Cold War US Prototypes

Moon ‘Tanks’ and Lunar Combat

USA (1958-1967) Concepts – None Built

Source: US Army Future Weapons Office

Following the defeat of Germany in 1945, the two former allies and ‘superpowers’, the United States and the Soviet Union, began a decades-long confrontation and global competition which became known as the Cold War.

The United States, assisted by its allies, such as Great Britain, had developed a functional nuclear weapon in 1945, and was followed by the Soviet Union in 1949 (post-war, the USA refused to share this technology with the UK, which developed its own nuclear device in 1952).

A year later, in 1950, the newly formed United Nations went to war in Korea with the Chinese and Soviet backed North Korean forces in a 3-year long conflict which could have escalated into the use of nuclear weapons.

It was clear to the US military that, whilst conventional forces may face off against each other, nuclear weapons may also come to dominate the battlefields of the 1960’s and beyond, and also that, in the larger geopolitical rivalry with the Soviet Union, any edge may be decisive.

When, at the end of July 1955, the United States announced its intention to launch artificial satellites into orbit around the Earth, the Soviets saw this as a challenge to their own security. They then began their own space program, culminating in the launch of Sputnik I and II in October-November 1957, the world’s first artificial satellite and the start of what became known as the Space Race. This was a race not just to show some technical superiority over a rival power, but also had the potential to yield dominance of a fourth realm of warfare – space.

Dominance of space would mean control over enemy surveillance satellites, the ability to spy on anyone, anywhere, and also to mount weapons beyond the ability of an enemy to counter strike, but also meant some kind of base would be needed.

This would be a base not in the form of a giant man-made space station orbiting the Earth, but on the greatest natural satellite – the Moon itself. This was made official as a request in early 1958, when the US Secretary of Defense, Neil McElroy, ordered the Advanced Research Projects Agency (ARPA) to take “a close look at the moon”. This was followed on 2nd April 1958 by President Eisenhower declaring the need for establishing a single unified national space agency (the National Aerospace and Space Administration – NASA, was formed on 1st October 1958).

“Last year (1958), Air Force General Homer A. Boushey,… stated that a lunar military base someday will be vital to national security, that in one sense the Moon represents the age-old military advantage of [‘high ground.’] He is one of the many uniformed American leaders seriously thinking in terms of the military relation of outer space to the Earth and human events thereon. While there is perhaps no unified agreement in American military circles on the concept that ‘he who controls the Moon controls the Earth,’ nevertheless, there is well-grounded agreement that vital military keys to our future national defense lie in outer space.”

LTC Robert B Rigg, US Army, 1959

The Project Horizon Moonbase dug into the lunar surface, ‘Late 1965’. Source: US Army

The Moon, Earth’s nearest neighbor, measures some 3,476 km in diameter (equatorial) and orbits the Earth at a distance of between 356,400 km (perigee) to 406,700 (apogee) at an average speed of 1,022 km/s. With a mass of 7.342 x 1022 kg, just 1.2% of the mass of the Earth, it has a surface gravity of just 1.62 m/s2, just 16.5% of Earth’s gravity. The Moon has no functional atmosphere. There are gases to be found on the surface, but the density of molecules is so low as to technically form an exosphere. Whilst minute levels of oxygen, amongst other gases, have been found, the quantities that are so minute as to be of little or no use – certainly not enough for a person to breath or vehicle engine to use.

No atmosphere also means no filtering of the solar and cosmic radiation, with charged particles being attracted to the exterior of any suit or vehicle as a result of the lunar surface being well insulated, building up a charge on anything moving across it. Men or vehicles returning to a base would have to be ‘earthed’ (grounded) to remove this charge – yet another problem to overcome.

If these conditions are not harsh enough, the temperatures range from -130° C to 120° C at the equator and are even colder at the poles. The temperature variation in a small locale can be severe too. The Moon moves around the Earth at just 0.5° per second, meaning not only that days and nights are two-week-long, but also that the area in daylight from the Sun lying next to an area shaded may only be a few centimeters away from each other, but could be over a hundred degrees different in temperature.

The surface is heavily pitted with craters from asteroid and meteorite impacts that struck the crust of the Moon over billions of years. Those impacts led to the surface being covered with a fine dusty material called regolith, which can range in depth from as little as 3 meters deep to around 20 meters deep in places with numerous rocky outcrops. The surface is a difficult and barren zone and any vehicles conducting operations, or any men on the surface, would have to be able to both navigate, survive, and even fight in these conditions – no small feat. Navigation both on foot or by vehicle is, for example, complicated by the fact that the magnetic field is too weak for an effective compass to work (less than 200 nT [nanotesla] compared to Earth’s 22,000 to 67,000 nT) and that a man 1.82 m (6’) tall can see only 2 miles (3.2 km) at best and more usually just 1.5 miles (2.4 km) and could easily become disoriented and lost. Further, the lack of an atmosphere means that radio signals can not be bounced down over the horizon, so radio communication is limited to line of sight only. With this high vacuum, metals in contact with each other can weld themselves together and yet lubrication is complicated by the lubricants boiling off. Any metals should therefore have to consider solid lubricants (which do not sublimate), special surface anti-friction coatings and/or only be in contact with non-metals.

Unusual conditions required unusual vehicles and Project Horizon certainly had its share of them and this would require some careful planning.

It has also to be borne in mind that in 1959, the exact surface conditions on the Moon were unknown to the extent that a plan in 1959 called for detonating a 500 kiloton nuclear weapon on the surface to analyze the material thrown up and the seismic effects resulting from the blast. Thankfully, the idea of nuking the Moon for science was not carried out and the first actual lunar samples would, in fact, not come back to Earth until 1969 and 1970 with Apollo 11 (USA) and Luna-16 (USSR) respectively.

The most probable site identified was the Sinus Aestruum (Latin: ‘Bay of Seething Heat’) near the Sinus Medii (Latin: ‘Middle Bay’) (center of the map to the right of the Copernicus crater). From a 1:5,000,000 scale labeled Mercator-projection relief map ‘Lunar Earthside Chart LMP-1’ October 1970 of the Moon 50 deg. N/S. & 100 deg. W/E. Source: Lunar and Planetary Institute via US Air Force Aeronautical Chart Information Centre


Planning for a base of operations on the Moon would start in the first half of 1959 without physical samples of the lunar surface, but with an idea of the conditions based on scientific observation instead. Work on the project began with a feasibility study (Phase I), followed by a detailed development plan including how much it would cost (Phase II) through the rest of 1959 and the first months of 1960. All of the necessary development of technology and hardware needed would begin in 1960 (Phase III) with 4 years of solid work up to the start of lunar base construction in mid-1964. Phase III was to continue through to 1967, with the lunar base construction (Phase IV) finished by the end of 1966 and online (Phase V) by the end of 1967. The final phase, Phase VI, would then follow as capabilities for operations were progressively improved and expanded. All told, it was estimated to take nearly 10 years to have this base fully operational and, by that time (end of 1967), the base would be housing nearly 300 personnel.

The planning for Project Horizon fell to Lt. General Arthur Trudeau, who, at the time, was the Chief of Research and Development. He ordered the Chief of Army Ordnance to draw up the details in a 90-day planning exercise. The experts for this project worked for an agency known as ABMA – the Army Ballistic Missile Agency, and were led by none other than Dr. Wernher von Braun (23/3/1912 – 16/6/1977). Just as Trudeau tasked the Chief of Army Ordnance, who tasked Dr. Braun, Dr. Braun passed the task to Heinz-Hermann Koelle (22/7/1925 – 20/2/2011) as project lead, who brought in Dr. Georg Heinrich Patrick Baron von Tiesenhausen (18/5/1914 – 4/6/2018). Tiesenhausen had been an employee in the German missile program at Peenemünde (from April 1943) during WW2, where he had been a Section Chief in charge of ground support equipment and designed Pruefstand XII for the exhaust deflection system for the Schwimmweste [Eng: ‘life vest’] project (submarine-launched V2 rockets for targeting the USA) and had worked alongside Koelle, Braun, and others. He had not, however, been brought to the USA until 1953. Subsequent to the end of the war in 1945 and prior to being gathered up as part of Operation Paperclip, the Latvian-born scientist had been running a tank collection park for the British and working at a ship winch fabricator. The Project Horizon work was also to bring in every conceivable specialist at some point to have their say or express their views on the potential task at hand. This was an enormous project, despite the very narrow window in which to do it – certainly more than a simple paper exercise in lateral thinking, but a serious discussion over the challenges ahead.

Dr. Wernher von Braun (left) and Heinz-Hermann Koelle (right).
Source: NASA via Air and Space Magazine
Dr. Georg H.P. Baron von Tiesenhausen, the brains behind the lunar mobility program for NASA. Source: Huntsville Times via the Tiesenhausen family.

Lt. Gen. Trudeau kicked off the planning work in March 1959 and, by 8th June that year, the report was done and published as ‘Project Horizon: A U.S. Army Study for the Establishment of a Lunar Military Outpost’ – a plan costing US$6 bn. to US$7.7 bn. For reference, US$$6 bn. and US$7.7 bn. in 1959 dollars would be the equivalent of US$53.4 bn. to US$68.8 bn. in 2020 values. Whilst this is a huge sum of money, it is still less than the current US defence budget for 2020, which is US$686 bn., and the costs were going to be spread over a decade. It accounted for just under 1% of the total budget, not to mention this would be money spent by the government within the US on rockets and salaries, etcetera. Maintenance of a lunar base was estimated in 1960 as an immodest US$631m per annum, equivalent to US$5.5 bn. in 2020 dollars – still under 1% of the US annual defense budget. The 1960 viability report by the US Air Force (also considering their own lunar base) on a permanent lunar military outpost pointed out that its total 10-year cost was equivalent to the annual operating costs of the US Farm Subsidy Program; in other words, it was expensive but affordable.

Lt. General Arthur Trudeau, US Army Chief of Research and Development 1958-1962. Source:

The Project Horizon report would be the outline for how a base could be set up as a critical lunar system, for which a later decision would be taken on exactly how to militarise it and what for. The ability to conduct observations from a fixed platform onto the Earth was obviously valuable, but a base would go further than that, as can be inferred from the ominously titled 1959 report on the base plans “Lunar Based Earth Bombardment System” which could, according to a 1960 report, deliver weapons to Earth with an accuracy of 2 to 5 nautical miles (3.7 to 9.3 km), clearly indicating that nuclear weapons were going to be the weapons of choice.

Getting men, machines, and equipment there, setting up a base, and then protecting it from a potential adversary meant creating a supply system and potential weapons systems. All of this had to be integrated together and work in synergy due to the distance from potential help or resupply. Thus, all of the problems of such an outpost have to be considered together to understand the decisions made.

Getting There

The task of bringing all of the tools, equipment, and men to the Moon was to take 229 flights over a four-year period using the Saturn I and Saturn II rockets. Just getting men into Earth orbit would take 16 flights of the Saturn I and 6 of the Saturn II, with an additional 47 and 71 flights respectively to get the cargo into space. As well as the 300 personnel to be ferried back and forth between the Earth and Moon, using a clever rotation schedule to establish a 12-man outpost, approximately 245 tons of equipment and building materials had to be delivered to the Moon. This does not include the sustaining cost of maintaining the base either. A total of 61 Saturn I and 88 Saturn II launches would be needed over a 28 month period (a rate of 5.3 per month) to get set up, with 64 more to supply the base in year 1 – more than 1 per week. Later, larger and more efficient rockets, including ones propelled by nuclear detonation (predicted to be available from about 1970) would reduce the logistic burden of supplying the base. Bases for launching the Project were planned for either Brazil or Christmas Island, as locations near the equator were desirable.

“to be second to the Soviet Union in establishing an outpost on the Moon would be disastrous to our nation’s prestige and in turn to our democratic philosophy.”

Project Horizon, June 1959

The Base

Buried into the lunar surface, the base would be partially protected from damage by solar radiation and falling meteoroids. It would be built from a series of tubes connected together in much the same manner as many nuclear shelters on Earth, forming functional modules in which work would be conducted. The primary difference would be the source of power, and for this, it was planned to use nuclear reactors to provide sufficient electrical power for all of the heating, lighting and equipment. An initial 5 kW nuclear reactor would be landed to provide power for the construction camp, followed by a 10 kW unit and a 40 kW nuclear unit for the construction of the rest of the facility. At that time, the 5 kW reactor would be dedicated to just powering the life-support. Lacking radiation shielding (to save weight), these would be placed into craters blasted out from the lunar surface if natural ones could not be found, and then covered with lunar soil to a depth of 12 feet (3.7 m). For normal operations, all power was to come from the 40 kW reactor, with the 10 kW unit held for emergency backup use. Despite the extreme cold in places, spare heat would still have to be released from the reactors and this was to be done with metal radiators fabricated from scrap, such as from cargo containers. Poking out above the surface, these radiators would dump the excess heat through thermal radiation, but also ensure a steady source of radiation on the surface, meaning men would have to stay away. At 50 feet (15.2 m) from the radiator, the dosage for a man within that zone would be 300 millirems per week. For reference, background radiation on Earth is around 100 millirem per year. Such a dose for the soldier within that distance would be just over 3 times the US Nuclear Regulatory Commission (NRC) sets as permissible for someone working around nuclear material. However, this was safe for the lunar surface, as the two plants would be located over 100 meters from the living quarters, about 30 meters apart. A final 60 kW nuclear power unit would also be added later, meaning no less than 4 different nuclear power units for the base to sustain life and conduct its military purposes.

The V-shaped arrangement of trenches containing the cylindrical housing modules is put together with the multi-purpose lunar construction vehicle. To the right of the image and just in the distance, can be seen the radiators for the nuclear reactors sticking out of the lunar surface. Source: Project Horizon Vol.II

Vehicles – Construction

One of the first vehicles to consider was a construction vehicle which could perform a variety of duties for the initial set-up phase of the outpost. Bearing in mind that gravity on the Moon was just 16.5% of Earth’s, this would, at first, appear to make life easier, as a 1,000 kg load on Earth would weigh just 165 kg on the Moon, but the low gravity created problems for the vehicles as well as the stability of them. On Earth, stability is based in large part on ‘normal’ gravity. With the mass distribution as it is, even if a regular bulldozer could be brought to the Moon, the weight distribution would be incorrect, making the vehicle unstable.

Vehicles would have to be weighted in order to maintain an effective power-to-traction ratio and that weight would not be brought from Earth – it would be added locally on the lunar surface. Much of the lunar vehicle work was to fall to Tiesenhausen and, as a matter of record, it should be noted that he became head of lunar mobility systems at NASA in 1963. Tiesenhausen is also primarily responsible for the lunar rover as it finally appeared as well several years later, but in terms of Project Horizon, there was primarily a concern for a vehicle for construction duties.

Weighing just 4,500 lbs. (2.04 tonnes) as its basic structure, additional mass the vehicle would need to become stable would simply be provided by means of ballasting it with lunar material, bringing its operational weight up to 9,000 lbs. (4.08 tonnes). Operating on four 4’ (1.22 m) open-spoke metal wheels, no tyres were to be used, but the speed would be low – just 1.5 mph up to 5 mph (2.4 to 8.0 km/h) so the cushioning of a rubber tire was not needed. The wheels would have diamond-shaped grousers to gain purchase on the lunar surface, and with a mass of 2,040 to 4,080 kg would, in effect, mean a weight of just 16.5% of that, making traction easier. Powered by a pair of 4 hp electric motors (rechargeable from the nuclear power-generated electricity supply from the outpost), the entire vehicle would be just 15’ (4.57 m) long, 6’ (1.83 m) wide, and 6’ (1.83 m) high and could be controlled directly through a pressurized cab where a man could work without a suit, or via radio (subject to the limits of radio range already discussed). On Earth, such a vehicle would require 20 to 25 hp per ton to operate off-road but, with the reduced gravity of the Moon, the electrical power units (8 hp total) were sufficient to meet the equivalent engine-power on the Moon and provide an operating range of 50-150 miles (81 to 241 km) although, as previously stated, anyone operating that far from a base would run a serious risk of becoming lost.

Lunar construction vehicle. Source: US Army

It was fitted with a variety of attachments, such as a U-shaped bulldozer blade, robotic arms, a crane boom, and a power take-off for a variety of other equipment which may be needed, such as an auger. This vehicle was calculated to be able to carry up to 480 cu. ft. (13.6 m3) per hour over 250 feet (76.2 m) with its 43 cu. ft. (1.2 m3) front bucket and to bulldoze up to 750 cu. ft. (21.2 m3) in the same time over the same distance. The crane would be able to lift 4,500 lbs. (2,042 kg) up to 2 feet (0.61 m) from the surface at up to 10 feet (3.0 m) from the vehicle. The vehicle would also be suitable to tow heavy loads, such as moving the habitation modules into the trenches dug for them, or supply sleds. Those would be made from leftover cargo containers which would be cut up to form rudimentary supply sleds and also to produce shielding for the habitation modules to protect from radiation and meteorite impacts. The towing capacity of the construction vehicle would be around just 50% of the total vehicle weight, just 2.04 tonnes at best.

Vehicles – Lunar Transport

To avoid the soldiers in suits having to walk around on the surface too much, a transport vehicle was going to be required. Consisting of a skeletonised frame made from light-weight metal, it was going to be compact – just 6’ (1.82 m), square, with the seat and controls exposed – avoiding the need for a cab, although a two-man cab could be used if required. A small load deck, in the manner of a miniature pickup truck, would be at the back. Also electrically powered, this 3-axle vehicle would weigh just 2,000 lbs. (907 kg), and be able to move a load of men and equipment between 50% and 300% of its own weight, depending on the nature of the surface.

Each axle would have a wheel at each end and each would have its own 1 hp electric motor for a total tractive power of 6 hp. Suitable batteries would provide a range of 50 miles (80 km) or 10 hours of operation before needing to be recharged. Interestingly, the prospective design for this vehicle is missing from the available copies of Project Horizon.

A foreign analysis of other types of lunar vehicles was published for the US Air Force in 1967 from an original document by D. St. Andreescu of Romania. Andreescu was a Major General and a member of the Commission on Aeronautics in Romania and the article the US Air Force translated in 1967 was first published in 1963. Andreescu’s work had involved looking at conflict and exploration in space at least as early as 1957, so it is no surprise that his work would garner attention from the US.

Rocket-type lunar lander from the front page of Andreescu’s 1963 article. Source: Andreescu

The Foreign Technology Division (the US Air Force Branch responsible for identifying and analyzing foreign technical material) investigated what ‘the other side’ was looking at in terms of potential lunar vehicles. Originally titled ‘Vehicule Lunare’ [English: Lunar Vehicles] in the original Romanian article by Andreescu, the report considered that a Moon-based command post was, just like the USA had concluded, a logical step in the steady conquest and use of space. Andreescu considered a few different types of vehicles and types of power systems for lunar propulsion, including tracks, wheels, a large rolling spherical body, helicoidal screws, rockets, electric motors, walking machines, flying machines, and even leaping or ‘bounding’ vehicles. In doing so, he appears to have been drawing upon ideas or designs which predated this 1963 work, although it is unclear where he got them from. They may have been his own ideas from before or a collection of ideas from a variety of international sources – it just is not known as he provided no references. There are, however, two vehicles of particular interest from Andreescu. One, a giant tracked ball virtually identical to the vehicle shown in the Project Horizons plan, and a small tracked luna mobile. Whilst the former vehicle does appear in the Project Horizon report, the second does not – it only appears in a 1967 US Air Force translation of his paper. Of the multiple vehicles Andreescu discussed, therefore, it is those two which are of the most interest in terms of Project Horizons.

Spheres and Tracks

The ‘tank-like’ vehicle ran on wide tracks supported by four large road wheels and a drive or jockey wheel at either end. It is not clear which end the power was supplied to the tracks, as it is not shown in the available image of the vehicle. No supporting rollers are shown. The track is, however, covered across the top by a large dust shield to prevent clouds of regolith being thrown up as it moves. The body of the vehicle is flat-sided, with a shallow sloping front surface, which on a tank would be the ‘glacis’. The rear is more sharply angled. On top of the vehicle is shown what appears to be an exhaust stack for venting gas and/or heat, much like a ship’s funnel over the back end, with a large dome with multiple large rectangular windows at the front of the roof. Inside are shown a trio of astronauts.

Completing the vehicle are a pair of headlamps at the front, a flapped-horizontal slot and a circular feature (perhaps a light) on the ‘glacis’. Projecting from the front, just below those headlamps, are a pair of supporting arms for what appears to be a bulldozer blade.

It would be powered by electric motors running on compressed (pressurized) hydrogen provided by a turbogenerator and recharged by use of nuclear power generators. This power supply would propel the vehicle on the lunar surface at up to 40 km/h for 24 hours of continuous use between recharges. The heat irradiated from the passengers on-board would boil off the hydrogen fuel source and this heat was then recaptured by a lithium hydride recuperator. This power supply would weigh just 1,200 kg – more than 200 kg less than an equivalent diesel engine and without the problems of liquid fuels in a lunar environment.

With a crew of three in the bubble on top, this 1.2-ton lunar vehicle uses the heat from the humans as part of the propulsion system. This image is identical to the one featured in the 1967 US Air Force translation but does not appear in the 1958 Project Horizon plan. Source: Andreescu
Note: surrounding text from image has been digitally removed for the sake of clarity but the vehicle image has not been altered.

If the tracked lunamobile is rather mundane as a tracked vehicle, albeit one for the Moon, then it is the spherical vehicle idea from Andreescu which is perhaps the most curious. This was a vehicle with a spherical hull and held upright by means of “hydroscopic” (gyroscopic) stabilisation, ensuring the 3 or 4 men inside would stay correctly orientated in relation to the lunar surface. Running on a single circumferential track, the spherical lunamobile was thought to be useful for exploring the surface due to its shape, which would prevent it from becoming stuck in a crater. A second track ran circumferentially around the vehicle in the horizontal plane, meaning that, even if the vehicle toppled over to one side, it could move by being driven by both tracks either out of the obstruction or until the gyroscopes righted the vehicle.

Power was supplied by a large circular solar cell acting like a parasol above the vehicle, which could be angled to receive maximum solar radiation, although no other details are provided.

A gyroscopically-stabilised tracked ball vehicle with overlapping circumferential track, this highly impractical vehicle was pictured in some form to be useful for exploring the surface. This image is identical to the one featured in the 1967 US Air Force translation and also appears in the 1958 Project Horizon plan. Source: Andreescu

The curious matter about this vehicle, described in General Andreescu’s report from 1963, is that this vehicle features at all. It is, in fact, identical to the spherical lunar vehicle seen in Volume III of the Top Secret Project Horizons plan, a plan which was still secret through this time. Looking at the two views of this vehicle in these two reports, it is hard not to see that one party must have known about the other and, as Horizon was 4 years before Andreescu’s report, it would seem at first glance that Andreescu took inspiration from it for that image. The Project Horizon work was, for decades, Top Secret, so it is highly unlikely he could have seen the tracked spherical lunamobile. Instead, the logical conclusion is that the spherical tracked vehicle predated the Project Horizon in some non-classified form from which ABMA and, in due course, Andreescu, drew inspiration. Whether this was something serious or some science-fiction writing is not known at this point. Certainly, if ABM was copying from some preexisting idea from Andreescu, then the tracked and rather practical lunamobile could reasonably have been expected to have featured in Project Horizon.

The spherical lunar vehicle as pictured in the 1959 Project Horizon (left), and the 1963 Andreescu Romanian report (right). The similarities between the two (other than the horizontal track running in the other direction) are undeniable. Source: US Army and Andreescu (via US Air Force) respectively.

The use of the spherical exploration machine in the Project Horizon plan comes up during discussion of combat too, so it is fair to say that where concepts of combat on a lunar surface are concerned- they would, in the eyes of the planners, inevitably involve vehicles and probably tracked ones at that.


With a very credible Soviet space program and the sense of a race to the Moon, it was part of the planning activities of the program that there was a potential for the base to be attacked by the Soviets. It would, afterall, be a base for nuclear weapons and needed guarding. In considering combat on the lunar surface, the environmental considerations of temperature, pressure (or rather, the lack of pressure), and the low gravity made for a complex combat situation.

“…sole possession of a lunar outpost… would provide a military advantage in case of terrestrial hostilities. Defense must be provided to deter attack to obtain such an advantage”

Project Horizons Vol.I

Development of various elements of equipment to meet the needs of defending the men and equipment on the outpost was going to be divested to the various expert technical agencies. For example, nuclear weapons systems would be left to the Atomic Weapons Laboratories at Picatinny Arsenal, electronic systems would be in the hands of Diamond Ordnance Fuze Laboratory (DOFL), and missile/rocket design would go to the US Army Ordnance Missile Command (AOMC). On the surface of the Moon, vehicles were going to be needed to move around, build facilities, and provide security and these were to be left in the hands of the Ordnance Tank-Automotive Command in Detroit with responsibility for “developing and testing both combat and transport vehicles to meet special requirements”.

“If the moon and other planets are explored and possibly colonized, the world could eventually see a second evolution of weaponry and protection therefrom. Visualise starting with a weapon capable of penetrating thin skinned vehicles. The vehicles then get thicker skin. The weapons then attain a greater penetrating capability. The vehicles get even thicker skin until the weight and cost thereof becomes insurmountable. The weapons attain longer ranges etc., etc., etc.,. This proceeds through the mortar, howitzer, gun and tank stages until eventually you have missiles, antimissiles and nuclear weapons…..”

US Army Directorate of Research and Development, 1965.

Just as the comment above related to ‘tanks’, it was part of Project Horizon’s initial assessment that the use of vehicles in a potential attack or defense at the outpost was a credible concern. Although they could not carry armor in the sense of a conventional tank due to the difficulties in getting such a vehicle to the Moon, it was certainly conceivable such vehicles may have some ballistic protection beyond just retaining a pressurized atmosphere within the vehicle. Thus, any weapons planned for the outpost should also have had an anti-materiel ability to perforate a vehicle and depressurize it or cripple the automotive parts.

Such a unique combat environment precluded the use of conventional ammunition and weapons like rifles. This is not, as may be thought because the ammunition would not work in an oxygen-free atmosphere. It would work (albeit with some known problems with primer activation in a vacuum) – modern ammunition has its own oxidizer self-contained, so a rifle would indeed work. In fact, the lack of moisture and oxygen actually helps to preserve plastic explosives and prevent corrosion infuses, etcetera, although non-plastic explosives like TNT would degrade with the temperature extremes. Such conventional firearms were, however, designed to fire in Earth-gravity situations, so the sights would be almost useless on the Moon. Add to this that the reduced gravity on the Moon would seriously affect the trajectory of any bullet fired on the surface and that other features of a conventional rifle, like a stock, were not required because a man in a suit would not be able to carry the weapon easily in such a way and what is left is the need for a bespoke weapon – albeit it one which might use conventional-types of ammunition. However, that too involved a lot of weight-wastage through a casing. Newton’s Third Law of Motion states that for every action there is an equal and opposite reaction. In other words – recoil, and this recoil would be harder to manage for the soldier in a low gravity environment. With no effective atmosphere either, any missile fired would not be subject to drag from friction, like it would on Earth, and would increase the range of a projectile by some 6 times or more. The same was also true of the explosive out-gassing behind a recoilless weapon, making them extremely hazardous to friendly vehicles, buildings, or personnel behind. The same applied to explosively producing fragments/debris, as it would travel further and faster than on Earth. Given that penetration is a function of the square of the velocity of the projectile, even bits of regolith kicked up by a blast created an enormous hazard for men and machines.

The effect on-target of the projectile or directed energy device differed substantially from terrestrial combat too, as substantial damage could be done to a target simply by exposing it to the vacuum of space, piercing the suit or vehicle skin.

An attack on the outpost from the Soviets could not come without warning. Either the launch would be detected or the launched-craft picked up by Earth-based monitoring. If a craft could be landed secretly, the outpost would also have a short-range radar set with a range of up to 2 miles (3.2 km) and backed up by an active infra-red system with a range of 400 – 500 yards (366 – 457 m) range.

Planning assumption for outpost defense related to a roughly platoon-sized attacking force, but defense had to consider combat in 4 situations:

  1. Space-suited personal combat
  2. Lunar surface vehicle combat
  3. Moon-orbiting space vehicles
  4. Non-orbiting space vehicles

Project Horizon considered various modes of killing or incapacitating an enemy force approaching the perimeter of the outpost (scenarios 1 and 2 above). This perimeter defense had to be able to provide adequate means of killing both suited men and also vehicles and should be fireable directly or remotely. Options for such a weapon were considered and evaluated for both performances but also whether they were technically feasible.

These included

  1. Beamed electromagnetic radiation
  2. Flamethrower
  3. Blast weapons
  4. Fragmentation weapons
  5. Radiant energy

Defending against orbiting craft was more complex than a surface defense and, whilst an orbiting enemy could be tracked using Hercules, Zeus, or Hawk radar, it would be difficult to engage as available surface to air (or in this case surface to orbit) missiles were well beyond the 1,000 lb. (454 kg) weight limit imposed and a new bespoke weapon was needed. This would be expensive and with a long development time. An electron accelerator-based weapon was considered and would work by directing beams of gamma and/or neutron radiation at a craft to kill the crew and damage the craft. Just like the missile idea, however, this was far too heavy, 6,000 lbs. (2,722 kg) on Earth for such a system and still over 1,000 lbs. (454 kg) equivalent for a lunar-based system. In conclusion, Project Horizon rationalized that no effective defense could be provided against an orbiting enemy vehicle and the men on the outpost could, at best, dig into the surface to obtain protection until a suitable missile defense system became light enough to install there.

Personal Combat

With a set of unique problems from the environment (lack of atmosphere and exposure to solar radiation), equally unique weapons would be needed for troops to use if combat was to take place between US soldiers and a (presumably Soviet) force landing there.

Spacesuits would have to include an element of armor protection, along with the ability to self-seal following perforation, as a simple weapon that made even a small hole in a suit could prove lethal. More holes meant a greater chance of killing the opponent with the environment rather than the terrestrial method of killing the opponent by means of trauma. Weapons that optimized the delivery of high-velocity fragments were therefore considered the most desirable.

May 1959 design for a ‘Lunar Clothing System’. It owes more to Buck Rogers than a practical suit. The ice-skate-looking devices on the boots are soles to help stop the astronaut from sinking and presumably he would want some gloves too, although these are not shown in the drawing. Source: US Army

The suit proposed by Project Horizon included a hard suit for the body, made from titanium approximately 4 mm thick for standard protection and up to nearly 10 mm thick for maximum protection covering the stomach and chest, with a composite inner layer for resisting radiation. The same would go for a vehicle, with a titanium metal structure of approximately the same thickness to provide some resistance to fragments and also to maintain pressurization. Later, in analyzing how much protection 3.70 – 9.25 mm of titanium could actually provide on the lunar surface, it was calculated that a simple 6 grain (0.38 gram) fragment at 3,800 ft/s (1,158 m/s) or a 17 grain (1.10 gram) fragment at 2,400 ft/s (732 m/s) could pierce the suit or vehicle.

In terms of personal firepower, Project Horizon considered the various options and limitations which had to be considered, such as having to be self-sustaining.

The assessment was clear that the best weapon for defeating an enemy force either suited on-foot or in a vehicle of any description would be a Claymore-type mine. The standard Army type coming into service was the T48E1 mine, weighing just 1.36 kg and containing 675 5.56 mm diameter steel balls in a plastic resin. Once detonated, these balls, which were arranged in a slightly concave shape, would be fired out at a speed of 3,700 to 3,900 fps (1,128 to 1,189 m/s) across a 60-degree arc. On Earth, the mine’s effective lethal radius was around 200 feet (61 m), but on the Moon, with no atmosphere to slow down the balls and low gravity, the effective lethal range was increased to 2,500 feet (762 m), although the spread of the balls at that range would be extreme.

The Claymores could be set as a perimeter defense to be triggered upon command or by a tripwire, but they could also be handheld. This was not as hazardous as it may sound as, due to the vacuum of space, there was no blast hazard to the man detonating it on the end of a pole 5 to 6 feet (1.52 to 1.83 m) long. With a suitable shield surrounding the back of the mine to prevent mine fragments from being fired at the soldier wielding this weapon, in total, it was under 1 kg in weight. This made it simple, cheap, and easy to use for all combat purposes against men or machines.

T48E1 Claymore Antipersonnel mine. Source: US Army
Claymore mine detonated to kill approaching enemy forces on the lunar surface. Note the presence of the tracked spherical lunamobile in the image. Source: US Army.
Handheld claymore-type directional fragment weapon. This odd-looking device was ideal for use against men and vehicles on the lunar surface. Source: US Army
Artist’s impression of the handheld claymore device in use by a US Soldier against an unidentified adversarial force on the lunar surface. Source: US Army.

Whilst the attack scenarios involving orbiting were complex, the judicious use of detonating a nuclear weapon nearby was possible. Detonating a 10MT nuclear device in space, launched from the outpost for protection would, for example, have a lethal radius of around 320 km, although it did mean having to station nuclear weapons there and obviously accepting the risk of killing yourself with your own weapon’s radiation (unlike a detonation in Earth’s atmosphere, a nuclear blast in a vacuum primarily produces intense radiation rather than blast or thermal energy release). Even should the outpost detonate a weapon in lunar orbit to defend against an attacking craft, the lack of atmosphere on the surface meant that there would be no attenuation of the intense radiation, creating a hazard for the outpost.

Proximity to the blast was one of the notable flaws of the Army’s new M-28 ‘Davy Crockett’ nuclear weapon system. Often referred to as a recoilless rifle system, the M-28 was, in fact, a type of spigot mortar (120 mm) that could throw the 23 kg Mk.54 nuclear warhead weighing around 2 km. With a yield of 0.01 to 0.03 kT of TNT, the warhead on Earth would cause severe damage over a 10 m radius and moderate blast damage out to around 500 m (surface detonation), and up to a kilometer as an airburst. On the Moon, with no atmosphere to attenuate the explosion, damage could spread a lot further but so could the potential range of the warhead.

The Davy Crockett, fired at a maximum angle of 45 degrees, could, from the Moon, reach a lunar altitude of just over 1,200 m – high enough to be a threat to a descending enemy craft but not high enough to engage an orbital target and both with serious personal safety issues.

M-28 ‘Davy Crockett’ Short Range Spigot system. Source: US Army
The variation in terrestrial and lunar trajectories for the M-28 ‘Davy Crockett’ are shown starkly in this graph where the range on Earth is just 1,800 m compared to on the Moon at 15,500 m.
Source: US Army

An alternative to the M-28 was also considered, one which was more accurate, lighter, and simpler, but with a shorter range. This was the Dumbo II, which was still on the drawing board and consisted of little more than a launching tray on legs with a rocket-propelled bomb loaded into it. On the lunar surface, this device would have a range of just 4,400 yards (just over 4,000 m) with an accuracy of 40 yards (37 m). It was, in the understatement of the decade, “desirable” to increase the range. With a range improvement to 17,700 yards (just over 16,000 m), it would increase the weight from 130 lbs. (59 kg) to 160 lbs. (72.6 kg).

Dumbo II short-range nuclear weapon system. Source: US Army

In 1965, this subject of lunar personal weapons was examined once more by the US Army in the unusual title report “The Meanderings of a Weapon Oriented Mind When Applied in a Vacuum such as on the Moon”.

The cover-art of the June 1965 Army report features a weapon carrying vehicle on multiple legs with two space-suit clad soldiers. One is showing off with a pair of weapons in use at the same time followed by the less well armed soldier behind. Such artwork on an Army report was no doubt very exciting to see, but did not add a great deal of technical credibility to the reader and is more in keeping with science fiction rather than the plausibility of lunar combat. By the time of the report, all matter of lunar exploration had been handed over by the Army to NASA. Source: US Army

With the problems of cold welding over close-fitting and non-low friction metal parts, no lubricants, the temperature extremes in which it would have to operate and the issue of recoil from conventional-type weapons, solutions to a projectile weapon were perhaps harder to overcome in some regards than for a vehicle. The laser (‘Light Amplification by Stimulated Emissions of Radiation’), a concept of creating a focussed and intense beam of light, had been theorized for some time but did not exist before May 1960, when Theodore Maiman made the first laser (a ruby-laser) at the Hughes Research Laboratory in California. To theorize a laser weapon was beyond the ability of engineering in 1965 when the paper was written. It was not until 1967, with Co2 lasers of over 1,000 watts, that the first lasers were powerful enough to cut through even a sheet of steel 1 mm thick (TWI- The Welding Institute Cambridge, England), and the US Army paper actually suggested a lead time of at least 20 years. Although proposed in 1965, therefore, as a solution, laser-based systems were just pie in the sky, leaving recoilless weapons or very-low recoil weapons as the next best probable alternative.

Projectiles considered were rockets of various descriptions, balls (spheres), flechettes, and even rocks, which, based on the low gravity environment, would travel 2.73 times further than on Earth. For example, fired from the shoulder of a 6’ (1.8 m) tall man 5’ (1.5 m) from the ground at 3,000 f/s (914 m/s), a projectile would go 8,190 feet (2,500 m) when fired horizontally. Rather hazardously, however, was that due to the lack of atmosphere, if the projectile were fired upwards above the horizontal plane, it could go enormous distances. At 45 degrees, for example, a projectile launched at 3,000 f/s (914 m/s) (well short of the escape velocity of 2,400 m/s), would travel 320 miles (515 km), having reached an altitude of 80 miles (129 km) above the lunar surface.

The lack of ‘drop’ on the round added the severe hazard of projectiles in flight for large distances and long periods of time but had one significant advantage – the lack of anything other than the most rudimentary of sights being required. This is because a projectile would drop just 60 mm or so for every 100 m. Given a maximum line of sight engagement range of maybe 1.5 km, a projectile would, at worse, drop just 90 cm.

The lack of atmosphere also meant that wind resistance was effectively zero, so the shape of the projectile did not matter in terms of an efficient ballistic shape. Although ‘armor’ was not probable, it was objectively going to be easier for a spacesuit to resist perforation by a blunt object than a pointed one. Considering that vehicles were also a possibility, a pointed projectile with a high sectional density was preferred to aid in perforating the skin on those as well. The report concluded with a series of prospective weapon types summarised below. Noteworthy is that none of them are as expensive or perhaps simple and dangerous to men and vehicles as the Claymore-on-a-stick proposed in Project Horizon.


Exo-activity on the lunar surface (or even in space, as a ‘space-walk’) had not been done in 1959, so some of the suit-ideas and the science of space-suits were not fully developed by the time. There were, however, clear goals for a practical suit and the advantage of the low gravity meant that a 300-pound (136 kg) spacesuit would weigh just 50 pounds (22.7 kg) equivalent on the lunar surface.

Nonetheless, wearing a suit is a tiring task and normal wear would be limited to just 8 continuous hours, although 12 hours was acceptable. With a degree of caution, a man may operate in his suit for up to 24 hours and, in a dire emergency, 72 hours.

Referred to as a “metallic body conformation suit”, the outer surface was to be shiny (like all good 1950’s sci-fi) in order to reflect heat, but tough enough to resist the impact of micro-meteorites.

Any combat taking place in such a suit would be awkward and obvious to any attacker.


In 1959, there was a serious lack of crucial data on which to make some decisions – such as where to even put the base. Earth-based observations of the Moon could show the ‘seas’ – large flattish areas with few impacts, but the best available map being made by the Army Map Service at the time was just 1:5,000,000 scale and the contours were 2,000 feet (610 m) apart, meaning what looked flat could actually be quite a steep slope and landing on a cliff was ill-advised. An improved version of the map, due in around 1960 using better methods of stereo-image analysis, would be 1:1,000,000 scale with contours just 300 meters apart, with the aim of getting accuracy on surface features down to 150 or even 100 m by 1962. It is obvious, therefore, that with so little known, any outpost might find itself on impossible terrain. Any such landing without a better idea of the terrain was impossible in practical terms.

This was a fundamental part of the death knell for such ideas. It had not been the costs that killed Project Horizons perhaps as much as politics and practicality. It was not seen as being unfeasible or even unaffordable but perhaps just not necessary. The idea of launching at least one new Saturn rocket a week for years on end was one thing the Army could live with, but with the formation of NASA in October 1958, the writing was on the wall for the Army. NASA would take over all of the space work from the Army and Project Horizon, in particular, was handed over to their control by General John Medaris in March 1960. NASA had no interest in this project and it was thus left to die. The rest of the Army’s role in space was also handed over by the first half of that decade and the Army regained its terrestrial focus.

No weapons base on the Moon meant no need for weapons against men and machines, no lunar combat, and no ‘Moon-tanks’.

In 1967, with the signing through the United Nations of the Outer Space Treaty (OST), all signatories (including the USA and the Soviet Union) agreed not to place nuclear weapons in space (Article IV) either in orbit or on a celestial body (like the Moon), and that the Moon, in particular, was to be used exclusively for peaceful purposes. It also prohibits the establishment of military bases, installations, and fortifications on the Moon (Article IV), although military facilities for peaceful purposes were not prohibited. The treaty did not end ideas for a Moonbase, like Project ARES in the 1990s, but it did preclude space-based nuclear weapons. A further treaty, known as the Agreement Governing the Activities of States on the Moon and Other Celestial Bodies (‘The Moon Treaty’) signed in 1979 and effective from 1984, added to the Outer Space Treaty by prohibiting the creation of military bases although neither the United States nor the Soviet Union (or now Russia) have ratified that treaty.

Article IV
State Parties to the Treaty undertake not to place in orbit around the Earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, install such weapons on celestial bodies, or station such weapons in outer space in any other manner.

The Moon and other celestial bodies shall be used by all State Parties to the Treaty exclusively for peaceful purposes. The establishment of military bases, installations, and fortifications, the testing of any type of weapons, and the conduct of military maneuvers on celestial bodies shall be forbidden. The use of military personnel for scientific research or for any other peaceful purposes shall not be prohibited. The use of any equipment or facility necessary for peaceful exploration of the Moon and other celestial bodies shall also not be prohibited.

United Nations Office for Disarmament Affairs: Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies 1967. Underlining added by the author. Full text at

No national sovereignty rules in outer space. Those who venture there go as envoys of the entire human race. Their quest, therefore, must be for all mankind. And what they find should belong to all mankind.
President Lyndon Johnson in ‘The President’s News Conference
at the LBJ Ranch (29th August 1965).
Collected in Public Papers of the
Presidents of the United States:
Lyndon B. Johnson: 1965 II (1966), 944-945.

Project Horizon was, perhaps, more of an embarrassment just a few years after it had been completed. The new NASA-controlled program was not interested in nuclear weapons on the Moon and the Defense Department fought to prevent its release to the public. In a 3 year struggle (1959-1962), the project was subject to numerous requests for release and, after no less than 10 separate security reviews by 3 different intelligence agencies, it was finally revealed at the end of the year. The project was effectively obsolete before it had even been finished, regardless of future changes, but it can be said that the project did form an important mental step in the long process of getting men to the Moon and, for Tiesenhausen – for what would eventually convey astronauts on the lunar surface with the Apollo 15 mission in July 1971.

Tiesenhausen’s work finally reached its fruition in the form of the lunar rover (Lunar Roving Vehicle – LRV) on the Apollo 15 mission. It took the simple option of tires over tracks. Source: NASA

A small 1.2-ton construction vehicle meant for the lunar surface. It would have been useful not only for constructing the base but also for constructing defensive positions. Illustration by Pavel ‘Carpaticus’ Alexe, funded by our Patreon campaign.


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Cold War US Prototypes

120mm Gun Tank T43

U.S.A. (1951)
Heavy Tank – 6 Prototypes Built

On September 7th, 1945, military heads of the Western Powers were horrified by what they saw rumbling towards them along Charlottenburger Chaussee in central Berlin during the Victory Parade. Celebrating the end of the Second World War, the increasingly threatening Soviet Union unveiled its latest tank to the world: the IS-3 heavy tank. As these machines clattered down the parade route, a sense of consternation enveloped the representatives of the British, US, and French armies. What they saw was a tank with well-sloped and apparently heavy armor, a piked nose, wide tracks, and a gun at least 120 mm in caliber, and belonging to a future potential adversary. The IS-3 was clearly a serious potential threat to their own tank forces in any such conflict.

The race was on. France, Britain, and the US immediately began to design and develop their own heavy or heavily armed tanks. The British would eventually create the Conqueror Heavy Gun Tank, while the French experimented with the AMX-50. Both of these tanks had 120 mm guns that would, in theory, be able to combat the IS-3 threat. Two branches of the US Armed Forces would support the creation of a new American heavy tank. These branches were the US Army and the Marine Corps. Realising that the heavy tanks conceived during WW2, such as the T29, T30, and T34, were unfeasible, both branches set out to develop a new heavy tank that would eventually be known as the 120 mm Gun Tank M103.

Although the need for a heavy tank was urgent to fight the perceived IS-3 threat, it would take until 1948 before the development of the T43 heavy tank would actually start because of various issues, including budget and disarmament. Both the Marine Corps and Army were interested in the future heavy tank, but when various forces within the US Army started opposing the T43, it was the Marine Corps that would eventually give the leverage needed for full production. The first 6 of these vehicles were pilot vehicles which would lay the foundations for the M103 heavy tank, the only heavy tank to be used in active service of the United States.

The T43 Pilot #1, Aberdeen Proving Ground July 7 1951.
Source: Firepower, Hunnicutt


The T43 (M103) was a project of the US Army with the goal of developing a heavy tank capable of defeating enemy heavy tanks at combat ranges and deliver heavy fire-support for both infantrymen and medium tank battalions in offensive and defensive roles. It was to be superior to the previously developed T34 heavy tank, specifically in mobility, flexibility, and component availability. The USMC had an interest in the project because of their amphibious warfare doctrine. Initially, the Army would be the lead branch supporting the development of the M103 (then known as T43), but as development dragged on, the Army would lose interest. The Marine Corps would be the driving force behind the upgrade programs to fix some of the larger mistakes the tank had, which the Army did not do. Although the goals of the two branches were mostly the same, their reasons and experiences that led to the development of the T43 and its eventual service as the M103 were quite different.

The Army

Brigadier General Gladeon M. Barnes
Source: United States Army

The story of the Army part of the development begins in 1944 with Brigadier General Gladeon M. Barnes. Barnes was the head of the US Army’s Ordnance Technical Division (OTD) during the Second World War. In short, he was the head of development and acquisition of weapon systems for the US Army, including tanks and armored vehicles. Throughout the war, he had advocated for heavier tanks and tank guns, but had met stiff opposition from Army Ground Forces (AGF) under Lesley McNair.

When the Allies had to face off against the Tiger II and increasing numbers of Panthers in 1944, of which the latter was originally perceived as a heavy tank instead of a Panzer IV replacement, Barnes would receive much less opposition against his heavy tank programs. Those projects took form as the T29 and T30 heavy tanks and would eventually serve as testbeds for many components used in later US tanks. The AGF objected to the T30’s heavy ammunition and requested for the rearmament of the T29 platform, designated T34, which was to be armed with a converted 120 mm anti-air cannon. The T29, T30, and especially the T34, with its 120 mm gun, would pave the way for the M103.

T34 Heavy Tank
Source: War Thunder Forum

With the end of WW2, the development and production of the aforementioned heavy tanks would come to a halt, as there was no need for them anymore. But then, on September 7th, 1945, the need for a heavy tank would be renewed as the last armored column of the 1945 military victory parade in Berlin drove past the military heads of the Western powers. A new challenger had made its way on the stage: the IS-3 had arrived.

As early as January 1945, the Army had started conducting an equipment requirements study for a post-war situation. In June 1945, this study would be finished and recommended the adoption of a new generation of light (25 US tons / 22.7 tonnes), medium (45 US tons / 40.8 tonnes) and heavy tanks (75 US tons / 68 tonnes), and a prototype 150 US ton (136 tonnes) super-heavy tank. It also gave the following specifications of the recommended heavy tank: a five-man crew, a sustained maximum speed of 20 miles per hour (32 km/h) on a 7-degree slope, fording ability of at least equal to the tank’s height, interestingly, a main gun not larger than 90 mm capable of penetrating 10 inches (254 mm) of armor at a 30-degree vertical slope from a distance of 2,000 yards (1,830 m) with special ammunition, accurate fire at a range of 4,000 yards (3,660 m) with a dispersion limit of 0.3 mils (a dispersion of 1.08 inch per 100 yards or 3 cm per 100 meters) and the frontal hull and turret should have an effective armor of 10.5 inches (267 mm). In January 1946, the Army declared its entire tank force, with the exception of the M4A3E8(76)W Shermans and M26 Pershing, obsolete (the Pershing was later reclassified as a medium tank in May 1946).

During the same month, another requirements study, done by the Department of War, was finished. This requirements study also recommended the adoption of new light, medium and heavy tanks which would eventually receive the designations T41, T42, and T43 respectively, while dropping the super-heavy tank and laying emphasis on developing components to be used specifically for tanks.

The Marine Corps

Major General Oliver P. Smith (left) and Lieutenant Colonel Arthur J. Stuart (Right)
Sources: M103 Heavy Tank, Kenneth Estes and USMC

The story of the Marine Corps part of this development begins in September 1944 at the beaches of Peleliu. There, the Marines landed with armored support, consisting of 30 Sherman tanks. They were met by well dug-in enemy forces, artillery, and mortar fire. The Japanese responded to the invasion by launching a counter-attack with 17 tanks supported by infantry. The Marines were caught by surprise and the Shermans still had to get into position. The light Japanese vehicles were destroyed by bazookas, Shermans, and various other anti-tank weapons during the counter-attack.

Two key players, who were going to have a profound influence on the acquisition of a heavy tank for the Marine Corps and were essential to the development of the M103, bore witness to the Japanese tank-infantry counter-attack. These were Lieutenant Colonel Arthur J. Stuart, who commanded the 1st Tank Battalion at Peleliu, and Major General Oliver P. Smith, who was a ground commander during the battle. These men ensured that the Marine Corps got its heavy tank, with Lt. Col. Stuart being one of the most important advocates of integrating tanks in Marine Corps doctrine during the early post-war situation.

On March 22nd, 1946, now Brigadier General and Commandant of the Marine Corps Schools, Oliver P. Smith wrote to the Commandant of the Marine Corps Alexander A. Vandegrift the following:

‘’In general, the tanks with which the Marine Divisions ended the war are now definitely obsolete. The tank for the future must be capable of withstanding greater punishment, be more mobile, and have improved hitting power. The present tanks are too slow and too vulnerable to anti-tank weapons.’’

This conclusion was based upon the experience of Lt. Col. Stuart who remarked:

‘’Had the Japanese possessed modern tanks instead of tankettes and had they attacked in greater numbers the situation would have been critical.’’

General Alexander Vandegrift responded by purchasing M26 Pershings as substitute heavy tanks and waiting until the Army developed new tanks that the Marine Corps could adopt. Whereas the Marines fought Japanese light tanks during the War in the Pacific, they potentially had to face significantly more powerful and more heavily armored Soviet medium and heavy tanks during the Cold War.

M26 Pershing in Korea.

The reason for the Marines desire for a heavy tank came from their doctrine of amphibious warfare, developed in 1935, which had called for the deployment of tanks during a beach assault. This doctrine consisted of 2 phases of amphibious assault, of which the first phase, the initial landing phase, was to be supported by a light landing tank for infantry support and clearing beach defenses. The second phase was to be supported by a medium tank to carry the battle inland, destroy heavier positions and repel any armored counter-attack. During WW2, the first phase was to be carried out by the M3 Stuart and the second phase by the M4 Sherman. The Stuarts proved to be ineffective at Tarawa in late 1943 and their role was taken over by the M4 Sherman, now carrying out both the first and second phase of the assault. Naturally, the second phase should now be carried out by heavy tank battalions in the post-war scenario.

The T34 needs to lose weight

Although the need for more capable tanks for the post-war situation was clear, the actual start of developing the T43 began as late as 1948. The lack of budget and direction caused the Army to invest in developing components instead of tanks. By testing components used in existing tanks, such as the T29 and T34, the Army developed a whole range of tested components that could be combined into a new tank. Components like the Continental AV-1790 engine and CD-850 transmission can be found throughout the Patton series and the M103 as well. This development approach, although the best solution for the US Army’s low budget long-term tank development, would plague the future tanks with underpowered engines and rushed development.

Development of the T43 began with the rejection of the most promising heavy tank prototype the Americans had at the time, the T34. The 70-US ton (54.4 tonnes) heavy tank was rejected because of its weight, which led to poor mobility and maneuverability characteristics, which could not meet the post-war requirements of both the Army and the Marine Corps. The rejection of the T34, combined with a deteriorating world situation, caused the Army to start undertaking the development of the later designated T41, T42, and T43 tanks that were recommended by the equipment requirements study in May 1946. Although the Army faced severe budget cuts after World War 2, caused by extreme demobilization, public pressure, servicemen pressure for demobilization, and the debate if nuclear weapons would replace conventional armies, the Army still decided to develop its heavy tank.

Multiple conferences were held at the Detroit Tank Arsenal in 1948 to establish the specifications of the new heavy tank. Using previously developed vehicles, such as the T34, these conferences combined with studies from the Detroit Tank Arsenal estimated that a lighter heavy tank could be made by shortening the T34’s hull, using highly angled armor, and arming it with a lighter version of the 120 mm T53 gun that was used on the T34. This modified design would weigh 58 US tons (52 tonnes) and met firepower, protection, and mobility requirements.

The characteristics of the now designated T43 were specified as a feasible design in December 1948. The tank kept the 80 inch (2,032 mm) diameter turret ring, the crew was reduced from 6 to 4 members by eliminating the assistant driver and one of the two loaders. By eliminating one of the loaders, the need for an ammunition handling system was identified. The tank was to have 7 road wheels, compared to 8 road wheels on the T34, with a ground pressure of 11.6 psi (80 kPa) and 28 inch (711 mm) wide tracks. The 12-cylinder gasoline Continental AV-1790-5c engine with a gross 810 horsepower (Net 690 hp) was selected in combination with the CD-850 transmission. A supercharged version of the AV-1790 was considered, which would have delivered a gross 1,040 horsepower, but this would have required the design of a new and untested transmission. A lighter version of the 120 mm T53, along with a .50 caliber coaxial machine gun, were to be installed in the combination gun mount T140. The design also called for two .30 caliber remote-controlled machine guns mounted in blisters on the turret side along with a .50 machine gun for anti-air purposes. The main gun was to be elevated and traversed by an electric-hydraulic system. A range finder, direct sight telescope, lead computer, and panoramic telescope were to be used for the fire control system. The T43 presented 5 inches (127 mm) of the frontal hull and turret armor.

The early design concept of the T43 Heavy Tank. Note the remote-controlled blister machine guns at the back of the turret.

Arming the T43

The previously mentioned conferences held at the Detroit Tank Arsenal in 1948 decided in December that the T43 heavy tank was to be armed with a lighter version of the 120 mm T53 which was used on the T34 heavy tank. The 120 mm T53 gun came into existence after the Ordnance Department undertook design studies in early 1945 to modify the 120 mm M1 anti-aircraft gun to serve as a tank gun. These studies determined that the 120 mm T53 would achieve greater anti-tank performance than the 105 mm T5E1 and the 155 mm T7 which were used on the T29 and the T30.

The 120 mm T53 was a rifled gun, 60 calibers in length (7.16 m), and weighed approximately 7,405 pounds (3,360 kg). It used two-piece ammunition, like the anti-aircraft gun it was derived from, and could handle a maximum pressure of 38,000 psi (26.2 x 10^4 kPa). The gun could fire an estimated 5 rounds per minute and was loaded by two loaders. Its Armor Piercing (AP) round was estimated to be able to defeat 7.8 inches of armor at 1,000 yards and 30 degrees (198 mm at 910 m). Its High Velocity Armor Piercing (HVAP) round was estimated to be able to defeat 11 inches of armor at 1,000 yards and 30 degrees (279 mm at 910 m).

The new guns that were proposed for the T43 were the T122 and T123 120 mm guns. These guns also used two-piece ammunition and were both 60 calibers in length as well (7.16 m). The T122 was virtually the same gun as the 120 mm T53 but weighed approximately 6,320 pounds (2,867 kg), 1,085 pounds (492 kg) lighter than the T53. The T123 was a more powerful gun than its T53 and T122 counterparts.

The T123 was made with cold working techniques. This meant that the gun was made at temperatures below the point that would change the structure of the steel. The advantage of using cold working techniques instead of hot working techniques, which was used for the T53 and T122, is that the material becomes harder, stiffer, and stronger. By using cold working techniques, the T123 gun was both lighter and more powerful than the T122. The T123 weighed approximately 6,280 pounds (2.849 kg) and could handle a maximum pressure of 48,000 psi instead of 38,000 psi (331 mPa instead of 262 mPa). The increase in pressure effectively meant that the US army could fire the gun with more propellant and thus increase the gun’s muzzle velocity and penetration.

During the October 1949 Detroit Arsenal Conference, the following estimated details about the proposed guns and ammunition types were presented:











Muzzle velocity

3,100 fps
945 m/s
3,550 fps
1,082 m/s
3,300 fps
1,005 m/s
3,300 fps
1,005 m/s
4,000 fps
1,219 m/s
4,200 fps
1,280 m/s

Penetration, 1,000 yards 30 degrees (914 m)

8.4 inch
213.4 mm
10.9 inch
276.9 mm
14.5 inch
368.3 mm
9.2 inch
233.7 mm
12 inch
304.8 mm
13.6 inch
345.4 mm

Penetration, 2,000 yards 30 degrees (1829 m)

7.6 inch
193 mm
8.8 inch
223.5 mm
13.6 inch
345.4 mm
8.3 inch
210.8 mm
10.2 inch
259.1 mm
12.3 inch
312.4 mm
Ammunition table as presented during the October 1949 Detroit Conference
Source: Kenneth Estes,

A gun-versus-armor test for Army Field Forces representatives was reported on December 19th, 1949, carried out at Aberdeen Proving Ground. In this test, various guns were selected to try and penetrate a 5 inch (127 mm) plate of armor at 55 degrees, representing the upper hull armor of the IS-3. The 120 mm T53, the gun on which the T122 was based, failed to penetrate the armor.

On February 16th, 1950, Ordnance obtained approval for the development of the T122 and the T123 guns.

Development of 120 mm ammunition, which had been going on since the end of WW2, placed much emphasis on HVAP and HVAP-DS (High Velocity Armor Piercing Discarding Sabot) rounds. These rounds needed valuable resources, such as tungsten, and caused very high bore erosion which significantly lessened the gun tube life. The advantage was that these rounds were subcaliber rounds, which resulted in high muzzle velocities and flat trajectories to the target. Various studies were conducted which concluded that the HVAP rounds showed no better results than a full caliber APC round. Because the T123 fired its ammunition at a higher muzzle velocity, it was an economic solution, as its APC round performed better than the APC round of the T122 and performed sufficiently enough for it to be used instead of the T122’s HVAP round. In a way, the T122 was seen as an interim gun until the development of the T123’s ammunition was completed.

Additionally, new advances made the development of 120 mm HEAT ammunition viable for the T43. The development of the T153 HEAT ammunition began on September 1st, 1950. These rounds presented high muzzle velocities without losing penetration over distance or impact. The T153 was initially estimated to penetrate 13 inches of armor (330 mm), but later reached 15 inches (381 mm) of armor penetration at all ranges. The HEAT round had a muzzle velocity of 3,750 fps (1,143 m/s), which made it theoretically more accurate than the APC round, which had a lower muzzle velocity.

The T123 was initially mounted in the same T140 gun mount as the T122 gun, but further studies resulted in the design of a more conventional and reliable gun mount for the T43 which was implemented into all production tanks. This redesigned gun mount received the designation combination gun mount T154 and is first mentioned in an OCM of July 10th, 1951. The redesigned gun mount resulted in a redesign of the T123 gun, which was now known as the T123E1 and featured a quick change gun tube.

Various ammunition types were developed for the T53, T122, and T123 guns. The T14E3 APC round was developed for the T43 and T122 guns, while the T99 APC round was developed for the T123. An AP round was developed for both the T122 and T123 guns as well, designated the T116 (for the T122) and T117 (for the T123), respectively. Additional ammunition types that were in development guns were the T102 HVAP-DS, T153 HEAT, T143 HEP, T15 HE, T147 Target Practice, T16 Smoke, and T272 Canister rounds.

Projectiles and propellant for the T123 120 mm gun.

Development on the T123 proceeded so quickly and satisfactorily, that the development of the T53 and T122 guns was canceled on either February 6th, 1952, April 10th, 1952, or May 1952, depending on sources.

The T123E1 was selected as the main gun of the production vehicles. The development of various ammo types for the T123 gun was eventually canceled. In June 1953, the T117 AP and the T99 were canceled after the promising T116 APC shell was developed. Eventually, three types of ammunition were required for service: APC, HEAT, and HE, although smoke and a target practice round were developed and used as well.

The 120mm T123E1 gun, the main armament of the T43.
Source: Tankograd T-10

How many T43’s do we need anyway?

The new heavy tank faced some initial criticism from a British liaison officer, who identified that the vehicle did not comply with expected agreements of the upcoming Tripartite Tank Conference between Canada, Britain, and the United States planned in March 1949. Additionally, the transportation, logistic divisions, and the Army General Staff questioned the capability of the industry, logistics, and transportation resources to support the active service of a heavy tank.

The Tripartite Conference was meant for Canada, the USA, and the UK to establish certain requirements for tanks, like retaining the light, medium, and heavy tank classes. The conferences focus on simplicity, maintenance, economy, high production rate, low cost, reduced weight, and reliability. The idea for the medium and heavy tanks was that the UK and US developers designed separate guns, ammunition, and chassis and then conducted tests to determine the best. The results were to be combined into a single vehicle. This never really happened except for the specifications of the heavy tank.

Lieutenant Colonel Walter B. Richardson

Luckily for the T43, a previously mentioned advocate of the heavy tank, Lieutenant Colonel Arthur Stuart from the Marine Corps, was part of the Ordnance Technical Committee and thus in the ideal position to push for the introduction of the T43 heavy tank. Additionally, the Marine Corps advocate was supported by Lieutenant Colonel Walter B. Richardson from the Army, who was a veteran tank commander. Both services could count on support for the development of the T43 from both studies and policy boards.

On February 18th, 1949, an advisory board from Army Field Forces endorsed the heavy tank and also designated the heavy tank as the new main anti-tank weapon of the US Army, which meant the end of the tank destroyers in the US Army. The board then specified the required amount of heavy tanks. One battalion of each armored division (which consisted of 4 battalions in total) became a heavy tank battalion fielding 69 T43 tanks. The board determined the need for 12 divisions which were to be immediately mobilized in the case of war (1,476 heavy tanks), which would eventually grow to a full fighting force consisting of 64 armored divisions in the case of World War 3 (to put this into perspective, the US Army only fielded 20 armored divisions in WW2), resulting in a grand total of 11,529 T43 heavy tanks (in comparison, Germany only built a combined number of around 1,800 Tiger 1 and Tiger 2 tanks during World War 2). The chairman of the advisory board, Major General Ernest N. Harmon, also stated that:

‘’Unless our tank development situation is improved, we cannot expect to have enough tanks to support a major ground conflict for at least two and a half years after an emergency is declared to exist.’’

The Marine Corps formed their own Armor Policy Board on April 15th, 1949, to determine the requirements and usage of tanks in the cold-war era doctrine. Created through the efforts of Arthur J. Stuart, the board consisted of veteran battalion commanders of the war in the Pacific. The board determined that a heavy tank was desirable to provide support to the medium tanks during landing operations in the case of an armored counter-attack and to assist in the destruction of heavy fortifications. The board determined that three heavy tank battalions were needed in a wartime situation, but none during peacetime. To keep a trained manpower pool, a number of heavy tanks had to be acquired and combined with armored divisions in times of peace so that the crews were still able to train on the vehicle. Eventually, the Marine Corps put out a requirement for 504 heavy tanks, of which 55 were to be reserved for the three heavy tank battalions and 25 for training purposes, while the rest served as reserves.

After various reviews, the general staff approved the development and production of pilot vehicles on May 19th, 1949. Not long after the approval by the Army, the Marine Corps made their own order for additional pilot vehicles as well.

The T43 starts taking shape

Not long after the approval for pilot vehicles, the use of an elliptically shaped hull and turret, designed by Engineer Joseph Williams, was proposed. The elliptical shape improved the armor-to-weight ratio of the T43 by presenting highly angled armor with decreasing actual armor thickness the more angled the armor got and thus lessening the armor needed to provide 10 inches (254 mm) of effective armor. The appearance of the T43 changed and the new design was studied during conferences at Detroit Arsenal in October and December 1949. These conferences drastically altered the specifications of the T43.

Mock-up of an early version of the T43 without the remote-controlled machine gun blisters.
Source: Firepower, Hunnicutt

The turret ring was to be broadened from 80 inches to 85 inches in diameter (2,032 mm to 2,159 mm), the crew increased to 5 crew members by adding a loader because the planned automatic loading equipment was part of a different project, the elliptically shaped armor reduced the estimated weight to 55 US tons (49.9 tonnes) and a periscopic sight was added as a backup for the gunner’s rangefinder. The commander received gun controls to enable him to override the gunner and aim at a different target if necessary. Additionally, with the introduction of a second loader, an electric loader safety was added in order to move the second loader away from the recoiling breach when the gun was fired. A new concentric recoil cylinder was chosen to replace the previous three-cylinder recoil system. Other additions were the installation of an auxiliary engine-generator to enable the operation of the electrical systems without the main engine running, specifying quick-change barrels for the main gun, a cant-corrector for increased accuracy, and vane sight to help reorientation. The T140 gun mount was reduced in size and could accommodate a pair of .30 or .50 caliber machine guns. Various components were eliminated, including the .30 caliber remote-controlled blister machine guns, the gunner’s direct sight telescope, the panoramic telescope, and the lead computer. These changes were published on April 24th, 1950 and approved by the Army Staff on June 28th, 1950.

In addition, an OCM published on July 19th, 1950, mentions the development of multiple bulldozers for multiple tanks, including a bulldozer blade, designated T18, for the T43 Heavy Tank. Another OCM, published on August 17th, 1950, mentions the development of multiple flotation devices, including device T15, which was meant for the T43.

The US Army Tank Crisis

While the Americans were busy designing, developing, and adjusting their tank designs for a future war, the war came to them. Across the Pacific, after a period of border clashes and disputes, on June 25th, 1950 at 0400 hours, the North Korean Army invaded South Korea. The ROK army was taken completely by surprise and, 3 days later, on June 28th, Seoul fell to the North Koreans. The North Korean army pushed the ROK Army and its allies back to the Busan Line in August, which the United Nations managed to hold and eventually turn the tables after the Incheon Landing on September 15th, 1950.

Like the South Koreans, the Americans were also taken completely by surprise when the North Koreans invaded the South. Although reports had suggested a possible invasion, these were mostly ignored, as Korea was not seen as a likely theatre of war by the Western ministries compared to other possible theatres. The US and its allies feared that the Korean War would lead to the beginning of a new World War in which the West faced off against the East, a war which the US was ill-equipped to fight.

In June 1950, the Army’s Armored Panel reported that the Army and the Marine Corps had a combined number of 4,752 battle-worthy and in total 18,876 tanks. The Soviet Union had an estimated number of 40,650 tanks, of which an estimated 24,100 tanks were identified as reserves. Additionally, the Panel stated that the Soviet tanks were ‘’superior to any we now have.’’ Combine this with the previously mentioned statement of Major General Ernest N. Harmon in February 1949, which stated that the US could not expect to have enough tanks to support a major ground conflict for two and a half years after an emergency was declared, it can be concluded that the situation in which the US Army found itself in when the Korean War broke out was very dire.

Thus, the US Army had to go to war in Korea with outdated World War 2 equipment and, in addition, might have had to fight a new World War in which the outnumbered US tanks would have to face off against IS-3 heavy tank among other Soviet tanks. In response, the US Army Field Forces declared a Tank Crisis on July 12th, 1950. This Crisis was followed with a Crash Program to develop and produce the new generation T41, T42, and T43 tanks by any possible and plausible means, while, at the same time, refitting and refurbishing the US Army’s stock of World War 2 M4 Shermans and M26 Pershings. The US knew of the issues that a Crash Program could bring during the development, in the form of design problems and delayed fielding of the vehicles because of rapid design without proper testing, but the situation had such urgency that they accepted the risk. Between the declaration of the Tank Crisis and the armistice between North and South Korea on July 27th, 1953, the US funded 23,000 and produced 12,000 tanks.

Keeping the T43 project alive

When the Korean War broke out, the T43 existed only as a full-scale wooden mockup. Even worse for the T43, various parties within the Army were considering the cancellation of the T43. The Ordnance Department redefined military characteristics on April 24th, 1950, before the outbreak of the Korean War, which had made the T43 a less relevant project. In the spring of 1950, the Army Chief of Staff General, Joseph Lawton Collins, was making published statements on the supposed imminent obsolescence of the tank, with medium and heavy tanks in particular.

The earlier mentioned Ordnance Technical Committee member, US Army Lieutenant Colonel Walter B. Richardson, would also reveal a three-way struggle within the Army to his fellow committee member of the Marine Corps, Lieutenant Colonel Arthur J. Stuart. This struggle between the Infantry, Armor, and Ordnance branches was over the T42 medium tank project, with the Infantry desiring greater anti-tank performance from the 90 mm gun. The Logistics Division of the Army had presented a study to General Joseph Lawton Collins, with the recommendation of canceling the T43, as the national war economy would have severe difficulties in producing sufficient numbers of heavy tanks to equal Soviet stocks and production. Additionally, it was also expected that the experimental HEAT ammunition of the T42’s 90 mm gun could penetrate the armor of the Soviet heavy tanks.

In September 1950, the Detroit Arsenal conducted a study to arm the T43 with the T15 90 mm gun in a smaller turret. The new design reduced costs and weighed around 45 US tons instead of 55 US tons (40.8 tonnes instead of 49.9 tonnes). The T15 90 mm was an experimental upgrade mounted on the M26 Pershing around 1945 in the form of the T26E4. The T15 was a two piece ammunition gun which could penetrate 6.2 and 9.2 inches at 1,000 yards at 30 degrees (157.5 mm and 233.7 mm at 910 m), with a muzzle velocity of 3,200 and 3,750 fps (975 m/s and 1,143 m/s) for the AP and the HVAP rounds, respectively. The US Army discontinued developing a Pershing with the T15 90 mm gun because of practicality reasons which limited the performance of the vehicle. This study seems to have been initiated by advocates of the 90 mm gun with the Army Staff, but the exact reasons for this study remains vague except to reduce weight and costs of the T43.

A mockup of the early T43, according to Hunnicutt. According to Kenneth Estes, this was a mock-up of a T43 armed with a 90 mm gun.
Source: Firepower, Hunnicutt

Although the Army Chief of Staff and the Logistics Division were in favor of cancelling the T43, various forces within the Army would see to it that the T43 was ordered for production. The Army Field Forces were strongly opposed to the Army Chief of Staff for the following reasons. The 90 mm HEAT ammunition was unproven, the HEAT round could easily be defeated by spaced armor, which reports suggested that the Soviets were using, the round would be inaccurate after 1,000 yards (910 m) and even though a medium tank capable of defeating all enemy armor could be delivered, heavy frontal armor was still necessary to perform breakthrough or defensive operations.

Lieutenant Colonel Arthur J. Stuart also used these arguments when he wrote to his superiors of the Marine Corps to solidify their support. This resulted in a letter from the Marine Corps staff on April 20th 1950 to the Naval Planning Group, that the Marine Corps had no heavy tanks and that these were needed to provide defense against enemy armor.

Brigadier General Bruce C. Clarke
Source: US Army

When the Korean War began, the two Lieutenant Colonels also received support from the Armor Branch of the US Army. Brigadier General Bruce C. Clarke, the former assistant commandant of the Armor school and former member of the 1949 Army Field Forces Advisory Panel, which heavily endorsed the adoption of the T43. He had observed the Soviet build-up of forces in Europe while commanding a brigade in West Germany. He responded by calling for the ‘’immediate initiation of quantity heavy tank production.’’ With the support of the Army Field Forces, Brigadier General Bruce C. Clarke, and the endorsements of all the Army General Staff, the Army Chief of Staff had no other choice than to approve limited heavy tank production and the activation of a limited number of heavy tank battalions for evaluation in August 1950.

Lieutenant Colonel Walter B. Richardson learned that just 80 T43 tanks were approved for production and urged Lieutenant Colonel Stuart to make the Marine Corps support of the T43 project clear, so as to get more leverage for full heavy tank production. Three General Staff members of the US Army contacted Arthur J. Stuart, urging the Marine Corps to reveal their stance on the T43. As a result, the commandant of the Marine Corps wrote a letter to the Army Chief of Staff on September 15th 1950, to notify him of the Marine Corps requirement for a heavy tank and he requested whether production was planned for a heavy tank and what the estimated costs would be.

On November 7th 1950, a new designation system was implemented. Rather than classifying tanks by their weight in the light, medium and heavy categories, the tanks were now classified according to their main armament. In this case, the Heavy Tank T43 became the 120 mm Gun Tank T43.

The Army Staff confirmed their order in December 1950 for the production of 80 T43 tanks. In turn, the Marine Corps confirmed their order of 195 T43 tanks on December 20th 1950, which was later increased to a total of 220 heavy tanks costing $500,000 each (close to $5.4 million in 2019). An order of 300 T43 heavy tanks was placed with the Chrysler Corporation by the US Army and Marine Corps, in addition to six pilot vehicles which were already ordered on January 18th 1951.

The first T43 was completed and delivered to the Aberdeen Proving Ground in June 1951.

120mm Gun Tank T43

The 6 prototype versions differed from each other in multiple ways. The sources only mention specific details on the pilot vehicles #1, #3 and #6. These 6 pilot vehicles were also significantly different from the actual production vehicles. These differences in between the pilot vehicles included the main gun, sand shields, a pistol port, a ladder, muzzle brakes and driver periscopes, among others. The first two pilot vehicles were made according to the initial drawings and the other four according to early production drawings. The design of the final three pilot vehicles was carried out by Chrysler. The 6 pilot vehicles are essentially divided in two versions: the first 2 Pilot vehicles and the later 4 pre-production vehicles, of which the last 3, designed by Chrysler, were designated as 120mm Gun, Tank T43E1 on July 17th 1952. This was done because the differences between the initial T43 Pilot vehicles and the final three pre-production vehicles was large enough to obtain a new designation.

Some key features of the pilot vehicles which were removed on the production vehicles included a two armed gun travel lock, exhaust deflectors to prevent the suction of hot exhaust gasses in the engine cooler, exhaust pipes from the personal heaters through the hull and a track tensioning idler in front of the sprocket.

120mm Gun Tank T43, Pilot #1


T43 Pilot #1 weighed approximately 55 US tons unstowed and 60 US tons combat loaded (49.9 and 54.4 tonnes respectively). The vehicle was 22.94 feet (7 m) long without including the gun, 12.3 feet (3.75 m) wide and 10.56 feet (3.22 m) tall. The T43 was an impressive tank to see. The tank was operated by a five-man crew, consisting of the Commander (turret rear), Gunner (turret rear, in front of the Commander on the Commander’s right side), two Loaders (middle fighting compartment) and the Driver (front hull). The turret had two hatches, one for the commander and one for the loaders and the gunner.

T43 Pilot #1, note the pistol port on the side of the turret. Taken at Aberdeen Proving Ground July 7th 1951.
Source: Firepower, Hunnicutt


The hull was a mix of an elliptically shaped cast (mild steel, casted by General Steel Castings Corporation) and rolled steel which was assembled by welding. An elliptical shape is one of the most efficient ways to make a hull with maximum curvature across the front and sides, putting maximum actual armor where it is needed (the least angled parts of the armor). The armor is most vulnerable head on, but the more the projectile hits to the side of the armor, the more effective the armor gets because the angling gets steeper. The extreme angling of the elliptical shape also makes it more likely for a projectile to deflect if it does not hit the armor head on.

The front hull upper glacis presented 5.0 inches (127 mm) of armor at an angle up to 60 degrees vertically. This gave the T43’s upper glacis a minimal effective thickness 10 inches (254 mm) at every angle. The armor at the transition from the upper to the lower glacis was thicker than 5 inches (127 mm), the exact thickness is not specified by the sources. The advantage of an elliptical hull is that the armor is highly angled at every point and gets more effective the more away from the middle the shell hits the elliptical shape. The lower glacis was 4 inches thick, angled at 45 degrees from vertical. The minimal effective thickness of the lower glacis was around 7.1 inches (180.3 mm).

The front of the elliptically shaped hull of the T43, the first vehicle to implement this technique.
Source: Firepower, Hunnicutt

The sides of the T43 had an elliptical shape, like the front of the hull. Both the upper and lower glacis of the side armor presented armor equalling 3 inches (76.2 mm). The armor of the upper glacis was angled at 40 degrees from vertical, which meant it presented around 2.3 inches (58.4 mm) of actual armor. The side hull lower glacis was angled at 30 degrees from vertical, which meant it presented around 2.6 inches (66 mm) of actual armor. As with the frontal armor, the actual armor was thicker at the transition point from the upper to the lower glacis, but the exact thickness is not specified by sources.

The side of the elliptically shaped hull of the T43.
Source: Firepower, Hunnicutt

The rear of the hull was not elliptically shaped, like the front or the sides of the hull. The upper rear armor plate was 1.5 inches (38.1 mm) thick at 30 degrees vertical. This gave it an effective protection of around 1.73 inches (43.9 mm). The lower rear armor plate was 1 inch (25.4 mm) thick at an angle of 62 degrees vertical, which presented an effective armor of 2.13 inches (54.1 mm).

The floor of the T43 was, like the front and the sides, elliptically shaped. An advantage of an elliptically shaped floor is that it better deflects the blast of a mine because of its curved shape. The floor armor of the T43 lessened gradually from 1.5 inches (38.1 mm) at the front, to 1 inch (25.4 mm) in the center and 0.5 inch (12.7 mm) in the rear of the hull. The top of the hull was 1 inch (25.4 mm) thick.

The gun travel lock was located at the right of the rear hull plate. An interphone control box was located on the left side of the rear hull plate. Two storage boxes were located on both fenders, one large and one smaller. Two outlets were located at the upper right side of the hull (near the turret ring). These were outlets for the bilge pump and exhaust pipe for the personnel heater. The T43 had two pairs of lamps installed on the front of the hull. On the left side was a combination of a headlamp and horn and, on the right side, a blackout lamp (for convoy driving) and a headlamp. Additionally, a blackout marker was installed on both sides.

The headlight design of the first pilot vehicles on the top picture and the exhaust pipes of the personnel heater and bilge pump on the bottom picture.
Source: Firepower, Hunnicutt

The driver was located at the front of the hull, in the middle. The driver used a mechanical wobble stick to steer the vehicle, which was situated between the driver’s legs. At his feet were the brake (left) and accelerator (right) pedals. The horn button and primer pump were situated at his left and a handbrake lever on his right. In front of the driver were a performance indicator, an instrument panel, periscopes (T36 periscopes for the first 4 pilot vehicles), and a hand throttle lock. The seat could be tilted to the side and locked in place with the help of a lever and a clamp. Underneath the seat was an escape hatch for the driver, which was opened by pulling the hatch release lever, after which it would fall open. The driver’s hatch was a sliding hatch that would slide to the side when opened. Behind the driver were the fighting compartment, turret, and engine.

The driver’s compartment.
Source: Firepower, Hunnicutt


The T43 was powered by the gasoline 12 cylinder AV-1790-5C engine. This air-cooled engine developed an 810 gross horsepower at 2,800 rpm and a net 650 hp at 2,400 rpm, which gave the vehicle a net horsepower to ton ratio of 10.8. The T43 used the General Motors CD-850-4 transmission, the same transmission that was used for the M46, M47 and M48 Patton tanks, which had 2 gears forward and 1 for reverse. Combined, this powerpack gave the T43 a top speed of 25 mph (40.2 km/h) on a level road. It had a fuel capacity of 280 gallons which gave it a range of approximately 80 miles (130 km) on roads.

The T43 used a torsion bars suspension with 7 road wheels and 6 return rollers per track. In addition, the T43 had a compensating idler at the front of the tracks and a track tensioning idler in front of each sprocket. It had 3 shock absorbers fitted on the first 3 road wheels and 2 on the last two road wheels. The T43 had 13 teeth and 28.802 inches (731.57 mm) diameter drive sprocket at the rear of the vehicle.

The lower hull of the T43, note the track tension idler before the sprocket, a feature only used in the pilot vehicles.
Source: Firepower, Hunnicutt

The T43 could use either the T96 or T97 tracks and had 82 track links per side. The tracks were covered by a small side skirt. The tracks had a width of 28 inches (711.2 mm) and a ground contact length of 173.4 inches (4.4 m). This gave the T43 a ground pressure of 12.4 psi (8,500 kPa). For comparison, a human foot has an average ground pressure of 10.15 psi (7,000 kPa). The tank had a ground clearance of 16.1 inches (409 mm) and the ability to climb a 27 inch (0.686 m) vertical wall. It could cross trenches of up to 7.5 feet (2.29 m) wide, could climb a 31-degree slope, and ford 48 inches (1.219 m) of water. The T43 was able to pivot steer as well.


The T43’s turret was a single steel casting. Like the hull, it was cast in an elliptical shape. The front of the turret was the most armored part and the thickness gradually decreased from the front to the rear of the turret. The gun mantlet had a thickness from 10.5 to 4 inches at a degree from 0 to 45 degrees vertical (266.7 mm to 101.6 mm). At its thinnest, this would give the T43’s gun mantlet a minimal effective armor of 5.66 inches (143.76 mm). The front of the turret had 5 inches (127 mm) of armor at 60 degrees vertical, which gave it an approximate effective armor of 10 inches (254 mm).

As previously stated, the side armor gradually lessened from the front to the rear of the turret. The side armor lessened from approximately 3.5 inches to 2.5 inches and was sloped at an average of 40 degrees vertical (88.9 mm to 65.5 mm). Pilot turret number 6 was tested by Aberdeen Proving Ground between September 8th and 17th 1952. This was done by firing 120 mm AP T116 ammunition (the ammunition the T43 would use) on the front (avg. 4.73 inches, 120.14 mm) and the frontal sides (avg 5.25 inches, 133.35 mm, 30 degrees longitude) of the turret, 90 mm AP T33 and 90 mm HVAP M304 ammunition at the frontal sides (avg. 3.63 and 3.46 inches respectively, 92.2 mm and 87.88 mm, 30 degrees longitude), 76 mm APC M62A1 and 57 mm AP M70 ammunition at the sides of the turret (avg. 3.28 to 3.10 inches, 83.31 to 78.74 mm, 90 degrees longitude).

Turret test of the T43 pilot turret.
Source: Aberdeen Proving Ground

The following observation was made: there were large differences in protection from a direct frontal attack as compared to a 30-degree flank and that this condition could be somewhat improved by a slight change in the turret wall thickness to increase its protection. The wall thickness decreased rapidly from the front to the sidewall areas and could be much improved by making this decrease more gradual.

A picture that represents the gradual lessening of armor from the front to the rear.
Source: Aberdeen Proving Ground and author

The rear of the turret had 2 inches (50.8 mm) of armor at 40 degrees vertical, which gave it an effective armor of approximately 2.61 inches (66.29 mm). The turret had 1.5 inches (38.1 mm) of armor at 85 to 90 degrees vertical. An armor plate was bolted on the turret at the gun’s position to facilitate the removal of the gun. Additionally, an armor plate was bolted on the top of the turret in front of the commander’s hatch and above the gunner. The back-up periscope of the gunner was installed on the top left of the armor plate. The loaders and the gunner had to share just one escape hatch, while the commander had his own. The safety of the loaders and the gunners when they needed to escape the vehicle seems questionable to say the least.

Top view of the T43 Pilot #1, note the loaders and gunner escape hatch in the middle right of the turret.
Source: Firepower, Hunnicutt

The commander was located in the rear of the turret, the gunner was located in front of the commander on the commander’s right side and the two loaders were located at the front of the turret at both the left and right side. To accommodate the gunner’s seat, a decrease was designed in the turret bustle which can be identified by a weird bulge at the bottom of the turret.

Commander’s seat of the T43.
Source: Firepower, Hunnicutt

External features of the T43 Pilot #1 turret included a pistol port on the left side wall, a ladder on the right side wall, a handrail on both sides, a handrail on the rear, a stowage rack on the rear, mounting for a jerry can on both sides at the rear of the turret, the protective blisters of the T42 rangefinder sticking out on both sides at the middle of the turret, a ventilator inlet on the left side of the commander’s cupola, two receptacles for radio antennas on both sides of the commander’s cupola and multiple lifting eyes on the front and the rear of the turret.

The commander’s cupola is an interesting development of the T43 heavy tank. The T43 pilot vehicles received the same commander cupola as the M47 Patton, but the production vehicles would receive the M48 Patton commander cupola which was designed by Chrysler, which was smaller than the early type commander’s cupola. It is unclear if the switch from the early type M47 Patton cupola to the M48 Patton cupola was carried out after the production of the 6 pilot vehicles or if this was done during the production of the pilot vehicles, as the last pilot vehicle, Pilot #6, seems to have the M48 Patton cupola. It might be that this switch was already carried out when Chrysler took over the design responsibility of the final three prototype vehicles, but sadly, no pictures of the Pilot #4 or #5 have been found to give support to this theory.

Early production commander’s cupola(top) and production commander’s cupola(bottom)
Sources: Firepower, Hunnicutt and


The T43 Pilot #1 was the only T43 pilot to be armed with the 120 mm T122 gun in the T140 combination gun mount. Every vehicle produced after Pilot #1 used the 120 mm T123 gun. The 120 mm T122 was a rifled gun barrel with a length from muzzle to breech block of 302.3 inches (7.68 m) and the barrel itself was 60 calibers or 282 inches long (7.16 m). The T122 could handle a 38.000 psi (262 mPa) pressure.

T43 Pilot design from the Fort Benning archives, provided by Sofilein.
Source: Fort Benning

Interestingly enough, it seems that Hunnicut has made an error in his sketch of the T43 Pilot #1 in his book: Firepower: A history of the American heavy tank. Hunnicut presents Pilot #1 with the muzzle brake of the 120 mm T53 gun, but without a bore evacuator. Since the later T34 Heavy Tanks were armed with 120 mm cannons with bore evacuators, it would be illogical for a gun of this size and with the technology available, to not have a bore evacuator. In addition, a picture from the Fort Benning archives shows a sketch of the T43 Pilot design with a bore evacuator.

Side drawing of the T43 Pilot #1, note the 120 mm T53 gun without a bore evacuator.
Source: Firepower, Hunnicutt

What is interesting about Pilot #1, is that it seems to never have had the actual T122 barrel as it was intended. Instead of a muzzle brake and bore evacuator, it seems to have a counterweight. A reason for not mounting a proper T122 gun might be because they never intended to test-fire the T43 Pilot #1, because the T43 would never use the T122 gun. Why the T123 gun was never mounted on Pilot #1 in the first place, is unknown. It is possible that the T122 gun was the only available gun at the time and a prototype was needed before a T123 gun could be supplied.

A picture of the T43 Pilot #1 without a tarp covering the Counterweight.

The turret had an electric-hydraulic and manual 360-degree traverse. Additionally, it also used electric-hydraulic and manual elevation, with a range of -8 to +15 degrees. It took 20 seconds for the turret to fully traverse and the gun could elevate 4 degrees per second. The gunner aimed the main gun via the T42 range finder and had a T35 periscope as a backup. The Commander had a set of gun controls and was able to override the Gunner and fire if necessary. In short, the T43 had primitive Hunter-Killer capabilities.

Just two types of ammunition were developed for the T122 gun before its cancellation. These were an AP and an HVAP shot. Both shells were two-case ammunition. The right side loader would load the projectile and the left side loader would load the propellant and slide the ammunition into the gun breech. Before the gun could be fired, the left side loader had to step away from the gun and press the button of an electrical loading safety mechanism, so he would not get in the way of a recoiling 6,320 pound (2,870 kg) gun. The AP projectile and the propellant both weighed 50 pounds (22.67 kg), which meant that the left side loader had to slide a 100 pound (45.36 kg) round into the gun breach. The AP projectile of the T122 had a muzzle velocity of 3,100 fps (945 m/s), which could penetrate approximately 7.8 or 8.4 inches (198.1 mm or 213.4 mm) of armor at 30 degrees at 1,000 yards (910 m) depending on sources. The HVAP projectile could penetrate an estimated 14.5 or 15 inches (368.3 mm or 381 mm) of armor at 30 degrees at 1,000 yards (910 m), depending on sources. The maximum rate of fire was 5 rounds per minute and the T43 carried 34 rounds of 120 mm ammunition. Additionally, the T43 Pilot #1 could mount 2 coaxial .50 cal machine guns in the combination gun mount, one on each side of the main gun, and carried 4,000 rounds of .50 cal ammunition. One of the .50 cals could also be swapped with a .30 cal machine gun.

Other Systems

The electrics were powered by the main engine-driven main generator, which produced 24 volts and 200 amperes. An auxiliary generator was used when the main engine was not running. This auxiliary generator produced 28.5 volts and 300 amperes. In addition, a total of 4 12 volts batteries were available, divided in 2 sets of 2 batteries. These batteries were charged by either the main or auxiliary generator.

The T43 Pilot #1 used an AN/GRC-3, SCR 508 or SCR 528 radio, which was installed in the turret. It had 4 interphone stations plus an external extension kit.

The vehicle also had 2 personnel heaters on both sides of the front hull and 3 10-pound CO2 fixed fire extinguishers and 1 additional 5-pound portable CO2 fire extinguisher.

The 120mm Gun Tank T43, Pilot #1 still exists.

The T43 Pilot #1, restored and preserved at Fort Benning in 2020, picture taken by Sofilein.
Source: Sofilein

120mm Gun Tank T43, pre-production Pilot #3

The T43 Pilot #3 was a little different from T43 Pilot #1. The T43 Pilot #3 was, for example, armed with the T123 main gun in the T154 gun mount, which could handle a pressure of 48,000 psi instead of 38,000 psi of the T122 (3,310 Bar instead of 2,620 Bar), making it much more powerful. Its AP round could penetrate an estimated 9.2 inches (233.7 mm) of armor at 30 degrees at 1,000 yards (914.4 m) with a muzzle velocity of 3,300 fps (1,006 m/s). Its HEAT round could penetrate an initially estimated 13 inches (330.2 mm) of armor at all ranges at 30 degrees with a muzzle velocity of 3,750 fps (1,143 m/s) and, later, 15 inches (381 mm). The T123 gun has an effective range of 2,000 yards (1828,8 meters).

The pistol port and the side skirts were removed on Pilot #3.

The T43 Pilot #3 loaded on a train wagon.
Source: Firepower, Hunnicutt

120mm Gun Tank T43E1, pre-production Pilot #6

The 6th pilot vehicle was the Marine Corps pilot vehicle and was the last of the pilot vehicles. This pilot vehicle was, in contrast to the Pilot #1 and #3 vehicles, designed under the responsibility of Chrysler. Some notable differences from the previously mentioned pilot vehicles were the M48 style commander’s cupola instead of the early type M47 Patton one and the headlight guards. In the previous pilot vehicles, these were much more rectangular, but the headlight guard on the Pilot #6 was round. This shape would be used in all the production vehicles. Another distinct feature of Pilot #6 was the T-shaped muzzle break.

The T43 Pilot #6, note the headlight protectors and the T-shape muzzle brake.
Source: M103 Heavy Tank, Kenneth Estes

Pilot Vehicle Gallery

From top to bottom: T43 Pilot #1, T43 Pilot #3, and T43 Pilot #6. Note the differences like the pistol port and Commander’s cupola.

Meanwhile, in the Soviet Union

What the Western Allies did not know was that, after the initial reveal of the IS-3 during the 1945 Berlin Victory Parade, the IS-3 “super” tank had numerous mechanical issues. The design had been rushed into production, which resulted in welds cracking open on the thick frontal armor plates, the suspension had issues and also the engine mounts needed reinforcing. Large numbers of IS-3 heavy tanks were sidelined during an extensive upgrade program that lasted from 1948 to 1952. The IS-3 was produced until 1951, with a production number of around 1,800 tanks.

IS-3 tanks.
Source: T-10 Tankograd

In 1951, the British conducted a study of the effectiveness of the IS-3. In this study, they deemed that the IS-3 would have been more effective if it used either the German 88 mm KwK 43 of the Tiger II or the 85 mm D-5T gun. The 122 mm ammo was deemed too big and too unwieldy in the turret style of the IS-3. If one would compare the space of an IS-3 with that of a T43 Heavy tank, which achieved a maximum of 5 rounds per minute in a more spacious turret with two loaders, it can be concluded that the reload of the IS-3 and, thus, its effectiveness, would be less than its T43 counterpart.

While the Western Allies were still building their tanks to counter the IS-3, the Soviets were already designing its successor. In September 1949, the first prototype of the IS-5 or Object 730 was ready for trials. Although the eventual T-10 would differ slightly from the IS-5 because of various improvements that were made during production, the first vehicles of this new heavy tank were put into production on November 28th, 1953.

IS-5/Object 730 heavy tank.
Source: T-10 Tankograd


The T43 was the logical successor to American World War 2 heavy tank development. By building a lighter version of the T34 heavy tank and using the most advanced techniques at their disposal when it came to steel manufacturing, it was truly a worthy successor of the American heavy tanks. The elliptical hull shape gave the T43 better armor than the T34 while weighing 10 US tons less. Combined with a 48,000 psi gun, the T43 seemed to be the way to go to counter the Soviet IS-3 tank menace.

The problem is that the T43 always seemed to have been in a very tight spot and, even when the Korean War broke out, on the verge of cancellation. The first red flag would have been the ridiculous numbers that the Army suggested it needed, a massive 11,529 tanks for the US Army alone and an additional 504 tanks for the Marine Corps.

The second red flag was the division in the US Army on the T43, which will eventually cause the Army to drop out from bringing the T43E1 to the T43E2 standard and just go with the T43E1 instead. The Marine Corps was called in to bring the additional leverage needed for full-scale production of 300 vehicles, while the Marine Corps only requested about 4% of the total estimated number of about 12,000 tanks needed. With the Marine Corps ordering the most T43 tanks of the two branches, it can be suggested that the heavy tank developed by the Army and for the Army, was in actuality now a heavy tank for the Marine Corps instead. In short, the Army was already very divided on the T43 heavy tank, and thus the M103, before the first prototype was even built.

Luckily for the T43, enough leverage was given by the supporters within the Army and the Marine Corps to get the 6 T43 Pilot vehicles and the 300 production vehicles into production, 6 years after the IS-3 was revealed in Berlin and 1 year before the T-10, the successor of the IS-3, went into its first production run. But the future of the M103 Heavy Tank, albeit a troubled and extensive future, was secured by the supporters of the heavy tank in the Army and the Marine Corps.

Specifications (T43 Pilot vehicles)

Dimensions (L-W-H) 22.94 feet (without gun) x 12.3 feet x 10.56 feet (7 m x 3,75 m x 3,22 m)
Total weight, battle ready 60 US tons (54.4 tonnes)
Crew 5 (Driver, commander, gunner, two loaders)
Propulsion Continental 12 cylinder gasoline AV-1790-5C 650 hp net
Suspension Torsion bar
Speed (road) 25 mph (40 kph)
Armament 120 mm gun T122 (Pilot #1)
120 mm gun T123 (Pilot #2 to #6)
Sec. 3 .50 caliber MG HB M2 (two coaxial, one on turret top) or .30 caliber M1919A4E1 for one of the coaxial machine guns


Front (Upper Glacis) 5 in at 60 degrees (127 mm)
Front (Lower Glacis) 4 in at 45 degrees (101.6 mm)
Sides (Upper and Lower) 3 in at 0 degrees (76.2 mm)
Rear (Upper Glacis) 1.5 in at 30 degrees (38.1 mm)
Rear (Lower Glacis) 1 in at 62 degrees (25,4 mm)
Top 1 in at 90 degrees
(25.4 mm)
Floor 1.5 to 0.5 in at 90 degrees (38.1 mm to 12.7 mm)


Front 5 in at 60 degrees (127 mm)
Gun mantlet 10.5-4 in from 0 to 45 degrees (266.7 mm to 101.6 mm)
Sides 3.25-2.75 at 40 degrees (82.55 mm to 69.85 mm)
Rear 2 in at 40 degrees (50.8 mm)
Top 1.5 in from 85 to 90 degrees (38.1 mm)

Production 6 pilot vehicles

Special thanks to Lieutenant Colonel Lee F. Kichen, USA-Retired


The early design concept of the T43 Heavy Tank with remote control blister machine guns.
T43 Pilot #1
T43 pre-production Pilot #3
T43E1, pre-production Pilot #6

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Archive Sources

Elements of Armament Engineering: Ballistics, Part 2
Standard Military Vehicle Characteristic Data Sheets
Aberdeen Proving Ground Firing Record APG File: 451.6/2, DA File: 470.4/APG
Guns for Heavy Tanks
Advisory Panel on Armor 334/44 August 19 1954
Army Operational Research Group Report 11/51 Performance of British and Russian Tanks
Fort Benning: R.P. Hunnicutt Collection with courtesy of Sofilein


R.P. Hunnicutt:
Firepower: A history of the American Heavy Tank
Patton: A History of the American Main Battle Tank

Kenneth W. Estes:
M103 Heavy Tank 1950-74
Marines under armor: The Marine Corps and the Armored Fighting Vehicle, 1916-2000

Lieutenant Colonel Lee F. Kichen, USA-Retired:
Private Correspondence
On Point, The journal of Army History, Volume 24, no. 4, Spring 2018

Max Hastings:
The Korean war

Technical Manuals:
TM 9-2350-206-12

Additional Sources

Camp Colt to Desert Storm
AFV Weapons 41: M103 Heavy Tank + M41 Light Tank(Walker Bulldog)
History of Acquisition in the Department of Defense, Volume 1
Intimidating the World: The United States Atomic Army, 1956-1960
Tankograd T-10
USMC History Division
The Chieftain’s Hatch: Improving Super Pershing

Cold War US Prototypes

19.5 ton Electric Drive Future Combat Vehicle (E.D.F.C.V.)

USA (1984-1987)
Combat Vehicle – models only

In 1984, the US military was considering the problems connected with a new range of vehicles, such as the M1 Abrams main battle tank and the M2 Bradley Infantry Fighting Vehicle (IFV). As part of the evaluation of trends in future vehicles, a commission was formed to look into the potential for electric drive systems for a 40-ton (36.3 tonnes) (tank) and 19.5-ton (17.7 tonnes) (APC/IFV) platform.

The US Army’s Tank Automotive Command (TACOM) issued a contract to General Dynamics Land Systems for this project – to evaluate existing electric drive technologies to use in future vehicles. This contract was given the number DAAE07-84-C-RO16 and was divided into 2 phases – a third phase was added later under contract modification P00006.

The goal was roughly that of evaluating the ‘new’ (electric drive for vehicles predates armored vehicles themselves) technology available across a variety of platforms for what it may offer for further development. What it actually generated was the realization that electric-drive fighting vehicles were not only possible but had some valuable features worth exploring, especially with regards to a series of heavy IFV platforms. However, like so many other studies, this work faded away and the design work was abandoned. To this day, in 2020, the M2 Bradley remains in service with a conventional power plant along with numerous other armored vehicles in the US inventory. Despite the billions of dollars spent, to date, the US military has yet to capitalize on the potential of electric-drive vehicles.

The beginning

Work on a future electric drive combat vehicle was to consist of three phases of work:

  • Phase I: A survey of existing technology (document JU-84-04057-002)
  • Phase II: Generation of concept vehicles with electric drive
  • Phase III: A parametric study and evaluation with a selection of 3 recommended concepts for further consideration

General Dynamics had actually been looking into the potential of electric drive systems as early as 1981, producing electric-drive concept vehicles for various other vehicle projects. It also had possession of a 6 x 6 wheeled, 15-ton (13.6 tonnes) Electric Vehicle Test Bed (EVTB) it had paid for itself in order to test and validate electric drive. It also had an Advanced Hybrid Electric Drive (AHED) 8 x 8 vehicle in the 20-ton class using lithium-ion batteries.

General Dynamics Advanced Hybrid Electric Drive (AHED) 8 x 8. Source: DiSante and Paschen

The timetable for the project called for Phase I to be concluded by the end of 1984. In the end, the report on this phase was finished in July 1984 and then published in January 1985. By this time, the second phase was already underway, with an expected conclusion date in the latter half of 1985 followed by another report and, starting in the middle of 1986, Phase III running through into the start of 1987.

Why Electric Drive?

The potential of electrical drive systems for tanks was recognized and experimented upon as far back as WW1. An electrical transmission offered the designer a significant freeing up of the internal layout of an armored vehicle, as the drive motors did not have to be next to the engine, and the ability to deliver continuous, reliable power in preference to mechanical systems. This is primarily because an electrical drive system has far fewer moving parts and bearing surfaces than a mechanical system. There are also major advantages, not the least of which being volume. An electrical system could be smaller than the equivalent mechanical system and a smaller volume meant more internal volume in a vehicle for other things and/or a reduction in the amount which needed to be protected by armor – that means less weight too. Electrical transmissions are also quieter due to the absence of gearing and driveshafts and offer the not insignificant potential to provide electrical power for the vehicle’s systems.

One of the biggest advantages of e-drive over a conventional powertrain (liquid-fuel burning engine connected to a mechanical transmission) is that the engine, generators, and motors do not have to be co-located within the vehicle, significantly freeing up potential layouts for the vehicle.

Study concepts

Some 38 possible concepts across the 19.5 (17.7 tonnes) and 40-ton (36.3 tonnes) vehicles were considered over four basic vehicle considerations. Various companies and one university submitted concept plans for the program, namely: Westinghouse, ACEC (Ateliers de Constructions Electriques de Charleroi), Unique Mobility, Garrett, Jarret, and the University of Michigan. All of the options were to consider an automotive scheme for a baseline vehicle.

19.5 ton (17.7 tonnes) Baseline Vehicle Concept. Source: GDLS

Baseline Vehicle Description

The baseline vehicle was a departure from the rather large body of the M2 Bradley. The essential layout, however, was very conventional. Riding on six wheels attached to what appear to be suspension arms, it appears to have torsion bar suspension, with the track running on these 6 sets of road wheels on each side which were divided into two groups of three and supported on the top with a trio of return rollers.

A driver sat in the front left with the power plant alongside on the right. Behind this was the fighting and troops’ space with a turret set slightly back from the center. The two-man turret carried all of the armament for the design, consisting of a single .50 caliber (12.7 mm) heavy machine gun with an elevation range of -15 to +30 and 1,000 rounds of ammunition. On each side of the turret was a pair of Dragon anti-tank guided missile (ATGM) launchers with another 4 missiles stowed at the back of the turret.

Finally, the troop space at the back, as can be imagined from a relatively small vehicle with a turret, was also small. Although only two men are shown drawn in the vehicle, it is probable that another two would be seated opposite for a troop space of 4 men, although how happy they would be to know that they were sat atop the 640-liter fuel tank is anybody’s guess.

It is important to remember though that the vehicle shown in the drawing, whilst more than a mere doodle of a viable armored personnel carrier (APC), should only be taken as an illustration of a possible future APC. The power plant work could just as legitimately be refitted to another vehicle as the key part of the study was not this APC per se, but a study to evaluate these power systems for AFV propulsion.

19.5-ton (17.7 tonne) Vehicle Concepts

With four (five including one minor amendment) configurations being considered, the design task was simplified by the specification of the engines to be used. The 19.5-ton (17.7 tonne) vehicle would use the Cummins VTA-903T generating 500 hp. The engine would then drive generator/s to provide power to various configurations of motors with a goal of a road speed of 45 mph (72.4 km/h).

Dimensions were set with a ‘datum’ concept vehicle with a hull height of 72” (1.83 m), an overall height of 96” (2.44 m), a distance of 150” (3.81 m) from the center of the front road wheel to the rear roadwheel, and a total length of 246” (6.25 m). The tracks were to be 17.5” (445 mm) wide with a total vehicle width of 110” (2.79 m). Armament was to be concentrated on a small turret located centrally width-wise and just back from the center of the length of the vehicle. All of the 19.5-ton (17.7 tonnes) vehicle concepts used an ‘engine forward’ arrangement leaving a large space in the rear of the vehicle suitable for carrying troops or other payloads. Armament was likewise the same on all of the 19.5-ton (17.7 tonnes) concepts: a single heavy machine in the small turret flanked on each side by a fire of anti-tank guided missile (ATGM) launchers.

Each design was identified by a concept number followed by a design number. For example ‘I-5’ was Configuration 1 Design 5, whereas II-5 was Configuration 2 Design 5 and so on. Vehicle concepts selected to go forward from theoretical design to a drawing stage were all allocated a drawing number starting AD-8432-xxxx.

Having outlined various conceptual vehicles, those which were successful were authorized to be drawn and, of those, five 19.5-ton (17.7 tonnes) vehicle concepts were selected on the basis of an efficiency scoring system that assessed a variety of factors such as weight, volume, the efficiency of the system, and technological ease. Despite it being a heavier system than the others, it was the Belgian ACEC system that was selected as being the best of all of the possibilities for the new vehicle. One proviso to this was that the Jarret system was received late in the assessment process and potentially could have been better than the ACEC – the design team recommended it receive further development too.

Garrett 19.5 ton (17.7 tonne) Concept I-1. source: GDLS
Westinghouse 19.5 ton (17.7 tonne) Concept I-2. source: GDLS
ACEC 19.5-ton (17.7 tonne) Concept I-5. Source: GDLS
Garret 19.5 ton (17.7 tonne) Concept I-6. Source: GDLS
Unique Mobility 19.5 ton (17.7 tonne) Concept I-9. Source: GDLS
Unique Mobility 19.5 ton (17.7 tonne) Concept I-9A. Source: GDLS
Garrett 19.5 ton (17.7 tonne) Concept I-10. Source: GDLS
Garrett 19.5 ton (17.7 tonne) Concept IA-1. Source: GDLS
Jarret 19.5 ton (17.7 tonne) Concept IA-3. Source: GDLS
Unique Mobility 19.5 ton (17.7 tonne) Concept II-3. Source: GDLS
Unique Mobility 19.5 ton (17.7 tonne) Concept II-6. Source: GDLS
ACEC 19.5 ton (17.7 tonne) Concept III-2. Source: GDLS
Unique Mobility 19.5 ton (17.7 tonne) Concept III-3. Source: GDLS
Unique Mobility 19.5 ton (17.7 tonne) Concept IV-2. Source: GDLS
ACEC 19.5 ton (17.7 tonne) Concept IV-3. Source: GDLS

Production study

With the ACEC winning out, a production study was conducted as to problems and costs. The 192 hp DC motor in the design was not an issue, as it was already a well established piece of technology. It had already been used experimentally on a Belgian AFV called the ACEC Cobra several years before.

Although the ACEC system had already been used on the Cobra some years beforehand, there were significant differences. The study had selected the 500 hp Cummins VTA-903T whereas the Cobra used the 190 hp Cummins VT 190.

The 417 hp rare-earth metal permanent magnet (PM) generator (a Garrett design) used in the concept study was a problem. The generator required Samarium Cobalt (SmCo – a type of rare-earth magnet), and Inconel (a nickel alloy), an ingredients list which used strategic materials – specifically cobalt, a material which was difficult to work with in manufacturing, as it required special handling to prevent it from being damaged.

The result was that the cost of the drive-system without considering the final drives and cooling was estimated per vehicle at 1985US$19,500 (nearly US$47k in 2020 values) with a projection that the drives for the planned 400 vehicles would cost over 1985US$165,000 (just under US$396,000 in 2020 values).

Alternative Engines

Although the 500 hp Cummins VTA-903T was selected for the purposes of the study, it was accepted that other engines were available. In the end though, other than the possibility of switching to a petrol-turbine, the existing diesel engines were the only technology mature enough to be considered.

Of the 38 possibilities, three systems suitable for the 19.5-ton vehicle were identified. Concept I-5, from the Belgian firm of ACEC, came with the conventional DC (Direct Current) traction motor driven by a permanent magnet AC generator. The second was concept I-10 from the firm of Garrett which used its own AC permanent magnet drive, and finally, from the firm of Unique Mobility was concept IV-2 which used a dual-path AC permanent magnet drive system.

Other systems were considered as showing potential, even though they were not selected. These were the Jarret variable reluctance drive (using a single seed gearbox saving a lot of weight and volume with 84% efficiency) and the Westinghouse DC Homopolar drive (an extremely simple system albeit heavier than the equivalent mechanical system).

ACEC Drive System Detailed

The ACEC drive system consisted of a single 417 hp rare-earth self-excited metal permanent magnet (PM) generator (a Garrett design) operating at 18,000 r.p.m. This oil-cooled generator had an efficiency of 93.5% and a rating of 370 kVA. Connected to the 500 hp Cummins VTA-903T, it required a ratio transfer case operating at a ratio of 6.9:1 to raise the relatively slower rotating speed inside the engine to match that needed by the generator.

This sounded simple enough but the output from the generator was 3-Phase Alternating Current (AC) and had to be rectified into Direct Current for the ACEC motors. This was done using an oil-cooled 6 thyristor rectifier bridge allowing for bi-directional power flow and also for close control over the voltages. Operating at 747 Volts DC, this rectifier was 98% efficient.

ACEC DC traction motor as used on the ACEC Cobra. Source: Janes

The pair of ACEC DC traction motors were air-cooled and each rated at 192 hp, although they could deliver up to 300% of that capacity for up to 20 seconds. These were more than just drive motors too, as they also operated in the manner of generators when run with the field excitation voltage reversed, which allowed for steering and braking with the power generated fed back into the system and adding to the power of the generator. The motors were very compact too, just 2.35 cu.ft. (0.07 m3) each, with a diameter of 430 mm, length of just 460 mm, and a weight of just 700 lbs. (317.5 kg). Operating at 1,887 r.p.m. the motors could work at a maximum of 5,660 r.p.m. (for 20 seconds) operating at 420 Volts DC and with 93% efficiency over a 3 to 1-speed range.

These motors, on their own, were insufficient to provide all the power required to meet the desired road speed of 45 mph (72.4 km/h), so a two-speed 3:1 ratio oil-cooled gearbox was added with a constant mesh gear and clutch system of a type similar to that used in the X-1000 series transmission on the M1 Abrams.

The final element in the drivetrain was the 4:1 reduction ratio heavy-duty planetary drive coupled to the drive sprocket. For the ACEC-system vehicle, a maximum heat rejection of 3,677 BTU/Min (3,879 KJ/ Min) was needed.

ACEC Concept I-5 for the 19.5 ton (17.7 tonne) electric drive vehicle. Source: GDLS

Garrett Drive System Detailed

The Garrett system (I-10) consisted of a permanent magnet AC traction motor rated at 444 hp, also with a 2-speed gearbox and final drives. The AC generator itself was an oil-cooled unit of Garrett design using the rare-earth magnets to supply the field flux and operating at 747 Volts RMS at 18,000 r.p.m. with an efficiency of 93.5 %. As with the ACEC system, a ratio transfer case operating at a ratio of 6.9:1 was needed to raise the relatively slower rotating speed inside the 500 hp Cummins VTA-903T engine to match that needed by the generator.

Garrett Concept I-10 for the 19.5 ton (17.7 tonnes) electric drive vehicle. Source: GDLS

The system from Garrett added an oil-cooled rectifier to provide feedback to the control system for the driver for the steering and braking of the vehicle. Operating at 747 Volts DC, this unit worked at 98% efficiency. This system was connected to a pair of 192 hp traction motors. Operating at 4,600 rpm, these oil-cooled motors, like the motors from ACEC, were capable of operating at up to 300% capacity and running at 18,500 rpm for up to 20 seconds.

The AC traction motors delivered speed across a 4 to 1-speed range but once more, like the ACEC system, was insufficient on its own to provide the necessary top speed desired. This system too was therefore also supplemented by an oil-cooled 2-speed gearbox, once more using a similar gear meshing and clutch system as used on the X-1000 series transmission of the M1 Abrams. Finally, the Garrett system used a 4:1 reduction ratio heavy-duty planetary gear driven by the output from the 2-speed gearbox to move the sprockets.

Cooling was an important factor in all of the system and calculations for the Garrett systems (both I-10 for the 19.5 ton and I-3 for the 40-ton) were calculated. For the 19.5 ton (17.7 tonnes) vehicle, a maximum heat rejection of 4,565 BTU/Min (4,816 KJ/ Min) was needed.

Unique Mobility Drive System Detailed

The drive system from Unique Mobility (UM) was different from the other systems in that it used two different paths for the delivery of automotive power, one mechanical and one electrical. The electrical system alone delivered power for speeds from 0 to 15 mph (24 km/h) and, when more power was needed to go above that, the mechanical system was unlocked and coupled to the electrical system. The control unit then controlled the power between these two units.

The electrical power was provided by a permanent magnet AC generator driven by the engine rectified to DC and then inverted in order to provide power to the traction motors. The generator was an oil-cooled Garrett-type rated at 400 hp and rotated at 18,000 rpm with 93.5% efficiency. The oil-cooled rectifier for this system operated at 685 Volts DC at 98% efficiency and connected to a 284 Volt AC inverter operating at 96% efficiency.

The traction motors used rare-earth metal magnets made from neodymium which removed the problem of the cobalt-type magnets, as the US had adequate stocks of neodymium. The cost of 400 of these power units was estimated to be 1985 US$145,000 (just under US$350,000 in 2020 values). The Garrett traction motors delivered 192 hp each and were able to operate at 200% for up to 30 seconds and deliver power to the final drive units which operated at a 4:1 reduction ratio.

Concept IV-2 from Unique Mobility. Source: GDLS


Switching to an electrical transmission from a mechanical one could have provided several key benefits. It was more efficient, produced less heat through friction, and took up less than half the volume of the mechanical system. Half the volume meant more space available inside for fuel, weapons, and men, or just a smaller vehicle which therefore needed less armor and could be lighter.

With the transmission decoupled from the location of the engine and no drive shafts needed, the designers for the vehicle were free to make some radical layout changes if they wanted. This they did not do for this concept, as the layout remained rather ordinary. It is perhaps that which was the biggest failing of the study, as the vehicle shape and size were dictated from the start, meaning the single biggest freedom provided to the designers was gone. Instead, electric drive could only compete in terms of weight and volume and perhaps it was this ‘dictating the terms of the contest’ which was the main factor in why it was not adopted.

By working their way through the possible vehicle power options, the concept study team had made a clear choice. A relatively small diesel engine and the ACEC DC system were the most efficient and effective e-drive options for a new generation of vehicles in the 19.5-ton (17.7 tonnes) class.

Despite this, however, the idea was destined for obsolescence by the conventional diesel engine and mechanical powertrain on the M2 Bradley. The Belgians had made their ACEC motor-powered APC and even a light tank on the platform, but this American project fizzled out and more than 30 years later the idea of a diesel electric-powered APC has yet to be exploited to its full potential.

Side profile of the EDFCV. While the outside layout of the vehicle was quite interesting, the heart of the project lay within: The hybrid drive. Illustration by Rhictor Valkiri, funded by our Patreon campaign.
3/4 view of the EDFCV, showing the impressive armament and optics. Illustration by Rhictor Valkiri, funded by our Patreon campaign.

Specifications 19.5 ton (17.7 tonne) Concept

Dimensions (L-W-H) 246” (6.25 m) overall, 92.52” (2.35 m) from front wheel to rear (centers) x 110” (2.79 m) x 72” (1.83 m) hull, 96” (2.44 m) overall
Tracks 17.52” (0.45 m) wide, 150” (3.81 m) length ground contact
Total weight 19.5 tons (17.7 tonnes)
Crew ??
Propulsion 500 hp Cummins VTA-903T with electric drive
Speed 5 mph (8 km/h) to 45 mph (72.4 km/h)
Armament Single 0.50 calibre (12.7 mm) heavy machine gun with 1,000 rounds, pair of twin Dragon ATGM launchers with 4 spare missiles


GDLS. (1987). Electric Drive Study Final Report – Contract DAAE07-84-C-RO16. US Army Tank Automotive Command Research, Development and Engineering Center, Michigan, USA
DiSante, P. Paschen, J. (2003). Hybrid Drive Partnerships Keep the Army on the Right Road. RDECOM Magazine June 2003
Khalil, G. (2011). TARDEC Hybrid Electric Technology Program. TARDEC

Cold War US Prototypes

Baldine One-Man Tank

USA (1951-1958)
Light Tank – Design only

On 2nd April 1951, James Joseph Baldine (20/12/1910 to June 1974) of Hubbard, Ohio, USA, submitted a design for a one man tank and, like so many other one-man tank designs, Baldine’s had all the advantages of protecting a single soldier behind armor but also all the same disadvantages of a lack of fightability, observation, and vehicle control. He had, however, carefully considered the control aspect of the one-man tank and devised a foot-pedal control system which would allow the soldier inside to manage the steering and propulsion of the vehicle entirely with his feet allowing him to keep his hands free to operate a weapon. Baldine was no doubt influenced by current events, as the design was submitted at the time of the Korean War (1950-1953) but showed what can only be described as naive thinking in military terms, especially in a post-World War II era. Nonetheless, the design was a thorough one, producing probably the best of all of the one-man tanks and showing how many of the challenges for such a concept could be overcome.

Baldine’s one-man tank of 1951. Source: US Patent 2722986


Baldine’s tank did not separate the engine from the operator (this is what Baldine called the sole crewman), but placed it directly behind him, with the control pedals for steering/braking at his feet. The engine is described only as a four-cylinder, air cooled aviation type motor behind which was a conventional fluid transmission connected to the final drive for the tracks and a power-take-off with a small propeller allowing the vehicle to be propelled in water. Exhaust gases were vented directly out of the top but, with no provision for a fan, the operator would quickly become very tired from the proximity of this hot engine (despite the presence of a bulkhead between the operator and the engine) inside such a small machine. Directly under the crotch region of the pad, under the operator, was the petrol tank for the engine. The tracks for Baldine’s tank are not specified but he describes them only as “an endless track” with suspension of a ‘shock absorbing’ type.


The only mention of armament from Baldine is of a single machine gun in the front. The artwork submitted for his patent application in 1951 seems to indicate a .50 calibre machine gun like the M2 Browning. Fitted within a simple ball-mount in the nose of the tank, it would actually have a potentially wide arc of fire. Ammunition for it was fed from a magazine secured to the side of the nose-wall. A secondary weapon, in the form of a forward firing rocket launcher sticking out of the front, was located to the left of the operator. Fed from a magazine at the rear, the purpose of the rocket launcher is unclear as to whether it was for smoke or anti-tank or other purposes. The exhaust gas from the rocket was directed down below the vehicle to prevent it from giving away the position of the tank and the operator was provided with a sight to try and aim it. No other armament or smoke launchers were provided for, although presumably any soldier inside would also have their personal weapon as well, such as a submachine gun or handgun.


The tank itself was somewhat more complex than many other one-man tank concepts and also a lot larger. Unlike others, where the operator lacks enough space to sit up, Baldine proposed a taller vehicle with a pronounced dome directly over the soldier. Provided with ventilation slots, this dome would provide air and comfort for the solder but was not used for observation. Instead, all observation was conducted through the single large bulletproof glass window located directly to the soldier’s front over the main armament. Access to the tank was gained via a small sliding hatch located midway down its length on the roof, meaning the soldier would be exposed to enemy fire if/when the machine became stuck. 

Cross-sectional view of Baldine’s one-man tank showing the location of the large pad on which the operator lay and the fuel tank (60) underneath him. Source: US Patent US2823393

The Pad

A common flaw in the one-man tank concept is the issue of comfort for the soldier crewing the vehicle. The operator is already very busy having to command, steer, and fight from the tank and obviously this is made harder if they are uncomfortable. Taking a prone position, where the soldier is lying on his front, can become very tiring after a while, particularly after travelling over rough country and having to lift their head up in order to see and fight, which produces additional strains. Baldine’s additional idea to assist his one-man tank concept was the addition of a specially designed sponge-rubber pad on which the soldier could lay. 

Specially shaped, this pad would hold the operator in a steady position, providing support for his arms and chin as well as a wedge shaped block on which his crotch would rest. This crotch-block would prevent the solder from slipping down the mattress and raised edges on the sides and base would stop him from sliding laterally as well. 

The unusually shaped sponge-rubber pad on which the operator would lay showing the crotch block (40) and chin-rest (36/38)US Patent US2823393


The one-man tank idea, something first proposed decades earlier and something which had never seen any successful mass production or use, was a dead idea by the 50’s. It can be surmised that Baldine was motivated by seeing the War in Korea and wanting to do his part for his country and to save the lives of soldiers or maybe just opportunism to try and make some money from an idea. Regardless of his motivations though, the design itself was not a terrible one by any means. As far as the concept goes, the design certainly had merit for the control of the machine and the layout, but the concept of a one-man tank was just fundamentally a bad one. A single soldier would be unable to adequately command, control and fight from the vehicle and the features of the vehicle inherent within the design, such as the low profile, giving low visibility, prevent such an idea being viable. As such, his one-man tank design might have been a very good one-man tank design but the concept was simply a flawed one. As such, his design suffered from those flaws and despite his best efforts could not overcome them. That ended his one-man tank idea.

Baldine also submitted a patent for a game teaching apparatus in January 1951. In 1963, he also designed a portable incinerator for a motor vehicle, designed as a means of disposing of cigarettes and paper items which could be fitted to a standard saloon car for disposing of litter on the move. Neither of those two designs were perhaps as adventurous as his one man tank idea, but Baldine had moved on anyway. It is not known whether Baldine received any financial benefit from his patents, but his one-man tank idea certainly went nowhere. His political career, as Mayor of Hubbard, was far more successful though, serving six consecutive terms. He died in office in 1974.


US Patent US2823393(A) Cushion pad for one-man tank, filed 2nd April 1951, granted 18th February 1958

US Patent US2722986 Braking and Steering Control Mechanism for one-man tank, filed 2nd April 1951, granted 8th November 1955

Hubbard News, 19th June 1974 – Mayor Baldine: an era has ended

Illustration of the Baldine one-man tank, by Yuvashva Sharma, funded through our Patreon campaign.
Cold War US Prototypes

FMC Howitzer Improvement Program (HIP)

USA (1979-1983)
Self-propelled gun – Project only

FMC HIP design. Source: Janes

The SPG deficit

The United States had, by the 1970s, realized that the majority of their artillery was aging rapidly or just out of date. Open topped, slow, vulnerable, based on obsolete chassis, the existing self-propelled guns (SPG’s) in service were not suitable for a potential Cold War showdown with the Soviet Union, which had a more modern SPG force. Early development work took place under the program names Division Support Weapon System (DSWS) and Direct Support Armored Cannon System (DSACS). The DSWS had changed by 1979 into the Enhanced Self-Propelled Weapons System (ESPWS) program with the goal of producing a common platform for self-propelled artillery for the Army.

All of these programs were also grouped under the general name of the Howitzer Improvement Program (HIP). This development was to take multiple strands. One was work commissioned from the firm of Norden to study improvements to the existing M109 fleet as well as an examination of foreign systems in use or development. This included the French GCT and the multinational SP-70 project. The M109, a system developed in the 1950s and first fielded in 1963, was a prime candidate for upgrading or replacement. In 1980, the replacement for the M109, incorporating elements of the other programs, was underway and after 3 years of work several alternatives for replacement or modernization of the M109 had been evaluated as part of the Howitzer Improvement Program known as HIP.

HIP outline

With the multitude of acronyms involved before work had even begun, it is easy to become confused, but the HIP program laid general principles a future system would have to meet to be acceptable. Firstly and most importantly, the caliber was defined. It had to be a 155 mm gun with a barrel length not less than 38 calibers long (5.89 m) and not longer than 50 calibers (7.75m) capable of firing standard 155 mm shells to 25 km. HERA – High Explosive Rocket-Assisted – ammunition would be available in order to extend this range to 30 km. Shells would be loaded by means of an automatic loader system reducing the crew down to a nominal 4 with some optimism that it could be reduced to 3 and operated in an emergency by just 2 men.

Not less than 50 rounds were to be carried with a target of up to 75 shells which, working with the automatic loading system, could deliver between 8 and 12 rounds per minute. If the automatic loading system was omitted and a manual system retained, then the rate of fire would drop to just 4 rounds per minute, as well as impacting the number of crew required to operate the gun. The alternative consideration was a ‘halfway house’ of a semi-automatic system rather than manual or fully automatic with an estimated rate of fire of between 4 and 8 rounds per minute. The desire was for a state of the art system to meet the RAM (Reliability, Availability, Maintainability) requirements with computer-controlled and monitored systems. Fire control was to be by means of an onboard ballistic computer and computer-controlled gun motors. This combination allowed the system to fire, relocate to avoid counter-battery fire, and then fire again in under 1 minute. The ability to avoid enemy counter-battery fire was a significant improvement and step forward.

Protection was to be just of an ‘improved’ type over what (presumably) there already was in comparison on the M109 and the vehicle had to have an NBC overpressure system fitted as standard. A further note was that for self-defense the vehicle would be provided with a single .50 caliber heavy machine gun on the commander’s cupola. For mobility, the HIP required a new powerful engine capable of delivering not less than 20 horsepower per ton capable of propelling the various vehicles based on this chassis to a road speed of 60-75 km/h, to a maximum operational range of between 400 and 600 km. All vehicles had to be capable of transportation via a C-130 transport aircraft.

HIP Chassis family

Each SPG would have an associated and dedicated Ammunition Resupply Vehicles (ARV) with between 80 and 150 additional rounds of ammunition. This vehicle was to be based on the same chassis as the SPG itself, with a crew of 3 or 4 and the same level of protection.

Another vehicle would be the Battery Operations Center (BOC) also based on the chassis with a crew of 7 (in two shifts) and an Armored Maintenance Vehicle (AMV) with a crew of 2 (and 4 mechanics). Each AMV would carry spares, tools, and even a complete spare power pack for the chassis. The vehicles were to be assigned to a battery at the rate of one AMV per battery.

A battery would therefore consist of 3 SPG’s, 3 ARV’s, 1 BOC and 1 AMV for a total of 3 guns, up to 675 x 155mm shells, and between 28 and 45 men.

HIP was to be an integrated part of all Army divisions replacing the vehicles already in service at a rate of one battalion to each Army brigade

Battalion makeup for the HIP program. Source: Author

The FMC Proposal New Start

By 1984, FMC (Food Machinery Corporation) had made their own proposal to meet the demands of the HIP program as specified under the name ‘DSWS New Start.’ The basic arrangement of the proposal was an unusual-looking vehicle with a completely fixed superstructure on the rear of the chassis. The engine was mounted in the front and the ammunition (in drums) sat at the top rear of the casemate. The 155 mm gun mounted into this superstructure was not completely fixed and had the ability to move up to 5 degrees left or right. The driver sat forwards of the casemate, in a raised structure that extended back along the hull into the casemate. This would permit him to come back into the fighting space rather than be isolated in the driving position. The chassis itself was mounted on 7 road wheels with 4 return rollers and drive to the tracks delivered by a front-mounted sprocket. Power would be provided by an unspecified 700 hp engine.


The requirement was for a 155 mm gun 38 to 50 calibers long and FMC’s design was for a 45 caliber weapon which was under development at Watervliet Arsenal. The range required was 25km (30km with rocket assistance) but this FMC proposal gave the maximum range with standard (non-rocket-assisted) projectiles as 23km.

Shells would be delivered via a fully automatic system feeding from two large drums containing a maximum of 50 rounds divided equally, with one drum on each side of the breach. Fifty shells were the minimum required by the program but this FMC proposal could fulfill the other needs for full automation including fuze setting which was incorporated into the breach and was fully compatible with the existing 1 to 8 zone bag charge propellant system or the then newly proposed 5-zone modular propellant. Shells would be reloaded via the Ammunition Resupply Vehicle via two large hatches in the rear of the gun.

The end of the new start

The DSWS project was canceled by 1983. It was seen as being too expensive and too complicated. The focus would instead be on modernizing the existing M109 fleet and the HIP project would roll on sucking in more cash. For their part, FMC had produced a capable design whose biggest flaw was probably not the cost but the lack of a turret. They had met almost all of the requirements set by HIP and would try their hand at the M109 modernization instead, rolling much of their development work into a new M109.


Like many of these multi-year huge contracts in the US, this one is an enormous project of overlapping requirements. The HIP program didn’t end with the cancellation of the FMC DSWS New Start concept, it was still going on into 1991. This was the date by which the vehicles were meant to have been entering service yet development hadn’t even finished and only 8 prototype improved vehicles had even been made by 1989. The project was simply too large and phenomenally expensive. In 1989 alone, for example, the HIP program cost nearly US$28.5million and nearly US$10.5million the following year. It didn’t matter anyway for FMC. All work on a complete replacement for their project was terminated by 1984 with the decision being made at the time to simply modify the M109 fleet with new ammunition stowage and a longer range gun instead. The project was overall somewhat of a failure, no new vehicle was produced and a huge amount of money was spent. The opportunity for a new and more capable platform producing a new family of vehicles was lost.

Illustration of the FCM New Start Howitzer Improvement Program, showing the forward placed driver compartment connected to the rear fixed superstructure. Illustration by Yuvnashva Sharma, funded by our Patreon campaign.

Specifications required for Future Self-Propelled Artillery System

Propulsion Advanced new engine delivering at least 20 hp/t
Top speed 60 to 75kmh (road)
Operational maximum range 400-600km
Armament 155 L38 to L/50 main gun, one cupola mounted .50 cal heavy machine gun
Ammunition All current and future compatible NATO 155mm shells, modular combustible case shells as well as guided, unguided and rocket-assisted shells.
Armor Unspecified ‘improved’ armor

FMC proposal ‘DSWS New Start’

Armament 155 L45 main gun, one cupola mounted .50 cal heavy machine gun
Ammunition 50 rounds in two 25 round drums with fully automatic feed capable of firing unassisted projectiles to 23km


GAO Report AD-A141 422 M109 to M109A5 Report, March 26th 1984
Janes Armour and Artillery 1984-5
US Army Tank Automotive Command Laboratory Posture Report FY 1982, US Army
Research Development and Evaluation Army Appropriation descriptive summaries, January 1990, US Army Congressional Report
Report ARLCD-CR-81053, Demonstration Prototype Automated Ammunition and Handling System for 155mm Self-Propelled Howitzer Test Bed, December 1981, US Army ARRADCOM

Cold War US Prototypes

M-70 Main Battle Tank

USA (1962 – 1963) – MBT – None built

In 1962, the US Armor Association launched a competition for the design of a next generation of Main Battle Tanks (MBTs) to replace the M60 Gun Tank in light of advanced Soviet vehicles which were being developed. The goal was to gather ideas as to how people thought the tanks of 1965-1975 might look and left the various designers a lot of freedom in terms of armament and propulsion. Many designs were sent in from around the world but one very close to home came from a serving US soldier, David Bredemeir, based at Fort Knox, the home of the US School of Armor at the time. This design was to eschew conventional suspension, layout, and armament and produce a missile carrier capable of destroying any future Soviet threat. Named the ‘M-70’ (no connection to the MBT-70), presumably for the anticipated in-service date, this vehicle provides a semi-professional glimpse at some of the thinking of the era.

PFC David Bredemeir, the designer of the M-70. Source: Armor Magazine


The basic layout of the M-70 was a long slender tank. The engine, a “long slender gas turbine”, was positioned alongside the driver at the front. The turbine would power the front-mounted transmission.


The M-70 was not to be a conventional gun tank. Bredemeir eschewed the conventional cannon approach for his design and put the offensive capability for the tank in the hands of anti-tank guided missiles. This design choice was based upon the logic that it would be able to fire before an enemy tank could and to ensure a first-round hit each time. The result was that the tank was to carry a battery of 8 anti-tank guided missiles (ATGM) in each ‘fender’, the sponsons along each side above the tracks. As the missiles traveled slower than a conventional shell, they could be fired in the general direction of the enemy even without aiming, with this process then being picked up by means of the guidance as the vehicle stopped. There would then be time to guide the missile onto its target before the corresponding enemy tank had had time to stop, aim and fire its main gun. Another launcher was retained in a rotatable turret at the back of the vehicle and between 50 and 60 missiles could be carried. Storage was facilitated for them, as their fins were all spring-loaded to fold down. Of those 50-60 missiles, 20 were to be stored in the turret.

Various types of missiles were proposed, including smoke, chemical, heat-seeking, and even atomic rounds, guaranteeing these missiles were capable of taking on even the heaviest of enemy armor. The heat-seeking missiles also enabled this tank to counter enemy aircraft and it could track them itself too with a built-in onboard radar. A machine gun was mounted on the commander’s cupola.


The M-70 was to use a three-man crew consisting of commander, gunner, and driver, although the gunner also served as a radar operator. When the gunner was busy loading the missile tube, the commander could take over his duties. Of the three crew, the driver would be at the front, leaving the commander and gunner in the turret at the back. The gunner, situated on the left, would be able to operate the missile launch-tube centrally as well as the radar, and when he was otherwise engaged, the commander could take on the gunner’s duties. The commander sat in the turret on the right-hand side and had his own cupola with a machine gun.

Bredemeir’s M-70 tank design relied upon its low profile for protection and missiles for its firepower. Source: Armor Magazine


Being lower than the M60 Gun Tank would give the M-70 a higher chance of survival on the battlefield, as it would be less likely to be hit. It also meant a lighter and more maneuverable tank but it still needed armor. The result was that the M-70 was to be made out of aluminum. This, in turn, would keep the overall weight down to 20 to 25 tons (18.14 to 22.70 tonnes)


The suspension for the M-70 was a ‘two-stage’ system, with the tracks and road wheels divided in half and connected together via a single leaf-spring holding them to a beam that ran the full length along each side. Each of those beams was then connected by a pivot arm at the front and back of the tank to a connector on the opposite side. The hull itself was not mounted directly to these track units but held via coil springs from each end of the beam instead. Only the driving axles for the sprockets would directly link the hull to the tracks units. This double-spring system was felt to provide maximum comfort. Small road wheels would spread the weight of the tank along its track and also serve to keep the overall height of the vehicle down.


During the 1960s, faced with the enormous growth in power of anti-tank guided missiles, many were speculating it meant the end of the conventional tank. Likewise, the potential of ATGMs outstripped the anti-armor potential for large caliber guns with the advantage of being significantly smaller and lighter. Many countries would consider and even develop ATGM-based tanks during the Cold War, but just like the US Army, they were constrained by budgets, thinking, and a conservative attitude of trying to keep developments relatively simple. The M-70 offered superior firepower to the M60 in a much smaller vehicle but in 1962, this gun-launched missile concept was already underway on the M551 Sheridan. It was never to work satisfactorily for that tank and the M-70 offered little to warrant development.

Illustration of the M-70 Main Battle Tank by Andrei ‘Octo10’ Kirushkin, funded by our Patreon Campaign


Armour Magazine January-February 1963

M-70 Specifications

Total weight, battle ready 20 to 25 tons (18.14 to 22.70 tonnes)
Crew 3 (Commander/Gunner, Gunner/Radar Operator, Driver)
Propulsion Petrol turbine (fuel tanks under turret at the back)
Armament ATGM launchers, 50-60 shells (incl. 20 in turret)
Cold War US Prototypes

Lockheed/Forsyth Tank

U.S.A. (1962-67)
None Built

Post World War 2, the United States had a glut of tanks including large stocks of M4 Shermans and new designs such as the M26 Pershing. There was, as a result, little impetus for new vehicles, even though design work, if anything, increased apace at this time.

Throughout the 1950’s, US tank designers were looking at every aspect of the problems of tank technology, from armor to propulsion and armament. Whereas a lot of development had made great strides during this time in other areas, armor was still fundamentally based upon large steel castings. Various ideas though had been tried, including compositions with glass in armor cavities and even work on bar armor to defeat incoming projectiles and the increasingly common HEAT-type warheads.

By the early 1960s though, even with a new generation of Main Battle Tanks (MBTs) at hand, the US was short of a light modern tank that was air-transportable, amphibious, well-armed, and well protected. Obviously, this is a holy grail of tank design, light-enough weight to be air-transportable but with enough armor protection to be useful in direct battle rather than just scouting or skirmish roles. The tank which was to become the M551 Sheridan was in development but this was not the only possible light tank in development at the time. Another design from the Forsyth brothers was also being planned, and this vehicle was a technological step well ahead of anything the Sheridan offered. The first glimpse of this vehicle came in a competition held by the US Armor Association in 1962, with an entry deadline of August that year.

The model from Robert and John Forsyth, which won the US Armor Association tank design competition in 1962. Source: Hunnicutt

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The first thing to address in looking at this design are the designers, John and Robert Forsyth. John and Robert were brothers who were engineers living in California and worked at the Vehicle Systems Development Division of the Lockheed Aircraft Corporation in California. Over the years, they designed and developed various transportation-related vehicles, amongst other things. These included a large bus for cars to travel in and various forms of unusual traction machines including a tri-wheeled amphibious vehicle and articulated machines.

The Forsyth brothers. Source: Armor Magazine

Whether their tank design was already being considered prior to the Armor competition of 1962 is not clear, but it was certainly submitted, meaning it must have been ready before the end of August 1962.

The Need For a Light Tank

Despite a multitude of light tank designs considered during various conferences during the 1950s, it was not until January 1959 that work had begun in earnest of a new light combat vehicle under the designation AR/AAV (Armored Reconnaissance/Airborne Assault Vehicle). The specifications demanded of that design were presented in July 1959 by Ordnance Tank Automotive Command (OTAC). That vehicle was going to have to replace the existing stock of M41 light tanks, the M56 self-propelled gun and supplement/work alongside the existing main battle tanks and armored personnel carriers in service.

To meet this demand, a pilot vehicle was prepared by Aircraft Armaments Incorporated (AAI) with a 3-man crew tank in the 10-ton (9.1 tonne) class. Another company, Cadillac, designed a vehicle with a four-man crew and a little heavier. Neither of those vehicles though, as obvious by the incredibly low weight, had any reasonable protection outside of against small arms. Even so, the Cadillac proposal, although selected for development, was still woefully under-protected even outside the weight limit imposed. As a result, the allowance for weight was increased to 15 tons (13.6 tonnes) and was designated AR/AAV XM551, the progenitor of the M551 Sheridan. What that design sacrificed in height and size it made up for in armament, with a 152 mm main gun capable of firing a large HEAT (High Explosive Anti Tank) round as well as the Shillelagh missile with a HEAT warhead. Both of those weapons were capable of taking on even the heaviest contemporary Soviet armor and also provide fire support for airborne troops. Other weapons under consideration at the time were a conventional 76 mm, 90 mm, 105 mm, and even 152 mm guns, ENTAC (ENgin Téléguidé Anti-Char) (to supplement any conventional gun), TOW (Tube-launched, Optically-tracked, Wire-guided), or POLCAT missiles.

The first pilot XM551s were delivered in June 1962 for testing, with more pilots following in 1963, 1964, and 1965. Despite teething problems, the design was authorized for production and contracts issued in April 1965. The M551 went on to provide decades of service for the US military in various conflicts but it never really lived up to expectations. The armor was always inadequate and the firepower from the gun/missile system never really worked well.

A contemporary design though, offered some solutions to what became the flaws in the M551 Sheridan, whilst at the same time adding another layer of complexity to meet the demand to replace the old and obsolescent M41 Walker-Bulldog and M56 Scorpion vehicles in service. Providing a main battle tank class vehicle at a significantly reduced weight, this design was supposed to add mobility as it could go places a conventional tank, light or otherwise could not go.

Basic Layout

Having won the tank design competition with their design at the end of 1962, the Forsyth brothers and Lockheed Aircraft Corporation were anxious to secure and market the idea. The result was an embodiment in the patent application filled in January 1963, but there was nothing in that application other than the layout.

What it showed was a small tank with 5 road wheels on each side, topped with a low-profile rounded turret. Inside that turret can be seen one large caliber gun and a smaller secondary armament. Most striking in that design though is what is behind the tank, a trailer. Not just a trailer in fact, but another tracked hull, with 5 road wheels but where the armored body is taller, reaching nearly the height of the turret of the preceding vehicle. The two sections connected together through an articulated joint. The details of the articulated design would be made clear in a following application filed in July that year.

The basic design of Forsyth and Forsyth’s tank concept for Lockheed, as shown in US Patent 196779 of January 1963, illustrates a novel articulated vehicle.

The articulation was carried out by means of an assembly consisting of two rungs, the outer of which has two arms connected to the hull of one vehicle which controlled the pitch and roll between the two sections. The inner ring was mounted by means of an internally rotating ‘shoe’ to a yoke which was fixed rigidly to the other vehicle. In this way, the coupling allowed for a controlled degree of rotation between the two sections as well as movement sideways (as encountered when steering) and vertically (as encountered when climbing or descending).

The coupling between the two sections. Source US Patent 3215219
The whole construction was simple, just two fabricated sections forming a top and a bottom half of the hull fastened together. US Patent 3351374


The armor in the 1962 Armor competition was described as a steel and aluminum alloy with a maximum thickness of 76 mm to 150 mm (3 to 6 inches). This was clearly subject for more thought and the focus of the design submitted for patent in July 1963 was the armor. Instead of relying on a homogenous steel plate that was face hardened and was heavy and vulnerable to shaped charges, the Forsyth brothers envisaged a new system. This system consisted of a series of layers, a first and second layer of rigid armor spaced apart from each other which the cavity between them filled with a multitude of different armor panels, which were themselves held apart by a filler material proposed to be cellular or a foam-type material. This armor-system extended across the entirety of the front of the tank, covering the glacis and lower hull, but also along the full length of the upper hull side sponsons over the tracks. The lower hull, in order to save bulk, was just the single-thickness stiff section. Likewise, the roof was a single thickness of metal as was the rear.

Distribution of armor per US Patent 3351374. The armor is concentrated on the front and upper sides, where enemy fire is most likely to be received. This is repeated on the following unit for the tank as well. Note that in this drawing the tank has only 4 wheels.

The panels inside the armor cavities were suggested as being made from a variety of possible materials, including glass-fiber or metal fabric laminated together, coated with flexible epoxy-urethane resin. Other epoxy resins, polyurethane and plastics could also be substituted. The filler material between those panels served to hold them apart and offer rigidity and was to consist of polyurethane resin too. The difference between this resin filler and the other resin used was that this filler-resin was also to contain cyclohexylstearate or dimer acid, and a lead, cadmium, or boron compound (i.e. lead oxide, cadmium oxide, boric oxide) as protection against neutron radiation. In other areas where this filler did not need to be used throughout the cavity, it was to be substituted with foam, as this was a good thermal insulator and provided buoyancy.

As an aside, Forsyth and Forsyth also considered that this armor was suitable for consideration on ships and submarines. The projected weight for both parts was just 21 to 22 tons (19.00 to 19.96 tonnes) for the steel/aluminum armor version and fro, 24 to 32 tons (21.77 to 29.03 tonnes) for the composite armored version, depending on the exact composition. The composite armor-option was a significant improvement over the original steel and aluminum option and provided the design with substantially more protection than that of the Sheridan against both kinetic energy and shaped charge munitions.

The armor arrangement as outlined for the tank but used for a submarine (left) and boat (right). Source: US Patent 3351374


As shown in the patents, there were two weapons mounted on the tank, and later, a third weapon mounted on the following unit. The tank’s weapons consisted of a single large-caliber gun of an undisclosed size in the patent, although it bears a close resemblance to a gun like that on the M551, the 152 mm. Bearing in mind the requirements from the army, as stated before, included 76 mm, 90 mm, 105 mm, and even 152 mm guns, ENTAC (to supplement a conventional gun), TOW, or POLCAT missiles, one of those would have been chosen and what is shown is too large for either the 76 mm or 90 mm guns. In their competition entry, the Forsyth brothers were clear that they planned a 155 mm gun as the primary weapon, capable of firing rocket-assisted projectiles. The secondary armament, as it appears in the patents, appears to be a cannon, but is only described as the secondary armament for anti-personnel purposes. No mention is made of the third gun at the back, which could be assumed to be a machine gun. In their competition entry, the secondary gun is confirmed as a 20 mm Hispano-Suiza HSS 820 automatic cannon in the front vehicle and the small turret at the back is confirmed to take a 7.62 mm Vulcan-type machine gun.

Side view of the complete design showing the additional rear mini-turret. Source: US Patent 3215219
Front ¾ view of the design showing the two turret hatches and the armament. Source: US Patent 3351374


The M551 was to have a crew of four, as the use of a three-man turret was seen as having value in combat. The design from Lockheed though went away from that idea and back to a three-man crew with just two in the turret. The two men, commander/gunner, and gunner/loader were seated on the left and right, respectively. The driver, lying supine to reduce the overall height of the vehicle, was located on the front left of the hull, with the engine to his right. Although being self-powered and able to operate independently of the following unit, the unit behind contained more men. Four more men in the back acted as a small armored personnel carrier team attached to the main tank and accessed it via a door at the back. They could egress the vehicle to fight or carry out tasks dismounted, and in the final patent publication’s drawings, this following unit had gained a small turret with a gun so as to provide additional firepower. As part of a platoon of such tanks, the men in the rear sections would end up being a unit 15 to 40 strong without the need for additional APC’s to follow.

Layout of automotive elements and crew from US Patent 3215219

Automotive and Suspension

The engine for this first section of the vehicle was located in the front right of the hull and centrally in the second section. It is described only as “a piston unit [conventional petrol or diesel engine] or a gas turbine” which drove an A.C. electrical generator. That electrical power was then delivered to the back of the tank (in the case of the lead unit) where traction units drove the sprockets. On the trailing unit, the same system was used except that the electrical traction units and sprockets were at the front. Steering was electro-hydraulic, able to adjust power to the tracks on each side of each section to vary the turning moment applied but also allowed for steering forces to be applied through the coupling hydraulically.

Suspension for both sections was by means of a flat band track mounted on long-pitch, large-diameter road wheels, although the designers did suggest that if tracks were not suitable that a multi-axle wheel system could be substituted instead.

Forsyth’s articulated tank concept model. Source: Armor Magazine.

One advantage of this arrangement of power with two independently powered sections connected by an articulated joint was flexibility. Either vehicle could operate completely independently or together. If one unit failed or broke, the other could push or pull it along, reducing the chances of the design becoming stuck or crippled. Further though, the independence of the electrical transmission provided additional benefits. The sections could be split and have power sent from one half to the other via cable even though they are not attached. This means that the vehicle did not have to float across waterways but instead could submerge and receive power from another tank on the bank. Once it got to the other side, it started up and sent power to the following tank in a system very similar to that adopted for the German Maus in WW2. It made loading onto aircraft for transport easier too.

Working alone or in pairs, the design was flexible enough to allow power to be sent from one vehicle or pair of vehicles to another so it can travel submerged. Source: US Patent 3215219
At just 21 to 22 tons (19.00 to 19.96 tonnes) (steel/aluminum armor version) to 24 to 32 tons (21.77 to 29.03 tonnes) (composite armored version) in total, the vehicle was air-portable and was able to split in half to easily self-load into an aircraft. Source: US Patent 3215219


The design from Messrs. Forsyth and Lockheed was, in many ways, ahead of its time. During the early 1960s, the concept of using composite armor was still new thinking. There were, however, serious problems to overcome. The coupling concept was not new, ideas for coupled tanks date back to 1915, and although the coupling in 1962/3 was undoubtedly better designed than the ones from 1915, it was still not a perfected technology. Lighter than the M551, this design offered increased protection and capability and the potential for improved firepower, but it was unlikely to have ever received serious consideration. By the time the first patent was filed, the US Army’s eyes were on the XM551 project, which offered a lot of what they wanted without having to use new and as of yet unproven technologies. The potential offered by this design was thus lost, it received no orders and was never built. Coupled vehicles would continue to be examined by a variety of countries for a variety of purposes, as would coupled tanks and electric drive and composite hulls. This design, however, seems to be the first design to combine all of these elements in one.

Cross-sectional view of Forsyth’s couple tank concept. Source: Armor Magazine

The tracked version of the Lockheed/Forsyth Tank

The wheeled version of the Lockheed/Forsyth Tank

These illustrations were produced by Andrei Kirushkin, funded by our Patreon campaign.


Dimensions 1.83 m (72”) high
Mass 21 – 22 tons (19.00 – 19.95 tonnes) (aluminium/steel armor version) up to 24 and 32 tons (21.77 to 29.03 tonnes) (composite armor version) depending on armor selected.
Crew 3 (Driver, Commander/Gunner, Gunner/Loader) + 4
Propulsion Petrol/diesel piston engine / gas turbine, with electric transmission
Range 322 to 483 km (200 – 300 miles)
Armament 155 mm main gun firing rocket-assisted projectiles (24 rounds), 20 mm Hispano-Suiza HSS 820 automatic cannon (200 rounds), 7.62 mm Vulcan-type machine gun (2500 rounds)
Armor Steel/aluminium alloy mix 76 to 150 mm thick later changed to composite-type 76 to 150 mm thick


Armor Magazine. (July-August 1962). Tank Design Contest.
Armor Magazine. (January-February 1963). The Winning Tank Designs.
US Patent 196779 ‘ Tank Unit’, field 28th January 1963, granted 5th November 1963
US Patent 3351374 ‘Armor Construction’, filed 1st July 1963, granted 7th November 1967
US Patent 3215219 ‘Articulated Vehicle’, filed 22nd July 1963, granted 2nd November 1965
Hunnicutt, R. (1995). Sheridan: A History of the American Light Tank. Presidio Press, California
Hunnicutt, R. (1990). Abrams: A History of the American Main Battle Tank. Presidio Press, USA

Cold War US Prototypes

120mm Gun Tank M1E1 Abrams

USA (1979 – 1985)
Main Battle Tank – 14 Built

Following the failure of the MBT-70/KPz-70 joint project, the need for a new tank for West Germany and the USA (amongst others) had not gone away. One of the main points of value for those projects was the interchangeability of parts and, even after the joint project had been terminated, the desire for more interchangeability continued. In 1974, a memorandum of understanding (MOU) was signed between the USA and West Germany in which the USA would test the German Leopard 2 with the goal of standardizing as much as possible between the two tank programs. This was followed, in 1976, by an addendum to that 1974 MOU in which the components to be standardized were identified.

It was here that the decision was made to select the German 120 mm smoothbore gun for both tanks, although it was apparent that the first series of M1 Abrams entering production would have to be armed with the M68 105 mm gun (an American-made copy of the British L7 rifled gun) instead, as the 120 mm was not ready. In 1976, the project to up gun the M1 with this 120 mm smoothbore gun was already set out, naming this first variant as the M1E1 (E = official Experimental version).

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Experimental Model Number 1

Not only was this first experimental modification of the M1 Abrams going to mount and test the German 120 mm smoothbore, but there were other plans too. Every vehicle has a certain amount of ‘growth potential’ – the amount which it can reasonably be expected to take and accept changes, modifications, adaptations etc. to meet future threats and stay up to date. The same is also true with the M1. Although M1E1 plans had been started in 1976, it was not until February 1979 that this growth potential investigation began with the M1E1 Block Improvement Program starting. This four-point plan was to investigate armor improvements to the front of the turret, a hybrid NBC system incorporating a micro-climate crew cooling system, weight reduction, and upgrades to the suspension and final drives. It was debated about adding an independent thermal imaging sight (CITV – Commander’s Independent Thermal Imager) for the commander for the M1E1.

M1E1 turret showing what appears to be a mockup fitting of the CITV system. Whilst this was not adopted, a small hatch was made on the roof of the M1A1 so it could be added later. Source: US DoD

Adding a CITV would have given the M1E1 commander the ability to adopt an independent hunter-killer mode, able to hunt for targets even whilst a target was already being engaged by the gunner. Due to the expense involved with thermal imagers, this idea was dropped to save money. A circular port was planned to be added to the roof though so that a thermal imager could be added at a later date. The rest of the work was approved in May 1982 for work to proceed with the first M1E1 expected in 1985. The first 2 of the 14 M1E1s were delivered for testing in March 1981, ahead of the actual implementation date of the product improvement program.

“The M1 is now in procurement, with a small amount of development and testing yet to be accomplished. We have procured over 780 tanks as of the end of 1982. Fielding began in 1981 and will continue for a decade or more. The 120mm-gun-equipped M1E1 is now in development. The first production model M1E1 will be produced in 1985. In addition, the Army is pursuing a product development program to assure the M1 maintains its competitive position through the 1980s and beyond”

– US Dept. of the Army, 1983

M1E1 first pilot model built in March 1981. Note the wide ring fitted around the rear sprocket in an effort to prevent it from throwing tracks. Source: Hunnicutt


Upgrades made to the basic M1 for the new M1E1 were identified as Blocks. Block I was to consist of the 120 mm gun and NBC system. Block II, which included further improvements in survivability and fire control, would not be done until the M1A1 was in service.

Upgrades – Turret M1 to M1E1

Even before production of the M1 was fully underway, there were concerns over the choice of armament, as the United States’ major NATO allies, Great Britain and Germany, were already fielding 120 mm guns (rifled and smoothbore, respectively) on their new main battle tanks. The brand new US tank was, therefore, going to end up being fielded with the cheap and effective 105 mm and was thus going to be under-armed. More to the point though, the M1 was not going to meet the requirements of the interoperability agreement with Germany which had called for the use of the 120 mm German smoothbore. Knowing that this gun would be fitted eventually, the turret was at least designed with this gun in mind. As the turret was going to have to be upgraded anyway with better armor, it was decided to incorporate some other, smaller changes too. Firstly, the amount of stowage was improved with an additional stowage box added to the turret side. The second stowage improvement was the addition of a full turret bustle rack on the back in which items could be stowed. This replaced the original canvas strap system which was slow and cumbersome to use. The final change to the turret, other than the gun and armor, was the wind sensor. On the M1 turret, the wind sensor, in the middle of the turret at the back, could be folded down. It was now fixed in place on the M1E1 turret.

Visual changes between the M1 and M1E1 turrets. Note that this graphic shows a 3-section ammo blow-off panel on the M1 rather than the original 4-piece panel. Source: Mesko

Armament M1 to M1E1

The M68A1 105 mm gun was cheap and reliable and the M1 carrying that gun could carry 55 rounds of ammunition between the hull and turret compartments. Upgrading to a larger gun, as had been considered, would reduce the amount of ammunition which could be carried. With Great Britain and Germany fielding powerful 120 mm guns on their new main battle tanks (Challenger and Leopard II, respectively), this left the US in the position of not just using a less powerful gun but having no cross-compatibility in terms of ammunition with either NATO partner.

The German 120 mm smoothbore, made by Rheinmetall, had suffered from some development issues and was not delivered for testing to Aberdeen Proving Grounds until the first half of 1980, where it was designated as the XM256. Plans for an American-designed breech for the gun were still on the table, as it was felt that the German breech was too complex and the source of some additional problems. Those new-breech plans were abandoned as unnecessary and the German breech would be used instead, as the problems were steadily overcome and simplified. Following successful trials of the XM256 in 1980, the first 14 M1s were retrofitted with this gun replacing their 105 mm rifled guns. As such, these vehicles were designed M1E1 to test the new gun mount and other improvements. When the XM256 120 mm smoothbore gun was accepted for service for the M1A1, it was redesignated as the M256.

The early problems with the German 120 mm Smoothbore made by Rheinmetall had led to the idea that it might not be ready at all. As a result, a secondary armament upgrade was considered, using an enhanced 105 mm gun in March 1983. This would have used a gun tube 1.5 metres longer than the tube of the M68A1 105 mm gun, and which could tolerate a much higher internal pressure. When the problems with the 120 mm XM256 were resolved, there was no need for this improved 105 mm gun and the plan for it was dropped for both the M1E1 and IPM1. The XM256 was accepted for use in December 1984, although into FY1985 there was still a validation trial of the improved 105 mm gun on an Abrams listed briefly as M1E2. Regardless of this 105 mm gun though the development life of the 105 mm rifled gun was essentially over, the new gun was clearly going to be the 120 mm smoothbore.

As the turret had been designed from the beginning for this larger gun, mounting it in the turret was not a big problem, although the amount of ammunition would be reduced to just 44 rounds.

The German 120 mm smoothbore adopted for trials as the XM256. This gun is using the German breech which was initially felt to be too complex. The idea of a simpler American-designed breech was dropped and this gun was adopted later as the M256. Source: Hunnicutt

These 44 rounds were planned to be divided amongst the turret bustle (34) and hull rear (6), with an additional 4 (‘ready rounds’) in an armored box on the turret floor – a hangover from the M1. With the size of these unitary 120 mm cartridges though, those extra 4 were eliminated, leaving just 40 rounds for the tank. The hull stowage (6 rounds) was retained in the rear of the hull (accessed by a small door in the bottom right of the turret basket), albeit with a new size rack for the larger rounds and an improved hatch on the armored door. In the turret, the ammunition rack also had to be changed for the new, larger rounds with the shells divided into three sections in the bustle. Each of the outer sections could hold 9 rounds and the center section, divided from the other two alongside it by a bulkhead, held the main stock of rounds, with 16 more. The original blow-off panels above this ammunition store consisted of four rectangular sections on the first M1s, changed to a three-section panel, with two narrow sections surrounding a slightly wider center panel, on the M1E1. When the M1E1 was adopted as the M1A1, this 3-section panel was dropped and replaced with a simpler 2-section blow-off panel instead.

Elevated front and rear view of the pilot model M1E1, providing an excellent view of the changes to the blow-off panels and stowage on the turret. Note that, at this time, the circular panel where a thermal imager could be fitted had not yet been added. Source: Hunnicutt
Visual differences between the turret front and armament of the M1 compared to M1E1. Source: Mesko

The switch to this new, heavier and larger caliber gun also meant changes to the fire control system were needed. A new gearbox for elevation and depression of the gun, software upgrades and electronics were added in order to make this new gun workable. The coaxial gun needed some minor modifications, with a new mount for the ammunition box, feed and ejection chute, and a box to collect spent ammunition and links.



One consideration to upgrading mobility was to reduce weight. Simultaneously with increasing the size (and weight) of the main gun and the addition of more armor (and weight) to the turret, there was an attempt to reduce the weight of the primary construction elements of the tank. There would, in later years, be numerous ‘lightenings’ of components for the Abrams throughout its life to save a little weight here and there, but in 1985 the idea was to take the single largest and heaviest element, the hull, and make it lighter. The hull, which was of an all-steel welded construction, offered few options for lightening, so the project was switched over to the concept of making a completely new hull for the M1 out of composite materials. Those plans, therefore, formed no part of the M1E1 or the M1A1 by the time it was approved.

The other mobility upgrades were dictated by the increased weight. Improved final drives and transmission for the M1E1 would increase reliability and deal with the additional load. Further, new suspension shock absorbers were fitted to the front to increase the damping effect. Less obvious was the adoption of a slightly modified road wheel with a thinner rubber tyre and wider cross-section (132 mm to 145 mm).


Somewhat surprisingly for a modern main battle tank designed to fight a modern war in Europe, which was highly likely to involve the use of nuclear, chemical, or biological weapons, the M1 Abrams had no NBC filtration system. The crew, instead, would have to wear their personal protective equipment, such as gloves and respirators, whilst fighting in the tank – an enormous encumbrance for them which would reduce their fighting ability. A key goal of the M1E1, therefore, was the addition of an NBC system which would create an overpressure within the tank to keep out contaminants and poisons, with filters being used to scrub the air being drawn in.

Port for the NBC system trialed on the M1E1, as it appears on the left side of the hull. Note: the turret is turned to the rear in the photo. Source: Hunnicutt

One M1E1 was modified for these purposes and for testing at the Natick Laboratories in Maryland. Fitted with the M43A1 detector and AN/VDR-2 radiac (mounted on the turret floor), even very low levels of chemical or nuclear agents could be detected. The M13 filtered air system, which delivered air directly to the crew’s face masks as was used on the original M1, was retained as a backup system.

The system was to use an all-vehicle air conditioning system (macroclimate) instead of the alternative of using individual crew cooling systems (microclimate). This macro system would keep the crew comfortable inside the tank as well as filter the air coming in. However, this cooling system proved to be bulky, as it had to filter, cool, and circulate the air around the tank. The crews who took part in the testing (two crews from 2nd Battalion 6th Cavalry) were positive about the need for the new air system, but in light of the bulk and expense involved, it was decided to abandon the tank-climate system and revert to the earlier idea of a microclimate individual crew-cooling vest instead.


Other minor changes incorporated at the same time as the others were a slight rearrangement of internal stowage, the addition of a dual air heater, a new hull electrical network box, and new electrical harnesses. Minor changes continued in the turret, with a rerouting of the electrical harnesses and alterations to the commander’s seat and a new knee guard for the gunner.

With a new and improved M1 underway for the Army (which would enter service as the M1A1), it was also a potential replacement tank for the United States Marine Corps (USMC), who were still using the venerable M60 series tanks. To meet the needs of the USMC, the M1A1 would have to be able to ford deep water, up to 2 metres deep. This meant that a deep water wading kit had to be designed, fitted, and trialed on the M1E1. These trails were carried out in October 1984.

Design for a deep water wading kit for a USMC version of the M1A1 which was evaluated on the M1E1. Note: after leaving the water the turret would be traversed and knock off the towers over the air inlet and exhaust. Source: Hunnicutt


By 1984, the M1E1 was undergoing Development Test II and Operational Test II, making sure it met the requirements of the Army. The M1E1 was expected to enter production in 1985, when it would be renamed from M1E1 to M1A1. At the same time, the Army was also pursuing a program of continuing product improvement with an eye to changes and development of the M1 Abrams as a platform to meet future threats.

Montage image of M1E1 with deep wading kit fitted during trials in October 1984. Source: Hunnicutt

Before these trials were over, the Improved Performance version of the M1, known as the M1IP, was authorised and would provide a stop-gap whilst the new M1A1 entered production. The IPM1 though did not adopt the German 120 mm gun or the NBC suite trialed on the M1E1.

A sequence of shots showing an M1E1 from above during tropical trials in Panama. Source: US National Archives
M1E1 Abrams with turret traversed to the rear. Source: Mesko
One of the 14 M1E1s as fitted with the XM256 120 mm smoothbore gun and other improvements, including substantial slabs of steel welded to the hull and turret front to mock up the weight of a new armor package. Source: Mesko
Pictured in 1984, this M1E1 is being evaluated. The additional plating on the front of the turret is readily apparent. Source: Zaloga

Armor M1 to M1E1

The most obvious changes to the M1E1 from the M1 are the new, larger gun and the large slabs of steel welded to the front of the turret. It is important to note that although these were large slabs of steel welded to the front that they were not actually additional armor in of themselves. They were added simply as weight to simulate the additional weight of the new composite armor modules being added behind the original ‘skin’ on the front of the turret. The structure and arrangement of this armor is known, although the exact composition of those special armor arrays is not. The composition of the armor is still classified, although it is known that, at this time, the Abrams was not using Depleted Uranium (DU) within the armor. This was not added until later. Nonetheless, the ‘special’ armor provided significantly better protection (weight for weight) than conventional cast-steel or rolled steel armor, making use of composite materials and spacing within the arrays. This was particularly effective against High Explosive Anti-Tank (HEAT) ammunition and less so against Kinetic energy ammunition (APFSDS – Armor Piercing Fin Stabilised Discarding Sabot).

A careful look at the front of the turret of one of the first M1E1s being evaluated clearly shows that these slabs (eventually three-thick) were added incrementally to the design during evaluation. With all of the modifications to the turret and hull, the new gun, and the additional armor, the M1E1 weighed 62 tonnes. The M1 would get even heavier throughout its life in service, far exceeding the original goals of the 1970s.

This early M1E1 during testing provides a rare view of the additional plating on both sides of the turret face. Source: Hunnicutt
Two views of two of the 14 M1E1s fitted with the XM256 120 mm smoothbore gun and other improvements, including substantial slabs of steel welded to the hull and turret front to mock up the weight of a new armor package. Note that the application of welds differs for each vehicle. Source: Mesko (right) and unknown (left)


The M1E1 was a very successful trial project. Even though not all of the systems proposed or tested, such as the commander’s independent thermal sight, were adopted on the M1A1, the M1E1 marked the step into what the M1 was supposed to be in the first place – a superior tank in all aspects to the Soviet tanks it faced for the 1980’s in Western Europe. The M1 ceased production in January 1985, as new vehicles would be of the new M1A1 standard. The only aberration to the story of the M1E1 is the appearance of the IPM1, a stopgap M1 to meet the urgent need for more protection.

The M1E1 also marked the first step in what was to be a significant gain in weight for the Abrams, a trend which has continued since then, as the demand for protection has increased as the threats the tank faces change. The M1E1 is not a well-known variant of the Abrams and it never saw combat. Just 14 were made for testing and none are known to survive.

Illustration of the 120mm Gun Tank M1E1. Produced by Tank Encyclopedia’s own David Bocquelet.


Dimensions (L-W-H) 9.83 x 3.65 x 2.89 meters
113.6” h (1984 memo)
311.68” long (1984 memo) – L W H all identical to M1 hull
143.8: wide (1984 memo)
Total weight, battle-ready 62,000 kg (62.9 US tons -1984 statement) 63 tons – 1984 memo
Crew 4 (Commander, Gunner, Loader, Driver)
Propulsion Avco-Lycoming Turbine (Petrol) 1,500 hp (1,119 kW)
Maximum speed 41.5 mph (67 km/h) governed
Suspensions High-hardness-steel torsion bars with rotary shock absorbers
Armament 120 mm XM256 smoothbore gun
12.7 mm M2HB QCB heavy machine gun
2 x 7.62 mm MAG58 general-purpose machine guns
Armor Hull: Welded steel with special armor inserts in the front. Composite side skirts.
Turret: Welded steel with special armor inserts on the front and sides
Production 14


Hunnicutt, R. (1990). Abrams – A History of the American Main Battle Tank. Presidio Press, California, USA
Mesko, J. (1989). M1 Abrams in Action Squadron/Signal Publications, USA
Janes Armour and Artillery 1985-86, Janes Information Group
Lucas, W., Rhoades, R. (2004). Lessons from Army System Developments Vol. II – Case Studies. UAH RI Report 2004-1
Organic Composite Applications for the M1/M1A. (1986). Allen Pivett. General Dynamics Land Systems, Michigan.
US Army Research Institute of Environmental Medicine. (1991). A Physiological Evaluation of a Prototype Air-Vest Microclimate Cooling system. United States Army Medical Research and Development Command, Natick, Maryland, USA
US Dept. of the Army. (1983). 1983 Weapon Systems. US Dept. of the Army, Washington D.C., USA
US Dept. of the Army. (1984). 1984 Weapon Systems. US Dept. of the Army, Washington D.C., USA
US Dept. of the Army. (1985). 1985 Weapon Systems. US Dept. of the Army, Washington D.C., USA
US Dept. of the Army. (1984). Army Modernization Information Memorandum (AMIM) Vol. 1. US Dept. of the Army, Washington D.C., USA
Zaloga, S. (2018). M1A2 Abrams Main Battle Tank, Osprey Publishing, England

Cold War US Prototypes

LVTP-77 Cybernetically Coupled Amphibian & Articulated LVT

U.S.A. (1966)
Research Vehicle – 1 Built

Ideas about coupling vehicles together and of an articulated body for fighting vehicles are as old as tanks themselves. Coupling two vehicles together offers the designer some significant benefits for mobility and design for a variety of roles, one of which was with amphibian tanks.

Unladen LVTP-5 in the water showing her trim line, later a coupled LVTP-5 was attempted. Source: Dyck and Ehrlich

Amphibian tanks, which can operate on land or in water, have unique challenges to overcome. They have to be buoyant enough to float and yet armored sufficiently to protect the troops and then they still have to deal with the difficult transition from water to land. A coupled or articulated vehicle has the advantage of being long enough to straddle this boundary between water and land and potentially, of being able to cross bigger obstacles than a single-hulled vehicle.

With that in mind, the US Navy started work as early as 1966 studying the effects, benefits, and costs associated with coupling amphibian vehicles together. That study followed work between 1956 and 1958 focusing solely on improving water speeds for amphibian vehicles although due to time and financial constraints it was limited only to wheeled vehicles. Although those tests were inconclusive the one bright light from them was the testing of the ‘Sea-Serpent’ (not to be confused with the amphibian flame-thrower vehicle of the same name). Sea-Serpent was the name given to a multi-vehicle amphibian train of up to eight vehicles coupled together which managed a combined speed double that of one of the single vehicles.

Artwork for the ‘Sea-Serpent’ a series on coupled amphibians and the simple pin connection between the trucks. Source: Nuttall and Kamm.

Building on this finding for such a novel vehicle, in 1966, Davidson Laboratory (DL) looked at the problem from the point of view of tracked amphibians and concluded that it was feasible to couple together up to five LVTP-5s and that this ‘amphibian-train’ had only twice the water friction of a single vehicle. As such, this 5 vehicle train could increase speed by up to 50% in the water alone. Furthermore, the transition zone was traversed more easily by this 5 vehicle train, as were obstacles. Such an increase in mobility constituted a significant military advantage and clearly this success meant there would be further work in this area to expand on this.

The DL experiments did not use actual LVTP-5 but instead accurately shaped and weighed models in a test tank with them connected together by means of simple pin connections at the height of the center-of-gravity (CoG) of the vehicles.

One problem identified during these 1966 tests was that the increased vehicle speed produced an increased sized bow-wave with a consequent increased risk of swamping of the lead vehicle (as there is no bow wave for any of the following vehicles). To counter this, a freeboard shield would be required to be fitted to the lead vehicle of any LVTP-5 train regardless of length (Tests conducted during the 1970’s with coupled M113s also showed this additional freeboard shielding used). Additionally, as a larger freeboard shield was required for any length of LVTP-5 train, it was also found this had the side benefit of itself reducing drag in the water by 5%. In calm water, it required zero freeboard at 7.1 mph (11.4 km/h) and 12 inches (305 mm) at 7.6 mph (12.2 km/h). At 8.3 mph (13.4 km/h) however, she would need 20 inches (508 mm) of freeboard – the same amount as required unladen at 10 mph (16.1 km/h).

Schematics of the 1/12 scale model used for the coupled LVTP5 trials showing the size of the additional freeboard protection required. Source: Dyck and Ehrlich


Vehicles used in an amphibian train had to be carefully positioned to reduce drag and the ideal gap between vehicles was found to be 1 foot (300 mm) compared to the original 6 feet (1.8m). This close-coupling reduced drag in the water by 15% and thereafter all testing was done with little or no gap between vehicles. Even with the drag reductions and freeboard changes though, the entire train was still effectively limited to a safe speed of 9.2 mph (14.8 km/h) in the water to provide a margin of safety for rough water.

Additionally for rough water the coupling, DL recommended that it “must be capable of absorbing some degree of shock, if wave or surf operation is contemplated”. They had found that, at a pitch angle of more than 25 degrees, their train broke apart. Obviously, in a real-world situation, this would have proven extremely hazardous.

The 1966 experiments ended with strong recommendations to pursue this modeling to the prototype stage with a train made from real LVTP-5 tested with a view to developing an effective type of coupling and box shields. It is not known, however, if any LVTP-5’s were ever modified in tested in this coupled configuration despite the potential benefits.

M113 CCRV project during snow trials. The vehicle could be controlled from either front or rear vehicle. Source: TACOM/TARDEC

A Project Reborn

The work in 1966 had shown the potential for coupling for amphibians but also highlighted the lack of knowledge in coupled-vehicle systems. As a result, in 1972, money was put aside by Congress for work on cybernetically coupled technologies with positive feedback controls to tray and leverage this coupling technology. The following year (1973), two M113’s were modified and coupled together to form the M226 Cybernetically Coupled Research Vehicle (CCRV). That work showed, once more, great potential. Combined, the two vehicles exhibited greater mobility off-road than an individual vehicle, particularly when it came to obstacle crossing, and used a more controlled system for the coupling compared to the rather crude pin-attachment in the 1966 experiments. This time, instead of an uncontrolled pin vulnerable to excess pitch (in the water) and excess yaw (on land or in the water), the M113 CCRV connector limited movement to a maximum articulation of +/-45 degrees and a yaw of +/-30 degrees.

Control for the system was by means of a simple joystick with positive feedback in all cases, except for pitching where the feedback caused some problems. A simple movement of the driver’s joystick would control the hydraulic arms on top of the vehicle to move the two hulls relative to each other as well as providing stiffness preventing too much pitch and yaw.

The conclusion of the trials in 1974 had proven the experiments in 1966 to be partially correct. A coupled vehicle did exhibit manoeuvrability benefits over the single hull system. Some specific recommendations and findings about the coupled-vehicle system came out of the project including the reduction of water resistance for amphibious vehicles and assisting amphibious assault vehicles in breaching defences.


Irmin Kamm, from the Stevens Institute of Technology and one of the lead authors for TACOM on cybernetically coupled vehicles had already worked on amphibian trains coming up with the Sea-Serpent back in 1969 and then, on the M113 CCRV project. He continued his work on the coupled-vehicle concept with amphibians in 1979 with an evaluation of the concept of a ‘Coupled-LVT’ (LVT – Landing Vehicle Tracked). He was clearly advocating for more work in this area as, in 1979, he concluded that study saying “the advantages [of a coupled vehicle] exceed the drawbacks, it is recommended that existing vehicles be coupled and tested to establish their operational capacity”. The end-user was being clearly identified as the US Marine Corps just like before but the requirements had changed a little. Instead of a coupling permitting +/-45 degrees and a yaw of +/-30 degrees as on the M113 CCRV, this coupled LVTP would have a maximum pitch of just +/- 30 degrees.

Instead of the A-frame drawbar connected to a ball and two hydraulic actuators, this time, the system would be simpler. That older system had to be connected manually but with a new cone-into-cone system, the vehicles could connect or detach on sea or land without having to stop and get out. Each vehicle would simply have a ‘male’ convex cone on the front and a ‘female’ concave cone on the rear, with both located at the center of gravity line. This system was much more versatile. Instead of a master-and-slave unit, as with the M113 CCRV, this time any vehicle so equipped with a coupling cone could connect to any other on sea or land adding a new level of capability to the idea.

Just as before, control over pitch and yaw was performed by either lead or following vehicle by means of a joystick (although a steering wheel was also considered in the study) and the engines would be synchronized to produce the same output. Transmission and braking was to be changed manually though.

With two LVTP-7’s coupled together in this system, the expected performance increases were impressive at a price of additional weight of controls and fittings and a reduction in the internal space in each vehicle. Another note was that the coupled vehicles presented a slightly larger target to enemy fire although from the front the area exposed would obviously be the same. Coupled together, the vehicle would also get a new name. It was to be the LVTP-77.


Articulated LVT

The name ‘LVTP-77’ appears here for the first time as it is two LVTP-7’s coupled together and rather than sum the two 7’s to make LVTP-14, akin to what was done adding together the ‘113’ part of the two M113’s which were coupled forming the M226, here they simply added a second ‘7’ to make LVTP-77. Looking at the figures for the LVTP-77, they clearly demonstrate that the coupled amphibian is more stable and faster in water, and in fact, faster on land too, with better obstacle crossing, but there was one other concept investigated by Kamm as an alternative. This was an articulated vehicle made from multiple-units comprising a single vehicle rather than two or more vehicles combining.

This articulated vehicle would have two sections of 14 feet (4.27m) and 19 feet (5.80 m) respectively fore and aft with a single 890 gross horsepower engine and weighing 54,000lbs (24.5 tonnes). The fore-section contained the engine and transmission and the rear section contained all of the crew, and an auxiliary engine.


The 1979 study had concluded that a coupled amphibian was not only possible and beneficial but also desirable, as was an articulated LVT. The recommendation going forwards was to design, install and test a suitable coupling on either a pair of LVTP-7’s or LVTPX-12 vehicles.

Coupling the LVTP’s

With the M226 CCRV, it was simple. It was just a test rig so it did not really matter if the combat capabilities, such as the troop space, were severely hampered. For the actual project with LVTP-7’s or others, the rear ramp and emergency exits had to be kept clear, as would the cargo hatch. Unlike the M226 CCRV, the coupling had to be remotely connectable and disconnectable on land or water and each vehicle had to be able to operate as either the master or the slave. For an articulated LVT, the vehicle was to be limited to 33’ (10.06 m) and had to be equipped with a rear exit ramp and top cargo hatch. The restriction of just one driver was not a problem, but the articulated vehicle was also supposed to be able to dump one part of itself and be able to operate independently on land if needs be. Hence, the reason for the auxiliary engine in the aft unit of the articulated LVT design.

There were 12 separate coupling systems suggested for the coupled LVTP, but only a single viable design for the articulated LVT. The types of connections considered were ball joint, off-center ball joint, symmetrical yaw, symmetrical yaw with independent pitch control, dependent pitch and yaw, dependent pitch and yaw with coupling frame, yaw – no roll, pitch only, turntable, trunnion mount, trunnion mount- internal coupler, and, split pitch and yaw. Only the split pitch and yaw type was suitable for both remote coupling and further development.

The articulated LVT was perhaps more promising as it did not need to concern itself with the problems of remote coupling. In keeping with articulated and coupled vehicles though, the turning radius was large, 35’ (10.7 m), over twice as big as a single LVTP-7 but substantially less than either the coupled M113CCRV or the LVTP-77.

All of the pitch and yaw controls were completely contained within the vehicle with steering by the simple means of yaw control from the driver. The front unit’s 850 ghp engine would be supplemented by a 100 hp auxiliary engine in the back providing some very limited mobility in the absence of the lead unit or if it became damaged by enemy fire. In the normal situation though, this 100 hp engine was used only for driving the pumps for moving the actuators for the coupling.

Power in the water was to be provided by water jets enclosed in the fore sections powered from the main engine. Although it would be more efficient in water-drive terms to have them in the rear section, it was a more efficient use of weight and space to have them in the front. Steering in the water was by means of water deflectors in the jets which moved in conjunction with the yaw of the vehicle for efficient steering. The articulated vehicle would only need one driver who was required to be in the rear although was ideally to be in the front section for visibility. The coupled vehicle concept, on the other hand, would require a driver in both sections to ensure smooth operation and obviously would not need to couple up remotely. In an emergency, it could decouple from the front unit by means of an explosive bolt – in this was the driver did not have to get out at all.

Having conducted various analytical work on the concepts for arrangements of the LVTP-7 and LVTPX-12 models, trials were carried out and once more confirmed the efficiency of coupling an amphibian. Unlike the coupled LVTP-5, which does not appear to have gone further than the concept stage, there was work carried out between 1979 and 1980 on the LVTP-7 project.

The Articulated LVT

The other part of the project which seems to have gained no traction was the Articulated LVT. Despite being better in many regards than the M226 and LVTP-77, simpler, no remote coupling or uncoupling, a single driver, etc., the project simply did not get anywhere yet was a fairly straightforward design. Two sections, engine at the front with the crew at the back, it could pitch through +/- 30 degrees and yaw to +/-34 degrees. Two small turrets on the aft portion contained cupolas for the commander and driver with the secondary weapon (unspecified but likely a .50 caliber machine-gun) in the commander’s turret. The troop compartment behind this was large with enough space for 6-8 Marines provided with a large rear ramp. The front section allowed the vehicle to climb obstacles the LVTP-7 could not and propel it through the water just as well as the LVTP too. An added advantage was that this fore-section would also be the first part coming out of the water to draw enemy fire but, being completely unmanned, did not matter. Instead, it actually served to provide substantial protection for the aft section and in the event of the fore section being damaged the auxiliary engine could simply move the vehicle forward and use the fore section as a large shield until it could be discarded. No armor is actually specified anywhere in the design, but it is a reasonable assumption to assign values comparable to the LVTP-7.

Drawings of the proposed Articulated LVT. Source: Kamm and Nazalwicz

Floating in the water, the fore section with the water jets tilted upwards sharply directing the water jets down whilst the main vehicle was relatively level behind it. Poking out just above the water from this fore section was another weapon, remotely operated and forming the primary weapon for the design specified only as an ‘automatic weapon’.

Drawings of the proposed Articulated LVT. Source: Kamm and Nazalwicz

Putting the LVTP-77 Concept Into Reality

Tests took place at the USMC camp, Camp Lejeune, North Carolina in 1979 and 1980 with LVTP-7 being tested firstly with three new designs of bow planes to cope with the anticipated larger bow wave. These new bow planes were 54” (1,372 mm) long, 42” (1067 mm) long, and 42” (1,067 mm) with a 6” (152.4 mm) lip. The vehicles were tested for speed at Courthouse Bay and at the Battalion Maintenance Pier followed by open water tests in the open ocean off Onslow Beach, all at Camp Lejeune, compared to an unmodified vehicle and a ‘jury-rigged’ coupling between two LVTP-7s.

Arrangements of the experimental bow planes tested on LVTP7s at Camp Lejeune 1979-1980. Source: Kamm and Nazalwicz

The results showed that the increased bow planes did not directly affect speed by reducing drag, but did reduce swamping which allowed for a small increase in speed. Regardless, however, the coupled LVTP-77 was faster by about 0.5 mph (0.8 km/h) in all conditions even without a bow plane and the method of coupling was inadequate with the vehicles too far (about 24 inches / 610 mm) apart, something known to increase drag. Had the coupling been properly constructed and fitted no doubt further improvement could have been made.

Experimental coupling tested at Camp Lejeune for two LVTP7’s. Source: Kamm and Nazalwicz
Very poor quality image showing the two LVTP-7’s coupled together during open water testing. Source: Kamm and Nazalwicz

The tests concluded that a new bow plane should be designed and made for the LVTP-7A1 to reduce the swamping experienced at even 6.5mph in calm waters and further work should be done on the coupled LVTP idea. The gap between the vehicles was going to be a problem though, the requirement for the ramp to still lower guaranteed the vehicles had to be too far apart to make complete use of the extra efficiency when in the water.

Either way, the coupled LVTP7 idea was dropped. The benefits were obvious, but simply did not outweigh some of the associated problems and the money to develop the system was not available. As a result, the whole project was terminated. It is assumed that the two LVTP-7’s modified with the coupling were simply returned to USMC service straight after the trials. The articulated LVT was even less successful. Despite being the logical solution to the coupling development, it never got past the proposal stage. The LVTP-7 was serviceable and available and budgets, seemingly, were better spent elsewhere rather than on a relatively small improvement to an existing vehicle.

Illustration of the LVTP-77 Cybernetically Coupled Amphibian produced by Tank Encyclopedia’s own David Bocquelet

Specifications (LVTP-77)

Total weight, battle ready 103,968lbs (47.2 tonnes) to 106,500lbs (48.3 tonnes)
Crew Minimum 1 (driver), ideally 2 (one in each vehicle)

Specifications (Articulated LVT)

Dimensions 33 ft x 14 ft x 19 ft (10.06m x 4.27 x 5.79 meters)
Total weight, battle ready 54,000lbs (24.5 tonnes) fore section 15,200lbs (6.9 tonnes), and aft section 38,800lbs (17.6 tonnes)
Crew Minimum 1 (driver)
Propulsion main engine LCR-V903 890hp, auxiliary engine 100hp
Armament primary automatic weapon in fore section controlled remotely, secondary weapon on commander’s turret on aft section


Cybernetically Coupled Research Vehicle. (1974). Ronald Beck and Irmin Kamm, Stevens Institute of Technology, USA
50 years of the International Society for Terrain-Vehicle Systems: Ground Vehicle Mobility, Modeling and Simulation ar TACOM-TARDEC ‘A Brief History’ (2012). Dr. Peter Kiss and Dr. Sally Shoop Editors. International Society for Terrain-Vehicle Systems, Germany
The Water Performance of Single and Coupled LVTP7’s, with and without bow plane extensions. (1980). Irmin Kamm and Jan Nazalwicz. Ship Research and Development Center, Office of Naval Research, Department of the Navy.
Drag Studies of Coupled Amphibians. (1966). R.L. Van Dyck and I. R. Ehrlich. Office of Naval Research, Department of the Navy.
Department of Defense Appropriations for Fiscal Year 1973. (1973). United States Congress Appropriations Committee
Analysis of Obstacle Negotiation by Articulated Tracked Vehicles: The State of the Art. (1981). Peter Brady. Naval ship Research and Development Center, Office of Naval Research
High Speed Wheeled Amphibian: A Concept Study. (1969). C. J. Nuttall and Irmin Kamm. Davidson Laboratory, Stevens Institute of Technology, USA
An Evaluation of the Coupled LVT Concept. (1979). Irmin Kamm, Peter Brown, and Peter Brady. David Taylor Naval Ship Research and Development Center, Stevens Institute of Technology, USA

Cold War US Prototypes

Ridlon’s Main Battle Tank

U.S.A. (1962-1963)
Main Battle Tank – None built

By 1962, the 105 mm Gun Tank M60 was still a new tank in service with the US Army but, just like any current system, was already being considered for future replacement, redevelopment, and upgrading. The latest generation of Soviet tanks were well armed and armored, and much smaller than their American counterparts. A new tank would be needed to deal with this increasingly dangerous threat. During the height of the Cold War in 1962, the Armor Association of the United States Army held an open competition for the design of a new tank. Of the designs submitted, some were clearly better thought-out and practical in terms of production, cost, and combat effectiveness than others.

Nonetheless, the competition formed part of one means by which the US Army could assess new and novel ideas for the potential next generation of tanks. One such tank, perhaps the most outlandish of the top four finishers, came from the fertile mind of Everett Philip Ridlon of Hibbing, Minnesota. Ridlon, an electrical engineer by trade. He submitted a quad-track tank with a crewless turret propelled by a hybrid-drive system based on the M60.

Everett Ridlon 26/7/1934 – 9/7/2011. The designer of the tank. Source: Armor Magazine


Probably the most obvious thing about Ridlon’s design is the suspension. Six wheels on each side divided into groups of three with a strong angling at the front and back respectively. Assuming the raised wheel at the front of the lead unit and rear of the rear-most unit were the drive sprockets this provided a strong degree of redundancy in the design so that should one unit become damaged by enemy fire or a land mine or accident, the vehicle would not be immobilised. Each wheel was held on a single arm providing a good degree of movement and is reminiscent of the suspension arms of the M60. If it was just like those on the M60, then the arms would be hydraulically damped in their movement.

Viewed from the front of the tank the curved lower hull of the M60 is clearly similar in style to that envisaged by Ridlon and shows how these suspension arm units would have to project from a curved body. Also visible at the back in the angled hydraulic damper and also the track tension adjuster to the idler wheel at the front. Source: Author


The design of this vehicle was not going to need a new tank hull, as Ridlon simply planned to reuse the lower hulls from the M60. He proposed stripping out of the original drive components and fitting a new engine and the motors. On each side in the middle, where the two track units were closest to each other, the road wheels would be on the ground, creating a large empty space above them. This meant that the new upper hull of the M60 donor tank was going to need to bulge out across the side to improve the ballistic protection in that area.

Within the hull would sit the two crew along with the myriad of engines and motors proposed. In amongst all of this would be compartmentalised storage for fuel, compressed air, hydraulic fluid, water, fire extinguishers, and other items which were seen as being able to add to the protective structures around the crew.

Ridlon’s crude and un-detailed sketch of a future main battle tank. Source: Armor Magazine


The lower hull would be that of an M60, but the upper half would be remade to feature a large curved section across the top half bulging out at the sides to make use of the low section above the ends of both track units on each side. Further, Ridlon wanted the armor to be made in sections so that, as it was hit by enemy shells, the outer sections would break away on impact. To accomplish this, he wanted the outer sections of the armor to be made ‘soft’, with ‘hard’ armor on the inside, in what he describes as a “live” system. Further, he stated “the outer armor is composed of ribbed interlocking plates which give greater depth of armor and less weight as well as catch the projectile higher on the sides and thus disperse impact energy over a larger surface area”. The whole plan was not practical in that sense, but it could be considered as modular as each damaged section could at least be replaced.


The drawing of the turret and main armament is almost comically poor, with an impossibly small turret described as a ball-type turret. In this turret were to be two machine guns and either an automatic cannon or an automated one. The turret, as drawn, certainly appears far too small to accommodate any men but, if it is considered to be a remote turret, and a ball-type turret at that, it seems a little less ridiculous. Those turret-mounted weapons were not the end of the arsenal the tank would carry, as Ridlon also proposed rocket tubes should be placed in the upper hull, capable of attacking ground or airborne targets.


Ridlon, somewhat preciently for a US Main Battle Tank, proposed the use of a very small ‘gas turbine’, that is, a turbine-type engine running on petrol. This engine was not to directly drive the tank though, but was to drive a series of small high-speed homopolar generators. Each of these generators would be spread around the vehicle to minimize the chance of a single one becoming damaged and incapacitating the vehicle. Ridlon envisaged this system being duplicated for all military vehicles, as the humble Jeep would need just a pair of these small generators, a truck three and eight for a tank. Ridlon proposed eight small turbines working together to deliver power to thirty-two motors which powered the four sprockets which drove the tracks. The idea was that, by increasing the number of possible drive options, it would be impossible to be crippled by the loss of any one drive unit, motor or generator. The chances of all of those elements being made to work without something breaking seems highly optimistic even though it is the best part of his design considering elements of protective redundancy in the drive units to avoid being crippled and vulnerable to enemy fire. Rearranging the automotive elements of the tank to multiple small motors and generators would have made significant changes to the internal layout possible but that was beyond Ridlon’s skills as a designer, which perhaps explains why the drawing was so poor and the ideas on armor so poorly conceived.


Ridlon’s design took third place in the Armor Association’s competition, behind the Forsyth brothers’ coupled-tank and Eischen’s MBT, yet is drawn and described very crudely. The design appears utterly impractical with multiple complex systems, yet was held in high regard by the Armor judges. The question is why?

Perhaps it was a combination of novelties of the ball unmanned ball turret, the hybrid drive, the compartmentalization or some or all of those, but whereas the Forsyth design was a competent and well-thought-through design, this vehicle was simply impractical and an example of fantastical thinking for the time. There was no likelihood this vehicle would ever have been built and its inclusion in third place seems surprising given other better thought out designs. Ridlon did better than his tank design did, by 1970 he was teaching at a technical college before retiring in 1992. He died of lung cancer in 2011.

Illustration of Ridlon’s Main Battle Tank, based on his original sketch, produced by Andrei Kirushkin, funded by our Patreon campaign.



Crew 2
Propulsion Petrol-Electric (8 Petrol turbine driving 32 high speed homopolar generators)
Armament 2 machine guns, cannon, surface to air/ground missiles


Armor Magazine January-February 1963
Hibbing Daily Tribune, 12th June 2011 ‘Everett Philip ‘Babe’ Ridlon