M113 / M901 GLH-H ‘Ground Launched Hellfire – Heavy’

United States of America (1990-1991)
Missile Tank Destroyer – 1 Built

The AGM-114 ‘Hellfire’ missile was developed by the US Army specifically to counter modern Soviet main battle tanks in a potential clash of superpowers. Thankfully for all concerned, such a conflict did not erupt, the Cold War ending with the collapse of the Soviet Union. Nonetheless, the missile in service proved itself effective in combat and offered advantages over the TOW (Tube-launched Optically-tracked, Wire-guided) missile. The idea of a ground-launched version of the missile goes back to around 1980, even before the missile had been finished. It was not until 1991 that efforts were seriously made to use it within a project called Hellfire Ground Launched (HGL) coming in two types; Light (GLH-L) – mounted on an HMMWV, and Heavy (GLH-H) – mounted on a light armored vehicle such as the Bradley, LAV, or M113. It came to pass that only one of those options was pursued, the test mounting and fitting of the GLH-H turret on an M113, in this case, a repurposed M901 TOW version of the M113.

Background

The Hellfire missile is a third-generation anti-tank missile capable of both air launch (originally from the Advanced Attack Helicopter program by Hughes Aircraft Company) but also from the ground, in a line of development dating back to the late 1960s with the LASAM (LAser Semi-Active Missile) and MISTIC (MIssile System Target Illuminator Controlled) programs. By 1969, MYSTIC, the over-the-horizon laser missile program, had transitioned into a new program known as the ‘Heliborne Laser Fire and Forget Missile’, shortly thereafter renamed ‘Heliborne Launched Fire and Forget Missile’, later shortened to just ‘Hellfire’.

By 1973, the Hellfire was already being offered for procurement by Rockwell International based in Columbus, Ohio, and to be manufactured by Martin Marietta Corporation as the ‘HELLFIRE’, but somewhat misleadingly still being considered or labeled by some as a ‘fire and forget’ type of weapon. It was not until the arrival of Hellfire Longbow that a true fire-and-forget version of the Hellfire existed.

Procurement and limited manufacturing of the missile followed, with the first test firings of the finished product, known as the YAGM-114A, at Redstone Arsenal in September 1978. This was followed by modifications to the infrared seeker of the missile. With Army trials completed in 1981, full-scale production began in early 1982, with the first units fielded by the US Army in Europe at the end of 1984.

Targeting

Despite being occasionally mislabelled as a fire and forget missile, the Hellfire can in fact be used quite differently. Fire and forget implies that, once the weapon is locked onto a target, it could be fired and then the launch vehicle could retreat to a safe distance or move on to the next target. This is not strictly a correct description of the Hellfire, as the missile also has the ability to have its trajectory changed during flight by up to 20 degrees from the original and up to 1,000 m each way.

Targeting for the missile is by means of a laser which is projected from a designator either in the air or on the ground, regardless of where the missile is launched. An air-launched Hellfire can, for example, be targeted onto an enemy vehicle by a ground designation laser or by other designating aircraft. The missile is not limited to ground targets either. It can also be used to target aircraft, with some emphasis on its ability to counter enemy attack helicopters. Thus, the missile gains a substantial survivability bonus for a launch vehicle, as it does not have to remain in situ and can even be fired from over the horizon, such as over a hill at targets beyond.

The TOW missile was already available in the US arsenal, but Hellfire offered some things that TOW did not. For example, an increased standoff capacity along with an increased range (over the 3 to 3.75 km maximum range of TOW), an increased versatility of use, as the TOW was not suitable for aircraft use, as well as improved physical performance, such as armor penetration, explosive blast, and a shorter flight time due to traveling more quickly.

With a continuous laser seeker on the missile following the designation applied, the missile could easily target moving vehicles whilst being harder to intercept or counter (by engaging the launcher).

Improvements in ballistics through the 1980s improved the Hellfire design and the weapon has a maximum effective range quoted as being up to 8 km, with longer ranges being achieved with a reduction in accuracy due mainly to attenuation of the laser beam. Data from the Department of Defense, however, provides a maximum direct fire range of 7 km, with indirect fire out to 8 km, with a minimum engagement range of 500 m.

The Hellfire missile was first used in anger during the Invasion of Panama in December 1989, with 7 missiles being fired, all of which hit their targets.

Ground Launched Hellfire – Light (GLH-L)

The initial deployment of Hellfire in the ground role was considered to support the capabilities of the US 9th Infantry Division in 1987. By 1991, this idea of using Hellfires to support that unit had grown closer and it was decided that the M998 HMMWV would become the mount for the system. Interest was later shown by the Army in potentially deploying this system to the 82nd Airborne Division as well.

Using off-the-shelf components, and with a potential customer in the form of the Swedish military, who wanted a coastal defence missile, the Ground Launched Hellfire – Light (GLH-L) received a budget and went ahead. Five such vehicles were created. During trials in California in 1991, the system showed itself to be a success in firing trials. Despite this, the system was not adopted by the US military.

Ground Launched Hellfire – Heavy (GLH-H)

For heavier vehicles, ones with some built-in ballistic protection from enemy fire, three vehicles were the obvious choice of launch platform for the Hellfire, the Bradley, the LAV, and the ever-present M113. Operating as Fire Support Team Vehicles (FIST-V), the vehicles would be able to lase an enemy target and attack it directly if they wished, or once more use remote targeting. This was the Ground Launched Hellfire – Heavy (GLH – H) part of the 16-month-long GLH project.

It is unclear if a test was even carried out on a Bradley, but one was certainly done on an M113. This involved little modification of the vehicle itself except that it had to have a turret fitted to take the missiles and electronics involved. To this end, the M113 under the system was almost inconsequential to the vehicle, as it was little more than a test bed to haul the turret around. A large circle was cut out of the roof armor to take the new system. Conversion work was undertaken by the Electronics and Space Corporation (ESCO), including the fitting of the turret and installation of the laser equipment.

The ring in the roof does not appear to even have an adequate lock or means by which to prevent it from easily rotating under its own weight. The vehicle, currently on display in a museum in Nebraska, has the turret held in place with wire cables to prevent damage and rotation, suggesting the original gearing or control mechanism from the vehicle have been removed. This is because the donor M113 selected for the trials was an M901 Improved TOW Vehicle (ITV).

M901 ITV

The M901 ITV, introduced in 1978, differed from the M113 in that, instead of just being an armored box for infantry transport, it was an armored box with a roof-mounted missile system.

The basic M901 mounted the M22A1 TOW, followed by the M901A1 with the M220A2 TOW 2 missiles. The final option, the M901A3, carried the same TOW2 missiles and launcher as the A1 model, but had vehicular improvements, such as improved driver controls and RISE powerpack.

Carrying a dual M220 TOW launcher, the M901 had a crew of 4, consisting of a driver, a gunner, a commander, and a loader. This made sense for a vehicle where the missiles could be reloaded from inside, but less so for the GLH-L and GLH-H, on which reloading had to take place outside.

Turret Structure

The Hellfire turret consisted of 4 primary parts: the basket lying underneath the turret and inside the body of the M113, the manned section of the turret, the guidance system at the front, and the rocket pods themselves.

At the back of the turret were a pair of hatches with vision blocks around them. Ahead of the left sight which was mounted on the roof and fixed in place, was the designator offset on the turret front, where a pair of angular protrusions covering the front of the turret face and a pair of thickly made boxes on each side. Each box appears to have been detachable by a series of bolts on the sides and top. These housed the rotating mount for each pod.

View of the turret roof showing the hatches at the back and fixed roof sight. The thickly made boxes are visible both from the front (left) and rear (right).
Source: Author

The body of the turret was approximately 8 mm thick aluminum all round. At the front, on each side, appear to be a pair of large armored boxes, approximately 35 mm thick on the sides and roof. The actual thickness of the roof cannot be measured as is, but the mounting plate for the gunner’s sight is 16 mm thick and sits on an additional plate on the roof with approximately the same thickness.

The hatches at the back are mounted on steel springs but have an aluminum body 40 mm thick. They have a thin steel covering bolted to the top of the hatch. The purpose of this construction is unclear.

The hatch on the left is fitted with 4 simple episcopes, although only the one facing 45 degrees to the rear left would be of much use. No sight is provided forwards for the gunner except for the large roof sight. The episcope facing left is completely obscured by the left-hand missile pod and the one to the right is blocked by the other hatch. The one fitted to the rear right, looking 45 degrees backward, is also blocked, this time by a small metal box in the center of the rear of the turret roof, the purpose of which is unknown.

If the crew member using the left hatch is poorly served by optics, then the one on the right is even more so, as they only had provision for 2 episcopes and these are half the size of the ones on the other hatch. Both are positioned facing forwards at 45 degrees, meaning no direct view forwards from that position and neither is of any use. The one on the right simply faces directly into the right hand missile pod and the one on the left would be completely blocked by the large roof-mounted sight, or would be if it had not been removed and welded over. Thus, of the 6 ‘normal’ episcopes on the turret for the crew, one is missing, three are completely or almost completely blocked by other turret features and none of them look forward.

Looking down on the turret hatches. Hunnicutt identified these are the commander’s hatch on the right and gunner’s hatch on the left.
Source: Author.

Guidance System

The turret is asymmetrical, with the guidance module offset to the left at the front. It consists of a pronounced armored box on a mantlet, allowing the laser designator to be fitted. The author R. P. Hunnicutt states that both the US Army ground locator designator (G.L.L.D.) and US Marine Corps Modular Universal Laser Equipment (M.U.L.E.) were fitted.

The box housing it, like the rest of the turret (apart from the mantlet), is made from aluminium, with a front panel 9 mm thick, which houses the lens over the laser designator. The back of the box is 11 mm thick and then mounted to the steel rotating mantlet, which is approximately 50 mm thick. The aluminium framing on either side of this area is 20 mm thick on the right side and 32 mm thick on the left side. The reason for this difference is unclear.

The amount of rotation available for the guidance box on the mantlet is unclear, as there is a metal bolted to that rotating part which would foul on the top edge, where it meets the turret roof, at a relatively modest angle of around 30 degrees or so. It appears that this module would be severely limited in the ability of targeting aircraft, such as helicopters, but this was just a test bed, so what modifications would have been made to allow for a broad spectrum of possible targets is unknown.

Armament

Absolutely no secondary armament of any kind is apparent on the vehicle, either on the hull or on the turret. It is likely that, should such a turret ever have seen production, some kind of weapon mount would have been added in the form of a roof machine gun. Even then, however, with those huge pods blocking both sides, the coverage of such a weapon would be extremely limited. The vehicle is thus rather vulnerable to any enemy nearby. The only provision for self-defense are the smoke dischargers, which consist of a single 3-pot mounting on the front right corner of the turret and the dischagers on the hull (2 four-pot discharges on the front corners). Hunnicutt states that a single machine gun was fitted for close-in protection, but this is not shown in any photograph and no mounting for it is apparent either.

The Pods

As mounted on the M113, the Hellfire system took the basic form of a pair of 4-missile pods on either side of a turret. Each pod was divided into 4 chambers, each measuring 335 mm wide by 335 mm high internally and made from aluminum supported with ribs 7 mm thick. The internal structure of the pods is heavy, with a central vertical divider and floor plate approximately 40 mm thick. Holes in the front and back of the pods indicate that, at some point, covers were also fitted to these pods and one can be seen in a photo of the system during trials.

Each pod was fitted with what appears to be a hinged lid, but closer inspection shows these hinges are on both sides of the top, precluding some sort of vertical reloading. Reloading, in fact, seems to only have been possible from either in front or behind the pod. Given the height of the turret above the ground, reloading would entail standing on the hull roof with the turret partially rotated.

Each pod can clearly rotate from at least horizontal, but the upper limit is unknown. Photographic evidence from launches show an angle less than 45 degrees and also that each pod could be rotated independently.

Eight Hellfire missiles could be carried ready for action on the GLH-H, compared to just 2 on the GLH-L. It is likely that additional stowage inside the back of the GLH-H mount, whether on the Bradley, LAV, or M113, would also have been installed to carry more missiles. For reference, the M901 had space for an additional rack of missiles. The same would likely have been true of any fielded GLH-H system as well.

Basket

Inside the vehicle, the driver’s station was just as it was on the M901. However, the area under the turret was quite different. The turret descended into the hull using a riveted cylindrical aluminum basket, with a motor or gearing mounted in the center of the floor. On each side of this were the two crew positions. Whilst a space was retained between this cylinder and the rear access door, in which a fourth crewmember might be located with additional missiles, there is no space on either side of the cylinder around which passage can be obtained. Through-access from front to rear on the vehicle is therefore limited to passage through the large gaps in the cylindrical basket and, with two crew in there, this would not be possible. In its current state, in 2020/2021, there is no safe access within the vehicle.

Conclusion

GLH-H appears to have been a bit of an orphan program. The GLH-L had been supported by the Army and by the Hellfire Project Office (HPO), which had accumulated the work of MICOM Weapons Systems Management Directorate (WSDM) in February 1990. HPO had then followed up on the Hellfire, as it was used in service and was being improved and refined. At the same time, Martin Marietta received a contract for the development of the missile known as the Hellfire Optimised Missile System (HOMS) in March 1990 and both had supported the work on GLH-L. However, in April 1991, HPO was redesignated as the Air-to-Ground Missile Systems (AGMS) Project Management Office, leaving no doubt that official interest seemed to have ended in ground-launched applications in favor of aircraft-launched systems. Indeed, this was just a few months after work on developing the Hellfire missile for the Longbow Apache helicopter had started.

By 1992, HOMS too was gone and its work was simply repurposed as ‘Hellfire II’, which was to finally take the form of the AGM-114K version of the missile. The GLH-H side of things, therefore, was left out in the cold. There seemed little appetite for a ground-launched version of a weapon that was already successful on aircraft and the development work specifically was to focus on airborne use as well.

What did the GLH-H offer that a vehicle like the M901 ITV did not? On a one-to-one comparison scale, both vehicles had pros and cons, although the substantially larger missile load on the GLH-H and the longer range of the Hellfire missile were perhaps the most obvious. The system was, however, unproven. The TOW system had already been in ground use since the early 1970s and was combat-proven, as well as being substantially cheaper on a missile-to-missile basis. Having a maximum engagement range of 7 km instead of just over 3 km was certainly no small deal and it was not argued that the Hellfire was in any way inferior to the TOW. The issue was perhaps more of a practical one. The TOW was already in widespread use and proven and the GLH-H was not. If the enemy were further away, then they were by definition a lesser threat anyway and could be engaged by other means, such as air-launched Hellfires. The GLH-H system was also huge. Those missile pods were vulnerable to damage from enemy action or environmental or terrain factors and there was no way of reloading them safely from within a vehicle such as the M113, as there was with the M901, meaning the crews would have to be exposed. The Bradley, on the other hand, had a large hatch over the roof at the back, which might have allowed for some limited protection for reloading.

More than the design issues of the GLH-H launcher and compatible mounting, the development of GLH simply came too late. Despite being considered as far back as 1980, no work was really done for over a decade, by which time the TOW was even more widely deployed than before and there were other new missiles for infantry use available. If GLH was ever going to get actively developed, it might have been then, during the peak of the Soviet threat in Western Europe, when large numbers of Soviet tanks were expected to be encountered and a new missile system could have added much-needed firepower. With the collapse of the Soviet Union in 1990 and existing anti-tank measures being proven in combat in the Gulf War of 1990-1991, it was not clear why a new system would even be needed, whether on a light or heavy platform.

After all, if the need for a better-protected platform with missiles was essential, there was no reason not to just mount the M220 TOW system onto a Bradley anyway, although what this would add when mounting a pair of TOW missiles on a Bradley was standard is even less clear and really just reinforces the point of this being a project without a true purpose.

It was all academic by the early 1990s, the M901 series was being removed anyway, the Bradley already carried a pair of TOW missiles on the side, meeting the same level of firepower, and two systems to do the same thing, with one substantially more capable as a basic vehicle than the other made no sense. The only logical outcome for a GLH-H to have met a ‘need’ would have been Bradley based rather than on an M113, but this step was not taken and would not have fundamentally changed the viability of the project other than creating a very identifiable variant of the Bradley on the battlefield. With control of the development of the whole project handed over to an aircraft-focussed approach, the project with unclear objectives and needs was destined for failure.

The M113 / M901 converted with this GLH-H 8-missile launcher resides today at the Historic Museum of Military Vehicles in Lexington, Nebraska. The author wishes to express his gratitude to the staff there for their assistance.

Ground-Launched Hellfire Redux?

In recent years, however, renewed interest has been shown in a ground-launched Hellfire version to replace TOW and upgrade the US military’s ability to strike enemy targets from even further away. In 2010, Boeing tested the ability of the Avenger turret air defense system to launch Hellfire missiles. This would allow the Hellfire once more to be mounted on light vehicles like a HMMWV, but also on the LAV and other systems.

The Hellfire missile has also already been mounted in the ground role on the Pandur 6 x 6, with the Multi-Mission Launcher (MML), on the Family of Medium Tactical Vehicles (FMTV) truck and in Lockheed Martin’s Long Range Surveillance and Attack Vehicle (LRSAV) based on the Patria AMV firing the Hellfire II in 2014. However, such systems seeing service seems unlikely, as the Hellfire missile and variants are, as of 2016, destined for replacement by a new missile known as the Joint Air to Ground Missile (J.A.G.M.), meant as a common missile across all platforms, naval, air, and ground-based.

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