Modern US Improvised Vehicles

CV-990 Tire Assault Vehicle (TAV)

United States of America/NASA (1995)
Robot – 1 Built

By 1993, the U.S. National Aeronautics and Space Administration’s (NASA) four Space Shuttles, Columbia, Challenger, Discovery, and Atlantis, as well as a fifth, Endeavour, which made its inaugural flight less than a year earlier, held between them over 50 completed missions. The Space Shuttles very much formed the backbone of NASA’s space operations. Like all spacecraft, the Shuttles were upgraded throughout their lives. Every system and component was trialed and tested to its breaking point to see if it could be improved. In 1993, it was the humble tire that came under the knife.
The Space Shuttle’s tires weren’t just any tires; having to go to space and back meant that they had to be tough. Each tire, of which there were six, could support over 64 metric tons. The pressure inside the Michelin-brand tires was 340 psi (23.9 kg per square centimeter).
To test the Shuttle tires, NASA roped in an old medium-altitude atmospheric testing aircraft, a modified Convair 990 Coronado narrow-body airliner with the tail number NASA 810. NASA 810 was modified into a landing systems research aircraft or LSRA. Its job was to test the brakes, landing gear systems, nose wheel steering control, and overall durability of the Space Shuttle’s tires. Tests of the Shuttle tires with the Convair 990 LSRA began in April 1993 at NASA’s Dryden Flight Research Center at Edwards Air Force Base in California. The CV-990 LSRA, flown by astronaut and test pilot Charles Gordon Fullerton, completed 155 missions by the close of the program in August 1995.

View of the underside of CV-990 LSRA ‘NASA 810’, showing the Space Shuttle wheel suspended on a special hydraulic assembly between the airliner’s normal landing gear, April 1993. Photo: SOURCE

NASA 810 before it was modified into a landing systems research aircraft, July 1992. Photo: SOURCE
When tires are tested to their limits, blowouts are to be expected; and when there’s enough force behind that blowout to rip limbs from their sockets and hurl massive chunks of rubber hundreds, if not thousands, of feet, one should obviously err on the side of caution. The most dangerous tires were the ones that seemed to survive the tests. Outwardly, a tire could appear completely intact, while on the inside it is ready to burst. Extreme wear, as well as heat and the resulting pressure changes, could weaken the tire to the point that even touching it could cause it to fail. Even allowing the hot tire to cool could be sufficient stress leading to a rupture.
NASA tried several simple ways of safely detonating the tires, but they did not always work, and could even be dangerous. A 450 lb (204 kg) bomb disposal robot, worth 100,000 U.S. dollars, was available to the CV-990 LSRA crew, but it was often preoccupied when they needed it. In addition, the bomb robot was 4 feet (1.22 m) tall, 4 feet (1.22 m) long, and 3 feet (0.91 m) wide, making it too large to effectively maneuver under the plane.

The Last Operational Use of the King Tiger… Kind of

This problem, as with most problems when you put your mind to it, was solved with heavy armor. Not just any heavy armor, the heaviest and most fearsome tank of the Second World War, the King Tiger, albeit made of plastic and much smaller than the original.
David Carrott, a portable radio communications expert contracted by NASA, stepped forward with a way to puncture stressed Shuttle tires coming in off the LSRA. Carrott bought a Tamiya 1/16th scale remote controlled Tiger II (Item No. 56018), retailing at around 1,000 U.S. dollars, and used it as a base to build a tire-popping robot. He built the lower portion of the hull, the suspension, tracks, and rear plate, but forwent the rest, using approximately 25% of the original model’s parts. He then fabricated a metal piece resembling an inverted “U”, which took the place of the upper hull sides and roof. Another metal piece was cut out in the shape of the upper frontal plate and welded to the front of the machine. The use of metal for the hull of the machine was presumably to protect it from debris from exploding tires, which could easily have destroyed it were it made of plastic. Side skirts also made of metal were attached above the tracks with 9 rivets per side. The reason why Carrott thought the vehicle needed side skirts is unknown, though some have theorized it was to keep any stray wires or debris out of the tracks. An interesting detail to note is that the side skirts seem to have been custom ordered, as on the top of the right skirt is what appears to be a NASA-tagged barcode.
The “weapon” of the machine was a DeWalt power drill with a 3/8 inch (9.53 mm) bit. Power was provided by a single 12 Volt, 7 Ah, Black and Decker VRLA rechargeable battery. The handle of the drill was removed and the remaining portion mounted above the radio operator’s area on the right-hand side of the model tank chassis. To the left of the drill was a small pod containing a video camera as well as a transmitter.
Two other Black and Decker/DeWalt electric drill motors were employed to propel the tank, one driving each track through a geared transmission. The motors driving the tracks as well as the drill were all controlled through three separate custom solid-state VANTEC speed controllers. All onboard equipment, such as the video camera and the motors driving the tracks, were powered by the drill battery protruding from the engine deck.
The controller was a JR X388S transmitter and receiver operating on government frequency. The signal from the camera was received by a down-converter and turned into a composite video. A portable black-and-white television displayed the video feed to the operator.
The whole machine was built for under 3,000 U.S. dollars. It weighed 20 pounds (9.1 kg), and was 12 inches (30.5 cm) high, 18 inches (45.7 cm) long, and 8 inches (20.3 cm) wide. Carrott called his creation the CV-990 Tire Assault Vehicle. It was referred to as the TAV for short.

Illustration of the ‘Tire Assault vehicle (TAV)’ by Bernard ‘Escodrion’ Baker, funded by our Patreon campaign.


The TAV was available for 32 of the 155 Shuttle tire test missions. While it only operated from February to August of 1995, catching the tail end of the test missions, the TAV performed its role flawlessly. It safely detonated 9 “live” tires, 4 of which were extremely volatile, and could have endangered the lives of any persons who would have had to go in to defuse them had the TAV not been present.
There is only a single known photo of the TAV in operation (shown below). In it, the camera is seen mounted on an elevated bracket at the far rear of the machine. In place of where the camera is normally seen, to the left of the drill, is what appears to be an infrared thermometer. This would make sense, as the temperature is directly related to pressure inside a tire, monitoring the temperature also allows you to monitor the pressure. Is it possible, probable even, that the TAV used this configuration for most or all of its service life, only being reconfigured after the Shuttle tire tests were finished. It is equally probable that it was reconfigured depending upon the exact situation which it faced.

The Tire Assault Vehicle moving in on a Shuttle tire after Test Flight 145, July 27th, 1995. Photo: SOURCE


The tests performed with the Space Shuttle tires between 1993 and 1995 provided a large amount of data. Most notably, the knowledge of the exact behavior of Shuttle tires allowed the crosswind limit for the Shuttle, that is, the maximum speed of wind crossing the runway parallel to the landing aircraft deemed safe to land in, to be increased from 15 knots (17.3 mph, 27.8 kph) to 20 knots (23 mph, 37 kph).
Life as a landing systems research aircraft would be the final mission for NASA 810; after completion of the program, it was retired. It now stands as a gate guard at the Mojave Air and Space Port in California.

NASA 810 as she sits today at the Mojave Air and Space Port, March 2017. Photo: SOURCE
Remarkably, the TAV survives as well. It is located in a plexiglass box in the gift shop of the Air Force Flight Test Museum at Edwards Air Force Base in California, where it spent its entire operational life.

The TAV in its display case at the Air Force Flight Test Museum, Around May 2017.

The plaque at the foot of the TAV display case. Photo: SOURCE

Links & Resources

German King Tiger Tank – Tank Encyclopedia Support Shirt

German King Tiger Tank – Tank Encyclopedia Support Shirt

Get out there with the confidence of the King Tiger in this tee. . A portion of the proceeds from this purchase will support Tank Encyclopedia, a military history research project. Buy this T-Shirt on Gunji Graphics!

Modern US Improvised Vehicles

Marvin Heemeyer’s Armored Bulldozer

United States of America (2004)
Improvised Fighting Vehicle – 1 Built

A one-man rampage

In 2004, the resort town of Granby, Colorado was terrorized by a man named Marvin John Heemeyer. A costly amount of property and vehicles were destroyed by a single man and his retrofitted Komatsu D355A bulldozer. Heemeyer’s bulldozer (also known as the Killdozer) was an engineering marvel for a single man and managed to take explosives and armor piercing ammunition. Not much is known about the man, but he claimed to be influenced by God. He recorded himself prior to the rampage explaining his motives and his targets. However, even though the recordings were released to the news reporters, they were never fully released to the public. Only bits and pieces can be found online.Heemeye's Killdozer at the end of its rampage
Heemeye’s Killdozer at the end of its rampage


Marvin John Heemeyer (born in South Dakota, October 28,1951), a successful welder, owned two muffler shops named “Mountain View Muffler” in Granby and nearby Boulder, Colorado. He was known by the town for fighting civil issues such as a failed proposal to bring gambling to Grand Lake, Colorado (where he lived) in 1994.
The town of Granby allowed a cement plant to be located near Heemeyer’s muffler shop in 2000. This angered him over the noise, dust and the limited access to his shop it could create. Heemeyer tried to convince Cody Docheff, the project’s operator, to sell his property, but ultimately failed.
In 2001, the town sided with the concrete plant. Heemeyer countered this with a lawsuit which failed again.
In 2003, he found himself involved in another conflict with the town concerning whether he should be connected to the town’s sewage system. Heemeyer was not part of the system. He was forced to pay the $2500 fine and wrote a check which he enclosed the note with “cowards” written on it.
He plotted his revenge. This involved his Komatsu D355A bulldozer. He had originally purchased it to construct roads to his shops. In March of 2003,, Heemeyer deeded his house to a friend and lived in his shop. He then sold off both of his shops and the building that housed his bulldozer.
However, he kept 185 square miles (479 square kilometers) of closed off land with a building where the bulldozer was moved to in December the same year. For six months, he used his welding skills to armor up his bulldozer so he could use it for his revenge.


The default 49 ton Komatsu D355A bulldozer is powered by a 410 hp (305 kw) engine. It had a top road speed of 7.45 mph (12 km/h) and a horsepower per ton of 8.36. Heemeyer’s armored version brought the weight up to 61 tons. This most likely slowed the bulldozer somewhat and decreased the horsepower per ton to 6.7.


The bulldozer was armed with a .50 (12.7mm) Barret M82 semi-automatic rifle at the rear, 5.56mm FN FNC semi-automatic assault rifle at the front, and a .223 (5.7mm) Ruger Mini-14 at the right. His two side arms were a .357 (9.1mm) Magnum revolver and 9mm Kel-Tec P-11. These weapons were fired from small firing ports inside the cabin.

One of the Killdozer's weapons, a Barret M82 rifle
One of the Killdozer’s weapons, a Barret M82 rifle


The armor consisted of two half inch (12.7mm) steel plates with concrete in the middle and bonded plexiglas which gave it the same benefits of composite armor. This proved very effective against small-arms fire, armor piercing ammunition and grenades.
The cameras which allowed Heemeyer to see his surroundings were connected to three monitors and protected by three inch (76.2mm) bulletproof plastic. The armored Komatsu D355A bulldozer also had a sophisticated air filtration system and air conditioning system.


On June 4, 2004, Heemeyer greased up his bulldozer to make it harder for people to climb on top before he bolted himself shut inside. He smashed through the building that housed his bulldozer and proceeded to his first target which was unsurprisingly the cement plant near his former business.
While this factory was being destroyed, the owner, Cody Docheff, drove one of his own construction vehicles to try and stop the destruction. Heemeyer saw this and quickly charged towards Docheff’s vehicle. Docheff regretted his decision. His vehicle was not big enough to stop the bulldozer so he tried to make his escape by driving away. Heemeyer rammed the rear of Docheff’s vehicle.
The armored bulldozer preparing to rip through a building
The armored bulldozer preparing to rip through a building
During his rampage, he managed to destroy a local bank, his former business, hardware store, the town hall, the police department building, the home of Granby’s deceased former mayor, the town’s library, local newspaper office, former judge’s home, and an enormous amount of cars. He spent a few minutes trying to ignite the Independent Propane Company’s storage tanks by firing at them with his .50 cal rifle. Luckily, they did not explode or catch fire.

Marvin Heemeyer’s armored bulldozer reconstitution by D Bocquelet


After being sealed by an industrial loader inside a group of buildings, Heemeyer in his armored Komatsu bulldozer tried to escape by ramming through buildings. The chaos stopped when the bulldozer collapsed inside a store’s basement.
Police officers charged towards the bulldozer but it was covered with grease which made it tougher for them to get on top of the machine. Colorado’s governor considered using the Apache’s Hellfire missiles from the Colorado National Guard to destroy the vehicle, but it was already bogged down inside a basement. Heemeyer committed suicide with his .357 (9.1mm) Magnum revolver. His armored bulldozer was stuck. He could see no way out and he did not want to go to jail.


Fortunately, there were no civilian or police deaths, however, Heemeyer had caused seven million dollars of damage to buildings and vehicles. It is said that killing civilians wasn’t his intentions, but his tape recordings say otherwise. Heemeyer’s recordings were released by the police department to news stations, however, only bits and pieces can be found online. It took twelve hours with a blowtorch to enter into the cabin of the armored bulldozer to retrieve his dead body.
The town hall after the rampage This truck was one of the many vehicular victims of Heeymer's rampage
The incident left 7 million dollars worth of damage.
Heemeyer is seen by most as just a terrorist, but some see him as a patriotic American for standing up to the government. C4, grenades, and more than 200 bullets were used against the bulldozer and had little to no effect. A few people in Granby proposed a yearly celebration of the incident to generate tourism. The idea was rejected, and the armored bulldozer was scrapped.
Luckily, insurance and state aid came to help the ravaged town of Granby and it quickly got back onto its feet. After Heemeyer’s rampage, it received the reputation as the “Killdozer”. Funny enough, this isn’t the first kind of attack in Colorado. In 1998, a man named Tom Leask conducted an attack with a government owned front end loader in Alma, Colorado. He managed to destroy the town’s post office, town hall, fire department, and water department until he was taken into custody.

Similar Vehicles

Armored bulldozers are nothing new and are present in many conflicts as professionally manufactured or improvised combat vehicles. This bulldozer is particularly interesting due to how well it protected him from C4, grenades, and armor piercing ammunition. Plus, it only took one expert welder to make this impressive contraption.
The Israeli Defense Forces has different armored versions of the D9 Caterpillar with slat armor and a protected cabin; other examples include the British Centaur bulldozer, Japanese Type 75 bulldozer, American D7G Caterpillar bulldozer, armored bulldozer used by the Sri Lankan Armed Forces in Sri Lanka against the LTTE (Liberation Tigers of Tamil Eelam), and dozens of other bulldozers.

An article by Joshua Martinez


Suburban Legends: True Tales of Murder, Mayhem, and Minivans
The Colorado Mountain Companion
Komatsu D355A-1 specifications
News article about the event

Killdozer specifications

Dimensions TBA m (TBA)
Total weight, battle ready 61 tons
Crew 1
Propulsion Komatsu SA6D155-4A, 410 hp
Armament .50 (12.7 mm) Barret M82 semi-automatic rifle
5.56 mm (0.22 in) FN FNC semi-automatic assault rifle
.223 (5.7 mm) Ruger Mini-14
Armor Plexiglass, Concrete, .5 inch (12.7 mm) steel plates



A good shot of the bulldozer after the destruction spree
Various shots of the KilldozerVarious shots of the KilldozerVarious shots of the Killdozer