Name	MBT-70
Origin	/
Type	Main battle tank
Is vehicle	yes
Design year	1965-69
Number	14 (prototypes and pilots)
Weight
Length
Width
Height
Primary armament	152 mm XM-150E5 120 mm gun (FRG only)
Secondary armament	20 mm cannon 7.62 mm machine gun
Armour	spaced armor
Engine power	.
Speed
Suspension	hydropneumatic
Crew	3 }}

The MBT-70 (German: ''KPz 70'') was a 1960s German-U.S. joint project to develop a new main battle tank, which was to be equipped with a number of advanced features. It utilized a newly developed hydropneumatic "kneeling" suspension and housed the entire crew in the large turret. The MBT-70 was armed with a 152 mm XM-150 gun/launcher, which could use conventional ammunition and the Shillelagh missile for long range combat.

In 1969 the project was well over budget and the Germans withdrew from the effort, developing a new main battle tank on their own instead. In the US the development continued for a short time, until in 1971 the Congress cancelled the program. The MBT-70 is the "grandfather" of the Leopard 2 and the M1 Abrams, the current main battle tanks of both countries.

History

In the early 1960s the German Leopard 1 and the US M60 were the newest main battle tanks in their respective country's service. While designed to counter the T-54/55 tanks, both tanks were placed at a disadvantage by the new smoothbore gun fielded in the T-62. It became clear that the next generation of Soviet tanks would have increased firepower and protection. An upgrade project for the Leopard was planned, but it appeared this model would not be enough of an advance to be worthwhile.

To solve the problems in the tank forces, Germany and the United States had a memorandum of understanding to develop a common new tank for both armies. However, this may have been one of the worst things to happen to the project, as both teams started "pulling" the design in their own directions. Arguments arose over almost every part of the design: the gun, the engine, even whether or not the design would use metric or SAE measurements. This last dispute was eventually "settled" by using both systems, thereby increasing costs considerably.

Design

Many features of the MBT-70 were ahead of their time. The vehicle used an advanced hydropneumatic suspension system that allowed for fast cross-country speeds even though it was to weigh . The suspension could be raised or lowered on command by the driver, down to put the bottom of the tank just over from the ground, or up to for cross-country running.

The MBT-70 was designed with a low silhouette, contrary to the M60, one of the tallest MBTs ever built. The MBT-70 ended up very low, just over from the floor to the turret-roof. The driver therefore had to be moved into the big turret, where he was located in the cupola, which rotated so that he was always looking in the direction the tank drove. The tank was therefore capable of driving backwards at full speed.

The US version was to mount the newly developed Continental AVCR air-cooled V-12 diesel of . German versions originally used a similar Daimler-Benz model, but later moved to an MTU design of . The MTU unit could be easily swapped out of the tank, along with the drive train, in 15 minutes. Both versions could reach on their engines, at the time an unheard-of speed for such a heavy tank.

Armament

The MBT-70's main armament was a stabilized XM-150 152 mm gun/launcher, a longer-barreled and improved variant of the XM-81 gun/launcher used in the light M551 Sheridan and the M60A2 'Starship'. This gun/launcher could fire conventional 152 mm rounds like HE, anti-personnel, HEAT and APFSDS, but also the Shillelagh missile, a 152 mm guided missile, which had a combat range of some . In the 1960s the effective combat range of the L7 tank gun was considered to be about . The XM578 APFSDS was made of a newly developed tungsten alloy, which was 97.5 percent tungsten. This new alloy had a density of 18.5 g·cm³, which was a big improvement compared to the older tungsten-carbide APDS and APFSDS. Another new feature of the ammunition was that the tank rounds were "caseless" i.e. they had combustible cases. The MBT-70 was equipped with a laser rangefinder and an auto-loader, located in the turret rear, two 'cutting edge' devices for this time. The auto-loader was capable of loading both the missiles and the normal tank rounds.

The Germans were planning to use the MBT-70 in combination with the ''Keiler'', a tank built on the MBT-70 chassis equipped with a Rheinmetall 120 mm smoothbore gun, therefore some MBT-70 prototypes were tested with the 120 mm gun. The MBT-70 would destroy enemies at long ranges, while the ''Keiler'' would have an effective combat range of up to .

The secondary armament of the MBT-70 consisted of a remote-controlled 20 mm autocannon for use against aircraft and light armoured vehicles. The autocannon had a caliber-length of 85 and was stored inside a container behind the driver's rotating cupola. It could be retracted to reduce the overall height. Furthermore a 7.62 mm machine gun was mounted coaxially alongside the main gun for close-defense.

The ammunition load of the MBT-70 prototype seen in the Deutsches Panzermuseum consists of 42 tank rounds, 6 Shillelagh missiles, 660 20 x 139 mm and 2700 7.62 x 51 mm rounds.

Protection

The MBT-70 was protected by a newly developed type of spaced armor in the frontal area of the hull and the turret. It consisted of an outer layer made of cold-rolled hardened steel and a softer inner steel layer, which also served as spall liner with space between the two. This type of armour offered better protection against armor-piercing and HEAT warheads, which were by then one of the strongest threats against tanks. The armor offered protection against 105 mm APDS at a range of only . The design included bulkheads, fireproof doors, and blow-out sections in the ammunition storage area to minimize crew injury when a hit was received.

The tank's low silhouette, which could be lowered from to only , was also a big advantage. Compared to the M60 tank, the MBT-70 had a lower profile. With the hydropneumatic suspension lowered it was also smaller than the Leopard 1, which gave the MBT-70 a better hull down position.

For protection against neutron radiation a 15 to 20 cm thick layer of polythene was installed around the crew compartment. The MBT-70 was protected against EMPs and NBC as well.

Mobility

The MBT-70 was capable of reaching a top speed of , and maintained a higher level of mobility than any tank of its time. It was considerably faster than the M60 and even faster than the Leopard 1 tank. It also could accelerate three times faster than the M60. In cross-country performance the high power engine and hydropneumatic suspension allowed it to travel almost three times as fast as the M60 without causing problems for the crew.

Testing

A prototype series started in 1965, with one mild steel hull and six "complete" hulls of both the US and German versions, for a total of 14 hulls. The lower hull and drivetrain were tested in 1966, and full trials began in 1968.

The tank proved to be better than the M60: it was considerably faster, both in all-out speed and, more importantly, with about three times the acceleration. All of this led to a reduction in the time the tank was exposed to fire, in testing it was 1/3 less likely to be seen while maneuvering than the M60, and it could run a obstacle course in 30 % less time.

Problems

An unanticipated problem was that the drivers complained of disorientation when the turret was rotated, contrary to the predictions of the designers who felt the location of the cupola near the center of rotation would eliminate this effect. The German 120 mm proved excellent, but the XM-150 was a serious problem. The similar but smaller XM-81 mounted on the M551 Sheridan proved to be just as troublesome. There were also several problems with the ammunition. The caseless design made conventional tank rounds too vulnerable to water. Wet rounds expanded so they would not fit into the barrel anymore or left hard residues after being fired. The auto-loader was capable of handling the Shillelagh missile without problems, but the combustible cases of the tank rounds could be deformed by it. As is often a problem with caseless ammunition, the ammunition also had a tendency to "cook-off", or fire prematurely, due to heat build-up in the barrel from previously fired rounds. The attempted solution, to only carry a single round with the balance in missiles, also proved unacceptable. Deployment of the 20 mm anti-aircraft cannon also proved difficult and the weapon itself was overly complicated and nearly impossible to use effectively.

Another problem of the MBT-70 was the increasing weight. While at the beginning of the project, a weight of some was projected, it increased to during development, which forced the designers to redesign some elements, so that finally a weight of was reached, still higher than required. This meant that the MBT-70 would require its own armoured recovery vehicles and bridge-launching systems.

Commentators on the MBT-70 typically assert that though it was innovative in many respects, the project was ruined by the use of too many untried and unproven technologies. A senator from Arkansas, Senator James W. Fulbright, mentioned that to drive a MBT-70, a master's degree in a technical institute would be required.

Cancellation

By 1969 the MBT-70 cost five times what was projected, at $1 million a unit ($}} in present-day terms). Originally the planned costs of the MBT-70 project were as low as $80 million (or 292.8 million DM), but in 1969 the project had already costed $303 million (nearly 1.1 billion DM). West Germany's part alone of this was about $130 million (475.8 million DM), which in itself was more than the original planned total costs of the project. Germany backed out of the project, and started the development of the Keiler on its own. Later this program would lead to the Leopard 2 The Leopard 2, like the ''Keiler'', uses a 120 mm smoothbore gun. At this point Congress also began objecting to the rapidly increasing price and soon canceled it in 1970. The Army then introduced a lower-cost system based on the same design, known as the XM803. This succeeded only in producing an expensive system with capabilities similar to the M60 it was supposed to replace.

Congress, angered by the delays and cost overruns, cancelled the project in November 1971, and redistributed the funds to the new XM815. This project was later renamed XM1, the project that led to the very successful M1 Abrams tank. The M1 had a conventional, but welded steel turret, suspension, and gun, and was innovative in incorporating advanced armor materials and the use of a gas turbine engine.

Surviving vehicles

Altogether 14 prototypes and test-beds have been built, two of them were made of mild steel. Some of them have survived in museums and can still be visited today.

American prototypes

One prototype is located in the US Army Ordnance Museum in Aberdeen, Maryland

A mild steel prototype in bad condition can be seen in the Military Museum of the Southern New England in Danbury, CT

German prototypes

One prototype is located in the Deutsches Panzermuseum Munster

Another is located in the Wehrtechnische Studiensammlung Koblenz

See also

VT tank

Leopard 2

M1 Abrams

References

External links

MBT-70 page at the Armor Site

Category:Main battle tanks of the United States Category:Main battle tanks of the Cold War Category:Abandoned military projects of the United States Category:Abandoned military projects of Germany Category:Trial and research tanks Category:Main battle tanks of Germany Category:Cold War tanks of Germany Category:Cold War tanks of the United States

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