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MBT-70 / XM803

During the 1960s the US Army continued to improve the M60 tank. However, unless a new tank was fielded there would be a large gap between US and Soviet tanks when the Soviets fielded their next generation MBT. The first try at the Supertank concept, the MBT 70 was a failure due to high costs. An early example of a codevelopment initiative is the MBT-70 [Main Battle Tank 1970s] program between West Germany and the United States. Thanks largely to the support of then Defense Secretary Robert McNamara, agreement was reached in 1963 between the two nations to jointly develop a main battle tank. With cast homogeneous steel layered armor, the inner shell was overlaid with spaced high hardness homogeneous rolled armor steel.

The US prototype was equipped with a 152mm gun launcher with an auto loader. It was capable of firing AP/HE/WP rounds and the Shillelagh Missile. The main armament was to be a long-barrelled improved XM-150 variant of the XM-81 gun/launcher mounted on the M551 Sheridan and the M60a2 Patton. This was a much more reliable weapon than the earlier variant, firing Sabot, HE, and Cannister rounds in addition to the Shilelagh A/T Missile, but the earlier weapon's reputation was such that it was a lost cause from the start. It had a coax 7.62 machinegun and a 20mm AA remote control gun in a separate part of the turret. It would pop up out of twin hatches and fire at the target. The German version had a 120mm autocannon, instead of the 152mm gun launcher.

In some respects, the tank was fairly conventional. It had a diesel engine, and the armor, whilst strong was not of the composite type on the Abrams. The silhoutte was low. The tank had a three-man crew, each in his own compartment. Probably the most intruiging aspect was that all the crewmen were located in the turret. The driver was in the turret, in a capsule that rotated to keep him orientated to the front of the vehicle [it is said that the driver would often get confused when the turret rotated anyway]. This had the effect of raising the sihouette a little, and if the contra-rotating mechanism was knocked out, it would effectively immobilize the tank. It was to include hydropneumatic suspension, stabilization system, and a NBC system. The hydropneumatic suspension allowed the vehicle to crouch or raise one end of the tank to better take advantage of hull-down positions.

Problems, however, plagued the MBT-70 program from the beginning. Difficulties with English-German translations, metric to English measurement conversions, and differences between German and American manufacturing and designing practices caused considerable headaches before the first tanks were even designed. Most of the new systems were still experimental and this led to massive cost overruns and delays. Also the joint nature of the program led to disagreements about design features.

From 1965 to 1972, the US Army conducted a parallel development program for the 152mm XM578 cartridge, which was co-developed with the prototype MBT-70 Tank. The XM578 cartridge used a tungsten alloy that was slightly denser than the British alloy, consisting of 97.5 percent tungsten and 2.5 percent binder, which had a density of 18.5 gm/cc. In response to the new operational requirements, military developers evaluated a succession of metal alloys. Initially, the British government developed a higher density tungsten alloy consisting of 93 percent tungsten and 7 percent binder tungsten alloy (WA). The new WA alloy had a density of 17 gm/cc -- versus 13 gm/cc for tungsten carbide.

Unfortunately, rising costs and technical problems caused the partners to go their separate ways. Trials began in 1968 and problems resulted in further delays and cost overruns. By 1969 the vehicle cost 5 times what was projected and as a result Germany backed out of the project. The MBT-70 program was finally halted in January 1970. The same fiscal year (1971-72) witnessed the termination of two major weapons procurement programs, one for the Cheyenne advanced attack helicopter and the other for the MBT-70 main battle tank. Although Army leaders saw both weapons systems as critical to the Army's long overdue modernization program, they were unable to convince the Department of Defense and Congress of a need for these weapons commensurate with their costs. The joint effort with the Federal Republic of Germany, under which the MBT-70 had been developed, was modified to a co-operative program in the middle of Fiscal Year 1970.

The US chose to give the MBT70 another chance, but this time as an austere vehicle with toned-down technological gizmos. This project was dubbed XM803, and it featured a less powerful engine, lacked the complex hydropneumatic suspension, and was protected by a simpler armor array than MBT70. Changes in the US design were recommended to decrease production costs and increase the reliability of the vehicle; sacrifices in combat effectiveness were minimal. In December 1969, the new program was reviewed in the Office of the Secretary of Defense and in the following month the recommended changes were approved. The design changes reduced the estimated unit cost of the tank by almost 30 percent. With the modification of the program and of the co-operative features of the engineering effort, the tank received a new designation, XM803; the composite nomenclature MBT-70 / XM-803 was used until February 1971.

The XM803, the successor to the abortive MBT-70 project, was intended to modernize the armored force. Concerned about expense, Congress withdrew funding for the XM803 in December 1971, thereby canceling the program, but agreed to leave the remaining surplus of $20 million in Army hands to continue conceptual studies. This resulted in the German Leopard II and the US M1 Abrams. The Leopard 2's powerpack was originally designed for the German prototype of the MBT-70. In 1973, cooperation between these two projects led to the adoption of the German 120mm smoothbore gun by the US.




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