The U.S. Army’s sole class of main battle tank the M1 Abrams, which has served since 1980 and remains one of just two Western tank classes in production today, has seen renewed attention drawn to its capabilities after the announcement that the vehicles would be provided as aid to the Ukrainian Armed Forces. Recent contracts to export the vehicles to Poland and Taiwan, both of which sit on the frontiers with Russia and the Chinese mainland respectively, previously also raised the Abrams’ profile, as did a proposal by General Dynamics Land Systems in late 2022 to develop a radically improved next generation variant, the AbramsX, with an autoloader and unmanned turret which would reduce crew requirements to three – thus mirroring prior developments with Chinese, South Korean and Russian tanks. Transfers to Ukraine have raised questions as to whether the Abrams is suitable for the war-torn state’s armed forces due to its particularly high maintenance needs and fuel consumption, and have drawn attention to the trade off made by the decision to integrate a Honeywell AGT1500 gas turbine engine onto the tank rather than a traditional lower maintenance diesel engine. Questions regarding the efficiency of turbine engines has in turn recalled both the debate in the Soviet Union surrounding its own gas turbine powered tank class, the T-80, as well as the development of an experimental Abrams tank using a diesel engine in the 1990s by General Dynamics Land Systems.
Development of a diesel engine Abrams variant first began in 1997, and was used to pitch the tank for export, with the benefits of considerably easier and less time consuming maintenance and far cheaper production. The Soviet T-80 tank which first entered service 1976 pioneered the use of gas turbine engines, the GTD-1000, but largely as a result cost well over three times as much as the preceding T-64 tank of similar size. The GTD-1000 facilitated a sustained high speed travel much better than diesel engines on the T-64, making them particularly highly prized for deployments to East German for a potential push across Western Europe at speed, with faster acceleration paired with greater quietness and a far faster startup time in conditions of extreme cold compared to diesel engines. Nevertheless their extreme costs, over ten times as expensive as equivalent diesel engines, and the ability of diesel-powered T-72s to travel close to four times as far in between maintenance largely due to the engine discrepancy, led the Defence Ministry to begin exploring options for diesel powered T-80 variant.
The discrepancy in cost and efficiency favouring diesel powered tanks led to the development of a cheaper diesel-powered T-80 variant, the T-80UD, which entered service in the late 1980s. Several hundred were built before the Soviet Union’s disintegration ended the program. The manufacturing Malyshev Factory’s location in Ukraine meant it could not remain operational without support from the industrial base in Russia after the two states’ separation, while in Russia itself gas turbine powered T-80s were largely phased out of service. Those that remained operated primarily in the Arctic where their capabilities were highly suitable for the climate there. The bulk of diesel powered T-80UDs were inherited by Ukraine, but were sold to Pakistan in the late 1990s leaving its army to rely on the much older and less capable T-64 – which remains the case today. Many of the attractions of the T-80UD over other T-80 variants similarly applied to the Abrams program.
In the case of the Abrams the MT-883 V12 diesel engine was found in testing to provide equal levels of mobility and “no difference in target detection, identification or main gun accuracy,” with tests confirming “that the tank’s performance is not changed by the diesel engine and that it has a significantly lower operating cost.” Gas turbine engines nevertheless continued to be used, although had foreign clients specifically requested a diesel engine then such an adaptation could have potentially materialised. A second attempt by General Dynamics Land Systems to integrate a diesel engine began in 1999 using the new AVDS 1790 V12, and according to the Armor journal it would provide “the same power as the gas turbine … will deliver a 50-percent increase in cruising range through enhanced fuel efficiency and a 37 percent reduction in maintenance costs owing to greater simplicity and higher commonality with commercial diesel engines.” This too was never adopted, although General Dynamics continued to persist in seeking alternatives to turbine engines culminating in the integration of a hybrid diesel-electric propulsion system onto the 2022 AbramsX proposal. Again, however, it appears to have failed to gain the Pentagon’s attention.
The closest thing to a success in gaining orders for a diesel powered Abrams variant was the South Korean Hyundai K1 program, which was closely derived from the American tank, developed with considerable support from Chrysler, and first produced a vehicle for active service in 1987. The vehicle had comparable mobility and a much lower operational cost, and would see over 1500 built, although it was prevented from being marketed to compete with the original Abrams for export due to the nature of the technology transfer contracts. With Abrams tanks not deploying in anything resembling the extreme Arctic conditions which Russian T-80 tanks are primarily used in, the lack of a diesel electric variant over 30 years after the end of the Cold War has not only imposed very significant costs both on the U.S. Army and on the vehicle’s many foreign clients, but has also limited the viability of the vehicle for the Ukrainian Army – which is expected to find the German Leopard 2 and British Challenger 2 much more practical to operate.