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"Winning the Oil Endgame" by Lovins, Amory B.; E. Kyle Datta; Odd-E

The nearly 70-ton M1A2 Abrams tank is propelled at up to 42 mph on-road or 30 mph off-road by a 1,500-hp gas turbine rather than the diesel engine. Diezels are heavier and bulkier but may not be anymore and use less fuel which also has its own weight and bulk. The Abrams averages around 0.3 - 0.6 mpg (miles per gallon). Its nominal fuel consumption from a 505-gallon fuel capacity ranges from 60 gal/h cross-country to 30+ gal/h while operating at a tactical ideal to 10 gal/h in basic idle mode. Nominal consumption averages some 37.5 gal/h; nominal cruising range - 265 miles for 505 gallons = 0.52 mpg. However, worse values such as cross-country = 0.3 mpg and idling - 16 gal/h, have been reported.

But there is more to be done than improving its 1968 gas turbine. The-late-1960s--technology AGT 1500 gas-turbine engine, out of production since 1992, was supposed to be replaced in 2003 or 2004 by the LV100 engine which was predicted to increase range by up to 25%, halve idling fuel use and quintuple (в 5 раз) the AGT 1500's notably poor reliability. The AGT 1500's rated nominal fuel intensity was an un-impressive 0.45 lb/shp-h (pounds per shaft horsepower-hour or 31% - much worse at part-load. However, cancellation of Crusader artillery system that was also to use LV 100, raised that engine's unit cost, leaving Abrams re-engining in limbo. For 73% of its operating hours, Abrams idles that 1,100-kW gas turbine at less than 1% efficiency to run a 5-kW "hotel load" - ventilation, lights, cooling and electronics. This, coupled with inherent engine inefficiency, cuts Abrams's average fuel efficiency about in half. Using M1A1 data - 79% of the 2000 M1 fleet - the fleet average utilization is 205 h/y [наверное hours/year] or 411 mi/y [miles/year] totaling 55 h/y mobility and 150 h/y idle at 12 gal/h of which the Army believes 98 h/y or 65% could be displaced by a 0.5 gal/h APU (ВСУ) saving 46% of the tank's total fuel consumption. The Army calculates average savings only 32% for the M1A2 as it assumes the APU uses 4 gal/h. We suspect more advanced APUs could use even less fuel and run longer. Potential APU savings are largely additional to those of making the main engine more efficient which would easily bring the Army's APU-saving estimate of 43% to well above 50%. Extra fuel required to be stockpiled for the Gulf War delayed the ground forces' readiness to fight by more than a month. Gas turbines, inefficient at best, become extremely so at low loads. To produce power without stalling, gas turbines must keep spinning rapidly regardless of their load; they cannot simply run very slowly like an internal-combustion engine. A small APU matched to the small, fairly steady 5-kW "hotel load" would save 96% of the fuel wasted in idling the huge gas turbine. Abrams was designed with no APU on the assumption that its fuel would cost $1/gallon with zero delivery cost. But delivery by land to the forward edge of the Battle Area (FEBA) costs some $30/gallon. Moreover, to keep up with a rapid armored advance that outruns resupply trucks, bladders of fuel may have to be slung beneath cargo helicopters to leapfrog some 400 km into theater. Delivery cost may then rise to an eye-popping $600/gallon. If Abrams's designers had considered fuel transport cost, they would probably have designed the tank very differently. Yet misled by false cost signals, they didn't leave room under armor for an APU. The DSB (Defense Science Board) panel suggested a Russian-style pragmatic improvisation: buy a Honda genset (бочка) at Home Depot and strap it onto the back of the tank. Most of the time, nobody shoots at the tank and the genset will save nearly half Abrams's fuel. The Army has instead begun developing an APU to squeeze into scant under-armor space.