Sunday, December 17, 2006

Limits To US Military Superiority - 2

The US Air Force Refueling Capability

It takes fuel to deliver fuel and fuel use imposes large logistical burdens.

While numerous US military aircraft provide refueling services, the bulk of refueling capability lies in the Air Force fleet of 59 KC-10 and 543 KC-135 aircraft, or aerial refuellers.[1] The KC-10 aircraft are relatively young, averaging about 21 years in age, whereas average age of KC-135s is 44 years. This was the main reason a GAO report[2] in 2003 recommended recapitalizing KC-135 fleet will be crucial to maintaining aerial refueling capability, and also noted that that will be a very expensive undertaking.

It is therefore no surprise that General T. Michael Moseley, Chief of Staff of the Air Force, announced in October 2006 that KCX tanker is the Air Force's new number 1 procurement priority, followed by CSARX (the new combat rescue helicopter), space based early warning and communications satellites, the F35, and the next generation long range strike. According to a New York Times article on October 13, 2006 (Air Force seeks $13 billion to start replacing tankers) Air Force is seeking $13 billion over the next five years to replace their aging fleet of aerial refueling aircraft.

How Alternative is Alternative Fuels for Air Force Fleet?

A recent NASA report[3] to investigate the feasibility and assess the impacts at the airplane level of using alternative fuels argues that “although we are not going to run out of crude oil anytime soon, alternative energy sources need to be developed quickly to help address the end of cheap oil.”

The report concludes that the only currently known drop-in alternative jet fuel was synthetic fuel. As jet fuel requires high-performance characteristics, it makes more sense to use higher performing synthetic fuels in aviation. It also tends to be cleaner than crude-oil-derived Jet-A.

Aircraft biofuel requires an additional processing step to address fuel-freezing issues. Biofuel would need to be mixed at a maximum 20% ratio to avoid stability issues over time. Regular bio-diesel fuel freezes at the cold (i.e., –20 °C) operating conditions of aircraft. Because synthetic jet fuel and bio-jet fuel have approximately the same weight, volume, and performance characteristics of current oil-derived jet fuel, they would be relatively easy to use and not affect the design of the airplane.

But one of the biggest problems with biofuels is their negative energy balance from the EROEI point of view. Besides that there is the area requirement for production of raw material. As indicated in the report “in 2004 the U.S. commercial fleet used about 13.6 billion gal of jet fuel. A 15% blend of bio-jet fuel would require 2.04 billion gal of this fuel per year. A crop, such as soybeans yielding about 60 gal of biofuel per acre, would require 34 million acres of agricultural land, about the land size of the state of Florida.” Similar problems exist for switchgrass even though 1 acre switchgrass yields 500 gallon ethanol. In addition, “biofuel appears to be better suited for ground transportation, whereas synthetic jet fuel is ideally suited for aviation.”

Aircraft fuels need to have high energy content per unit weight and volume. Hydrogen-powered airplanes need a larger tank, which reduces the fuel efficiency of short-range aircraft. Liquid Hydrogen could be preferred only for a long range flight. Ethanol takes up 64% more room and weighs 60% more compared with Jet-A fuel. An ethanol-fueled airplane requires a larger wing and engines, thus reducing the airplane’s fuel efficiency.

Now let me introduce an official statement: Air Force’s goal is to have a 50% of its aviation fuel come from alternative fuel sources by 2016 (through synthetic fuels). Smile, if you wish…

Conclusions for Limits to Air Force Military Superiority

The US Air Force is the world’s dominant source of air and space power.

Even though its fleet is ageing (average of 23 years for active fleet) its number and quality cannot be matched by any other air force in the world. But a separation between wants and wishes versus utility and needs must be carried out in deciding any transformation process and in acquiring new technologies under the framework of future foreign and national security strategies. The reports I so far read conclude that the USAF will have to leverage space-based weapons systems and unmanned aerial vehicles at the expense of manned aircraft. Size is necessary but not a sufficient condition.

Deputy Defense Secretary Gordon England recently noted that the greatest long-term threat to the US is not weapons of mass destruction, but rather the prospect of losing strength in science and technology.[4] The Defense Advanced Research Projects Agency (DARPA), the central research and development organization for the DoD, plays a major role in maintaining the technological superiority.

This superiority that rests upon a technological base requires enormous quantities of oil. DARPA’s first ever hands off autonomous air refueling operation as well as its aviation biofuel research (in the context of its BioFuels program) to develop alternative fuels will surely help. But I am afraid the use of it will rather be limited and not widespread.

Fuel efficiency and longer range strike capabilities are put forward by the Air Force officials as important features of future fleet. Despite its energy-saving technologies[5] and efforts to reduce oil consumption, the Pentagon is not likely to reduce its oil dependency. As its worldwide adventures continue its oil use and hence dependency will go nowhere but up.

[1] These are large, long-range aircraft that have counterparts in the commercial airlines, but which have been modified to turn them into tankers. The KC-10 is based on the DC-10 aircraft, and the KC-135 is similar to the Boeing-707 airliner. For detailed descriptions, see, Gallery of USAF Weapons in 2006 USAF Almanac.

see part 1: Limits To US Military Superiority - 1


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