USFA Tests a New Synfuel Blend

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Air Force scientists are looking for cleaner, more efficient ways to fuel the military’s aircraft. USAF officials have declared on several occasions that "The Air Force is committed to reducing our reliance on foreign oil." To this end, USAF is closely cooperating with industry as part of a consortium of commercial airlines and engine manufacturers, called the Commercial Aviation Alternative Fuels Initiative, hoping that production economies of scale will make biofuels affordable, on par with petroleum-based jet fuel. The USAF goal is to switch half of its continental jet fuel requirement to alternative fuels by 2016. A short-term goal is to have all Air Force aircraft certified to fly using alternative fuels by 2012.

Hydrotreated renewable jet fuel, or HRJ (created from animal fats and plant oils), along with synthetic paraffinic kerosene, is one of the alternative fuels that USAF is pursuing to pave the way toward a “greener, energy independent” future.

An A-10C Thunderbolt II ground-attack aircraft (see specs) on 25 March 2010 became the first aircraft to fly running on a new 50-50 blend of traditional JP-8 fuel and a biomass-derived hydrotreated renewable jet fuel during a test sortie from Eglin AFB, Fla. (see video)

Test pilot Maj. Chris Seager, is reported to have “no problems whatsoever" with the aircraft running on this blend after the flight along the coast of Florida. The fuel used for the demonstration was from the camelina plant, a weed-like plant similar to soybean and mustard that needs little to flourish and is not used as a food-source. According to Alternative Fuels Certification officials the refining process as well as the emissions of the fuel is cleaner than conventional fuels (AFMC report by Samuel King Jr).

In a period of five days, a total of 2400 gallons of fuel was used for ground tests and the flight test (1200 gallons of the actual HRJ biofuel blended with another 1200 gallons of JP-8 to create 2400 gallons synfuel blend). For the first phase of certification for the HRJ fuels, USAF bought 100,000 gallons of the new product of camelina, and 100,000 for the tallow-based fuel from a number of different manufacturers. (see DoDLive Bloggers Roundtable: U.S. Air Force Jet Making History)

According to Tim Edwards, a senior chemical engineer with the Air Force Research Laboratory’s propulsion directorate “The way we look at it is to figure out what fuels make the most sense from an aviation industry perspective -- which ones have the potential to make the most fuel the most affordably with the least environmental impact,” including lifecycle greenhouse gas footprints and other factors. One such refinery is being built by Tyson/Syntroleum in Geismar, Louisiana that's going to take animal fat from Tyson's operations down there and make either -- HRJ jet fuel or a green diesel fuel and will use animal fats from its food production factories to create biomass fuels. And another company, called AltAir Fuels, is building such a plant near an existing refinery in Washington state. It turns out the primary cost comes from feed stock; the processing isn’t all that expensive.

A-10 aircraft testing the synfuel blend.

Source: AFMC

A second feasibility demonstration of the same blend will be made on an F-15 Eagle flight this summer to test performance parameters. Later this year a C-17 Globemaster III will be tested because of the amount of fuel it consumes, and an F-22 Raptor test is planned because of the aircraft's complexity.

As far as I understand, USAF won’t be using one type of synfuel. I mean it will not rely on solely one feedstock. Instead, depending on the availability of the feedstock used to produce the synfuel in different parts of the US, and hence it will have different synfuel blends. So, my naïve question is: Are different synfuel blends fully compatible?

I have some other technical questions that so far remain unanswered. Let me ask them by giving the A-10 synfuel test as an example. Assume that you use 1000 gallon of HRJ biofuel and 1000 gallon of conventional JP-8. You have 2000 gallons of synfuel blend.

1. How much space this 2000 gallons synfuel blend would occupy in aircraft fuel tanker compared to 2000 gallons of conventional JP-8?
2. What is the distance you could fly (in terms of miles) with 2000 gallons of synfuel blend compared to 2000 gallons of conventional JP-8?
3. Or let me combine the previous two questions into one. What would be the range and flight time (in miles and hours) if all the fuel tankers in the aircraft would be filled with synfuel, compared to conventional JP-8? And what would be the fuel costs in each case?
4. Would aerial refueling (say by using KC-135 or KC-10, or KC-X if you wish) be possible, safe, and effective?
5. Will it be possible for the same aircraft to make frequent switches between synfuel to conventional JP-8? Would the fuel switch cause any long term impact in the fuel tanker or in the engine of the aircraft?