The Air Force Research Laboratory's propulsion directorate, a part of Air Force Materiel Command, is providing technical assistance to the test flight scheduled for September at Edwards Air Force Base, Calif. The bomber will fly with two of its eight jet engines using a specially blended fuel made of conventional petroleum-derived JP-8 and a Fischer-Tropsch jet fuel produced from natural gas.

Alternative jet fuels can be produced from domestically available hydrocarbon products like natural gas, coal and shale using the Fischer-Tropsch process, which was developed in Germany in the early 1920s. Gasification can convert any hydrocarbon feedstock (raw material required for an industrial process) into a synthesis gas that can then, through the Fischer-Tropsch process, be converted into any number of liquid fuel products.

The cost of using Fischer-Tropsch has been cost-prohibitive until now. Today's petroleum prices are making liquid fuels derived from the process more cost-competitive, said Maj. Timothy Schulteis, Air Force propulsion program element monitor.

"The recent rise in cost of fuel has brought us to where many think we are now at the break-even point," he said.

An additional advantage is that the United States can reduce its dependence on foreign petroleum by using domestic feedstock such as coal to create liquid fuel.

"One of the primary things we are looking at is using a coal-based fuel for aviation use," he said. "One of the big advantages of that is we have a large domestic source for coal-based fuel."

The United States has perhaps the largest reserve of coal in the world. That abundance of coal, and the Fischer-Tropsch process, could put the United States on the path to a more secure energy future.

"If there is anything you can do to increase the assured access to a fuel, that is going to be a great benefit," Major Schulteis said. "It is a national security issue to have access to fuel. The other side of that is, with an assured source, you reduce (price) fluctuations so you have stable planning and budgeting."

Since this is an experimental program, the September B-52 test flight will not run entirely on fuel derived through the Fischer-Tropsch process. While two of the aircraft's eight engines will run on a blend of JP-8 and liquid fuel derived from natural gas, the remaining six engines will run on traditional JP-8 jet fuel. The fuel derived from natural gas is virtually identical to that which could be derived from coal. The test flight is just one experiment the propulsion lab will engage in before the Air Force sees a new fuel for its aircraft.

"This is kind of the initial step, (to say) we have proven we can fly it on an aircraft," Major Schulteis said. There are many issues to go through for the certification and qualification effort.

Air Force engines are specially designed to work with the current blend of JP-8 the service purchases. That fuel is held to high standards so it doesn't damage the engines it runs in. Any new fuel that goes in Air Force engines would have to meet similar criteria, Major Schulteis said.

Jet fuels produced via the Fischer-Tropsch process are chemically similar to petroleum-derived fuels. The propulsion directorate is conducting experiments to assure the fuel is fit-for-purpose for use in aircraft and will conduct tests to demonstrate engine performance, high-temperature stability, low-temperature properties and compatibility with aircraft systems

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