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Alternative Aviation Fuel Experiment

NASA and 11 other research groups tested two non-petroleum-based jet fuels in the pursuit of alternative fuels that can power commercial jets and address rising oil costs.

The tests, run at NASA's Armstrong Flight Research Center in California, measured the performance and emissions of two synthetic fuels derived from coal and natural gas using the Fischer-Tropsch process. These fuels have drawn attention because they have the energy necessary for commercial flight.

The Fischer-Tropsch process is a chemical reaction in which a synthesis gas -- a mixture of carbon monoxide and hydrogen -- is converted into liquid hydrocarbons of various forms. The process produces synthetic petroleum for use as a lubricant or fuel.

A DC-8 based at Armstrong in Edwards, Calif., was the test vehicle because its engine operations are well-documented and well-understood. The airplane remained on the ground for the tests, which used one fuel made from natural gas and one from coal. Researchers tested 100 percent synthetic fuels and 50-50 blends of synthetics and regular jet fuel.  The tests specifically sought to establish fuel matrix effects on: 1) engine and exhaust gas temperatures and compressor speeds; 2) engine and auxiliary power unit (APU) gas phase and particle emissions and characteristics; and 3) volatile aerosol formation in aging exhaust plumes.

The tests were carried out using sampling probes placed downstream from the DC-8's right inboard engine. Researchers examined the plume chemistry and particle evolution to compare it to that of standard jet fuel.

NASA is one of many organizations working to understand how non-petroleum alternatives may be used to satisfy the growing demand for less expensive, cleaner burning fuel for aviation.

The AAFEX tests are funded and managed by NASA's Fundamental Aeronautics Program, which is part of the agency's Aeronautics Research Mission Directorate in Washington, D.C. The participating research groups include three other government agencies, five companies and three universities.

AAFEX took place at NASA Armstrong in Palmdale, California, from January 19 to February 3, 2009