January 26, 2009

NASA seeks quiet supersonic flight

The U.S. space agency says it has conducted a series of flight tests that might help produce quieter supersonic aircraft.

The National Aeronautics and Space Administration said the tests measured shock waves generated by an F-15 jet to validate computer models that could be used in designing commercial aircraft that can fly faster than the speed of sound without generating loud sonic booms over land. Supersonic flights over land generally are prohibited because of such loud noises.

A sonic boom is created by shock waves that form on the front and rear of an aircraft (with) the boom loudness related to the strength of the shock waves, NASA said. The formation of the shock waves is dependent on the aircraft geometry and the way in which the wing generates lift.

During the flight tests one of two F-15s generally followed 100 feet to 500 feet below and behind the other, measuring the strength of the leading aircraft's shock waves at various distances using special instruments.

The tests were the latest in a series of NASA projects investigating effects of aircraft geometry and lift on the strength of shock waves.