After six years of work, the US Air Force Research Laboratory has successfully flown a test-rig pulse-detonation engine at Mojave airport in California. The just-announced test flight took place on January 31.

The engine is purely experimental, an assembly which (at least when I saw it in 2003, at Oshkosh) included major pieces of an Oldsmobile Quad 4 auto engine. The goal was to demonstrate that the engine could be made to run with acceptable qualities and enough thrust to sustain flight, and that noise levels would be tolerable. Pilot Pete Siebold - one of Burt Rutan's Scaled Composites team - used a rocket to assist take-off with the modified Long-Eze, but shut the rocket down to complete the flight.

The announcement coincides with the start of DARPA's Project Vulcan, aimed at ground-testing a full-scale zero-to-Mach 4 propulsion system combining a conventional fighter engine with a pulse-detonation or constant-volume augmentation system. Program manager is Tom Bussing, a pulse-detonation advocate who worked on the technology with Adroit Systems in Seattle. (Adroit sold that unit to Pratt & Whitney in 2001.)

Pulse-detonation engines have been linked to secret-airplane eyewitness reports, but - unless the secret world is 20 years ahead of everyone else - the technology hasn't reached the operational stage yet. Also, the low-frequency surging sounds in some ear-witness reports don't match the cycle rate - 80 Hz for the Mojave experiment - associated with these engines.

pic credit:  USAF. Title credit, Lulu