After Combustion: Detonation!

Photograph by C. Morlinghaus SOUND & FURY
GE's pulse-detonation test rig, ready for firing. Is this the engine of the future? Photograph by C. Morlinghaus

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At first glance, the engine bolted to the test stand looks like an unlikely candidate to lead an aerospace revolution. Its size is unimpressive: At about four feet long, it's dwarfed by the machinery that feeds it air and fuel, machinery that fills a house-size structure at the China Lake Naval Air Warfare
Center in California. And its appearance is unremarkable: This machine has none of the grace of the high-bypass turbofans that power modern jetliners, with wide, sweeping inlets and delicate blades. From the outside, it's simply a collection of metal tubes, one large cylinder feeding into five smaller ones terminated by convex, barnacle-shaped nozzles.




But Gary Lidstone and Tom Bussing have bet that this little aircraft engine-the most advanced expression yet of a revolutionary concept called pulse detonation-could absolutely bury all those that have come before it. Lidstone is the manager of propulsion programs for Pratt & Whitney's Seattle Aerosciences Center, and Bussing is his boss and the creative force behind the device's design. Here at China Lake, standing in the desert heat, the two survey their handiwork like proud papas, explaining how it has taken years to show that the concept behind this engine can open up an entirely new world of jet propulsion. "There's a big payoff," Lidstone says. "It's a paradigm shift that could make other things obsolete."




Indeed, Lidstone's team is hardly alone in its quest. In the past 10 years, the promise of the technology-a promise of a propulsion system far simpler than today's turbofans and capable of operating across a much wider velocity range, powering aircraft from takeoff to Mach 4 with ease-has touched off an explosion of interest at university, military and NASA research centers, and in labs as far away as Japan, France and Russia. In just the past three years, the two companies that stand to gain or lose the most from the rise of a revolutionary, market-disrupting jet-engine technology have begun to invest heavily in pulse-detonation engine (PDE) research. In January 2001, Pratt & Whitney bought the company Bussing had created to develop his concepts. That same year, General Electric designated pulse detonation a top priority. Arriving late in the game but armed with a new approach that could trump Pratt & Whitney, GE began plowing resources into building a PDE development team at its Global Research Center in upstate New York. "We see pulse detonation throughout our entire product line," says Harvey Maclin, manager for advanced technology, marketing and government programs at GE Aircraft Engines and one of the early sponsors of pulse-detonation research at GE. "That's why we're so interested in it."




For decades, these two companies have been battling for supremacy in the global jet-engine arena, exploiting any advantage that might give them an edge in the struggle for civilian and military market share. But those advantages have grown smaller as conventional jet-engine performance edges closer to the limits of thrust-to-weight ratios and fuel efficiency. Pulse-detonation technology offers a chance to escape from this spiral of diminishing gains and score a big win-not to mention the first lucrative corporate and military contracts. Those contracts could be for superefficient engines for subsonic jetliners, which would chop fuel consumption by an amount that engineers would "kill their grandmothers" to get, Lidstone jokes, or for supersonic, unmanned aerial vehicles or manned fighters. We could also see a supersonic airliner that's much cheaper and more practical than the recently grounded Concorde. Pulse detonation would also offer cheaper access to space, saving tons of liquid oxygen and fuel by powering vehicles from the ground to high altitude and hypersonic velocity, where conventional rocket engines would take over to lift them into orbit.