It costs $10,000 to loft just one pound of payload into orbit with a conventional rocket. A "scramjet"— an air-breathing jet engine with the potential to hit velocities 25 times the speed of sound— could slash the cost to hundreds of dollars per pound. But no vehicle has ever successfully flown under scramjet power. aircraft or boosting the next-generation space shuttle by 2025.
That's set to change in June, when NASA plans to test its Hyper-X. Two weeks later, a team from Australia's University of Queensland plans to fly a scramjet of its own. Like conventional jet engines, scramjets pull in air and compress it; then they add fuel, ignite it, and blow the high-pressure exhaust out the back. "But unlike jet engines, scramjets use only the vehicle's forward motion and the engine's geometry to compress the air," says Randy Voland of NASA's Langley Research Center in Hampton, Virginia, who manages the Hyper-X project. "They have higher efficiency and higher speed." aircraft or boosting the next-generation space shuttle by 2025.
NASA's Hyper-X will use air-breathing engines for a cheap ride into space.Photo by NASA
Scramjets operate only at supersonic velocities. So both of the prototype engines will first be accelerated up to Mach 7 with small sounding rockets. Then the engines will switch on for a few seconds to prove they work. Because they need to pull oxygen from the air, scramjets can't operate in a vacuum. "To insert a vehicle into space, the scramjet must be shut down and a small rocket turned on," Voland says. He thinks scramjets could be propelling hypersonic aircraft or boosting the next-generation space shuttle by 2025.
