IT LOOKS MORE LIKE A FLYING saucer than a sleek spaceship. It will be powered by silent microwave beams instead of roaring rockets. And its airframe is essentially a helium-filled dirigible. Despite these unconventional features, the aerospace craft being developed at Rensselaer Polytechnic Institute isn't mere science fiction.
Last month, Rensselaer's "air spike" propulsion system passed a Mach 10 wind-tunnel test with flying colors. That's only half the speed needed to get into space, but Leik N. Myrabo, the RPI associate professor of mechanical engineering who heads the research team, is confident the principle is valid for craft that could ferry tourists to the moon in six hours--or business travelers from New York to Singapore in 45 minutes.
The air-spike system works by funneling microwave energy to a spikelike antenna. Its tip generates shock waves that blast away the air in front of the saucer, creating lift to suck the airframe forward. But the real action comes when the shock waves collapse back around the rim of the saucer, forcing hypersonic air into the intakes of a special jet engine. No heavy fuel is carried because the jet burns electricity--beamed in as microwaves from high-power transmitters on the ground or in space. If the wind-tunnel results at RPI attract more funding, says Myrabo, 21st century travelers may literally ride on energy-beam highways in the sky.