Jet would skitter across globe in 2 hours

 By skipping along the top of the atmosphere like a rock skittering across a pond, a proposed new style of aircraft could fly between most points on Earth in only 2 hours, its proponents say.

 The plane, dubbed HyperSoar, could attian a hypersonic top speed of 3 kilometers per second, or Mach 10-10 times the speed of sound. It could transport freight and people, strike enemy targets, or help propel payloads into space. In most uses, it would not only go places faster but would also haul more load per kilogram of aircraft than existing planes or rockets do, says Preston H. Carter, an aerospace engineer at Lawrence Livermore (Calif.) National Laboratory.

 After developing the concept for a decade, partly in collaboration with engineers at the University of Maryland, College Park, Carter has been pitching it during the past year to the military and NASA. He hopes to find sponsors willing to pay an estimated $500 million to build a 16-meter-long unmanned prototype. A full-scale plane would be 65 meters in length, roughly as long as the wingspan of a Boeing 747, Carter says.

"It's a great airplane. It's a great launch vehicle. But it's a new airplane and new technology, and therefore everyone is being very cautious," he says.

 The aircraft, whose knife-edged profile resembles a folded paper plane, would make a conventional take-off from a standard runway, jet out of the atmosphere to a height of about 60 km, and then coast back toward Earth at a shallow angle to begin the skipping part of its flight.

 Aerodynamic lift, increasing as the descending plane meets denser air, would cause the aircraft to glance back upward at an altitude of about 35 km. The engines then would kick in briefly, helping lob the plane back up to its peak altitude. The plane would repeat its porpoise-like bobbing, with an engine-assist on each upswing, until it reached its destination. It would bob roughly every 2 minutes, subjecting passengers alternately to about 1.5 times Earth's gravity-a little more than that of a normal take-off-and weightlessness, Carter says.

 No plane has ever used a skipping trajectory, but the idea has been around for some 20 years, promoted mainly by Jason Speyer, an aerospace engineer at the University of California, Los Angeles. By regularly popping out of the atmosphere, an airplane flying faster than about Mach 8 would save fuel, heat less from atmospheric friction, and avoid creating a blanket of charged particles that disrupts radio communications, Speyer says.

 The fastest military plane, the SR71, flies at speeds of between Mach 3 and Mach 4. The commercial speed champion, the Concorde, only reaches Mach 2.

 The HyperSoar concept, which will be described in a future issue of the Journal of Aircraft, "appears to be a reasonable approach," Speyer says.

 Engineers at the Boeing Co. in St. Louis and James L. Hunt of NASA's Langley Research Center in Hampton, Va., have also proposed a hypersonic vehicle capable of both atmospheric and space use. Their Vision aircraft, unveiled in April at the Space Planes and Hypersonic Systems and Technologies Conference in Norfolk, Va., resembles HyperSoar but does not follow an undulating flight pattern.

 Carter claims that HyperSoar is superior, but Hunt says both approaches need more detailed analysis. Neither group has yet investigated possible adverse environmental effects from emissions or sonic booms, which have plagued attempts to develop slower, supersonic transport planes.