September 11, 2002. Copyright 2002. Graphic News. All rights reserved.

Hyper-jet could skim across globe in two hours

LONDON, September 11, Graphic News: A trip from Chicago to Tokyo could be just a hop, skip, and jump with a new hypersonic aircraft designed by researchers at the Lawrence Livermore National Laboratory in California.

The HyperSoar concept has been just a paper plane for the last four years, but now the U.S. Defense Advanced Research Projects Agency (Darpa) appears ready to lift the concept off the drawing board toward a $350 million spaceplane demonstrator.

HyperSoar could fly at 6,700mph (10,782 km/h) or Mach 10, and operate primarily at altitudes of 115,000-200,000 feet (35,000-61,000 metres) while carrying roughly twice the payload of subsonic aircraft of the same take-off weight, said Livermore National Laboratory aerospace engineer Preston Carter, developer of the HyperSoar concept.

The 213-feet-long (65-metre-long) aircraft (about as long as the wingspan of a Boeing 747) could make a conventional take-off from a standard runway. Using special, air-breathing, hydrogen-fuelled engines, it would ascend 25 miles (40 kilometres) above the ground -- to the outer limit of EarthÕs atmosphere. 

Once there, its engines would be turned off, and it would coast under its own momentum up to a high point of 37 miles (60 kilometres) before beginning to fall back down to about 22 miles (35 kilometres) -- well inside the atmosphereÕs upper level. As it descends into denser air, the aircraft would be pushed up by the increased aerodynamic lift. The engines would fire briefly, propelling the plane back into space. 

Outside the atmosphere, the engines shut down and the process is repeated. In this way, HyperSoar would skip off the top layer of the atmosphere every two or three minutes, like a flat rock skittering in slow motion across the surface of a pond.

Including the time taken and distances covered by the ascent and descent portions of a flight, a trip from Chicago to Tokyo (6,300 miles, 10,120 kilometres) would involve about 18 skips and take 72 minutes, and to travel from Los Angeles to New York (2,470 miles 3,980 kilometres) would involve about 5 skips and take 35 minutes.

By popping regularly out of the atmosphere and using the rocket-based, combined-cycle engines intermittently, HyperSoar would use less fuel and solve a critical problem that plagues other hypersonic aircraft designs -- heat build-up.

All objects -- aircraft, spacecraft or asteroid -- speeding through the atmosphere compress and heat the air in front of it. This heat is inevitably absorbed by the surface of the object. 

ÒHeat build-up just kills most designs for hypersonic aircraft,Ó said Carter. ÒThe hotter the craft gets, the more material engineers add to the airframe to strengthen and shield it.Ó 

Carter and colleagues at the University of Maryland have analyzed HyperSoar, compared it to other concepts, and found that -- thanks to its trajectory and shape -- it has less heat load on its airframe and consumes less fuel.

The spaceplane has garnered interest from organizations as diverse as Federal Express, the U.S. Strategic Air Command, and NASA, which sees HyperSoar as the first stage of a two-stage-to-orbit space launch system. 

A bomber version would be able to carry almost 100,000lb (45,350kg) of payload on a 6,200-mile (10,000-km) mission radius. The concept, at other times, is being envisioned as a rapid response reconnaissance system or a future airlifter. U.S. Air Force officials have had a long-standing interest in the project.
/ENDS

Sources: Aviation Week & Space Technology, Lawrence Livermore National Laboratory