After 20 years of drawings and often dashed dreams, the United States is taking concrete steps toward developing a superfast aerospace plane. A key step toward developing a space plane -- which would take off from a runway, accelerate to perhaps 25 times the speed of sound, and then climb into low-Earth orbit -- came this month when the US government awarded contracts for technical development.
The awards, worth some $400 million, cover work on propulsion systems and airframe designs. They are part of an accelerated research program to develop a new generation of aircraft, referred to variously as space planes, hypersonic aircraft, transatmospheric vehicles, or Orient Expresses (because of their expected ability to be able to fly from New York to Tokyo in two hours).
During his State of the Union message in February, President Reagan singled out the radical plane as a major priority. The administration followed up by asking for some $600 million over the next three years to explore the technology for such a vehicle.
Until now, the National Aeronautics and Space Administration (NASA) and the Pentagon have spent less than $50 million a year on space-plane technology. As much as $3 billion may be needed before a prototype can be flown, probably sometime in the mid-1990s.
``The National Aerospace Plane Program holds the key to regaining the substantial lead in aerospace once enjoyed by the United States,'' said Roger D. Schaufele, vice-president of engineering at the McDonnell Douglas Corporation, in congressional testimony last month.
The US isn't the only country interested in such technology. The British government recently said it would spend some $2.1 million over two years to design a space plane it calls Hotol, which stands for horizontal takeoff and landing.
Some in US government and aerospace circles are interested in a 300- to 500-passenger civilian transport. This hypersonic plane would be capable of flying to speeds of Mach 5, about 3,750 miles an hour. The Anglo-French Concorde cruises at Mach 2. Hypersonic enthusiasts see the jetliner as a way to link the US with far-flung trading partners, particularly in Asia, though critics doubt there is a commercial market for the aircraft.
``The technical challenges for such vehicles are formidable, and long lead times are to be expected; however, there is no question as to the feasibility of eventually achieving technology readiness,'' said Dr. Raymond Colladay, NASA's associate administrator for aeronautics and space technology, in congressional testimony last summer.
Others are interested in a true spacecraft, like Hotol, that could fly in and out of orbit. This would require a vehicle that could accelerate to orbital velocity, roughly Mach 25. The Pentagon says such a machine might make a nifty quick-reaction spy plane. It and NASA are also interested in the vehicle as a cheaper, more versatile alternative to the shuttle.
The space-plane program's visibility has, in fact, grown since the Challenger disaster last January. Although such a craft could not be built to help NASA meet its growing backlog of launch requests any time soon, some political and aerospace analysts say the US should develop the next generation launch vehicle -- be it a space plane or something else -- rather than invest more in the shuttle program.
Building a space plane will not be easy. Greg Reck, deputy director of technology for the National Aerospace Plane Program, a joint NASA-Pentagon effort, says the project ``really goes well beyond anything we have direct experience with in flight vehicles.''
A major challenge will be the engines. Engineers say a space plane would require, in effect, three propulsion systems in one. At low speeds the engine would use turbines, similar to those in a jet engine, to compress the air before it mixes with fuel in the combustion chamber. At higher speeds, the shock of air moving through the engine would itself become the compressor. Once the craft reached orbit, where there is no oxygen to sustain combustion, it would rely on rocket power.
NASA has been working on air-breathing engines, called scramjets, for many years. Under the latest round of contracts, additional work on propulsion systems will be carried out by General Electric and the Pratt & Whitney division of United Technologies Corporation.
Other contracts have gone to Boeing, Lockheed, McDonnell Douglas, General Dynamics, and Rockwell International to design the airframes. Here, too, plenty of work remains to be done -- especially on the aerodynamics and heat-resistant materials.