THE 10,000-MPH AIRLINER Aviation stands on the threshold of a new giant leap: hypersonic flight. Aerospace and other companies are hard at work and could have planes flying as early as 1993.
By Gene Bylinsky REPORTER ASSOCIATE Alicia Hills Moore

(FORTUNE Magazine) – AROUND THE COUNTRY wind tunnels are rumbling, computers whirring, construction workers expanding test buildings. From NASA's Langley Research Center in Virginia and Edwards Air Force Base in Southern California to the design centers at Boeing in Seattle and Pratt & Whitney in West Palm Beach, scientists and engineers are burning with an excitement not seen since the heady days of the Apollo program that put men on the moon. Many aeronautical designers are postponing retirement, and hundreds of others are trying to get into the act. Ron Samborsky, project manager at Aerojet TechSystems in Sacramento, a subcontractor, echoes the experience at participating companies, laboratories, and research centers: ''Hardly a day goes by without a request from someone to be transferred to this program. I wish I could take them all.'' The cause of the excitement: hypersonic flight, which by most definitions begins around 3,800 miles per hour. Achieving it, many experts believe, will launch a revolution in military and civilian aircraft as far-reaching as the one the jet engine produced. If their promise turns into reality, these so- called aerospace planes will come in a variety of sizes, shapes, and functions. They will reach unheard-of speeds: Some will zoom into orbit at 18,000 mph, 25 times the speed of sound, and crease the edge of space 350,000 feet above the earth. That's nearly ten times as fast and more than three times as high as an airplane has ever flown. The earliest experimental aerospace plane, the X-30 in the foreground of the painting at right, could fly as soon as 1993. But the version of greatest interest to the jet-lagged traveler is the passenger-carrying Orient Express, so named because it could cross the Pacific nonstop in two hours. Shown , shortly after takeoff in the painting, it would cruise at up to 10,000 mph, or about Mach 14 (Mach 1 is the speed of sound, 760 mph at sea level), and have a range of 8,000 miles. The British-French Concorde, by contrast, is downright sluggish and short-legged, with a speed of just 1,350 mph and a range of 3,800 miles. Putting the world's major cities in easy touch with each other -- New York to London in just over an hour, Paris to Sydney in about three hours -- the Orient Express will take off with a roar not much different from that of today's jetliners. But its climbing angle will be steeper, pushing passengers back in their seats and subjecting them to pressure not unlike that felt by the driver of a hot sports car flooring it from a standing start. Does that mean that a grandmother or someone with heart disease could not fly aboard this dream machine? Not at all, according to experts. At the cruising altitude of 100,000 feet, twice that of the Concorde, passengers will have no sensation of speed, since they will be too far above clouds and geographical features to perceive the plane's motion. Designers may sacrifice such niceties as individual windows to save weight, substituting small liquid crystal screens connected to external closed-circuit TV cameras. A single large viewing window might be installed as a concession, however. Through it the passengers could see, say, the California coast from San Francisco Bay to San Diego and, above, layers of the earth's atmosphere shading from blue into the deep black of space. One thing will probably remain unchanged. Says former test pilot A. Scott Crossfield, 65, who made 30 flights into the stratosphere aboard the X-15 rocket plane: ''You have breakfast in New York and tomorrow night's supper in Peking because you have crossed the international date line. You fly back and have tonight's supper in New York. Meanwhile, your bags go to Rio.'' Whether the Orient Express ever flies will depend on the success of the National Aerospace Plane Program, which is gathering speed. The first hypersonic plane, the X-30, would be about the size of a DC-9 airliner and a third as large as the Orient Express. Seven years from now, if the schedule holds, two test pilots will take off from a conventional runway in the X-30 and zoom to about 200,000 feet at 18,000 mph. Novel air-breathing engines will carry it to that lofty plateau. Then rocket engines using conventional liquid hydrogen and liquid oxygen fuels would ignite, sending the X-30 into orbit. ; After completing its mission in space, it would reenter the atmosphere just as the shuttle does and land on an ordinary runway. IN THAT COMPLEX FLIGHT, the X-30 will serve as the test bed for a whole new flock of different hypersonic aircraft. To make them possible, government labs and commercial aerospace and engine companies are rapidly developing a sunburst of new technologies: propulsion systems, materials that will withstand the searing heat of those mind-boggling speeds, and airframes that combine, in effect, a huge f1ying thermos bottle containing supercold hydrogen that will both cool the plane's surfaces (some heated to 5,000 degrees F., half as hot as the surface of the sun) and fuel its furnace of an engine.

First will come a full-fledged orbiting aerospace plane based on the X-30. Such a craft could serve as a successor to the space shuttle and a truck to haul components of the Strategic Defense Initiative, or Star Wars, into orbit. The aerospace plane could cut the cost of flights to orbit to a tenth of those of the shuttle. At some distant date it could even be used as a civilian transport, taking passengers on pleasure trips to space station hostels like the futuristic Howard Johnson's in 2001: A Space Odyssey. The second version of the aerospace plane could become a potent new U.S. weapon. Capable of zipping along near the top of the atmosphere at speeds approaching 18,000 mph, it would be the most elusive spy plane ever built, or a fast-response fighter-bomber that could fly anywhere on earth in about two hours. Fleets of such military craft could be airborne by the end of the century -- just 13 years from now. Reflecting the importance the military places on the aerospace plane, the Defense Department is picking up 80% of the development tab for the X-30, NASA the remaining 20%. Finally the civilian Orient Express would emerge, possibly leapfrogging any successor to the supersonic Concorde. It would actually be technically simpler to build than the earlier planes, since it would not need to reach orbit or fly faster than 10,000 mph. The Orient Express will be designed and produced not by the government but by aircraft builders such as Boeing, Lockheed, and McDonnell Douglas, which are already conducting preliminary studies. Development could start years before any military aerospace plane flies. A propulsion system that works at those lower speeds could be peeled off along the way to perfecting more complex engines for an orbital aerospace plane. First, though, comes the awesome challenge of building the X-30, the test vehicle for the combination orbiter-hypersonic airplane. ''The danger we face is promising too much,'' says Robert M. Williams, 42, director of the program and an intense aerodynamicist at the Pentagon's Defense Advanced Research Projects Agency (DARPA). His deputy, Air Force Brigadier General Kenneth E. Staten, 47, echoes his boss: ''We know there are risks. There will be disappointments, setbacks, even failures.'' Some critics feel that the aerospace plane managers may have bitten off too big a slice of an untried high-tech cake. Willis M. Hawkins, 72, a retired senior vice president of Lockheed and now a consultant to the company, suggests that the aerospace plane could come a cropper because the requirement that it attain orbit will add severe weight and propulsion problems. A veteran of Lockheed's fabled Skunk Works, where such remarkable spy planes as the U-2 and the SR-71 Blackbird were developed, Hawkins would have been happier if program managers had settled for a hypersonic plane that did not have to reach orbit. The idea of an aerospace plane is not new. In the early 1950s the U.S. Air Force experimented with various programs, including Dynasoar, a shuttlelike craft that would have been rocketed into space to return like an airplane. The closest anyone came was the X-15. Dropped from beneath the wing of an airborne B-52 bomber, it made 250 flights, briefly attaining hypersonic speeds approaching 4,500 mph and flying as high as 354,000 feet. The Air Force had plans to turn the X-15 into an orbiter, but the shift to earth-to-orbit rocket-based space exploration in the 1960s put all those aviation developments on the shelf for more than 25 years. The fastest, highest-flying airplane today -- the Air Force's SR-71 Blackbird spy plane, which reaches speeds of 2,100 mph and altitudes of 80,000 feet -- is now 25 years old. The Concorde first flew in the late 1960s; the U.S. plan to build a bigger, faster SST died in 1971 because of concern about ear-shattering sonic booms and potential damage to the ozone layer in the atmosphere that protects life on earth against cosmic radiation. (The Concorde flies below the ozone layer. Its sonic booms have confined it to over-the-ocean routes, making it a technological, but not a commercial, success.) Because the Orient Express would fly so high and so fast, its sonic booms would be muffled to the point where they would become mere sonic peeps. It ) would soar above the ozone layer; since it would burn a mix of hydrogen and atmospheric oxygen as fuel, with water vapor as the end product, it would not damage the atmosphere. The aerospace plane was resurrected in its present form by DARPA's Bob Williams. In 1982 he was investigating the use of hypersonic propulsion for missiles and became curious about how high an airplane could fly using an air- breathing engine. Since no one knew the answer, Williams recruited an expert in propulsion and a specialist in materials. He then had a computer wizard run simulations for him. A little drama ensued once Williams began egging on the computer expert to fly faster and faster. ''I'm up to Mach 12, but it's getting awfully hot -- this thing looks like it's going to melt,'' he warned Williams at one point. Williams told him to cool things off by flying higher, where the air is thinner and creates less friction. The computer model started getting too hot even at a higher altitude, but Williams reassured the man that he could go still faster since DARPA was developing advanced materials to cope with that kind of heat. WHEN THE MAN reported that he had pushed even the new materials to their limit, Williams told him to try active cooling. Williams foresaw a double benefit: The hydrogen fuel, the most efficient available, would be pumped around parts of the aerospace plane to cool it -- and the fuel would burn still more efficiently when heated. ''There was a long silence for about two weeks,'' Williams recalls. ''Finally about 12:30 or 1 o'clock one night I get this phone call: 'All right, damn it, Williams, I've been up for a whole 24 hours running this thing. I'm at Mach 25 and 200,000 feet. What do you want now?' I said, 'Nothing more -- we're there. We're at orbital speed.' '' In 1984 Williams got a go-ahead for the program along with funds for some critical experiments, mainly in propulsion and materials. He assembled a small team of specialists from the Air Force, NASA, and the Navy. (The Navy, responsible for keeping track of what goes on in the oceans, is interested in the aerospace plane's surveillance capabilities.) The team worked secretly under the code name Copper Canyon. Reviewing the work last year, DARPA decided that the program merited a big expansion. It presented the project to top officials of the agencies involved, including the Star Wars program. ''It met with incredible support in all quarters,'' says Williams. ''It was as if this had been a dream of a lot of people. Each agency was willing to offer up funds from its own budget to apply toward this program. Shortly after that, the President spoke about the program and it took off like a shooting star.'' He adds: ''Now I have to make good on all those claims.'' Last April the National Aerospace Plane Program awarded about $450 million in initial contracts. For airframe design, contracts went to Boeing, General Dynamics, Lockheed, McDonnell Douglas, and Rockwell. General Electric and Pratt & Whitney got contracts to develop the propulsion system. Fifty other companies already participate in the program, and their number is growing rapidly. For example, Alcoa and Sikorsky Aircraft are both investigating new materials; Garrett and Gould are working on tiny electrical motors that will replace hydraulic controls in the aerospace plane to help save weight. United Technologies is developing advanced fuel cells, or high-tech batteries. After about three years, the Pentagon and NASA will decide whether progress justifies building the X-30. To make sure it does, Williams zooms around the country with evangelical zeal. Says an executive at one contractor company: ''I think of Bob Williams as a male Joan of Arc. You know, the Lord came down and touched this guy on the top of the head and said to him, 'Baby, go and make hypersonics real.' And he's doing it.'' TO DO IT will require what Williams describes as ''bringing the technological might of the U.S. to bear on one of the most engrossing technological challenges this country has ever faced.'' He'll need every ounce of that might, because much of what the aerospace plane will have to do is unusual or even unique. For one thing, while the fastest aircraft today merely push air molecules out of the way, the aerospace plane will go so fast that it will literally tear the molecules apart. The molecular fragments will heat the plane's skin to the point where it will act as a catalyst, producing new molecular combinations that could damage the skin. The aerospace plane builders' biggest challenge, the propulsion system, must operate at a stunning variety of speeds under varying flight conditions. It will probably consist of a number of different engines, each switched on as needed. To allow conventional takeoff, the aerospace plane must be equipped with an air-breathing engine, most likely a turbojet similar to those on passenger airliners. To push the plane beyond Mach 2 (1,520 mph), a simple ramjet engine will take over. A ramjet contains no whirling turbines, only a cone-shaped structure facing the onrushing air, which it compresses, or ''rams,'' and slows down for burning. But the ramjet is limited at both ends of the speed scale: It cannot gather enough air to work efficiently at subsonic speeds, and it becomes inefficient again at Mach 5 (3,500 mph). At that point a supersonic combustion ramjet -- ''scramjet,'' for short -- must take over. (''Supersonic'' refers to the speed of air through the engine.) The scramjet is the most elegantly simple of all air-breathing engines: It's merely an elongated box with some angled struts inside to slow down the incoming air, and a combustion area in the back into which fuel is injected. The trick is to ignite the fuel-air mixture quickly as it rushes through the scramjet. Model scramjets have been tested in NASA wind tunnels and elsewhere up to Mach 20, but never in flight. Computer projections do show, however, that the scramjet will work at the aerospace plane's intended top speed of Mach 25. What gives the aerospace plane designers a lot of confidence right now is their rapidly evolving ability to use supercomputers to simulate the effects of air pressure and heat on a hypothetical airframe (see photograph, last page). Scientists can now ''fly'' the aerospace plane inside a computer -- not quite as good as real-life flight, but nonetheless allowing designers to try out a large number of configurations under varying conditions. For the skin to survive stresses never before encountered in sustained flight, designers are banking on man's increasing ability to fashion specialized materials. Those now under development include new alloys produced by so-called rapid solidifications technology, which uses astounding cooling rates of up to one million degrees Fahrenheit per second to make materials with such desirable properties as light weight, great strength, and heat resistance. The abrupt cooling realigns the atoms in ways that do not occur under ordinary conditions. Another promising technology: composites, which join at least two different materials such as carbon filaments and a metal matrix to yield a unique set of useful characteristics. But even the best of today's materials can withstand temperatures no higher than about 2,800 degrees F. -- not good enough for the aerospace plane. Its needle-sharp nose, along with the leading edges of its wings and tail, will be exposed to the greatest air resistance. It was this problem that led Williams to think of using supercooled hydrogen to soak up the heat. Using hydrogen for fuel introduces new challenges on the ground, although the danger of fire is less than with conventional fuels because its ignition temperature of 1,085 degrees F. is twice that of aviation-grade kerosene. NASA studies show less hazard to the crew, passengers, and the immediate surroundings from crash-generated fire in a hydrogen-fueled aircraft than in one powered by conventional hydrocarbon fuels. NASA has learned how to handle supercold hydrogen in space launches. For civilian flight, proponents of the Orient Express make the surprising claim that a 300- to 500-seat hypersonic airliner could be not only more successful commercially than the Concorde but as profitable as subsonic aircraft like the Boeing 747. The Air Force has studied the economics of a hydrogen-fueled Orient Express that would fly at speeds between 4,500 and 9,000 mph. The study found that direct operating costs per flight could be competitive with current subsonic aircraft. That conclusion assumes a fast turnaround, although the Orient Express could be so hot an hour after landing that it would need a liquid nitrogen bath to cool it off for ground maintenance. IT ALSO RESTS on the much shorter flight times for the Orient Express -- about two hours from New York to Tokyo, vs. 14 hours on a 747 -- as well as the need for only one crew for the run. ''You can really get a day's work out of it,'' says Benjamin Lightfoot, Northwest Airlines' vice president for maintenance and engineering. He has calculated that in less than 24 hours an Orient Express could fly twice across the Atlantic and four times across the Pacific -- a total of 27,600 miles, or the equivalent of more than once around the earth. Obviously the economic viability of the Orient Express will depend on growth in long-distance passenger traffic as well as still uncertain development and production costs. By the end of this century, McDonnell Douglas expects air traffic between the U.S. and the Pacific rim countries -- Japan, China, South Korea, Singapore, among others -- to soar from the present six million passengers a year to more than 30 million, making the Pacific the world's busiest air travel corridor. No one knows yet how much an Orient Express will cost the airlines, although some authorities have speculated that the price would be $200 million to $300 million per plane (vs. about $100 million for a 747). Lightfoot says an airline probably couldn't get away with charging more than 10% to 15% more than present-day fares for hypersonic flight. The probable development cost of the first two X-30s, plus an earthbound test model, is known, however: about $3 billion. This is not a high price for entry into a new arena of flight. The Concorde precedent suggests that if the U.S. doesn't build the aerospace plane, others will. Research is already under way in Britain, West Germany, Japan, and most likely the Soviet Union, which has always had a strong tradition in aviation. The British want to build a craft that will go directly into orbit, like the U.S. version. The West Germans are pushing a two-stage vehicle that would piggyback a small space shuttle high into the atmosphere and launch it into orbit from there; the first stage could also serve as a basis for developing a hypersonic transport. Lightfoot fears that the Japanese may try to beat the U.S. into the potentially lucrative market for an Orient Express airliner. Bob Williams and General Staten claim that Americans could do the job best because they are the world's best engineers. That is doubtless a chauvinistic exaggeration, but Americans have shown themselves to be the world's best aeronautical engineers. Says General Staten: ''The aerospace plane is very much in the American personality. It's the kind of thing we've done before. It stimulates the pioneer in all of us.''