Can Hard Science Save The Aerospace Plane?

After years of hype, the national aerospace plane may finally be lumbering off the ground. Gone are the visionaries who spent years promoting proposals that have turned out to be little more than pipe dreams. Replacing them is a group of practical scientists and engineers. They admit that they are working on an experimental prototype that may never fly, much less carry passengers. Ironically, though, it’s just this kind of pragmatic talk that could bring the project the credibility it will need if it is ever to launch its exotic bird. The most obvious change is at the top. Last April, the Air Force took command of the project from the Defense Advanced Research Projects Agency. The move was scheduled to occur in 1990, but the date was moved up after the previous director was replaced for overstepping his authority by seeking direct presidential support for the program. As it is, the government will spend more than $300 million on the plane this year—two-thirds of it by the Air Force and one-third by NASA—and Air Force officials have decided to assert greater control over the disposition of their funds. But the changes aren’t just organizational. The project’s new director, Air Force engineer Robert Barthelemy, hopes to double spending for fundamental research into the kind of advanced materials needed for hypersonic travel. The increased emphasis on building up a database on the challenges posed by flying an aircraft at speeds upto orbital velocity has invigorated the field, with the technical community of experts growing from only 300 people three years ago to more than 5,000 today. These experts are, in turn, feeding the newly pragmatic project management with hard numbers. Recalling the old days, Princeton’s Seymour Bogdonoff, an experimental physicist who has been wrestling for decades with such issues, says, “There was no database. One person’s views had been as good as the next.” With the possible exception of President Reagan. Heavy Rhetoric Probably no one had a rosier view of the plane than the president. Most people first heard about it when Reagan declared, in his 1986 State of the Union message, that “we are going forward with research on a new Orient Express that could, by the end of the next decade, take off from Dulles Airport [outside Washington, D.C.] and accelerate up to 25 times the speed of sound, attaining low-earth orbit or flying to Tokyo within two hours.” But that rhetoric proved to be an impossibly heavy load for such a revolutionary plane. Even its name was more than scientists could handle. Barthelemy, who took over last April, uses only its proper research designation, X-30. And he admits that the X-30 is “a risky vehicle. There won’t be any zero-risk technology,” he adds. Even the trappings of the “hype dream”—the fancy renderings and viewgraphs developed over a decade that symbolized the hopes of its most fervent supporters—have disappeared. They are conspicuously absent from Barthelemy’s office walls; instead, there is a framed painting of a New England lighthouse with seagulls. “I look at it about 10 times a day,” he says. “It helps soothe me.” He needs all the peace of mind he can get, since the technical challenges, as he freely concedes, are enormous. Barthelemy’s team is preparing to build an experimental aircraft that is meant to fly eight times faster and five times higher than any plane has yet flown. The X-30 would be the first aircraft to fly into orbit from a normal start down a runway. Barthelemy estimates that building and testing the X-30 will cost “at least $3 to $4 billion, maybe more.” As for justifying this expense, Barthelemy admits it won’t be easy. “We are going to have to justify much more strongly [than we have] what we can do with hypersonics.” His hopes are built around the scramjet. A novel engine, the scramjet is designed to handle air flowing into the engine at hypersonic speeds and avoid the crippling shock waves that form in front of the engine. Turbojets offer good fuel economy but are limited in speed; they overheat if flown much beyond 2,000 miles per hour. Rockets, by contrast, readily reach an orbital velocity of 17,000 miles per hour. But their speed comes at a price: the added weight of carrying their oxygen with them rather than drawing in air from the atmosphere. Barthelemy hopes that scramjets can avoid the speed and temperature limits of turbojets while preserving the weight advantages of using air to burn the fuel. But the challenge of using air that flows at such high speeds is daunting. So far, scientists are stymied at speeds that approach 5,000 miles per hour as fast as that is, it’s still less than one-third of orbital velocity. Barthelemy is confident that his emphasis on exploring the fundamentals of hypersonic, flight will ultimately serve the project better than a campaign to sell the idea of an Orient Express. But he also knows that the project owes a great debt to the dreams of four men: Tony duPont, an independent inventor and entrepreneur Robert Williams, an aeronautical engineer and project manager at DARPA; Robert Cooper, director of DARPA; and Lawrence Skantze, a four-star Air Force general. Of these, only duPont had a professional background in hypersonics. An aeronautical engineer from Caltech, duPont had invented a variant of the scramjet that he believed would deliver particularly high performance. In 1970 he launched an aggressive campaign to sell his ideas to NASA, the Pentagon, Congress, and the White House. He didn’t get very far by the end of the decade he was reduced to testing a wood-and-Plexiglas model in a friend’s backyard, using an air compressor from Sears. However, in 1983 the picture improved considerably, thanks to DARPA. Cooper, an electrical engineer and former director of NASA’s Goddard Research Center, wanted to build new experimental aircraft. Cooper listened to duPont’s sales pitch, then turned him over to one of his best aerodynamicists, Robert Williams. Williams was an expert on helicopters, not hypersonics. But he became a convert, seeing duPont as “a maverick with an absolutely brilliant grasp of propulsion.” Armed with this endorsement, Cooper launched a $6 million study of the prospects for hypersonics. This 1984 study, called Copper Canyon, was part of the agency’s long line of speculative projects that had included such technologies as stealth aircraft and beamed-energy weapons for the Strategic Defense Initiative. “I couldn’t pick any obvious holes,” Cooper stated after a comprehensive review of the study in 1985. Cooper put Williams in touch with other key government officials, including Skantze, who was then head of the Air Force Systems Command. For several years Skantze had been promoting a trans-atmospheric vehicle that could eventually replace the shuttle as a means to carry cargo to orbit. But he needed someone to tell him how to build it. In mid-1985 Skantze heard about duPont’s engine from Williams. After watching a test of a duPont engine, Skantze rallied the Pentagon and NASA behind a drive to develop the national aerospace plane. Williams was picked as its manager. The professional hypersonics community might have been excused for believing the hype; after all, it foresaw a multibillion-dollar bonanza after years of struggling along on a few million dollars annually. But its analyses were becoming increasingly sophisticated; where duPont had relied on a hand-held calculator, its members now had the latest supercomputers. And they discovered that the numbers didn’t add up. “Vehicle weights are much larger than duPont’s estimates,” wrote Robert Jones, a NASA-Langley aerodynamicist who had been managing NASA’s experimental studies of scramjets, in one critique. “Engine performance is less than duPont estimates; drag is higher. The baseline vehicle cannot reach orbit [his emphasis].” Jones urged Williams to put more funds into areas such as advanced lightweight materials rather than assuming that duPont was right. Williams replied that Jones should question his own analyses. As Princeton’s Bogdonoff recalls, “People had been telling Williams for years that duPont was wrong. He wouldn’t listen. He would say that, if you try hard enough, you can get it to work.” By 1987 Williams was finding himself increasingly estranged from the growing hypersonics community. He reacted by viewing them as adversaries. A briefing before the Defense Science Board, the Pentagon’s principal scientific advisory group, demonstrated how wide the gap had grown. Williams had helped pick the panel’s members and had chosen the people who would conduct the briefings. Nevertheless, the die was cast. “The first time I walked into the DSB, I ran into an absolutely hostile environment,” he recalls. “They had already made up their minds about the baseline.” Confronted with such opposition and facing a cut in Air Force support, Williams cast about for a senior administration official who could salvage his budget. That search led him straight to the top. In December, Williams wrote a letter to Howard Baker, White House chief of staff, urging him to seek President Reagan’s renewed support for the aerospace plane. Baker did no such thing. Instead, he forwarded the letter to Defense Secretary Frank Carlucci, who decided that Williams’ breach of protocol was sufficient cause for his removal from the program. Williams’ replacement, Barthelemy, is a member of the Senior Executive Service who has held such posts as technical director of the Air Force Wright Aeronautical Laboratories. His view of hypersonics is much more low-keyed than Williams’, and he’s quick to dismiss duPont’s design. “It’s probably a vehicle that we’ll never build and that will never fly,” he says. “But it’s the configuration that started off the program, and it’s unclassified.” The outspoken Bogdonoff gives him high marks: “There aren’t many people at his level of management who have Raft’s level of technical exise” A Fresh Look However, the program needs more than a competent manager to be a success. A recent paper by Jack Kerrebrock, associate dean of engineering at MIT and member of the Defense Science Board, asserted that the X-30’s performance will be even worse than many of his colleagues anticipate. Kerrebrock also chairs a National Academy of Sciences panel that, at the request of the Air Force, is taking a fresh look at problems of hypersonics. In the meantime, the project is moving ahead on several scientific fronts. “You could say that Williams and duPont were optimistic on engine performance but pessimistic on structural weights,” says physicist Fred Bug of Johns Hopkins University’s Applied Physics Lab. “We’re finding that we can do more with materials and get lower weights.” In addition, Barthelemy is funding the development of a new fuel, called slush hydrogen. A mixture of solid and liquid hydrogen, it offers more energy and greater cooling ability. Industry is also beginning to play a major role. Pratt & Whitney and Rocketdyne are designing engines for the X-30, while Rockwell International, General Dynamics, and McDonnell Douglas are working on the airframes. In September 1990, one engine builder and one airframe contractor will be picked to move ahead with development. That schedule, of course, depends on continued support from the next administration. The Republican Party platform calls for further development of the aerospace plane as part of a long list of space-related research initiatives, and Vice President George Bush has used his support for the plane to appeal to voters in several space-minded states. Democratic nominee Michael Dukakis hasn’t commented on the X-30 specifically, according to campaign aides, although he has sharply criticized the Orient Express for serving only narrow interests. Harvard’s Lewis Branscomb, the former IBM chief scientist who has been widely rumored as a possible science adviser in a Dukakis ad- ministration, says he believes that a Dukakis administration might look more favorably on a research program to develop hypersonic flight. “There’s no demand within industry for an Orient Express,” he says, “but there’s a difference between a search for broadly applicable technology and a prototype for which there is no demand.” Clearly, supporters of the X-30 hope that the dream of hypersonic flight will propel the project beyond whatever political and budgetary obstacles lie in its path. And they believe that the right team is now in place to deliver on the project’s scientific promise. T.A. Heppenheimer is a Southern Cal ifornia-based freelance writer with a Ph.D. in aeronautical engineering.

Can Hard Science Save The Aerospace Plane?

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Ta Heppenheimer

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October 1988

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