In 1990, the Pentagon's Star Wars program called for a radically new rocket that would do what no other spacecraft had done: climb into orbit in one piece, without dropping off booster rockets on the way up--and without a human pilot on board. It would be the space equivalent of an airliner--reusable and therefore cheaper to operate.
Skeptics at NASA insisted that any rocket big enough to hold all the fuel required would be too heavy to reach orbit. But aerospace companies crunched the numbers and decided a so-called single-stage-to-orbit (SSTO) rocket had become technically feasible. McDonnell Douglas Corp. won the contest to build a suborbital vehicle to test the concept. Today, its rocket--the Delta Clipper Experimental, or DC-X--is one of three contenders being evaluated by NASA as a potential successor to the space shuttle. A decision should come on July 1.
Despite the skeptics, NASA has embraced the one-piece approach since inheriting the DC-X program from the Pentagon last year. On June 7, after watching the 10th test flight since 1993, NASA Chief Daniel S. Goldin left no doubt that the fate of NASA's longtime pet, the space shuttle, was sealed. "This is how we will change space flight," he told the crowd gathered at White Sands Missile Range in New Mexico.
NEW FRONTIERS. The main goal is to chop the tab for lifting payloads into space to only 10% of current costs, which run about $10,000 per pound. The U.S. space-launch industry would then have by far the lowest-cost launcher and might be able to recapture some of the 70% market share it has lost to rivals in France, Russia, and China. Cheap access to space could also usher in a new economic frontier, just as "railroads opened up the West," says Paul L. Klevatt, who directed the McDonnell Douglas DC-X team.
Goldin's determination to replace the shuttle doesn't necessarily mean its successor will resemble the pyramid-shaped DC-X. The McDonnell Douglas design could get whipped by sleek rivals with winglets. Both Lockheed Martin Corp. and Rockwell International Corp. have offered less risky SSTO designs that would take off vertically but land horizontally, like the shuttle (table).
For the winner, there's a prize of $900 million, over three years, to build a half-size experimental model. This experimental vehicle, to be called the X-33, will be used to test the technologies needed for a full-fledged reusable launch vehicle--RLV, for short.
There are two crucial steps in the development of an RLV, says Gary E. Payton, manager of NASA's reusable launch vehicle program. One is to slash operating costs by eliminating the small army that NASA needs to service the shuttle and strap on its external main engine and booster rockets. That's the reason for packaging everything into one single-stage rocket that can be serviced as easily as an airliner, Payton notes. In June, a 24-person ground crew was able to relaunch the 42-foot-tall DC-X 26 hours after it landed.
The next step is to prove that an SSTO rocket can actually be light enough and powerful enough to reach orbit. That requires a host of new technologies, says Payton. Some progress has already been made with the DC-X, earning it a new moniker: DC-X Advanced, or DC-XA. For example, the fuel tank that holds liquid hydrogen is now made from graphite-epoxy composite. It tips the scale at 2,146 pounds, or 66% less than its aluminum predecessor.
Still, there's no way the DC-XA could fly fast enough to leave the earth's gravity, says Klevatt, who now runs the X-33 program at McDonnell Douglas. Bigger engines and a lighter, all-composites structure are needed to attain the "escape velocity" of 17,500 miles per hour. These improvements will be tested in a DC-XA spinoff, if McDonnell Douglas wins the X-33 job.
NASA funding will stop in 1999, however. The agency wants the winner to pick up the multibillion-dollar cost of building the full-size RLV.
TOURISM. All three contenders are cautiously optimistic that they can raise the money. But a successful X-33 is a crucial first step, says Thomas K. "T.K." Mattingly, Lockheed Martin's vice-president of reusable launch vehicles. Without solid proof from the X-33 that the single-stage-to-orbit idea is feasible, "we think it would be impossible to attract the necessary capital," Mattingly says.
If there are no major hitches, improved second-generation RLVs might trim launch costs to $300 per pound or less. Even space tourism could then be affordable. But Klevatt figures you'll probably have to wait until 2012 to dash off for a weekend in orbit.