The Columbia accident and growing doubts about the safety of the space shuttle are forcing NASA to accelerate efforts to build a new space vehicle -- one that can begin operating in less than a decade.
The space agency is awarding $135 million to three major aerospace companies to begin designing what could become a multibillion-dollar fleet of orbital space planes just big enough to ferry crews of about four astronauts back and forth to the international space station.
The plan, with little fanfare, represents a potential watershed in the U.S. space program.
In a departure from the ambitious goals it has set since the dawn of the Space Age, NASA wants a modest system that will break no new technological barriers but instead reduce costs and improve safety -- perhaps by adding a crew escape system, for example.
The space plane would not have its own main engines, but rather ride atop an expendable rocket, such as a Delta 4 or an Atlas 5. Pilots would be a thing of the past, and maneuvering the craft in space would be small, automated thrusters. The plane would carry only tiny payloads -- making room for them would require reducing the size of the crew and removing seats, NASA officials say.
The plane may even lack wings and take the form of a capsule, like the 1960s-era Mercury, Gemini and Apollo ships, splashing down in the ocean or parachuting onto land.
At least in popular perception, it could amount to an uninspiring step backward.
"On some level, it may appear it is just some lower-technology way to get people to and from space," said Dennis Smith, NASA's program manager. "But the key thing is we need them there to perform science, and we need to improve safety."
Some critics say the new program lacks vision and fails to make clear why the United States even has a space program. The infrastructure planned by the Bush administration, they say, will preclude any human exploration of space for decades and limit all human activity in space to low Earth orbit at the space station.
But others say NASA's new goals are long overdue for an agency that tried too hard to be the technological vanguard of America.
The change is one measure of the tremendous effect of the Columbia loss, which appears to be surpassing the Challenger explosion 17 years ago in terms of realigning the space program and forcing a confrontation with limits. When Challenger was lost, the space shuttle fleet was relatively young, but today NASA recognizes it can no longer put off a replacement.
The space plane, however, will not fully replace the shuttle or its remarkable ability to lift heavy loads in its 60-foot-long payload bay. John Rogacki, NASA's senior official overseeing spacecraft development, says the agency cannot operate the space station with only the space plane, meaning the shuttle fleet could be around an additional 20 years.
NASA has repeatedly attempted to replace the shuttle since the late 1980s with an advanced launch system capable of reaching orbit on a single stage and cutting costs by tenfold. The agency spent billions on such programs as the National Aerospace Plane, the X-33 and the Delta Clipper, among others. It designed exotic engines like the aerospike and supersonic ramjet. One by one, the replacement efforts collapsed, leaving the agency dependent on the shuttle for far longer than it ever envisioned.
Thus, the space plane is only a partial solution to NASA's predicament. The agency also is studying a new reusable launch vehicle, though that effort is lagging well behind the space plane. If it gets built, it could carry the space plane, but for the foreseeable future the space plane will ride on expendable rockets.
Dave Urie, creator of the X-33 and now an aerospace consultant, said NASA and Congress were too ready to give up in earlier programs any time a technical problem came up. It has created a wasteful cycle in which billions of dollars are spent on projects abandoned prematurely, and now the agency has embarked on a program that seems to lack ambition, he said.
"Where's the progress?" Urie asked. "NASA should be sticking its neck out, doing things that nobody else has the guts to do."
The space plane program originated in the fall, when the Bush administration quietly outlined its intentions in a budget document submitted to Congress. But the Columbia accident gave the project urgency, and NASA is forming a plan to sharply accelerate the development schedule, which originally called for the plane to be operational in 2012.
"With 113 flights and two accidents, the shuttle is not as safe a system as we thought it was," said Mike Coats, Lockheed Martin Corp.'s program manager for the space plane. "I want to give the crew a fighting chance."