NASA’s bid to accelerate the schedule for fielding a crew rescue vehicle for the international space station has intensified the debate over how ambitious an approach the agency ought to take on its Orbital Space Plane program.

One side is urging NASA to keep it simple in light of the Space Shuttle Columbia disaster and concentrate on updating tried-and-true designs from the past. The other side is urging NASA to push the envelope and develop an Orbital Space Plane that not only meets the needs of the space station program but also puts the agency in position to move out beyond low Earth orbit.

"We wanted a third-party perspective on [the Orbital Space Plane] and figured we wouldn’t have been able to get that kind of participation because of ongoing contract discussions," said Brian Chase, executive director of the National Space Society and the panel moderator.

Urging NASA to take an aggressive approach to the Orbital Space Plane program was former House Science Committee chairman Robert Walker, an aerospace lobbyist here who last year served as head of the Commission on the Future of the U.S. Aerospace Industry.

NASA officials said in mid-July that they are taking a close look at having industry produce an Orbital Space Plane to serve as an emergency crew lifeboat at the international space station by 2008, two years ahead of the previous schedule. By 2012, NASA wants to field a vehicle to replace the space shuttle for routinely transporting crews to and from the space station. Both the crew rescue and crew transfer vehicle would be based on the same basic design and would launch on an expendable rocket, probably either Lockheed Martin’s Atlas 5 or Boeing’s Delta 4.

Walker said NASA should resist the temptation to build a vehicle that satisfies the pressing crew rescue and transfer needs of the international space station but has little or no potential to evolve into something capable of performing future missions for NASA or other federal agencies.

"We shouldn’t kid ourselves, folks," Walker said. "Whatever we design and spend money on is going to be the vehicle for the next 20 years."

For that reason, Walker said he favors an aerodynamic lifting-body design that could become the second stage for the type of fully reusable booster envisioned by NASA, the Pentagon and industry. Walker said the vehicle should be capable of runway landings and scalable to a variety of potential NASA or Pentagon missions.

Walker said NASA should not be shy about asking Congress for the money to build the Orbital Space Plane and should move out aggressively while the Columbia disaster is still fresh on the minds of lawmakers.

NASA has made no public statements to date about what the Orbital Space Plane will cost. According to sources, recent internal estimates peg the project as a $17 billion to $18 billion undertaking over the next five to eight years.

"Clearly we are at a moment where Congress has a recognition of the need to move forward," Walker said. "This is the right political time to do this."

Walker worries that a more conservative approach to the Orbital Space Plane, such as building a ballistic capsule that meets the space station’s crew transportation needs but has limited potential to serve as an upper stage for a fully reusable launcher, could get a rough reception in Congress.

"You’ve got to give them a view of the future," Walker said. "Not just a view of the present."

Former NASA official Lori Garver, a vice president at the consulting firm DFI International here, did not disagree with Walker’s assessment of the mood of Congress but said it is becoming increasingly clear to her that what NASA wants is the quickest solution to its crew transfer conundrum. "I think they want it soon and simple," Garver said.

For its part, NASA says it is open to a capsule design and that contractors should not read too much into the term Orbital Space Plane. Frederick Gregory, NASA’s deputy administrator, said July 17 at an aerospace conference in Dayton, Ohio, that even if the agency ultimately fields a capsule design it would incorporate the latest technologies.

Samuel Durrance, a panelist and former astronaut, said NASA could best meet its criteria for the Orbital Space Plane with a capsule that borrows "wherever possible" from the command module used in the Apollo moon missions in the late 1960s and early 1970s. Whether the Orbital Space Plane is reusable or not should be based on cost considerations, he said.

Durrance, who now heads the Florida Space Research Institute in Cape Canaveral, agreed with Walker that whatever NASA builds, the vehicle should be able to evolve into something that can perform missions other than space station support, such as expeditions beyond low Earth orbit. But expediency is the key if the space station is to live up to its potential as a research platform, Durrance said.

NASA ought to push to field the crew rescue version or the Orbital Space Plane by 2007 instead of 2008, he said.