"I think weve done a lot of that already," Lockheed Vice President Jerry Rising said. The metallic skin designed to protect the X-33 during re-entry is very sturdy and easy to maintain, "so this is a very robust thermal protection system, more than anything thats out there." He said the system could be retro-fitted to the shuttle, which has an older and more fragile shield of tiles.

The X-33 is scheduled for six months of test flights starting in summer of 2000. If it completes its flights successfully, Lockheed will go ahead and build the VentureStar, a fully reusable, single-stage-to-orbit vehicle.

Only after the vehicle has flown 17 or 18 trips, Payton said, would NASA consider purchasing flights on the Venture Star to send crew members up to the International Space Station. That could be as early as 2008 or as late as 2012 under current estimates, Payton said, and there would be additional years needed for the transition of vehicles.

Subcommittee Chairman Dana Rohrabacher (R-California) expressed support for the program at the start and close of the meeting, and said afterwards that "certainly all the questions are answered, not certainly all the concerns are answered." Rohrabacher has opposed what he thinks is NASA putting "all its technological eggs in one basket" by concentrating too much on the X-33.

"I havent seen anything that would suggest this program is in disarray," he said in his closing statement. "Im grateful for that. Usually, we dont have these proceedings unless theres something very, very wrong."