A shuttle rolled out to the Kennedy Space Center launch pad this week, astronauts climbed in, and NASA counted down to launch for the first time since the Challenger accident last January. The rollout and countdown were rehearsals for a liftoff scheduled 15 months from now - an event that will mark resumption of a more modest program than the one that led to the Challenger disaster.
The revised program should be safer, too. The National Aeronautics and Space Administration has settled on a new design for the flawed booster joints, reproduced in tests the scorching leak that destroyed the Challenger, and is beginning to test the new design.
Management shifts have swept over the upper levels of the program.
Most important, the shuttle is now relieved of the contradiction that many observers have viewed as the key strain on the pre-Challenger shuttle: the pressure to run a still-developing spacecraft as a routinely operational one.
``That error has now been corrected,'' says Jack Kerrebrock, a Massachusetts Institute of Technology professor and former associate administrator at NASA. ``That doesn't mean that the shuttle is suddenly safer to fly. But it's a change in attitude. That makes a big difference.''
Skepticism remains, however. Doubts about NASA's judgment leading into the Challenger accident continue to surface. Debate over the new design for joints in the shuttle booster engines is still strong. John Logsdon, a space policy expert at George Washington University, notes that NASA is still about 25 percent more optimistic about shuttle flight frequency than others, such as the National Research Council (NRC) commission that recently studied shuttle flight rates.
``There is still a disjoint between what NASA is projecting internally and what well-informed outsiders are saying,'' Dr. Logsdon says.
Whether NASA can meet its planned launch target of some time in the first quarter of 1988 depends largely on how well the new booster joint designs test out.
The space agency is scheduling only five launches for 1988. When it is once again running a four-orbiter fleet, in 1991 or '92, the agency is planning 16 launches a year. The NRC told Congress in October, however, that 11 to 13 flights a year are the most NASA can expect.
Before the Challenger accident, NASA had planned 15 shuttle launches in 1986 and 24 in 1990. But the shuttle's role in space is ebbing. NASA has given up launching commercial satellites, except for a few that require a manned launch vehicle, and is turning that task over to private launch companies. The military, a heavy shuttle user, is fast developing its own launch capacity. And NASA is deciding now whether to design the projected space station so that it can be supplied by unmanned rockets, taking even more demand off the shuttle.
Shuttle management has been thoroughly revamped. There are new directors at NASA itself and all three major space centers - Johnson in Houston, Kennedy at Cape Canaveral, and Marshall in Huntsville, Ala.
The head of the shuttle program, Arnold Aldrich, who was largely absolved of blame for the Challenger disaster, is moving from Houston to headquarters in Washington, D.C. There he will report directly to Rear Adm. Richard Truly, the associate administrator for space flight. The move is meant to clarify and simplify authority in a program where communication has been stymied by regional space center parochialism.
Management shifts also include a stronger role for astronauts. Admiral Truly, who returned to NASA last spring, is himself a former astronaut. Robert Crippen, a current astronaut, will be Mr. Aldrich's deputy in charge of flight readiness and the final launch decision.
The hardware changes NASA makes must pass muster not only with the agency's own review panels but with NRC committees of outside experts.
The key new design is of the joints between segments of the solid fuel booster rockets. NASA engineers have settled on a prime design concept featuring a new lip around the inside of the joint that keeps it from twisting slightly open as the rockets bulge under pressure.