Discovery expected to return safely

Initial inspections show that the space shuttle Discovery can safely fly home Aug. 7, mission managers said yesterday, but they remained deeply concerned about the risk of serious damage from chunks of insulating foam falling from the external tank during future launches.

So far, engineers have counted about 10 instances of dings, scuffs, and damage to coating and tile, although it appears there is only one possible instance of a minor debris hit. They estimated Discovery has sustained far fewer impacts from foam and ice debris than in past missions, which NASA officials attribute to design changes made after the Columbia disaster in February 2003.

''The initial report was that it looks extremely good and we don't have anything to worry about on Discovery," John Shannon, flight operations manager, said yesterday after the shuttle docked flawlessly at the International Space Station. However, a full inspection would not be completed for about three days, he said.

On Wednesday, NASA officials declared the shuttle fleet grounded until the problem with falling debris could be solved. But there were concerns that a solution to protect the three shuttles in the fleet may take too long and too much money. Since the Columbia disaster, NASA has spent hundreds of millions of dollars making changes that engineers thought would prevent exactly what happened two minutes after Discovery blasted into space Tuesday.

A more than 2-foot-long and 1-foot-wide piece of foam tore off the external fuel tank. A slightly larger piece fell off the same tank during Columbia's liftoff in January 2003, damaging that shuttle and dooming all seven astronauts on board. A piece of foam fell from a different part of the tank on Discovery, which was spared a strike because the foam detached at a higher altitude where the air is thinner. That allowed it to drift away, rather than be struck by Discovery. Officials had considered redesigning that area of the fuel tank after the Columbia disaster, but decided it was not necessary.

Unless engineers can find a comprehensive solution to the debris problem, the fleet may be permanently grounded, the International Space Station may be abandoned, and the agency's credibility may be eroded as it attempts to win public confidence for a more daring era of space travel, observers said yesterday.

''What I keep thinking about is the Concorde. . . . They are all sitting in museums," said Howard McCurdy, professor of public affairs at American University, who has written extensively on the space program. ''We've spent a lot of time trying to fix this already."

Discovery's 7:18 a.m. EDT space station rendezvous included the shuttle performing a back flip prior to docking so that the station crew could photograph its underbelly heat shield to look for damage. Discovery's crew will test new safety shuttle mechanisms and deliver 15 tons of supplies to the space station. Yesterday, more than 200 NASA engineers continued to painstakingly analyze photos and video footage, frame by frame, to determine what damage the shuttle sustained during its ground-shaking blast into orbit. Scientists will finish inspections by the end of the weekend and say they then hope to issue a clean bill of health for the shuttle.

The harvesting of images of virtually every inch of the shuttle's body is part of a new screening system to identify problems like those that brought down Columbia. During Columbia's liftoff, foam fell off the external tank and punched a hole in the orbiter's thermal layer, which led to the craft disintegrating during reentry into the Earth's atmosphere.

NASA officials indicated they were stunned by the size of the piece that fell from the section of the external fuel tank that protects wires and cables running along its side. The piece of foam that detached Tuesday weighed about half as much as what hit Columbia, and it ranged in thickness from 2 1/2 to 8 inches.

''This is a test flight," NASA administrator Michael Griffin said in a statement posted on the agency's website yesterday. ''Among the things we are testing are the integrity of the foam insulation and the performance of new camera equipment installed to detect problems. The cameras worked well. The foam did not."

Mission managers in Houston said three other tiny foam pieces apparently fell off Discovery's fuel tank near where the larger piece was shed. Exhibiting pictures of stunning clarity, NASA managers illustrated how one small piece may have hit a wing, but noted that a careful examination of the area showed no sign of impact. Still, NASA officials say they are taking all potential damage seriously and are most concerned about a small piece of tile or its covering that appears to be missing from the edge of the door covering the nose's landing gear. In a way, NASA is overloaded with information. In the past, so few cameras were trained on shuttles during liftoff that agency officials had no idea how much debris fell, unlike with the Discovery launch, when more than 100 cameras were trained on the shuttle and its external tank.

If the shuttle is damaged, NASA's options for a rescue are limited because the shuttle Atlantis that was to rescue the Discovery crew is grounded. Astronauts have experimental repair kits designed to test fixing gouges in the shuttle's skin, but NASA officials and astronauts have indicated they are reluctant to use them because they are only designed for early testing.

Discovery's launch was supposed to set off an ambitious 15-year timeline for NASA. The aging shuttle fleet is supposed to fly to the International Space Station more than 20 times to help finish it before the shuttles are retired in 2010. Then, NASA had planned to turn its full attention to developing a new crew exploration vehicle to fulfill a presidential mandate to send an astronaut back to the moon by 2020, and then on to Mars. NASA officials have also indicated that they may send a shuttle to repair the Hubble Space Telescope if test shuttle flights go well.

But space policy specialists expressed concerns yesterday that NASA, with a limited budget, may not have enough funds to conduct a major redesign of the shuttle if it is needed to solve the debris problem, as well as to create the next-generation vehicle to get back to the moon and on to Mars. Some scientists wondered whether the shuttle fleet should be retired now to focus NASA's attention on the future.

''A serious possibility is the most prudent action [might be] to cancel the space shuttle," said Louis Friedman, executive director of the Planetary Society, a space advocacy group based in California.

But others said NASA needs to see if the problem can be solved quickly before making that determination. Only one other test flight is scheduled for this year -- in September -- so a short delay would not affect the program's overall schedule.

''It's premature to say the program should shut down," said John Logsdon, executive director of the Space Policy Institute at George Washington University. ''[The debris issue] may be a body blow, but not a knockout."

Material from the Associated Press was used in this report.