NASA looks at ways for astronauts to fix shuttle tiles in orbit


HOUSTON - NASA will study whether it can give astronauts the ability to inspect and repair heat-resistant tiles on the space shuttle while in orbit, officials said yesterday, one of the first moves the agency has made to address safety since the Columbia disintegrated while re-entering Earth's atmosphere.

Officials at the National Aeronautics and Space Administration insist they intend to fly the shuttles again, though the space agency will have to assure the public that a replay of the Columbia tragedy Feb. 1 could not occur. If investigators determine that damaged tiles were at fault, the study could provide NASA with a way to protect the craft in the future.

Even if another cause is identified in the Columbia accident, the investigation has already revealed so many weaknesses in the heat protection system that changes are likely. Though the study is just under way, it marks a significant shift in policy.

NASA was unable to inspect Columbia for damage while it was in orbit - and the astronauts could not have repaired the craft anyway. With current technology, the crew and Mission Control officials in Houston merely accept damage to protective tiles as a routine risk of space travel.

In the early days of the shuttle program, NASA rejected the idea of equipping astronauts with the ability to make repairs because officials did not think it was possible and did not want to acknowledge that they had anything less than complete faith in the tiles. But the ceramic tiles - more than 24,000 of which protect the shuttle from the intense heat of re-entry - are a focus of the investigation into the Columbia failure.

"This is the prudent thing to do," said NASA spokesman James Hartsfield. "It's something we should do."

As Columbia was lifting off Jan. 16 from Cape Canaveral, Fla., three pieces of foam insulation fell from an external fuel tank and struck the leading edge or the underside of the left wing. While an independent panel appointed by NASA continues to investigate the cause of the disaster, that liftoff incident is a chief suspect. The foam debris, investigators suspect, may have damaged the tiles or the craft's landing gear door, allowing superheated gas known as plasma to penetrate the shuttle and bring it down.

In addition to the tile-repair study, NASA officials are examining whether the agency can improve the application of foam insulation on the structural connections between the external tank and the orbiter. Chunks of foam have fallen from that part of the tanks in three missions.

The tile study will investigate whether astronauts who dock with the International Space Shuttle can take advantage of the space station's $1 billion robotic arm to assess the integrity of the shuttle. The space station's 58-foot-long, 3,000-pound arm could allow astronauts to inspect the shuttle's belly, then use it as a giant platform to perform repairs while spacewalking, Hartsfield said.

Among the questions the study would attempt to answer is whether material can be developed that would allow astronauts to repair damaged tiles or replace missing tiles. In past missions, NASA has found hundreds of damaged or missing tiles on the orbiter.

Any repairs would have to maintain the shuttle's smooth exterior contours, which are essential to its aerodynamic stability during re-entry at speeds of more than 17,000 mph, said Paul Fischbeck, an engineering professor at Carnegie Melon University who co-authored a study that examined tile damage on space shuttles.

"Giving astronauts the ability to repair tiles makes sense," Fischbeck said.

In all likelihood, the measure would not have saved the seven crew members aboard Columbia. Because it was a rare mission devoted entirely to scientific research, Columbia was not assigned to go to the International Space Station and did not have enough propellant to get there if it needed repairs.

However, nearly every shuttle mission planned for the future, except for an occasional trip to service the Hubble Space Telescope, will include a trip to the space station.

NASA officials also said yesterday that they have deciphered two more seconds of garbled data emitted by the shuttle during its final moments. Those two seconds suggest that the shuttle's cockpit and fuselage may have been intact as the shuttle approached Texas, even though pieces of the shuttle appear to have begun falling off far from the coast of California.

Ralph Vartabedian and Scott Gold write for the Los Angeles Times, a Tribune Publishing newspaper.

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