NASA Aims for In-Orbit Tile Repair

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

NASA officials 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 could not occur.

If investigators determine that damaged tiles were at fault in the Feb. 1 crash, then the study could provide NASA with a way to protect the craft in the future.

Even if another cause is identified as the cause of the Columbia accident, the investigation has already revealed so many weaknesses in the heat-protection system that some changes are likely.

Though the study is just underway, it marks a significant shift in policy.

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

In the early days of the shuttle program, NASA rejected the notion of enabling astronauts to make repairs because administrators did not think it was possible and did not want to acknowledge that they had less than absolute faith in the tiles. But those ceramic tiles -- more than 24,000 of which protect the shuttle from the intense heat of reentry -- are a focus of the investigation into the Columbia tragedy.

“This is the prudent thing to do,” NASA spokesman James Hartsfield said in an interview Monday. “It’s something we should do.”

As the 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 Columbia disaster, that liftoff incident is a chief suspect. The foam debris, investigators suspect, may have damaged either 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 now fallen from that portion of the tanks in three missions.

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

The robotic arm, built by Canadian engineers as part of the country’s role in the development of the space station, works much like a human arm, but with seven joints. It was considered a revolutionary design in part because neither end must remain anchored to the space station. Instead, the arm creeps along the outside of the space station much like an inchworm.

Among the questions the study would attempt to answer is whether material can be developed that would allow astronauts to repair or replace 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 reentry at speeds of more than 17,000 mph, according to Paul Fischbeck, an engineering professor at Carnegie Mellon University who coauthored 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 of the Columbia. Because it was a rare mission devoted entirely to scientific research, the 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. The shuttle is a key provider of supplies and personnel for the $100-billion space station, which remains in permanent orbit. Sixteen nations are participating in the effort to build and operate the station.

Hartsfield said NASA won’t know for months how much it would cost to retrofit the space station’s robotic arm, giving it the capability of assisting shuttle repairs.

“If it can be done,” said John Logsdon, head of the Space Policy Institute at George Washington University, “it should be done.”

Even before the space shuttle’s first flight in 1981, NASA developed and tested a tile-repair kit, but dropped it when problems developed with the repair materials, according to former astronaut Charles Bolden.

NASA developed a system for astronauts to maneuver around the outside of the space shuttle and had planned to stow 162 repair tiles aboard each orbiter, along with various adhesives and fillers. But Bolden said there was serious concern that astronauts might cause additional damage by maneuvering around the delicate tiles, which are so fragile they can be nicked with a fingernail. Bolden also said the space agency could not find fillers and adhesives that would cure in a vacuum.

NASA revisited the issue of repairing tiles during orbit in recent years, researching the technology in a program at its Ames Research Center in Mountain View, Calif. But the effort was never fully developed.

The use of the space station would avoid some of the early problems. The tile-repair kits could be stored on the station and the robotic arm would give astronauts a stable platform for working.

The space shuttle often carries its own robotic arm, but a shorter and far less nimble version than the one carried by the space station.

Columbia was not carrying a robotic arm, but even if it had been, the arm could not have been used to see the portion of the craft believed to have been damaged, nor to repair any harm that had been done to the tiles, NASA officials have said.

NASA officials also said Monday that they have deciphered two more seconds of a garbled data stream emitted by the shuttle during its final moments Feb. 1.

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.

The data did not necessarily suggest that the astronauts were still alive and taking evasive action.

Investigators had hoped to learn much from the garbled transmission. They had determined that the shuttle had automatically fired rocket thrusters in an attempt to correct “drag,” resistance to aerodynamics.

But the data stream was in such poor condition that investigators at Mission Control in Houston have been largely frustrated in their efforts to interpret it.