A Damaged Shuttle, Once in Orbit, Has Nowhere to Turn

In the aftermath of the Columbia disaster, a question lingering amid the sorrowful assessments of loss is whether anything could have been done to rescue the seven astronauts had NASA determined that the orbiter was too damaged for a safe reentry.

The short answer: No.

“If they [NASA] had known very early in the launch that there was a problem, they might have been able to abort the launch and come back in to land,” said aerospace engineer Mark J. Lewis of the University of Maryland. “Once the astronauts were in orbit, however, there is not a thing they could have done.”

NASA has not yet determined why Columbia disintegrated, but the early investigation has focused on an unusual temperature rise in the left wheel well that might have been caused by damage to its insulating tiles. Images obtained during liftoff showed that a piece of foam broke away from the external fuel tank and hit the left wing, possibly damaging the tiles and leaving the craft vulnerable to heat during reentry.

Despite the best efforts of countless engineers, no one has devised a way to retrieve a damaged spacecraft from orbit or to protect astronauts from a catastrophe on reentry. Any conceivable safety system would add too much weight or be unfeasible because of the extreme temperatures and speed of reentry.

“Rockets are systems that almost don’t work,” Lewis said. “The amount you can put into orbit is really very small” compared with the total weight of the rocket, he said.

Adding extra safety features would reduce the amount of cargo and number of people the shuttle could carry.

NASA made a conscious decision to accept the risks associated with reentry as part of the cost of manned missions.

“You build fail-safes into the shuttle so that these scenarios don’t happen, but there is always a very small chance that they will occur anyway,” said aeronautical engineer William Ailor of Aerospace Corp.

NASA scientists always have known that reentry is one of the most critical and dangerous phases of spaceflight, though the U.S. had never lost a spacecraft during reentry in 42 years of manned missions.

Four Soviet cosmonauts have perished in two accidents. In April 1967, Vladimir Komarov died when the cords on the parachute meant to slow his craft tangled, allowing the Soyuz I to plunge to the ground. Four years later, Georgy Dobrovolsky, Vladislav Volkov and Victor Patsayev suffocated during reentry. The Soviets had placed three men in a Soyuz designed for two, so there was no room for spacesuits. The men, descending in shirt sleeves, died when the capsule depressurized.

After Columbia’s launch Jan. 16, NASA officials closely examined the impact of the peeled-off foam on the wing, did modeling studies and determined that the event had produced no significant damage. If damage had been found, however, Space Shuttle Program Manager Ron Dittemore said, they had no contingency rescue plan.

“There was zero we could do about it,” Dittemore said.

The orbiter carries no spare tiles or repair equipment. Each tile on the orbiter’s skin has a unique shape, and it is impossible to predict which ones might be needed. Also, gluing them into place in orbit would be difficult, not only in terms of curing the adhesive but also of simply reaching the areas to be repaired. The orbiter does not normally carry the backpacks astronauts use for spacewalks, the belly of the shuttle has no handholds for maneuvering and the remote manipulating system -- the shuttle’s long mechanical arm -- was not carried on this flight because it was not needed for the science experiments.

Although NASA engineers tried to develop a system to repair tiles in orbit, “We eventually concluded that we risked creating more damage than what we were trying to repair,” Dittemore said Sunday, explaining that just the jostling of an astronaut against the exterior of the spacecraft could damage it.

Ground-based observers have suggested that the international space station might have offered a safe port, but there was no way that Columbia could have reached it. Changing orbits once a craft is in space requires tremendous amounts of fuel and the orbiter carried only enough to initiate reentry.

And rescue by a second shuttle mission would not have been a viable option. Processing a shuttle after one mission to prepare it for the next requires weeks or months, depending on the mission and any damage that might have occurred on its previous flight. The shuttle Atlantis was scheduled to be launched March 1, but experts doubt that it could have been prepped quick enough to rescue the crew of Columbia, which carried enough oxygen for only a few days.

Furthermore, NASA officials almost certainly would be reluctant to launch another shuttle mission if one were damaged during liftoff, running the risk of stranding two crews in orbit, Lewis said.

And finally, the shuttle carries a maximum of seven people. There were seven crew members aboard Columbia, and at least two would be required to run a rescue mission. “Where would they put them all?” Lewis asked.

Ejection seats and escape pods are not built into orbiters. Early U.S. space vehicles such as the Mercury, Gemini and Apollo craft had escape systems designed to blast the capsule away from its rocket in the event of a launch failure. But they had nothing that would be useful during reentry.

The first shuttle orbiter had ejection seats for the two pilots, but those could have been used only in limited situations -- essentially when the orbiter was traveling at a speed of Mach 3 or less, Lewis said. At higher speeds, a human is unlikely to survive an ejection. At the time of the Columbia’s destruction, it was traveling at Mach 18 (12,500 mph) with a wing temperature of about 3,000 degrees.

Even if ejection seats were feasible, only the four astronauts on the upper deck of the orbiter would be able to use them, leaving no escape system for the three mission specialists on the lower deck.

After the Challenger accident in 1986, some thought was given to incorporating an escape pod into the orbiters, but the idea was discarded because it would require major structural changes in the orbiter without assuring crew safety, NASA’s then-manager of crew escape systems, William A. Chandler, said at the time.

The breakup of Columbia occurred abruptly, so it is unlikely that the crew would have had time to enter an escape pod even if one were aboard, Ailor noted.

The two points during a mission when there is a possibility of rescue are during launch and immediately before landing. Once the orbiter is detached from the solid rocket boosters, about two minutes after liftoff, it can separate from the external fuel tank and descend to Earth for a landing at one of several sites. Such a reentry can be accomplished within the first nine minutes of flight, before the craft achieves orbital velocity.

After the Challenger explosion, NASA engineers installed an escape system that can be used when the spacecraft is flying level at relatively low speeds. That system involves parachutes and an extendable pole that would guide escaping astronauts past the wing.