Nasa rescue options for crew were 'desperate'

Desperate measures would have been needed to save the seven crew of the space shuttle Columbia, or the spacecraft itself, even if controllers had suspected its heat shield was damaged on take-off.

Assuming there had been suspicion about problems with the thousands of ceramic tiles, many options at first seem promising: docking with the International Space Station (ISS), to take refuge there; inspecting and perhaps mending the tiles in space; or waiting in orbit for a rescue mission by an American or Russian rocket.

Nasa staff and independent experts said yesterday that none of the possibilities had any chance of working, although as James Oberg, a former shuttle flight controller, observed: "They may be implausible, but not by much; there's always the question of miracles."

And indeed miracles would have been needed. Columbia was not intended to dock with the ISS. The two craft did pass within a few hundred miles of each, but getting the two craft together would require huge amounts of fuel.

"The ISS is on an orbit that's inclined at 66 degrees to the Equator, and Columbia was on one at 29 degrees," said Chris Welch, principal lecturer in space engineering at Kingston University in Surrey. "In space, it's not as simple as just pressing an accelerator. You have to go into a lower orbit to catch up, then change orbit to the same altitude as the object you're after, then perform other maneouvres. It's not even clear whether Columbia had enough fuel to dock with the ISS."

Nasa said Columbia could not have docked with the space station, so the crew would have had to make the crossing inside their spacesuits, protected by huge fabric "balls" developed for such contingencies. But if the crossing had been achieved the seven astronauts could have taken refuge to await the next shuttle launch.

The next option might have been repair. But Nasa knew a piece of insulation had come off the solid rocket boosters about a minute into the launch and did not believe it had caused a problem. "We went through the gamut of discussion [about what to do]," Ron Dittemore, Nasa's space shuttle programme manager, said. "Our technical experts believed the debris that hit [the shuttle] was inconsequential. It was not going to represent an impact to our flight control qualities or its safety."

The chance was not taken to view any damage using the ISS's telescopes; an attempt in 1998 to check the shuttle Discovery's parachute revealed nothing useful.

Early in the shuttle programme, Nasa realised that if important tiles were lost from the belly of the craft, it could be disastrous. Mr Dittemore said Nasa tried to develop a method for orbital tile repairs, and abandoned it. The belly of the craft is smooth, with no anchor points (because those would be points of weakness on re-entry). The tiles are fragile, half an inch thick, made of silicon glass. And it gets worse. Dr Welch said: "Every tile is individually shaped. They're black, with a yellow number and ID code on each saying where it should go." The underside has 28,000 tiles. Carrying enough for repairs would be unfeasible. And no stock of the special glue used to fix them is on board.

Mr Dittemore added: "We were also concerned that if you send a spacewalk crew member underneath the vehicle [because the spacewalk exit is on the top of the shuttle] that just the nature of them trying to position themselves in space underneath the vehicle could cause more damage than what we were trying to fix." Columbia did not carry a jetpack, so the spacewalker might have drifted off into space. The operation could have taken eight hours; spacesuits cannot carry that much oxygen.

What about taking refuge in the shuttle itself until rescue spacecraft could be sent up? Dr Welch said: "They would be limited by the amount of oxygen they could produce on board. They probably couldn't stay there for longer than three weeks." And getting a shuttle up would be risky. Launch procedures would be rushed, though Nasa said it could have readied Atlantis in one week. Again, the crew would have had to use spacesuits; shuttles cannot dock together.

"My gut feeling is that the ISS would have been the best bet," Dr Welch said. "It would have meant they were safe for a certain period, if they could get there at all."

A final possibility would have been to take a shallower entry into the Earth's atmosphere, hoping to lessen the heating effect on the ship. But that might have left it entering the atmosphere too fast, uncontrollable for a safe landing.

The last possibility would see the astronauts marooned in space, unreachable from the ground, and unable to return safely. Eventually they would have suffocated, and the shuttle would have fallen flaming to Earth. Mr Oberg said: "It would be visible at dawn and dusk [during its orbit] and that would be creepy. It would be a Viking funeral."

Was there any hope? The alternatives

Head for International Space Station

Would not work because the ISS and Columbia were in different orbits, and Columbia did not have enough fuel to fly to it. Even if it could have reached the space station, it could not have docked as it does not have the correct "docking-ring" to link up.

Fix the tiles in space

Would not work because the tiles are individually made, no repair materials are carried on the shuttles, and there is nothing to anchor to on the underside of the spacecraft. The shuttle also had no jet-pack, so the person doing the repairs might have floated off into space.

Wait on 'Columbia' for another shuttle

Might have worked, depending how quickly the shuttle Atlantis could be readied. Nasa says it might have been able to have it ready in a week, but any delay could mean severe problems for the orbiting astronauts, who would start to run short of oxygen.

Wait on 'Columbia' for a Russian Soyuz rocket

Would not work because the Soyuz has too little space for non-essential crew. It carries three people at take-off, and has room for only one other. Russia also schedules a Soyuz flight only once every six months, and the next was not due for months.

Enter atmosphere at a less steep angle

Would not work because even if the tiles withstood the still-extreme heat, the shuttle would not have lost enough of its energy. Like a stone skipping over a pond, it would still be moving too swiftly to make a safe landing on the ground.