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SHORTLY after Columbia broke up on re-entry, shuttle programme manager Ron Dittemore made what seemed to many to be a surprising statement. Despite NASA’s awareness that a piece of foam insulation had fallen from the shuttle’s external tank during lift-off, he said, mission control had decided not to make any attempt to photograph the shuttle’s underside to see if its heat-protection tiles were damaged.

Why not? There’s no doubt that NASA could have taken the pictures – it has done so before using spy satellites, and there are cameras on-board the International Space Station. Dittemore, however, said there was no point. “There was zero that we could do about it, and in this case, we elected not even to take the pictures.” (See “Nasa’s initial response”).

Seasoned NASA observers found themselves scratching their heads. What had happened to the agency’s “can-do” spirit, famously embodied in Apollo 13 flight director Gene Kranz’s declaration that “failure is not an option”?

NASA chief Sean O’Keefe has since put the record straight, saying that there would have been “no end of efforts” if a serious problem had been detected. And it now seems clear that if mission control had known there was a dangerous breach of the shuttle’s heat shield, they could have taken steps to save the lives of the seven astronauts.

That’s not to say NASA was negligent. There is no value in second-guessing decisions made under pressure by people who were doing their best to protect the lives of their close friends and colleagues – and a $1.5 billion spacecraft. But what might NASA do next time? The only way to answer that question is to think through what could have been done, so that if a future mission ends up in the terrifying position of being in orbit and knowing that it can’t possibly land, NASA can take every measure to prevent another catastrophe.

The first step, as soon as a problem was evident, would be to do what the crew of Apollo 13 did when an explosion on their craft placed them in immediate peril: conserve. The most important thing is to buy time, to give planners maximum opportunity to weigh up the options and develop contingency plans. Astronauts in space are critically dependent on the limited “consumables” that they have brought along, and the first strategy would be to minimise the consumption of all of these.

This is an idea, in fact, that astronauts talk about and train for. “When I was in the programme 14 years ago,” says former astronaut Frederick Hauck, veteran of three shuttle missions, “if you had to do a power-down, we had various degrees of power-down depending on how critical the situation was. I’m sure those procedures still exist.” The basic principle, in the most severe case, is to turn off everything that isn’t essential for survival.

On a mission like Columbia’s, the first thing to go would be the scientific experiments. Then after that would be the fans, lights and most other electrical equipment. Jeffrey Hoffman, a former scientist and astronaut who flew on five shuttle missions up until 1996, says that the scarcest resource during a mission is usually electrical power, which is generated on board by fuel cells that combine hydrogen and oxygen from special tanks at the rear of the orbiter to produce electricity and make water for the crew as a by-product.

Drinking water would not be a problem. The fuel cells produce it in such abundance that the excess is routinely jettisoned through a nozzle on the shuttle’s underside. Even in a power- down there would be enough for the crew. Food would not be an issue either. “You need to eat, but they carry extra,” Hoffman says. And with adequate water, people can survive for a long time without food. “You’re not going to die from that,” he says.

The earliest major problem would be the build-up of carbon dioxide from the astronauts’ breath. This would almost certainly happen before the oxygen supply ran out. Canisters full of an absorbent material are used to remove excess CO₂, but there are only a limited number of these on board. James Oberg, an aerospace engineer turned author who worked for 22 years at mission control at NASA’s Johnson Space Center, thinks CO₂ levels might be the deciding factor in the length of time astronauts could survive in a shuttle. “This is the gas that kills people in closed spaces. CO₂ accumulates in your blood and turns acidic, killing your brain cells,” Oberg wrote recently.

So what can a crew do to extend the time available? One option is to restrict all activity to lower the respiration rate, as the Apollo 13 crew did. However, it may be possible to survive a build-up of CO₂ for longer than previously thought. High levels of the gas are a familiar problem for submarine crews, and also to the eight people who lived for two years inside the sealed environment of Biosphere 2 in Arizona. In both cases, people have been able to survive in CO₂ levels at least 20 times greater than normal, with no long-term ill effects.

As Hoffman told 91av: “If you knew right at the beginning that you had a problem, you would go into full power-down mode, and you could probably double, or even more, the amount of time you could stay up. You just go into survival mode.” Columbia’s mission was planned to last 16 days, which means the crew might have been able to buy themselves more than a month – perhaps enough time for NASA to mount a dramatic rescue bid.

But what form could a rescue have taken? One obvious possibility would be to head for the International Space Station and await a mercy mission. Unfortunately, for Columbia, this was never an option. The space station was utterly out of reach for two reasons: Columbia’s orbit was too low, and it was at the wrong angle. Columbia was the first shuttle built and is heavier than the other three, so it could never reach the higher altitude of the space station. Because of this, it was limited to missions for scientific research, launching spacecraft or servicing the Hubble Space Telescope. In addition, it was launched in an orbit tilted at 40 degrees to the equator, whereas the station’s orbit is tilted at 51.6 degrees in order to make it accessible to the Russian Soyuz and Progress spacecraft, which can only reach such an orbit. To reach the space station it would have had to wait for their orbits to overlap then make what is called a “plane change”. But altering the inclination of an orbit in this way requires prodigious amounts of energy, and even if Columbia could have boosted to the right altitude it would not have had enough fuel to change orbits.

Future missions, though, could use the space station as a sanctuary. One possibility would be to require that all shuttle flights go into an orbit within reach of the station, even if they are not planning to visit it. In the event of an accident the shuttle could limp to the space station and await rescue.

Depending on the nature of the problem, that rescue mission could also bring along equipment to repair the damaged shuttle and allow it to return safely. If no such repair was possible – as is the case with tile damage – the damaged shuttle could just be left docked to the station indefinitely, providing extra space for living and research, and its crew could return home on the rescue shuttle.

Alternatively, if the problem turned out to be a generic one that precluded the launch of a rescue shuttle, the crew could return in Soyuz capsules. It would take three of the three-person capsules to bring back all of a seven-member crew like Columbia’s, but the station’s ample stores, and its capability for being resupplied by unmanned Progress craft, would provide sufficient time for that.

Even without the space station there would still have been a chance to get Columbia’s crew home. Oberg says that shuttle engineers have told him that another shuttle could be rushed through its launch preparations, which normally take four months, in as little as two weeks if one were already assembled and ready – as Atlantis actually was in this case. A shuttle can fly with a minimum crew of two and a maximum of nine, so rescuing a crew of seven would just be possible.

Although NASA has never developed a detailed plan for a rendezvous between two shuttles, it did consider the option early on in the shuttle programme. At one time there was even talk about always having a second shuttle and crew on standby during missions, ready to launch quickly in case of an emergency, says Charles Oman, a senior researcher in aeronautics and astronautics at the Massachusetts Institute of Technology. But such a rescue mission “would be a major technical challenge”, he says.

For one thing, there is no way for two shuttles to dock together, so they would have to rendezvous and then stay as close as possible without colliding: a delicate orbital minuet, but not impossible. Then would come the really tricky bit: the astronauts would have to space walk across the gap.

Performing a mass space walk would be no easy matter. Each crew member would have to spend hours in the airlock donning a spacesuit and acclimatising to its high oxygen levels. This process would have to be repeated for each astronaut, because only one can fit in the airlock at a time. So the whole process of transferring a crew of seven might extend over two or more days.

What’s more, the suits are bulky and heavy and most shuttle missions only carry a few – Columbia had two for its crew of seven. So, because of the time that would be involved in exchanging suits, any rescue mission would have to bring up enough spacesuits for all of the crew to be rescued, as well as for the rescuers.

Still, if – and that’s a very big if – it was clear that the only alternative was the awful fate that befell the Columbia’s crew, there is little doubt that NASA would have pulled out all the stops to try to plan such a mission. As Oberg puts it, “it’s the sort of ‘impossible’ contingency that the mission control team (and their ‘bolt-turner’ buddies on the launch crews at Cape Canaveral) could really sink their teeth into.”

Will such contingency planning be part of the reforms that will follow the Columbia accident investigation? There’s no telling, especially at this stage when the actual cause of the accident is not yet known – as, indeed, it may never be.

However, if the previous shuttle accident is anything to go by, NASA will learn valuable lessons from the loss of Columbia. In the aftermath of Challenger’s explosive demise during lift-off in 1986, NASA made a set of changes to improve the odds that a crew might survive any similar accident in the future. Shuttle crews ever since have been equipped with parachutes, pressure suits and a system for escaping from the shuttle if they know it is going down. Lessons were learned, and the margin of safety was improved.

In many respects, though, the question of safety is a relative one. How safe is safe enough, when dealing with something as inherently harsh and dangerous as space travel? The answers that people involved in the space programme have come up with might shock the public, the politicians who control the purse strings, and even the teachers and members of Congress who readily volunteer to travel into the harsh but stunningly beautiful environment of near-Earth space.

“I’ve asked a number of people – astronauts, payload specialists and students,” says Oman. Typically, he says, people say: “1 in 10 is not OK, unless there was something historically momentous about the mission. Apollo astronauts, for example, were willing to take 1 in 10.” For most astronauts and most missions, he says, “I believe the crew thought it was on the order of 1 in 100, and that was an acceptable number.”

Shuttle veteran Hauck adds: “I never thought of it quantitatively. I just knew it was risky.” To him risk was nothing new, and this was the case for most of the astronauts, at least in the earlier days of the programme. “I came out of the Navy, and in my test-pilot experience, it would take more than both hands to count the number of friends and acquaintances who were lost,” says Hauck.

Ultimately, though, the arbiter of safety is not what is possible, nor the level of risk the astronauts are prepared to bear. It’s cost. “There may be things people might want,” says Hoffman. “The question will be, ‘how little improvement, for how much money?'”