With seven astronauts dead, bitter battles with the Bush administration over funding, its shuttle fleet grounded and an international space station only half built, Nasa has nowhere to go but up.
It must. There are two Americans and a Russian cosmonaut who had hoped to return to Earth aboard the space shuttle in March: they must now stay there until June. The challenge is to get them down, and get new crews in orbit.
Altogether, five space shuttle flights this year were to have delivered almost 40 tonnes of hardware, including two huge sets of solar panels to take Nasa's flagship from an orbiting space Portakabin to a space Hilton. It should also have delivered a new space laboratory, to be home to at least 30 experiments in 2003.
To have assembled all this metal, 200 miles above the Earth, astronauts and cosmonauts would have had to make 24 spacewalks, 18 of them while the shuttle was docked with the space station. The last big payload was to have been taken up by the shuttle in January 2004.
By then, the international space station was supposed to be 220 tonnes of sophisticated hardware, with kitchen and bedrooms attached, and a rebuke to critics who claimed that Nasa has spent $60bn (£38bn) on a political gesture and a show business arena in space.
A shadow now hangs over the whole venture. A Russian Progress supply ship blasted off on schedule yesterday for a rendezvous. Ron Dittemore, the shuttle's programme manager, said the existing crew had supplies enough to last until June. There will be pressure to keep the remaining three shuttles on the ground until Nasa engineers have finished their analysis of the catastrophe.
But time is not on Nasa's side. Harrison Schmitt, a former senator for New Mexico, and a geologist who walked on the moon on the last Apollo mission in 1972, said Nasa could not keep its fleet grounded for long. "You have to have enough confidence in the rest of the fleet to keep going... otherwise you don't have a fleet," he said.
The shuttle is Nasa's only workhorse. It was launched 22 years ago, to 30-year-old designs, to lift large military satellites into orbit, and its clumsy structure was a compromise between civilian and warrior needs. But by the 1990s, civilian investment in space had overtaken government spending, and private groups have moved into the launch market. Even Europe, with its troubled Ariane V rocket, was able to outperform the Americans at putting telecommunications satellites into high orbits.
Nasa's former chief Daniel Goldin tried to turn the US space agency into something swift and flexible: the mantra was "faster, better, cheaper".
But space is an unforgiving environment. When things go wrong, cost-cutting begins to look like folly. Engineers had begun to talk of faulty hardware and potential hazard. Andre Balogh, of Imperial College, one of the scientists behind the Ulysses space probe which has spent 10 years orbiting the sun, should have seen his mission launched by the ill-fated Challenger, years earlier. "I still feel that the shuttles at the moment are, on the whole, as safe as these things can be. Human space flight can never be without risk," he said. "A lot of people are wise after the event, a lot of people will say 'I told them so.' But in fact, safety is very much an open-ended issue. You cannot guarantee a 100% safe shuttle flight."
But, he warned, the generation of engineers and scientists who flowered during the Apollo programme were in their sixties. "They are going to retire, and I am not sure their experience has been passed on sufficiently."
He, like others, thinks that the shuttle will fly again. The agency has no other workhorse. There were elaborate plans in the last decade for a new generation craft that would fly into space and back again: Nasa now has just enough money to design a new kind of space taxi, but not a heavy goods vehicle.
There have been conferences to hammer out ways of propelling hardware across the solar system, from nuclear fusion propulsion to space sailing craft, but all are untried.
Nasa still has to hold its own in a competitive world. In June it plans to launch two landers for a touchdown on Mars, just days behind a European space agency orbiter with a tiny British lander called Beagle 2. Altogether, the US agency is involved at around 30 current missions to other parts of the solar system and is working with other groups on at least another 20. Europe has high ambitions.
The Japanese have moved into space exploration, the Indians have their eyes on the skies and the Chinese are rumoured to be preparing to sent a man into orbit this year.
The risks are high, but government space agencies are testing technologies which can then be exploited for profit. The catch is that while the potential rewards are high, so are the costs.
It costs roughly £10,000 to put 0.5kg (1lb) of payload into orbit. Both governments and commercial agencies are searching for ways to cut launch costs. But for the time being the tried and tested Russian Soyuz rockets, Atlas launchers and the shuttle will continue to use awesome quantities of propellant to put payloads up, and bring humans down.
"The space plane concepts have come and gone. My judgment, for the moment, is that they do not have a replacement," said Prof Balogh. "The shuttles will keep flying."
