Countdown to shuttle return flight

By David Shukman
BBC science correspondent

The shuttle is due to return to flight in May

Step out of the Florida heat into the cavernous Vehicle Assembly Building at the US space agency's (Nasa) launch complex at the Kennedy Space Center and you enter a cool, dark cathedral to spaceflight.

It is a structure more than 50 storeys high that has witnessed the greatest and the worst moments of America's ventures into the heavens.

It was here that the giant Saturn rockets were pieced together before the Apollo missions to the Moon.

So it's no surprise that everything about this place is measured in superlatives: the massive doors, the vast gantries, the impossibly complicated engineering required to get into orbit and beyond.

Painful memories

The cranes and catwalks and mobile platforms are now frantically busy once more as engineers prepare for an event which could prove pivotal for the future of Nasa: getting the space shuttle flying again.

Nasa only has three of the spacecraft left, so this mission cannot fail. A provisional launch date has been set for 12 May.

Shuttle crew member Andy Thomas is glad preparations are nearing an end

Overshadowing the work are the memories of the last shuttle to fly: Columbia, the spacecraft that was damaged on takeoff and then ripped apart during its descent, as superheated gases worked their way into a hole on the left wing and led to the deaths of all seven astronauts on board.

Columbia memorabilia decorate rooms and corridors here, a constant reminder of a series of mistakes and circumstances that proved fatal.

Close scrutiny

Nasa was sharply criticised by the accident investigators for tolerating a culture in which potential risks were played down - and in which concerns for safety were too often ignored.

Today the managers and astronauts I encounter are open about the organisation's failings. Andy Thomas, one of the crew preparing for the next flight, is disarmingly frank.

The shuttle's external fuel tank has arrived at Kennedy

Out on the runway, where he's just landed after a flight from the training centre at Houston, he says he knows of no other institution that would have listened to the criticisms and then put itself through such a searing self-examination.

The result is that no shuttle flight will have been better prepared. I watched as the shuttle Discovery was minutely checked.

The huge craft was engulfed in scaffolding and every vantage point was filled with technicians fitting a multitude of parts; Nasa supervisors were overseeing the work of private contractors.

Most critical are the panels on the leading edges of the wings. These are made of reinforced carbon and it was one of these that was fractured by a lump of loose insulating foam during takeoff.

Clearing the decks

There's an air of real purpose, a desire to convince visitors like me that technical problems have been overcome, that the can-do spirit that caught the public imagination back in the 60s for the Moon shots is alive again.

A new repair kit will be able to patch damage on the shuttle exterior

The truth is that Nasa desperately needs this next mission to work. Only the shuttle has the capacity to carry into orbit the building blocks for the International Space Station (ISS) and there's an eagerness to get that task over and done.

That would clear the decks for the more glamorous roles of heading beyond orbit to the Moon and on to Mars.

The viewing stands are ready. The broadcasting cabins of the television networks, installed for the Moon shots, are poised.

I meet the man who, on that fast-approaching May morning, will utter those famous words, "give me a go or no-go for launch".

Mike Leinbach seems focused but calm. So will he be nervous? Sure, he says. He won't be alone.