God, the Russians and unk-unks willing

Karl Sabbagh looks at the gamble of putting the International Space Station into orbit piece by piece and why British scientists don't want to play

Recently Mike Foale, the British-born Nasa astronaut, tried to explain the rationale for the International Space Station: "When the federal government decided to lay down straight highways all the way across America through land that wasn't used, if you just looked at it narrowly, you'd say, 'Why are we doing this? It's a road to nowhere'. Well, as soon as you put the road down, the towns spring up, industries develop and suddenly the whole country is wealthier. That's the analogy I would apply to the exploration of space. The space station is like the first piece of that highway."

It is not surprising that Foale now lives and works in Houston. As someone with a passion for the manned exploration of space, he would find little to occupy him in British science at the moment. Our government has decided that it would rather put what limited money it has for astronomy into unmanned projects. But then Pounds 200 million - our government's annual spend on space - would probably go unnoticed in the much larger Space Station budget, estimated at $20 billion. Over the past two and a half years, one of the most complex technological projects the world has ever seen has been occupying thousands of scientists and engineers, many of them British emigres, in Houston, Huntsville, and Huntington Beach, as well as in Canada, Russia, Japan and Italy.

So what are they trying to achieve? Imagine trying to make a new type of car by first designing and manufacturing the engine in Britain, then sending it to the United States, while you design and manufacture the axles and gearbox. Send those off and get designing the chassis, wheels and brakes, and so on, sending off each element as it is manufactured to be connected to the growing car on the other side of the Atlantic. That car will have to drive away smoothly as soon as the final component arrives.

Although small components of the space station will be replaceable, the 20 or so modules that will make up the 100-metre-long orbiting laboratory are unique. There is no redundancy at that level - no backup plan that would not involve a halt in the assembly schedule while, say, a test article is made flightworthy. Yet the station as a whole will never have been assembled on the ground to ensure that all the systems work together.

The on-orbit assembly has already begun. Last November, the first piece of the station, the Russian module Zarya, was put into orbit from the Russian Cosmodrome in Baikonur, followed three weeks later by the American module Unity. Then, in a test of a process that will have to succeed dozens of times, two astronauts carried out spacewalks over several days to connect power and communications systems between the two.

I watched from Mission Control in Houston as astronaut Jerry Ross poked a long pole at an aerial on Zarya that had failed to deploy after launch. Earlier in the year he had told me about a holiday he and his wife had taken in Scotland. When I asked him if he had hired a car, he said, "No, I was afraid to drive on the wrong side of the road." Now, he was orbiting the earth nearly 200 miles up in a spacesuit, trying to carry out a delicate manoeuvre, instructed by an engineering team on the ground.

A thousand issues like this crop up on every mission and as more components are launched from February, a series of increasingly complex spacewalks will be needed to attach modules supplying accommodation, laboratories, propulsion units and power-generating equipment. An array of laboratory facilities will facilitate experiments submitted by scientists from around the world. There will also be comprehensive medical and biological test facilities for monitoring the effects on the human body of long periods in zero gravity.

Nasa - and Boeing, its prime contractor - have presented the space station to the US public as if its main justification is the future scientific and medical benefits to mankind. But as one senior Boeing manager, Royce Mitchell, told me: "When you have a multimillion-dollar programme, people want to know whyI And when you can't give them a specific answer, such as, we are going to find the answer to cancer or poverty on Earth, then it rubs people up the wrong way - including our leaders."

In fact, making promises that cannot be kept is a worse tactic than defending the space station on the grounds that if mankind is ever going to move away from Earth, we need to learn a lot about space construction, complex systems integration, recyclable life support systems, and, most important, how to overcome the physiological problems of long-stay spaceflight. The International Space Station is meant to provide a unique research tool for finding the answers to all these questions.

Then there is the romantic justification. In the words of Boeing's space station manager, Brewster Shaw: "I believe in it and I think it's the right thing for us to do. I believed in the Ni$a, the Pinta and the Santa Maria, and all the wagon trains... If we can demonstrate that we can assemble this thing called International Space Station, in orbit above this Earth, I think we will have demonstrated to ourselves, as human beings, that we can assemble a place to live and work anywhere we can get to."

But it's a big "if". One obstacle is the Russian participation in the programme, seen initially as a life-saver when the US Congress ordered a budget cut to the project. Now, lack of Russian funding, which is leading to schedule delays, could deal a death blow. Even the most pro-Russian Nasa engineers are beginning to wish the collaboration had never existed. Gordon Ducote, the payload manager for the Russian Service Module, the next piece to be launched into orbit, says: "If I had to do it over again, would I? I There are many nights when I go home drained and I'd say 'no, I wouldn't'."

It is a project full of what Americans call "unk-unks" - unknown unknowns. There are so many things that can go wrong. With dozens of astronauts needed over the next four years for assembly, then ten more years to run the station, more lives are at risk than in any previous US space programme. But one thing is clear. Until now, despite ten years of research and development, the International Space Station has not been much in the headlines. The scale of future activity is going to change that.

Space Station, a two-part documentary produced by Karl Sabbagh and Belinda Aird, airs at 4pm on Channel4, November and December 4.