World's largest prefab heads for orbit

THE WORLD'S most ambitious building project begins this week, with the launch of the first of 45 rockets to build an orbiting space station as big as two football fields.

Yet even before the launch, the project to construct the International Space Station (ISS) has run into huge problems, including massive cost overruns and continual arguments between the United States and Russia, even over issues as trivial as the station's name. (The US favoured Freedom; Russia thought that sounded like a snide comment on the Cold War. Presently "ISS" is the compromise.)

More serious though are calculations which suggest that during its planned 20-year life, and associated rocket trips, the ISS stands a real chance of suffering a catastrophe which could kill astronauts - and perhaps leave them whirling lifeless around the Earth forever.

The principal hazards include a rocket explosion on liftoff, and a strike on the huge area of the station either by orbiting "space junk",which includes thousands of tiny metal fragments, including dropped tools from previous space missions, or meteorites.

The threat of being hit is very serious. To put the ISS together, the astronauts will have to carry out 1,000 hours of spacewalks. By comparison, the record length spent outside so far is 30 hours, on the second Hubble Space Telescope repair mission in 1997.

Space junk makes spacewalks - and life on the ISS - risky. A pebble-sized object would carry the kinetic energy of a car travelling faster than 100mph, and a direct hit on any astronaut or on the station could be fatal.

The size of the station, with 4,000 square metres of solar panels, will be a huge target. A Nasa analyst, Eric Chrsitiansen, has calculated there is a 42 per cent chance of one of the ISS's 30 modules being penetrated by an outside object during its 20-year life. What nobody knows is whether it would cause an explosion, or just a slow leak that could be plugged.

Yet Nasa has not completed a formal risk assessment on the project, and last week Julie Swain, a member of Nasa's independent Advisory Council, told New Scientist magazine: "the opportunity for something to go wrong is phenomenal".

She thinks that something - perhaps major - is bound to go wrong, by the laws of statistics: "It's dangerous. It will always be dangerous. It ought to be expected that people are going to die," she said.

Thus there will be many crossed fingers amid the celebrations on Friday when a Russian Proton-4 rocket takes off from the remote Kazakhstan desert carrying a cargo module, Zarya, with propulsion, command and control systems for the ISS. A fortnight later the US Space Shuttle Endeavour will take off from the more prestigious Kennedy Space Facility, bearing a cornerstone of the ISS - its Unity connecting module, to which all the US's pieces will connect in future.

The US space agency Nasa was upbeat as the launch process moved towards completion. "Unity represents the first new human spacecraft to go to a Kennedy launch pad since the Shuttle launch 17 years ago," said Steve Francois, director of payloads. "The era of the ISS is here."

If so, it's very late. The ISS was first suggested by Ronald Reagan in 1984. First plans were that it would cost $8bn (pounds 4.8bn), and be finished by 1994. Presently those figures look more like $50bn - or perhaps $100bn - with construction finishing in 2003, though it should provide a permanent station for at least three astronauts from July next year.

Once complete, it will offer a crew of seven a choice of five pressurised laboratories with attached external sites for research. It could also be a useful waystation for future exploration of the solar system. But some scientists remain doubtful it will ever pay its way, because of the associated costs of reaching it: every Shuttle launch costs about $400m. "If Rumpelstiltskin took straw into space and spun it into gold, he'd still lose money," quipped one materials scientist. .

Meanwhile, as Russia's economy has slumped, the US has been forced to shoulder more of the burden of designing and paying for the ISS. Though there are 16 partners in the project (including Britain) - Nasa has had to drive the project.

Dan Goldin, the normally upbeat head of Nasa, told Congress last month that the problems with the ISS had forced him to consider resigning. Instead, he demanded $1.2bn more funding from Congress: "If we can't get the money, maybe we ought just to cancel it," he challenged.