It's late and way over budget, but the International Space Station should finally blast off today. Is it worth it? asks Julia Hinde

Plane-spotters and stargazers may soon have a new target in their sights. The first stage of Alpha, the long-awaited, much maligned and over-budget International Space Station, is scheduled to be launched today.

The size of two football pitches and travelling at 18,000 mph in an orbit more than 200 miles up, the station should be visible from earth. Eventually it will house six scientists, and when the Russian station Mir is abandoned next year, it will be humanity's only base in space.

What is less clear is the final cost of the project, its value in scientific terms, and whether the UK will have any role in this, or future, manned space missions.

³ÉÈËVRÊÓƵ

Zarya, the first segment of the station, is to be fired into space today aboard a Russian rocket. The launch of this Russian-built control module, which will act as the cornerstone for the assembly to come, marks the culmination of 14 years of planning, design - and delays. Hopefully, it heralds Zarya, or day-break, for the station itself, which is due to be completed by 2004.

Conceived by the Russians in 1984, the space station survived the end of the cold war to become an international programme involving both the US and Russia as well as 14 other nations (11 in Europe). According to Nasa, the station is the next step in man's exploration of space, offering world-class research opportunities. But few doubt that national pride and international politics (including a desire to gain access to the newly privatised Russian space industry) have played a large part in keeping the dream alive.

³ÉÈËVRÊÓƵ

For, despite this week's planned launch, Alpha's problems seem far from over. The Russian-built component that will house the astronauts is months behind schedule. Alpha should have been up and running six years ago to coincide with the 500th anniversary of Columbus's arrival in the New World.

Meanwhile, questions are being asked among scientists about the programme's usefulness. Some doubt whether the station can provide the vibration-free laboratory conditions needed to carry out key experiments.

Many scientists have also slammed the final cost, (estimated at between $50 and $100 billion) as unjustifiable. One US scientist argued that "the entire concept of putting a station up there has not been subjected to peer review". "Lots of basic science will be possible," said one British scientist, "but basically it's dabbling. Who can say if anything important will come out of it?" For the same amount of money, many argue, crucial scientific questions could be addressed - though it is pretty unlikely such money would be made available for other scientific projects if the station were cancelled.

Until now, Britain has stayed out of the saga. Though the UK is a member of the European Space Agency, Britain is one of four ESA countries that has refused to pay towards the space station. Nonetheless, experiments devised by UK scientists will be included on the space station's lab, Columbus, due for launch in 2001.

Now, following high-level approaches from the US and pressure from ESA, Britain's policy-makers are considering whether the UK, which signed the initial international space station agreement a decade ago but has done little since, should start to pay up. A spokeswoman for the British National Space Centre, the UK's space agency, said: "We are assessing what our attitude should be. There are still some UK groups that are interested in protein crystallisation and other work that could benefit from space station access. It's not clear how much it would cost."

The British space community is described by one insider as "polarised", both towards this space station and, generally, towards sending people into space. For some, missions involving astronauts represent the ultimate endeavour, while others see them as hugely wasteful. According to the BNSC, most things that UK scientists have wanted to do in space could be carried out by robots and machines.

For Nick Flowers, of University College London's Mullard Space Science Laboratory, trying to justify the costs of the station on science grounds alone is "indefensible". "This is a prestige project and a stepping stone to further exploration of the stars. If the UK becomes involved in any way, it will cripple our budgets. It would cost an awful lot of money and whether it's worth it, is something else."

³ÉÈËVRÊÓƵ

Ken Pounds, former chief executive of the Particle Physics and Astronomy Research Council, however, believes that the view that manned missions are not worth the money is too simplistic. "In the US, the more active the manned space programme, the greater the public interest's interest (in space exploration). That leads to money coming in for less popular areas of space science."

³ÉÈËVRÊÓƵ

For Robin Marshall, professor of physics at Manchester University, the UK's lack of involvement is frustrating. He says: "If you talk to anyone who is not a scientist, no one has heard of ESA, but everyone has heard of Nasa. Putting people into space is expensive, but it's all about human interest and human endeavour."

Will the British government share Professor Marshall's view and decide to start paying towards the space station? With the first stage of in-orbit construction today expected to become reality, the pressure is on Tony Blair to make up his mind.

WHAT THE SCIENTISTS HOPE TO ACHIEVE

A permanent manned space laboratory could study human physiology, enabling the muscle atrophy astronauts experience to be studied over long time-scales. It should also provide suitable conditions for studying crystallisation processes, the behaviour of materials at high temperatures and subtle fluid movements normally masked by gravity.

A questionmark still hangs over whether the station will provide the vibration-free environment essential for these projects. But having astronauts aboard means experiments can be changed.

The station will also provide a new facility from which to view the solar system. Future telescopes, too huge to be sent into space by themselves, could be pieced together in orbit.

Several British experiments have been accepted for the ESA laboratory:

* David Wynn-Williams of the British Antarctic Survey, will simulate a worst-case ozone hole scenario.

* Alan Chambers, lecturer in engineering materials at Southampton University, wants to measure atomic oxygen in space and to monitor how this corrodes metals. Though ESA has offered him room, he has yet to find the money to build the equipment.

³ÉÈËVRÊÓƵ

* Clive Dyer of the Defence Evaluation Research Agency is leading the Columbus Radiation Environmental Package, which is designed to measure radiation and cosmic ray levels in space.