By BBC News Online's Ivan Noble

The first crew of the International Space Station - Expedition One - took up residence on 2 November, 2000. They opened the hatch on their new home at about 1100 GMT.

The American space agency describes the first anniversary of this event as "a milestone in space history".

"The station is the largest international engineering project ever undertaken in space, and it is the first truly global space exploration effort," said Nasa's International Space Station program director, Tommy Holloway.

ISS visitors and residents

79 total 68 men 11 women 58 from US 15 from Russia 3 from Canada 1 from France 1 from Italy 1 from Japan

"Its unprecedented scale in orbital size and capability will be matched in the future by the scale of the benefits its research will bring to lives on Earth," he said.

But does manned spaceflight really make scientific and economic sense?

'No practical case'

Sir Martin Rees, Astronomer Royal in the UK, thinks not.

"I think there is no practical or scientific case - it's getting weaker all the time as miniaturisation and robotics advance.

"However, in the long run, I support the case for 'space colonies', but I believe this will be done by free-enterprise risk-taking adventurers rather than a government programme," he told BBC News Online.

Space tourist Dennis Tito reportedly paid millions to climb aboard

Maarten Meerman, principal engineer at Surrey Satellite Technologies, Ltd, takes a "horses for courses" view.

"If we actually wish for Star Trek-like space travel to become a reality we have to do lots of hard study...

"Having humans there allows development to go much quicker than when it has to happen through remote operations by radio link. Ever tried to help someone over the phone to fix their computer?" he asked.

"Unmanned spacecraft on the other hand can also do a lot of science... and there are many tasks which a small satellite can do as well or better than an astronaut.

"By definition, having a human in space is very expensive. The answer is that some tasks are better suited to astronauts and some should be done by unmanned missions," he added.

'Not proven'

The British National Space Centre thinks the exploration of space is a good thing, but the case for manned space travel is "not proven".

Sending people into space is pointless. It is dangerous, costly and scientifically useless

The Economist

Advising the government on whether to put a British astronaut on to the ISS, the centre said:

"Following consultation with industry and the science sector, we concluded that the provision of an astronaut did not best meet our priorities of commercial exploitation and good space science.

"Within the inevitably limited funds we have available, we must prioritise in the best interests of the British space science community and industry."

Wright brothers comparison

The Economist newspaper is unequivocal: "Sending people into space is pointless. It is dangerous, costly and scientifically useless," it said in a recent editorial.

The ISS project is about showmanship, the US staying friends with Russia, keeping Russian scientists out of mischief and a disguised subsidy to the aerospace industry worth billions of dollars, it said.

But, as Maarten Meerman observes: "There may not be an obvious need for an ISS, but then again, there was no need for the Wright brothers, mobile phones, or TV soap operas.

"Yet, when they are there we cannot do without them anymore, and who would say no to a holiday into space?"