ISS: 'the benefits have been tremendous'
This week, two astronauts worked outside the International Space Station hundreds of kilometres above the Earth in the second of two space walks in as many weeks.
After years of construction work, the space station is formally complete, and with the station running well, space walks are becoming less common.
Meanwhile, the death of the astronaut Neil Armstrong and the presence of the rover Curiosity on the Martian surface, has led to renewed questions about the goals and visions of the orbiting space platform.
Sam Scimemi, deputy director for the International Space Station Programme at the US space agency Nasa, spoke to BBC News about the future of the ISS.
What has the ISS achieved so far in terms of international collaboration?
First of all the programme, which began in 1984 - if you can believe it's been that long - has spanned a long history of international collaboration beginning first during the Cold War with our European, Canadian and Japanese counterparts. When the programme was changed in 1995, we brought the Russians on, combining their space station programme with our space station programme. So as far as international collaboration, it's been a huge success even though it started off... difficult in so many technical, diplomatic (ways) and the like. It has really matured in a way that no-one's ever really expected, it's had a really deep and profound relationship between all the partnership.
What about scientifically?
Scientifically, for the most part, the space station has been concentrating on how micro-gravity affects the human body and we've also just begun doing studies on other areas such as technology development for extending human presence beyond low-Earth orbit. We've also spent many years to date on micro-gravity effects for biological and the physical sciences, we've begun to see results in things like bone density and bone disease, that may be coming out soon. We've also seen other effects on bacteria and its effects in zero gravity and how that might affect vaccines here on the Earth.
How would you justify the costs of the ISS - $100bn or more - to an ordinary citizen?
Human life and everything here on Earth has evolved in a gravity environment. To escape that gravity environment is expensive, and it's difficult, it's dangerous. The cost to make sure that it's safe and viable for humans to operate in - there's a high price for that. And the research that follows on to humans being in space adds to all that. The cost is quite high compared to doing that same type of research here on Earth. So in order to get the benefit of taking gravity away, there is a high price. But we believe that in the research to come that we will see benefits... of taking gravity away from the research we do here on the Earth.This is a peaceful endeavour - the largest peaceful endeavour in history - and the benefits have been tremendous, here on Earth on a diplomatic level and on a cooperation level that you really can't get a cost out of.
Is the vision of the ISS as a jumping-off point for the Moon and beyond still on the cards?
The space station's still being used to develop all the operational techniques, the technology, and experience of sending humans beyond low-Earth orbit. As far as a "jumping off point", like you'd use from an airport or the like, that's still under investigation.