@helgoland: Pfft, there's PLENTY of non-propoganda reasons to keep a space station in orbit, like say, science, and as a mid point between stations on the moon or mars.
So, we can use a space station to support other space stations. And most science can be done via sattelites much cheaper than via the ISS. The only science that can not be done using robotic experiments is science on humans in space, and that science only serves to allow us to keep humans in space longer.
So really , manned space stations have no other purpose than allowing for other manned space stations.
As for decommissioning it after 2020, what are we going to replace it with? Unless they mean decommission as in hand over to private companies.
Decommision as in dumping it out of orbit. As in, this manned space program thingy turned out to be a dramatic waste of money, and we're not replacing it.
Each man day on the ISS costs 7.5 million dollar. Comparison, a single rocket launch costs 50-60 million dollar for a midsized flight.
You could send them back down for maintenance, either single robots or whole modules... I'm fairly certain we could build a fully automatic space station if we wanted to. Sattelites work without human interference, after all.
Actually, there's little point in having a space station. Just send up (re-useable) lab sattelites. It's how the majority of space based science happens.
As for decommissioning it after 2020, what are we going to replace it with? Unless they mean decommission as in hand over to private companies.
The decommissioning thing is that the structural integrity starts to dangerously erode after 2028 or so requiring either major repairs or ending the mission and going back to the drawing board. Personally I see the merits in both ideas.
Actually, the 2020 decommision data was purely for financial reasons, it's off the tables now, with the station being funded till 2024.