Actually they would be using nuclear if there wasn't huge public out cry about launching a reactor into space. Also we would be using much more efficient nuclear rockets
http://en.wikipedia.org/wiki/Project_Prometheus
http://en.wikipedia.org/wiki/Nuclear_thermal_rocket

These are the kind of posts that make treehugger look silly.

Where is all the silicon comming from? I simply don't like sullying up someone elses back yard. There are new technologies comming up, and the interest in soloar is growing. Let's make it all it could be (not setting up major silicon based systems for cities...).

Jilted, no, they wouldn't be using nuclear power on ISS. Nuclear Thermal Rockets were conceived for interplanetary travel, not launch from Earth.

Project Prometheus is meant to provide nuclear power for outer Solar System missions, where the Sun is too far away to provide energy without massive arrays or concentrators.

On ISS a nuclear reactor is simply not needed. The Sun is strong enough here, and then there is the question of reentry. Like Skylab and Mir, ISS will eventually be brought back down to Earth.

Not silly at all. A little sarcasm goes a long way to point out just how valuable PV is. In this case, NASA wouldn't rely on a potentially mission-ending component (the energy source) if they didn't think it would be reliable.

I don't think that the viability in space is in question, solar has been in use for a very long time. The problem with solar has been cost of panel production, which is coming down, and direct sunlight. When the project cost tens to hundreds of millions of dollars then the panel cost is negligible. Sunlight is available most of the time outside the atmosphere.
I live in a state where several solar initiatives have been launched and failed because are number four for cloud cover in the US. So even cheap panels don't necessarily solve the problem.
Just a comment on the whole silicon thing, all that sand is just dirtying up the beaches anyway.

Project Orion was designed for earth to orbit launch. If no fallout could be established it would be a good idea. http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29

Sure the sun is strong enough, but you need a 240+ foot solar array. To say ISS doesn't need a nuclear reactor is ignorant. There is not a whole lot of research being done on ISS because of lack of power.

You wouldn't need a 240 foot solar array. Sunlight is MUCH stronger in space than it is on Earth because it isn't being reflected by the atmosphere. Exposure to direct, unfiltered sunlight in space will kill you. You don't need to bring a nuclear reactor to space... there is already one there.

The light is the same, what kills you is the solar wind. Even where ISS is, it is still protected by Earth's magnetosphere. And you do need more than one 240 feet array. Read the blog post. A solar cell only makes electricity from a certain wavelength, it doesn't matter where it is.

I think that missions to low earth orbit have lost an opportunity to promote an environmentalism of sorts. If one can neglect for a moment the huge expenditure of energy to get them up there human habitation of Earths orbit offers a great invitation to explore human could live completely within their means.

I suspect the problem with Biosphere2 was that the challenge to sruvuve would always have been a recreational one, there would have always been a unlocked side door that if thing got to hot one could always step outside. To survive up there no aspect of life can be taken for granted. Continuity of air, water, food, waste and shelter is secured second by second not from Natures abundant offers the supply we on the ground take for granted like children waiting for their pocket money, but solely from their own human cunning.

I long for the day that a space station periodicaly passes over my head not linked to some throbbing mission control but has been forgotten about, radioing down occasionaly to a dusty corner of JPL, asking to be sent up the sports scores.

Solar output is about 1350 watts/meter-squared in Earth orbit. The Earth's atmosphere absorbs some wavelengths more than others, hence the lower output per meter-squared at the Earth's surface.

Solar energy drops off with square of distance. At Mars it is significantly less, which is why some missions requiring more power, use RTGs (radioisotope thermal generators). The Mars Science Lab (2009 launch) will use several kg of Plutonium for power and heat. The Pluto New horizons mission launched in Feb of this year used a few kg of Plutonium for RTGs. Nuclear reactors are very rare in space. The Soviets used quite a few (including one that reentered over Canada in the late 70's).

Space debris and radiation from the Sun cause solar cells to degrade over time. The original solar arrays from the Hubble were returned in the shuttle. They had several hundred micropits from natural (micro-meteoroids) and unnatual debris (small stuff from other rocket launches).

Still, the space industry has been pushing the technology more than anyone else has. They just don't use a lot of it. The housing industry will drive the economies of scale while space drives the advanced technology.

As for needing nuclear power on the ISS. The lack of research on the ISS isn't because of the lack of power (though that does have an impact), it is because of the lack of astronauts/cosmonauts. They spend 2/3 of their time exercising and repairing the ISS. Their just isn't enough support in the government (pick any) to fund a larger crew to get some real science done.

Two reasons that nuclear power would be a bad idea. One, as mentioned previously, it would be politically unacceptable. If there was a catstrophic failure of launch systems, the ISS could not get the periodic orbit boosts it needs to stop re-entering the atmosphere. It primarily uses the Soyuz capsules to boost its orbit. Thus a burning in ISS with a nuclear reactor on board would be bad. Second reason, and more of a hurdle than the first, is weight. Nuclear reactors require a lot of shielding around humans. The weight of such shielding would cripple the ISS launch budget /manifest. It's tough enough getting the ISS completed now, without adding many more launches to bring up a politically unpopular nuclear reactor.

But I digress...

"As for needing nuclear power on the ISS. The lack of research on the ISS isn't because of the lack of power (though that does have an impact), it is because of the lack of astronauts/cosmonauts. They spend 2/3 of their time exercising and repairing the ISS. Their just isn't enough support in the government (pick any) to fund a larger crew to get some real science done." True that is part of the problem, but the main reason I've heard is there isn't enough power to have more people up there. Air and water cleaning take up a lot of energy. Also the ISS requires a lot of shielding as it is from the solar wind. Probably no more would be needed to shield from a reactor. Also a reactor could power an ion engine to maintain orbit.

Traces of Irony found on Treehugger...mind you I think it's gone over some people's heads!!