But building a large-scale orbital infrastructure and ignoring the Moon is probably not the right way to go.

If the goal is the ability to build large space objects, then why not address the problem directly? The major problem in space exploration as I see it is the cost of reaching the orbit. Why not work on that directly instead of going to the Moon? Cheap space vehicle or Clark’s space elevator IMHO would be a LOT more useful than a Moon base. And would probably have similar costs.

But why the Moon? Once we’re there, launching materials from the Moon for large-scale space construction takes far less energy than launching from Earth, and there’s no atmosphere so you can launch at orbital speed from the surface if you want. It’ll mean establishing mining and manufacturing facilities there, etc. Yes, that’s not going to happen tomorrow – but the sooner we get back on the surface, the sooner the rest of this can happen.

You don’t have to go back to the Moon to get space solar power of course. But building a large-scale orbital infrastructure and ignoring the Moon is probably not the right way to go.

1 – Fission is too expensive.

I’ll double check, but as far as I know, fission is the second cheapest to hydro.

we have a WMD problem in the world

You have WMD problem? I see JWB has this same problem too. Must be contageous :-). But seriously. So far it has not been confirmed. Not even close. Could it be the same problem as the man-made global warming?

2 – Fusion, unfortunately, is still in a “which reactor design will work” mode

OK, ok, so it does not exist yet. Where can I see the space-based solar power plant?

Why go to space for solar power?

That’s not my question. I have not seen anyone asking this particular question. Why are you answering it? My question was why do you need to go to the Moon or Mars for solar power? Let’s make it simple. What’s the point in going to the Moon?

*1 – Fission is too expensive. The French don’t have many other options, and heavily subsidize it. All US reactors were subsidized too – they stopped building them 25 years ago because of the expense (you could blame the expense on the environemntal review process, but still, it’s there). Also, supplying non-fossil energy needs this century with fission would require multiplying the number of reactors worldwide by about a factor of 10, and (unless we found new ways to mine uranium from very low grade ores or seawater) would require breeder reactors and fuel reprocessing as well. Think we have a WMD problem in the world right now? What would it be like with 100’s of times more plutonium being extracted from spent fuel?

*2 – Fusion, unfortunately, is still in a “which reactor design will work” mode, and these are pretty major questions. The tokomak design, on which the multi-billion dollar ITER project is based, has magnetic coils on the inside of the plasma; these will be destroyed by radiation in too short a period of time to be useful for a commercial reactor; in fact the ITER project isn’t even planning to use real fuel (deuterium-tritium, rather than deuterium-deuterium) until almost the end of the project, to avoid this problem. There are proposed solutions with “liquid walls” and spherical designs, and then there are the various intertial designs. Replicating the sun on the Earth is going to be exceedingly difficult and expensive, at least for the next 50 years or so.

Why go to space for solar power? Sunlight 24×365. On Earth in the average location you get the equivalent of full sun just 2-3 hours/day. Even the best locations get only about 5-6 hours/day worth. Currently the cost of solar photovoltaics is prohibitive, but in space you wouldn’t need nearly as much of them. Of course the cost of launch is too high too, but at least people are hoping there are solutions to that problem.