Thorium nuclear fission material solves the fission problem(nuclear fusion is
right around the corner). India is about to get a thorium nuclear fission
reactor going(within the year or so).
That being said, I certainly don't
like the idea of confining all of humanity on earth forever. It seems to me that
people's thinking are culturaly conditioned; it's a bit like the way most people
learn language as they grow up; do they really know the technicalities of their
language they use every day? Most never do. For those people, learning a new
language is often a hard frustrating experience. It's similar to learning how to
think! People think when their cultures tell them to. Space expansion(like the
great expansion of humanity from Europe to the Americas) expands and frees the
mind; or, at least, I hope that's the case.
One underrated power of democracy is that it frees people from having to think in social conditioned ways, even if they get voted out. It's not so much the voting of people in and out(that can serve a good function; but, it's often a lot of back and forth pluses and minuses). Well, perhaps the American's system of checks and balances is what really makes it work. Americans complain about the system getting bogged down; but, really, that's what's its for; to make sure nobody has absolute power.
I point out the democracy thing here because some people want to think that Democracy is about solving problems(even physics problems! See Timothy Ferris's "The Science of Liberty"). As already stated, the democratic solution is always a back and forth minuses and pluses of voting in and out different viewpoints. What's really made democracy special is as an indirect way of freeing people's minds.