The Smallest Minority on earth is the individual. Those who deny individual rights cannot claim to be defenders of minorities. - Ayn Rand
Not sure I agree that freedom/capitalism is necessary in order to go to space; it wasn't necessary for the exploration of the undeveloped world by Europe.
If there is a need to reach space, and a benefit to doing so that overrides the cost, then a free capitalist society is the best way to ensure that such travel happens as soon as possible, by efficiently allocating resources where they are needed. But if you have a strong central government with either direct control or regulatory oversight of industry (Soviet Union, Nazi Germany, the United State of America after WWII), then all it needs to do is steal resources from the productive and funnel it into space travel (or R&D, if tech level isn't there yet).
Just watch how much money is redistributed to global warming special interests in the next decade...
I'd add as an additional thought:
A free society is only stable if there is an intact right of exit. Once all of the frontier a particular civilization has access too has been exhausted, they will begin a long slow decline in liberty.
I don't read him as saying capitalism is necessary per se so much as that the diversity of approach to solving the problems as well as the acceptance of individual risk aren't factors much allowed by a more centrally planned economic model.
Within the context Frank provides above, "the undeveloped world" was immensely more free, both in action as well as economically, then was Europe of the 15th or 16th century. It's all a matter of context and relative condition, not some absolute measure.
And wouldn't the universe pretty much be the definition of "frontier"? Whether or how, using who's model, seems to be the question under discussion, I think.
Thanks for the link Kevin. Interesting stuff.