> it has to do with knowledge. And that can never be replaced by private companies.

Many voyages of discovery were financed by private companies. For example, the Terra Nova Expedition was half financed privately.

http://en.wikipedia.org/wiki/Terra_Nova_Expedition#Finance

and:

http://en.wikipedia.org/wiki/Discovery_Expedition#Finance

> NASA's space program has nothing to do with profit, it has to do with knowledge. And that can never be replaced by private companies.

Why not?

Because long term research requires immense levels of upfront spending with no requirement to turn a profit.

IBM, Bell and Xerox are pretty well known for their research efforts.

Because NASA's mission is not to turn a profit.

Yes, but that doesn't say anything about companies.

The FAA doesn't fly airplanes, either. NASA's role will change once commercial manned space access is part of the environment.

NASA's role isn't flying billionaires around planets for profit. That can happen through private companies just like its happening with planes now. Knowledge and exploration is NASA's game. No private company cares for those, so funding will come by the state. Its more effective then to fund NASA, than some private company that stands to make profit by doing it.

The error in your logic is the casual assumption that knowledge can not be profitable. Hopefully the mere act of stating it is enough to show how untrue that is? And that's why there were private discovery expeditions, per WalterBright's point.