Well there are some very good points being made here about the practical aspects of space travel. In particular, thank you Jon for your insightful comments in separating speculation from fact regarding things like the motivations of the space policy developers or the damaging effects of micro-gravity.
Allow me to share some perspectives and experiences regarding “vision” and “risk” as someone who has been in the space business for 25+ years. I enjoy science fiction too but as an engineer I am also amazed at how much basic ground work still hasn't been done to establish the backbone of everything that is taken for granted in sci-fi stories. As I noted earlier, the International Space Station has only been operating a closed loop urine recycling system for six months and its full crew of six has only been there about 3 months.
The Jet Propulsion Lab just finished flying an Electronic Nose, a real-time chemical sensor/analyzer, on board the ISS for six months. Surely such basic technology would be needed on a long Mars mission, at the very least for safety. The chief scientist for this 5-person project has been repeatedly approached by people in the business community (e.g., airport security teams, food inspection firms, etc) to build one of these for their needs but the technology is still in its infancy because you have to do the tedious lab work to optimize your detectors for the things you expect to encounter.
Just this week the first inflatable heat shield was tested by NASA. Several years ago JPL had a very aggressive Mars robotic program in which by now all our orbiters would be arriving at Mars via aero-CAPTURE (i.e., plunge straight into the atmosphere for braking down to orbital speed, rather than using retro-rockets). This was abandoned when we lost two Mars missions in 1999 due to poor technical oversight caused by the "faster, better, cheaper" philosophy. Aerocapture looks great on paper, but who wants to be the first mission to volunteer... anyone stepping forward?
At NASA we are constantly admonished to do the hard things, the sometimes unglamorous but very risky work. We don't build orbiter spacecraft in-house anymore because contractors like Lockheed-Martin can do that just fine. As much as I would like to fly on Virgin Galactic's 5 minutes of weightlessness trip, Bert Rutan has stated that his goal for SpacecShip Two is to be less risky that the first airliners were in their early days.
I am fascinated by the progress of Space X and their Falcon 1 (and soon Falcon 9) rockets lofting satellites at a fraction of the current cost. When the founder Elon Musk came to speak at JPL several years ago, the auditorium was packed and since then some JPLers have gone to work there in mid-career for the excitement and challenge. Fortunately, Elon Musk earned several hundred million dollars co-founding PayPal and some early computer games, so he can finance the company and new employees don't have to take a pay cut (but they get stock options!). There are definitely some risks having a company built around one person. Some of you may recall when AMROC’s founder died in a car crash a few days before their big launch (which burned up on the pad) and the company soon folded. It now appears Sea Launch is going to fail after they had a spectacular launch pad failure a few years ago. Robert Bigelow (Bigelow Aerospace - Las Vegas) has now placed two small-scale inflatable habitats in orbit and is offering $50 million to anyone who can build a vessel to carry people to his space hotel for a stay of up to 6 months. He has stated, however, that there is a drop dead date to that offer and the whole space hotel venture because, after all, he is a businessman (he created the Budget Suites hotel chain). Finally, a Russian company is talking about launching a long-duration version of a Soyuz spacecraft for a gliding orbit around the Moon and back for space tourists.
In the end, where does government funding of space fit into the picture? I would suggest that one of NASA’s biggest roles is to try innovation, “retire the risk”, and move things into the commercial arena. For example, I work on an Earth-orbiting experiment called the Atmospheric Infrared Sounder which has been mapping out the thermal and chemical content of Earth’s atmosphere since May 2002. In general, NASA builds up new technology for weather and meteorological research then hands them over in the next generation satellites to the National Oceanic and Atmospheric Administration (NOAA), who gives us the hurricane weather reports. Some NASA and NOAA project make extensive use of contractors but to date, other than the French SPOT venture, I haven’t seen too many private companies stepping forward to launch their own weather satellites and take on the grunt work of weather reporting. Evidently, at least from a financial perspective, the “risk” hasn’t yet been retired. Similarly, the Space Shuttle is being retired precisely because there are such insurmountable risks in its design that it can never be “routine”. Sometimes it’s better to start over with many lessons learned in your pocket.
We will get to Mars eventually, but should NASA pave the way if no one (i.e., private enterprise) will be there to carry the ball after the first touchdown?