[okami]

Anything's realistic, given time and resources. Since we've never had a good space program, however, jumping the gun by going to Mars is out of the question for a couple decades at the minimum. I seriously doubt I'll see it in my own time.

It would take a permanent base or four on the moon (especially on the far side) and orbiting industries, let alone nuclear or ionic propulsion, to get the job done. Reliable methods of eliminating microgravitic effects on the body (loss of calcium, redistribution of mass, muscular deterioration etc) would have to be countered by reliable methods of imitating earth-normal grivitational effects.

By far the greatest hazards would be the length of the journey and the danger from stellar instabilities. Disruptive solar flares from our own sun could sterilize of kill voyagers with inadequate shielding, as well as frying out any equipment or changing the vessel's trajectory. Such phenomena can't always be predicted, either.

The same is possible where nearby stars are concerned, since one never knows for sure when a supernova may appear: basically, when the light gets here, it's too late. The last visible in this galaxy was in the late 16th century or so. Supernova 1987A, which was observed in the southern hemisphere, was in one of the two Magellanic Clouds, smaller galaxies orbiting our own. Obscuring dust and gases keep us from seeing most of the supernovae in our own galaxy; for all i know, the dust and gases protect us from the adverse effects of these stars.

If one posits extrasolar phenomena as being of low probability, it still leaves open the question of our own sun. For this reason it would be better to go in steps, I believe, using near-earth asteroids which cross the orbits of both the earth and Mars. Besides getting much-needed training and experience, one could use such asteroids as bases, with two self-evident advantages.

(1) The mass of an asteroid can be used as a shield against the sun. Place a few comsats in orbit if it's massive enough, stay on the far side, and any harmful solar particles or radiation won't get through. . .provided, of course, its rotation can be stabilized. Better yet, it can be hollowed out, so that inhabitants and virtually all equipment are completely safe. Contact with Earth can be maintained through the comsats in orbit; if they're burned out, it'll be cheap to send up some more from the asteroid base.

(2) Use the asteroid in question as a launching platform. On its closest approach to Mars, launch manned probes, etc. to the Martian surface. The need for fuel and similar consumables would be drastically shortened, since the asteroid's mass and orbital characteristics do most of the work.

Insofar as building materials go, it's terribly expensive to put things into space because we have to fight gravity each step of the way. This consumes all kinds of power and materials in itself. Space programs must be aggressively pursued, whether American or not. Get Spaceguard up and running, so that the rest of the near-earth asteroids can be plotted. Some craft can go to them for building materials; one good hunk of nickel-iron supplemented by lunar materials could do for construction of the spacecraft(s), if it isn't hollowed out to become the spacecraft itself. Robotic probes can rendezvous with comets on this side of Jupiter & pick up the hydrogen & oxygen (as well as other gases) frozen in the ices of the nucleus, so that the crews would have water, breathable air and propellents.

Ionic propulsion, tested in the Deep Space probe a while back, is far more reliable than the chemical boosters we have, but it takes time to get to speed. When Cassini was sent to Mars, lotsa people got bent out of shape because it carried a nuclear reactor for power: Solar radiation's virtually nonexistent around the gas giants, so that power via solar cells was out of the question.

While I applaud the dangers of nuclear weapons, etc, people forget that there's a BIG fusion reactor in our faces every day, about 800,000 miles across. While accidents are always possiible, the nuclear reactors we've sent into space have (as far as I know) performed nearly flawlessly to date.

I believe, then, that a Mars mission would be drastically safer and cheaper--albeit taking much longer--by taking our time and using the near-earth asteroids, rather than taking one very big step straight to Mars.

If it wasn't for the political ballyhoo, such a program could have been started decades ago.