$6/Kg to orbit
It's a number well within our reach
A poisonous meme has been spreading lately--well, not lately; this has been building now for many years. It's most recently appeared in this New York Times op-ed piece by Lawrence Krauss. Krauss floats the idea of sending astronauts on a one-way trip to Mars, because as we all know, the radiation bath of space is just too toxic to contemplate a two-way trip.
Of course, this "deadly radiation bath" stuff is nonsense.
The meme that has taken over our society's perception of space travel is that it is incredibly hard, and incredibly dangerous. This despite the fact that twelve men walked on the moon, forty years ago, using 1960s technology.
The objections all sound reasonable: too much radiation! Too far away! Zero gravity is too debilitating! Too expensive!
All of these objections are true, while at the same time they're all wildly wrong, and largely for the same reasons. In fact they're all true only if getting from Earth to orbit remains as expensive as it is now.
Consider the seemingly insurmountable problem of radiation that Krauss complains of in his piece. What's the solution to radiation? Shielding. Is shielding a spacecraft impossible, or even difficult? No, actually it's easy. Two meters of water around the crew cabin are enough to solve the problem of radiation in the inner solar system. The problem is not the shielding; it's the cost of shipping the water up to orbit that is the problem.
Ditto for, oh, let's say zero gravity. No astronaut should ever have to put up with zero gravity for more than a day or two at a time; the simple solution to the debilitating effects of freefall is to spin the spacecraft. To do it in a manner comfortable to to the astronauts, you need a long boom arm, which might be heavy and awkward to lift from Earth. The point is, the solution is easy.
Too far away? If a space voyage is going to take months or years, there are two simple solutions: send the ship faster, by using more propellant; or bring along more supplies. Both of these solutions are primarily constrained by the cost of bringing stuff up from Earth.
The list goes on. The fact is, there is only one problem worth speaking about in space development, and that is the problem of cost-to-orbit. It currently costs around $10,000/kg to launch anything at all.
That price will never come down as long as chemical rockets are the only technology we use. Compare the above cost to Alexander Bolonkin's Magnetic Space Launcher, where the price for launching acceleration-hardened non-living objects into space is calculated to be $6/kg. In 2004's NIAC report Modular Laser Launch Architecture: Analysis and Beam Module Design by Jordin T. Kare, thoroughly investigates the cost to launch a human being into orbit using a laser launcher, and comes to a figure of $200/kg. (Both of these systems use electricity and would not themselves pollute at all.)
Even Kare's fancier (and more thoroughly researched) laser launcher provides a cost-to-orbit figure that's 50 times less than current systems. The cost to develop and test his system is also orders of magnitude less than NASA is proposing to spend on the (chemically-driven) Ares launch system.
So where's the radiation problem when you can launch 50 times as much mass into orbit for the same price? Where's the supply problem? Or the velocity problem when you can launch 2000 times as much fuel and hardware using Bolonkin's launcher?
Space is only a costly and dangerous destination if you insist on using 1960s technology to reach it. Once NASA--or more likely the private sector--finally abandons that route, what was impossible will become easy. --I only fear that the meme of space's inaccessibility will prevent us from ever building the launch infrastructure that will prove it wrong; at this point, the meme looks like it's turning into a self-fulfilling prophecy.
After all, when I was ten years old it was obvious that Mars would be humanity's next destination. And that was thirty-seven years ago.
Is still better to get there faster
Mass shielding is still pretty punitive if you have to haul it up from Earth - easy answer: don't.
Tony Zuppero's neofuel website explains just how easy it would be to build spaceships out of ice obtained from the halo of NEOs...
...plus a whole load of other handy in-space materials can be extracted from the NEOs via either a relatively small reactor or solar heat-source. A no-brainer really. To build decent sized space stations/habitats we'll have to go to the NEOs for materials anyway.