Interplanetary travel far from us
In the last March 2006 issue of Scientific American appeared published a devastating article on cosmic rays and their implications for interplanetary space travel. Here over the earth surface we are shielded from extremely energetic particles. Our thick atmosfere and the Van Allen belts protect us from the damaging effects of fast charged particles that cross the vacuum that lies among the planets.
Any spaceship aimed to bring humans to other planets requires some sort of shielding to protect the astronauts. The problem is that all the current shield proposals seem to be unfeasible. A simple shield of matter would be too heavy for current propulsion systems, a magnetic shield would be dangerous for the passengers, and an electrostatic shield would be energetically prohibitive and ludicrous, at would attract and accelerate surrounding negative particles, giving rise to an equally dangerous bombardment, although of the opposite polarity to cosmic rays.
The author put some hope in the idea of using a still to be developed anti-radiation pill. I may know almost nothing about Physics, but I do know some Biology. Take my word that that pill is at least decades ahead of us, if it is to be attained at all.
To me, this means that human space travel will be impractical for us until we find a better propulsion system. I don't feel any regret for dropping the idea of going to Mars. I regard Mars as no more than a clump of rusty rocks deep down in a profound gravity well. However, there are many interesting places in the solar system. If we can't travel through the space we won't be able to live in it and exploit its resources.
There are some alternative ideas that may work, as the Marshall Brain's discard your body concept. That idea may do, and it will be possible to implement it sooner than the anti-radiation pill. In any case, this option is decades far from us too, and for now I find it a bit disgusting.
I will stick to my body for as long as I can.