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Cosmic Rays Could Kill Astronauts Visiting Mars
jvchamary writes "Given the recent stream of reports of 10th planets and the relative success of the NASA Discovery mission, it might again be time to get excited at the prospect of visiting the Red Planet. Unfortunately, New Scientist reports that Astronauts traveling to Mars would be exposed to so much cosmic radiation that 10% would die of cancer."
We've known this for quite a while.
I think they'd also have to go through the Van Allen radiation belts which could also be a concern. Conspiracy theorists have argued that space travel to the moon was impossible because the Van Allen radiation would kill or incapacitate an astronaut who made the trip. In practice, even at the peak of the belts, one could live for several months without receiving a lethal dose.
Apollo had timed things however to make it accross while radiation was at a minimum. However, if they'd be on such a long trip -- timing will have to be a lot more precise.
Short of hauling up lead plates, I don't know what they'll do.
If they're talking about current chemical propulsion technologies, then yes, they'll be out there for the better part of a year. If we get dig out nuclear propulsion technology that's already been developed, such as NERVA, and other things such as gas core nuclear rockets, it's simple to cut the trip down to weeks while simultaneously packing dozens of tons of extra shielding.
The situation is a lot more complicated than that. High atomic mass elements are great at causing collisions with the particles composing the radiation that you're trying to shield against. However, a direct collision isn't always the best thing.
Case and point: The best way to shield against solar radiation is high atomic mass materials. Even moderate materials, such as aluminum, should work quite well if you plate it on thick enough.
But what happens when GCR (Galactic Cosmic Radiation) strikes that shielding? You often get bremsstrahlung ("braking radiation") - the single particle is instead replaced with a shower of much more dangerous particles. Even worse, these particles are released partway or even all the way through the shielding.
The best way to shield against GCR is hydrogen in huge quantities to decelerate the particles - this generally means either your fuel or plastics in the skin. But that doesn't shield well against solar radiation. In short, what you end up needing is a complex layered system. The exact design? That's still a wide-open question. We know we can pack enough aluminium to stop solar-radiation-only (including a small shelter for storms) without having too heavy shielding requirements. Factor in bremsstrahlung, however, and it's a wide-open question.
By the way, to those who suggest "active shielding" (creating a magnetic field around the craft to deflect radiation) - studies show that it won't work to stop GCR (only solar).
"It felt almost as good as stealing cars from grandma." -- Margaret Thatcher, probably.