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by MeImCounting 744 days ago
The problem is that paradoxically, thicker shields can cause higher doses of radiation due to secondary radiation production. Theres a balance there to minimizing primary and secondary dosage but you cant really get it below a certain threshold without some form of active shielding. Theres a lot of promising ideas for active shielding but they all require alot of power. All this to say that someone on a trip to mars will indeed get a high dose and this is something that needs to be given thought. Its not an intractable problem but it is also not even close to being solved or trivial.

Folks on Mars is still quite a ways away. Not impossible or pointless by any means but it will require significant advancements in many domains before we can really do it safely.
2 comments
somenameforme 744 days ago
The secondary radiation you're talking about is called bremsstrahlung (braking) radiation [1]. This is precisely why water is, to my knowledge, the current leading idea. It works not only as an excellent primary shield but also helps to minimize secondary radiation, and you also naturally have literally tons of it.

As an aside, this is why the original Moon missions used simple aluminum. One of the typical angles people who don't think we landed on the Moon used is that to safely get through the Van Allen Belts we would have needed massive lead shielding on the craft, when in reality it was shielded by a pretty thin layer of aluminum, precisely to minimize secondary radiation. If you put that thick lead shielding on the craft that people intuitively think you'd need, it very well could have killed the astronauts.

[1] - https://en.wikipedia.org/wiki/Bremsstrahlung

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MeImCounting 744 days ago
Polyethylene is similarly a good shield because its got high hydrogen content so is pretty good at moderating neutrons. I image a polyethylene structure containing a layer of water is probably something like what we'll end up settling on. Its also quite strong and would make decent structural components.
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timschmidt 744 days ago
https://en.wikipedia.org/wiki/Radiotrophic_fungus have also been discussed as an option.
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