[siffland]

Serious question, since this is out of my swim lane. The Author keeps talking about the effects of Galactic Cosmic Rays, do we have any usable materials we can build habitats out of that can block them? I mean usable in the sense we can produce in scale and they are non toxic to humans.

[Balgair]

For Cosmic Rays the only thing is just a lot of atomic nuclei. You need pure mass. This is why a transit to Mars or Saturn is going to be hard for us to pull off in the near term. All those nuclei are expensive to get into orbit right now.

Outside of that, there is a 'graded Z' shield. Here, you make a layer cake of various atomic nuclei (the Zs), going from heavier to lighter. Typically Tantalum down to Tin and down to Aluminum. They physics here aren't super important, but for lower energy radiation, you can get down to a 60% mass reduction for similar shielding protection.

The problem is that it's the higher energy radiation that you are worried about, the Cosmic Rays. Graded Z shields pretty much work like anything else at those energies. Under our current physics mumbo-jumbo, you just need nuclei.

[Miraste]

Artificial magnetic fields are another possible solution.

[Balgair]

Yeah, for the less energetic stuff. The same issue applies, the very energetic stuff just sails right on in. Big EM fields also don't deflect neutrally charged stuff like Cosmic Rays and neutrons. Radiation shielding is hard stuff and it'll take multiple methods working in tandem.

[ryanmercer]

Any material will work if thick enough. Thick concrete, water/ice. It just has to be thick enough to also handle the secondary radiation from higher energy stuff. We're talking a need for several feet of concrete or several inches of lead.

For a rocky body like Mars the 'easiest' solution is simply excavate trenches to put your habitats in and then piling several meters of regolith over the top, or using lava tubes/caves. If excavating was too difficult you could similarly just make bricks of compressed/fused regolith and pile them up. Titan has a rocky core but is mostly ice where a manned mission would be, there you'd probably just carve out large blocks of ice and place them around your habitat.

The best universal solution would probably be some sort of sandwich of materials that was still decently thick.

[TheGallopedHigh]

One of the simplest methods would be to bury habitats in conjunction with materials to block cosmic rays.