Astronauts on future long-duration missions will be exposed to different kinds of ionizing radiations, Earth's plasmashpere and Van Allens radiation belts, solar flares and galactic cosmic rays. What are the cutting edge materials & strategies which could be applied for radiation shielding?

Is there some universal material which could be used for all types of radiations or there should be a layered protection, each layer dedicated to specific type of radiation?

Also what would be the minimal thickness of such protection which can confidently guarantee (NASA 95% confidence level) that astronauts will receive less than 50mVs during the flight to Mars?

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    $\begingroup$ The physics of radiation shielding is pretty mundane; you've got kilograms of electrons and nuclei. There's no nanoparticle or metamaterial technology that's going to be better than the usual suspects (water, titanium, tantalum, etc.) there may be strategies involving how to position them between the incoming direction and the astronauts, and how to detect the timing and severity of solar ejecta etc. $\endgroup$ – uhoh Mar 9 '20 at 0:01
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    $\begingroup$ @uhoh - acknowledged. $\endgroup$ – WOW 6EQUJ5 Mar 9 '20 at 0:04
  • $\begingroup$ @uhoh - Be careful. It depends on from what energies you wish to shield the cargo. Some things with lots of hydrogen per molecule are great at certain energies but are useless at others. Lead is great at shielding on Earth, but sucks in space because it's too expensive to launch appreciable amounts (and it tends to have a finite amount of radioactivity as well). Titanium, Tantalum, etc. are good as well but also not cheap. $\endgroup$ – honeste_vivere Feb 24 at 16:28
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    $\begingroup$ @honeste_vivere I'm confident that as written my comment is correct. $\endgroup$ – uhoh Feb 24 at 21:08
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    $\begingroup$ @honeste_vivere after 3,000 questions and ~30,000 comments network-wide I've learned to choose my wording very carefully (most of the time at least) $\endgroup$ – uhoh Feb 24 at 21:36

Most shielding is just mass plus atomic number - for cosmic Ray shielding you want light elements, as heavy elements make more radiation. Water and polyethylene are good options.

The main interesting thing is how to make the shielding do double duty.

Options include:

  • supplies
  • thermal protection systems
  • fuel/propellant
  • water supplies
  • boxes of food
  • sewage (can gradually replace food)
  • speculatively, algae tanks for closed life support
  • the rest of the habitat/spacecraft -auxiliary vehicles
  • on planetary surfaces, sandbags of regolith

There are some ideas about magnetic shielding but they require insanely strong magnetic fields... That the astronauts and equipment would be exposed to. Plus the equipment to generate magnetic fields also has weight. So this isn't usually considered a very practical near-future option.

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    $\begingroup$ There are some wild schemes for a strong magnetic field generator to deflect at least all particles with charge. $\endgroup$ – Carl Witthoft Mar 9 '20 at 14:21
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    $\begingroup$ @CarlWitthoft Is NASA doing research on “mini-magnetospheres” to protect crew from radiation in space? and also touched on in this answer. $\endgroup$ – uhoh Mar 10 '20 at 3:27
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    $\begingroup$ @CarlWitthoft - I answered something along these lines at physics.stackexchange.com/a/214858/59023 but note that to shield ALL particles, the fields would need to be enormous, like way more than MRI enormous. If by all you mean anything below ~1 GeV, then you are looking at fields in excess of 1-10 T. Ceramic magnets can certainly generate such fields but that's a lot of mass to cover a spacecraft and also poses potential issues with some electronics. $\endgroup$ – honeste_vivere Feb 24 at 16:34

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