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?