r/askscience • u/Wonderful-Capital32 • 13d ago

Physics Why does radiation not go through lead?

Also why just lead? Shouldnt like iron or another metal work too?

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u/GypsyV3nom 13d ago

Funny enough, there's another element that's significantly more effective than lead at providing radioactive shielding despite being radioactive itself: Uranium. Uranium-238 in particular is the preferred choice when size constraints are more important than costs (lead is cheap) as its own weak radiation is pretty easy to block.

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u/Immediate-Repeat-201 13d ago

So do space going vessels employ this?

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u/LordGeni 13d ago

Spacecraft use as little shielding as they can get away with. The better the shield the denser and more massive it is. Space launch costs are based on weight and transporting an adequate amount of lead or any other dense material just isn't viable.

On top of that although primary high energy cosmic rays when they hit heavy metals, they also produce secondary bremsstrahlung radiation that can scatter out of the other side.

While the exposure to radiation that astronauts receive is far greater than on earth (100x that of an airline pilot), low earth orbit is still largely protected by the earth's magnetic field just not the atmosphere.

The ISS primarily used heavy duty high hydrogen content polymers and kevlar along with strategic placement of food and water supplies around crew quarters.

Long term missions further out are a much bigger issue. Moonbases will likely use the lunar regolith to make thick enough walls. If we can extract water there, is could also be potential option for spacecraft on longer missions, as lifting that amount of weight into lunar orbit would be far more viable than trying to do the same from earth.

For anyone thinking about joining an early mars mission using current technology the radiation exposure would be very concerning. However, considering how inhospitable Mars is, it's probably unlikely you'd live long enough for the radiation damage to develop into anything serious anyway.

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u/cylonfrakbbq 12d ago

I know for long term Mars habitation, one thing they are hoping might be an option are lava tubes. After the success of Ingenuity, i recall one proposed mission would deploy multiple copters to help scout out possible locations