You can’t protect them from galactic radiation using shielding, but as we learn more about renal biology it may be possible to develop technological or pharmaceutical measures to facilitate extended space travel.

Is there a physical reason why shielding is ineffective? Seems like some tanks of water (which a Mars mission would need anyway) or some slabs of lead or tungsten would do the trick.

[–] Illuminostro 6 points 2 weeks ago (1 children)

The weight, and all the extra fuel it would take to get it into orbit, which would require larger rockets, which drives up cost...

Until we can start mining asteroids, it's probably a no go.

[–] [email protected] 1 points 2 weeks ago* (last edited 2 weeks ago)

Those sound more like financial and engineering challenges than physics. If we build something like an Aldrin cycler, all that mass needs to be launched only once. Larger and cheaper rockets are currently in development, with multiple organizations currently working on fully or partially reusable launch vehicles.

I'm not convinced that asteroid mining is a necessary prerequisite for a well-shielded Mars mission, though it would definitely be more efficient in the future.

[–] CarbonatedPastaSauce 4 points 2 weeks ago (1 children)

It would take a LOT of mass, even just using water. You need a 1m thick layer of water to provide adequate protection in space outside of LEO. There's a good explanation here:

https://space.stackexchange.com/questions/1336/what-thickness-depth-of-water-would-be-required-to-provide-radiation-shielding-i

TL;DR - You'd need 3 Saturn V launches of just water to fill the shielding for a tiny capsule going to Mars. The example they used was "a cylinder roughly 3.5m by 20m" for the crew compartment.

If they could somehow pull the water from space (comets, asteroids) then it would become easier, but launching that much water from the surface of Earth is just not logistically feasible with our technology.

[–] [email protected] 1 points 2 weeks ago

The volume of shielding water needed is the difference between those two cylinders, or 22⋅π⋅2.752−20⋅π⋅1.752≈522.68−192.42=330.26m3. As one cubic meter of water weighs 1 metric ton (1,000kg), that's 330,260kg to get into space

Honestly, 330 tonnes doesn't seem too unacheivable to me. That's less than the mass of the ISS, which was built using much smaller rockets than are currently in development.