"Oh, you are asking me about an actual problem with my unrealistic plans to colonize Mars? I have no idea, but I must say we plan to colonize Mars soon in order to get money from the stupid investors, lmao"
https://twitter.com/marinakoren/status/1461114697713954820
I've read some sci-fi stories where they use a thick layer of water to attenuate solar radiation. But I don't think it's anywhere near a solved problem. Musk is a twit.
What was the one where the whole crew had to hide from a radiation storm behind the water tanks?
No but that sounds like it's in the same vein.
Its solved in so far as adding a large mass to the exterior of the ship can dramatically reduce the hazards of deep space travel. But its still a problem in the sense that getting large amounts of material into space is horribly expensive and difficult.
There was some proposal by the Chinese to build a kilometer long spacecraft, for instance. And if you're willing to invest that much material into a spacecraft, that opens up your options quite a bit.
Woof. A km long? I guess they have cargo ships almost that big that endure far greater pressures and stresses than a spaceship would, but holy shit that's ambitious.