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Comment by WizardAustralis | Hacker News Reader

The issues of space radiation is far from discredited. It is one.of the major issues that still doesn't have an elegant solution. One.idea that SpaceX is proposing is to try and get the trip to Mars to 6 months. It will still be a serious issue but it would at least be better than the typical trip proposal.

One of the reasons I posted that channel was because they seem to have really done their research far beyond the typical "it wont work, just because". It is biased still but at least they arent just firing blind.

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It does have a pretty elegant solution: water. Water is an excellent shield against radiation, and any long duration mission will have a large amount of water on board for the humans. With proper positioning of the tanks, said water can do double duty as a radiation shield.

Water does work, it is also astoundingly heavy. That is the major issue. Elegant but impractical.

It simply blows out any useful payload volume and costings because of the amount of water required. Last estimate I have seen is they would need 1,500 tons of water to make Starship radiation resistant (80% decrease in exposure). Even at $300 per Kg, about 1/8th the cost of current launches, that is still approaching a half billion dollars per ship with a significant lost of internal space.

Technical viability and economic viability are two very different things as well. This is going to be the thing that I feel will eventually limit our travel outside of the earth system.

I suspect we will see rampant use of Starship in orbit, the occasional run to the moon and maybe once or twice to Mars but beyond that. It will be just another technological lead that ends up in civilizations recycling bin.

One possibility is the use of a cycler - in other words, putting only a couple Starships with massive amounts of water onboard in an orbit that loops back and forth between the Earth and Mars. Passengers would board it for the transit, then transfer back into an unshielded starship that flies in formation for the journey. This way, the shielding mass only needs to be launched once, and can be reused for an arbitrary number of flights.

That is a pretty smart idea actually.

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