Beautifully rendered video of a wheel-shaped space habitat with artificial gravity. This shows viscerally what I pointed out in my Substack posts on the Single-Family Space Colony: that windows are a bad idea in rotating environments. #space#3dmodel
@KarlSchroeder Yeah. My preferred model for a space habitat with spin-gravity: take a gravel-pile asteroid like 101955 Bennu. Inflate a steel balloon inside it (fill with breathable air). Build spinning habitat inside airbag. Add nets and other safety features to taste. Added bonus: the rubble pile outside provides cosmic radiation shielding. Negatives: for farming, you need grow lamps powered by external PV panels—no direct sunlight available.
@cstross@KarlSchroeder If you should wish to inflate Bennu into a shell; you may want to put an outer layer of bag to stop pieces from flying away into space (more so than already happens, anyway).
Complications to this approach include the possibility of creating hot spots inside the containment that cook the mercury & arsenic in the rubble out into vapor that will freeze out onto any cold spots along with less-exciting water & sulfur.
@michael_w_busch@KarlSchroeder You probably want to do that systematically, then—cook the dirtpile to extract wanted/exclude unwanted stuff before you move into Protostellar Love Canal.
@SkipHuffman
Think of the rubble-pile as raw material to place in a 2 meter thick sheath around a cylinder. Leave windows open in the ends for sunlight and to radiate heat.
BUT, it might be overkill. And, again, it's dependent on the cohesion of the economic/collective effort. The concept still nestles safely inside the megaproject vision of space settlement. @60sRefugee@cstross
I think we want the rubble bound together in some way. Loose material is a hazard waiting to happen. Could be mechanically with nets and bags, thermal by partly vitrifying it in place, or chemically with an adhesive or mortar.
@SkipHuffman
The recent paper on this design suggested that. I don't have it right at hand, but it's only a few months old, I believe.I assume you'd do this.
But space colonization makes no sense if you're locked indoors. It's like Covid lockdown, but forever. We do want the experience of living in nature, so we'll have to build that. My argument is that giant colony cylinders is not the best place to start. @60sRefugee@cstross
(Not because a space colony should imitate Tropical Islands but because it gives an idea of what a suitable "outdoors indoor" experience can be like; and it's the sort of thing you could plausibly build on Mars or the Moon once you got past the initial austere colony bootstrapping stage.)
Almost anywhere in space other than low Earth orbit; to limit the radiation dose for humans there for the long-term, you need a continuous thick shell around you - the protons & heavier nuclei come in from all directions. That means no large windows unless they're meters thick.
It also sets a lower limit on the scale required: Several thousand kilograms for every square meter of surface area. And it heavily favors large habitats over small ones.
@michael_w_busch@KarlSchroeder@SkipHuffman@60sRefugee No large windows unless they're behind a periscope arrangement (photons get reflected into the window; high energy cosmic rays run into the walls of the periscope, which can be as thick as necessary).
@michael_w_busch
This assumes that magnetic shielding will never be a thing. Also that lighter substances such as polyethylene are inferior to regolyth. And that other design interventions are impossible. This is a design prompt, not a manifesto.
For instance, even if we need a single big bag for shielding that doesn't mean that a single pressurized vessel is all you can put in it. Why not a hab neighbouhood?
@KarlSchroeder@SkipHuffman@60sRefugee@cstross Magnetic shielding doesn't work for protons on scales less than hundreds of kilometers (the proton gyroradius is too big). Nor does it work to block neutrons or X-rays or gammas.
Similarly; while hydrogen-rich material like plastic works well for soaking up protons and neutrons, you still need meters of shielding. And blocking gammas requires some higher-atomic-number atoms.
All this doesn't say anything about what gets built inside the shell.
@michael_w_busch@KarlSchroeder@SkipHuffman@60sRefugee Wrong radiation spectrum, surely? Naked neutrons have a half-life on the order of 14 minutes; gammas that are too high-energy decay via electron/positron pair production so probably not a factor in deep space. AIUI the real radiation hazard outside the Van Allen belts—beside CMEs—is from high energy cosmic rays, in the > 5 GeV range. Do-able with magnetic shielding, but you're asking for gigavolts.
But ion collisions in the solar photosphere put out >100 MeV neutrons that last long enough for many survive to ~1 au distance. They're some percent of the unshielded radiation dose.
The gamma ray spectrum follows a power-law plus hundreds-of-keV emission bands from positrons hitting electrons & neutron decays.
There are also lower-energy secondary neutrons & gammas produced inside whatever shielding is used.
@michael_w_busch@KarlSchroeder Good point. But (L5 proposals aside) don't most space colony proposals focus on the asteroid belt and further out? By which time you're getting multiple decay half-lives out from the sun.
Add comment