From: henry@spsystems.net
In article ,
Josh Gigantino wrote:
>> 20cm or so of water is a good storm shelter for interplanetary space or
>> high orbit. (There's no point in having it in LEO...
>
>20cm is enough for shelter from solar storms?
Probably, yes -- it depends a little bit on what assumptions you make and
how conservative you are.
>...For cosmic rays (from your previous
>posts on subject), they basically scatter into highly ionized pieces
>that do more damage in tissue. Is there a way to shield against them?
>Something like M2P2 or that rad-plastic in the space news lately?
Nothing that will stop them reliably in a short distance, I fear. The
energies are still pretty high and they're fairly penetrating.
>For LEO, would you recommend a foam-only TransHab? What about the HEEO
>orbit I mention, and flights to Mars/asteroids?
For LEO, it depends a little on which LEO you're in, but by and large you
don't need a lot of shielding. For an orbit passing through the belts
with any regularity, you'd need a bunch, but I don't have numbers on hand.
Out in deep space, you want either complete shielding (5-10t/m^2,
impossibly heavy for near-future vehicles) or else a small shielded storm
shelter and relatively little shielding on the rest.
>> Uh, there's no reason why the outer layer would be frozen. In fact, it
>> would probably be difficult to arrange for it to stay frozen. Manned
>> modules generate a lot of heat...
>
>What kind of processes could utilize this heat?
There isn't really anything terribly practical, because it's at quite low
temperatures, which makes exploiting it fundamentally difficult. About
all you can do is get rid of it, and even that's a nuisance, since you
need quite a bit of radiator area. (That's what the inside surfaces of
the shuttle cargo-bay doors are, for example.)
>...Waste heat and available water could be used for humidity control.
Humidity control in a manned spacecraft with a recirculating air system
generally means dehumidification, not humidification. Human bodies put
out substantial amounts of water vapor.
>Would the water (plus several layers of kevlar, bladders, etc) provide
>enough meteorite/impact protection?
The way to protect against micrometeorites (and in LEO, space debris) is
with multiple thin "bumper" shields spaced well out from the main hull.
It's helpful to add low-density material, e.g. thermal insulation, in the
gaps... but the #1 way to improve the protection is to make the gaps
*wider*. An incoming object hits the first shield and turns into an
expanding cloud of plasma and fragments, and the more time that cloud has
to expand before it reaches the next layer, the less chance that enough of
it will hit in one place to penetrate. Wider gaps are more effective than
more mass, and multiple thin walls are more effective than one thick wall.
>...People are always saying that the Van Allen belts are
>life-threatening, it seems like a good way to provide protection.
>Would the 20cm (or 50?) around equipment and personnel be enough? (I
>know you don't have numbers handy, just ballpark)
Gut feeling, 20cm isn't enough but 50cm might be.
>Would it be correct that a HEEO application might be the only
>reasonable use of this type of inflatable? Would it actually be more
>dangerous than a foam-filled inflatable (cosmic ray damage) on a Mars
>mission?
Right, you *don't* want to live inside 20cm of shielding in deep space,
because the cosmic-ray-secondary dose inside that sort of shield is
rather higher than the cosmic-ray-primary dose outside it. Only when
a giant solar flare temporarily changes the outside environment for the
worse do you retreat inside, and that fortunately is rare.
--
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-- George Herbert | henry@spsystems.net
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