Re: Reasonable Minimal Size for a 2-Man Capsule?

In article <1165218817.283949.304370@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Oren <oren@xxxxxxxxxxx> wrote:
that's a conservative number because aluminum is not actually the best
shielding; something with a lot of hydrogen in it will be better.

Water has a lot of hydrogen but unlike polyethylene it can be moved
around easily. If you store a layer of water in the walls and then use
it for evaporative cooling during reentry you can theoretically use the
same mass for both radiation shielding and heat shielding. Is there a
potential net mass gain here?

It's mildly interesting even for those modest shielding masses, and much
more so if the shielding requirement is raised to handle giant flares
(which Apollo just took its chances with).

However, water cooling for reentry is poorly explored and a cautious
capsule designer might think it overly risky. (Another area where NASA
could do spaceflight a lot of good with an X-rocket series, sigh.)

The lunar lander also needs significant radiation shielding and all
that mass is carried down into the moon's gravity well and up again...

Whether the lander needs significant shielding is not clear. Apollo did
*not* shield its lander; the procedure for a major flare was for the guys
on the surface to head back to the CSM pronto, as soon as the radiation
gauges started to rise. If you can do that at any time, and you think
you'll have enough time for it(*), you may not want to shield the lander.

(* The joker in the deck is the 20 Jan 2005 flare, which was the most
intense in spaceflight history *and* hit like an avalanche, with none of
the long slow rise seen in other giant flares. That caused a lot of
rethinking of radiation-protection ideas. )

An alternative is to adopt the philosophy that the lander is only for
travel, and that the first thing you do on arrival on the lunar surface is
to unload the living quarters and bury them well enough to shield them.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. | henry@xxxxxxxxxxxxx
.

Relevant Pages

  • Re: Blisters n microwaves
    ... > Even MRI exciting frequencies of sufficient power density to work would ... Everything requires shielding, it's simply what ... water, but might require a long bake. ... I watched a guy finish the edges of saw cut, 4" thick bluestone by spraying ...
    (rec.boats)
  • Re: TransHab as storm shelter
    ... >>20cm is enough for shelter from solar storms? ... > shelter and relatively little shielding on the rest. ... the manned sections having zip-together water layers. ...
    (sci.space.tech)
  • Re: Interplanetary exploration in a fantasy setting (surgeons general warning: contains reactionless
    ... concrete and water tanks (which double as balancing ... is this good enough on its own as radiation shielding? ... You can probably get away with a bit less than 10 tons if you're willing ...
    (rec.arts.sf.science)
  • Re: radiation shielding for a habitat
    ... a lot of mass. ... > of liquid water. ... you radiation shielding on par with Earth's atmosphere. ...
    (sci.space.tech)