>From: rball84213 RemoveThis @aol.com (Richard Ballard)
>Has anybody discussed how an astronaut forced to continually
>wear a pressure suit and recline within a small space capsule
>for tens of days will avoid developing bedsores?
>
As others have pointed out, a Mars mission will require more than just tens of
days, unless we have a continuous thrust system such as an ion drive. This has
been used in the Deep Space One mission (not to be confused with Deep Space
Nine) and at least one communications satellite.
<a style='text-decoration: underline;' href="http://hs.onysd.wednet.edu/clubs/astroweb/club/news/deep_space_1.html" target="_blank">http://hs.onysd.wednet.edu/clubs/astroweb/club/news/deep_space_1.html</a> Even
with this, I think mission time will be too long for a small capsule approach.
In Expanded Universe Robert A. Heinlein calculated the travel time to Mars
using constant boosts of 1 g, 1/10 g, 1/100 g, and 1/000 g. At one g the round
trip time is 4.59 days, but this is out of the question. We do not even have
any good theories as to how to achieve a 1 g continuous boost over a period of
days. I think even 1/10 g is unattainable, and that results in a round trip of
14.5 days. MAYBE this is doable in a small capsule, but it is stretching
things. A more realistic acceleration of 1/100 g gives a round trip of 45.9
days, and I think that is out of the question. At 1/1000 g, the trip is 145
days, and I think that might be our most realistic assumption for a continuous
boost with current technology.
Without continuous propulsion, it is out of the question. Months at least
would be needed each way. If we use a Hohmann minimum energy orbit, the travel
time is about 8.5 months each way. <a style='text-decoration: underline;' href="http://makeashorterlink.com/?K2B4267D7" target="_blank">http://makeashorterlink.com/?K2B4267D7</a> If
we are willing to use more fuel we can get there faster, but any realistic fuel
consumption still means a mission much too long for a small capsule to work.
This is simply not an option for a Mars mission. Both physically and mentally,
staying in an acceleration couch while wearing a pressure suit for that length
of time is out of the question. The astronaut would be very weak and ill at
best, and might not even live through the experience. He certainly would be in
no shape to walk on Mars, if he did live that long. I also doubt if there is
anyone who could remain sane for that long under those conditions.
I don't think direct lift off from Earth is an option either. I think the
heaviest booster we have ever made was the Saturn V. I doubt if even one of
these could launch the mission. Even if we did assume one person, smallest
possible capsule with him strapped to the couch all the way, no landing just
orbit and return, minimum possible life support, and the hell with health or
sanity, even then I don't think a Saturn V could have launched the mission.
Several launches will be necessary to assemble the mission. I am guessing that
trying to take along consumables will be out of the question, even if it is a
one person mission. A more practical idea would probably be hydroponics for
food and oxygen. I don't think these launches should come from the Earth
though. I think we should build a colony on the moon, then use it to build and
launch the Mars mission. Some things will have to come from Earth, for example
computer chips. I don't think these will be manufactured by a lunar colony any
time in the near future. Still, they can make and launch the massive stuff,
such as the structure of the craft itself. We can probably use and
electromagnetic mass driver for these launches, instead of chemical fuel. The
moon has plenty of oxygen (the crust is 43% oxygen by weight) but the fuel
itself is lacking in the Lunar crust. Instead of trying to extract hydrogen
(50 parts per million) or other rare and hard to get stuff for fuel, a mass
driver looks a lot more practical.
I think magnesium could be used as ion fuel. It is present in sufficient
amounts (about 5% by weight) and has a fairly low boiling temperature. It
should be possible to use a solar array to vaporize it, then shoot it out as an
ion stream for continuous propulsion. The Deep Space One mission uses xenon,
but that is not present at all in the lunar crust. The solar panels for the
mission can probably be made on the moon too, instead of launched from Earth.
They will already be using hydroponics for their own food and oxygen needs, so
setting them up in this craft should be simple enough. Ammonium nitrate for
plant food might need to come from Earth. What I am guessing is that the lunar
colony could build most of the stuff for this ship, and some minimal stuff
comes from Earth, especially the electronics needed to get into Earth orbit.
Then it is flown into Earth orbit, where launches can rendezvous with the ship
in order to complete the electronics, send up ammonium nitrate and whatever
else is needed for hydroponics (not seeds, these were already sent from Lunar
launches), crew, various scientific probes and equipment, and fuel for the
landers. I have tried to figure out how to get this from Luna, but I don't see
a way. Liquid oxygen is not practical, because it requires cryogenic storage
and even with the best storage it boils off over time. I think trying to store
it as high pressure gas would be too bulky to be practical. The Apollo
missions used hydrazine for fuel and nitrogen tetroxide as oxidizer. Nitrogen
is present in the lunar crust at 100 PPM, twice as much as hydrogen. Possibly
we could make the nitrogen tetroxide on the moon. Hydrazine (N2H4) uses two
elements that are rare on the moon. UDMH ((CH3)2NNH2), another fuel used by
Apollo, adds carbon to the list of rare stuff we need. Alcohol needs carbon
(another 100 PPM substance) and hydrogen. I'm guessing that if we want to land
on Mars, lander fuel needs to come from Earth. Possibly they would only send
the needed rare elements, and we could synthesize it onboard, with Lunar
oxygen?
I do have one somewhat wild idea for lander fuel, but I doubt if it is
practical. Here it is, can anyone with engineering knowlege tell me if it
might work? Magnesium and aluminum both burn, and both are present in the
Lunar crust. Could a hybrid solid/liquid rocket be built? It would have a
combustion chamber similar to the Space Shuttle solid rocket boosters, but
lined with aluminum, magnesium, or an alloy of these two. Then we pump in
oxidizer (liquid oxygen for short missions, a more storable oxidizer such as
N2O4 for longer ones) and ignite it. Would we get enough thrust to make it
work as a rocket? We can vary the thrust by controlling the amount of oxidizer
pumped in, and start and stop it, unlike most solid fuel rockets.
The best part is that I think the cost of a lunar colony would be similar to
trying to base a Mars mission from Earth. At the end though, we have both a
colony and a Mars mission. With Earth basing, all we have is a Mars mission.
I think a lunar colony could put together a much larger mission, too.
Over on alt.fan.heinlein, I have discussed my ideas for a lunar colony fairly
extensively. I have put them into a text file, which I will now post here in a
new thread. Any and all comments are welcome.
--
Ferengi rule of acquisition #192: Never cheat a Klingon...unless you're sure
you can get away with it.<!-- ~MESSAGE_AFTER~ -->
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