[extropy-chat] FWD [forteana] Re: Are dwarfs better forlongduration spaceflight?]

spike spike66 at comcast.net
Tue Sep 6 05:47:03 UTC 2005


> bounces at lists.extropy.org] On Behalf Of Adrian Tymes
> To: ExI chat list
> Subject: RE: [extropy-chat] FWD [forteana] Re: Are dwarfs better
> forlongduration spaceflight?]
> 
...
> 
> Actually, considering how small a fraction makes up the crew and crew
> support - the "payload" - of any manned space vehicle to date...yes, we
> are talking about shaving close to the margin...

Ja, ok I see now where is the disconnect.  Assume the
surface-landing manufacturing machinery is launched
separately, sent on ahead.  It can go with slow, highly
efficient ion drives, all the tricky stuff, since it
has no consumables.  The hab module is in a hurry, so
it will likely use chemical rockets on a Hohmann 
transfer orbit.  

All the astronaut does is to inject into Mars synchronous 
orbit for a couple years in order to guide the machine 
real time.  The design exercise is now just the human 
hab module.  In that scenario, I imagine the
vehicle as a spherical shell about 4 times her height.
The propulsion system scales with the mass of that shell,
which scales as the cube of the diameter.  The heating
system scales approximately as the square of the
diameter, since heat loss is a function of surface
area.  The antenna that sends signals to the surface
of Mars and to Earth does not scale with the size of
the orbit vehicle.  The system needed to deal with
waste processing scales linearly with the amount
of food and water she devours.

Given these things, try to determine what is the
function of weight as a function of the astronaut's
height.  Assume a minimum crew, one person.  I have
pointed out the mass of the shell and the mass of
the air inside scale as the cube, heater as the
square, waste processing some unknown function and
communications gear no scaling.  Does the weight
scale approximately as the 2.4 power of the height
of the astronaut?  How much?

I kinda jumped into this assuming the participants
were up on the previous, more detailed treatment
we did on this about 4 or 5 yrs ago.  We messed up
this time by not defining the mission up front, so
everyone was going on different initial assumptions.

I think I have a scenario where one human could go
to Mars orbit and return with a single heavy launch,
plus another heavy launch to carry the landing
machinery.  That wouldn't break the bank.

spike







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