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

spike spike66 at comcast.net
Thu Sep 1 05:59:50 UTC 2005


> 
> "Terry W. Colvin" <fortean1 at mindspring.com> fnarded:
> 
...
> 
> Designing for absolute minimum weight aerospace vehicles is fraught
> with problems...

Granted, however we are discussing only *scaling* as a function
of the needs of the astronaut.  This exercise is not about shaving
close to the margin; the margin is the same for the smaller 
vehicle as it is for the larger.

My notion is that under these extreme conditions, we can
make a spherical hab module with a diameter about four times 
the height of the astronaut.  Not roomy, but survivable.  The
notion then is that the diameter of the sphere scales with
the height of the astronaut, and if so, the mass scales as 
the cube of that height, and if so, finding the smallest
astronaut is everything.


> ... While a measure of weight as saved, it made the vehicle
> so difficult to manufacture that the cost increases by far outweighed
> any operational savings...

Of course, but manufacturing constraints in aircraft,
where you are making many, are not directly comparable
to manufacturing constraints in spacecraft where you
are making one or two.


> ... - thinner skins
> oilcanned and flexed...

Not applicable to a spherical shell.


> ...the scalloped edges around fastener holes
> reduced the fatigue life, and so on...

Generally not applicable to spacecraft.  You would load up the
sphere, insert the hapless astronaut, then weld the
hatch closed.  When she returns, the reentry vehicle
would be attached and the hatch cut open.  


> In a nutshell, while there are advantages to making stringent size and
> weight requirements on your crew, simply making a tight, lightweight
> design is not the complete answer...

OK, but spacecraft are not aircraft.  I agree with all that
is stated here for planes.  


> 
> I also have a bit of a problem with the physical requirements placed
> on a crew. You have also to be concerned with whether or not a given
> cew member can coe with possible extremes that could be encounteed
> on a long-term mission...

I grant you that it will take a very special person to 
pull this off.  We have 6e9 people on this planet from
which to choose.  I think this special person exists somewhere.

> Would, for example, a person of a more delicate
> stature be capable of enduring a longer or more rigorous work schedule?

Yes, I think this durable little person exists somewhere.  Her
job is a lot like a video game.  I see little correlation 
between physical size and endurance at a video game console.

> 
> Okay, sitting in the cabin of a spacecraft on a zero-g coast between
> Earth and Mars is going to favour the lightweight crew member. But
> lugging bits of gear about on the surface of Mars when they get there
> is going to put a much greater strain on the smaller guy...

Ja I should have defined this mission more carefully.  There 
is no lugging stuff around on the surface in this scenario.  The
mission is to insert into Martian synchronous orbit for a little over
two years, during which the astronaut guides robots on the
surface which build things that humans will later use: manufacturing
facilities, a pressure vessel for growing plants and living in,
etc.  After 2.4 years, the craft leaves Mars orbit, injects into LEO,
docks with a reentry vehicle and comes home.

We can carry enough delta V to do all this with current
technology.  In 2.4 years, she should be able to get some
cool stuff accomplished.
 
> ... 
> Like they say, size (in either direction) isn't everything...

In aircraft, I agree.  In Mars missions, size matters more
than anything.

spike


ps The news on in the background as I write.  Damn that
flood in New Orleans is bad.  {8-[






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