From: Jeff Davis (jdavis@socketscience.com)
Date: Sun Jan 07 2001 - 23:33:43 MST
On Sat, 6 Jan 2001, Steve Van Sickle quoted Doug Jones, who wrote :
>> spreadsheet for Rotary Rocket). Secondly, while the bulk density of a
>> body is about 1, the lungs and other air filled spaces are <<1, and
>> would experience very strong buoyancy effects. At more than 25 gees
>> this would be likely to cause tearing of lung tissue. Also, the
>> hydrostatic pressure at the lowest point in the lungs would be far
>> higher than the gas pressure in the lungs leading to edema as liquids
>> leak through the walls of the alveoli. In tests, healthy subjects
>> immersed in water were able to take about ten gees for about fifteen
>> minutes before losing consciousness.
Then Steve added:
>How about filling the lungs with saline at about the same density? Either
>the passenger could be placed in profound hypothermia and so do without
>oxygen (or a heartbeat, for that matter) for 30 or 40 minutes, or have the
>blood oxygenated by a heart/lung machine.
Excellent posts, Doug and Steve. I anticipated the bouyancy problem you
mention Doug--note my comment about liquid-breathing apparatus--but didn't
elaborate on it because it's all something of a flight of fancy. I was
seeking the upper bound implied by Brent's original question:
>How many gs can a human
>stand for extended periods of time?
So, a bit more then?
Additional problems include: High Pressure Nervous Syndrome (HPNS), which
results from an overly fast rate of compression; and, of course,
decompression complications.
For a diver, HPNS is bad news because he has to function as a worker, not
to mention survive in a hazardous environment, but for an astronaut just
laying back for the trip, it's not so critical. I'm not a hundred percent
certain, but as I recall the theory of HPNS attributes it to mechanical
distortion--due to compression--of neural cell membranes, and that it can
be prevented or reversed by administration of anesthesia, which, absorbed
by the membranes, causes them to swell. First it restores normal nerve
function, then, with additional absorbtion and swelling, it puts you to
sleep. So to prevent our astronaut from becoming wired to the point of
seizures--that's what HPNS does to you--we have to medicate him.
As Steve points out, saline filling the lungs addresses the hydrostatic
pressure differential/bouyancy problem as it relates to the lungs (and
other body gas spaces), but introduces the 'drowning' problem. To counter
that, Steve proposes profound hypothermia and a heart-lung machine. Let me
add that this arrangement also takes care of the decompression problem. Or
you can skip the hypothermia, fill the lungs with saline, and just go for a
'lung' machine.
Or you can take the hypothermia to the extreme, cryonically vitrify the
astronaut, turning him/her into a glassy rock, thus achieving some serious
g-resisting structural strength. Then you can go REALLY fast. What's the
shear strength of the block of diamond that would then serve as the
supporting 'pressure vessel' for the cryo-astronaut?
What with the escalting complexity of life-support with increasing G
forces, I conclude that one G, a good book, some videos, and a bucket of
McNuggets will do just fine. Two days one hour and fifty minutes (at
mars-to-earth closest approach) is less time than it takes to cross the
Atlantic by boat, even today.
By the way, if mars is on the other side of the sun, 2.524 AU from earth,
the trip time at one G is still only 4 days 13 hours 20 min. And that's
not even taking into account the solar slingshot effect.
And one last comment. The rotary rocket engine, the spinning wheel,
exhaust nozzles at the periphery, dynamic geometric simplicity replacing
complex and expensive turbopumps, remains for me a concept of breathtaking,
dazzling elegance. I am bereft and inconsolable at the thought that it is
not to be. Rather, I choose to believe that persons of venality and small
vision, the spawn which curseth humanity by their abundance, have simply
postponed the day when that beauty of engineering shall grace the skies.
Tell me Doug--lie if you have to--that there is still hope.
Best, Jeff Davis
"Everything's hard till you know how to do it."
Ray Charles
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