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Space station future adrift (Soyuz purchase crisis)



 
 
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  #21  
Old December 1st 04, 05:01 AM
Alan Anderson
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"D Schneider" wrote:

Henry Spencer wrote:
[...]
[...] A quick-donning, one-size-fits-all,
lightweight emergency suit is most unlikely to be a high-pressure suit,
at least not any time soon.


Are the "skin suit" designs a candidate for this? Perhaps with a
high-pressure helmet?


Skinsuits are decidedly not one-size-fits-all, nor would I expect them to
be particularly quick-donning *or* high-pressure.
  #22  
Old December 1st 04, 05:48 AM
Derek Lyons
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"D Schneider" wrote:

IIRC, previous discussions pointed out that "skin suits" hadn't completely
solved the joint problem yet,


"Skin Suits" haven't solved *any* of their problems yet.

D.
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-Resolved: To be more temperate in my postings.
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  #23  
Old December 1st 04, 06:03 AM
Pete Lynn
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"Henry Spencer" wrote in message
...


As Rand says, this is a very old idea. Unfortunately, it
turns out that legs are really quite useful in free fall, for
holding you in place and maneuvering you around (using
foot restraints, of course). The pod concepts mostly date
from a time when people thought that working while
floating free would be easy, when in fact it's extremely
difficult.

The idea is not ridiculous, but it's by no means obviously
attractive.


Considering the dexterity that some people manage with the likes of
bicycles, forklifts, even helicopters, I am hopeful that some kind of
remote leg, perhaps with prehensile toes, might be workable. At first
thought, human legs do not seem that well suited to space, many much
longer grappling legs, (perhaps foot operated), might be of some use.
Even if this is not as coordinated as a suited leg.

The pod concepts do not necessarily have to replace space suits, just
supplement them. Designing the space station, or whatever, with such
pods in mind might also be sensible. For example, the capacity to
externally detach small things and then bring them through an airlock
into the pod for onsite fine work without gloves might make some sense.
Detaching larger objects and carrying them into a hanger for such fine
work also seems highly desirable. A gloved hand is still far inferior
to bare hands for fine work.

I think such pod approaches should enable you to greatly reduce suit
time at little extra cost. Even having a podded person on hand to
assist the suited "surgeon" with tools, air, extra eyes, power, heavy
grappling, a mobile platform, simple tasks, fine work on detached
components, etc., might greatly speed up the operation at little cost.
The likes of a quick flyby inspection of the space shuttle tiles would
also be possible, not that I am suggesting use of a shuttle.

Point being, I suspect such a pod system might be a useful and justified
addition to space station operating equipment. Greatly increasing your
options and ability to quickly do stuff.

Pete.


  #24  
Old December 1st 04, 04:47 PM
Henry Spencer
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In article opsia5gyicemtzlb@d3h1pn11,
D Schneider wrote:
[...] A quick-donning, one-size-fits-all,
lightweight emergency suit is most unlikely to be a high-pressure suit...


Are the "skin suit" designs a candidate for this? Perhaps with a
high-pressure helmet?


Nope. Aside from the fact that skinsuits are not yet a proven approach --
the basic concept works, but whether some detailed engineering problems
can be adequately solved is unknown, due to lack of funding -- they don't
work for this at all.

As things stand now, skinsuits most emphatically are *not* quick-donning
or one-size-fits-all. Donning is tedious and difficult, to the point that
this rates as one of the important unresolved problems. Moreover, they
have to be precisely custom-tailored, to the point that the intended
wearer has to avoid gaining or losing more than a pound or two if he wants
the suit to fit properly. Modern materials might help the tailoring
problem, but the donning problem is harder.

Finally, all skinsuits made to date are low-pressure. Helmet and body
pressures must match; there is a continuous liquid column between the lung
capillaries and the skin capillaries, after all. And the one attempt so
far at producing an 8psi skinsuit glove was unsuccessful -- techniques and
materials which work quite well at 3.5psi don't scale well enough.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |
  #25  
Old December 2nd 04, 03:14 AM
D Schneider
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Henry Spencer wrote:

[...]
As things stand now, skinsuits most emphatically are *not* quick-donning
or one-size-fits-all. Donning is tedious and difficult, to the point
that this rates as one of the important unresolved problems. Moreover,
theyhave to be precisely custom-tailored, to the point that the intended
wearer has to avoid gaining or losing more than a pound or two if he
wants the suit to fit properly. Modern materials might help the
tailoring
problem, but the donning problem is harder.


Dang. Modern materials might include some of the artificial muscle
materials, but these aren't going to be ready for *this* application for a
while; might as well be unobtanium. However, when the decade dawns that
these are the material of choice, they might as well use them to solve the
donning problem as well as the tailoring problem.

Finally, all skinsuits made to date are low-pressure. Helmet and body
pressures must match; there is a continuous liquid column between the
lung capillaries and the skin capillaries, after all. And the one
attempt so
far at producing an 8psi skinsuit glove was unsuccessful -- techniques
and materials which work quite well at 3.5psi don't scale well enough.


Okay, we rig the transporter to remove nitrogen, and just aim us into the
spacesuits.

"Careful, Captain...the machine has bin leaving a few wee embolisms of
late; we dinna wanna lose ye..."

/dps

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  #26  
Old December 2nd 04, 05:24 AM
Henry Spencer
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In article opsicy53faemtzlb@d3h1pn11,
D Schneider wrote:
Modern materials might help the tailoring
problem, but the donning problem is harder.


Dang. Modern materials might include some of the artificial muscle
materials, but these aren't going to be ready for *this* application for a
while; might as well be unobtanium...


You don't need to get quite that drastic. :-) Skinsuits benefit a lot from
materials with a non-linear stress-strain curve, and some of those already
exist.

With a normal elastic material, if you want to stretch it twice as far,
you have to apply about twice as much force. But there are some
materials, Spandex being one of them if I recall correctly, which are
different. They start out the normal way, but when you reach a particular
amount of stretch, the curve flattens out: the material stretches, and
stretches more, and stretches still more, with only the most minute
increase of force. Eventually the required force starts rising again, but
there's a wide flat section in the middle of the curve. This is exactly
what's wanted for a skinsuit: essentially constant force over a wide
range of stretch. Not only does this accommodate flexing of the body, but
if that range is wide enough, it can also accommodate some discrepancy
between the design size and the actual size of the body.

But at donning time, you're still trying to put on something that's
squeezing hard all the time. What's needed is a way to turn that off and
on, either on command or automatically in response to ambient pressure (a
fabric that shrinks in vacuum). Not simple.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |
  #27  
Old December 2nd 04, 09:40 AM
D Schneider
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Henry Spencer wrote:

[...]
But at donning time, you're still trying to put on something that's
squeezing hard all the time. What's needed is a way to turn that off and
on, either on command or automatically in response to ambient pressure (a
fabric that shrinks in vacuum). Not simple.


Well, that's what I was thinking of the muscle fabric for...to take up the
slack you need for donning. Slip on your "Incredibles" suit, getting your
legs in nice spacious openings (like Slates, not Levis), and push a button
to cinch things up. But even as promising as the Sci Am article was, it
will still be a while....

/dps

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  #28  
Old December 2nd 04, 11:06 AM
John Doe
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D Schneider wrote:
Well, that's what I was thinking of the muscle fabric for...to take up the
slack you need for donning. Slip on your "Incredibles" suit, getting your
legs in nice spacious openings (like Slates, not Levis), and push a button
to cinch things up.


This will be developped. The documentary Back to the Future (2 I think)
showed such garments in action, including shoes.

More likely would be some sort of "heat shrink" fabric which, upon
encountering a catalyst, shrink to fit. (catalyst could be some spray of a
chemical for instance).

One would also need to have a reverse chemical reaction to make the fabric
expand again so you can egress the suit.

Nut again, this is not needed for emergency return to earth since the human
will not need mobility while in space, and will automatically regain mobility
once differential pressure is reduced as altitude decreases.
  #30  
Old December 4th 04, 08:07 PM
Greg D. Moore \(Strider\)
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"Henry Spencer" wrote in message
...
With a normal elastic material, if you want to stretch it twice as far,
you have to apply about twice as much force. But there are some
materials, Spandex being one of them if I recall correctly, which are
different. They start out the normal way, but when you reach a particular
amount of stretch, the curve flattens out: the material stretches, and
stretches more, and stretches still more, with only the most minute
increase of force. Eventually the required force starts rising again, but
there's a wide flat section in the middle of the curve. This is exactly
what's wanted for a skinsuit: essentially constant force over a wide
range of stretch. Not only does this accommodate flexing of the body, but
if that range is wide enough, it can also accommodate some discrepancy
between the design size and the actual size of the body.

But at donning time, you're still trying to put on something that's
squeezing hard all the time. What's needed is a way to turn that off and
on, either on command or automatically in response to ambient pressure (a
fabric that shrinks in vacuum). Not simple.



No, something simpler. Something that reacts to a piezoelectric force.

Done a nice loose fitting suit, plug in the battery, bamm... skin tight.


--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |




 




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