Newsgroups: sci.space.history
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Mercury Parachute Escape?
Date: Sun, 8 Mar 1998 03:33:36 GMT

In article <01bd474c$a512c800$0f03de8b@mtmpc.sys.uea.ac.uk>,
Michael Morton <mtm@tuna.uea.ac.uk> wrote:
>> ...Shepard and Grissom had the personal parachutes...
>
>At the time, people where looking at bail out from orbit systems. One
>I read about in a book from the period had the astronaut strapped to
>a heat shield consisting of a large bag that inflated with some sort
>of foaming polymer that quickly became rigid...

Actually, that came much later -- it wasn't during the Mercury days.
Early in shuttle development, for some reason there was some money spent
on looking at various issues of orbital rescue, including the possibility
of orbital bailout.  That's where the foam-in-place heatshield, among
other concepts, showed up.

(The one I liked best was the orbital parachute.  Given a specially
designed parachute and a heat-resistant spacesuit -- which need be no
better than the special Gemini suit built for Gene Cernan's abortive
maneuvering-unit spacewalk -- you can actually parachute all the way from
orbit.  The parachute gives you a sufficiently low mass/area that you
decelerate at extremely high altitude, where heating is not severe.)
--
Being the last man on the Moon                  |     Henry Spencer
is a very dubious honor. -- Gene Cernan         | henry@zoo.toronto.edu

Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: All hands abandon ship!
Date: Fri, 5 Jan 2001 18:16:15 GMT

>At its most simplistic this might be done with a  space suit, a parachute, a
>personal heat shield and a small thruster to de-orbit and keep the heat
>sheild aligned...

You don't really need the heat shield, given a heat-resistant parachute
and a spacesuit designed for the job.  Gene Cernan's Gemini 9 suit had a
very heat-resistant lower half, as a precaution for the planned tests of
the (hydrogen peroxide) maneuvering backpack.  If your whole suit can be
made that tough, then you deploy the parachute (which has to be designed
for the job) *before* reentry.  It decelerates you very early, at very
high altitude in very thin air, keeping the heating rate down to what the
suit and parachute can handle.  Some crucial areas, e.g. the shroud lines,
would probably need a bit of rubber ablator on them.

"Drop at 1,300,000ft.  Deployed canopy at 1,000,000ft.  Eventually the
ground showed up."
--
When failure is not an option, success  |  Henry Spencer   henry@spsystems.net
can get expensive.   -- Peter Stibrany  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: All hands abandon ship!
Date: Sat, 6 Jan 2001 05:37:26 GMT

In article <3A567D74.C2C01D1A@mit.edu>,
Jason Goodman  <goodmanj@mit.edu> wrote:
>> If your whole suit can be made that tough, then you deploy the
>> parachute (which has to be designed for the job) *before* reentry.
>> "Drop at 1,300,000ft.  Deployed canopy at 1,000,000ft.  Eventually
>> the ground showed up."
>
>There must be enough atm. drag to allow the parachute to deploy
>cleanly...

No, it has to be designed to deploy *without* atmospheric drag, e.g. by
inflatable tubes sewn into it.  Not a big problem, but again, it really
does have to be designed specifically for the job.

>Another unrelated issue: a chute designed for re-entry probably won't
>work very well lower down.  One might have to cut loose the re-entry
>parachute and deploy a second atmospheric chute when you reach the
>stratosphere...

I think the concept I saw discussed used a single chute, but you could
be right.  It's not like these ideas have been explored thoroughly.
--
When failure is not an option, success  |  Henry Spencer   henry@spsystems.net
can get expensive.   -- Peter Stibrany  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: All hands abandon ship!
Date: Sun, 7 Jan 2001 05:54:03 GMT

In article <slrn95d4r7.cpt.soup@holly.tampabay.rr.com>,
John R. Campbell <soup@jtan.com> wrote:
>>You don't really need the heat shield, given a heat-resistant parachute
>>and a spacesuit designed for the job...
>
>	Actually, wouldn't a BIG balloon (on the scale of the Echo series
>	of inflatable satellites) be adequate to support re-entry with
>	as high a drag area and as low density possible?

Yes, very possibly.  I don't remember seeing that approach used in any of
the bailout-kit systems, but certainly such designs have been suggested
for reentry.  Indeed, the Russians tested an inflatable heatshield last
year (although details are scarce because they're hoping to market it).

Phil Bono's first SSTO design, back around 1960, used a ballute for
recovery... and it doubled as the landing system, because it was inflated
with hydrogen, and the descent rate reached zero (until the hydrogen
cooled down) at an altitude of several thousand feet...

>	Of course, what with various little strikes, this puppy would
>	leak tout suite...

Probably not enough to matter.

>	The biggest question is, once you've started the de-orbit
>	procedure (the retros must fire BEFORE deploying the 'chute)
>	YOU ARE COMMITTED, and there's no fail-safe mechanism.

This is what the reserve chute is for. :-)  If the main chute opens
properly, just unstrap the reserve chute and throw it away.

>	Even assuming this works just fine, you still need adequate
>	consumables while awaiting the ground's arrival.

True.  That's an hour or so.
--
When failure is not an option, success  |  Henry Spencer   henry@spsystems.net
can get expensive.   -- Peter Stibrany  |      (aka henry@zoo.toronto.edu)