Date: Wed, 17 Mar 1993 19:54:58 GMT
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Water Simulations (Was Re: Response to various attacks on SSF)
Newsgroups: sci.space

In article <1993Mar17.175450.27423@iti.org> aws@iti.org (Allen W. Sherzer) writes:
>... I think water tanks and practicing on them is
>a great idea. However, to assume that we can corelate actions in the tank
>to the actions needed to assemble a large space structure (like Freedom)
>in free fall is foolish. 

As a minor case in point, something that got mentioned at Making Orbit...

There are two things really wrong with the water-tank simulation of free
fall.  One is that you are lying in your suit rather than floating in it.
The other is the more obvious issue:  the water has viscosity.

When exiting the shuttle airlock, you reach out and grab a handrail
above the door, and then push off outward.  Apparently, *everyone* who
tries this for the first time in free fall after water-tank practice
bonks his helmet against the outside of the airlock, by pushing off
too hard and helplessly pivoting too far around the handrail.  Even
if he's been warned about the problem.

Not very significant in itself, but an indication of what you can run
into.
-- 
All work is one man's work.             | Henry Spencer @ U of Toronto Zoology
                    - Kipling           |  henry@zoo.toronto.edu  utzoo!henry

Newsgroups: sci.space.policy
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: SSTO size (was Re: landings)
Date: Wed, 10 Jan 1996 00:51:08 GMT

In article <4csadd$go2@crl3.crl.com> gherbert@crl.com (George Herbert) writes:
>The assemble-on-orbit proponents seem to generally downgrade the difficulties
>encountered in such assembly (and similar) operations by both manned and
>unmanned work, in previous experience.  EVA is not a friendly easy working
>environment, and we still have serious problems from time to time...

However, to some extent this is a vicious circle:  EVA equipment and
methods will never get good as long as it is seen as an expensive rarity.
Compare the amounts of operational time required to become an experienced
diver and an "experienced" spacewalker.  Only in the last two or three
years has NASA started doing deliberate in-space experiments to improve
EVA gear and techniques, and a lot of this is still at quite a small
scale, with many inadequacies of existing approaches accepted as laws of
nature. 

For example, as long as you are going to stick with low-pressure suits,
note that in his MIT thesis work, Mitch Burnside Clapp successfully
demonstrated using "skinsuit" technology in an improved glove meant for
conventional spacesuits.  It doesn't scale to higher pressures very
well... but nobody's got serious plans for higher-pressure suits right now
anyway.  For that matter, if we're talking about construction crews doing
extensive and frequent EVA, it's probably better to just keep the
construction shack at a lower air pressure for the sake of vastly more
dextrous gloves. 

EVA work currently is difficult and limited, but major improvements could
be made with determined effort.

Incidentally, why assume that in-orbit assembly has to be done by EVA?
A pressurized assembly hangar would be immensely valuable and not all
that difficult to build.
-- 
The Earth is our mother.                           |       Henry Spencer
Our nine months are up...                          |   henry@zoo.toronto.edu

Newsgroups: sci.space.policy,sci.space.history
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Future manned space & avoiding the Station's/Shuttle's 
	mistakes
Date: Thu, 28 Jan 1999 14:31:17 GMT

In article <ant280925d07M+4%@gnelson.demon.co.uk>,
Graham Nelson  <graham@gnelson.demon.co.uk> wrote:
>There was a telling incident on Mir when the cosmonauts trained
>on the ground to perform the IVA opening up Spektr found that
>everything was the wrong way up: the models in the swimming pool
>didn't reflect reality.

Also of note is an interesting tale -- I haven't verified its accuracy --
that every shuttle astronaut spacewalking for the first time, bar none,
bumps his helmet on the outside of the airlock.  The procedure for
emerging is to grab the outside handrail and push off from inside with
your feet... but doing this in the water tank requires pushing off firmly
because of water drag, and people doing it in vacuum for the first time
invariably push off too hard, pivot around the handrail, and bang into
the airlock before they can stop.
--
The good old days                   |  Henry Spencer   henry@spsystems.net
weren't.                            |      (aka henry@zoo.toronto.edu)