Re: SPACE: Why so much EVA on ISS?

From: Doug Jones (djonesxcor@qnet.com)
Date: Sat Mar 17 2001 - 16:36:30 MST


Chuck Kuecker wrote:
>
> More than that - what's the rationale behind putting all those cables on
> the outside of the units? Every cable that pierces the hull is a potential
> leak - and any wiring problems now force an EVA, with attendant loss of
> expensive atmosphere. The cabling is now more susceptible to damage from
> space junk, etc.
>
> What's so difficult about running the cabling and piping inside the
> interconnections?

The russians did all their connections through hatchways, which can be a
hazard when you have to close those hatches in an emergency. There is,
however, a third way- connectors outside the hatches, but within the
docking collar, which can be mated after the the hatches are open but
still allow the hatches to be closed. The narrow space between the
hatches is essentially an airlock.

Ascii drawing:

-------------- ----------------
              \ /
               \ /
                \ /
                #------# <docking collars
                | |
                +~~~~~~+ <Cabling connections between modules
                | |
               / \ (using standard hermetic
              / \ bulkhead connectors)
             / \
                | |
                +~~~~~~+
                | |
                #------# <docking collars
Module a / \
              / \ Module b
             / \
------------- ---------------

This wasn't invented at NASA so it was forbidden -thus the myriads of
hull penetrations and vulnerable cables mated on makework EVAs.
Sometimes I don't even try to suppress my scorn.

--
Doug Jones, Rocket Engineer



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