Re: SPACE: Why so much EVA on ISS?

Date: Sat Mar 17 2001 - 09:13:35 MST

In a message dated 3/17/01 9:18:29 AM Central Standard Time,

> 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?

On one level, the answer lies in pictures of the interior of Mir in its later
years. Mir grew haphazardly and with lots of additions and changes that
weren't foreseen when it was originally conceived. Notice in pictures of Mir
that the main openings between modules were full of cabling and hoses. When
they did have to close off one section from another, it proved to be very
difficult to figure out how to disconnect those cables so that an air-tight
seal could be created between modules. This presented an extreme safety
hazard, as well as a lack of flexibility in reconfiguring the modules.

There's no question that the ISS design is right in maintaining the main
connection between modules as a simple opening for people to pass through
that can be easily closed and sealed. The idea I suggested in my original
post could be implemented with a fairly substantial telescoping "raceway" or
conduit with automatic couplings for power, signal, air, water and coolant
connections. The more I think about this, the more I realize that there
would be a significant weight penalty in implementing this system. On the
one hand, you'd have to have the additional weight of the driving mechanism
to connect the conduit-carrier. On the other, you'd have to have a lot of
redundant switching and valving to make the system completely modular.
Finally, you'd have to design the system so it could be serviced from the
outside and "helped along" manually, if all the connections didn't form up
properly. Even so, the benefit in lower EVA load and forward-compatibility
would be significant.

       Greg Burch <>----<>
      Attorney ::: Vice President, Extropy Institute ::: Wilderness Guide -or-
                                           ICQ # 61112550
        "We never stop investigating. We are never satisfied that we know
        enough to get by. Every question we answer leads on to another
       question. This has become the greatest survival trick of our species."
                                          -- Desmond Morris

This archive was generated by hypermail 2b30 : Mon May 28 2001 - 09:59:41 MDT