Re: MMU Question

From: Jorge R. Frank (jrfrank_at_ibm-pc.borg)
Date: 03/24/05

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    Date: Wed, 23 Mar 2005 21:44:49 -0600

    "Andrew Lotosky" <skylon@gmail.com> wrote in
    news:1111635245.416302.20970@z14g2000cwz.googlegroups.com:

    >
    > LooseChanj wrote:
    >> Today's APOD picture features McCandless flying an MMU 100 meters
    > from the
    >> payload bay. Someone is arguing if the MMU were to fail, the poor
    > astro is
    >> screwed. I'm thinking it would be relatively easy to just fly the
    > orbiter
    >> over, and either grabbing him with the RMS or scooping him up in the
    > payload
    >> bay. (The latter being trickier.) Who's right? And one more thing,
    > what
    >> sort of failure modes did the MMUs have? What could have possibly
    > stranded
    >> an astro out riding one?
    >
    > I'm susprised this wasn't brought up, but, EVA's are done with two guys
    > and two MMU's are avaiable.

    I'm sure you meant to write, "were available".

    > The odds of BOTH MMU's failing are pretty damn high.

    I suspect you meant to write, "damn low".

    > Why not just send the other EVA Astronaut out to get his
    > partner?

    The MMU didn't fly much; every flight was essentially a test flight. A
    malfunction on one MMU could therefore be indicative of an undetected
    design flaw, to which the other MMU would have to be assumed to be
    vulnerable unless proven otherwise. In that case it makes more sense to use
    the (slightly, at that point) more proven capabilities of the orbiter to do
    the rescue, rather than relying on the other MMU.

    There's also the fact that the orbiter has much more delta-V capability at
    its disposal than the other MMU, and therefore has better odds of
    completing the rescue before propellant runs out. It would be really bad to
    send the second MMU after the first, only to have it run out of propellant
    and create a three-body (41-B) or four-body (41-C, 51-A) problem. 

    -- 
JRF
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    Relevant Pages

    • Re: MMU Question
      ... > payload bay. ... Someone is arguing if the MMU were to fail, ... > an astro out riding one? ...
      (sci.space.shuttle)
    • MMU Question
      ... Today's APOD picture features McCandless flying an MMU 100 meters from the ... payload bay. ... Someone is arguing if the MMU were to fail, the poor astro is ...
      (sci.space.shuttle)
    • Re: MMU Question
      ... >> itself, mind you, because the MMU is highly redundant). ... sets of thrusters, precisely to permit dealing with such situations), and ... uses the other side to stop the spin. ... probably the orbiter comes and gets him, to minimize demands on the MMU ...
      (sci.space.shuttle)
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