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'Dent' on US Lab debris shielding



 
 
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  #1  
Old November 5th 04, 05:56 PM
Jim Oberg
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Default 'Dent' on US Lab debris shielding


Any more information about this apparent 'dent'? When was it first
'discovered'? What was the last previous time that area was surveyed when
the dent WASN'T there? Has anything like it been seen anywhere else on the
exterior? Seems like the shielding is doing its job -- what might have
happened if the event had occurred in a region WITHOUT shielding?

Nov 4 ISS Status Report:
Next week the SSRMS (Space Station Remote Manipulator System) will be used
for an outside inspection of what appears to be a "dent" in the Lab module's
exterior surface, specifically in the MM/OD (micrometeoroid/orbital debris)
shielding surrounding the pressure shell. [The shielding, made of an
aluminum alloy, is designed to absorb the initial impact of MM/OD, slowing
it down while breaking it into small fragments before it hits the pressure
shell. The shielding is 0.13 cm (0.05 in.) thick and is separated from the
pressure shell by a 10.2-cm (4-in.) gap.]


  #2  
Old November 5th 04, 06:08 PM
Jim Kingdon
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Seems like the shielding is doing its job -- what might have happened
if the event had occurred in a region WITHOUT shielding?


An impact will make a hole rather than a dent, unless the object which
impacted is in a very similar orbit (which would happen pretty much if
and only if it was released from ISS itself).

My first guess is that the "dent" is the result of the shielding
undergoing some kind of thermal expansion/contraction. Maybe someone
with more expertise would have a different first guess.
  #3  
Old November 5th 04, 10:13 PM
Reed Snellenberger
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"Jim Oberg" wrote in
:


Any more information about this apparent 'dent'? When was it first
'discovered'? What was the last previous time that area was surveyed
when the dent WASN'T there? Has anything like it been seen anywhere
else on the exterior? Seems like the shielding is doing its job --
what might have happened if the event had occurred in a region WITHOUT
shielding?


If you're looking into this, it'd be interesting to find out whether NASA
has any plans/capabilities to replace these panels on-orbit (I know there
is the ability to install them as an upgrade on the Russian structures)?
I'd think it would be a little useful to inspect damaged panels to
evaluate the performance of the shielding.

Secondary question: The station is oriented (generally) with the PMA/Lab
end facing in the direction of "travel". Is the shielding roughly
symmetric, or is it thicker on the "forward" and "spacewards" sides? I'm
guessing that the probability of micrometeroid and/or debris impact on
the earth-facing side is much lower than those sides, and that the
probability of damage to the "rear-facing" surfaces would be somewhere
between those two extremes.

If I remember the details of the LDEF experiment correctly, it drifted in
a gravity gradient orientation (long axis pointed towards earth) and
wouldn't have provided much useful data about the isotropy of the
micrometeroid distribution. The only spacecraft I can think of that have
been long-duration, fixed-orientation (mostly), and human-inspectable
have been ISS, Mir, Salut, and Skylab.

--
Reed
  #4  
Old November 6th 04, 04:39 AM
Jim Oberg
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No, that was in the SM.

I'm hearing this dent has been around awhile,
was recently discovered during careful re-analysis of
shuttle images during a 2002 visit.

"Neon Knight" wrote in message
Could this be related to the crunching sound they heard awhile ago?



 




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