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Old July 2nd 16, 03:04 PM posted to sci.space.policy
Jeff Findley[_6_]
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Default SLS booster test

In article , says...

Jeff Findley wrote:
Yup. The vibrations go from subsonic, bone shaking, vibrations,
through the audible sound range. In other words, they're *loud*.
So, if you are the US Government launching a billion dollar
satellite to do top secret stuff, would you want it shaken and
blasted with noise for the first two minutes of flight?


Weren't at least a few classified satellite missions flown with Shuttle?

http://www.airspacemag.com/space/sec...318554/?no-ist

suggests there were something like 11 of them.


Yes, and since they were classified, we currently have no idea how much
money it cost to qualify those payloads to fly on the shuttle. But I'm
sure that they had to be put on shaker tables inside acoustic chambers
to simulate the launch environment. After testing, any parts or
assemblies which had issues would need to be "beefed up" and the test
re-run.

Eventually these documents will be declassified, and we'll be able to
read about how hard (or easy) it was to qualify these payloads for
shuttle launch.

For now, all I have is vague anecdotal evidence that it was not at all
fun to qualify some parts of these payloads.

But there are technical papers on the vibration issue that are not
classified. For example at http://ntrs.nasa.gov/, search for:

Vibration Isolation for Launch of a Space Station Orbital Replacement
Unit
Document ID: 20100042181

From the abstract of the above document:

Random vibration testing of one ORU to equivalent Space Shuttle launch
levels revealed that its qualification and acceptance requirements were
exceeded. An isolation system was designed to mitigate the structure-
borne launch vibration environment. To protect this ORU, the random
vibration levels at 50 Hz must be attenuated by a factor of two and
those at higher frequencies even more. Design load factors for Shuttle
launch are high, so a metallic load path is needed to maintain strength
margins. Isolation system design was performed using a finite element
model of the ORU on its carrier with representative disturbance inputs.
Iterations on the modelled to an optimized design based on flight proven
SoftRide MultiFlex isolators. Component testing has been performed on
prototype isolators to validate analytical predictions.

Right from the abstract, "Design load factors for Shuttle launch are
high". And in this case, a special vibration isolation system had to be
designed for the ORU or "orbital replacement unit" due to this fact.
So, engineering cost went up and launch mass increased for this ORU due
to the vibrations from the SRBs.

Again, large segmented solids are not at all ideal for a launch vehicle.
SLS increases the SRB size from 4 segments (used on the shuttle) to 5
segments. There will surely be an increase in vibrations due to this
change.

Jeff
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