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21 August 2008

Shocks in Rockets?

NASA to use shock-absorbers to fix shaking in new Ares rocket

I don't know about you you, but I look forward to all the different weeks that the Science/Discovery Channel does during the year.  Shark Week is probably the most famous, but my favorite is Space Week.  If you can't any of it, you might have seen the series Moon Machines, where they talk about the hardware and all the problems they had developing it. The episode on the Saturn V talked about the how the second stage was the red headed step-child of the rocket.  The first stage was pretty much complete and mission bloat kept increasing the size of the third stage containing the Command, Service and Lunar Modules.  This meant cannibalizing the second stage.  In addition, during the flight of Apollo 6, pogo oscillations structurally damaged the rocket, reminiscent of the tiles being knocked off the shuttle.  Those vibrations ruptured a the hydrogen feed line to the igniter on on of the engines on the second stage, causing it to fail.  This caused the onboad computer to shut the engine down, but because the controls were wired incorrectly, another perfectly functioning engine was shut down.

Various shock absorbers were developed to dampen out the oscillations and none of the subsequent Apollo flights had the same problem.  I wonder how much of the need for the shock absorbers was taken from lessons learned during Apollo?