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Paul Milenkovic wrote:
Most four-cylinder car engines these days have balance shafts to counteract the inherent roughness of a less-than-eight cylinder motor. Is one to suppose those weights on springs are the SRB version of balance shafts?
On the other hand, the whole thing sounds like some massive kludge. Isn't there any other way to dispense with these fixes upon fixes? Yeah, I know, it is called Direct, which is a minor variation on something once called Shuttle C.
[begin quote] Ah! You mean resonant burn. Yes, I am a bit familiar with the problem (aero313 is the real expert), since we had to address it with the TU-903/Castor 120 Taurus first stage. Its frequency (and amplitude) is inversely proportional to the length of the burn cavity, some 8 m long for the C120 (the amplitude is also somewhat proportional to the chamber pressure.) Also, the lower the frequency, the more "responsive" the structure is to the thrust oscillations that the resonant burn causes. I remember during those days thinking "this is the largest in-line solid stage I ever want to use" (the ET and general arrangement of the Shuttle alleviate that problem).
Now we have Ares, with an over 40m long solid first stage - about 5 times the Taurus' length! Ouch! [end quote]
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This page contains a single entry by Rand Simberg published on August 20, 2008 9:16 AM.
Most four-cylinder car engines these days have balance shafts to counteract the inherent roughness of a less-than-eight cylinder motor. Is one to suppose those weights on springs are the SRB version of balance shafts?
On the other hand, the whole thing sounds like some massive kludge. Isn't there any other way to dispense with these fixes upon fixes? Yeah, I know, it is called Direct, which is a minor variation on something once called Shuttle C.
Check this out (by Dr. Elias):
http://forum.nasaspaceflight.com/index.php?topic=11980.msg309609#msg309609
[begin quote] Ah! You mean resonant burn. Yes, I am a bit familiar with the problem (aero313 is the real expert), since we had to address it with the TU-903/Castor 120 Taurus first stage. Its frequency (and amplitude) is inversely proportional to the length of the burn cavity, some 8 m long for the C120 (the amplitude is also somewhat proportional to the chamber pressure.) Also, the lower the frequency, the more "responsive" the structure is to the thrust oscillations that the resonant burn causes. I remember during those days thinking "this is the largest in-line solid stage I ever want to use" (the ET and general arrangement of the Shuttle alleviate that problem).
Now we have Ares, with an over 40m long solid first stage - about 5 times the Taurus' length! Ouch! [end quote]
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