Ares 1: Lift Off Drift

[nimbus]

<p>Kyle I've read a lot of your posts when DrRocket is around, and it seems like a good mix of bad chemistry and culture differences, in addition to the fact that you do somehow ignore what he has to say.. It somehow gets lost somewhere between his keyboard and your eyes. He's no more curt than you refuse to walk in his shoes or alter your perception of him to see what he's actualy saying as opposed to what he seems to be saying at (your) first glance.</p><p>&nbsp;I won't derail the thread more than that.. Back on topic..&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[kyle_baron]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> the flame bucket and acoustic supression system were quite a bit larger than what you suggest.&nbsp; It is a matter of complex gas dynamics.&nbsp;&nbsp;&nbsp;&nbsp; <br />Posted by DrRocket</DIV></p><p><strong>I'm still waiting for a response, for the complex gas dynamics and how they apply to the flame bucket, and acoustic suppression system.&nbsp; Just a reminder.</strong><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

 

[vulture4]

Although it doesn't have to do with lift off drift, it's worth noting that the acoustic pressure wave from the Shuttle on STS-1&nbsp; was considerably more severe than had been predicted; there was actual distortion of the aft bulkead on the first flight. I believe the large water-filled bags that hang in the flame trench under the boosters were added as a result. The acoustic enviroment of the launch is extreme and analysis is not always equivalent to experience.

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I'm still waiting for a response, for the complex gas dynamics and how they apply to the flame bucket, and acoustic suppression system.&nbsp; Just a reminder. <br />Posted by kyle_baron</DIV></p><p>I am trying to find a way to dumb it down sufficiently for you to comprehend it.&nbsp; No luck so far.&nbsp; It is pretty obvious to people with the necessary background in physics and rocketry.<br /></p> <div class="Discussion_UserSignature"> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Although it doesn't have to do with lift off drift, it's worth noting that the acoustic pressure wave from the Shuttle on STS-1&nbsp; was considerably more severe than had been predicted; there was actual distortion of the aft bulkead on the first flight. I believe the large water-filled bags that hang in the flame trench under the boosters were added as a result. The acoustic enviroment of the launch is extreme and analysis is not always equivalent to experience. <br />Posted by vulture4</DIV></p><p>Not surprising.&nbsp; The history of analysis of the acoustic environment on payloads near lift-off is that the analysis is not very accurate.&nbsp; Similar things happened on other launches.&nbsp; As a I recall (dimly) when the burms around the Titan (might have been a different launcher)&nbsp;pad were changed the analysis missed the effect of acoustics on the payload section by a lot.</p><p>While not really acoustics, the refledtions of pressure waves in general generated&nbsp;assymetric loads on the nozzle of the early Titan IVB&nbsp;never succumbed to analysis.&nbsp;&nbsp;Gas dynamics analysis can be just plain hard.&nbsp; The Navier-Stokes equation is one of the truly difficult partial differential equations.&nbsp; </p><p>http://www.claymath.org/millennium/Navier-Stokes_Equations/<br /></p> <div class="Discussion_UserSignature"> </div>

 

[Testing]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Not surprising.&nbsp; The history of analysis of the acoustic environment on payloads near lift-off is that the analysis is not very accurate.&nbsp; Similar things happened on other launches.&nbsp; As a I recall (dimly) when the burms around the Titan (might have been a different launcher)&nbsp;pad were changed the analysis missed the effect of acoustics on the payload section by a lot.While not really acoustics, the refledtions of pressure waves in general generated&nbsp;assymetric loads on the nozzle of the early Titan IVB&nbsp;never succumbed to analysis.&nbsp;&nbsp;Gas dynamics analysis can be just plain hard.&nbsp; The Navier-Stokes equation is one of the truly difficult partial differential equations.&nbsp; http://www.claymath.org/millennium/Navier-Stokes_Equations/ <br />Posted by DrRocket</DIV></p><p>&nbsp;Call it acoustics or gas dynamics. The end result is launch stress vibration and deviation from trajectory. Quoting doom from a newspaper article is like taking advice from Wallstreet investors. Best go with the people with a 40 year track record.&nbsp; Carry on Dr.</p><p>Testing<br /></p> <div class="Discussion_UserSignature"> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Call it acoustics or gas dynamics. The end result is launch stress vibration and deviation from trajectory. Quoting doom from a newspaper article is like taking advice from Wallstreet investors. Best go with the people with a 40 year track record.&nbsp; Carry on Dr.Testing <br />Posted by Testing</DIV></p><p>The acoustics at launch actually cause some concern with&nbsp;simply rattling the payload, without even having to cause a trajectory deviation.&nbsp; In that case the frequencies are probably high enough to not cause much of a trajetory problem -- until you break something.</p><p><br />The issue on Titan involved some fairly large side loads that raised a concern with over-stressing the thrust vector control actuators.&nbsp; Nothing ever broke, either because the forces realized were not big enough or because of design changes that were put in place to avoid breaking anything.&nbsp; But quantification of the gas dynamics loads defied the best computer codes that could be found.&nbsp; </p><p>This problem was not the&nbsp;result of gas dynamics, but it was the result of a fluid dynamics problem.&nbsp; And we did break something.&nbsp; The trajectory is, I think you will agree, a deviation from what you might have expected.&nbsp; It is best not to do this too often.&nbsp; </p><p><br /><img src="http://sitelife.space.com/ver1.0/Content/images/store/3/13/232b67d6-5f3d-4159-8d17-b9f0096f34c2.Medium.bmp" alt="" /><br /></p> <div class="Discussion_UserSignature"> </div>

 

[BrianSlee]

<p>Why not just get rid of the launch pad&nbsp;and the SRBs altogether. Use a Hybrid Air Vehicle instead as the launch platform and you get rid of a lot of these nasty little problems altogether and increase your payload at the same time.&nbsp; ;O)</p> <div class="Discussion_UserSignature"> <p> </p><p>"I am therefore I think" </p><p>"The only thing "I HAVE TO DO!!" is die, in everything else I have freewill" Brian P. Slee</p> </div>

 

[shuttle_guy]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Although it doesn't have to do with lift off drift, it's worth noting that the acoustic pressure wave from the Shuttle on STS-1&nbsp; was considerably more severe than had been predicted; there was actual distortion of the aft bulkead on the first flight. I believe the large water-filled bags that hang in the flame trench under the boosters were added as a result. The acoustic enviroment of the launch is extreme and analysis is not always equivalent to experience. <br />Posted by vulture4</DIV></p><p>That is correct except there was no perminate&nbsp;distortion of the&nbsp;aft&nbsp;bulkhead.</p> <div class="Discussion_UserSignature"> </div>