SRB O-ring burn-through before STS-51L?

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rocketwatcher2001

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I'm not sure if M&L is the right forum for this thread/question, but I'll give it a shot.<br /><br />I remember reading that there was a fair amount of burn-through of SRB field joints on a few launches before STS-51L, but it never went all the way through. How much burn-through have we seen on the 90+ launches since the SRB field joint redesign compared to the 25 launches with the old field joint? <div class="Discussion_UserSignature"> </div>
 
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henryhallam

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I remember reading somewhere that the new joint "completely eliminated" burn-through, but I don't have a reference and I don't remember there being any numbers associated with that statement.<br />If you find anything out, keep us informed!
 
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billslugg

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The "new joint" was the old joint plus a heater, right??? <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>
 
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drwayne

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I know an additional O-ring was added, but I forget the mechanical changes...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>
 
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rocketwatcher2001

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<font color="yellow">I know an additional O-ring was added, but I forget the mechanical changes...</font><br /><br />I also remember that there was a some extra putty used. I don't remember if it was a different kind of putty or just an extra layer. <div class="Discussion_UserSignature"> </div>
 
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tomnackid

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silylene old

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NASA formerly used Viton brand fluorocarbon o-ring with a rather high Tg. Mistake. The Tg is too high, and these become hard on cooling below -5C.<br /><br />NASA should have used Kalrez fluorocarbon o-rings (made by DuPont), which were commercially available at that time. Kalrez has a Tg of about -40C, so it would have stayed flexible even on a cold day. Also Kalrez is stable to 325C (much higher), and has excellent hot plasma resistance. Kalrez is quite expensive, whereas Viton is much cheaper.<br /><br />I recall reading an article in C&E News when NASA first chose to use Viton o-rings, and thinking this was not the best choice. I was just a lowly grad student at the time.<br /><br />I don't know what brand of o-rings were used after the joint was redesigned, and have alway wondered. Any idea? <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>
 
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MeteorWayne

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What is Tg ? <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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silylene old

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Tg is the glass transition temperature of a polymer. Below Tg, a polymer is hard and maybe even brittle; above Tg a polymer is soft and flexible and easily compressible.<br /><br />Tm is the metling point, which is an even higher temperature than Tg. Above Tm, a polymer becomes a flowable viscous liquid.<br /><br />If you plot viscosity of a polymer versus temperature, there are significant discontinuities at the Tg and the Tm.<br /><br />Here's a wiki article on the subject. (which I don't think explains it very well)<br /><br />Here's a much more clear explanation of Tg. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>
 
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MeteorWayne

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I appreciate my ongoing education <img src="/images/icons/smile.gif" /><br />I just had never run across the term in my path through science.<br /><br />Thanx for the links, my cat-like curiousity will lead me through. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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