fisher@star.DEC (Burns Fisher ZKO1-1/D42 DTN 381-1466) (02/11/86)
There have been a number of questions and answers and speculation about the SRBs on the net lately. I would recommend the latest Aviation Week to those who wish to persue it further. (This is the 2/10/86 edition) Here are a few interesting excerpts: 1) The accident: AvWeek claims that the leak from the SRB did not burn through the ET, but rather burned through the lower attachment struts on the srb itself. This caused it the srb to pivot around the top attach point and smash into the ET, causing it to explode. They show pictures of the right SRB sailing away after the explosion with a parachute trailing out of it. They claim that this shows that the collision broke the top off the SRB allowing the 'chute to deploy. (BF speculation: this could explain the 'chute seen coming down just after the explosion). 2) Escape possibilities: NONEXISTENT durning SRB burn. This has always been known, so the SRBs were designed with much more conservative margins and redundancy than they would have been otherwise. Analysis has shown that detaching the solids while they were burning would cause unsurvivable structural loads. 3) How they burn: In general, they burn from the center out. The TOP section of the SRB has a star-shaped hole which initially gives a larger burning area than just a cylinder would. At MAX-Q, however, the "prongs" have been burned off the star, and the burning area is reduced, causing the thrust to drop. In addition, there is burning inhibitor placed on the face of the fuel at the SRB joints EXCEPT on the bottom surfaces of the two center sections. Thus the two center sections burn both from the bottom up and from the inside out. Somehow all these actions combine to increase the thrust back up after MAX-Q. Notice that this implies (to me) that the joint which apparently leaked was not covered up and protected by unburned fuel. Again, see Aviation Week for more information, and to confirm what I have condensed. Burns ....decwrl!rhea!star!fisher