Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site ucla-cs.ARPA Path: utzoo!watmath!clyde!burl!ulysses!bellcore!decvax!ittatc!dcdwest!sdcsvax!sdcrdcf!ucla-cs!wales From: wales@ucla-cs.UUCP Newsgroups: net.columbia Subject: Re: How to fix? Message-ID: <8818@ucla-cs.ARPA> Date: Sat, 8-Feb-86 02:09:11 EST Article-I.D.: ucla-cs.8818 Posted: Sat Feb 8 02:09:11 1986 Date-Received: Tue, 11-Feb-86 06:25:06 EST References: <968@decwrl.DEC.COM> Reply-To: wales@ucla-cs.UUCP (Rich Wales) Distribution: net Organization: UCLA Computer Science Department Lines: 80 Some comments on dec-star!fisher's article <968@decwrl.DEC.COM>: > I would say that not only should one attempt to minimize the > possibility of this happening again, but one should also attempt > to find a way of minimizing the effect if it DOES happen. Yes. I suspect that Congress will *demand* the development of improved early-abort modes. People are simply not of a mind to accept a finding that "it could happen again, just like before, and if it does, we can't do anything but watch". > There have always been "contingency" escape modes, but I have > always heard that the chances of sucessful escape during SRB > burn are minimal. Can they be improved? Apparently it is not > considered possible to jettison the SRBs while they are still > burning. The contingency escapes I have heard involve dumping > both the ET and the SRB, and thus depriving the shuttle of > propulsion and forcing a ditch. Not only would the shuttle have to glide without power (which might or might not force a ditch, depending on altitude and velocity), but: (1) Jettisoning the SRBs while they are still live creates a strong risk that their thrust will be directed on either the shuttle or the ET. Also, since their subsequent trajectory would be uncontrollable, they might later get in the shuttle's way -- clearly with catas- trophic results. (2) Jettisoning the ET with attached live SRBs definitely creates a strong risk that -- as the shuttle peels away nose first -- its rear end will hit the ET or the SRBs. Also remember that it takes time for the shuttle to disconnect cleanly from the ET without spilling LOX and LH all over the place. And the uncontrollability of the SRBs would make it difficult to keep the SRB/ET assembly from hitting the shuttle after separation. > A "marginal" escape possibility is almost useless because very > few commanders would choose a known marginal situation over a > "possible problem" situation. Would you have pushed the button > that meant 5% chance of survival if someone had said on the > radio "hey, that right srb does not look right"? This depends on how much info you have on the abnormal situation and how quickly it can be evaluated. If Dick Scobee could have known that one of the SRBs had sprung a leak and was blowing against the ET (assuming that this is what happened, of course), I don't think he would have had too much trouble deciding whether to push the button and take that 5% chance. Whether the consequences of a "possible problem" could be pre- dicted without the benefit of 20/20 hindsight is a question in itself. > Suppose you blew off the front and back of the engines, thus > lowering the pressure and thrust, and possibly extinguishing > the fuel. Could you then jettison the SRBs and do a regulation > Return-to-launch-site abort by continuing to burn the main > engines to get into the proper energy state? I'm not familiar enough with the SRBs to know if this is feasible. You would certainly run the risk, though, that the vehicle would run into the ejected SRB nose cones. Also, without nozzles on the SRBs, the flames coming from both ends might impinge on the ET or the shuttle. I would be particularly worried about the front ends -- due to the forward velocity of the vehicle (plus air resistance), the flames coming from the front ends of the SRBs would play all over the place. > Presumably this would only work after a certain height/velocity > was reached, but it might be an improvement on current conditions. Clearly, there will *always* be a minimum initial time interval during which the crew are totally helpless because the shuttle does not yet have enough height/velocity to do anything useful without power. The question is whether this minimum interval can be reduced significantly enough below the current value of about 128 seconds to make the extra effort worth it. -- Rich Wales // UCLA Computer Science Department // +1 213-825-5683 3531 Boelter Hall // Los Angeles, California 90024 // USA ARPA: wales@LOCUS.UCLA.EDU -or- wales@UCLA-LOCUS.ARPA UUCP: ...!(ucbvax,ihnp4)!ucla-cs!wales