fisher@star.DEC (Burns Fisher ZKO1-1/D42 DTN 381-1466) (02/07/86)
>>BTW, did the Russians run out of craters on Venus or what? Surely they >>could find 5 more to name after the men abord the shuttle. I like the >>idea of naming 7 of the newly discovered moons of Uranus after the >>astronauts. >> >> >> Don Nash >> > >This occurred to me also, but it turns out that they have named the other >craters on Venus for Soviet women. Thus naming only after Christa and Judy >is consistent, and I would say, very thoughtful. I appreciate that sort >of gesture. > >Burns Sorry...I mispoke. The craters are not necessarily being named after SOVIET women. They are just being named after women in the tradition established by the planet name Venus. -------------------------- About a previous near-burnthrough on the SRBs: Yes, there was a (or some?) close calls. The NOZZLE nearly burned through. The problem was found to be something improper done in forming them so they ablated faster than they were supposed to. That is fixed, and appears not to be relavent to the disaster, since the current problem appears to have happened up higher. -------------------------- And now to the subject of this note: What can be done? Let us make some assumptions and start a discussion. Assumptions: 1) The explosion was caused by hot gasses coming through a hole in the right srb and blowing the ET. 2) The hole was detectable something like 13 seconds before the explosion. 3) The cause of the hole will be found and fixed without MAJOR redesign. 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. Therefore, I would like to discuss the possibility of escape if this ever happens again. 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. Further assumptions: 4. You can't dump the SRBs while they are burning because of the 3million pounds of thrust. 5. 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"? 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? Presumably this would only work after a certain height/velocity was reached, but it might be an improvement on current conditions. Burns ...decwrl!rhea!star!fisher
wales@ucla-cs.UUCP (02/08/86)
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