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Space Forum / Shuttle / September 2006Is it possible to release the SRBs before they burn out?
I can see some problems with this for sure, but is there a way to release the SRBs in an emergency while they are still operating? Lee Jay Danny Dot wrote: >I can see some problems with this for sure, but is there a way to > release the SRBs in an emergency while they are still operating? The short answer is no. Separtating while burning would certainly result in recontact with the tank and loss of orbiter and crew. There is a switch and button to manually separate the SRBs if the auto system fails (e.g. SRB chamber pressure sensors). I can't remember if the switch is active during all of first stage (i.e. if the crew threw the switch and pushed the button early, would the SRBs come off?) The only viable option in first stage for a control problem is to engage the Backup Flight Software (BFS). There are NO abort modes. It the flight control system fails, the crew is dead. Danny Dot www.mobbinggonemad.org I imagine in theory it is, as they are often still burning at sep anyway, but with all that fuel still in the tank, I dare not imagine what the weird centre of gravity and loading would do. Why do you ask? Brian  SignatureBrian Gaff - briang1@blueyonder.co.uk Note:- In order to reduce spam, any email without 'Brian Gaff' in the display name may be lost. >I can see some problems with this for sure, but is there a way to > release the SRBs in an emergency while they are still operating? > > Lee Jay > I imagine in theory it is, as they are often still burning at sep anyway, > but with all that fuel still in the tank, I dare not imagine what the weird > centre of gravity and loading would do. Why do you ask? I was thinking that I had heard that you could. Obviously, once lit, there's no stopping them but I thought I had heard about an abort option to get rid of them instead of trying to shut them down like you would a liquid-fueled engine. Lee Jay Danny Dot wrote: >> I imagine in theory it is, as they are often still burning at sep anyway, >> but with all that fuel still in the tank, I dare not imagine what the [quoted text clipped - 5 lines] > option to get rid of them instead of trying to shut them down like you > would a liquid-fueled engine. There is no such abort mode. I am certain of this. Danny Dot > There is no such abort mode. I am certain of this. Fair enough. I must have been mistaken. Lee Jay Op Fri, 15 Sep 2006 18:50:41 -0700, schreef Lee Jay: >> There is no such abort mode. I am certain of this. > > Fair enough. I must have been mistaken. It reminds me of the saying: he who rides the tiger can never dismount. Nasty beasts those SRBs :o > Nasty beasts those SRBs :o In the videos, I'm always amazed at how much vibration goes away after separation. Lee Jay Even if you could be sure they would not get in the way, the aerodynamic anduneven structural loads etc, would pull the whole thing apart. Brian SignatureBrian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: briang1@blueyonder.co.uk ______________________________________________________________________________________________________________ > Danny Dot wrote: >>> I imagine in theory it is, as they are often still burning at sep [quoted text clipped - 11 lines] > > Danny Dot Well, you cannot shut them down, they are basically, big fireworks. Brian SignatureBrian Gaff....Note, this account does not accept Bcc: email. graphics are great, but the blind can't hear them Email: briang1@blueyonder.co.uk ______________________________________________________________________________________________________________ >> I imagine in theory it is, as they are often still burning at sep anyway, >> but with all that fuel still in the tank, I dare not imagine what the [quoted text clipped - 7 lines] > > Lee Jay > I can see some problems with this for sure, but is there a way to > release the SRBs in an emergency while they are still operating? Is it correct to say that explosive bolts would succesfully release the SRBs at any stage of flight ? Or are the mechanical attachements such that as long as the SRBs provide significant upwards force relative to the tank/shuttle, the "hooks" won't disengage ? (I realise that once released, the SRBs would accelerate and their exhaust would barbequeue the tank and shuttle, but from the SRB's point of view, it would be a succesful release :-) >> I can see some problems with this for sure, but is there a way to >> release the SRBs in an emergency while they are still operating? [quoted text clipped - 7 lines] > exhaust would barbequeue the tank and shuttle, but from the SRB's point > of view, it would be a succesful release :-) The range safety officer has the capability to distroy them after seperation. before they burn out to avoid having them hit populated areas. The SRB's on the Challenger were distroyed that way. SC >>> I can see some problems with this for sure, but is there a way to >>> release the SRBs in an emergency while they are still operating? [quoted text clipped - 11 lines] > seperation. before they burn out to avoid having them hit populated > areas. While true, in this particular scenario (early SRB sep), that wouldn't happen in time to save the orbiter and ET from being barbecued by the exhaust. As Danny wrote, even moreso than the exhaust, the real danger to the orbiter and the ET from an early SRB separation would be that the SRB gimbals are commanded from the orbiter. Once the SRBs separate they are out of control and re-contact with (and certain destruction of) the ET cannot be prevented. The SRB separation motors are certainly not powerful enough to overpower the SRBs if they are still generating thrust. Range safety destruct certainly could not be done in time. SignatureJRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. > The range safety officer has the capability to distroy them after > seperation. before they burn out to avoid having them hit populated areas. > > The SRB's on the Challenger were distroyed that way. For Challenger, did the SRBs *BREAK* away from the ET (perhaps bringing a small chunk of ET with them), or did they cleanly separate from the attack point ? Forgetting the exhaust issue for a second, can an SRB cleanly separate from the ET while the SRB is still generating thrust ? or would the thrust generated by SRBs end up ripping part of the ET at the attach points ? John Doe drukte met precisie uit : >> The range safety officer has the capability to distroy them after >> seperation. before they burn out to avoid having them hit populated areas. [quoted text clipped - 4 lines] > a small chunk of ET with them), or did they cleanly separate from the > attack point ? The lower strut of the SRB broke off, due to hot gasses leaking from that SRB, and moved away from the ET. This caused the tip of that SRB to pierce the upper portion of the ET, and the rest is al well known. > Forgetting the exhaust issue for a second, can an SRB cleanly separate > from the ET while the SRB is still generating thrust ? or would the > thrust generated by SRBs end up ripping part of the ET at the attach > points ? I don't think so, the power generated by the SRB, is also causing accelleration for the entire stack. If the explosive nuts and the seperation motors will work properly, I seriously doubt the clean separation will be possible, because of the forces generated by the SRB's. André Signature(\__/) ( o.O) This is Bunny. Copy and paste bunny into (")_(") your signature to help him gain world domination. >I can see some problems with this for sure, but is there a way to > release the SRBs in an emergency while they are still operating? No. Jeff Signature"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) >>I can see some problems with this for sure, but is there a way to >> release the SRBs in an emergency while they are still operating? > >No. Yes there is, "Fast Sep". Almost certainly unsurvivable, but the option is still there. Brian >>>I can see some problems with this for sure, but is there a way to >>> release the SRBs in an emergency while they are still operating? [quoted text clipped - 3 lines] > Yes there is, "Fast Sep". Almost certainly unsurvivable, but the > option is still there. Umm, not sure about this but I think Fast Sep separates the orbiter from the ET, not the SRBs. SignatureJRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. Danny Dot wrote: >>>I can see some problems with this for sure, but is there a way to >>> release the SRBs in an emergency while they are still operating? [quoted text clipped - 3 lines] > Yes there is, "Fast Sep". Almost certainly unsurvivable, but the > option is still there. Brian is correct. Fast Sep does work for all of first stage to sep the orbiter from the stack. It is considered not survivable in first stage. Danny Dot www.mobbinggonemad.org > Brian I'm sorry danny, but as long as you don't rip a wing off, you can sep from the stack any time you want to. First stage, second stage, it doesn't matter. > Fast Sep does work for all of first stage to sep the > orbiter from the stack. It is considered not survivable in first stage. Craig Fink Courtesy E-Mail Welcome @ WeBeGood@GMail.Com > I'm sorry danny, but as long as you don't rip a wing off, you can sep from > the stack any time you want to. First stage, second stage, it doesn't > matter. Okay, so maybe this is what I was remembering. So you can't ditch the SRBs from the tank but you can ditch the SRBs and tank from the orbiter, right? So now, we have two contradictory claims - it's either survivable or it's not. Anyone know for sure? Lee Jay Well what do you know (section 3): http://www.hq.nasa.gov/pao/History/rogersrep/v2appj.htm "The Space Shuttle system design contains no capability to safely accomplish a contingency abort while the SRB's are thrusting. There is no capability to physically separate the SRB's from the stack while SRB's are thrusting. Although the Orbiter can be separated from the external tank (ET) during SRB thrusting, this action is not survivable." Lee Jay Danny Dot wrote: > Well what do you know (section 3): > [quoted text clipped - 8 lines] > > Lee Jay This statement is correct. Danny Dot www.mobbinggonemad.org With SRB thrust termination, I would think it would be possible to drop them, then get off the tank. Would require a lot of work, but I would think it's possible to detect a Challenger type failure and do something about it in the 5-10 seconds from detection to failure. Personally, I like talking about the what-ifs. There have been a lot of interesting abort modes studied. One of the most interesting was one that could handle the three engine out at liftoff case. It actually made it back to the runway, three engine out RTLS. I believe loads were acceptable too, as the vehicle never got above Mach 1. But the region that this abort mode covered would have been rather small, liftoff to 10-15 seconds, and it would have driven the Range Safety Officer Crazy. SignatureCraig Fink Courtesy E-Mail Welcome @ WeBeGood@GMail.Com -- > Danny Dot wrote: > [quoted text clipped - 15 lines] > Danny Dot > www.mobbinggonemad.org Danny Dot wrote: > With SRB thrust termination, I would think it would be possible to drop > them, then get off the tank. Would require a lot of work, but I would [quoted text clipped - 9 lines] > liftoff to 10-15 seconds, and it would have driven the Range Safety > Officer Crazy. I have heard of this "mode". Apparently the deal was for 3 engines out very early, the stack is put in a big spiral where thrust is used for turning rather that to gain velocity. The end result was much lower dynamic pressure then SRB burn out in possition to make the runway. I also recall range safety didn't like this manuever at all. Danny Dot www.mobbinggonemad.org >> Danny Dot wrote: >> [quoted text clipped - 15 lines] >> Danny Dot >> www.mobbinggonemad.org Yeah, it was called the Helix maneuver, starting right above the launch pad. Can you imagine the instantaneous impact point doing larger and larger circles around the launch pad. From the Range Safety Officer's perspective, he wouldn't be able to tell which way it was going. East, North, West, South and everywhere in between. SignatureCraig Fink Courtesy E-Mail Welcome @ WeBeGood@GMail.Com -- > Danny Dot wrote: > [quoted text clipped - 17 lines] > pressure then SRB burn out in possition to make the runway. I also recall > range safety didn't like this manuever at all. > With SRB thrust termination, I would think it would be possible to drop > them, then get off the tank. Would require a lot of work, but I would > think it's possible to detect a Challenger type failure and do something > about it in the 5-10 seconds from detection to failure. Personally, I like > talking about the what-ifs. SRB thrust termination was in the original design, but when it was discovered that the shuttle's structure couldn't handle the transient forces caused by this event, the whole thing was dropped. Besides, the shuttle had a predicted loss rate of only 1 in 10,000, pre-Challenger. But that's o.k. NASA promises that the Ares I will have a similarly unbelievable predicted loss (of crew) rate. > There have been a lot of interesting abort modes studied. One of the most > interesting was one that could handle the three engine out at liftoff [quoted text clipped - 3 lines] > liftoff to 10-15 seconds, and it would have driven the Range Safety > Officer Crazy. Which is why the SRB's don't light until the SSME's are verified to be up and running properly. Jeff Signature"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) >> With SRB thrust termination, I would think it would be possible to >> drop them, then get off the tank. Would require a lot of work, but I [quoted text clipped - 10 lines] > But that's o.k. NASA promises that the Ares I will have a similarly > unbelievable predicted loss (of crew) rate. Partly due to misunderstanding - the number usually quoted is the *ascent* loss-of-crew rate only, not the *mission* loss-of-crew rate. (I agree it's still inflated.) SignatureJRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. > Partly due to misunderstanding - the number usually quoted is the *ascent* > loss-of-crew rate only, not the *mission* loss-of-crew rate. > > (I agree it's still inflated.) It's no inflated, it's just high (low, if you mean the fraction). That's because of the so-called "unknown unknowns". You can only statistically characterize that which you understand. Failure modes you don't anticipate are obviously not included in the statistical analysis. With a vehicle this complex, there must be tons of those. Lee Jay >> Partly due to misunderstanding - the number usually quoted is the >> *ascent* loss-of-crew rate only, not the *mission* loss-of-crew rate. [quoted text clipped - 6 lines] > you don't anticipate are obviously not included in the statistical > analysis. With a vehicle this complex, there must be tons of those. I agree; in fact the unknown unknowns dominate the knowns. At the top of the list is human error, which accounts for 80% of aviation accidents and there's no reason that shouldn't apply to spaceflight as well. It doesn't matter if the vehicle is good for 1:250 or 1:2500 - if the odds of human error are 1:50, the overall vehicle safety record will wind up close to 1:50. SignatureJRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. >>> Partly due to misunderstanding - the number usually quoted is the >>> *ascent* loss-of-crew rate only, not the *mission* loss-of-crew rate. [quoted text clipped - 14 lines] > of human error are 1:50, the overall vehicle safety record will wind up > close to 1:50. You guys are correct. Regardless how reliable you think you are, you need abort and escape. Danny Dot www.mobbinggonmad.org > Reply-to address spam-proofed - to reply by E-mail, > check "Organization" (I am not assimilated) and > think one step ahead of IBM. > I agree; in fact the unknown unknowns dominate the knowns. At the top of > the list is human error, which accounts for 80% of aviation accidents and > there's no reason that shouldn't apply to spaceflight as well. Yet another reason Ares isn't such a great idea. It's morphed so far beyond the initial "shuttle derived" design that it's the unknown unknowns that will get us. By comparison, the changes necessary to launch people on top of Atlas V ought to be far less dramatic, so previous flight experience with Atlas V will be more applicable to a manned Atlas V than shuttle experience will be for Ares I. > It doesn't matter if the vehicle is good for 1:250 or 1:2500 - if the odds > of human error are 1:50, the overall vehicle safety record will wind up > close to 1:50. Lots of possible human error when you're talking about a new launch vehicle design which uses only bits and pieces of the shuttle. When I read that NASA still thinks a paper Ares I design would be safer than a man rated Atlas V, it just seems that history is repeating itself. Jeff Signature"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) >> I'm sorry danny, but as long as you don't rip a wing off, you can sep >> from [quoted text clipped - 7 lines] > So now, we have two contradictory claims - it's either survivable or > it's not. It is not thought to be survivable. Here's a reference from General Dynamics. Note that lack of survivable fast separation during SRB firing was one of the arguments for replacing them with liquid rocket boosters. Executive Summary, Liquid Rocket Booster Study, Final Report http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900000821_1990000821.pdf Jeff Signature"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) > I'm sorry danny, but as long as you don't rip a wing off, you can sep from > the stack any time you want to. First stage, second stage, it doesn't > matter. Just because you can push the button at any time to do a fast sep doesn't mean you'd survive. I thought that fast sep with SRB's still firing would most likely cause the shuttle to hang up on the aft attach points, which would cause it to violently pitch up causing an extremely high angle of attack. The aerodynamic forces caused by the extremely high angle of attack at the dynamic pressures of first stage would almost surely rip the wings off as you describe. Note that Challenger was literally torn apart by aerodynamic forces during first stage. Jeff Signature"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) |
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