rossh@umd5.umd.edu (Hollis "NeXT-Dood" Ross) (10/17/89)
What was the results of the Rogers Commision, ie what did NASA change. I seem to recall that just another O-Ring was added. Someone mentioned (in this newsgroup) that he thought that a segmented SRB is a very bad idea. Is a non-segmented SRB actually feasible without costing 1/2 of the current defense budget? How much more expensive would it be to make a Double wall SRB and would that be too heavy?. An off the wall question: If enough fuel were available, would it be possible for the shuttle to make a journey to lunar orbit. How long can the shuttle stay up, what are the constraints for power, air, ect. Hollis Ross rossh@umd5.umd.edu /*****************************************************************************/ For a transcript of this posting, send $3 (Usenet dollars or I-Net Express only) to rossh@umd5.umd.edu or rossh@umdd (Bitnet). Taxes, tags, titles, destination charges, dealer prep and Usenet Flame Guards(C) extra. "Bo knows IBM 360 JCL"
goldader@uhccux.uhcc.hawaii.edu (Jeff Goldader) (10/18/89)
In article <5474@umd5.umd.edu> rossh@umd5.umd.edu (Hollis "NeXT-Dood" Ross) writes: >What was the results of the Rogers Commision, ie what did >NASA change. I seem to recall that just another O-Ring was >added. Well, it was more than that. The SRBs are made in segments, as you know; some of these segments are connected at the factory; in a fit of fancy, they were named "factory joints;" some are put together in the field (i.e. at KSC); they are called "field joints." The old design used a "tang and clevis" design, which was basically like this: | | | Upper segment Segment A | ^ / \ | | Tang ---> | | | |o| | |o| | Clevis ---> | Segment B | Lower segment | | | where the two O-rings were on the inner side of the tang, shown here as two small "o"s. For various reasons, although the design was supposed to ensure that at least one of the two O-rings always seated properly in its gap, the design failed. For Challenger, they failed to seat because they were so cold that they had lost sufficient resiliency (springiness) that they didn't deform correctly to fit the gap in the few milliseconds they had to do so (before the pressure of combustion deformed the booster to such an extent that proper seating was impossible). The new design helps fix this. It's called a "double tang" design: | | | Upper segment | ^ / \ | | Tang ---> | | | | |o|o| | |o| | | | | <--- Tang | | \ / Lower segment v | | | The "double tang" design helps the new third O-ring seat, even of the inner two fail to properly seat. It's supposed to be tolerant ofinstallation error and such. The basic idea is that if the pressure is so great that the joint is deformed to such an extent that the inner O-rings cannot seat, it will be great enough to *force* the outer O-ring to seat. I haven't heard of any O-ring problems since the resumption of flights; such things were very common with the old design (it was called "blow-by," at term which meant that the O-rings had not seated correctly, and hot gas was blowing by the rings) >Someone mentioned (in this newsgroup) that he thought that >a segmented SRB is a very bad idea. Is a non-segmented >SRB actually feasible without costing 1/2 of the current >defense budget? How much more expensive would it be to make >a Double wall SRB and would that be too heavy?. Well, you don't need a double wall. What you need is the ability to cast the solid fuel in a long motor. The reason they were segmented in the first place was that the technology didn't exist at the time to make a consistent grain the size of an SRB (the fuel is poured in as a very viscous fluid, and allowed to harden in the motor). I remember Aerojet (or was it Hercules?) saying that they had the know-how to cast the fuel into something the size of an SRB, but NASA didn't listen. They are using another segmented design for the Advanced SRM, rather than a single-section or (better yet) a liquid-fueled booster. Of course, the idea of a non-segmented booster is that you can't have Challenger-type joint failures.... As to expense, NASA is spending $$$ for the Advanced Solid Rocket Motor, and I don't see how the no-joint version could cost much more. I'd rather spend the money making a safe booster than replacing the next lost shuttle. > >An off the wall question: If enough fuel were available, >would it be possible for the shuttle to make a journey to >lunar orbit. How long can the shuttle stay up, what are >the constraints for power, air, ect. > Well, no. I mean, *if* you had an infinitely large fuel tank, you could, but the shuttle carries just about as much fuel as possible. No one has any good and reasonable ideas about how to get fuel into orbit, and the shuttle engines are not restartable. Currently, the limit for on-orbit time is about 10 days, with a few days just in case. I heard rumblings about modifying Columbia to have solar panels or a tank of LH2/LOX in the cargo bay so it would have power to saty in orbit for ~2-4 weeks, but I think NASA will kill that idea (it would conflict with Freedom; can't replace the $40G space station with a $300M retrofit to a 10-year-old shuttle, now, can we? :-( ) Jeff Goldader University of Hawaii uhifa.ifa.hawaii.edu Institute for Astronomy "So, Lonestar, now you see that Evil will always win- because Good is stupid." -The Dark Lord Dark Helmet, _SPACEBALLS_ Disclaimer: The opinions expressed herein are my responsibility alone. The University of Hawaii and the Institute for Astronomy neither support nor are in *any way* responsible for these opinions.
tindle@ms.uky.edu (Ken Tindle) (10/18/89)
I have heard that the SRB joint redesign has heaters and sensors to detect hot gases that would signal O-ring failure. What I wonder is: are said sensors being read by the flight computers with the control program itself able to kick off the boosters? To avoid a faulty sensor causing major trouble, I would guess that Houston would have to order any such emergency manuver. Or is it necessary to have the boosters burn out first? It might not be possible to fire the ordinance devices while under thrust, but I can't speak on that. I have a feeling someone here does know, however. :-) --------------------------\ /------------------------------------------ INTERNET:tindle@ms.uky.edu | "I heard you." -Kirk BITNET:tindle@ukma.bitnet | "He simply could not believe his ears." Ken Tindle - Lexington, KY | -Spock, The Trouble With Tribbles --------------------------/ \------------------------------------------
henry@utzoo.uucp (Henry Spencer) (10/19/89)
In article <12973@s.ms.uky.edu> tindle@ms.uky.edu (Ken Tindle) writes: >What I wonder is: are said sensors being read by the flight computers with >the control program itself able to kick off the boosters? Can't be done. There is no way to "kick off" the SRBs until they burn out. It's perhaps not theoretically impossible, but it would require considerable redesign. (For one thing, the SRBs would have to stay under some sort of control for at least a few seconds to avoid problems like having their exhaust hit the external tank, and they rely on the orbiter for control at present.) -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
henry@utzoo.uucp (Henry Spencer) (10/19/89)
In article <5474@umd5.umd.edu> rossh@umd5.umd.edu (Hollis "NeXT-Dood" Ross) writes: >What was the results of the Rogers Commision, ie what did >NASA change. I seem to recall that just another O-Ring was >added. There were a number of changes, actually. An extra flange was added to the joint to reduce flexing ("joint rotation") when the booster ignites. Another O-ring was added under that flange. The sealing putty was deleted entirely in favor of bonding the fuel in adjacent segments together. Heaters were added to keep the joints warm. I believe they did something about better weather protection to make sure that rain didn't get in and freeze. Rules for booster assembly were tightened up to ensure that proper clearances were maintained in the joints. Those are the high points that I recall. >Someone mentioned (in this newsgroup) that he thought that >a segmented SRB is a very bad idea. Is a non-segmented >SRB actually feasible without costing 1/2 of the current >defense budget? How much more expensive would it be to make >a Double wall SRB and would that be too heavy?. Double wall would add a lot of weight, I'd say. But a non-segmented SRB is quite feasible. Large non-segmented solid motors were test-fired successfully in the 60s. At least one of Thiokol's competitors, Aerojet, proposed a non-segmented replacement SRB after Challenger. One practical problem with non-segmented SRBs is that transporting them is harder, so manufacturing really needs to be near the launch site. There is also some concern about uniformity of casting in such large motors, which affects things like matching the thrust of the two SRBs (which is critical, because the shuttle can't handle too much of an imbalance). >An off the wall question: If enough fuel were available, >would it be possible for the shuttle to make a journey to >lunar orbit. How long can the shuttle stay up, what are >the constraints for power, air, ect. It would be kind of marginal with a stock orbiter, but with the changes planned to turn Columbia into an extended-duration orbiter, it would be practical if propulsion were up to it and things like navigation were sorted out. In practice it's a waste, because things like the wings are dead weight on such a trip. It's better done with a specialized vehicle. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
goldader@uhccux.uhcc.hawaii.edu (Jeff Goldader) (10/19/89)
In article <12973@s.ms.uky.edu> tindle@ms.uky.edu (Ken Tindle) writes: >I have heard that the SRB joint redesign has heaters and sensors to detect >hot gases that would signal O-ring failure. > >What I wonder is: are said sensors being read by the flight computers with >the control program itself able to kick off the boosters? Can't be done. If you try to sep the boosters before they're supposed to separate, you'd kill the shuttle with the aerodynamic stress of the separation. The system's designed to work... well... the way it's designed to work. In the same line of thought, it's impossible to separate the orbiter from the ET while the SRBs are still firing, since simulations show that the orbiter would hang up on its aft attach points, pitch down (um, towards the ground) and break up. Also, I really doubt that the orbiter could survive the SRB plumes, anyway. Jeff Goldader University of Hawaii uhifa.ifa.hawaii.edu Institute for Astronomy "So, Lonestar, now you see that Evil will always win- because Good is stupid." -The Dark Lord Dark Helmet, _SPACEBALLS_ Disclaimer: The opinions expressed herein are my responsibility alone. The University of Hawaii and the Institute for Astronomy neither support nor are in *any way* responsible for these opinions.
iiitsh@cybaswan.UUCP (Steve Hosgood) (10/23/89)
In article <1989Oct18.172311.22863@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >Can't be done. There is no way to "kick off" the SRBs until they burn out. I've been wondering about this recently. Wouldn't it be possible to design the SRB casing to have a venturi nozzle at both ends, but with the top one usually plugged by the igniter? If the igniter could be blown off the top in case of emergency, you'd be left with an SRB thrusting at both ends. The result *ought* to be that you could separate from the boosters. However, what the consequence of doing this with air rushing by at Mach N would be I have no idea. Maybe the booster would end up looking more like a ram-jet. Also, of course, if you blow the igniter off the top, you'll have to arrange for it not to hit the orbiter.. Any comments? >It's perhaps not theoretically impossible, but it would require considerable >redesign. (For one thing, the SRBs would have to stay under some sort of >control for at least a few seconds to avoid problems like having their >exhaust hit the external tank, and they rely on the orbiter for control >at present.) Couldn't they have fins fitted to give them some degree of independant steering? Steve iiitsh@pyr.swan.ac.uk
petej@phred.UUCP (Pete Jarvis) (10/24/89)
In article <1989Oct18.172311.22863@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: > >Can't be done. There is no way to "kick off" the SRBs until they burn out. Are you sure about that? What is the manual SRB sep switch for and when can it be used? I read (I forget where) that there is a quick-disconnect procedure to disconnect them early if need be. Peter Jarvis............
hogg@db.toronto.edu (John Hogg) (10/25/89)
In article <838@cybaswan.UUCP> iiitsh@cybaswan.UUCP (Steve Hosgood) writes: >Wouldn't it be possible to design >the SRB casing to have a venturi nozzle at both ends, but with the top one >usually plugged by the igniter? If the igniter could be blown off the top >in case of emergency, you'd be left with an SRB thrusting at both ends. The >result *ought* to be that you could separate from the boosters. That sounds roughly equivalent to the SRB destruct charges, except that the goal of these is simply to reduce thrust to zero by reducing chamber pressure. SRB fuel only burns effectively at high pressure. If this were a valid abort procedure, NASA would have adopted it. A small selection of problems includes avoiding debris, the reverse loading on the attachment struts when the SRB thrust suddenly becomes a drag in thick atmosphere (remember, normal SRB staging occurs at a considerable altitude) and the simple aerodynamics of separation in atmosphere. I'm sure that there are other (and probably more significant) difficulties, which somebody else can point out. >>(For one thing, the SRBs would have to stay under some sort of >>control for at least a few seconds to avoid problems like having their >>exhaust hit the external tank, and they rely on the orbiter for control >>at present.) >Couldn't they have fins fitted to give them some degree of independant >steering? While thrusting, they have independent steering via nozzle gimballing. This, of course, wouldn't apply after shutdown. However, the actual *control* circuitry is in the orbiter; the only signal that the SRBs receive independently is ``destruct''. There's no reason in principle why control packages couldn't be added. It's just that they'd have to be man-rated and salt-water-splashdown proof, and would be yet another mass penalty and source of potential failure. The same would apply to fins. Sometimes, safety in increased by leaving things out. -- John Hogg hogg@csri.utoronto.ca Department of Computer Science, University of Toronto
tneff@bfmny0.UU.NET (Tom Neff) (10/25/89)
The standard range safety approach for SRM's is to detach the nosecone so that the combustion chamber becomes an open cylinder with no net thrust. This would be dangerous to do to an assembled SRB/orbiter stack in flight. The whole thing would become an aerodynamic nightmare when the SRB thrust stopped. But separating the SRBs while still firing would be equally unpredictable and dangerous. "Forget it" would be a good summation. It would be more useful to have either liquid boosters which could be throttled down in a controlled manner, and/or a means to eject the entire crew compartment of the orbiter as a unit for separate recovery. The standard roll program orients the orbiter dorsal-down for the entire ascent, so rocket ejection of the compartment would pose difficulties. Needless to say this whole discussion is about some other orbiter, as what we have now will stay the way it is. -- Machines will never think, for "thought" ?! Tom Neff will be redefined, as often as needed, !? tneff@bfmny0.UU.NET as that which a machine cannot do. ?! ...uunet!bfmny0!tneff
henry@utzoo.uucp (Henry Spencer) (10/25/89)
In article <2816@phred.UUCP> petej@phred.UUCP (Pete Jarvis) writes: >>Can't be done. There is no way to "kick off" the SRBs until they burn out. > >Are you sure about that? What is the manual SRB sep switch for and when >can it be used? I read (I forget where) that there is a quick-disconnect >procedure to disconnect them early if need be. The quick-disconnect procedure is just a variant of the normal disconnect procedure, for use in certain cases of malfunctions in the separation process. The manual sep switches are in case the automatic separation system acts up. None of these will work until the SRBs have burnt out. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
henry@utzoo.uucp (Henry Spencer) (10/26/89)
In article <838@cybaswan.UUCP> iiitsh@cybaswan.UUCP (Steve Hosgood) writes: >>It's perhaps not theoretically impossible, but it would require considerable >>redesign. (For one thing, the SRBs would have to stay under some sort of >>control for at least a few seconds to avoid problems like having their >>exhaust hit the external tank, and they rely on the orbiter for control >>at present.) > >Couldn't they have fins fitted to give them some degree of independant >steering? The problem is not steering; they already have gimballed nozzles for that. The trouble is that they're not equipped to make their own decisions. Normally they just take orders from the orbiter. Yes, this could be fixed... at some substantial cost and probably at some weight penalty. Effort spent proposing complex redesigns of the SRBs to make them a bit more manageable is probably better spent proposing liquid-fuel boosters, which have a lot of other advantages. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
henry@utzoo.uucp (Henry Spencer) (10/26/89)
In article <1989Oct25.100345.2672@jarvis.csri.toronto.edu> hogg@db.toronto.edu (John Hogg) writes: >>Wouldn't it be possible to design >>the SRB casing to have a venturi nozzle at both ends, but with the top one >>usually plugged by the igniter? ... > >That sounds roughly equivalent to the SRB destruct charges, except that >the goal of these is simply to reduce thrust to zero by reducing >chamber pressure... A small correction: while some people have said in the past that the SRB destruct charges work by blowing off the nose of the SRBs, and this sort of procedure in fact is used in other solid motors, it is not what the shuttle SRB destruct charges use. The shuttle SRB destruct charges are linear charges in the wiring tunnel up the side of each SRB; they split the casing open lengthwise. -- A bit of tolerance is worth a | Henry Spencer at U of Toronto Zoology megabyte of flaming. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu