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#51
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Future Robotic Shuttles?
Jeff Findley wrote in
: [...} What destroyed Challenger was the design decision to use large segmented solid rocket boosters instead of liquids for the parallel staged boosters. Nor really. What destroyed Challenger was NASA's decision to ignore the engineers. Had a liquid fuel booster phisicaly collapse on the side of the ET would have caused the same scenario. It lowered design costs, but opened up the system design to the possibility of catastrophic failure due to the unique failure modes of large segmented solid rocket boosters. At least with liquids you can safely shut them down without adding complex, often pyrotechnic activated, thrust termination systems (which have their own failure modes). Assuming there would be enough time to thottle down both LRB's and the shuttle's engines in a coordinated way. A side question: if you blow the top of the SRBs while going several times the speed of sound, doesn't it still work as an engine ? Or is the pressure differential too great for air to be forced in from the top ? Columbia was also a launch failure in my book because the damage to the orbiter's TPS was caused during the launch. At the time the foam hit the wing it was probably to late to abort the launch, but probably not to late for a return to launch site abort. The root cause of the damage was foam shedding from the ET. I'd say the root cause was a wing edge that isn't up the launch environment. You can get rid of the foam and get ice instead. Foam shedding was treated like a maintenance issue but should have been treated as a safety issue all along. Foam shedding from the ET wasn't adequately addressed until after the Columbia disaster. Actually, the program to reduce shedding foam has been largely successful. Had such a program been implemented early in the shuttle program, a Columbia like failure would have been far less likely. Escape from a Columbia-like problem would have to be addressed by an escape pod and a pre-reentry decision to ditch the vehicle or at least to return empty (buran-style), and here we have more tons of "useless" items on-board. A launch escape system may not have helped the Columbia crew, since the damage went unnoticed during the launch and depending on the details a *launch* escape system may not be suitable for use during reentry. That would be a given since launch escape systems seem designed to do only one thing: get the crew capsule well away from the about-to-explode stack. On re-entry you have no stack to speak of. It's easy to say in hindsight that such a system should be designed to work during reentry, but I don't think that observation would have been obvious during the shuttle development. Adding a crew capsule to the shuttle would reduce it's already-defficient cargo capability (reinforced structures, half a ton of detonating cord and an SRB). |
#52
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Future Robotic Shuttles?
On Oct 17, 10:00*am, Jose Pina Coelho wrote:
Jeff Findley wrote : [...} What destroyed Challenger was the design decision to use large segmented solid rocket boosters instead of liquids for the parallel staged boosters. Nor really. *What destroyed Challenger was NASA's decision to ignore the engineers. *Had a liquid fuel booster phisicaly collapse on the side of the ET would have caused the same scenario. It lowered design costs, but opened up the system design to the possibility of catastrophic failure due to the unique failure modes of large segmented solid rocket boosters. *At least with liquids you can safely shut them down without adding complex, often pyrotechnic activated, thrust termination systems (which have their own failure modes). Assuming there would be enough time to thottle down both LRB's and the shuttle's engines in a coordinated way. A side question: *if you blow the top of the SRBs while going several times the speed of sound, doesn't it still work as an engine ? *Or is the pressure differential too great for air to be forced in from the top ? Columbia was also a launch failure in my book because the damage to the orbiter's TPS was caused during the launch. At the time the foam hit the wing it was probably to late to abort the launch, but probably not to late for a return to launch site abort. The root cause of the damage was foam shedding from the ET. I'd say the root cause was a wing edge that isn't up the launch environment. *You can get rid of the foam and get ice instead. Foam shedding was treated like a maintenance issue but should have been treated as a safety issue all along. *Foam shedding from the ET wasn't adequately addressed until after the Columbia disaster. *Actually, the program to reduce shedding foam has been largely successful. *Had such a program been implemented early in the shuttle program, a Columbia like failure would have been far less likely. Escape from a Columbia-like problem would have to be addressed by an escape pod and a pre-reentry decision to ditch the vehicle or at least to return empty (buran-style), and here we have more tons of "useless" items on-board. A launch escape system may not have helped the Columbia crew, since the damage went unnoticed during the launch and depending on the details a *launch* escape system may not be suitable for use during reentry. That would be a given since launch escape systems seem designed to do only one thing: get the crew capsule well away from the about-to-explode stack. *On re-entry you have no stack to speak of. It's easy to say in hindsight that such a system should be designed to work during reentry, but I don't think that observation would have been obvious during the shuttle development. Adding a crew capsule to the shuttle would reduce it's already-defficient cargo capability (reinforced structures, half a ton of detonating cord and an SRB). EXCELLENT POST! On how both losses were unavoidable......... if the challeger crew had the originally designed jettisonable crew compartment those astronauts would probably be alive today. and such a compartment may have survived the columbia break up. with no launch boost escape the shuttle should of never been man rated |
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#54
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#55
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#56
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Future Robotic Shuttles?
On 10/18/2010 07:36 AM, Jeff Findley wrote:
In , says... Jeff wrote in : Loss of vehicle can be a danger to people on the ground. Having a crewed cargo vehicle voids the "blow it up over the ocean" option. Not really. The shuttles have *always* lived with this possibility. If the shuttle stack goes out of control while the SRB's are burning, and it looks like it is becoming a danger to anyone on the ground, range safety would "push the button", which would "terminate the SRB thrust" by firing destruct charges which run the length of the SRB's. The shuttle cannot safely separate from the stack while the SRB's are burning, so this would result in loss of vehicle and crew. In other words, just because the shuttle has a crew on board, doesn't mean that it is immune from being destroyed if it endangers, so called, innocent people on the ground. This applies even after SRB sep, when the stack no longer has a flight termination system. Under the Flight Rules, the CDR and PLT "BECOME AGENTS OF THE 45 SW COMMANDER FOR PUBLIC SAFETY DURING THE PORTION OF FLIGHT AFTER SOLID ROCKET BOOSTER SEPARATION AND PRIOR TO MAIN ENGINE CUTOFF." For an imminent range safety MECO line violation during second stage, the abort request switches at the FD, FDO, and FCO consoles send commands to illuminate the ABORT light on the flight deck. The required crew response is to perform a manual MECO. So far so good (you can find these rules at the STS-107 FOIA page at: http://www.jsc.nasa.gov/news/columbia/fr_generic.pdf starting on p. 985). The part these rules leave unsaid is that the crew is expected to perform the manual MECO even if it leaves the orbiter in a known contingency abort 3-out black zone, from which survival of the orbiter down to safe bailout condition is not expected. |
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Future Robotic Shuttles?
Jeff Findley wrote in
: In article , says... Jeff Findley wrote in : [...} What destroyed Challenger was the design decision to use large segmented solid rocket boosters instead of liquids for the parallel staged boosters. Nor really. What destroyed Challenger was NASA's decision to ignore the engineers. Had a liquid fuel booster phisicaly collapse on the side of the ET would have caused the same scenario. I disagree. Burn through was more likely at lower temperatures, but o- ring erosion was found on *many* flights. It was a danger which could have destroyed a shuttle and crew even if management listened and the launched during warmer weather. The SRB field joints had several issues that needed addressed. In other words, the initial design was "not good". Yes, having hot gas pushing the o-rings away from the sealing position made my jaw drop. In fact, a lot of the CAIB report made my jaw drop. [...] It would take a heck of a lot more than that to change the crew capsule into "an escape capsule". If would be impossible to change it. It could only be designed as such from the start. Plus, this was to be a reusable vehicle with "airline like operations". Did anyone believe that one (other than a few senators, and top- management) ? Even the most optimist scenario of x number of flights per year would clearly mark it as "totaly unlike airline". Aircraft don't have escape capsules. F-111 Aardvark, but then again, with a name like that you would expect it to be different. :-), and the B-58 with individual capsules. Passenger airliners don't have parachutes for the people on board. That's because any egress solution that doesn't include 500 ejection seats will make sure that 90% of the passengers won't leave the aircraft before it hits the ground. The design philosophy here is to make sure the vehicle has intact abort modes throughout the flight envelope. |
#59
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Future Robotic Shuttles?
On Oct 21, 9:27*pm, "Jorge R. Frank" wrote:
On 10/21/2010 05:50 PM, Jose Pina Coelho wrote: Jeff *wrote in : In , says... Jeff *wrote in : [...} What destroyed Challenger was the design decision to use large segmented solid rocket boosters instead of liquids for the parallel staged boosters. Nor really. *What destroyed Challenger was NASA's decision to ignore the engineers. *Had a liquid fuel booster phisicaly collapse on the side of the ET would have caused the same scenario. I disagree. *Burn through was more likely at lower temperatures, but o- ring erosion was found on *many* flights. *It was a danger which could have destroyed a shuttle and crew even if management listened and the launched during warmer weather. *The SRB field joints had several issues that needed addressed. *In other words, the initial design was "not good". Yes, having hot gas pushing the o-rings away from the sealing position made my jaw drop. In fact, a lot of the CAIB report made my jaw drop. Umm, the CAIB report covered Columbia, not Challenger. Aircraft don't have escape capsules. F-111 Aardvark, but then again, with a name like that you would expect it to be different. :-), and the B-58 with individual capsules. They also had pretty lousy records for actually saving the crew.- Hide quoted text - - Show quoted text - well the shuttle is worse than flying in combat and most military airplanes have ejection seats. theres no escape system on commercial airliners since most accidents occur during takeoff or landing, and theres no way to get out during those times |
#60
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Future Robotic Shuttles?
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