Nefrums Posted January 15, 2018 Share Posted January 15, 2018 What I meant is that the launch clamps only have to deal with a 0.5 G load after ignition, compared to the 1 G load before ignition. Most of the engine thrust is countered by the rockets weight. Unless they run the static fire with partly empty tanks? Quote Link to comment Share on other sites More sharing options...
Hannu2 Posted January 15, 2018 Share Posted January 15, 2018 1 hour ago, Nefrums said: What I meant is that the launch clamps only have to deal with a 0.5 G load after ignition, compared to the 1 G load before ignition. Most of the engine thrust is countered by the rockets weight. Unless they run the static fire with partly empty tanks? The direction of force is very significant thing. I do not know exact structure of launch clamp, but I am sure that rocket's weight is on solid pieces fixed on pad before the ignition. But when engines are running, the force acts to moving parts of clamps. Quote Link to comment Share on other sites More sharing options...
sh1pman Posted January 15, 2018 Share Posted January 15, 2018 Safety panel raises concerns about Falcon 9 pressure vessel for commercial crew missions Quote WASHINGTON — An independent safety panel recommended NASA not certify SpaceX’s commercial crew system until the agency better understands the behavior of pressure vessels linked to a Falcon 9 failure in 2016. That recommendation was one of the stronger items in the annual report of the Aerospace Safety Advisory Panel (ASAP) released by NASA Jan. 11, which found that NASA was generally managing risk well on its various programs. The report devoted a section to the composite overwrapped pressure vessels (COPVs) used to store helium in the second stage propellant tanks of the Falcon 9. The investigation into the September 2016 pad explosion that destroyed a Falcon 9 while being prepared for a static-fire test concluded that liquid oxygen in the tank got trapped between the COPV overwrap and liner and then ignited through friction or other mechanisms. http://spacenews.com/safety-panel-raises-concerns-about-falcon-9-pressure-vessel-for-commercial-crew-missions/ Quote Link to comment Share on other sites More sharing options...
_Augustus_ Posted January 15, 2018 Share Posted January 15, 2018 16 minutes ago, sh1pman said: Safety panel raises concerns about Falcon 9 pressure vessel for commercial crew missions http://spacenews.com/safety-panel-raises-concerns-about-falcon-9-pressure-vessel-for-commercial-crew-missions/ ASAP is paranoid, is worried about an issue that occured over a dozen flights ago, and downright needs to go away because if it weren't for them D2 would be flying by now. Quote Link to comment Share on other sites More sharing options...
tater Posted January 15, 2018 Share Posted January 15, 2018 It's sort of amazing that this is a problem, yet they will fly crew on the never flown EUS, in a spacecraft that has never been flown before complete, on a stack that has never been flown before (SLS/Orion EM-2). Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 4 hours ago, Nefrums said: If the launch clamps are able to hold the rocket up before the engins start, they should have no problem holding it down after ignition. With a twr of 1,5 the force the launch clamps have to hold down is only half of what the have to hold up before ignition. Rarely does a mechanical system have the same strength in all directions. Also, by my numbers, FH will burn through 8.25 tonnes of fuel per second. With a 12-second static fire, that's about 100 tonnes of propellant, meaning the vehicle mass at the end of the static fire will be about 7% lower than at the start. Not a huge difference in TWR but it's nothing to sneeze at, and it's a dynamic load. 4 hours ago, KSK said: Well I would think they'd also have to cope with a pretty big dynamic load at engine start, so I wouldn't think it's a case of simply scaling up by 1.5. But yeah, as @PakledHostage pointed out, FH is hardly the most powerful launch vehicle ever built, so its not like sufficiently strong hold-downs are a new thing. They're still not something you want to take any chances with though. FH is not the most powerful launch vehicle ever built, but it is the most powerful launch vehicle ever static-fired. Quote Link to comment Share on other sites More sharing options...
Bill Phil Posted January 15, 2018 Share Posted January 15, 2018 4 minutes ago, tater said: It's sort of amazing that this is a problem, yet they will fly crew on the never flown EUS, in a spacecraft that has never been flown before complete, on a stack that has never been flown before (SLS/Orion EM-2). They've done worse. STS-1, anybody? At least here they will have a decent abort capability... Quote Link to comment Share on other sites More sharing options...
tater Posted January 15, 2018 Share Posted January 15, 2018 Assuming that the D2 tested so far, and that will be tested at max q abort is really a sort of boilerplate, and not a flight article, SpaceX should do another, voluntary test, IMHO. They have boosters to throw away, this test would cost a stage 2. They'd set off the range control pyros on stage 2 once safely downrange while S1 is still burning, and see if LES works, and would save crew. If that is not a LOC incident in terms of the forces on the capsule, then chances of a LOC incident are pretty slim. Reentry should be safe with a capsule, the next failure modes are what? Total loss of RCS so they could not abort from orbit or dock? Chute failure? Quote Link to comment Share on other sites More sharing options...
IncongruousGoat Posted January 15, 2018 Share Posted January 15, 2018 13 minutes ago, tater said: It's sort of amazing that this is a problem, yet they will fly crew on the never flown EUS, in a spacecraft that has never been flown before complete, on a stack that has never been flown before (SLS/Orion EM-2). I think the rationale is that COPV-related failure can cause the LV to blow up on the pad without warning or time for the LES to fire. Furthermore, the AMOS-6 incident occurred for a very bizarre reason, and couldn't have reasonably been predicted by anybody. Therein lies the problem- the failure modes for a COPV are poorly understood, and as such it can cause unprecedented problems. It's also been the cause, direct or indirect, of the only two catastrophic F9 failures. It's not that hard to see why they don't trust the rocket, especially when you add a healthy does of distrust/downright dislike of SpaceX compared to traditional launch providers. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 (edited) 9 minutes ago, tater said: Assuming that the D2 tested so far, and that will be tested at max q abort is really a sort of boilerplate, and not a flight article, SpaceX should do another, voluntary test, IMHO. They have boosters to throw away, this test would cost a stage 2. They'd set off the range control pyros on stage 2 once safely downrange while S1 is still burning, and see if LES works, and would save crew. If that is not a LOC incident in terms of the forces on the capsule, then chances of a LOC incident are pretty slim. Reentry should be safe with a capsule, the next failure modes are what? Total loss of RCS so they could not abort from orbit or dock? Chute failure? IIRC, this would be no different than CRS-7, and we already know that the Dragon survived, without LOC-level forces, even without an LAS. It would have been recovered if the chutes had been programmed to deploy. 6 minutes ago, IncongruousGoat said: I think the rationale is that COPV-related failure can cause the LV to blow up on the pad without warning or time for the LES to fire. Furthermore, the AMOS-6 incident occurred for a very bizarre reason, and couldn't have reasonably been predicted by anybody. Therein lies the problem- the failure modes for a COPV are poorly understood, and as such it can cause unprecedented problems. It's also been the cause, direct or indirect, of the only two catastrophic F9 failures. It's not that hard to see why they don't trust the rocket, especially when you add a healthy does of distrust/downright dislike of SpaceX compared to traditional launch providers. Dragon 2 has already shown 0-0 pad abort at a speed which would have protected the crew in an AMOS-6 situation. Edited January 15, 2018 by sevenperforce Quote Link to comment Share on other sites More sharing options...
tater Posted January 15, 2018 Share Posted January 15, 2018 Quote Link to comment Share on other sites More sharing options...
IncongruousGoat Posted January 15, 2018 Share Posted January 15, 2018 Just now, sevenperforce said: IIRC, this would be no different than CRS-7, and we already know that the Dragon survived, without LOC-level forces, even without an LAS. It would have been recovered if the chutes had been programmed to deploy. Dragon 2 has already shown 0-0 pad abort at a speed which would have protected the crew in an AMOS-6 situation. The question is not whether Dragon could have escaped in enough time. It's whether the abort button could have been pushed in time. The AMOS-6 failure happened almost instantly. Single-stage-to-explosion, as it were. This may very well be the case, but when the investigators are A: paranoid dinosaurs, and B: in the "SpaceX-could-never-ever-be-trustworthy" camp... I'm not saying it makes sense. I'm just trying to clarify the rationale behind the investigation, beyond simply attributing it to bias on the part of the investigators. If SpaceX were truly perfect there wouldn't be anything to investigate. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 3 minutes ago, IncongruousGoat said: The question is not whether Dragon could have escaped in enough time. It's whether the abort button could have been pushed in time. The AMOS-6 failure happened almost instantly. Single-stage-to-explosion, as it were. This may very well be the case, but when the investigators are A: paranoid dinosaurs, and B: in the "SpaceX-could-never-ever-be-trustworthy" camp... I'm not saying it makes sense. I'm just trying to clarify the rationale behind the investigation, beyond simply attributing it to bias on the part of the investigators. If SpaceX were truly perfect there wouldn't be anything to investigate. That's a fair enough assessment. Prior to AMOS-6, what was the planned sequence for Commercial Crew? Fuel loading, ingress, launch seq? Or ingress, fuel loading, launch seq? In the former case, it could conceivably have been possible to have a pad explosion due to COPV failure during ingress, which would have been LOCV. In the latter case, the only mechanism for LOCV would have been if the Dragon 2's LAS and automated triggering sequence was not activated during fuel loading, which seems ridiculously unlikely. Quote Link to comment Share on other sites More sharing options...
sh1pman Posted January 15, 2018 Share Posted January 15, 2018 1 minute ago, IncongruousGoat said: The question is not whether Dragon could have escaped in enough time. It's whether the abort button could have been pushed in time. The AMOS-6 failure happened almost instantly. Single-stage-to-explosion, as it were. This may very well be the case, but when the investigators are A: paranoid dinosaurs, and B: in the "SpaceX-could-never-ever-be-trustworthy" camp... I'm not saying it makes sense. I'm just trying to clarify the rationale behind the investigation, beyond simply attributing it to bias on the part of the investigators. If SpaceX were truly perfect there wouldn't be anything to investigate. Maybe it would be an automated abort command that, once the crew is onboard, can be triggered immediately if any kind of anomaly is detected. Quote Link to comment Share on other sites More sharing options...
IncongruousGoat Posted January 15, 2018 Share Posted January 15, 2018 Just now, sh1pman said: Maybe it would be an automated abort command that, once the crew is onboard, can be triggered immediately if any kind of anomaly is detected. Define "anomaly". What qualifies as conditions for an abort? On the one hand, nobody wants to risk the crew. On the other, nobody wants to throw a perfectly good booster out for a false abort; those things are expensive. It's not impossible, per se, to set up such a thing, but it's very much a case of "easier said than done". Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 4 minutes ago, IncongruousGoat said: Define "anomaly". What qualifies as conditions for an abort? On the one hand, nobody wants to risk the crew. On the other, nobody wants to throw a perfectly good booster out for a false abort; those things are expensive. It's not impossible, per se, to set up such a thing, but it's very much a case of "easier said than done". No fuel loading before ingress. After ingress, abort engines are on a hairtrigger. Any measurable acceleration prior to launch is an abort. Any unplanned pressure excursion is an abort. Also...not sure about this, but I doubt that a false abort would necessarily destroy the booster. The New Shepard survived capsule abort at Max-Q, and that pusher solid is far nastier to a rocket stage than the canted SuperDracos. Quote Link to comment Share on other sites More sharing options...
IncongruousGoat Posted January 15, 2018 Share Posted January 15, 2018 3 minutes ago, sevenperforce said: No fuel loading before ingress. After ingress, abort engines are on a hairtrigger. Any measurable acceleration prior to launch is an abort. Any unplanned pressure excursion is an abort. I was more leaning to in-launch abort, where failure modes are much more varied. Is engine failure cause for abort? Maybe, depending on how many engines and when in the flight they fail. Is higher than usual pressure cause for abort? Maybe, or it might just be a normal fluctuation in tank pressure. Is high aerodynamic shear cause for abort? Maybe, or it might just be windy that day. The point is, it's harder to quantify what qualifies as an abort, especially for a vehicle with redundancies like F9. Quote Link to comment Share on other sites More sharing options...
sh1pman Posted January 15, 2018 Share Posted January 15, 2018 1 minute ago, IncongruousGoat said: Define "anomaly". What qualifies as conditions for an abort? On the one hand, nobody wants to risk the crew. On the other, nobody wants to throw a perfectly good booster out for a false abort; those things are expensive. It's not impossible, per se, to set up such a thing, but it's very much a case of "easier said than done". I'm not saying it's easy, just that it would probably be automated. Exact conditions for LAS can be optimised to trigger only if something really bad happened, like sudden drop or increase in tank pressure, vibration or acceleration of D2 capsule, something like that. Quote Link to comment Share on other sites More sharing options...
tater Posted January 15, 2018 Share Posted January 15, 2018 No one pushes a button, the system has to detect the failure and act itself I assume. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 2 minutes ago, IncongruousGoat said: I was more leaning to in-launch abort, where failure modes are much more varied. Is engine failure cause for abort? Maybe, depending on how many engines and when in the flight they fail. Is higher than usual pressure cause for abort? Maybe, or it might just be a normal fluctuation in tank pressure. Is high aerodynamic shear cause for abort? Maybe, or it might just be windy that day. The point is, it's harder to quantify what qualifies as an abort, especially for a vehicle with redundancies like F9. Midflight abort is far less dangerous than pad abort. Most failure modes don't even need LAS, only separation, since the Dragon 2's trunk gives it passive stability. As I pointed out before, CRS-7 was virtually worst-case-scenario for an inflight abort, and the Dragon 1 survived without LAS. Quote Link to comment Share on other sites More sharing options...
tater Posted January 15, 2018 Share Posted January 15, 2018 Just now, sevenperforce said: Midflight abort is far less dangerous than pad abort. Most failure modes don't even need LAS, only separation, since the Dragon 2's trunk gives it passive stability. As I pointed out before, CRS-7 was virtually worst-case-scenario for an inflight abort, and the Dragon 1 survived without LAS. I assumed this was the case, but was unsure of the forces on the capsule. I think the principal issue would have been tumbling, had that happened during that flight. Assuming it instantly stabilizes in pretty much any direction of flight, the forces should be quite manageable. Quote Link to comment Share on other sites More sharing options...
Bill Phil Posted January 15, 2018 Share Posted January 15, 2018 (edited) 5 minutes ago, tater said: No one pushes a button, the system has to detect the failure and act itself I assume. What's worse is false positives in the error detection. Imagine a vert expensive mission wasted for no reason... Edited January 15, 2018 by Bill Phil Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 3 minutes ago, tater said: I assumed this was the case, but was unsure of the forces on the capsule. I think the principal issue would have been tumbling, had that happened during that flight. Assuming it instantly stabilizes in pretty much any direction of flight, the forces should be quite manageable. Yes, the Dragon 1 may have tumbled; I don't know. But the Dragon 2's trunk fins and forward CoM make it untumbleable until trunk separation. When you're dealing with liquids rather than solids, the purpose of LAS during flight is not so much to get clear of an explosion, but to get clear of debris or structural collision. You'd hate to survive a S2 breakup, only to be rammed by the business end of the still-firing first stage by some freak chance. 3 minutes ago, Bill Phil said: What's worse is false positives in the error detection. Imagine a vert expensive mission wasted for no reason... "Wasted" is relative. Sure, Dragon 2 loses whatever is in the trunk during a pad abort, but the booster isn't necessarily shredded. In flight it is a little dicier, but in flight you have a less demanding reaction window. Quote Link to comment Share on other sites More sharing options...
tater Posted January 15, 2018 Share Posted January 15, 2018 4 minutes ago, WildLynx said: There is standard method for abort triggering: the break wires. They run alongside entire rocket, and if 2 of 10 is broken, it's abort. Of course, they are separate for 1st and 2nd stages, so corresponding abort modes are disabled before staging. P.S. That on-pad accident would for sure break all 10 in stage 2, so it would caused abort even before we seen an expanding cloud. Out of likes, but this would have gotten one Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted January 15, 2018 Share Posted January 15, 2018 2 minutes ago, tater said: 7 minutes ago, WildLynx said: There is standard method for abort triggering: the break wires. They run alongside entire rocket, and if 2 of 10 is broken, it's abort. Of course, they are separate for 1st and 2nd stages, so corresponding abort modes are disabled before staging. P.S. That on-pad accident would for sure break all 10 in stage 2, so it would caused abort even before we seen an expanding cloud. Out of likes, but this would have gotten one Ditto this. I have been out of likes all morning. Quote Link to comment Share on other sites More sharing options...
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