sevenperforce Posted December 5, 2018 Share Posted December 5, 2018 5 minutes ago, Nightfury said: And it looked like the problem was only regarding landing phase, so maybe not even a problem for normal launches Yeah, grid fins are intentionally not used for any aspect of launch. Quote Link to comment Share on other sites More sharing options...
tater Posted December 5, 2018 Share Posted December 5, 2018 This performed as designed. RTLS is specifically placed in an offshore trajectory for this contingency to ensure safety ashore, then steered to the pads at the last minute. This was entirely a landing failure. A % of boosters are assumed to be lost, landing them is always a secondary goal to placing the payload where it belongs. This will also result in an iterative improvement to the hydraulic pumps, I'd wager. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted December 5, 2018 Share Posted December 5, 2018 21 minutes ago, tater said: The baseline trajectory is set such that it then has to fly to land, the default is in the water as I understand it, so if there is a failure (like today) it hits water. They didn't realize it was coming down over water at all. Quote Link to comment Share on other sites More sharing options...
Nightfury Posted December 5, 2018 Share Posted December 5, 2018 (edited) 5 minutes ago, sevenperforce said: Then again, it WOULD have landed safely, had it come down on the pad. Maybe a touch hard, but it would have managed Hm, would the S1 have managed the transition from a water trajectory to the one to the pad if it spins? Can the engines counteract it effectivly ? Single Engine burn, so no roll control Edited December 5, 2018 by Nightfury Quote Link to comment Share on other sites More sharing options...
Ultimate Steve Posted December 5, 2018 Share Posted December 5, 2018 Quote Link to comment Share on other sites More sharing options...
tater Posted December 5, 2018 Share Posted December 5, 2018 No. From that angle they cannot tell. It landed just offshore the pads. Quote Link to comment Share on other sites More sharing options...
KSK Posted December 5, 2018 Share Posted December 5, 2018 14 minutes ago, CatastrophicFailure said: That's a bit dire from a single, as yet un-diagnosed issue. They mentioned in the feed, that was just ice coming off, nothing that hasn't happened before. I hate to draw the obvious parallel here... Although if Elon's initial reaction is correct, I admit that I'm not seeing an obvious link between a stalled hydraulic pump and ice clipping the grid fin. And that landing was impressively controlled all things considered. If that had been a returning crew vessel, I'm thinking it may even have been survivable, presuming the crew could egress with haste once it hit the water. I don't think that either Crew Dragon or Starship intended / intend to use grid fins for landing though. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted December 5, 2018 Share Posted December 5, 2018 14 minutes ago, Nightfury said: Hm, would the S1 have managed the transition from a water trajectory to the one to the pad if it spins? Can the engines counteract it effectivly ? Single Engine burn, so no roll control I'm not saying they shouldn't have aborted the transition in this case; I'm just saying that the water landing itself was stable enough to have remained upright if it landed on a flat surface. Quote Link to comment Share on other sites More sharing options...
Nightfury Posted December 5, 2018 Share Posted December 5, 2018 1 minute ago, KSK said: And that landing was impressively controlled all things considered. Pretty good programming with adaptability(?) Quote Link to comment Share on other sites More sharing options...
Jaff Posted December 5, 2018 Share Posted December 5, 2018 Just now, sevenperforce said: I'm not saying they shouldn't have aborted the transition in this case; I'm just saying that the water landing itself was stable enough to have remained upright if it landed on a flat surface. The computer has to make the decision to ditch or not to ditch at some point though. untill halfway through that landing burn it was still essentially out of control doing its own little pirouette Quote Link to comment Share on other sites More sharing options...
KSK Posted December 5, 2018 Share Posted December 5, 2018 (edited) 13 minutes ago, Ultimate Steve said: Ouch. I get what he's saying - as @tater pointed out, the failsafe mode for landing is exactly what just happened, so I can understand the lack of a backup pump, but I'm a bit worried about how that might go down in a certain, recently announced review. Something considered ground safety critical doesn't get a backup system...I can see that being jumped all over. Edited December 5, 2018 by KSK Quote Link to comment Share on other sites More sharing options...
Mad Rocket Scientist Posted December 5, 2018 Share Posted December 5, 2018 I think it's unfair to say that this failure is the difference between propulsive landing being safe or not for crews, since the falcon 9 already has a terrible safe landing rate. This one is far less dire for safety of propulsive landings than any of the previous landings where the rocket simply completely failed to land and blew up. Quote Link to comment Share on other sites More sharing options...
Delay Posted December 5, 2018 Share Posted December 5, 2018 (edited) 4 minutes ago, Mad Rocket Scientist said: since the falcon 9 already has a terrible safe landing rate. What? Might be confirmation bias, but I'm pretty sure that SpaceX had more successful landings than failed ones. By far. What I'm more worried about right now is the media & their reaction. If CNN found it newsworthy enough to make an article about a "million dollar nose cone" not being retrieved, what is the reaction going to be here? "Multimillion dollar rocket crashed into water"? Edited December 5, 2018 by Delay Quote Link to comment Share on other sites More sharing options...
tater Posted December 5, 2018 Share Posted December 5, 2018 1 minute ago, KSK said: Ouch. I get what he's saying - as @tater pointed out, the failsafe mode for landing is exactly what just happened, so I can understand the lack of a backup pump, but I'm a bit worried about how that might go down in a certain, recently announced review. Something considered ground safety critical doesn't get a backup system...I can see that being jumped all over. Twitter is hardly the place for lengthy discourse. I think ground safety is not critical in landing because the trajectory is intentionally offshore. A failure of entry burn? Crash in ocean. A failure of grid fins? Ocean. A failure of terminal landing burn? That starts moving from offshore to damaging the pad (but already in the pad area, which is a "safe" place to crash on land, else it would be in the water). The engine systems are mission critical, and hence already have redundancies. Just now, Delay said: What? They crashed many times learning how to land, and a couple after learning (FH, and one other, I think). So out of 65 launches, and maybe 40-something landing attempts, they have landed 32. Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted December 5, 2018 Share Posted December 5, 2018 10 minutes ago, Jaff said: The computer has to make the decision to ditch or not to ditch at some point though. Yes, and the computer absolutely made the correct choice. No question there. Also, as others have pointed out, engine gimbal was enough to correct the bad pitch and yaw, but it might not have been enough to perform the translation necessary to get over to the ground pad. My point is that even with a critical systems failure in the control fins, the vehicle still landed intact. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted December 5, 2018 Share Posted December 5, 2018 Context of how close it was: Quote Link to comment Share on other sites More sharing options...
sevenperforce Posted December 5, 2018 Share Posted December 5, 2018 7 minutes ago, tater said: I think ground safety is not critical in landing because the trajectory is intentionally offshore. A failure of entry burn? Crash in ocean. A failure of grid fins? Ocean. A failure of terminal landing burn? That starts moving from offshore to damaging the pad (but already in the pad area, which is a "safe" place to crash on land, else it would be in the water). The engine systems are mission critical, and hence already have redundancies. And you'd have to have "failure of terminal landing burn during burn sequence" to endanger the landing pad. If an engine just craps out mid-burn, then yeah, that's a problem, but that is the definition of failure for every rocket ever. Quote Link to comment Share on other sites More sharing options...
Mad Rocket Scientist Posted December 5, 2018 Share Posted December 5, 2018 3 minutes ago, Delay said: What? Might be confirmation bias, but I'm pretty sure that SpaceX had more successful landings than failed ones. By far. [...] I meant from a potential crew safety standpoint. I think the current rate is 84.21%. Terrible was too strong a word, but definitely far from human-rated. Quote Link to comment Share on other sites More sharing options...
Delay Posted December 5, 2018 Share Posted December 5, 2018 2 minutes ago, sevenperforce said: If an engine just craps out mid-burn, then yeah, that's a problem, but that is the definition of failure for every rocket ever. What about the engine not shutting down after an otherwise successful landing? Quote Link to comment Share on other sites More sharing options...
tater Posted December 5, 2018 Share Posted December 5, 2018 1 minute ago, sevenperforce said: And you'd have to have "failure of terminal landing burn during burn sequence" to endanger the landing pad. If an engine just craps out mid-burn, then yeah, that's a problem, but that is the definition of failure for every rocket ever. Yeah, exactly. Also, on landing, there is not much there except plastic and metal. The ASDS crashes were spectacular, but the ship came back to port, often with most of a booster lying there. 1 minute ago, Mad Rocket Scientist said: I meant from a potential crew safety standpoint. I think the current rate is 84.21%. Terrible was too strong a word, but definitely far from human-rated. Yeah, point to point is a very long pole (propulsive landing with people), indeed. Quote Link to comment Share on other sites More sharing options...
Nightfury Posted December 5, 2018 Share Posted December 5, 2018 1 minute ago, Delay said: What about the engine not shutting down after an otherwise successful landing? Depends on how much fuel is left. If there is like nothing, it makes a short hop and then burns out. If there is to much, well, going to water I guess Quote Link to comment Share on other sites More sharing options...
Delay Posted December 5, 2018 Share Posted December 5, 2018 (edited) 4 minutes ago, Mad Rocket Scientist said: I think the current rate is 84.21%. Sure, but keep in mind that, as of now, SpaceX is the only company to even try and land their first stages back on the ground. For that, and the fact that they developed this technology from the ground up, a non-0% success rate is even more remarkable. Yes. 84.21% is probably not good enough for human rating. But it is not terrible, especially as it is a first in the space industry. Edited December 5, 2018 by Delay Sentence made no sense. Quote Link to comment Share on other sites More sharing options...
KSK Posted December 5, 2018 Share Posted December 5, 2018 6 minutes ago, tater said: Twitter is hardly the place for lengthy discourse. I think ground safety is not critical in landing because the trajectory is intentionally offshore. A failure of entry burn? Crash in ocean. A failure of grid fins? Ocean. A failure of terminal landing burn? That starts moving from offshore to damaging the pad (but already in the pad area, which is a "safe" place to crash on land, else it would be in the water). The engine systems are mission critical, and hence already have redundancies. All true and understood. It's more the perception I'm worried about - especially on Twitter which, as you say, isn't the best medium for more detailed explanations. Quote Link to comment Share on other sites More sharing options...
Mad Rocket Scientist Posted December 5, 2018 Share Posted December 5, 2018 2 minutes ago, Delay said: Sure, but keep in mind that, as of now, SpaceX is the only company to even try and land their first stages back on the ground. For that, and the fact that they developed this technology from the ground up, a non-0% success rate is even more remarkable. Yes. 84.21% is probably not good enough for human rating. But it is not terrible, especially as it is a first in the space industry. I completely agree. And I think that it is possible to make propulsive landing much safer, but I brought it up because I don't think this is a particularly bad sign for propulsive landing. After all, this was a failure of a system without any kind of backup or failsafe, something that just won't exist on a human-rated spacecraft. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted December 5, 2018 Share Posted December 5, 2018 1 minute ago, Mad Rocket Scientist said: After all, this was a failure of a system without any kind of backup or failsafe, And it sounds like it will now. Oy, what a morning! Quote Link to comment Share on other sites More sharing options...
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