tater Posted December 5, 2018 Share Posted December 5, 2018 True, it will be interesting since everyone was just fine with putting astronauts back on Soyuz. Also, even the flight termination system is turned off towards the terminal phase of landing, since smashing into the ocean (even at terminal velocity) is less dangerous than blowing up a rocket near the coast. As long as the trajectory is offshore, they let it ride in. Quote Link to comment Share on other sites More sharing options...
DMagic Posted December 5, 2018 Share Posted December 5, 2018 (edited) 23 minutes ago, CatastrophicFailure said: Context of how close it was: Close to the shore, but not close to the target. The landing zone is way off to the right, almost at the right edge when the rocket hits the water, I think. Also: Edited December 5, 2018 by DMagic Quote Link to comment Share on other sites More sharing options...
Mad Rocket Scientist Posted December 5, 2018 Share Posted December 5, 2018 Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted December 5, 2018 Share Posted December 5, 2018 (edited) More on board footage! Not for those prone to seasickness. [ninja’d ] Wheeeeeeeeeee! 4 minutes ago, DMagic said: Close to the shore, but not close to the target. The landing zone is way off to the right, almost at the right edge when the rocket hits the water, I think. Right, that’s the idea, so that if a failure does happen, it doesn’t take out the landing pad/droneship. Edited December 5, 2018 by CatastrophicFailure Quote Link to comment Share on other sites More sharing options...
tater Posted December 5, 2018 Share Posted December 5, 2018 Everything functioned perfectly---except the grid fin hydraulic pump. The safety systems in place (including the planned trajectory) were exactly right. Quote Link to comment Share on other sites More sharing options...
Brotoro Posted December 5, 2018 Share Posted December 5, 2018 wow. That is some impressive onboard splash-landing video. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted December 5, 2018 Share Posted December 5, 2018 Wait, engineS. Confirms was a 3 engine landing, then? Quote Link to comment Share on other sites More sharing options...
Mad Rocket Scientist Posted December 5, 2018 Share Posted December 5, 2018 It is insane how resistant the automatic landing software is if it can still land the booster under those conditions. @CatastrophicFailure I heard this was a 1 engine landing burn. I wonder if a 3 engine burn could have stabilized the roll more. Quote Link to comment Share on other sites More sharing options...
DMagic Posted December 5, 2018 Share Posted December 5, 2018 6 minutes ago, CatastrophicFailure said: Right, that’s the idea, so that if a failure does happen, it doesn’t take out the landing pad/droneship. Yeah, but I have a hard time believing that the intended abort site is relatively close to the shore, about midway between the landing zone and LC37, which is an active launch site. It seems likely that all that spinning put the rocket off course, just not off course enough, or in the wrong direction enough, to end up on land. 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: It is insane how resistant the automatic landing software is if it can still land the booster under those conditions. @CatastrophicFailure I heard this was a 1 engine landing burn. I wonder if a 3 engine burn could have stabilized the roll more. I don’t see how they could have stabilized without three engines, no way cold-gas thrusters @ sea level could arrest that much roll. Quote Link to comment Share on other sites More sharing options...
tater Posted December 5, 2018 Share Posted December 5, 2018 6 minutes ago, CatastrophicFailure said: Wait, engineS. Confirms was a 3 engine landing, then? I doubt it. Quote Link to comment Share on other sites More sharing options...
Brotoro Posted December 5, 2018 Share Posted December 5, 2018 I think it HAD to be the thrusters that stopped the roll (once the rocket slowed to the point where the force of the grid fins decreased enough). Quote Link to comment Share on other sites More sharing options...
tater Posted December 5, 2018 Share Posted December 5, 2018 2 minutes ago, CatastrophicFailure said: I don’t see how they could have stabilized without three engines, no way cold-gas thrusters @ sea level could arrest that much roll. Gimble. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted December 5, 2018 Share Posted December 5, 2018 Just now, tater said: Gimble. The center engine can’t control roll with gimbal tho. Quote Link to comment Share on other sites More sharing options...
Ultimate Steve Posted December 5, 2018 Share Posted December 5, 2018 On 12/3/2018 at 6:34 PM, CatastrophicFailure said: So after today, not landing a rocket will officially be abnormal! And then they're gonna go an do it anyway in a month with GPS-3, which isn't even that heavy.... Does this count as a landing? Because if not, it's abnormal again. Quote Link to comment Share on other sites More sharing options...
KSK Posted December 5, 2018 Share Posted December 5, 2018 2 minutes ago, tater said: Everything functioned perfectly---except the grid fin hydraulic pump. The safety systems in place (including the planned trajectory) were exactly right. Yep. A case of a video saying a thousand Twitter posts. Good move getting that out asap. Not only was it clear that the booster was never going anywhere other than over water, the system as a whole was reliable enough to completely take out that spin. Heck, the booster probably could have landed, although splashing down was absolutely the right call. It also occurs to me that SpaceX didn't get a repeat of that fuel tank problem they had on one of the early landing attempts (pre grid-fin I think?) where the cold-gas thrusters ran out of well... gas, cue spinning booster, cue centrifugal forces throwing propellants against the tank walls and starving the engine causing a crash. A very visible example of lessons learned and mistakes not repeated. Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted December 5, 2018 Share Posted December 5, 2018 1 minute ago, Ultimate Steve said: Does this count as a landing? Because if not, it's abnormal again. The $60 million question. Quote Link to comment Share on other sites More sharing options...
Mad Rocket Scientist Posted December 5, 2018 Share Posted December 5, 2018 (edited) 13 minutes ago, CatastrophicFailure said: I don’t see how they could have stabilized without three engines, no way cold-gas thrusters @ sea level could arrest that much roll. I think there are two other factors: First, the landing legs transfer quite a bit of momentum, like a figure skater. Second, as the booster slows down vertically, the gridfins stop making it spin more and start to produce a lot of drag slowing down the spin. EDIT: Moment of inertia is the word I'm looking for. EDIT2: Also, things spinning around their long axis try to move to a flat spin, IIRC. So that might have had some affect. Edited December 5, 2018 by Mad Rocket Scientist Quote Link to comment Share on other sites More sharing options...
KSK Posted December 5, 2018 Share Posted December 5, 2018 3 minutes ago, CatastrophicFailure said: The center engine can’t control roll with gimbal tho. Gas generator exhaust used for roll control I think? Witness the large gouts of sideways moving fire on Das Valdez's video. Quote Link to comment Share on other sites More sharing options...
Mad Rocket Scientist Posted December 5, 2018 Share Posted December 5, 2018 (edited) 6 minutes ago, KSK said: Gas generator exhaust used for roll control I think? Witness the large gouts of sideways moving fire on Das Valdez's video. No, they got rid of that after falcon 1. EDIT: Edited December 5, 2018 by Mad Rocket Scientist Quote Link to comment Share on other sites More sharing options...
KSK Posted December 5, 2018 Share Posted December 5, 2018 And just pinching this from the commentary over at Ars Technica. "This wasn't a water landing - it was aquabraking." Well I was amused anyway. Quote Link to comment Share on other sites More sharing options...
insert_name Posted December 5, 2018 Share Posted December 5, 2018 36 minutes ago, Mad Rocket Scientist said: hopefully it doesnt sink like govsat1's booster did Quote Link to comment Share on other sites More sharing options...
CatastrophicFailure Posted December 5, 2018 Share Posted December 5, 2018 Quote ...drifting south offshore... Well... at least this one will get washed. Wait, does salvage law apply here? That’s a nice booster they’ve got there, be a shame if someone with a faster boat... Just now, insert_name said: hopefully it doesnt sink like govsat1's booster did That one was deliberately sunk, I think. Lot of confusion around it. Quote Link to comment Share on other sites More sharing options...
sh1pman Posted December 5, 2018 Share Posted December 5, 2018 (edited) Interesting how two months ago we saw why LES is important. And today we had a good demonstration of why SpaceX aims their boosters at water before the final landing burn. ...I think I heard of a certain starship with no emergency escape system planned, doesn’t seem to be the best idea now, does it?.. Edited December 5, 2018 by sh1pman Quote Link to comment Share on other sites More sharing options...
KSK Posted December 5, 2018 Share Posted December 5, 2018 5 minutes ago, sh1pman said: Interesting how two months ago we saw why LES is important. And today we had a good demonstration of why SpaceX aims their boosters at water before the final landing burn. ...I think I heard of a certain starship with no emergency escape system planned, doesn’t seem to be the best idea now, does it?.. After watching that landing video where the engines alone were able to steer a busted rocket to a safe landing, it doesn't sound like an implausible idea. Unless Starship requires all engines burning to land (which seems unlikely), it may be able to use the other engines if anything goes wrong. Or in the argot of this particular forum, it's the 'moar boosters' approach to emergency escape systems. In other news - we have an early look at the root cause of the grid fin pump failure. "This'll teach you to pack mouldy chow..." Quote Link to comment Share on other sites More sharing options...
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