SpaceX Falcon 9 historic landing thread (1st landing attempt & most recent missions)

Onebadhawk
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BEC said:
....and (to return to topic) a Falcon 9 this morning landed for the seventh time after lofting a satellite for Sirius XM. Even though it's almost routine now, it is still really cool.
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It’s amazing to me that they’ve flown some of these boosters 7 times already. I think they have used some of the older ones for their own starlink missions, but this was for a paying customer. I wonder what the discount is if you agree to use a recovered booster instead of a new one.
 
Regarding the Starship test flight's powered climb, An interesting observation I have read elsewhere, which makes total sense now. Almost everyone expected for it to climb like a normal launch vehicle, to pitch diagonally to go towards the downrange area it was supposed to get to for apogee. It was expected it would use all three engines, cut off, and COAST the rest of the way.

But as we all saw, it pointed nearly vertically the whole time, shut down one engine, then shut down a second engine, and ended up flying more horizontally than vertically on the single engine, still pointing itself mostly vertical. What I have read as speculation, which makes total sense, as to why they did it that way.

Because it is not aerodynamically stable in yaw, and also those "flaps" in the pitch axis are incapable of controlling pitch in forward (straight ahead) flight (they are hinged to fold and unfold parallel to the body, not rotate in pitch). It could never coast straight, it would randomly flip around.

So, it HAD to be using vectored thrust the whole time, until reaching apogee and reaching the GPS location over the water where the belly flop maneuver was supposed to begin.

A video below, shot from at least 8 miles away, on South Padre Island looking south. A poor view overall (crash not visible), except that due to the venting you can see the white trails that shows the actual flight path pretty nicely. Especially the horizontal motion, while SN8 was pointed mostly vertical.



BTW - SN9 fell over due to the stand it was on collapsing. Very troubling that could happen, at all. It's upright now.

It has some dents to the body, though those might all be above the tank section. Also damage to a tail fin/flap, and to a forward flap. Not known if the flap hinge areas were structurally damaged, or if any parts of the tail section were structurally damaged
 
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georgegassaway said:
BTW - SN9 fell over due to the stand it was on collapsing. Very troubling that could happen, at all. It's upright now.

It has some dents to the body, though those might all be above the tank section. Also damage to a tail fin/flap, and to a forward flap. Not known if the flap hinge areas were structurally damaged, or if any parts of the tail section were structurally damaged
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Yeah, that's definitely Not Good. The stands are the easiest things to design, and since they don't fly, they're easy to design with lots of extra strength.

If it's not in a tank, 304L* is pretty easy to beat the dents out of. Certainly you could get close enough to be able to fly if the nosecone isn't pressurized. If it is in a tank, then there's probably more work. Rather than cutting out and re-welding, it might be worth just going to the pressure test and seeing if the dent pops out.

* At least normal 304L. I think this has a slightly special sauce in addition to the normal formula.
 
Analyze the crap out of it and fly it as-is. Gather data on flying a damaged ship.

Someday we may be trying to get off the surface in a damaged ship. It could totally happen. Call this an opportunity. Not to mention it's the cheapest way forward.
 
I could be wrong. Once in the high-bay, it is normally on it's legs and no longer on a stand. Most people confuse the legs that retract/extend inside the skirt for a stand.
 
The legs is a bigger deal than a stand for sure. If the legs can't handle just sitting still with whatever additional pressure the wind may put on it they definitely shouldn't work for a landing. A stand may have been faulty because an engineer put a decimal in the wrong place and the person that was supposed to check over the work failed to find the error. No big deal, just build a thicker one.
 
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Caleb beat me to posting the Teslarati article. The running theory there based on photos is that the jacks holding up the stand weren't bolted to the floor, so it was able to topple over when the rocket got bumped or hit with wind. If that's the case, just bolting the jacks/legs to a ring that sits on the floor would probably do the job while still being moveable.

The jacks-not-bolted-to-the-floor failure mechanism is pretty plausible, though it would also be pretty disappointing from an engineering design perspective. My CivE structure labs in college had a couple of projects where teams that considered those loads had their stuff work and teams who didn't didn't. Most of us learned then to take those loads into account.
 
Mushtang said:
The legs is a bigger deal that a stand for sure. If the legs can't handle just sitting still with whatever additional pressure the wind may put on it they definitely shouldn't work for a landing. A stand may have been faulty because an engineer put a decimal in the wrong place and the person that was supposed to check over the work failed to find the error. No big deal, just build a thicker one.
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Sitting on top of the stand, they build the Starship base structure, and add to it. The landing legs are among the things added to it during assembly. It also means they can test and modify and repair and replace landing leg parts and related systems at all times and test one more time afterwards to be sure it's al working. Can't do that if it is sitting on the legs.

I really was surprised to see that it's mostly just "sitting" on top of a stand with a circular ring on top. Like....where the h*ll are any diagonal braces? Although if it had rotated due to lack of diagonal bracing, that would have been seen in the LabPadre "always on" video that showed it tip over.

It WAS pretty windy that day. Though the wind was not directly towards that slim doorway, the wind currents would go past it and the wind direction that day seemed to be in a direction that would have been pushing it into the direction it fell towards. Which brings up a Chicken or the Egg question of whether the stand "just failed" out of the blue (or some very dumb ground crew mistake), or the wind caused SN-9 to tip and then the stand failed as a result (or combo of both).

BocaChicaGal (Mary) shot footage starting from before it tipped over, and showing after. At 2:07 you can see how windy by a big tent with a gash in it (I read they may have cut the canvas on purpose to remove it, not sure of the validity of that). Footage of SN8 debris during clean-up. At 5:36, a clip showing SN9 leaning. Also the edge of a tree showing how windy it was shortly after. Also the wind seemed to be from left to right, while not entering that doorway directly, some of it would wrap "around" the building and likely enter that doorway.


Gotta figure it HAS to be bolted down (or clamped down) when on the pad, due to wind blowing it over otherwise. So this begs the question of whether it may not have been bolted or clamped down inside the high bay (unless it really was 100% stand failure as in collapse on one side). Because a windproof building is not a windproof building when you have a massive opening in it with no door to keep the wind out.

Something new......even though from the flight 7 days ago. Edited high-quality footage of the flight last week. No commentary, and engine audio synced-up, no time delay. Some VERY nice close-up views from camera #4, you can see the nozzles and exhaust very well even at over 40,000 feet.

 
rklapp said:
Also it didn’t appear that the landing legs engaged before it crashed. Any explanation for this?
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I’ve always had the impression that a lot of the navigation and flight events are done by where it -should- be, rather than measuring where it actually is. Though I figure they have a better system than Joe Barnard - IMU updated by GPS at about 1Hz. Anyway, they don’t have radar/lidar, do they. The discussion has always been - the landing barge is placed under the rocket, not the other way around.
If so, then the leg deploy may have been timed for so many seconds after landing burn started - and it hit before the timing elapsed.
 
I forgot about this morning's mission until a few minutes ago, and thankfully I didn't miss it. I like seeing the boosters return to launch site to land on land. There must have been a delay, the clock is stopped at T-45 minutes.

 
Apparently there was a problem with the second stage LOX pressure sensor, and they're trying to reset it. Launch window open until noon.

11:08 update - scrubbed for today.
 
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So, the NROL mission launched this morning. Last Falcon-9 launch of the year, 70th successful landing. It was an RTLS landing.

Being a classified payload, NRO asked SpaceX to not show any video of the second stage, not even the nozzle view. So, the tracking camera stopped following the second stage and followed the booster, so all the video after staging was the booster coming back. Wish they had stayed split-screen to show the tracking camera all the way down.

They had solid onboard camera video all the way to the landing, and went to a splitscreen of a ground view of the landing pad shortly before touchdown. Note the time lag between the leg deploy and also landing on the right side view at the pad, versus the onboard camera (there is always this delay for whatever technical reasons, of about 2 seconds, from the Falcon-9 onboard cameras. So it's not a new thing, just this video shows that delay/lag very well in the landing splitscreen).

 

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