SpaceX recovery attempt not successful: water landing instead of land | Hacker News Reader

SpaceX recovery attempt not successful: water landing instead of land

clips.twitch.tv

78 pointsdolfje25 comments

This twitch video appears to be shot from Jetty Park, so there's a hill in the way. The people talking in the video can't see that the booster is out over the water. This is actually what's supposed to happen if the rocket thinks it has a problem: it's pointed offshore until the middle of the final landing burn. If it's unhappy, it stays pointed at the ocean.

This video from a plane shows how far offshore it was: https://twitter.com/flying_briann/status/1070392207696453632

And Elon's tweet with SpaceX's video from the booster itself: https://twitter.com/elonmusk/status/1070399755526656000

Surprised but glad it didn't explode after it fell over. Apparently they plan to use it for internal projects, which I took to mean the in-flight abort test of the Dragon.

I seem to recall that the Block 5 is targeting >10 reuses so even if they flub 1 in 20 landings going forward that's far from the end of the world in ROI terms.

It’s pretty much out of fuel by then, so an explosion isn’t very likely.

To be fair, there are plenty of examples of it exploding after touchdown in the early days (of landings), both on the barge and in the water, some which are pretty spectacular looking!

It may not meet the technical definition of an "explosion", but the fact that it's still intact here is a testament to how "soft" this hard landing was.

There's lots of great videos to prove you wrong on that one, actually.

The most dangerous time for a can of gasoline is when it's just been emptied- because it's actually full, just of air and gasoline vapor. It's a bomb at that point if you aren't careful. Rockets? Similar problems.

Watch what happened a few years ago when another Falcon 9 fell over because of a faulty landing leg: https://www.youtube.com/watch?v=xr7GcpFGWd0

Rockets contain both fuel and oxidiser, explosions when they are full are considerably worse than when empty. Compare the video you have linked to clips of Atlas or Soyuz blowing up on the pad.

Too true! The Falcon 9 that exploded on the launch pad certainly proved that point.

Nonetheless, an empty rocket is still dangerous.

4 of 6 water landings blew up. A small amount of LOX goes a long way.

ElonMusk just posted a video of the actual landing - including the fall.

https://twitter.com/elonmusk/status/1070399755526656000

That's a great video, thanks for posting.

Although it didn't land as they wanted, primary mission is still success. Also the booster is in the sea and still transmitting and will be recovered, but only be used for internal spaceX missions. Unfortunately the live spaceX webcast tuned away from the failing booster. But Elon has given his word it was wrong to tune away.

The issue is apparently with the hydraulics system of the grid fins that had a problem. It was nice to see that the gimballing engines recovered the spin before the sea landing.

It's been just 3 years since the first rocket landing, and we're so used to it to the point that today's mishap will get more coverage than yesterday's achievement. Seeing the renewed speed of the space launch industry puts a huge smile on me.

Actually, that was a good "intact water landing" the rocket stopped the spin before landing, then the rocket positioned itself so it fell horizontal on the water for retrieval instead of vertical

Does that mean that it uses some side boosters to ensure that the movement from vertical to horizontal is controlled?

This is the best video of the failed landing attempt I've seen so far. Elon tweeted a grid fin hydraulic pump stalled.

I understand for "marketing" reasons why they stopped the video feed from the first stage but since there wasn't any danger to humans here I was disappointed that they cut away from that and pretty much went into the damage control speak of "the primary mission is going well."

Elon's saying they shouldn't have cut away from it. He just posted the rocket-eye view of the water landing:

https://twitter.com/elonmusk/status/1070399755526656000

Engines stabilized rocket spin just in time, enabling an intact landing in water! Ships en route to rescue Falcon.

Although I'm completely unqualified to comment on it, I did notice that the spin seemed to reduce at the same time the landing legs extended. I'm wondering if they may have acted like fins and contributed to the countering of the rotation. If that's the case, it might be that a contingency approach of a small extension of the legs outwards (only a little) might help.

extending the landing legs will reduce roll rate for exactly the same reason a figure skater slows down when they extend their arms: roll axis moment of inertia goes up.

I'm sure they'll release video of it sooner or later. They not long ago release that montage of all their rocket failures.

I'm a little disappointed too, but it was probably the right call by them to cut the feed.

For those whose day it is to hear about this: https://www.youtube.com/watch?v=bvim4rsNHkQ

Can't say they don't have a sense of humor about it.

And bear in mind that these things are 12-storey-high explosive tubes landing from 75km up in the air

> SpaceX recovery attempty not successfull: water landing instead of land

Perhaps some mod can fix the typos in the title?

Did they actually have a plan to divert to water if they knew they couldn't safely land?

They aren't clear about whether it was an accident that they ended up in the water or was it by design. They could have planned ahead for this situation, if they detect that they have a problem and can't do a normal safe landing (the out of control spin) and then they could send it for a 'safe' and hopefully controlled water landing like they did. Or it could just be that it was way off course because they couldn't control it and it was just luck.

It’s by design. The default for all F9 rockets is to land off-shore in the water. Once all the checks are complete and the rocket is “happy” and all systems are performing nominally, it redirects to the landing zone (either a barge or on land).

That is really cool and makes sense. I continue to be impressed and delighted by spacex engineering and design.

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