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SpaceX nails triple booster landing after satellite delivery

bbc.com

21–30 of 128 posts

Re: SpaceX nails triple booster landing after satellite delivery

#21
There's a great media thread on reddit where people post their own photos and videos: https://www.reddit.com/r/spacex/comments/bbhz9a/rspacex_arab...

Here's a great video of the entire flight and landing of the side boosters in one shot, made with custom tracking software: https://www.youtube.com/watch?v=cEZZkEXAD6Q

Re: SpaceX nails triple booster landing after satellite delivery

#23
post #8

I wonder how they do the booster landings? Is it precise modelling and standard control algorithms, or something more exotic like neural networks?

It's done using convex optimization https://www.nap.edu/read/23659/chapter/10#39

How is "booster landing" mapped to a convex optimization problem?

Re: SpaceX nails triple booster landing after satellite delivery

#24
post #16

Not only that, but apparently they recovered both fairings: https://www.google.com/url?sa=t&source=web&rct=j&url=https:/... So 5 out of 5...

It's an interesting issue with the fairings, and I'm interested to see what (or if) they're going to solve the issue with the saltwater contaminated fairings.

Being a SpaceX launcher, as the article indicates, means they can accept higher risks, but in turn has a greater financial risk to the company. It's times like this where I'm glad SpaceX is a private company.

Re: SpaceX nails triple booster landing after satellite delivery

#25
post #14
post #3

Earlier quoted context omitted.

I'm more impressed by the booster landings though :-) Seeing a launch/landing in-person is on my bucket list.

I saw the live stream yesterday and when the two side boosters landed side-by-side synchronously it was almost as if it was out of a movie. We are living in the future!

On this launch, it looks like they offset the timings to reduce the chance of tipping over.

If you get time, go look for the first FH booster landings. The timing is almost perfect and the long exposure images looked beautiful.

Re: SpaceX nails triple booster landing after satellite delivery

#27
post #23
post #8

Earlier quoted context omitted.

It's done using convex optimization https://www.nap.edu/read/23659/chapter/10#39

How is "booster landing" mapped to a convex optimization problem?

Lars Blackmore, who works for SpaceX, has a page about the techniques that are used here:

http://www.larsblackmore.com/losslessconvexification.htm

See also: https://www.aa.washington.edu/facultyfinder/behcet-acikmese

Re: SpaceX nails triple booster landing after satellite delivery

#28
post #5

I wonder what emergency procedure is in place in case the landing is off-course. Does it blow itself up?

The booster's trajectory targets offshore or away from droneship in case landing burn fails. The landing burn brings the booster onto the landing pad. See CRS-16 where the booster landed in the water when the booster lost roll control when the grid fins failed.

They've had a few "on purposes misses" over the years. The Falcon Heavy demo launch had the center core purposely miss the droneship as it was coming in way too fast since 2 of the engines didn't light.

IIRC it purposely missed the droneship by only a few hundred meters, but it was going something like 300 miles per hour!

Re: SpaceX nails triple booster landing after satellite delivery

#29
post #5

I wonder what emergency procedure is in place in case the landing is off-course. Does it blow itself up?

As far as I understand, the Flight Termination System is safed before the landing burn. It's more dangerous to have it potentially still active after landing. So at this point it can't blow itself up anymore. Until the last moment it also doesn't target the barge itself, but slightly to the side. Only very shortly before landing does it correct the target to the actual landing position. So in most cases it would simp…

If you watch the livestream for yesterday's falcon heavy launch on youtube the second camera angle is a rendering showing trajectory, and you can actually see the center core adjusting closer and closer to the droneship with each step as it gets more confident that it's able to land safely.

Re: SpaceX nails triple booster landing after satellite delivery

#30
post #25
post #14

Earlier quoted context omitted.

I saw the live stream yesterday and when the two side boosters landed side-by-side synchronously it was almost as if it was out of a movie. We are living in the future!

On this launch, it looks like they offset the timings to reduce the chance of tipping over. If you get time, go look for the first FH booster landings. The timing is almost perfect and the long exposure images looked beautiful.

They are supposed to be offset for radar purposes. The fact the first time was so close was a mistake, fortunately it worked.
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