How SpaceX lands Starship (sort of)

Re:How SpaceX lands Starship (sort of) by bodhiandphysics on Thursday May 13, 2021 @10:15PM (#27149897)

There’s one really important aspect of starship control that this article mentions... starship control is stochastic. Spacex needs to minimize the area of an ellipse that represents the likely touchdown area of the craft. To do this they use another trick... they continuously recompute the optimal trajectory, in real time. Lars Blackmore has a paper on the process!

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Re:How SpaceX lands Starship (sort of) by gnzoidberg on Thursday May 13, 2021 @10:39PM (#27150074)

Yep, Lars learned GFOLD at JPL and took it to Spacex. GFOLD was invented by Behçet Açikmeşe https://www.aa.washington.edu/facultyfinder/behcet-acikmese

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Re:How SpaceX lands Starship (sort of) by bodhiandphysics on Thursday May 13, 2021 @10:56PM (#27150175)

Though as I understand, spacex doesn’t actually use GFOLD, but a related (and secret!) development

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Re:How SpaceX lands Starship (sort of) by ClumsyPilot on Friday May 14, 2021 @06:02AM (#27152604)

Not to accuse spaceX of anything, but I've witnessed companies sell 'hyper-localised weather" where they take public weather information and average the nearest two datapoints to you.

So I always take 'secret' 'proprietary' data and algorythms with a bit of salt, as almost every time I dug into them, it was all spin on previous public stuff.

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Re:How SpaceX lands Starship (sort of) by loudmax on Friday May 14, 2021 @09:05AM (#27153804)

In this case, SpaceX is actually landing those Falcon boosters pretty reliably now. So maybe their secret proprietary stuff isn't as advanced as they make it out to be, but whatever they're doing it does seem effective.

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Re:How SpaceX lands Starship (sort of) by jhgb on Friday May 14, 2021 @08:00AM (#27153276)

The two have apparently co-authored the relevant papers. So perhaps both of them "learned GFOLD at JPL" in the same sense.

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Re:How SpaceX lands Starship (sort of) by mseri on Friday May 14, 2021 @08:05AM (#27153316)

Cool, do you have a link for the paper?

EDIT: Found I think [http://www.larsblackmore.com/nae_bridge_2016.pdf]

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Re:How SpaceX lands Starship (sort of) by tboerstad on Friday May 14, 2021 @04:13AM (#27151953)

This sounds like model predictive control. Does anyone know the difference between the methods?

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Re:How SpaceX lands Starship (sort of) by pillefitz on Friday May 14, 2021 @06:39AM (#27152794)

You can implement it as MPC and minimize e.g. the trace of the covariance matrix that describes the state uncertainty. Wrote my thesis on something similar.

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