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A comment on Crew Dragon Docks with ISS. Parent comment

Re:Crew Dragon Docks with ISS by barbegal on Sunday May 31, 2020 @04:57PM (#23372667)
> The landing algorithm for the first stage uses convex optimization algorithms based on interior point methods, which were not available in the 1960s.

Is this level of optimisation really needed? I thought most of the landing was having enough fuel margin and then running a PID control algorithm during the landing burn.

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Re:Crew Dragon Docks with ISS by pfdietz on Sunday May 31, 2020 @06:11PM (#23373265)
Apparently yes. See Lars Blackmore's chapter in the 2016 "Frontiers of Engineering" (National Academy Press) (free registration required)

https://www.nap.edu/read/23659/chapter/10

https://www.nap.edu/download/23659

"SpaceX uses CVXGEN (Mattingley and Boyd 2012) to generate customized flight code, which enables very high-speed onboard convex optimization."

This is actually a great example of a true NASA spinoff, btw. Lars Blackmore was at JPL before moving to SpaceX. Landing on Mars and landing a first stage back on Earth aren't the same problem, but they're close enough for the work to transfer.

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Re:Crew Dragon Docks with ISS by usrusr on Sunday May 31, 2020 @05:53PM (#23373121)
I believe that the biggest obstacle in SpaceX's "hover slam" landing isn't calculating and controlling the burn but getting sufficiently precise input in time for those calculations. It must be a miracle of sensor fusion.
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