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by timmaxw 1204 days ago
I wanted to go for a record of as many flips as possible. So I boosted up to 25,000 feet; started spinning until it was doing about one flip per second; waited a few minutes; then turned on the autopilot to come into a landing.

The autopilot did a perfect job of stopping the rotation and lateral motion, so the lander came down straight as an arrow. Unfortunately, the autopilot didn't even try to decelerate! I crashed into the moon at 0.9 degrees and 770 MPH.
2 comments
ricardobeat 1204 days ago
The target velocity is a factor of height, and the autopilot has “160” hardcoded as the ceiling, so going above that means it will never decelerate fast enough.

https://github.com/szhu/lunar-lander-autopilot/blob/master/a...

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szhu 1204 days ago
That's a ceiling for the speed the autopilot is okay with letting the lander descend. There is no ceiling to how much hard it will try to "apply the brakes".

I agree that the target velocity calculation is off though. I was excited that I came up with something reasonably theoretically correct for correcting rotation... and for figuring out when to fire the engines I just gave up and eyeballed it :)

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szhu 1204 days ago
Update: I added a new algorithm, and I think it might be impossible to crash the ship now.

Let me know if you can still reproduce the bug!

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manbash 1203 days ago
Max speed: 148.7 Max height: 3998 Flips: 34

Perfect landing. :)

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timmaxw 1203 days ago
Yep, it lands safely now!
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