4 ms·

From the booster's point of view, the catch is a target location and speed. Plus a set of tolerances: however much the arm can swing to catch it, and horizont

From the booster's point of view, the catch is a target location and speed. Plus a set of tolerances: however much the arm can swing to catch it, and horizontal speed has to be really low because it needs to drop down vertically into the arms. I would expect that the target on the ocean, even for the first test, is very specific. Once the booster can hit a phantom target, they can change the target to the tower and go for a catch attempt.

usrusr 3y ago
I imagine that lack of stable reference points would be an issue on the ocean. Both for the algorithms under test and for validation. (I liberally use "algorithm" here as the superset of both algorithm and the hardware it runs on, I think in reality these tests are mostly for correcting parameters that are hard to determine with sufficient accuracy on paper) If you want to write off an entire booster, adding a dummy tower somewhere in the desert would not add much to the bill and could well be worth it. Or maybe even a not-quite-so-dummy tower, but off-site, where the booster would be scrapped on location (instead of reflown) even in the best case, no matter how hypothetical?
- Laremere 3y ago
  Good GPS in ideal conditions (no trees or buildings blocking/bouncing signal) has accuracy on the centimeter scale: https://www.gps.gov/systems/gps/performance/accuracy/ https://www.gps.gov/systems/gps/performance/accuracy/
  - usrusr 3y ago
    But in a real landing, they wouldn't want to be accurate relative to some GPS goalpost, they need to be accurate to whatever physical reality turns out to be. Reconciling expectations about were the landing location was supposed to be and where sensor input says it is must be of major importance. That link tells us that the signals are intended to be sent with an accuracy better than 200 cm 95% of the time. Using more frequencies only really helps avoiding errors from bad/misleading reception, so it's hardly relevant in "ideal situations". Long term stationary receivers can resolve to millimeters, but dropping rockets from orbit isn't exactly a thing that would be considered "stationary" in this context.

usrusr 3y ago

I imagine that lack of stable reference points would be an issue on the ocean. Both for the algorithms under test and for validation. (I liberally use "algorithm" here as the superset of both algorithm and the hardware it runs on, I think in reality these tests are mostly for correcting parameters that are hard to determine with sufficient accuracy on paper) If you want to write off an entire booster, adding a dummy tower somewhere in the desert would not add much to the bill and could well be worth it. Or maybe even a not-quite-so-dummy tower, but off-site, where the booster would be scrapped on location (instead of reflown) even in the best case, no matter how hypothetical?

Laremere 3y ago
Good GPS in ideal conditions (no trees or buildings blocking/bouncing signal) has accuracy on the centimeter scale: https://www.gps.gov/systems/gps/performance/accuracy/ https://www.gps.gov/systems/gps/performance/accuracy/
- usrusr 3y ago
  But in a real landing, they wouldn't want to be accurate relative to some GPS goalpost, they need to be accurate to whatever physical reality turns out to be. Reconciling expectations about were the landing location was supposed to be and where sensor input says it is must be of major importance. That link tells us that the signals are intended to be sent with an accuracy better than 200 cm 95% of the time. Using more frequencies only really helps avoiding errors from bad/misleading reception, so it's hardly relevant in "ideal situations". Long term stationary receivers can resolve to millimeters, but dropping rockets from orbit isn't exactly a thing that would be considered "stationary" in this context.