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About sevenperforce

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  1. I believe the droneship landing burns are still 1-3-1 while the RTLS landing burns are single-engine all the way down. And as @Elthy said, Starlink is volume-constrained, not mass-constrained, so a three-engine hoverslam simply isn't necessary. We might see a three-engine hoverslam if they really needed it for a more massive payload. One possibility would be a really large MEO or LEO payload, with a lofted trajectory where they needed all the TWR they could get.
  2. Yes, I am positive they did a WDR. And presumably they will need to do at least one WDR with the full stack. So if they need to retest, that's 4 of 9.
  3. This is a surprisingly tricky question, actually. The best way I know to handle it would be to take into account the hypothetical gravitational lensing effects of the sun. The sun's radius is 232,000 times its Schwarzschild radius, and we have been able to make weak gravitational lensing observations during solar eclipses. So I'm going to make the baseline assumption that visible gravitational lensing is negligible at the edge of a disc 232,000 times the Schwarzschild radius of an object. Since the Schwarzschild radius of the moon is 0.1 mm, that means the "lensing disc" of the moon would
  4. What have I been saying all along? From the research:
  5. This sort of AI/machine learning algorithm seems like a recipe for disaster. Not sure how you'd work around it, though. Suppose, for example, that the machine learns to recognize behavior from certain classes of vehicles (perhaps certain luxury brands) which, as a result, makes it change its behavior around those brands. This allows it to successfully reduce its overall accident rate. However, its change in behavior in turn makes accidents with OTHER vehicles more violent. What's the trade-off? Do you end up with a self-driving algorithm that effectively discriminates against poor people?
  6. In the past week, more Americans have died of COVID-19 than died of the flu during the ENTIRE 2019-2020 flu season.
  7. Edge cases are always going to be the problem. There will be accidents in AI cars. The important thing, however, is that the accident happens because it was a set of unavoidable conditions, not because of a software error. They need to be able to analyze it afterward and say something like, "The other vehicle spun out so abruptly and so unpredictable that there was no combination of control input which would have prevented the collision, but the AI's reaction time was able to reduce the collision impact by 20% well before a human driver would have been able to react." The edge cases
  8. It looks like there was a guidance problem right after restart. Maybe a stuck/stalled fin? Or a gimbal during restart that kicked the booster over. Either way the engine gimbaled very hard to correct and then very nearly tipped over while trying to zero out lateral velocity. After it zeroed lateral velocity it hung there for a pretty long moment in hover before finally dropping to the pad, well off of the center. This does show the advantage of the deep throttle. If a F9 booster came down with that much lateral velocity, it would have no way to make it work. Then again its grid fins
  9. Elon has said that the challenge is not to get AI to be as good as a human driver, but to get AI to be SO MUCH BETTER than a human driver that you KNOW it's safer to get in the car with an AI. The tricky thing is that humans are not all the same. Human reaction time, human distraction level, human ability to solve edge cases and react to new situations, human memory -- these all lie on bell curves, and combine to form one big bell curve. We heuristically assume that people we're getting in the car with are average drivers. But to have the same level of confidence with AI, the software nee
  10. Go for launch in under two minutes. Was it just me or did that hold-down last longer after ignition than usual? Maybe I'm just used to Falcon 9. excrementsttt something went WRONG on that final approach. Shocking it landed safely.
  11. Came here to post this. Very cool! This sort of rapid restart practice is essential.
  12. Arrestor cables are a good place to start but there's a degrees-of-freedom problem. For a carrier tailhook system, gravity and friction with the deck damp any motion perpendicular to the direction of travel. But with a vertical "midair" catch with motion in the z-axis, you can have motion in the x and y axes that remains undamped. If the wires provide vertical damping in the same way as the arrestor cable on a carrier, then Superheavy is going to be hanging from rather long cable loops. Any slight timing difference in which cable catches first is going to result in a tremendous torque/rot
  13. I'm not ascribing any mythical abilities to steel, nor would I. My point is that aircraft tailhooks are made out of welded steel, too. If you are designing the grid fins to take a wire catch point load, steel is a perfectly fine material to work with. They could design for that -- whatever the impact of tower blowback would be, you just aim slightly in the opposite direction.
  14. A few pages back I did the math and just two hot-gas thrusters will be able to handle gusts of up to 50 mph. Plus, Superheavy is HUGE so even without thrusters firing, even a tremendous wind gust would only produce a tiny amount of acceleration on the booster (f = ma, so when m is very big, a is very small).
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