I wanted to know what the fastest speed is that a Falcon 9 can land at and thus the max force the landing legs can withstand. I assumed the mass when landed is 26,000 kg (I once heard that somewhere). That means that when it is just standing there each leg will have (26,000 kg * 9.8 m/s^2) / 4 = 63,700 N of force on them. I did some video analysis on the Falcon 9 flight 26 (15 June 2016). This landing failed because it ran out of propellant just before landing so it fell a few meters. I thought this could be a good estimate for just above the upper bound of landing speed. My calculations showed that it was traveling at about 30 m/s at touchdown. Another rough estimate I made is that it takes 0.1 seconds from when the legs just touch the ground to a complete stop. That would the landing of flight 26 (26,000 kg * (30 m/s / 0.1 s)) / 4 = 1,950,000 N. Is it reasonable to assume the the legs could survive up to 325,000 Newtons, making the max landing speed 5 m/s?

  • $\begingroup$ Not entirely sure why this was downvoted... $\endgroup$ – Ingolifs Mar 21 '19 at 1:05
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    $\begingroup$ I think "plausible guess" would be more accurate. Unless I misunderstand, you essentially took a failure case and halved it right? 15m/s sounds pretty fast for a 26 tonne machine to hit a barge and survive. Most landings also look much slower than that, though my eyes have deceived me before. Props for taking a stab at an analytical answer though! I am pretty curious now. $\endgroup$ – ben Mar 21 '19 at 2:44

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