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Crew Dragon after SECO: Orbital Vfelocity at 27,000km/h at 200km altitude (roughly 9-10min after liftoff).crewdragon

ISS Orbital Velocity at ca. 28,000 km/h at 400km altitude.iss_altitude,iss speed

However from the equation $v = \sqrt{\frac{GM}r}$, I expect Crew Dragon to actually rotate faster than the ISS around earth?! What is wrong with my thinking?

Randy Welt
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    sources for you figures? Most likely a non-circular orbit, with further orbital rendezvous manoeuvrers to follow. –  Dec 24 '20 at 10:10
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  • If your source was the video, that might still be ground speed relative to the rotating Earth's surface, after all, it starts at zero, not 465 $\sin(lat)$ m/s right? 2) The vis-viva equation is $$v=\sqrt{GM \left(\frac{2}{r}-\frac{1}{a} \right)}$$ which works for elliptical orbits (and I think hyperbolic ones as well if you are careful). Your equation is for circular. Use the complete equation and solve for $a$ and you may discover that Crew Dragon was in an elliptical orbit that will carry it to or past the ISS' altitude. It's just a guess
    • – uhoh Dec 24 '20 at 10:21
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    Min/Max apogee 197km/202km (source: Commentator Crew Demo in Livestream Youtube Video) that orbit is elliptical, but always roughly 200km below ISS. – Randy Welt Dec 24 '20 at 10:22
  • My current guess is that it only works due to inertia. – Randy Welt Dec 24 '20 at 11:33
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    Possible duplicate of 2nd stage speed - with respect to what? (SpaceX webcast of Orbcomm OG2 deployment). The answer makes it clear that @uhoh is correct: The velocities are Earth-centered Earth-fixed rather than Earth-centered inertial. – David Hammen Dec 24 '20 at 16:03
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    @DavidHammen thanks for finding that, this sounded familliar. Wow five years ago already! – uhoh Dec 24 '20 at 17:25
  • rats. I nearly changed my comment to "inertial frames" –  Dec 24 '20 at 19:13
  • Thank u David. It is a Duplicate, but seems with ISS as rendezvou reference a more nice example. Also, I like to request some Youtubers to do a telemetry tutorial!! Still do not understand what exactly is the advantage of showing Earth-Center-Fixed Velocities, other than adding artifical complexity?! If anyone can give an answer for check-marking, will be nice. – Randy Welt Dec 24 '20 at 20:12