Crew Dragon: Go For Docking

[Stephanie B]

..... hard capture complete!

[LittleLebowski]

This has been wonderful to watch, today and yesterday.

[peterb]

Wow. Watching the dance of the attitude thrusters during the docking approach, or the fin movement during the first stage descent — that team wrote and tested a lot of good code.

The orbital mechanics for docking are strange. I remember being amazed when I first read about it.
————
However, the Gemini 4 attempts at rendezvous were unsuccessful largely because NASA engineers had yet to learn the orbital mechanics involved in the process. Simply pointing the active vehicle's nose at the target and thrusting was unsuccessful. If the target is ahead in the orbit and the tracking vehicle increases speed, its altitude also increases, actually moving it away from the target. The higher altitude then increases orbital period due to Kepler's third law, putting the tracker not only above, but also behind the target. The proper technique requires changing the tracking vehicle's orbit to allow the rendezvous target to either catch up or be caught up with, and then at the correct moment changing to the same orbit as the target with no relative motion between the vehicles (for example, putting the tracker into a lower orbit, which has a shorter orbital period allowing it to catch up, then executing a Hohmann transfer back to the original orbital height).[6]

https://en.wikipedia.org/wiki/Space_rendezvous

[5pins]

They just entered ISS.