Two objects travelling at 28,000 kilometres per hour must meet without destroying each other. Docking is the procedure that joins spacecraft in orbit, and it requires precise navigation, matching velocities, and a final approach measured in centimetres per second.

Russian and American programmes developed different systems during the Cold War. Modern docking ports use standardized mechanisms so vehicles from different countries can connect. The International Space Station has hosted dozens of visiting vehicles over the years.

Phases of a docking

1. Rendezvous, closing the distance between vehicles
2. Station keeping, holding position nearby
3. Final approach along the docking axis
4. Capture and hard mate of the connection

Autonomous docking handles most cargo flights. Crewed vehicles usually retain manual override so astronauts can take control if the automated system misbehaves.