¿Cómo puede la Soyuz llegar a la estación espacial en sólo 3 horas?

Video from the channel Scott Manley about Soyuz (cohete), linked on its Above Ten Thousand entry. Duration: 13:09. Language: English. Video type: Documentary.

Explanatory piece on how Soyuz MS-17 managed to dock with the International Space Station just 3 hours and 3 minutes after launch, half the time the Soyuz used to take and far less than the one-day approaches of the space shuttle or Crew Dragon. It reviews the orbital mechanics of the rendezvous: the lower phasing orbits used to catch up with the target, and the phase angle, which sets the launch window.

The record only applies to the station: in the 1960s, Gemini 11 docked 94 minutes after liftoff, because its targets were deliberately placed in the right orbit. With permanent stations, Soyuz moved to one- or two-day rendezvous, constrained by orbits with no contact with Soviet ground stations and by space sickness, which tended to peak on the first day. Docking is carried out by the Kurs system, made in Ukraine; after a Progress collided with Mir during tests of an alternative system, the United States asked that all missions to the station use Kurs.

For every kilometre below the target's orbit, about 9.4 km is gained per 90-minute orbit. The four-orbit profile requires the station to be about 30° ahead, with a margin of ±12.5°; the two-orbit profile allows only 6°. Digital avionics make it possible to combine manoeuvres and maintain communication throughout the orbit via geostationary satellites, and the near-coplanar injection performed by the rocket's second stage gives a margin of about ±2.5 minutes in the launch time.