Rendezvous (space travel)

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The Agena docking adapter for the Gemini flights
Apollo command module and docked lunar module (Apollo 9)

A rendezvous is the targeted approach of two missiles in space . Although it can also mean that a space probe reaches its target planet, the term mostly refers to the approach of two spaceships or a spaceship ("interceptor") to a space station ("target"), which is in orbit with no drive. The maneuver is determined by two forces: on the one hand by the gravitational pull of the planet (or moon) around which the two ships circle, on the other hand by the centrifugal force of the two ships, which is determined by their respective speed and which is exactly opposite to the gravitational force. Only one of the two spacecraft is actively controlled and moves in the same orbit from behind using suitable orbit maneuvers towards the other, passive spacecraft.

It should be noted that to catch up from behind in a circular orbit, an acceleration of the following spaceship causes it to move into a higher and thus longer orbit (because it is a longer circular arc) than the one flying ahead. This means that the spacecraft in pursuit will be faster, but due to the greater centripetal force it will inevitably drift into a higher orbit, the orbit of which would take longer than the orbit of the spacecraft in pursuit. This would give the tracked ship even more of a head start than it already has. - If a spacecraft flying ahead is to be overtaken, the speed of the pursuing ship in the same orbit must be reduced. This is done by switching on the main engine against the direction of flight for an exactly calculated number of seconds. To do this, the spaceship with position nozzles must first be rotated 180 degrees so that the main engine points in the opposite direction. By igniting the engine, the following spaceship loses speed and in the course of the next half orbit period sinks closer to earth and moves on the new, lower orbit at lower own speed, but faster (because of the shorter orbital period ) compared to the pursued spaceship . One also speaks of a higher angular velocity, which refers to the orbiting planet or moon. At the right moment, the main engine has to be accelerated again so that the following spaceship comes back into the same, higher orbit as the pursued spaceship, but this time directly behind it. The actual meeting and docking of the two spacecraft is brought about manually in the final phase by carefully switching on the position nozzles mounted around the spacecraft and acting in several directions and not by the main engine, which only allows rough changes in flight speed.

The goal of a rendezvous is often a coupling (docking) . Both spacecraft must be equipped with compatible docking mechanisms. For the transfer of space travelers or material, the spacecraft must have appropriate hatches. The exchange usually takes place via locks , only in rare cases in free space.

Historical overview of rendezvous and dockings

  • August 12, 1962: Vostok 3 and Vostok 4 approach each other within 6.5 km. This is based on precise calculations right from the start and not on steering (maneuvering) the spaceships.
  • June 16, 1963: Vostok 5 and Vostok 6 repeat this maneuver and approach each other within 5 kilometers.
  • December 15, 1965: First piloted rendezvous of manned spaceships by Gemini 6 and Gemini 7 . At times the distance is only 30 cm.
  • March 16, 1966: first coupling in manned space travel: Gemini 8 docks with an unmanned target satellite.
  • July 19, 1966: Gemini 10 docks with an unmanned target satellite and uses its engine to enter another orbit where a rendezvous with another satellite takes place.
  • October 30, 1967: first coupling of two unmanned Soyuz spaceships under the designations Kosmos 186 and 188 .
  • October 26, 1968: Soyuz 3 rendezvous with unmanned Soyuz 2 , but coupling fails.
  • January 16, 1969: Coupling of Soyuz 4 and Soyuz 5 . Two cosmonauts get out of their spaceship and into the other. This is the first transfer of space travelers between spaceships.
  • March 3, 1969: Apollo 9 completes the first docking of an Apollo spacecraft with the lunar module . Two days later, space travelers first transfer from one spaceship to another through a tunnel.
  • May 23, 1969: first rendezvous and docking in lunar orbit through Apollo 10 : the lander Snoopy meets the mother ship Charlie Brown ; further such maneuvers in the further missions.
  • October 13, 1969: first rendezvous of three spaceships through Soyuz 6 , Soyuz 7 and Soyuz 8 . Planned docking fails.
  • April 23, 1971: Soyuz 10 docks at the Salyut 1 space station , no transfer of cosmonauts.
  • June 6, 1971: Soyuz 11 docks at the Salyut 1 space station , the first transfer to a space station.
  • May 26, 1973: first docking of an Apollo spacecraft at the American space station Skylab
  • July 17, 1975: first international docking of two spaceships as part of the Apollo-Soyuz test project
  • January 22, 1978: the first unmanned Progress 1 transporter docks at the Salyut 6 space station
  • April 11, 1987: After several days of attempts, the Kwant 1 module was successfully docked to the Mir space station . This is the first time a space station has been expanded into orbit.
  • February 26, 1995: The American space shuttle Discovery rendezvous with the Russian Mir space station and orbits it for inspection. Docking is not carried out.
  • June 29, 1995: the American space shuttle Atlantis docks at the Russian space station Mir ( Shuttle Mir program ).
  • After 1995: The docking maneuvers to the Mir and later to the ISS were perfected and took place every few months, especially when the crew changed.
  • From July 2005, the US space shuttle began practicing the Rendezvous Pitch Maneuver (RPM) to check the heat shield for possible damage.
  • On April 3, 2008, a European transporter docks fully automatically at the ISS for the first time .
  • On November 2, 2011, the first coupling of Chinese space travel between the unmanned spaceship Shenzhou 8 and the space station Tiangong 1 succeeded .

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