These names each consisted of a significant word followed by the number 7 (representing the seven original astronauts) and were used as the call signs by the capsule communicators (CAPCOMs).
A notable exception was that Gus Grissom named his Gemini 3 spacecraft Molly Brown after the Titanic survivor, as a joke based on his experience with his Liberty Bell 7 capsule sinking.
The Apollo call signs were: For project Skylab, the practice returned to using the mission name as the spacecraft call sign, since the Skylab station was left uncrewed while the shuttle vehicle (an Apollo CSM) carried a crew to it or back to Earth.
The six Space Shuttle orbiters were given individual names (they also had letter-and-number callsigns) by NASA, which were used as the call signs: Enterprise (OV-101, which was not fitted for spaceflight), Columbia (OV-102), Challenger (OV-099), Discovery (OV-103), Atlantis (OV-104), and Endeavour (OV-105).
As Boeing Mission Control (MCC-CST) is located at the Johnson Space Center, the standard JSC call sign Houston is used.
Pavel Popovich and Andriyan Nikolayev's call signs in their joint flight in Vostok-3 and Vostok-4, Sokol ("falcon") and Berkut ("golden eagle"), were widely popularized by Soviet media.
The call sign of the launch facility itself for Vostok was nearly a code word: Zarya, meaning "dawn".
Early Soyuz flights intent on practicing docking procedures were given call signs elaborating on the first few letters of an alphabet.
Later Soyuz flights to the Salyut space stations and Mir had less noteworthy call signs: Foton, meaning "photon", etc.
When different space missions and different control centers work together in joint operations, for example when a Dragon capsule docks to the ISS, NASA connects all communication channels using what is known as the Big Loop.
[10] When communicating on the Big Loop, one can hear the call signs Dragon, Starliner, SpaceX, Houston and Station at any given time.