Entry Source: The Complete James Bond Movie Encyclopedia by Steven Jay Rubin

A manned U.S. spacecraft about to enter its fourth orbit of the Earth in the You Only Live Twice teaser. While one of its astronauts is on an EVA mission, the ship is attacked by the mysterious SPECTRE Intruder—a spacecraft capable of swallowing the U.S. capsule, which it does, severing one of the astronaut’s lifelines and sending him into a deep-space grave.

Entombed inside the Intruder, the Jupiter 16, along with its remaining astronaut, is brought back to Earth inside the cone of a dormant Japanese volcano, which is now the secret rocket base of SPECTRE chief Ernst Stavro Blofeld (DONALD PLEASENCE). Although it isn’t identified as such, the ship, piloted by two astronauts, is patterned after the Gemini spacecrafts that were prominent in the U.S. space program of the mid-1960s.