II.

Spacecraft

The Soyuz spacecraft weigh about 7 metric tons and have an oval orbital module in front, a bell-shaped descent module in the middle, and a cylindrical service module in the rear. The orbital module provides living space and carries the docking mechanism, which enables the craft to connect with other spacecraft in orbit. The descent module contains controls and seating for cosmonauts. It is the only part of the craft that returns to Earth. The service module carries rocket engines and the solar panels that are used for supplying electricity.

The changing role of the Soyuz spacecraft has necessitated a variety of design changes. The docking mechanism was modified when the spacecraft was redesigned for the space-station program. It was further modified to enable Soyuz to dock with an Apollo spacecraft of the United States. The failure of certain Soyuz spacecraft also led to safety-related changes such as altering the spacecraft to accommodate cosmonauts in full pressure suits during reentry into Earth’s atmosphere.

Soyuz spacecraft are launched on Soyuz rockets, which consist of four first-stage booster rockets strapped to a core rocket and the second-stage booster. The boosters use liquid fuel composed of kerosene and liquid oxygen. The spacecraft are launched from Baikonur Cosmodrome in Kazakhstan (formerly part of the Soviet Union). The Russians now rent Baikonur for launches. Soyuz descent modules land by parachute. They landed in Kazakhstan until 1991, but since the collapse of the Soviet Union they have usually landed in southern Russia.