Apollo-Soyuz test project

(ASTP), a joint experimental flight of an American Apollo spacecraft and a Soviet Soyuz spacecraft. The program of the ASTP was confirmed by a Soviet-American agreement on cooperation in the exploration and use of space for peaceful purposes, which was signed on May 24, 1972.

The main objectives of the ASTP were as follows: to test the components of a compatible rendezvous system in orbit; to test two-way, or active-passive, docking mechanisms (seeDOCKING); to test the methods and equipment for the transfer of astronauts from one spacecraft to another; and to acquire experience in conducting joint US-Soviet space flights, including, if necessary, rendering assistance in emergencies. In addition, the aims of the ASTP included a study of the possibility of controlling the attitude of docked spacecraft, a study of communications between spacecraft, and the coordination of the operations of the American and Soviet flight control centers. During preparations for the flight, Soviet and American designers solved a set of complex problems to ensure the compatibility of, for example, the spacecraft search and rendezvous systems, docking mechanisms, life support systems, communications gear, and flight controls equipment.

At 3:20 P.M. (Moscow time) on July 15, 1975, the Soyuz 19 spacecraft, with cosmonauts A. A. Leonov and V. N. Kubasov aboard, was launched from the Baikonur Cosmodrome. At 10:50 P.M., an Apollo spacecraft, with astronauts T. Stafford, D. Slayton, and V. Brand aboard, was launched from the Kennedy Space Center at Cape Canaveral, Fla. The two spacecraft docked at 7:12 P.M. on July 17, in the 36th orbit of the Soyuz spacecraft. The spacecraft undocked on July 19, in the 64th Soyuz orbit, and docked again in the 66th orbit. The spacecraft undocked for the last time in the 68th orbit of Soyuz 19 and then proceeded on separate orbits. The total flight duration was five days 22 hr 31 min for Soyuz 19 and nine days 1 hr 28 min for the Apollo spacecraft. The total flight duration while the two spacecraft were docked was 46 hr 36 min.

In the joint flight, several scientific studies and technical experiments were carried out. In an artificial solar eclipse, the Soyuz crew studied the solar corona and the gases around the two spacecraft during an occultation of the sun by the Apollo spacecraft. In an ultraviolet absorption experiment, the concentrations of atomic oxygen and nitrogen in space were measured at the flight altitude. In an experiment with zone-forming fungi, the effects of the aggregate of space-flight factors—that is, of weightlessness, physiological acceleration, and space radiation—on basic biological rhythms were investigated. In a microbial exchange experiment, the exchange of microorganisms between individual crew members and between the crews of the two spacecraft was studied under space-flight conditions. In a test of a general-purpose furnace, the effect of weightlessness on certain metallurgical and crystal-chemical processes in metallic and semiconductor materials was investigated.

The Apollo-Soyuz Test Project was an important step in the development of international cooperation in the exploration and use of space for peaceful purposes.