[Illustration: 77. Artist conception of the Apollo-Soyuz Test
Project rendezvous.]
On May 24, 1972, President Richard Nixon and Aleksey Kosygin, Chairman
of the USSR Council of Ministers, signed an agreement “concerning
cooperation in the exploration and use of outer space for peaceful
purposes.” The signing represented a formal endorsement of negotiations
that had been held between the two nations over several years. The
agreement established the Apollo-Soyuz Test Project (ASTP) to develop
and fly a standardized docking system “to enhance the safety of manned
flight in space and to provide the opportunity for conducting joint
scientific missions in the future.”
On July 15, 1975, the afternoon countdown for the Soviet launch was
completed and _Soyuz_ lifted off from the Baykonur complex near Tyuratum
in Central Asia, some 3200 kilometers (2000 miles) southeast of Moscow.
_Soyuz_ carried cosmonauts Alexey Leonov and Valeriy Kubasov.
Taking advantage of _Apollo_’s larger fuel supply for maneuvering,
_Apollo_ followed _Soyuz_ into orbit 7½ hours later. _Apollo_ was
launched atop a Saturn 1B from Kennedy Space Center, Florida.
After careful maneuvering, the two craft linked up around noon on July
18. Some 225 kilometers (140 miles) above Earth, the astronauts and
cosmonauts visited each other’s craft, performed joint experiments, and
made further tests of the new docking system.
Following the undocking Saturday, _Apollo_ fired its engines briefly and
moved away from _Soyuz_. _Soyuz_ descended from orbit and landed in the
south-central USSR early Monday morning, July 21.
Astronauts Stafford, Slayton, and Brand remained in orbit conducting
research and making science demonstrations. Splashdown into the Pacific
Ocean occurred in late afternoon on Thursday, July 24.
The historic ASTP mission was accomplished by using existing systems and
a new docking module. The _Apollo_ spacecraft was made available when
the lunar-landing program was curtailed. Since the command module was
built with a docking system designed to work only with U.S. spacecraft,
a method of incorporating the new docking system had to be devised.
A second important problem was the difference between the spacecraft
atmospheres. The _Apollo_ used a pure oxygen atmosphere at about
one-third of the atmospheric pressure on earth’s surface; _Soyuz_ used a
nitrogen-oxygen mixture at normal atmospheric pressure. To permit crews
to pass from _Soyuz_ to _Apollo_ without suffering from the “bends” (a
painful condition experienced when nitrogen gas bubbles form in the body
fluids), engineers had to design an airlock to equalize the pressure.
[Illustration: 78. The Soviet _Soyuz_ atop a three-stage launch
vehicle lifts off July 15, 1975, to begin the joint US-USSR space
mission.]
[Illustration: 79. Overhead view of _Soyuz_ in orbit, photographed
from the _Apollo_ spacecraft during the joint mission. The three
major components of the _Soyuz_ are the spherical Orbital Module,
the bell-shaped Descent Vehicle, and the cylindrical
Instrument-Assembly Module from which two solar panels protrude.]
[Illustration: 80. View of _Apollo_ spacecraft as seen in
Earth-orbit from _Soyuz_. The Command/Service Module and Docking
Module are contrasted against a black-sky background and the horizon
of the Earth is below.]
The docking module, 3 meters long and 1.5 meters in diameter (10 feet
long and 5 feet in diameter), also solved the problem of incompatible
docking mechanisms by carrying the new docking system on one end and a
system compatible with _Apollo_ on the other.
Prime contractor for Apollo Command Module, Service Module, and Docking
Module was Rockwell International.
The _Apollo_ hardware is from the National Aeronautics and Space
Administration, and the _Soyuz_ spacecraft is on loan from the USSR
Academy of Sciences.
_Apollo_
Command module
Base diameter 3.90 m. (12.8 ft.)
Length 3.66 m. (12 ft.)
Weight 5896 kg. (13,000 lb.)
Service module
Diameter 3.9 m. (12.8 ft.)
Length 6.71 m. (22 ft.)
Weight at launch 24,947 kg. (55,000 lb.)
Docking module
Diameter 1.52 m. (5 ft.)
Length 3.05 m. (10 ft.)
Weight 1882 kg. (4155 lb.)
_Soyuz_
Orbital module
Diameter 2.29 m. (7.5 ft.)
Length 2.65 m. (8.7 ft.)
Weight 1224 kg. (2700 lb.)
Descent module
Diameter 2.29 m. (7.5 ft.)
Length 2.20 m. (7.2 ft.)
Weight 2802 kg. (6200 lb.)
Instrument module
Diameter 2.77 m. (9.75 ft.)
Length 2.29 m. (7.5 ft.)
Weight 2654 kg. (5850 lb.)