The handshake in orbit was a critical event in a temporary thaw in US-Soviet relations known as détente: a period when the two superpowers tried to steer away from confrontation and toward peaceful coexistence after the US had withdrawn from Vietnam.

The bid to warm relations was a partial failure, as direct confrontation gave way to proxy wars, but it nonetheless produced a tangible reduction in tensions. The Apollo–Soyuz Test Project (ASTP) was, to a large extent, a public relations exercise selling détente to skeptics in both camps.



The idea for a joint space mission was first devised in 1970, but it took two years for the idea to evolve into a signed agreement. Three more years were spent resolving technical and organizational details, training crews at both American and Soviet facilities, and preparing the actual launches.

Couplings and copulations

For NASA, ASTP was the last mission of the Apollo program. The biggest alteration to the spaceship was the replacement of the moon landing module with a docking adapter. The Apollo vehicle’s atmosphere consisted of pure oxygen under low pressure while the Soyuz spacecraft had an oxygen-nitrogen mix similar to regular breathing air at normal pressure. Coupling the two capsules directly would have disrupted life support on both. A three-hour transition period, when air from the two vehicles passed through the adapter, was introduced to resolve the problem. The Russians also had to develop new flame-retardant fabric for their suits in order for them to be suitable for the oxygen-rich environment of their American hosts.

The docking also required that a new mechanism, called an Androgynous Peripheral Attach System (APAS), be developed. Designs derived from that project are still in use on the ISS and in China’s space program. Previously both space-faring nations had used a probe-and-drogue mechanism, which is similar to an electric plug and socket in the sense that two halves of different “sexes” were needed for coupling to be possible.



APAS was made to be able to serve as either ‘male’ or ‘female’ during a docking procedure, as needed. A lewd joke claims that neither country was willing to install a ‘female’ mechanism on its spaceship, as it would have implied submission. Anyhow, during the series of dockings and redockings, both Apollo and Soyuz had a chance to take the active role in the procedure.

Grim shadow over Soyuz

The Soyuz spacecraft was a work in progress at the time of the mission, with serious modifications having been introduced in 1973. They had been called for after the Soyuz-11 disaster in which three cosmonauts died after their capsule accidentally depressurized at high altitude during reentry.



The disaster prompted designers to reduce the crew to just two people in order to free up enough space for them to wear pressure suits during launch and reentry. The two Soviet crew members of the Apollo-Soyuz mission, Aleksey Leonov and Valery Kubasov, were meant to have flown in the ill-fated Soyuz-11, but had been pulled off the mission due to a suspected infection.



The USSR carried out extensive testing and preparations for the all-important joint mission. Six spacecraft similar to the Soyuz-19 that actually flew to rendezvous with Apollo were built. Two were used in unmanned test flights, one was manned for the Soyuz-16 mission, one was actually used in ASTP, and two were kept on the ground as backup, including one which was fully fueled and ready to fly a rescue mission if needed.

Three languages in orbit

The historic mission lasted 5 days 22 hours for Soyuz and 9 days 1 hour for Apollo. They two spacecraft remained docked for 1 day 23 hours during that time. Between sharing meals, talking to President Gerald Ford and General Secretary Leonid Brezhnev, and speaking to each other in their respective tongues (Leonov joked that Tom Stafford’s Russian was a language of its own, Oklahoman) the crews had time to conduct an extensive scientific program. It included experiments on how microbes could pass between astronauts and cosmonauts, and a study of the solar corona from Soyuz, as Apollo maneuvered to eclipse the sun for it.

The mission also set a record for the oldest person in space. Deke Slayton had been selected as one of the seven original Mercury astronauts in 1959, but was grounded soon after due to a heart condition. By the 1970s his condition improved and, being head of NASA’s astronaut office, he selected himself for ASTP. He was 51 at the time. The title for the oldest person in space has since changed hands several times and is currently held by John Glenn, who was 77 at the time of his 1998 Discovery voyage to the International Space Station.



The Apollo-Soyuz flight left a lasting legacy of joint space exploration that survived the hostilities of the 1980s and continues to this day at the International Space Station.