This illustration depicts a configuration of the Soyuz spacecraft for the Apollo-Soyuz Test Project (ASTP). The ASTP was the first international docking of the U.S.'s Apollo spacecraft and the U.S.S.R.'s Soyuz spacecraft in space. For this project, the Soviets built another in their continuing series of Soyuz space capsules. The U.S. used the Saturn IB Apollo capsule. A joint engineering team from the two countries met to develop a docking system that permitted the two spacecraft to link in space and allowed the crews to travel from one spacecraft to the other.