Apollo-Soyuz at 50: The Cold War space hug that nearly ended in gasping horror

It's been 50 years since the Apollo program marked its final hurrah, culminating in a historic mission that saw the last launch of an Apollo vehicle and a subsequent docking with a Soviet Soyuz spacecraft in orbit. This remarkable collaboration between the United States and the Soviet Union showcased détente in action, but also came perilously close to disaster.

The first US-Soviet joint mission was aptly named the Apollo-Soyuz Test Project (ASTP). It marked the final opportunity for Deke Slayton, one of the original Mercury 7 astronauts, to fly before the first launch of the Space Shuttle in 1981. Slayton had been cleared to fly after being disqualified from the initial Mercury program due to a heart condition.

On the Soviet side, the mission featured Alexei Leonov, the first spacewalker, who would command the two-person Soyuz crew on what would be his final spaceflight. The Apollo spacecraft was accompanied by an S-IVB upper stage and a docking module, which was crucial to the mission's success.

The ASTP consisted of three main components: the Apollo spacecraft, a docking module, and Soyuz 19. The launches occurred on July 15, 1975, with the Apollo launching from Kennedy Space Center's Launch Complex 39B and the Soyuz taking off from Baikonur in the Soviet Union. Both missions took place just over seven hours apart.

The docking module was a critical component of the mission, as it allowed the Apollo and Soyuz spacecraft to connect without directly matching each other. The module functioned like an adapter, with the Apollo using its probe-and-drogue mechanism and the Soyuz employing its APAS mechanism. This ingenious design enabled the two spacecraft to dock successfully.

During the mission, the crews exchanged gifts, ate meals together, and gave televised tours of their vehicles. The moment when the hatches opened and the crew saw each other in space for the first time was a highlight of the mission for Leonov. "At that moment," he wrote, "I felt that everything I had been through in my career as a cosmonaut … had been worth it."

However, not everything went smoothly. The Apollo crew received some unexpected gifts from Leonov – tubes of borscht with vodka labels – which raised concerns among the Americans. When they took their first swigs, Leonov reassured them that he would show them how to drink safely.

The mission's second docking did not go as smoothly as the first. Slayton accidentally fired one of Apollo's side roll thrusters, causing both vehicles to shift off center and threatening a catastrophic depressurization. Fortunately, the issue was quickly corrected, and the incident remained hidden from the public.

But the challenges didn't end there. During re-entry, Apollo's reaction control systems (RCS) malfunctioned, filling the cockpit with toxic gas. The crew quickly realized the problem and shut down the RCS, but not before they were exposed to a lethal dose of the toxic substance.

The mission was a turning point for US-Soviet relations, showcasing the potential for cooperation in space exploration. Despite some initial concerns about the mission's politics, it marked a significant milestone in the development of international space collaboration.

Today, the legacy of the Apollo Soyuz Test Project serves as a testament to the power of scientific collaboration and the determination of astronauts from both sides. The mission may have come perilously close to disaster, but its success paved the way for future cooperation in space exploration.