But in the wake of the Apollo Moon landings, the United States and the Soviet Union both backed off, and began favoring policies of détente, or an easing of tensions, on and off Earth.

One of the most fascinating byproducts of this geopolitical shift was the Apollo-Soyuz Test Project (ASTP), the first collaborative space mission between these two initial space powers, or any nations for that matter. The mission objective was to dock the American Apollo command/service module with the Soviet Soyuz capsule in orbit, allowing two Soviet cosmonauts and three American astronauts to share a multinational orbital habitat, built from the most iconic spacecraft of their respective nations.

It all went down 41 years ago Sunday, on July 17, 1975. Both vehicles had been launched within seven hours of each other on July 15, and had spent the previous two days meandering over to the meetup point, about 140 miles over continental Europe.