In 1975, Soviet Union sent a cannon to space and tested it from Salyut 3 station, just six months before US and Soviet astronauts met in orbit for the Apollo-Soyuz mission during the Cold War

In January 1975, the Soviet Union fired a 23mm cannon from its Salyut 3 space station, testing a weapon that had been designed to protect the spacecraft from a possible attack in orbit. The test came just months before American astronauts and Soviet cosmonauts would meet in space for the historic Apollo-Soyuz mission.

Salyut 3 belonged to the Soviet Almaz programme, a military space station project that the Soviet Union presented publicly as part of the Salyut series. The station carried reconnaissance equipment as well as defensive systems, including the rapid-fire cannon. The Soviet Union kept much of the programme secret during the Cold War.

Why did the Soviet Union put a cannon in space?

The Soviets were not primarily preparing to shoot down distant satellites. They feared that an enemy spacecraft could approach one of their military stations and potentially attack, damage or capture it.


The Almaz programme emerged partly from Soviet concerns about American military space projects. Soviet planners considered the possibility that an American spacecraft could approach a Soviet military station in orbit, making some form of close-range defence necessary. The cannon became part of that defensive system.

The weapon was a modified version of the NR-23 aircraft cannon. The Space Review reports that Salyut 3 carried the gun as part of its defensive equipment and that the Soviet Union successfully fired it during the station's final moments in orbit.

The cannon had a major problem

Putting a gun in space created a problem that does not exist in the same way on Earth. The cannon could not simply turn towards a target like a modern turret.

The weapon remained fixed to the station, meaning the entire spacecraft had to turn to point the cannon in the required direction. That made the system slow and difficult to use against a moving spacecraft.

Firing the weapon also produced recoil. On Earth, the ground absorbs some of the effects through the weapon and its surroundings. In orbit, the recoil could change the spacecraft's movement and orientation.

Because of those concerns, the Soviets did not fire the cannon while cosmonauts occupied Salyut 3. The Space Review reports that they waited until the station's final phase in orbit, when the crew had already left, before conducting the firing test.

NASA's historical record confirms that Soviet controllers commanded Salyut 3's retrorockets to begin its descent on January 24, 1975, after about seven months in orbit. The station subsequently re-entered over the western Pacific.

The test happened just months before Apollo-Soyuz

The timing makes the story particularly striking.

While the Soviet military space programme was testing an orbital weapon, the United States and Soviet Union were preparing for one of the most symbolic moments of the Cold War. On July 15, 1975, an American Apollo spacecraft and a Soviet Soyuz spacecraft launched for the Apollo-Soyuz Test Project. Two days later, they docked in orbit.

The mission brought together three American astronauts, Thomas Stafford, Vance Brand and Donald Slayton, and two Soviet cosmonauts, Alexey Leonov and Valery Kubasov. The crews spent nearly two days carrying out joint activities and experiments after docking.

NASA describes Apollo-Soyuz as the first international partnership in human spaceflight. The mission tested whether spacecraft from the two rival nations could rendezvous, dock and work together in orbit, while also creating a possible framework for future rescue missions.

Yet only months earlier, the Soviet Union had demonstrated a very different side of the Cold War in space.

The cannon on Salyut 3 ultimately proved far less practical than its designers might have hoped. Its fixed position, limited usefulness against distant targets and the problems caused by recoil made it an awkward defensive system. Still, the January 1975 test remains one of the strangest examples of how the Cold War rivalry extended beyond Earth, with the Soviet Union actually firing a conventional cannon from a spacecraft.