Illustration Of Soviet Almaz Space Station

NASA, via Wikimedia Commons

Officially, space is a weapons-free zone. As spelled out in the United Nations Outer Space Treaty, the heavens beyond earth are to remain free of weapons, weapons testing, and fortification. Both the United States and The Soviet Union signed the treaty, but it's hard for weapons inspectors to go to space to confirm. Rumored for decades, a 1970s Soviet space cannon was earlier this year finally revealed on Russian television.

Originally built for Russia's Tu-22 Blinder supersonic bomber, the R-23 gun was mounted in the plane's tail as a deadly surprise for any pursuing jet fighters. The gas-powered gun could fire 23mm rounds incredibly quickly. It's a variant of this gun that made it to space, on board one of the Soviet Union's Almaz military reconnaissance space stations.

From Anatoly Zak, writing at Popular Mechanics:

Only after the fall of the USSR did Russian sources revealed that the cannon had actually fired in orbit. It happened on Jan. 24, 1975, onboard the Salyut-3 space station. Worried about how firing a giant cannon would impact the outpost itself, Soviet officials scheduled the test firing just hours before the planned de-orbiting of the station, and long after the departure of the crew on July 19, 1974. The outpost ignited its jet thrusters simultaneously with firing the cannon to counteract the weapon's powerful recoil. According to various sources, the cannon fired from one to three blasts, reportedly firing around 20 shells in all. They burned up in the atmosphere, too.

Read the full story there, and be sure to check out the painstakingly rendered images of the gun itself.