What happens if a firearm is fired in orbit?


I get asked this question quite often and, finally, I decided to write an article, as I see that there are several common misconceptions about this topic.

Actually, I did. Although this information is readily available, it is little known. In the late 1960s, Soviet space stations of the Almaz series operated in orbit. These stations were armed with a 23 mm Nudelmann-Richter aircraft cannon. In theory, such a gun can fire up to 2600 rounds per minute.

The cannon was at the station to defend against potential attempts to «hijack» the station. Suspicions of an attempted hijacking arose after the United States began developing a fundamentally new type of spacecraft, the Space Shuttle, in 1967.

As it turned out, the design dimensions of the shuttle, as well as the calculated payload, which the shuttle could deliver from orbit to the Earth, approximately corresponded to the mass and dimensions of the Almaz series stations.
And although the dimensions of the cargo compartment and the carrying capacity of the shuttles were explained by their intended purpose — the launch of communication satellites into orbit, as well as modules for assembling space stations, it was decided to equip the station with a protection system.

The orbital cannon fired only once — on January 24, 1975. On this day, the Salyut-3 station was to be decommissioned. The last crew left the station barely on July 19th. The MCC decided to test the cannon in order to understand what effect the recoil would have on the station itself.

In total, the station fired three rounds within one minute, firing 20 shells. Simultaneously with the start of the line, the station’s engines were turned on in order to compensate for the recoil.

As reported, the start of the engines could not fully compensate for the recoil and as a result of the shots, the height and angular momentum of the station changed slightly. If the station were to remain in orbit, then after the firing, it would have been necessary to turn on the engines again to correct the orbit parameters, but since the station still had to be decommissioned within a few hours after the firing, this did not really matter.

Not really. To find an object in low Earth orbit, it must move at a speed of about 7.7 km / s. In order to overcome the gravity of the Earth and set off to fly through the Solar System, the bullet must reach the second cosmic velocity, which is approximately 11 km / s, i.e. the bullet should gain an additional speed of approximately 3.22 km / s.

No modern firearm can give a bullet or projectile this speed. So, for example, the average speed of bullets from a firearm is 0.5-0.7 km / s (for example, in the AK-47, the speed of a bullet at the exit from the barrel is 715 m / s). Of course, in orbit, this speed will be higher, since the bullets will not have to overcome air resistance, but still they will not be able to accelerate to the second cosmic speed.

So the projectiles fired from the Salyut-3 station from the NR-23 cannon did not leave low-earth orbit and quickly burned out in the atmosphere.

This is not entirely misleading. Of course, the law of conservation of momentum has not been canceled. A bullet fired from, for example, a rifle will give the astronaut an impulse and this will change his speed. There are no questions about that.

Questions arise rather in the ability to direct their movement with the help of shots. Of course, when firing from a firearm, the astronaut’s speed will change, but if you set the task for the astronaut to move from point A to point B located 100 meters away using only the recoil of the weapon, as an accelerator, then nothing will come of it, and if it does, then only by chance.

The fact is that the shot with a very high probability will not push the astronaut in the desired direction, but will spin him around its axis. Unless, somehow, the astronaut manages to fix the butt of the weapon exactly opposite his center of gravity. It is very difficult to do this in a spacesuit in zero gravity, so the result will still be poorly predictable.

These are the three main misconceptions about open space shooting. Well, in general, we are all for peaceful science and against the militarization of outer space.