Work-in-Progress: Asteroid Gun

[afrodri]

This is from a work-in-progress book of space equipment in the Hive, Queen, and Country setting. Any comments welcome!



Eanraig's Gun, a prototypical 'Asteroid Gun', side view

During the 'Asteroid Fever' period (1875-1876), a new breed of improvised recoilless weapon appeared in the innumerable 'claim jumper wars' – small skirmishes fought between rival mining crews on dozens of asteroid sites. Many of these guns were simple improvised devices cobbled together from spare parts. They often presented as much danger to the user as to the target.

However, many asteroid miners were skilled engineers with access to good machine tools and materials. The basic operation of a recoilless rifle is quite like a solid rocket – both consist of a solid propellant encased in a pressure vessel with a converging/diverging nozzle at one end. The individual components and operational theory would be quite familiar to any decent space mechanic. Some of the weapons developed were highly effective, and some could even be considered elegant.

Eanraig's Gun is an example of a higher quality gun. Developed by an unknown Scottish engineer for an unknown 'Jump War', its basic design was frequently copied, and variants can still be found for sale on Earth and Venus. Notably, Eanraig-like guns were used in the Big Horn Asteroid War. It's design and materials hint at its semi-improvised nature. A close inspection reveals handle grips covered in Silk+CAB/Al salvaged from an M1890 Hard Suit, truss spacers from a Blohm+Voss Hull Repair Kit, and tubing from a Chester Pipe and Tube heat pipe.


Eanraig's Gun, Perspective View

Behind the 54cm smoothbore barrel is a more or less conventional breech and gas-powered autoloading action. To reduce recoil, a duct is connected slightly ahead of the chamber. This duct directs a portion of the combustion gases toward the rear of the gun and an angled converging/diverging nozzle. The duct converges to a 4mm throat and then expands to a 20mm angled nozzle, accelerating the combustion gasses to almost 4500m/s. This cancels out almost 95% of the recoil. A gas diverter in the nozzle reduces the recoil further, to the point that the gun actually has a slight forward propulsion.  About halfway down the barrel a 2mm orifice diverts some gas back to the action to load the next round, allowing a sustained rate of fire of 170 r/min. To reduce heat, a radiator, water sheath, and gas separator system is included. The gun uses the readily available .45-70 "Trapdoor Springfield" cartridge. 32 of them are housed in an underslung double drum magazine.

Though a beautiful piece of in-the-field engineering, Eanraig's Gun is also a fiendishly complicated beast with all the complexities of a gas-powered automatic, a steam separator, a recoilless rifle, dual drum magazine, and an oddball assortment of parts. It's the sort of gun an engineer would love, but which also requires a lot of maintenance and is prone to failure.