Rail Guns and Gauss Guns
Current weapons rely on chemical reaction to propel the projectile. This reaction results in rapid expansion of gasses which, in closed space, results in explosion. In barrel of the gun, explosion …
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Current weapons rely on chemical reaction to propel the projectile. This reaction results in rapid expansion of gasses which, in closed space, results in explosion. In barrel of the gun, explosion has only one exit – though the barrel itself, pushing the bullet along the way. Longer barrel allows gasses longer time to affect the projectile, thus increasing muzzle velocity and projectile’s kinetic energy. This, all other factors being equal, results in longer range and greater penetrative power for any given range, as well as greater stability which leads to better accuracy. For assault rifles, muzzle velocities range from 715 m/s (AK-47) to 960 m/s (M-16), or generally between 600 and 1 000 meters per second. Sniper rifles have similar muzzle velocities, but heavier projectiles and longer barrels. Specifically made suppressed weapons and ammunition are designed to keep muzzle velocity below the speed of sound in order to reduce the sound signature, but have to sacrifice range to do so. Overall, for the same ammunition, longer barrel means longer range and greater lethality.
These same principles are true for artillery. Modern 120 mm tank guns have barrel length of 44 to 55 calibers in order to improve lethality. For Rheinmetal 120 mm gun, increase in barrel length from 44 to 55 calibres led to increase in muzzle velocity from 1700 to 1800 m/s, and 14% increase in muzzle energy.
Regardless of the barrel length, however, chemical weapons have a theoretical upper limit of 1400 – 2000 m/s. Up to 3 500 m/s is possible with guns that are built to achieve highest theoretical projectile velocities, but these are not practical as weapons. This limit is caused by the limit to expansion of hot gasses which propel the projectile to begin with: projectile cannot move faster than the gasses which propel it. There are three possible solutions to this. First is to equip the projectile with inbuilt rocket which would activate once it leaves the barrel and provide further acceleration. Effectiveness of this however will be limited depending on range to target and burn rate and time of the rocket. Second is to get rid of chemical projectiles altogether.
It should be noted however that solid rod penetrators have hydrodynamic limit at 4 – 5 km/s and optimal velocity of 3 km/s, but penetration picks up again at velocities beyond 6 km/s.