Features of using guns in combat. Using guns in space differs substantially from using them in an atmosphere and under gravity. This matters both in battle and when designing or arming a ship.
Without an atmosphere, a fired projectile travels at an unchanged speed equal to its muzzle velocity until it hits something or enters a gravitational field. Its firing range is therefore practically infinite. Guns have a dispersion parameter made up of three factors. Aiming error comes from play in the mechanisms and unaccounted temperature compensation. Natural dispersion depends on barrel condition and ammunition quality. Basic dispersion depends on the barrel's design. At a distance of a few kilometers, these factors may combine to produce an error of several meters; at 100 kilometers, the error will be hundreds of meters. Gun barrels must be warmed up before firing or kept warm continuously. In a vacuum, barrels cool more slowly than in an atmosphere, which significantly affects the rate of fire. For example, after a one-second burst from a rapid-fire six-barrel gun, it will need longer to cool to avoid overheating unless it has artificial cooling systems. Recoil must be countered by the attitude-control systems, consuming fuel or energy stored in flywheels. A projectile cannot be stabilized by the atmosphere, so smoothbore guns are effective only within limits. A rifled barrel stabilizes a projectile by spinning it, makes subsequent course correction harder if the projectile is guided, and reduces muzzle velocity for comparable ammunition. The blast effect of a shell exploding in space is practically absent because there is no atmosphere and therefore no shock wave, which would be the main damaging effect in that scenario. Fragments, however, will be quite effective. The armor penetration of armor-piercing shells may vary with the temperature of the enemy's armor and of the projectile itself.