A needlegun is a weapon featured in many works of fiction that fires slivers of metal or ice resembling common sewing needles. There have been some attempts to engineer working needleguns based upon this fiction, but these have not produced generally useful weapons.
The advantages of a needlegun over other projectile weapons are compact size, high repeat rate and ultra-high muzzle velocity. A needlegun takes advantage of kinetic energy to allow a low-recoil delivery system to inflict damage to a target; recoil is governed by momentum, which is velocity times mass, while damage inflicted is governed by kinetic energy, which is the square of the velocity times one half the mass. By having a high speed and a small mass, recoil is minimized at little cost to kinetic energy.
Most theoretical needlegun designs are solid state, meaning that the delivery system has no moving parts other than the projectile itself. For instance, see coilgun and railgun.
