projectile at more than the speed of sound in the ambient conditions. Hybrid electrothermal light-gas gun The hybrid electrothermal light-gas gun works on similar principles of the standard light-gas gun, but adds an electric arc to heat the light gas to a higher temperature and pressure than the piston alone. The arc is applied in the chamber containing the light gas, raising the temperature and pressure to the point where the gas both breaks the bursting disk and ignites the propellant behind the piston, which is perforated to allow ignition. The resulting combination of electrical heating and piston compression provide higher pressures and temperatures, resulting in more power and a higher potential speed than a standard light-gas gun. Impact profile When the projectile fired by a light-gas gun impacts its target, the pressure applied depends upon the mass of the projectile and the surface area, or cross-section, over which the impact force is distributed. Because air-launched projectiles experience friction with air molecules, drag increases proportionally to increased projectile surface area, which results in slower velocities the larger the surface area of a projectile is. As such, a dense and narrow projectile will apply more pressure overall than a light and wide one. Looking at constant cross-sectional projectiles, researchers have recently begun to vary their projectiles' density as a function of length. Since the projectiles travel at a known velocity, changes in density as a function of length have a predictable relationship to the impact pressure applied as a function of time. With materials in a wide range of densities (from tungsten powder to glass microspheres) applied in thin layers, carefully made projectiles can be used in constant-pressure experiments, or even controlled compression–expansion–compression sequences. See also Combustion light-gas gun, a high-velocity gun that uses combusted gas as propellant. Ram accelerator, a high-velocity gun that uses different principles to achieve similar projectile velocities. Shock tube, a tool used to demonstrate the properties of very high speed gases. Voitenko compressor, a shaped charge driven device which uses hydrogen gas to accelerate thin disks up to about 40 km/s. Super High Altitude Research Project Space gun References External links Lawrence Livermore National Laboratory's gas gun QuickLaunch, aka TekLaunch, plans to commercialize a 1 km hydrogen gun to launch fuel to low earth orbit Test Sequencer and high-speed camera controller with real-time reaction to hypervelocity events and trigger prediction capabilities Ballistics Space guns