“The combustion system heats the hydrogen to 1,430˚C (2,600˚F), which increases the gas pressure by 500%. An operator then opens a valve to allow the hot, pressurized hydrogen into the 1100-meter-long barrel of the gun, where it instantly expands, shooting the projectile out and into space. As soon as the payload has left, an iris at the end of the barrel closes to capture the hydrogen for re-use. Once the projectile is launched, a small rocket engine then boosts the payload into a low-Earth orbit.“