System Study of Slush Propellants for Future European Launch Vehicles

Usually cryogenic propellants in launch vehicles are stored at the normal boiling point, but the density can be increased by subcooling the propellant. In its most extreme form, this results in a mixture of solid and liquid propellant: the slush propellants. First, the possibility of employing slush fuels within the upper stages of prospective European launchers (Ariane 6 and Vega-E) is evaluated. Three methods of implementation are discussed and compared. In addition, their effect on possible future European launchers with a reusable Vertical Takeoff and Vertical Landing (VTVL) first stage are also investigated. While the application to existing designs only yields small improvements, results for the Reusable Launch Vehicles (RLV) show that the total mass of the launcher for the same payload could be reduced by up to 23 %. While not all complications of densified propellants are solved at this point in time, the potential for the improvement of future launch systems is substantial enough to warrant future investigation.