Design concept for LOX/hydrocarbon tripropellant booster engine

The design concept for a LOX/hydrocarbon tripropellant booster engines is discussed. The engine design is for the gas generator cycle with liquid methane, liquid oxygen, and liquid hydrogen as propellants, the latter greatly reducing risks associated with the high-pressure reusable hydrocarbon booster engines. The design features high combustion stability and high efficiency. The excellent cooling capability of liquid hydrogen was established in several operational engine designs. Multiple design diagrams are included.