Cycle selection and performance evaluation of tripropellant engines with LOX/CH₄/LH₂ and LOX/RP₁/LH₂ combinations

Tri-propellant engines are concepts which are suitable to take advantage of both high density impulse in low altitude and high specific impulse in high altitude application. A tripropellant engine in a SSTO mission operates in two modes. In Mode-1, all the three propellants i.e., LOX/LH₂ and RP1 or CH₄ are used by the engine and LOX/LH₂ in Mode -2 which provide high specific impulse. A study was conducted to evaluate future engine concepts using tripropellants. In this study, performances of engines with tripropellant combinations like LOX/ CH₄/LH₂ and LOX/RP1/LH₂ are evaluated. Different engine cycles were evaluated by adhering to consistent design practices and technologies and most suitable engine configurations are derived based on merits of performance in both the modes of operation.