Performance Prediction Model for a High-Impulse Monopropellant Propulsion System

A performance model has been developed for use with a high-impulse, multistart monopropellant propulsion system. In developing the mathematical model, theoretical considerations plus empirical data correlations were employed to characterize the propellant tank blowdown, feed system operation, and thruster performance. The system model derivation involved the development of a set of differential equations which can be numerically integrated to predict propellant consumption, pressure decay, and thruster performance for selected mission profiles. The significant feature of the model is its ability to characterize catalyst bed changes with thruster life, enabling performance prediction for a hydrazine system with extensive capabilities and a 3 :1 blowdown pressure range. An accuracy of better than 2.0% has been demonstrated in system testing. Nomenclature A = area BI, B2, £3, B4 = nitrogen solubility coefficients C* = characteristic exhaust velocity CD = Venturi discharge coefficient E — Young's modulus of elasticity