SCORES: Developing an Object-Oriented Rocket Propulsion Analysis Tool

SCORES (SpaceCraft Object-oriented Rocket Engine Simulation) is an analysis tool being developed for conceptual-level spacecraft and launch vehicle design. Written in C++, SCORES provides rocket thrust and Isp for propulsion system trade studies. Common gateway interface scripts, written in Perl, provide an interface with the World Wide Web. The design parameters used in SCORES are mixture ratio, chamber pressure, throat area, and expansion ratio, making SCORES effective in multidisciplinary design optimization. This paper describes the current status in the development of SCORES, compares chemical equilibrium results against accepted equilibrium codes STANJAN and CEA, compares engine thrust and Isp predictions against available engine data for nine rocket engines, and discusses areas for future work. SCORES accurately predicts equilibrium mole fractions and adiabatic flame temperature over a wide range of operating conditions within 0.5%. Uncorrected errors of less than 10% within SCORES engine thrust and specific impulse calculations are within acceptable tolerances for use in conceptual-level design. Statistically correcting the performance predictions reduces these errors appreciably and provides the designer with additional information, the confidence interval of the calculations. NOMENCLATURE β multiplier ε nozzle area ratio (A e /A t) γ ratio of specific heats λ k element potential (G/RT) A area (in 2) c* characteristic velocity C f thrust coefficient Cp constant-pressure specific heat G Gibbs free energy g c unit conversion factor˜g j (G/RT) for species i h specific enthalpy Isp specific impulse (sec) ˙ m mass flow rate (lb./sec) MW molecular weight (kg/kg-mole) N i moles of species i n kj element k atoms in species j O/F oxidizer to fuel ratio p pressure (psia) R gas constant s specific entropy T temperature (K) x j mole fraction of species i Subscripts a atmospheric act actual value c combustion chamber calc calculated value e nozzle exit AIAA 98-3227 2 M perfect gas mixture t nozzle throat thr thrust