Utilization and Loss of Available Energy for Chemical Rockets in Atmospheric Flight

Abstract

The physical basis and application of the fundamental relationship governing the balance and utilization of available energy for a chemical rocket operating within the atmosphere are described. The relative contributions of the thermochemical availability and the kinetic energy of the stored propellant to the overall energy availability are shown. There are optimal flight velocities for which 1) overall entropy generation is minimized and 2) effectiveness of the conversion of available energy to vehicle force power is maximized. The fundamental impacts of entropy generation within a rocket engine flowfield on energy utilization and thrust/performance characteristics of a rocket-powered vehicle are studied analytically. Highly nonlinear coupling between entropy generation in the engine and entropy generation in the wake is observed; this is true as well as for other energy utilization parameters, such as thrust losses. Representative energy utilization-based performance maps for selected (example) legacy rocket systems across altitude/flight velocity confirm the theoretical results. Propulsion models and available flight data are then used to provide the time evolution of energy utilization characteristics for the flight of Apollo 11 (Saturn V).