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).

描述了在大气中运行的化学火箭的可用能量平衡和利用的基本关系的物理基础和应用。显示了热化学可用性和储存推进剂的动能对整体能量可用性的相对贡献。存在最佳飞行速度，1) 总熵产生最小化和 2) 可用能量转换为飞行器动力的效率最大化。分析研究了火箭发动机流场内熵产生对火箭动力车辆的能量利用和推力/性能特性的基本影响。观察到发动机中的熵生成和尾流中的熵生成之间的高度非线性耦合；对于其他能量利用参数（例如推力损失）也是如此。所选（示例）传统火箭系统在海拔/飞行速度方面的代表性基于能量利用的性能图证实了理论结果。然后使用推进模型和可用的飞行数据为阿波罗 11 号（土星五号）的飞行提供能量利用特性的时间演变。