Rocket Propulsion Elements, 9th Edition

CHAPTER 11ENGINE SYSTEMS, CONTROLS, AND INTEGRATION

In this chapter, we examine propellant budget, performance of multiple or complete rocket propulsion systems, designs of liquid propellant rocket engines with pressurized or with turbopump (TP) feed systems, engine controls, engine calibration, system integration, and system optimization. Some content also applies to solid propellant motors and hybrid propulsion systems.

11.1 PROPELLANT BUDGET

In all liquid propellant rocket engines the amount of propellant inserted into the vehicle tanks is always somewhat greater than the nominal amount of propellant needed to accomplish the intended mission. The extra propellant is needed for purposes other than providing thrust (e.g., for auxiliary functions like valve actuation), to compensate for changes from engine to engine (such as dimensional tolerances causing slight changes in flow), for uncertainties of engine construction and for minor variations in the flight plan. A propellant budget represents the sum of all the propellant utilization categories and losses in an engine—11 are identified below. Such a budget defines how much propellant has to be loaded and is aimed at minimizing the amounts of extra propellant.

1. Enough propellant must be available for achieving the required vehicle velocity increase and any nominal set of attitude control maneuvers for the specified application of the entire flight vehicle or stage. The nominal velocity increment is defined from a system analysis ...