Evolution of Reaction Control Engines for U.S. Manned Spacecraft

Abstract

Recent manned-spacecraft achievements have highlighted the importance of small reaction-control rocket engines in the successful accomplishment of such missions. Successive generations of U.S. manned spacecraft — Mercury, Gemini, and Apollo — have utilized reaction-control engines of increasing sophistication and capability. As missions have become longer and more complicated, a corresponding improvement has been required in engine characteristics such as operating life, minimum impulse bit, duty cycle flexibility, pulse performance, and reliability.

In this paper, the reaction-control engines used on Mercury, Gemini, and Apollo are described, and significant design characteristics and performance parameters are compared. In-flight experience is also discussed, to the extent of data availability.