Overview

Probably no single factor constrains the design of a space vehicle and the execution of its mission more than does the state of the art in propulsion technology. Ascent propulsion capability, together with the physical limitations imposed by celestial mechanics, sets the limits on payload mass, volume, and configuration that bound the overall design. The economics of space flight and our progress in exploiting space are driven inexorably by the cost per kilogram of mass delivered to orbit. Mankind's reach in exploring interplanetary space is limited by the energy available from current upper stages. Though the advent of the space shuttle has expanded many of the boundaries of the spacecraft design environment, it is still true that the scope of most space missions is ultimately set by propulsion system limitations.

Yet, despite its importance, ascent propulsion is probably the factor over which a spacecraft designer has the least control. Except for those involved directly in the areas of rocket engine, booster, or upper-stage design, most aerospace engineers will be in the position of customers with freight to be moved. A limited number of choices are available, and the final selection is seldom optimal for the given task, but is merely the least unsatisfactory. Rarely is a particular mission so important that a specific engine or launch vehicle will be designed to fit its needs. Indeed, there have been few boosters designed for space missions at all; most are converted Intermediate Range Ballistic Missiles (IRBM) and Intercontinental Ballistic Missiles (ICBM)...