Electric Propulsion

Abstract

For space exploration we not necessarily bigger,For space exploration we not necessarily bigger, need rockets that are better, than those being developed.need rockets that are better, than those being developed.Propulsion is a means of producing motion, or, more accurately, changes in momentum. Propulsion is also required to maintain momentum in the presence of resistive or retarding forces. These functions of a propulsion system require the expenditure of energy. If this propulsive energy must be carried by the vehicle, as is the case with most systems, then the amount of change in momentum, or the length of the period during which a given momentum can be maintained, is determined by the form and amount of the energy carried along. Ideally, this energy should be in a form which yields the maximum useful propulsive energy per unit of weight.Other factors, however, such as development and operating problems and costs, or the adequacy of existing systems, may argue against use of systems having the highest possible energy per unit weight. In the case of aircraft, for example, the use of nuclear power would have greatly increased the energy per unit weight, but it involved many difficult and costly problems of development and operation. Its advantages, in terms of much greater range and duration of flight, were overbalanced by these disadvantages, and by the fact that kerosene-burning aircraft were already available with range, speed, and Propulsion is a means of producing motion, or, more accurately, changes in momentum. Propulsion is also required to maintain momentum in the presence of resistive or retarding forces. These functions of a propulsion system require the expenditure of energy. If this propulsive energy must be carried by the vehicle, as is the case with most systems, then the amount of change in momentum, or the length of the period during which a given momentum can be maintained, is determined by the form and amount of the energy carried along. Ideally, this energy should be in a form which yields the maximum useful propulsive energy per unit of weight.Other factors, however, such as development and operating problems and costs, or the adequacy of existing systems, may argue against use of systems having the highest possible energy per unit weight. In the case of aircraft, for example, the use of nuclear power would have greatly increased the energy per unit weight, but it involved many difficult and costly problems of development and operation. Its advantages, in terms of much greater range and duration of flight, were overbalanced by these disadvantages, and by the fact that kerosene-burning aircraft were already available with range, speed, and flight durations which were adequate for most applications of interest.For space missions, if man would be satisfied with exploring the moon, or even with settling a colony on it, there would be little incentive to develop propulsion systems with much greater energy per unit weight than the chemical rockets now in use or under development. Some economies mi...