Mission Effectiveness Model for Manned Space Flight

The most objective manner in which to measure the ability of a system to perform against a specified mission is to estimate the average probability of successfully completing that mission. This probability of success is defined as the Mission Effectiveness of the system. In general, when specifications are stated for military or space application equipment, the reliability aspect far outweighs all other considerations when in reality it is only one important factor in the ability of the system to complete a satisfactory performance of its assigned mission. In this paper the importance of other factors are illustrated by developing a model which estimates mission effectiveness. This model is developed for a system which undergoes scheduled checkout and up-dating after relatively long standby periods during which it is expected to respond to a random demand. The effects upon mission effectiveness of noninstantaneous and imperfect failure detection and repair are considered, as well as system accuracy. The model for the mission as described is found to be a Markov Chain with one absorbing barrier. The advantage of this type of model is that once the first transition matrix is derived, the factors that enter into mission effectiveness can be readily and automatically extracted. The principal result of the paper is in demonstrating the application of this technique to generate a realistic system model for mission effectiveness. This technique is quite general and as such is applicable to most types of military and space missions.