TABLE OF CONTENTS An important measure of the worth of any engineering system is its reliability, which we define as the probability that the system will function as expected. Space systems tend to be quite expensive as well as unusually complex and are not repairable other than in highly unusual circumstances, and so it is both extremely important and very difficult to ensure that a spacecraft is highly reliable. Attaining the desired degree of space vehicle reliability, and trading incremental improvements in reliability against incremental costs, is the overall responsibility of the spacecraft system engineer. As with other aspects of system design, he will be aided in this effort by a knowledgeable specialist, in this case a safety, reliability, and quality assurance (SR&QA) engineer. As one of the so-called "ilities" (including such disciplines as maintainability, producibility, and operability), reliability analysis often lacks the visibility associated with seemingly more prestigious specialties. However, the cost of unreliability, both in lives and property damage, can be far greater than that of a suboptimal, but generally workable, design in almost any other subsystem.
In this chapter, we will develop an understanding of the tools and methods of reliability analysis and illustrate the use of these methods through the use of relatively simple examples. To do this, we begin with a treatment of the fundamentals of probability theory and the analysis of random variables. With these tools, the system engineer will be equipped to deal with the most common features of engineering reliability analysis. However, we...
