Lessons from the military: Applications, environments, and servicemen pose reliability challenges not found in commerce or industry

Reliability in military systems is complicated by many factors not usually encountered in commercial or industrial applications. Among them are the following constraints: • Military applications often require higher performance. To get it, designers must use advanced or revolutionary technology before the reliability of that technology has been proved. Nonmilitary systems, by contrast, are usually state-of-the-art, or evolutionary, products with a proven record of reliability. • Military system designers are often required to create a “perfect” design at an early stage. Nonmilitary system designers tend to use iterative approaches, in which they make many small changes to solve problems as they arise. • Military systems generally operate in harsh environments that have proved difficult to simulate under test conditions. The environments may include extremes of temperature, vibration, mechanical shock, humidity, or corrosive agents (such as sea water), as well as electromagnetic interference and nuclear radiation. The electromagnetic environment alone may have up to 100 different signals broadcast by enemy jamming systems or friendly forces. Experience has shown that some equipment in the field is only about one third as reliable as it was during final testing by the manufacturer. • The servicemenwho operate military systemsmaybe unusually error-prone. In the chaos of battle they are subjectto great stress, with accompanying lapses in performance. • The armed services are chronicallyshort of experienced operators and maintenance personnel in many areas, as well as reliability engineers. The services are confronted by chronically high turnover rates in personnel. • Manufacturers cannot always guarantee the reliability of spare parts or the adequacy of maintenance once the systemis in the field; some systemsmay be repaired with either unspecified parts or parts from various manufacturers, since the services are required by law to buy spare parts through competitivebids. • Military-gradedevicescost more than comparable commercial or industrial devices. They require specialmanufacturing, documantition, and testing procedures to ensure reliability and uniform quality. • Military procurement engineershave only minimal leverage in the semiconductorindustry. Military-grade integrated circuitsaccount for less than 10 percent of the industry's dollar sales, and they have not offered as stable a market as commerical items.