The system engineer should be aware of some basic

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Unformatted text preview: es what activities will be undertaken in support of reliability engineering. The reliability engineer develops a reliability program considering its cost, schedule, and risk implications. This planning should begin during Phase A. The project manager/system engineer must work with the reliability engineer to develop an appropriate reliability program as Lunar Excursion Module (LEM) Reliability Part of the reliability engineer's job is to develop an understanding of the underlying physical and human-induced causes of failures, rather than assuming that all failures are random. According to Joseph Gavin, Director of the LEM Program at Grumman, "after about 10 years of testing of individual [LEM] components and subsystems, [NASA] found something like 14,000 anomalies, only 22 of which escaped definite understanding NASA Systems Engineering Handbook Integrating Engineering Specialties Into the Systems Engineering Process The Bathtub Curve For many systems, the hazard rate function looks like the classic "bathtub curve" as in the graph below. Because of burn-in failures and/or inadequate quality assurance practices,λ(t) is initially high, but gradually decreases during the infant failure rate period. During the useful life period, λ(t) remains constant, reflecting randomly occurring failures. Later, λ(t) begins to increase because of wearout failures. The exponential reliability formula applies only during the useful life period. many factors need to be considered in developing this program. These factors include: • • NASA payload classification. The reliability program's analytic content and its documentation of problems and failures are generally more extensive for a Class A payload than for a Class D one. (See Appendix B.3 for classification guidelines.) Mission environmental risks. Several mission environmental models may need to be developed. For flight projects, these include ground (transportation and handling), launch, • on-orbit (Earth or other), and planetary environments. In addition, the reliabil...
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This document was uploaded on 02/26/2014 for the course E 515 at University of Louisiana at Lafayette.

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