NASA Office of Logic Design

NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.

NASA Technical Memorandum 4322

NASA Reliability Preferred Practices for Design and Test

NASA Reliability and Maintainability Steering Committee
National Aeronautics and Space Administration
Office of Safety and Mission Assurance
Washington, D.C.

1991 (Updated with Supplements 1(1992), 2 (1993), 3 (1994), 4 (1995), and 5 (1995)




This manual is produced to communicate within the aerospace community design practices that have contributed to NASA mission success. The information presented has been collected from various NASA field centers and reviewed by a committee consisting of senior technical representatives from the participating centers.


The information presented in this manual represents the "best technical advice" that NASA has to offer on reliability design and test practices. The practices contained in this manual should not be interpreted as requirements, but rather as proven technical approaches that can enhance system reliability. Application of the practices and guidelines is strongly encouraged, but the final decisions regarding applicability resides with the particular program or project office The manual is divided into two technical sections. Section II contains reliability practices, including design criteria, test procedures, and analytical techniques that have been successfully applied on previous space flight programs. Section III contains reliability guidelines, including techniques currently applied to space flight projects where insufficient information exists to certify that the technique will contribute to mission success.


Experience with NASA's successful extended duration space missions shows that four fundamental elements contribute to high reliability: 1) understanding stress factors imposed on flight hardware by its operating environment; 2) controlling the stress factors through selection of conservative design criteria; 3) appropriate analysis to identify and track high stress points in the design (prior to qualification testing or flight use); and 4) careful selection of redundancy alternatives that will provide the necessary function(s) should failure occur. This manual is provided to encourage design, test, and reliability engineers to give careful attention to both redundancy and stress management during the design and development of space flight systems.


The practices and guidelines contained in this manual serve as a mechanism for communicating the latest techniques that contribute to high reliability. This publication will be revised periodically to include additional practices/guidelines, or revisions to information (as additional technical data becomes available). Contributions from aerospace contractors and NASA Field centers are encouraged. Any practice, guideline or technique that appears appropriate for inclusion in this manual should be submitted for review. Submissions should be formatted identically to the practices and guidelines in this manual and sent to the address below for consideration:

National Aeronautics and Space Administration
Code Q
300 E Street, SW
Washington, DC 20546

Organizations submitting practices/guidelines that are selected for inclusion in this manual will be recognized in the lower right-hand corner of the published item.


This section contains Reliability Design Practices that have contributed to the success of previous space flight programs. The information presented in this section is for use throughout NASA and the aerospace community to assist in the design and development of highly reliable equipment and assemblies. The practices include recommended analysis procedures, redundancy considerations, parts selection, environmental requirements considerations, and test requirements and procedures.


The format for the reliability practices is shown below:


Practice: A brief statement of the process or procedure with emphasis on the reliability aspects.

Benefit: A concise statement of the technical improvement realized from implementing the practice .

Programs That Certified Usage: Identifiable programs or projects that have applied the practice.

Center to Contact for More Information: Source of additional information, usually the sponsoring NASA Center. (See "CENTER CONTACTS," paragraph G.)

Implementation Method: A brief technical discussion that is not intended to give the full details of the process, but rather to provide a design engineer with adequate information to understand how the practice should be used.

Technical Rationale: A brief technical justification for the use of the practice.

Impact of Nonpractice: A brief statement of what can be expected if use of the practice is avoided.

Related Practices: Identification of other topic areas in the manual that contain related information.

References: Publications that contain additional information about the practice.


In the preparation of this manual, the dedication, time, and technical contributions of the following individuals are appreciated. Without the support of their individual centers, and their enthusiastic personal support and willingness to serve on the NASA Reliability and Maintainability Steering Committee, the practices and guidelines contained in this manual would not be possible. All of the NASA Centers were invited to contribute to this manual. The people listed below may be contacted for more information about these practices and guidelines.

Mr. Dan Lee
Ames Research Center
MS 240A-3
P.O. Box 1000
Moffet Field, California 94035

Mr. Jack Remez
Goddard Space Flight Center
Code 302 Bldg 6 Rm S233
Greenbelt, Maryland 20771

James Arnett
Jet Propulsion Laboratory
California Institute of Technology
MS 301-456, Office 505
4800 Oak Grove Drive
Pasadena, California 91109

Mr. Malcolm Himel
Lyndon B. Johnson Space Center
Bldg 45 Rm 618A Code NB2
Houston, Texas 77058

Mr. Leon Migdalski
Kennedy Space Center
Kennedy Space Center, Florida 32899

Mr. Vernon W. Wessel
Langley Research Center
MS 421, Bldg. 1162A
5 Freeman Road
Hampton, VA 23681-0001

Mr. Michael Langley
George C. Marshall Space Flight Center
CR40 Bldg 4203
Marshall Space Flight Center, Alabama 35812

Mr. Ronald Lisk
NASA Headquarters
Code Q
300 E Street, SW
Washington, DC 20546

Mr. Vincent Lalli
Lewis Research Center
MS 501-4 Code 0152
Brookpark Road Cleveland, Ohio 44135

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