W..e_: NASA Technical Memorandum 4628 Recommended Techniques for Effective Maintainability A Continuous Improvement Initiative of the NASA Reliability and Maintainability Steering Committee December 1994 = # \ (NASA-TM-4628) RECOMMENOEO N95-31530 TECHNIQUES FOR EFFECTIVE MAINTAINABILITY. A CONTINUOUS IMPROVEMENT INITIATIVE OF THE NASA Unclas RELIABILITY AND MAINTAINABILITY STEERING COMMITTEE (NASA) 105 p H1/38 0060399 | w = J J Ira! J] ii U mmm mini mJ r - w J _J W IL u h_ PREFACE Current and future NASA programs face the challenge of achieving a high degree of mission success with a minimum degree of technical risk. Although technical risk has several . , w elements, such as safety, reliability, and performance, a proven track record of overall system effectiveness ultimately will be the NASA benchmark. This will foster the accomplishment of r mission objectives within cost and schedule expectations without compromising safety or w program risk. A key CharaCteristic of systems effeci_veness is the impiementation of appropriate levels of maintainability throughout the program life cycle. Maintainability is a process for assuring the ease by which a system can be restored to operation following a failure. It is an essential consideration for any program requiring ground n and/or on-orbit maintenance. TheiOffice of S_._ty"and Mission Assurance (OSMA) has undertaken a continuous improvement initiative to develop a technical roadmap that will provide a path toward achieving the desired degree of maintainability while realizing cost and schedule benefits. Although early life cycle costs are a characteristic of any assurance program, operational cost savings and improved system availability almost always result from __° a properlY administered maintainability assurance program. Past experience on NASA w programs has demonstrated the value of an effective maintainability program initiated early in the program life cycle. This memorandum provides guidance towards continuous improvement of the life cycle development process within NASA. It has been developed from NASA, Department of Defense, and industry experience. The degree to which these proven techniques should be w imposed resides with the project/program, and will require an objective evaluation of the applicability of each technique. However, each applicable suggestion not implemented may represent an increase in program risk. Also, the information presented is consistent with w OSMA policy, which advocates an Integrated Product Team (IPT) approach for NASA systems acquisition. Therefore, this memorandum should be used to communicate technical knowledge that will promote proven maintainability design and implementation methods resulting in the highest possible degree of mission success while balancing cost effectiveness and programmatic risk. w w Frederick D. Gregory Associate Administrator for Safety and Mission Assurance w w DEVELOPING ACTIVITY U The development of this technical memorandum has been overseen by the NASA Reliability and Maintainability (R&M) Steering Committee, which consists of senior technical representatives from NASA Headquarters and participating NASA field installations. This Committee exists to m provide recommendations for the continuous improvement of the R&M discipline within the NASA community, and this manual represents the best technical "advice" on designing and m operating maintainable systems from the participating Centers and the Committee. Each J technique presented in this memorandum has been reviewed and approved by the Committee. CENTER CONTACTS m Appreciation is expressed for the dedication, time, and technical contributions of the following M individuals in the preparation of thismanual. Without the support of their individual Centers, U and their enthusiastic personal support and willingness to serve on the NASA R&M Steering c-bmmittee, the capture oftlie m_inffinab_tytechniques _ofi/a_ned in this manual would not be possible. -" R All of the NASA Centers are invited to participate in this activity and contribute to this manual. The Committee members listed below may be contacted for more information pertaining to these i maintainability techniques. m Mr. Donald Bush Mr. Leon Migdalski George C. Marshall Space Flight Center John F. Kennedy Space Center I CR85 Bldg 4203 RT-SRD-2 KSC HQS 3548 Marshall Space Flight Center, Alabama 35812 Kennedy Space Center, Florida 32899 B Mr. Vincent Lalli Mr. Ronald Lisk Lewis Research Center NASA Headquarters Code QS MS 501-4 Code 0152 200 E Street, SW g 21000 Brookpark Road Washington, DC 20546 Cleveland, Ohio 44135 u Mr. Malcolm Himel Lyndon B. Johnson Space Center Bldg. 45 RM 618A, Code NB2 m Houston, Texas 77058 w J ii U m I . J TABLE OF CONTENTS w SECTION PAGENUMBER PREFACE ................................................................ i DEVELOPING ACTIVITY .................................................. ii CENTER CONTACTS ...................................................... ii w I. INTRODUCTION ...................................................... v w A. Purpose .......................................................... v B. Control/Contributions ............................................... v C. Maintainability Technique Format Summary ........................... vi II. RECOMMENDED TECHNIQUES FOR EFFECTIVE MAINTAINABILITY Program Management 22 Technique PM-I : The Benefits of Implementing Maqntainability on NASA Programs .... PM-2 w Technique PM-2 : Maintainability Program Management Considerations ............. PM-8 Technique PM-3: Maintenance Concept for Space Systems ....................... PM-14 Design Factors and Engineering Technique DFE-I : Selection of Robotically Compatible Fasteners and Handling Mechanisms .................................... DFE-2 Technique DFE-2: False Alarm Mitigation ................................... DFE-8 Analysis and Test Technique A T-l: Neutral Buoyancy Simulation of On-Orbit Maintenance ............ AT-2 Technique A T-2: Mean Time To Repair Predictions ............................. AT-7 Technique A T-3: Availability Prediction and Analysis ........................... AT-12 Technique A 7-4: Availability, Cost, and Resource Allocation (ACARA) Model to Support Maintenance Requirements ......................... AT- 17 Technique AT-5: Rocket Engine Failure Detection Using an Average Signal Power Technique ......................................... AT-21 Operations and Operational Design Considerations Technique OPS-I : SRB Maintainability and Refurbishment Practices ............... OPS-2 Technique OPS-2: Electrical Connector Protection ............................. OPS-9 Technique OPS-3: Robotic Removal and Application of SRB Thermal Systems ....... OPS- 11 Technique OPS-4: GHe Purging of H 2 Systems ............................... OPS- 17 Technique OPS-5: Programmable Logic Controller ........................... OPS-20 III TABLE OF CONTENTS (CONT.) m IBm SECTION: PAGE NUMBER Operations and Operational Design Considerations (cont.) m Technique OPS-6: DC Drive - Solid State Controls ............................ OPS-24 i Technique OPS-7: AC- Variable Frequency Drive Systems ..................... OPS-28 m Technique OPS-8: Fiber Optic Systems ..................................... OPS-32 Technique OPS-9: Pneumatic Systems-Dome Loaded Pressure Regulator Loading .... OPS-36 Technique OPS-IO: Modular Automatic Power Source Switching Device OPS-39 I Technique OPS-11: Pneumatic System Contamination Protection ................. OPS-42 m m m. APPENDIX A: CANDIDATE TECHNIQUES FOR FUTURE DEVELOPMENT ............................................ A-1 g I M il IB J m_ w E m w u I m 1v u w I. INTRODUCTION r A. PURPOSE w Maintainability is a process for assuring the ease by which a system can be restored to operation following a failure. Designing and operating cost effective, maintainable systems ? f (both on-orbit and on the ground) has become a necessity within NASA. In addition, NASA w cannot afford to lose public support by designing less than successful projects. In this era of shrinking budgets, the temptation to reduce up front costs rather than consider total program life cycle costs should be avoided. In the past, relaxation of R&M requirements to reduce up front costs has resulted in end-items that did not perform as advertised and could not be properly maintained in a cost effective manner. Additional costs result when attempts are L_ made late in the design phase to correct for the early relaxation of requirements. w The purpose of this manual is to present a series of recommended techniques that can increase overall operational effectiveness of both flight- and ground-based NASA systems. Although each technique contains useful information, none should be interpreted as a requirement. The objective is to provide a set of tools to minimize the risk associated with: • Restoring failed functions (both ground and flight based) • Conducting complex and highly visible maintenance operations • Sustaining a technical capability to support the NASA mission utilizing aging equipment W or facilities. This document provides (1) program management considerations - key elements of an effective maintainability effort; (2) design and development considerations; (3) analysis and test considerations - quantitative and qualitative analysis processes and testing techniques; and (4) operations and operational design considerations that address NASA field experience. Updates will include a section applicable to on-orbit maintenance with practical experience from NASA EVA maintenance