Mission Success Starts with Safety Reliability Engineering - Discussions and Clarifications Reliability Engineering VS. Probabilistic Risk Assessment (PRA) Reliability Prediction VS. Reliability Demonstration Design Reliability VS. Process Reliability Fayssal M. Safie, Ph. D., NASA R&M Tech Fellow Marshall Space Flight Center SRE Meeting March 11, 2014 F. Safie 1
Agenda • Reliability Engineering Overview – Reliability Engineering Definitions – The Reliability Engineering Case – The Relationship to Safety, Mission Success, and Affordability • Discussions and Clarifications – Reliability VS. Probabilistic Risk Assessment (PRA) – Reliability Prediction VS. Reliability Demonstration – Design Reliability VS. Process Reliability • Concluding Remarks F. Safie 2
Reliability Engineering Overview F. Safie 3
Reliability Engineering • Reliability Engineering as a Discipline: – The application of engineering and scientific principles to the design and processing of products, both hardware and software, for the purpose of meeting product reliability requirements or goals. • Reliability as a Figure of Merit is: – The probability that an item will perform its intended function for a specified mission profile. • Reliability is a very broad design-support discipline. It has important interfaces with most engineering disciplines • Reliability analysis is critical for understanding component failure mechanisms and identifying reliability critical design and process drivers . F. Safie 4
The Reliability Engineering Case Reliability Program Management & Control Reliability Contractors and Reliability Program Reliability Progress Failure Review Program Plan Suppliers Monitoring Audits Reports Processes Process Reliability Reliability Requirements Root Cause Analysis Design Reliability Drivers Reliability Requirements Worst Case Analysis Analysis Critical Parameter Reliability Requirements Human Reliability Allocation Analysis Process Characterization Reliability Prediction Stress Screening Process Parameter Design Reliability Sneak Circuit Analysis Feedback Control Case Statistical Process Control Probabilistic Design Analysis Process Monitoring FMEA/CIL Reliability Testing F. Safie 5
The Relationship to Safety, Mission Success, and Affordability RELIABILITY MAINTAINABILITY SUPPORTABILITY COST OF LOGISTICS SUPPORT & Level of Repair Failure INFRASTRUCTURE Spares, Identification and Facilities, Analysis COST OF AFFORDABILITY Maintenance PREVENTIVE Preventive Critical Items MAINTENANC Labor , Maintenance Identification E materials , Design Mitigation Maintenance COST OF and Critical Process Support , etc. CORRRECTIVE Corrective Control MAINTENANCE Maintenance COST OF LOSS Loss of Crew/Mission/Space System, Stand Down, Loss of Launch Opportunity, etc. Failures COST OF DEVELOPMENT Redesigns TESTING, CERTIFICATION, AND SUSTAINING F. Safie 6 ENGINEERING
Reliability Discussions and Clarifications F. Safie 7
Probabilistic Risk Assessment (PRA) • Reliability: The probability that an item will perform its intended function for a specified mission profile. • Risk: The chance of occurrence of an undesired event and the severity of the resulting consequences. • Probabilistic Risk assessment (PRA) is the systematic process of analyzing a system, a process, or an activity to answer three basic questions: – What can go wrong that would lead to loss or degraded performance (i.e., scenarios involving undesired consequences of interest)? – How likely is it (probabilities)? – What is the severity of the degradation (consequences)? Likelihood Risk assessment is the task Scenario Consequence (Probability) of generating the triplet set S 1 C 1 p 1 S 2 C 2 p 2 R RISK { S i , P i , C i } S 3 C 3 p 3 . . . . . . . . . S N p N C N 8
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