NASA Technical Paper 3642 Working on the Boundaries: Philosophies and Practices of the Design Process R. Ryan, J. Blair, J. Townsend, and V. Verderaime July 1996 NASA Technical Paper 3642 Working on the Boundaries: Philosophies and Practices of the Design Process R. Ryan, J. Blair, J. Townsend, and V. Verderaime Marshall Space Flight Center • MSFC, Alabama National Aeronautics and Space Administration Marshall Space Flight Center • MSFC, Alabama 35812 July 1996 TABLE OF CONTENTS Page I. INTRODUCTION ................................................................................................................ 1 II. PHILOSOPHY ...................................................................................................................... 4 A. Organizational Philosophy .............................................................................................. 4 B. Philosophy of Design ...................................................................................................... 4 C. Design Tools ................................................................................................................... 5 D. Operations ....................................................................................................................... 6 E. Verification ..................................................................................................................... 6 III. ROLE OF CRITERIA IN DESIGN AND MANAGEMENT .............................................. 8 A. Criteria: Definition and Scope ........................................................................................ 8 B. Misuses of Criteria .......................................................................................................... 10 C. Proper Use of Criteria ..................................................................................................... 11 D. Project Management as Influenced by Criteria ............................................................... 13 E. Proper Development of Criteria ...................................................................................... 14 F. Restructuring Criteria to Full Potential ........................................................................... 15 IV. SYSTEMS GUIDELINES .................................................................................................... 16 A. Systems Design Process .................................................................................................. 16 B. Systems Concept Phase ................................................................................................... 17 C. Payload Requirements..................................................................................................... 17 D. Vehicle Concepts ............................................................................................................ 18 E. Systems Definition Phase................................................................................................ 21 F. Design Phase ................................................................................................................... 22 G. Quality Performance ....................................................................................................... 22 H. Quality Manufacturing .................................................................................................... 23 I. Verification ..................................................................................................................... 24 J. Operations ....................................................................................................................... 24 V. PROBABILISTIC DESIGN, APPROACHES, AND STATUS .......................................... 25 A. Background ..................................................................................................................... 25 B. Previous Applications ..................................................................................................... 26 C. Basic Approach ............................................................................................................... 29 D. Current Limitations of Probabilistic Methods ................................................................ 31 E. Recommendations of Critical Development Areas ......................................................... 32 VI. THE CONCEPT OF ROBUSTNESS IN DESIGN .............................................................. 32 A. General Process ............................................................................................................... 33 B. General Characteristics of Robustness ............................................................................ 37 C. Top Level Approaches .................................................................................................... 37 D. General Characteristics ................................................................................................... 39 E. Trades .............................................................................................................................. 40 iii TABLE OF CONTENTS (Continued) Page VII. DISCIPLINE FUNDAMENTALS ....................................................................................... 42 A. Structural Dynamics ........................................................................................................ 43 B. Fracture Mechanics ......................................................................................................... 45 VIII. INTERDISCIPLINARY ANALYSIS .................................................................................. 49 IX. TESTING .............................................................................................................................. 50 X. THE ROLES OF PROBLEMS HISTORY ........................................................................... 52 XI. ORGANIZATIONAL FUNDAMENTALS ......................................................................... 59 A. Empowerment ................................................................................................................. 60 B. Teaming .......................................................................................................................... 60 C. Leadership ....................................................................................................................... 60 XII. SPECIAL TOOLS................................................................................................................. 62 XIII. THE DESIGN CYCLE ......................................................................................................... 66 A. General or Overall Approach .......................................................................................... 66 B. Structural Tasks............................................................................................................... 78 C. Subelement and Local Analysis ...................................................................................... 93 D. Operations ....................................................................................................................... 94 XIV. CONCLUSIONS ................................................................................................................... 96 A. Summary ......................................................................................................................... 97 B. Recommendations ........................................................................................................... 98 REFERENCES.................................................................................................................................. 101 BIBLIOGRAPHY ............................................................................................................................. 105 iv LIST OF ILLUSTRATIONS Figure Title Page 1. System design process ....................................................................................................... 2 2. Interacting design requirements ......................................................................................... 3 3. Quality lever ....................................................................................................................... 5 4. “So that decimal point was a fly speck.” ........................................................................... 7 5. Role of requirements in product design ............................................................................. 9 6. Criteria in the design and operational cycle ....................................................................... 9 7. The balancing act ............................................................................................................... 11 8. Triangle of product design ................................................................................................. 12 9. Proper use of criteria .......................................................................................................... 12 10. Systems design process ...................................................................................................... 17 11. QFD process ....................................................................................................................... 18 12. Propulsion system selection options .................................................................................. 19 13. Vehicle parameters and interacting