Measuring Space Systems Flexibility: a Comprehensive Six-Element Framework
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Measuring Space Systems Flexibility: A Comprehensive Six-element Framework by Roshanak Nilchiani M.S. Engineering Mechanics, University of Nebraska-Lincoln, 2002 B.S. Mechanical Engineering, Sharif University of Technology, 1998 SUBMITTED TO THE DEPARTMENT OF AERONAUTICS AND ASTRONAUTICS IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN AEROSPACE SYSTEMS AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY September 2005 Copyright © 2005 Massachusetts Institute of Technology. All Rights Reserved Author…………………………………………………………….……………………. Space Systems Laboratory, Department of Aeronautics and Astronautics Certified by………………………………………………………………………………. Daniel E. Hastings, Thesis Committee Chair Director, Engineering Systems Division Professor of Engineering Systems and Aeronautics and Astronautics Certified by.…………………………………….…………………….………………… Joseph M. Sussman, Thesis Supervisor Professor of Civil and Environmental Engineering and Engineering Systems Certified by…………………………………………………….………………………… David W. Miller, Thesis Supervisor Associate Professor of Aeronautics and Astronautics Accepted by………………………………………………….………………………………….. Jaime Peraire, Professor of Aeronautics and Astronautics Chair, Committee on Graduate Students 2 Measuring Space Systems Flexibility: A Comprehensive Six-element Framework by Roshanak Nilchiani Submitted To the Department of Aeronautics and Astronautics In Partial Fulfillment of The Requirements For The Degree Of Doctor of Philosophy In Aerospace Systems At the Massachusetts Institute Of Technology Abstract Space systems are extremely delicate and costly engineering artifacts that take a long time to design, manufacture, and launch into space and after they are launched, there is limited access to them. Millions of dollars of space systems assets lost annually, when the space system has failed to meet new market conditions, cannot adapt to new applications, its technology becomes obsolete or when it cannot cope with changes in the environment it operates in. Some senior leaders have called for more flexible space systems. The existence of flexibility can help it adapt itself to the change at hand, or even take advantage of new possibilities while in space. Yet in the absence of a practical way to measure its value, most decision-makers overlook its implementation in their space systems. Although the literature is not lacking in number of flexibility measures, there is a void in articulating a unified and comprehensive framework for measuring the multiple aspects of flexibility in space systems. This research is an effort to provide such a framework based on the common fundamental elements that define the nature of flexibility in space systems and other engineering systems. Through the extraction of common elements of flexibility from 25 major papers in the field of space systems flexibility, more than 60 papers in the field of manufacturing flexibility and 43 papers in the field of systems engineering, this dissertation identified uncertainty, time window of change, system boundary, response to change, the system aspect to which flexibility is applied, and access to the system as the six key elements that affect the value flexibility. Based on the six elements, the 6E Flexibility Framework was proposed as a twelve-step framework that can guide decision-makers in assessing the value of flexibility in their system. The framework was then applied to four case studies dealing with a variety of space systems (commercial, military and scientific) with monetary and non-monetary value delivery, at different scales (satellite level, fleet level), different time windows of change and with regards to different aspects of flexibility (life extension, instrument upgrade, capacity expansion) facing different kinds of uncertainty (technological change and market uncertainty). The case studies demonstrated the ability of such a framework to provide decision-makers with the information necessary to integrate flexibility in their design and operational decisions and showed that the 6E Flexibility framework could be applied across different aspects of a system easily, capturing the impact of flexibility on design of and decision-making for space systems. 3 4 Acknowledgement I also dedicate this work to the memory of my uncle Morteza Mohebbi-Taban, who provided me with my first scientific books at the age of six, who brought me my first telescope and opened to me the awe for a universe far beyond the confines of our earth. I owe my passion for knowledge and scientific exploration to him. The passion he filled me with will continue to take me on a journey that may never end as long as I am alive. My love for Ali, my soul mate, has been the source of much of the energy for my explorations in the past 10 years. During all the difficult times of the past few years, he has been on my side, giving me courage to face the professional and personal challenges I have faced while at MIT. Without his support, this dissertation would not have been possible. My family has been a major source of support and love, and I would not be here if it were not for them. My sincere love and thanks to my mom Tahereh Mohebbi-Taban, my father Masoud Nilchiani and my siblings Azadeh and Mani. My affection for my uncle Reza Mohebbi-Taban, my aunt Azarakhsh Etemadzadeh and their encouragement of my scientific quest deserves a special thanks. My grandmother, Zahra Ghorbani, whose wisdom has given me the gift of life deserves my deepest gratitude. The unwavering support of my in-laws, Jalil and Enci Mostashari allowed me and Ali to take this opportunity to explore the world beyond the borders of our birthplace. They are also high on the thank you list. I would like to express my gratitude to all those who provided me with guidance in completing this dissertation. I would like to thank Prof. Daniel E. Hastings for his thorough guidance and supervision of this work and for providing me with an opportunity to work on such an exciting and challenging topic. I would also like to thank my doctoral committee Prof. Joseph M. Sussman and Prof. David Miller for their support and guidance and their excellent feedback throughout the process. Many thanks to Prof. Annalisa Weigel and Prof. Oliver De Weck for accepting to be my thesis readers, and for providing valuable input on this research. I would like to acknowledge the support of AFRL/VS from the Defense Advanced research Program Agency (DARPA) Contract No. F29601-97-K-0010. In addition, I would particularly like to thank Lt. Col. James Shoemaker at DARPA for his continued support. Last, but not least I would like to acknowledge the support of my dear friends Ebru Gokdag, Kalina Galabova, and Maryam Rahimi who listened when I needed to be heard. Thank you. 5 6 Table of Contents 1. Introduction......................................................................................................... 21 Flexibility in Space Systems ......................................................................................... 23 Problem Definition: Measuring the Value of Flexibility in Space Systems ................. 23 Research Hypothesis ..................................................................................................... 24 Research Methodology ................................................................................................. 25 Structure of the Dissertation ......................................................................................... 25 2. Flexibility in Engineering Systems: A Literature Review...................................... 29 2.1. Flexibility in Engineering Systems ....................................................................... 29 2.2. Manufacturing Systems Flexibility....................................................................... 30 2.2.1. Definitions................................................................................................. 30 2.2.2. Classifications of Flexibility in Manufacturing ........................................ 31 2.2.3. Measurements of Flexibility ..................................................................... 32 2.3. Network Flexibility............................................................................................... 42 2.3.1. Definition .................................................................................................. 42 2.3.2. Flexibility and Robustness in Network Systems....................................... 44 2.3.3. Measuring Network Flexibility................................................................. 45 2.3.4. Quantitative Measures of Network Complexity ....................................... 48 2.4. Summary ................................................................................................... 53 3. Space Systems Flexibility: A Literature Review .............................................. 59 3.1. Flexibility on the Basis of Cost per Function ....................................................... 59 3.1.1. Shaw’s Metric for Flexibility in Telecommunication Satellites ............... 60 3.1.2. Analysis of Shaw’s metric ........................................................................ 62 3.2. Black-Scholes Approach to Flexibility in Space Systems .................................... 62 3.2.1. Saleh and Lamassoure flexibility metric for Space Systems .................... 62 3.2.2. Limitations of Black-Scholes approach to flexibility ............................... 65 3.3. Provider-side Flexibility in On-orbit Servicing ...................................................