HEXANE: Architecting Manned Space Exploration Missions beyond Low-Earth Orbit by Alexander ...

255 Pages·2013·7.92 MB·English

HEXANE: Architecting Manned Space Exploration Missions beyond
Low-Earth Orbit
by
Alexander August Rudat
B.S. Mechanical Engineering
Georgia Institute of Technology, 2011

SUBMITTED TO THE DEPARTMENT OF AERONAUTICS AND ASTRONAUTICS
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE IN AERONAUTICS AND ASTRONAUTICS
AT THE
MASSACHUSETTS INSTITUTE OF TECHNOLOGY

JUNE 2013

© 2013 Massachusetts Institute of Technology. All Rights Reserved.

Signature of Author: __________________________________________________________________________________________
Department of Aeronautics and Astronautics
May 23, 2013

Certified by: ____________________________________________________________________________________________________
Prof. Edward F. Crawley
Ford Professor of Aeronautics and Astronautics and Engineering Systems
Thesis Supervisor

Accepted by: ___________________________________________________________________________________________________
Prof. Eytan H. Modiano
Professor of Aeronautics and Astronautics
Chair, Graduate Program Committee
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Architecting Manned Space Exploration Missions beyond Low-
Earth Orbit

by
Alexander August Rudat
Submitted to the Department of Aeronautics and Astronautics
on May 23, 2013 in Partial Fulfillment of the Requirements for the
Degree of Master of Science in Aeronautics and Astronautics

Abstract

With the end of the Space Shuttle Program and the cancellation of the Constellation Program,
NASA’s long-term designs for manned spaceflight beyond Earth orbit remain indefinite. Although
progress has been made in plans for operations on orbit, the capabilities gap for manned spaceflight
beyond orbit has grown. Gaining an understanding of the trade-offs inherent in future system
architectures for manned missions aids decision support for long-term planning of the spaceflight
infrastructure. Assessments of such manned missions are particularly difficult due to the quantity of
applicable technologies and potential component, sub-system, and system-level elements. Complex
interactions between these technologies and elements lead to the need for high-fidelity analysis,
requiring significant resource investments. NASA has typically turned to expert opinion and
detailed point design studies to assess possible mission architectures, but recent developments in
the field of systems architecture and computer science allow for the assessment of these
architectures through system modeling techniques.
This thesis presents a tool for the enumeration and analysis of system architectures for future
manned missions to the Moon, Mars, and Near-Earth Asteroids (NEAs). An abstracted, solution-
neutral formulation of the system allows for the analysis of the in-space transportation
infrastructure portion of potential mission architectures through a unique functional decomposition
and use of a decision formulation. Cost-based metrics are derived for the evaluation of
architectures, representing both mass-based operations costs as well as development and
procurement costs. The full combinatorial enumeration of the architecture tradespace generates a
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large data set on which to perform analysis. Rigorous techniques are used to derive decision
influence information from this data. In-depth evaluation of Mars conjunction-class missions, with
an emphasis on the assessment of highly influential architectural decisions, is presented, along with
a more superficial treatment of lunar and NEA architectures.
Mission architectures to these destinations are likely to require many new technologies and large-
scale mission elements. In order to build confidence in these technologies and elements, precursor
demonstration sub-missions (missions performed prior to the final surface mission) are often
required. A tool is presented to leverage the results from the mission enumeration and evaluation
model, exploring the tradespace of demonstration sub-mission sequences. In particular, this tool
analyzes the grouping of technologies and mission elements to demonstrate. It also examines the
use of Lagrange points as destinations for precursor sub-missions. Results from this tool are
presented for lunar and low-energy NEA missions using metrics representing both individual sub-
mission properties as well as sequence-level properties.
Finally, a framework is presented for the construction of architecture-level complex system
models. The development of this framework is based in knowledge gained from building the
previously described tools as well as an academic background in system architecting. The
framework directs professionals and academics in the process of designing complex system models
with the intent of reducing gratuitous and modeling-induced complexity while retaining essential
complexity. A brief case study is used to demonstrate the benefits gained from the use of the
framework in comparison to unguided model creation.

Thesis Supervisor: Edward F. Crawley

Title: Ford Professor of Engineering

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Acknowledgements
To my many friends and colleagues, both at M.I.T. and elsewhere, you have my everlasting thanks
for your support both during the process of working toward my Master’s degree and during the
years before it. I could not have come this far without you. To my close friend and roommate,
Tamas, thank you for putting up with my late night rants, both good and bad. You, Vishnu,
Michael, and my other supporters in the M.I.T. community have kept my days lively and my love
of space strong.

To my colleagues, both here and far away, thank you for your understanding and encouragement in
coming from a mechanical engineering background with little knowledge of spacecraft to this point.
Jon and Alessandro, HEXANE would never have been produced without your help. Dani, my
thesis would certainly have never been completed without your tireless hours of editing and very
helpful feedback. You have always been an excellent resource. And I also thank your wife and my
friend, Ana, who put up with you editing my thesis and also gave me support in this process.
Morgan, Peter, Francisco, Marc, Wen, and Andreas, you have all been great friends and supporters
through my time here, and I have always been impressed with all of your passions and capabilities.
And, of course, to my friends across the office, Narek, Sydney, Koki, Andrew, Margaret, Ioana,
and Amanda, thank you for putting up with our conversations over on our side and keeping our
enthusiasm strong.

Bruce, this thesis and this degree would never have been completed without your support. Your
insights have created much of this research, and for that I thank you.

To my advisor, Ed Crawley, your enthusiasm has never waned as your time sometimes did. It has
been an honor and a pleasure.

And finally, to my family, my parents and my sisters as well as my relatives and relatives in-law,
without your wisdom and your guidance, your support in all things, I would not be at M.I.T., nor
would I have such a fruitful life. As always, you have my thanks and my love.

And thank you, space, because you’re awesome.

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Table of Contents
ACKNOWLEDGEMENTS ..................................................................................................................... 6
LIST OF FIGURES .............................................................................................................................. 11
LIST OF TABLES ................................................................................................................................ 14
ACRONYMS AND ABBREVIATIONS ................................................................................................ 16
1. INTRODUCTION ......................................................................................................................... 19
1.1 MOTIVATION ........................................................................................................................... 19
1.1.1 Current State of Manned Space Exploration ....................................................................... 19
1.1.2 Infrastructure Development and Long-Term Planning ...................................................... 20
1.2 THE ROLE OF SYSTEM ARCHITECTURE AND ARCHITECTING .................................... 21
1.3 DECISION ANALYSIS IN SYSTEM ARCHITECTURE ........................................................ 22
1.4 EXHAUSTIVE TRADESPACE EXPLORATION .................................................................... 23
1.5 PRIOR MANNED SPACEFLIGHT MODELS ......................................................................... 23
1.5.1 Hofstetter Manned Spaceflight Tradespace Model ............................................................. 23
1.5.2 Simmons Manned Spaceflight Tradespace Model ............................................................... 25
1.5.3 Design Reference Architecture 5.0 ....................................................................................... 28
1.5.4 Austere ................................................................................................................................... 34
1.5.5 Mars-Oz .................................................................................................................................. 36
1.5.6 Additional Point Design Studies ........................................................................................... 38
1.5.7 The Design of Complex System Models ............................................................................... 38
1.6 OBJECTIVES ............................................................................................................................ 39
1.7 THESIS OVERVIEW ................................................................................................................. 40
2. HEXANE: HUMAN EXPLORATION ARCHITECTURE NETWORK EVALUATOR ................ 42
2.1 SCOPING AND PROBLEM STATEMENT .............................................................................. 42
2.1.1 Infrastructure Downscoping ................................................................................................. 43
2.1.2 Destination Selection ............................................................................................................. 44
2.1.3 Sortie-Like Mission Design ................................................................................................... 46
2.1.4 Abstraction ............................................................................................................................. 47
2.2 HABITATION AND TRANSPORTATION FUNCTIONAL DECOMPOSITION .................. 47
2.2.1 Primal Functions ................................................................................................................... 49
2.2.2 Temporal- & Requirement-based Sub-Functions ................................................................ 50
2.2.3 Representation in an Exploration Mission Context ............................................................ 53
2.2.4 Invariant Functions and Set Partitioning ........................................................................... 54
2.3 ARCHITECTURE-LEVEL TECHNOLOGIES ........................................................................ 56
2.4 FORMULATION AS AN ASSIGNMENT PROBLEM ............................................................. 57
2.5 PARAMETRICS ......................................................................................................................... 59
2.5.1 The Need for Parametrics ..................................................................................................... 59
2.5.2 Assumptions ........................................................................................................................... 61
2.5.3 Metrics .................................................................................................................................... 63
2.6 MODEL STRUCTURE .............................................................................................................. 65
2.7 VALIDATION ............................................................................................................................ 68
2.7.1 Mars Validation ..................................................................................................................... 69
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2.7.2 Lunar Validation ................................................................................................................... 72
2.7.3 NEA Validation ...................................................................................................................... 73
2.8 CHAPTER SUMMARY ............................................................................................................. 73
3. PRIMARY FINDINGS: MARS ..................................................................................................... 74
3.1 ANALYSIS GOALS AND SUMMARY ...................................................................................... 74
3.2 CONSTRAINED TRADESPACE ANALYSIS .......................................................................... 76
3.2.1 Mass Feasibility Constraint .................................................................................................. 76
3.2.2 Orion Multi-Purpose Crew Vehicle Constraint ................................................................... 77
3.2.3 General Tradespace Characteristics .................................................................................... 80
3.3 OPTIMAL ARCHITECTURES ................................................................................................. 85
3.3.1 Minimum IMLEO Architecture ............................................................................................ 86
3.3.2 Minimum LCC Architecture ................................................................................................. 89
3.3.3 All Non-Dominated Architectures ........................................................................................ 93
3.4 ARCHITECTURAL DECISIONS AND COUPLING ............................................................... 96
3.4.1 IMLEO-Minimal Decision “Switches” .................................................................................. 97
3.4.2 Fixed Architecture Decision Switches ................................................................................ 100
3.4.3 Technology Influence Measure ........................................................................................... 103
3.4.4 Cryogenic Propellant Usage ................................................................................................ 105
3.4.5 Boil-Off Control .................................................................................................................... 107
3.4.6 Nuclear Thermal Rockets .................................................................................................... 109
3.4.7 Pre-Deployment using Solar-Electric Propulsion .............................................................. 110
3.4.8 Ablative Aerocapture ........................................................................................................... 112
3.4.9 In-Space LOX/LCH Stages ................................................................................................ 114
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3.4.10 Capsules and the MPCV ................................................................................................. 115
3.4.11 Monolithic and Semi-Monolithic Habitats ..................................................................... 116
3.4.12 Decision Coupling ............................................................................................................ 118
3.5 CONCLUSIONS AND RECOMMENDATIONS .................................................................... 122
3.6 A BRIEF DISCUSSION OF LUNAR AND NEA RESULTS.................................................. 123
3.6.1 Lunar Architecture Results ................................................................................................ 123
3.6.2 Low-Energy NEA Results ................................................................................................... 124
3.6.3 High-Energy NEA Results .................................................................................................. 125
3.6.4 Combined Results Analysis ................................................................................................. 125
3.7 SUMMARY ............................................................................................................................... 127
4. STEPPING STONES: PROGRESSION TOWARD LOW-ENERGY DESTINATIONS ............. 128
4.1 MOTIVATION AND PROBLEM STATEMENT .................................................................... 128
4.2 LOW-E AS A BACKEND TO HEXANE .................................................................................. 131
4.2.1 Demonstrable Technologies & Capabilities ....................................................................... 131
4.2.2 Demonstration Destinations ............................................................................................... 136
4.2.3 Assumptions ......................................................................................................................... 136
4.2.4 Metrics .................................................................................................................................. 137
4.3 RESULTS AND FINDINGS .................................................................................................... 138
4.3.1 Lunar Results....................................................................................................................... 139
4.3.2 Low-Energy NEAs ............................................................................................................... 149
4.4 CONCLUSIONS AND RECOMMENDATIONS .................................................................... 154
4.5 CHAPTER SUMMARY ........................................................................................................... 155
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5. A FRAMEWORK FOR THE MODELING OF COMPLEX SYSTEMS ...................................... 156
5.1 INTRODUCTION .................................................................................................................... 156
5.1.1 Motivation: Modeling of Complex Systems as a General Challenge ................................ 156
5.1.2 Lessons Learned from HEXANE ........................................................................................ 157
5.1.3 Gratuitous & Modeling-Induced Complexity vs. Essential Complexity .......................... 158
5.1.4 Objectives ............................................................................................................................. 159
5.2 IDEOLOGICAL VS. PHYSICAL MODELS AND THE FUNNEL FRAMEWORK .............. 161
5.2.1 Ideological Model ................................................................................................................. 162
5.2.2 Physical Model ..................................................................................................................... 165
5.2.3 Funnel Framework .............................................................................................................. 166
5.3 THE EXPANDED FRAMEWORK .......................................................................................... 167
5.3.1 Classification of Coupling Relationships ............................................................................ 168
5.3.2 Separability .......................................................................................................................... 169
5.3.3 Reducible vs. Irreducible Coupling ..................................................................................... 170
5.3.4 Parallel vs. Serial Sub-problems ........................................................................................ 172
5.3.5 The Role of Cognitive Psychology ....................................................................................... 175
5.3.6 Expanded Ideological Model ............................................................................................... 175
5.3.7 Expanded Physical Model ................................................................................................... 178
5.3.8 Integrated Expanded Models .............................................................................................. 180
5.3.9 Topics for Further Consideration ....................................................................................... 181
5.4 COMPARISON WITH PREVIOUS CONCEPTS ................................................................... 181
5.4.1 Simon’s Four Steps to Decision Making ............................................................................. 182
5.4.2 Simmons’ Four Steps ........................................................................................................... 183
5.5 ASSUMPTIONS AND LIMITATIONS ................................................................................... 186
5.6 CASE STUDY IN BRIEF: HOFSTETTER MANNED SPACEFLIGHT MODEL ................ 187
5.7 FUTURE WORK ...................................................................................................................... 190
5.8 CHAPTER SUMMARY ........................................................................................................... 192
6. CONCLUSION ........................................................................................................................... 194
6.1 THESIS SUMMARY ................................................................................................................ 194
6.2 PRIMARY CONTRIBUTIONS ................................................................................................ 195
6.2.1 Methodology and Tool Contributions ................................................................................. 195
6.2.2 Analysis Findings ................................................................................................................ 196
6.3 FUTURE WORK ...................................................................................................................... 197
6.3.1 HEXANE Refinement .......................................................................................................... 198
6.3.2 Low-E Refinement ............................................................................................................... 201
6.3.3 Funnel Framework Development ....................................................................................... 201
BIBLIOGRAPHY ............................................................................................................................... 203
APPENDIX A: ADDITIONAL HEXANE INFORMATION ............................................................... 212
A-1: PARAMETER DATABASE ............................................................................................................. 212
A-2: EXPANDED FUNCTIONAL BLOCK DIAGRAM ............................................................................... 214
A-3: ASSUMPTIONS LIST ................................................................................................................... 215
A-4: ∆V MATRICES ............................................................................................................................ 217
A-5: TOF MATRIX ............................................................................................................................. 219
A-6: LOW-THRUST ∆V ESTIMATION METHOD ................................................................................... 220
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A-7: LOW-THRUST ∆V MATRIX.......................................................................................................... 222
A-8: LOW-THRUST TOF MATRIX ....................................................................................................... 223
A-9: MATRIX METHOD FOR SIMULTANEOUS PROPULSION ELEMENT SIZING ................................... 224
A-10: ALTERNATIVE ITERATIVE SOLVER FOR NESTED PROPULSION ELEMENTS ................................ 226
A-11: CHEMICAL PROPULSION ELEMENT SIZING METHOD ................................................................ 227
A-12: SEP ELEMENT SIZING METHOD ................................................................................................ 228
A-13: PROPELLANT DATA .................................................................................................................... 230
A-14: AEROCAPTURE SHIELD SIZING AND EDL RESPONSE SURFACE ................................................ 230
A-15: ISRU ......................................................................................................................................... 234
A-16: HABITAT SIZING PARAMETRICS ................................................................................................. 235
A-17: LOGISTICS SIZING PARAMETRIC ................................................................................................ 237
APPENDIX B: LUNAR AND NEA HEXANE RESULTS .................................................................. 239
B-1: LUNAR RESULTS ........................................................................................................................ 239
B-2: LOW-ENERGY NEA RESULTS .................................................................................................... 245
B-3: HIGH ENERGY NEA RESULTS ................................................................................................... 250

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