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Systems Engineering and Spacecraft Subsystems Modeling as Prerequisites for Capstone Design

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2011 ASEE Annual Conference & Exposition


Vancouver, BC

Publication Date

June 26, 2011

Start Date

June 26, 2011

End Date

June 29, 2011



Conference Session

Developing Systems Engineering Curriculum, Part I

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Systems Engineering

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Page Numbers

22.1365.1 - 22.1365.9

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Paper Authors


Lisa Guerra NASA Headquarters

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Ms. Lisa A. Guerra,
Research Fellow
NASA, Exploration Systems Mission Directorate.

Lisa Guerra has 25 years experience in the NASA aerospace community. Ms. Guerra is currently working with the UTeach Engineering Program. She recently completed a four-year assignment from NASA Headquarters to establish a systems engineering curriculum at The University of Texas, Austin, as a pilot for national dissemination. Ms. Guerra’s most recent position at NASA Headquarters was Director of the Directorate Integration Office in the Exploration Systems Mission Directorate. In that position, her responsibilities involved strategic planning, international cooperation, cross-directorate coordination, architecture analysis, and exploration control boards. Prior to this assignment, Ms. Guerra worked in the Biological and Physical Research Enterprise and the Space Science Enterprise in the capacity as Special Assistant to the Associate Administrator. While in the Space Science Enterprise, she managed the Decadal Planning Team, a precursor effort to enabling the Bush Administration’s Vision for Space Exploration. Ms. Guerra also spent three years at the Goddard Space Flight Center as Program Integration Manager for future high-energy astrophysics missions, particularly the James Webb Space Telescope.

Ms. Guerra started her career at Eagle Engineering Corporation in Houston focusing on conceptual design of advanced spacecraft for human missions to the Moon and Mars. Ms. Guerra continued working on space exploration-oriented assignments at SAIC (Science Applications International Corporation) in support of NASA’s Johnson Space Center.

Ms. Guerra earned a B.S. in Aerospace Engineering and a B.A. in English from the University of Notre Dame. She received a Master of Science degree in Aerospace Engineering from the University of Texas at Austin. Her Master’s thesis, “A Commonality Assessment of Lunar Surface Habitation”, was performed under a research grant from the Johnson Space Center. Ms. Guerra is also a contributing author to the McGraw-Hill textbook, “Human Spaceflight, Mission Analysis and Design”. Her current efforts in systems engineering curriculum can be located at

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Wallace T. Fowler University of Texas, Austin

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Wallace Fowler is Professor of Aerospace Engineering and Engineering Mechanics at the University of Texas at Austin. ASEE offices held include Chair, Aerospace Division, Chair, Zone III, ASEE VP Member Affairs, ASEE First VP, and ASEE President 2000 - 2001. He is a member of the University of Texas Academy of Distinguished Teachers and has received numerous teaching awards.

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Martin James Brennan University of Texas, Austin, Department of Aerospace Engineering and Engineering Mechanics

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Growing up in Ocean Springs, MS, Martin Brennan developed a passion for science and in particular, flight. He entered Mississippi State University after high school with a keen sense of problem solving, which lead to earning a double major in Aerospace Engineering and Physics. His interest has been further ignited by graduate studies in spacecraft design and orbital mechanics at the University of Texas at Austin, where he is currently pursuing a Ph.D.

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Systems Engineering and Spacecraft Subsystems Modeling as Prerequisites for Capstone Design Wallace Fowler1, Lisa A. Guerra2, John A. Christian3, and Martin Brennan1 1 University of Texas at Austin 2 NASA Exploration Systems Mission Directorate 3 NASA Johnson Space Center A NASA project to improve design education university curricula has resulted in the addition of an undergraduate introduction to systems engineering and a spacecraft subsystems modeling laboratory as prerequisites to the capstone spacecraft/mission design course in aerospace engineering at the University of Texas at Austin. The systems engineering course materials, created by the second author, are based on NASA systems engineering practices and available in the public domain on the internet ( The current paper summarizes the content of the systems engineering course, as well as a companion lab on modeling spacecraft subsystems, and focuses on the positive effects of introducing systems engineering prior to the capstone design course. The student designs since the introduction of the systems engineering prerequisite have been more complete, better conceived, better documented, and much more professional than before. The student design team leadership has functioned more effectively and student oral presentations have been markedly improved. The effects of the systems engineering introduction are most apparent in the final written design reports. Summary information from an example student report is included here and the full report is available. Corresponding Author: Wallace Fowler, NASA’s Project The systems engineering course materials were organized into PowerPoint modules so that they couldIn fall 2006, the second author, a NASA engineer, came be made available as a resource for instructors acrossto the University of Texas at Austin on an Interagency the nation via the internet. As part of the materialsPersonnel Act (IPA) appointment for the purpose of development process, engineering faculty from thefinding ways to increase the systems engineering University of Colorado at Boulder reviewed the courseawareness of graduating engineering students. The goal materials and provided feedback. In October of 2008, awas to work at both the undergraduate and graduate conference was held at NASA JSC in which the courselevels. The first author had been teaching the capstone materials were first presented to the national academicspace/mission design course at UT Austin since 1985. community.During the two initial semesters, the NASA engineer Now available online, the materials include twenty-attended the capstone design classes and provided seven systems engineering lecture modules, examplelectures on systems engineering topics at the appropriate assignments and examinations, reference documentstimes during the semesters. Meanwhile, she was including NASA and other government handbooks,developing course materials and planning for a full recommended readings, two video lectures aboutcourse introducing systems engineering at the systems engineering by Gentry Lee of the Jet Propulsionundergraduate level. Laboratory, and links to other related systems In spring 2007, the first offering of the three engineering resources. The materials are available onsemester-credit-hour prototype systems engineering the National Space Grant Foundation website1. Theintroductory course occurred. There were twenty five website is updated periodically with additional materialstudents in the class, with most having taken the contributed by faculty who use the materials. Incapstone design course or were taking it simultaneously. addition, NASA is sponsoring the development ofThere were only a few students who had neither taken twelve new modules in related topics, such as humannor were enrolled in the capstone course. This meant factors engineering and virtual teaming. Thesethat the experiences of this set of students could not be additional modules, as well as a graduate-level systemsused as typical of the planned course sequence. engineering course will be available in 2010. Thewebsite also includes a FORUM on which users can propulsion, thermal, etc.), the space environment,share information. launch vehicle selection, Monte Carlo analysis, and a few other specialized modules. The last month of the UT Austin Implementation course is focused on an extensive individual project that looks at a trade study involving two subsystems for an In fall 2006, the Aerospace Engineering Department interplanetary mission. This final project gives theat UT Austin began planning for curriculum revisions to students an opportunity to exercise the tools theybe effective in the 2008-2010 course catalog. The first learned in the SSL course and provides a glimpse ofauthor chaired the curriculum committee. In the 2006- what they will be doing on a larger scale as part of a2008 catalog, students chose between an aeronautics team in the capstone design class.technical area and a space flight technical area, each ofwhich had seven hours of courses. In the new catalog, Capstone Design Courseeach technical area was expanded to contain thirteenhours of courses, with a second design course being The capstone design course is a three semester-credit-added to each area. The faculty in the space flight area hour course taught in both the fall and spring semesters.chose to require the Space Systems Engineering Design In this course, students do a conceptual design of a(SSED) course as the prerequisite for the capstone space system and mission. The design coursespacecraft/ mission design course. Also, a deliverables were sequenced to allow (force) the teamscomputational laboratory attached to the orbital to follow good systems engineering methodology. Themechanics course was revamped to focus on the deliverables, in the order assigned, are:modeling of spacecraft subsystems. The course wasrenamed as the Spacecraft Systems Laboratory (SSL) to  Design Scope Oral Presentationbetter reflect the new course content. These courses  Design Proposal - 20 to 30 pageswere formally adopted for inclusion in the curriculum as  Team e-mail Progress Reports – weeklyprerequisites for the capstone design course effective in  Team workload management reports as appropriatethe fall 2008 semester.  Design Requirements Briefings  Trade study oral/written reportsSpace Systems Engineering Design (SSED)  Mass/Volume/Power oral/written reportThis course is a three semester-credit-hour course taught  Design Oral Mid-Semester Presentationon a twice per week basis. The course modules  Design Written Mid-Semester Reportdeveloped for the SSED course are Introduction,  PowerPoint of the Oral PresentationTeamwork, Project Life Cycle, Scope and Concept of  Peer reviews: Mid-term Reports & PresentationsOperations, System Architecture, System Hierarchy and  Design Oral Final PresentationWork Breakdown Structure, Analytical Hierarchy  Design Written Final ReportsProcess, Requirements–Basics, Requirements–Writing,  Design Poster and/or Models (if appropriate)Requirements-Configuration and CM, FunctionalAnalysis, System Synthesis, Design, Interfaces, Implementation and EffectsMargins, Technical Performance Measures, Cost, Risk,Technology, Trade Studies, Reliability, Verification, The SSED course has been taught every fall andTechnical Reviews, Schedule, Management, and Ethics. spring semester at UT Austin beginning in spring 2007All modules are available to the students on the course and the SSL course was first taught in the fall of and remain available to them in the capstone The transition period, in which some students weredesign course. taking the SSED course and/or the SSL course concurrently with or after the capstone design course isSpace Systems Laboratory (SSL) complete. During the fall 2008 semester, only four students in the class had taken the SSED course, and The SSL is a one semester-credit-hour laboratory none had taken the SSL. Each of these students took thecourse, created by the third author, that focuses on the role of the Systems Engineer on a design team such thatmodeling of spacecraft subsystems. This course is there were four teams comprised of seven students, sixtaught concurrently with the SSED course and consists of whom had not taken the SSED course. The results inof a 1.5 hour lecture and a 1.5 hour guided computer lab this semester seemed better than those of earliereach week. Students in the SSL course step through 12 semesters, but the real improvements occurred whendifferent week-long modules that cover important topics almost all of the students in the capstone course hadin the analysis of spacecraft performance. Topics completed the prerequisite courses in the new sequence.include modeling and simulation, all the major In spring 2009, more than half of the students in thespacecraft subsystems (e.g. power, communications, capstone course had taken the SSED and SDL coursesand the student work was perceptibly better. In fall Satellite Triton Examining its Internal Nature). The2009, only one of 28 students had not taken the two example student work consists of the Table of Contents,(now prerequisite) courses. The quality of the student List of Figures, and List of Tables (without pagefinal reports was much improved. The work was more numbers) of the design team’s final report. These itemscomplete, better thought out, and more professional. provide insight into the influence of the SSED and SSLEffects of the SSED and SSL courses on the capstone courses on the student work without presenting thedesign course include the following: entire final 100 page report3. Note the Table of Student teams are effectively organized and Contents entries are compressed here. They were not function more smoothly. Using the team structuring compressed in the student report. model from SSED, teams now have a Project Manager, a Chief Engineer, and a Systems Table of Contents Engineer. Executive Summary Students now develop improved and more 1.0 Introduction comprehensive requirements than before. The 2.0 Project Scope (Need, Goal, Objectives, Mission, emphasis placed on requirements development in Constraints, Assumptions, Authority and Responsibility, SSED has resulted in a much greater appreciation Concept of Operations, Requirements, Requirements for the role of precise requirements in design. Hierarchy, NEWTON Mission Requirements, Level 1 Students implement trade studies in more detail. Requirements) The coverage of trades in SSED and the modeling 3.0 Design Approach (Trade Tree, Trajectory, of subsystems in SSL give the students a strong Trajectory Design, Trajectory Design Approach, appreciation for the need for trades and the ability Trajectory Heritage, Trajectory Trade Study, Trajectory to quickly and accurately model subsystems. Final Design, Launch Vehicle, Launch Vehicle Students develop preliminary Concepts of Definition, Launch Vehicle Design Approach, Launch Operations (ConOps) and later refine them based Vehicle Trade Study, Launch Vehicle Final Design. on requirements developed earlier in the course. Ground System, (Ground System Definition, Ground Teams are much less prone to decide on a single System Design Approach, Ground System Heritage, mission-architecture early in the formulation Ground System Final Design, Payload (NEWTON process. They are much more willing to revise Science Instruments Assembly, EINSTEIN Lander, their design concepts than students were in earlier NEWTON Orbiter (C&DH Subsystem, Power semesters. This indicates a better understanding of Subsystem, Propulsion Subsystem, Attitude, the role of iteration in engineering design. Determination, and Control Subsystem, Communication Students seem much more aware of the importance Subsystem, Thermal Subsystem, Structure, Aeroshell of looking at heritage systems. However, they Subsystem) measure heritage systems against their own 4.0 Design Details (Baseline Design, Subsystem Block requirements and often reject or suggest Diagram, Mass Table, Power Budget, Volume Budget, modifications to heritage systems if chosen as part Mission Timeline) of their designs. 5.0 Summary and Conclusions The depth of analysis of the various subsystems in 6.0 Strengths and Weakness (6.1 Strengths, 6.2 each team project has increased markedly, with Weaknesses) many subsystems now including candidate References hardware, performance criteria, and choices of Appendices (CAD Drawings, Level 2 & Level 3 specific hardware for their designs. In previous Requirements, Cost Model, Team Structure & semesters, this was a rare occurrence. Organization Chart, Power Budgets, Individual Contributions, Resumes) An Example of Student Work List of FiguresThe written design report is the primary tangibleproduct of the capstone design course. The example is 2.1 Concept of Operations Diagramfrom a student team in the fall 2009 semester. The 2.2 Requirements Hierarchyproject topic chosen was suggested by an engineer at the 3.1 NEWTON Mission Trade TreeJet Propulsion Laboratory and involved a Neptune 3.2 Differences between aerocapture and aerobrakingorbiter that deployed a lander on Neptune’s moon, 3.3 Graphical representation of inner gravity assistsTriton. The two vehicle names reflect their missions. 3.4 Graphical representation of the entire trajectoryThe main spacecraft is named NEWTON (Neptune 3.5 C3 v. mass capability for heavy–lift launchersExploration With Triton ObservatioN), and the Trition 3.6 Ground System Segmentslander is named EINSTEIN (Exploration Into Neptune’s 3.7 BER vs. Eb/No for various modulation techniques3.8 Eb/N0 vs. HGA diameter for various power inputs 4.2 Power Modes3.9 HGA mass vs. HGA diameter 4.3 Sample Power Table: Science Mode3.10 Operational and survivable temperature ranges C.1 Cost Estimate3.11 HGA shielding configuration3.12 HGA, thermal switch, MLA, ASRG, thermal Note the close correlation between the items in thelouver student report and the module topics in the SSED3.13 NEWTON Spacecraft’s five largest components course. The addition of the SSED and the SSL has3.14 Different aeroshell zones for TPS selection/ sizing resulted in improved design products for the UT-Austin4. 1 CAD Model of NEWTON-EINSTEIN Spacecraft aerospace engineering capstone design course. By4.2 CAD: NEWTON-EINSTEIN in Aeroshell introducing these prerequisites, the students have the4. 3 CAD Model of EINSTEIN Lander opportunity to understand and exercise critical tools and4.4 Subsystem Block Diagram techniques prior to implementing their capstone design.4.5 Power Used and Margins The addition of the SSED and SSL courses clearly4.6 Height: NEWTON-EINSTEIN vs Payload Fairing resulted in improved design products for the UT-Austin4.7 Diameter: NEWTON-EINSTEIN vs Payload Fairing aerospace engineering capstone design course. With this4.8 Mission Timeline early mastery of systems engineering topics andCAD Models: NEWTON-EINSTEIN Spacecraft modeling methods, the students can tackle more (Side View 1, Side View 2, Front View, Back View, complex mission capstone designs in the secondTop and Bottom Views, EINSTEIN and Skycrane semester of the sequence.Joined, EINSTEIN After Separation, Skycrane NASA’s investment in this project offers anSequence for EINSTEIN) opportunity to markedly improve aerospace (and other)Team Structure and Organization Chart engineering design education nationally. The entire SSED course can be adopted or individual modules canList of Tables be integrated into existing courses. NASA’s project was3.1 Flight times for potential gravity-assist designed so that, though one university served as the3.2 Weights for gravity assist FOMs site of the courseware development, all universities have3.3 Overall Rating for different gravity assists access to the materials. By using the modules, adopting3.4 Trajectory Design Characteristics them to local constraints, and then sharing the results3.5 Neptune Orbit Characteristics through the FORUM, design instructors can participate3.6 Launch Vehicle Heritage details in the ongoing evolution of the systems engineering3.7 Spacecraft Comparisons course materials.3.8 Instrument Comparisons Although NASA’s primary purpose in initiating the3.9 Instrument Package pilot program was the production of future aerospace3.10 Trade Study : Lander vs. Imp actor employees with a general awareness and understanding3.11 EINSTEIN Lander Mass Breakdown (Without of systems engineering prior to entering the workforce,Contingency) the primary aim was not to develop a group of students3.12 EINSTEIN Power Budget (Without Contingency) interested in becoming systems engineers. However,3.13 EINSTEIN Propellant and Tank Estimates for many of the UT students have voiced a career interest inCruise Phase this sub-discipline of engineering as well as graduate3.14 EINSTEIN Propulsion Maneuvers (without schools that enable further education in systemsContingency) engineering. Although it takes years of experience and3.15 EINSTEIN Science Instruments Assembly (ESIA) exposure to space missions and the relevant disciplines3.16 System Complexity to truly be a competent systems engineer, being aware3.17 C&DH Sizing Estimate of the discipline at the start in one’s career can only3.18 Figures of Merit Comparisons benefit the aerospace workforce in general. A recent3.19 Specifications for Propulsion Components graduate of the design sequence reported “I am still3.20 Mass and Volume for Propellant and Pressurant learning, but I can’t even imagine being here (Odyssey3.21 ADCS Subassemblies’ Quantity, Mass, Power, Space Research) without having learned and workedand Duty Cycle systems engineering. Everyone is treating me as if I3.22 Heritage Information for LGA and HGA understand all of the systems concepts (I was afraid I3.23 Communication Subsystem Design Details might be "babyed" since I was straight out of college),3.24 Thermal Techniques outlined and described and I believe I am holding my own.”3.25 NEWTON largest components and % volume3.26 Aeroshell TPS characteristics References4.1 Mass Breakdown: NEWTON-EINSTEIN Mission 1., Rebekah, Dustin Walker, Kevin Ferrant, DavisVarghese, Joshua Albers, and Richard Garodnick,NEWTON, Neptune Exploration With TritonExploratioN, Final Report, ASE 374L,Spacecraft/Mission Design, The University of Texas atAustin Spring 2009. Available from the first author

Guerra, L., & Fowler, W. T., & Brennan, M. J. (2011, June), Systems Engineering and Spacecraft Subsystems Modeling as Prerequisites for Capstone Design Paper presented at 2011 ASEE Annual Conference & Exposition, Vancouver, BC.

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