Introduction to Aerospace Systems Engineering

1. Introduction to Aerospace Systems Engineering Henry ‘Lad’ Curtis Director of Engineering MicroSat Systems Inc. Littleton, Colorado 25 September 2007

2. Outline • Life Cycle of a Aerospace Spacecraft Program • What is Systems Engineering? • What are the Characteristics of a Systems Engineer? • What Does a Systems Engineer Do? • Mission Analysis • Setting the Requirements • Performing a Trade Study • Controlling the Design • Verifying the Requirements • Flying the Mission • Review

3. Concept Requirements Design Assembly, Integration & Test Mission Ops SC CAD Model SC Verification Matrix Op’s Handbook Con Ops Plan S/C Requirements Document Mfg. Procedures Test Procedures Trade Studies S/C Performance Reports ROM Cost Product Thermal and Space Simulations Environments Definition Detailed Analysis Science Data S/C Desc. Test Reports ICD’s Verification Plan Mission Analysis Non-conformance Documents Engineering Change Requests Risk Mgmt Plan Design Reference Mission People Change Board Eng. Ops Support Subcontractors ID’d System Design Meeting Core Tech Team Risk Board Award Contract SRR PDR CDR Env. Test Launch Events 18 Months to 4 Years 6 Months to 10 Years 6 Months to 2 Years Life Cycle of a Spacecraft Project

4. Mission System Thermal Subsystem Structure Subsystem Power Subsystem Spacecraft System Data Subsystem Payloads What is Systems Engineering? • A System is a Collection of Objects and Tasks Assigned to an Organization or Person. • Systems Can Contain Other Systems • A Systems Engineer Brings Together The Pieces of the System To Meet the Mission Objectives

5. What are the Characteristics of a Systems Engineer? • A Generalist: Knows Something About Everything • Experienced in All Aspects of Concept, Design, Test, Operations • This Means Most People Grow Into Systems Engineers Instead of Starting as Systems Engineers • Likes to Organize • Ability to Apply Basic Engineering Principles to Any Problem Across Multiple Engineering Disciplines • Excellent Problem Solving Skills • Skill at Breaking a Large Problem into Manageable Pieces and Controlling the Interface Between the Pieces • Likes to Work With People • Balanced Philosophies between Idealism and Practicality • Create a Quality Product On-Time and On-Budget • Ability to be Assertive if Necessary

6. What Does a Spacecraft Systems Engineer Do? • Mission Analysis • Design Leadership: Configuration and Performance Monitoring • System Trade Studies • Launch Vehicle Integration • Payload Accommodation On the Spacecraft • Specialty Engineering (Magnetic, Contamination, Radio Interference, Space Radiation, etc.) • Integration and Test • Verification & Anomaly Resolution • Mission Operations Support • Customer Collaboration Examples of Systems Engineering Tasks on a BalloonSat …

7. Concept Requirements Design Assembly, Integration & Test Mission Ops Mission Analysis • We Want to Maximize Mission Duration • What Events Or Physics Limits The Mission Duration? • Batteries • Balloon Failure • Data Collection Capacity • Which Limit Will Be Reached First? • Battery Capacity vs. Power Consumption by Subsystems and Payloads • Testing to Confirm Analysis will be Performed Later in the Program • Don’t forget about Temperature Impacts on Battery Life! • Estimate Rate of Ascent to Predict Battery Burst Time After Launch • Add on Time from Burst to Landing Based on Rate of Descent • Estimate or Define a Requirement for Rate of Data Collection so That Both Ascent and Descent Data Can Be Collected Within the Available Memory Capacity • Mission Analysis Results: • Life Limiter is the Battery Capacity. Want to Drive to Maximize Mission Duration. • Need Derived Requirements: Must Have Battery Heaters and Reduce Data Collection

8. Concept Requirements Design Assembly, Integration & Test Mission Ops Level 0/1: Mission Level 2: System Level 3: Subsystem Ground Chase Requirements Document Laptop and Chase Vehicle Requirements Power Allocations to Subsystems Eng. Change Form Payload Requirements Mission Definition Document BalloonSat Subsystems Mass Allocations to Subsystems BalloonSat System Requirements Document Power Customer Mission Statement (Very General Statement) Mission Objectives (3 - 5 General Statements from Mission Statement) Objective Requirements (Quantify Objectives) Att. Control SC CAD Model Structures SC Test Plan Software Environments Definition Change Approval Board Cmd & Data Thermal Payload Interface/ Constraints Doc Launch Vehicle Requirements Document Balloon, Tether, GPS Requirements Requirements and Design Control The System Engineer Documents and Controls Changes to the System and Subsystem Designs

9. What is a Requirement? • A One Sentence Statement Defining a Characteristic or Objective of a Thing. • Defines “What, Where, When” and Avoids “How” • An Ambiguous Requirement Can Result in Misinterpretation and Mission Failure. • A Requirement That Can Not Be Verified is Useless. • Verification Must Be Possible By Analysis, Inspection, Demonstration, or Test of the Components or End Product. • Example: BallonSat Mass Requirement • “Each BalloonSat is 1 kg.” • Ambiguous…Is this a statement of fact, estimate, or desire? • “Each BalloonSat Will Weigh 1 kg.” • Ambiguous… Is this a goal or a requirement. Can it be less than one kilogram? • “Each BalloonSat Shall Weigh No More Than 1.0 kg” • Good • Standard Terminology • “Shall” A Requirement Which Must Be Verified, Use It In Every Requirement • “Should” A Goal For Which A Best Effort Will Be Made • “Will” A Factual Or Explanatory Statement

10. Concept Requirements Design Assembly, Integration & Test Mission Ops Trade Studies A Trade Study is a Multi-variable Analysis That Defines a New Requirement or a Design Solution Steps: • Clearly Define a Desired Objective of the Trade Study. • Select System Parameters That Drive the System Design. • Vary the Value of Parameters to Understand the Benefits and Costs of Each Against the End Goal. • Apply Judgment to Reject Unreasonable Options. • Select the Value of Varied Parameters To Achieve the Best Result. BalloonSat Trade Study Example: • The System = Balloon Mission. The Issue = Number of Payloads? • Student Exercise: Perform a System Trade to Define Number of BallonSats in the Mission • STEP 1: Objective of Trade is “Define the Number of BallonSats on the Mission” • Customer Objective = Fly as Many BalloonSats as Possible • Customer Requirement = Balloon Shall Lift No Less Than 5 kg.

11. BalloonSat Trade Study Step 2: What Parameters Influence the Number of BalloonSats That Can Be Flown on the Balloon Mission? • Total Payload Mass: mp = nbs* mb Step 3: Vary the Parameters to Understand the Effect • Each Variation Requires a Point Design Be Created – Guess nbs • A Trade Matrix is a Common Tool Used to Organize Parameters and Options Step 5: Select the Best Solution: Design B or C • Customer Rejects Design C…10 Teams Too Many for One Professor to Manage (Surprise! You Didn’t Know This At the Outset) • Derived Requirement = BalloonSat Mass shall be Less Than 1 kg • New Derived Requirement = Number of BalloonSats in Mission Shall be Less Than 6 • Solution is Design B • Lessons: Sometimes You Have to Guess A Solution, Sometimes the Customer Has Unstated Goals or Requirements

12. Concept Requirements Design Assembly, Integration & Test Mission Ops Mass Limit 1.00 0% Mass Margin Plan Current Best Estimate Trend 25% Margin Violated. Decision Needed! 20% 0.75 15% Mass (kg) 5% 0.50 Current Date Time 0.25 Concept PDR CDR Test Launch Managing the Design: TPM’s • Technical Performance Measures (TPM’s) Are Selected From System Characteristics Known To Drive the Design Result • BalloonSat TPM’s ? • Mass, Power, Amount of Data Collected • Margin on a TPM Is Set At the Start of a Program Based on Engineering Experience • TPM Trends Are Used to Trigger Design Changes • Is Trend Dependable and No Action is Needed? • Act Now to Avoid More Drastic Acts in the Future?

13. Prove the System Meets Design Requirements Concept Requirements Design Assembly, Integration & Test Mission Ops Identify Requirements to Be Verified in Each Event Perform Verification: Analysis, Demo, Inspect, Test Document Results • “System” Test the BalloonSat • Run The Test Like Real-life Will Be • Temperature, Vacuum, Vibration Testing At Greater Extremes Than Launch And Flight Conditions • Run An Entire Mission Simulation From Launch To Landing Confirm Each Requirement Has Been Verified Satisfactorily Integration and Test • Key concept: Each Subsystem Comes To Integration After It Has Been Tested And Verified On Its Own • Systems Engineers • Insure The Intent Of Requirements Are Fulfilled • Write/Approve Test Procedures • Lead Trouble-shooting During The Testing With The Test Conductor

14. Concept Requirements Design Assembly, Integration & Test Mission Ops Launch and Mission Operations • Systems Engineers Often Lead a Group of Subsystem Experts Who Each Monitor Their Subsystems • Go for Launch! • The Systems Engineer Uses His/Her Accumulated Knowledge of a Product to Monitor and Fix the Product. • Mission Rules Are Do’s And Don’ts For Operating The Product. • Each Product Has A Unique Behavior That Is Learned During The Ground Test Program. • Once The Product Has Been Calibrated and is Operating Properly it is Sometimes Transferred to Full-Time Technicians and Engineers Who Operate it for the Customer.

15. Review • Systems Engineers Are Generalists • Systems Engineers Define Requirements and Control the Design Process • Systems Engineers Use Trade Studies and Technical Performance Measures to Make Design Decisions • Systems Engineers Participate in Integration and Test • Systems Engineers May Operate the Product During Flight Complex Products or Endeavors Require Systems Engineering The Current Demand for Systems Engineers is Large And Expected to Increase

16. Acronyms CDR- Critical Design Review Con Ops- Concept of Operations (Describes how the spacecraft is going to be used) ICD- Interface Control Document I&T- Integration and Test LV- Launch Vehicle Op’s- Mission Operations PDR- Preliminary Design Review RR- Readiness Review S/C,SC- Spacecraft SRR- System Requirements Review TPM- Technical Performance Measures

17. References and Resources • Koehler, C. Aug. 2002.BalloonSat: Missions to the Edge of Space. 16th Annual/USU Conference on Small Satellites, Paper SSC02-IX-7. • J. R. Wertz and W.J. Larson 1999. Space Mission Analysis and Design, Third Edition. El Segundo, California: Microcosm Press • M. Pilinski and C. Koehler 2007, Requirements Definition,Colorado Space Grant Consortium Presentation

18. Additional Information

19. Typical Organization of a Gov. Spacecraft Program Gov/Civilian Customer Program Engineer Launch Vehicle Provider Payload/Sensor Provider Spacecraft Bus Provider Program Manager Ground Control System Provider Chief Systems Engineer Propulsion Thermal Power Telecommunications Structures and Mechanisms Systems Engineering Command & Data Handling Integration and Test Mission Analysis System Design Lead Requirements and Verification Payload and LV Integration Specialty Engineers Mission Operations

20. Structures Design Flow Process Requirements Level 1, 2 and Derived LV Environments, Mass Prop, I/F Envelope Instrument &P/L Alignment, Pointing, and FOV Grounding & ESD Thermal Control Material Compatibility Requirement Verification Preliminary Design SV & Structure 3-D Solid Model Mass Properties/ MEL Drawing Tree Sub-System I/F Concept Design & Review Initial Model Preliminary Design Review Requirements Update Preliminary Manufacturing Tooling Assembly Methods Structural Analysis Structural Criteria Stiffness, Loads Flight Design Design & Model Updates Flight Engineering Release Engineering Table Tops Design Checklist Signature Release Manuf & Assembly Support MPP Review Engineering Control: RRS MRB/ENRT Structural Verification Qualification for EDU Accept/Workmanship: FLT Critical Design Review SV Test Support Environments Deployments Mass Properties Balance Engr Redline Incorporation Post Acceptance As Built Launch Ops Support Final Mass Prop Config Closeout A & I Support Mechanical Install Mass Prop Alignment

21. Thermal Design Process Modeling Tools (ThermalDesktop & SINDA/Fluint) Design Requirements (Systems Engineering) Preliminary Design & Temperature Predictions CAD Geometry (Structures Group) Updated Design & Temperature Predictions Prepare Pre-Test models of Test Conditions Update Models Based on Component Tests Correlate Test Model to Test Data & Update Flight Models Perform Thermal Balance/Thermal Vacuum Testing Pre-Flight Temperature Predictions Launch Support Cradle to Grave Program Support

22. Test and Launch Ops • Verify Space Vehicle Performance in Mission - Like Hardware and Software Combinations: • Verify Sub-System Functionality • Verify Key Performance Parameters • Verify System Fault Detection and Autonomous Recover Responses • Validate Selected Mission Sequences • Launch Operations: • Post-Ship Baseline Test • Payload Integration • Pre-Launch Checkout • System Environmental Testing: • I & T performs powered-on pre & post health checks for environmental testing • Team with Experience in all Aspects of Spacecraft ATLO