CU Aerospace Engineering: Systems Engineering, Page 1
Introduction to Aerospace Introduction to Aerospace Systems EngineeringSystems Engineering
Henry ‘Lad’ CurtisDirector of Engineering
MicroSat Systems Inc.Littleton, Colorado
25 September 2007
CU Aerospace Engineering: Systems Engineering, Page 2
OutlineOutline
• 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
CU Aerospace Engineering: Systems Engineering, Page 3
Change Board
SC CAD Model
Trade Studies
ICD’s
System Design Meeting
Risk Board
CDRPDR
Detailed Analysis
Engineering Change Requests
Op’s Handbook
Eng. Ops Support
6 Months to10 Years
S/C Performance Reports
Science Data
Life Cycle of a Spacecraft ProjectLife Cycle of a Spacecraft Project
Pro
du
ctP
eop
leE
ven
ts
Requirements Design Assembly, Integration & Test Mission OpsConcept
Design Reference Mission
S/C Requirements
Document
Environments Definition
Verification Plan
Core Tech Team
Risk Mgmt Plan
SRR
SC Verification Matrix
Mfg. Procedures Test Procedures
Non-conformance Documents
LaunchEnv.Test
18 Months to 4 Years
Test Reports
Thermal and Space Simulations
Con Ops Plan
ROM Cost
S/C Desc.
Subcontractors ID’d
Mission Analysis
AwardContract
6 Months to2 Years
CU Aerospace Engineering: Systems Engineering, Page 4
Mission System
What is Systems Engineering?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
Spacecraft System
Power Subsystem
Payloads
Structure Subsystem
Data Subsystem
Thermal Subsystem
CU Aerospace Engineering: Systems Engineering, Page 5
What are the Characteristics of a Systems Engineer?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
CU Aerospace Engineering: Systems Engineering, Page 6
What Does a Spacecraft Systems Engineer Do?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
LV Acoustic Spectrum ComparisonAcceptance Levels
100.0
105.0
110.0
115.0
120.0
125.0
130.0
135.0
140.0
10 100 1000 10000Frequency (Hz)
Soun
d Pr
essu
re L
evel
(dB)
Flight Acoustic EnvelopeTaurusPegasusDelta IIFalconAthena IIEUROCKOTDNEPRESPA - Delta IV - 4m PLFMinotaur (Liftoff)ESPA - Atlas V
Examples of Systems Engineering Tasks on a BalloonSat …
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Mission AnalysisMission Analysis
• We Want to Maximize Mission Duration– What Events Or Physics Limits The Mission Duration?
Life Limiter Estimated Life Comments
Battery Life 3 Hours at –30 Degrees C Need Heaters to Increase This to 5 hrs
Balloon Failure and Descent 5 Hours Based on Normal Winter Atmosphere
Data Collection 4 Hours with collection every 10 seconds
Can’t Record Balloon Failure and Descent
Requirements Design Assembly, Integration & Test Mission OpsConcept
• 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
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Requirements and Design ControlRequirements and Design Control
Level 2: System
BalloonSat System
Requirements Document
Ground Chase Requirements
Document
Launch Vehicle
Requirements Document
Change Approval
Board
Power Allocations to Subsystems
SC Test Plan
Mission Definition Document
SC CAD Model
Mass Allocations to Subsystems
Environments Definition
Eng. Change
Form
Payload Interface/Constraints Doc
The System Engineer Documents and Controls Changes to the System and Subsystem Designs
Requirements Design Assembly, Integration & Test Mission OpsConcept
Level 3: Subsystem
Payload Requirements
BalloonSat Subsystems
Balloon, Tether, GPS Requirements
Laptop and Chase Vehicle Requirements
Power
Att. Control
Structures
Software
Cmd & Data
Thermal
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CU Aerospace Engineering: Systems Engineering, Page 9
What is a Requirement?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
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Trade StudiesTrade Studies
A Trade Study is a Multi-variable Analysis That Defines a New Requirement or a Design Solution
Steps:1. Clearly Define a Desired Objective of the Trade Study.2. Select System Parameters That Drive the System Design. 3. Vary the Value of Parameters to Understand the Benefits and Costs of
Each Against the End Goal.4. Apply Judgment to Reject Unreasonable Options. 5. 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.
Requirements Design Assembly, Integration & Test Mission OpsConcept
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BalloonSat Trade StudyBalloonSat Trade Study
Step 2: What Parameters Influence the Number of BalloonSats That Can Be Flown on the Balloon Mission?
Parameter
Step 3: Point Design
Number of BalloonSats
nbs
Calculated Mass of Each BalloonSat
mb
Design A 1 5 kg
Design B 5 1 kg
Design C 10 0.5 kg
Design D 20 0.25 kg
– 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
Step 4: Reject Unreasonable Designs
Reject: One BallonSat Hardly Meets the Goal
Good Compromise – Meets Goal and Requirement
Good Compromise – Meets Goal and Requirement
Reject: Technologies Available to Student Insufficient to Build a 0.25 kg BalloonSat That Does Anything
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Managing the Design: TPM’sManaging the Design: TPM’s
• Technical Performance Measures (TPM’s) Are Selected From System Characteristics Known To Drive the Design Result– BalloonSat TPM’s ?
Requirements Design Assembly, Integration & Test Mission OpsConcept
Mass, Power, Amount of Data Collected
• Is Trend Dependable and No Action is Needed?• Act Now to Avoid More Drastic Acts in the Future?
• Margin on a TPM Is Set At the Start of a Program Based on Engineering Experience
• TPM Trends Are Used to Trigger Design Changes
Mass Limit
Mas
s (k
g)
Concept CDRPDR Test
1.00
0.25
0.50
0.75
TimeLaunch
25% 20
% 15%
5%
Mass Margin Plan
0%
Margin Violated. Decision Needed!
Current Best EstimateTrend
Current Date
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Integration and TestIntegration and Test
• Prove the System Meets Design RequirementsIdentify Requirements to Be
Verified in Each Event
Perform Verification: Analysis, Demo, Inspect, Test
Document Results
Confirm Each Requirement Has Been Verified Satisfactorily
Requirements Design Assembly, Integration & Test Mission OpsConcept
• “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
– 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
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Launch and Mission OperationsLaunch 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.
Requirements Design Assembly, Integration & Test Mission OpsConcept
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ReviewReview
• 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
CU Aerospace Engineering: Systems Engineering, Page 16
AcronymsAcronyms
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
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References and ResourcesReferences 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
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Additional InformationAdditional Information
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Typical Organization of a Gov. Spacecraft ProgramTypical Organization of a Gov. Spacecraft Program
Gov/Civilian Customer
Payload/Sensor Provider Launch Vehicle ProviderSpacecraft Bus Provider
Program Manager
Chief Systems Engineer
Structures and
Mechanisms
Systems Engineering
Telecommunications
PowerPropulsion
Command & Data
Handling
Integration and Test
Requirements and
Verification
Mission Analysis
Mission Operations
Thermal
Payload and LV Integration
System Design Lead
Specialty Engineers
Program Engineer
Ground Control System Provider
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Structures Design Flow ProcessStructures Design Flow Process
RequirementsLevel 1, 2 and Derived
LV Environments, Mass Prop, I/F EnvelopeInstrument &P/L Alignment, Pointing, and FOV
Grounding & ESDThermal Control
Material CompatibilityRequirement Verification
Preliminary DesignSV & Structure 3-D Solid Model
Mass Properties/ MELDrawing Tree
Sub-System I/F
Structural Analysis
Structural CriteriaStiffness, Loads
ManufacturingTooling
Assembly Methods
PreliminaryDesign Review
CriticalDesign Review
Engineering Release
Engineering Table TopsDesign Checklist
Signature Release
Engr Redline IncorporationPost Acceptance
As Built
Manuf & AssemblySupport
MPP ReviewEngineering Control: RRS
MRB/ENRT
Structural Verification
Qualification for EDUAccept/Workmanship: FLT
A & I SupportMechanical Install
Mass PropAlignment
SV Test Support
EnvironmentsDeployments
Mass PropertiesBalance
PreliminaryRequirements
Update
Flight DesignDesign & Model
Updates
Flight
ConceptDesign &Review
Initial Model
Launch OpsSupport
Final Mass PropConfig Closeout
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Thermal Design ProcessThermal Design Process
Cradle to Grave Program Support
Design Requirements (Systems Engineering)
CAD Geometry(Structures Group)
Preliminary Design & Temperature
Predictions
Update Models Based on Component Tests
Prepare Pre-Test models of Test Conditions
Perform Thermal Balance/Thermal Vacuum
Testing
Pre-Flight Temperature Predictions
Launch Support
Modeling Tools(ThermalDesktop &
SINDA/Fluint)
Correlate Test Model to Test Data & Update
Flight Models
Updated Design & Temperature Predictions
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Test and Launch OpsTest 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