CU Aerospace Engineering: Systems Engineering, Page 1 Introduction to Aerospace Systems Engineering Henry ‘Lad’ Curtis Director of Engineering MicroSat.

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


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


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

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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


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


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


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

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(dB)

Flight Acoustic EnvelopeTaurusPegasusDelta IIFalconAthena IIEUROCKOTDNEPRESPA - Delta IV - 4m PLFMinotaur (Liftoff)ESPA - Atlas V

Examples of Systems Engineering Tasks on a BalloonSat …


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


• 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


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


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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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


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.



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


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 ?


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


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


• “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


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.



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


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


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


Additional InformationAdditional Information


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


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


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


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

CU Aerospace Engineering: Systems Engineering, Page 1 Introduction to Aerospace Systems Engineering Henry ‘Lad’ Curtis Director of Engineering MicroSat.

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