FEMAP Use in Mechanical Analysis for Design and
Test of GEOStar Satellites and Subcomponents
Andrew Sayles / Thomas McQuigg
Orbital ATK Space Systems Group, Mechanical Analysis and Test
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4/14/2015
Agenda
Introduction
Orbital ATK Space Systems Group (SSG)
SSG Mechanical Analysis and Test
− GEOStar Communication Satellites
− Science Satellites
− ISS Commercial Resupply Service
Primer on Satellite Design Requirements
FEMAP for Satellite Modeling
Example GEOStar Analysis with FEMAP:
1. Detailed Hold Down Release Mechanism
2. Specialized Mesh Approach in a Corrugated Wave Tube Assembly Model
3. Component Level Test Model Correlation for Test Prediction
4. Structural Test and Strain Prediction for Large Scale Structures
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A Combination of Two Industry Leaders
Merger of Orbital and ATK was completed in February 2015
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A New Global Space and Defense Leader
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Dulles campus is prime facility for Geosynchronous satellite manufacturing
5 Orbital ATK Proprietary *April 1982-July 2014
Over 800 Space Missions Since 1982*
78 Commercial Satellites
202 Interceptor & Target Vehicles
40 Space Payloads
78 Space Launch Vehicles 346 Sounding Rockets
77 Government Satellites
Premier Aerospace and Defense Customers
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Extensive Human and Physical Resources
Over 13,000 Employees Dedicated
to Aerospace and Defense Business
4,300 Engineers and Scientists
7,400 Manufacturing and
Operations Specialists
1,400 Management and
Administration Personnel
Facilities in 17 States With 19.6
Million Sq. Ft. of R&D,
Manufacturing, Test, Operations and
Office Space
6.1 Million Sq. Ft. Owned
5.4 Million Sq. Ft. Leased
8.1 Million Sq. Ft. U.S.
Government Owned
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Orbital ATK Space Systems Group
SSG Mechanical Analysis/Test Working Out of Dulles, VA
Focuses on Satellites and Space Systems Areas of Our Business
− Commercial Satellites
− Science Satellites
− Commercial Resupply Mission (Cygnus Service Module)
− National Security Satellites
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GEOStar Satellite Bus:
Modular Design Tailored to Customer Needs
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5.0 kW
Emergence of GEOStar3 Product in 2014
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Satellite Design: Requirements and
Environments
Sources of Mechanical Design Requirements
Structural requirements are derived based on multiple phases of the satellite mission
Manufacture and Assembly
Transport and Handling
Testing
Launch and Ascent
On-orbit Mission Operations → satisfies business needs of customer
Re-entry and landing (if applicable)
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GEOStar2 Sine Vibration Test
Antares Launch of Cyngus
Vehicle at Wallops Island
Satellite Environments
Multiple environments must be considered during analysis:
Quasi-static (launch vehicle engine thrust and ascent)
Dynamic
− Random/Acoustic (LV engine, aerodynamic loading, energy reflection in fairing)
− Sine vibration (LV engine)
− Shock (separation from LV, deployment of appendages)
Thermal (on-orbit loading)
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Cygnus Vehicle preparing for Acoustic Testing
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FEMAP in Multi-Phase Satellite Design-Analysis
Life Cycle
Illustrated Overview of the Satellite Structure
Design Life Cycle
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(1) (2) (3)
(4)
(5) (6)
(7) (8)
(9)
1. CAD Geometry Design Generation
2. Finite Element Model Generation
3. Modal Analysis
4. Dynamic Analysis for LV Environments
5. Design Load Case Generation
6. Stress Analysis (Dyn/QS/Thermal)
7. Margin of Safety Reporting and Design Iteration
8. Testing – Verification and Validation
9. Completed Design for System Level Testing and
Launch
0.01
0.1
1
10 100
Inp
ut (g
)
Frequency (Hz)
AMZ-4A As-Run Z Axis Protoflight Input Notch
AMZ-4A Protoflight Input Envelope Ariane 5 MUA Protoflight Longitudinal Input
AMZ-4A Z Axis Protoflight PredictedNotched Input
AMZ-4A As-Run Z Axis ManualProtoflight Input
AMZ-4A As-Run Z Axis ProtoflightControl channel
Ariane FCLA Z SRS EnvelopeScaled to Protoflight (Q=20)
Ariane FCLA Minima Scaled to Protoflight acc_op1s111s_Z_AMP acc_op1s121s_Z_AMP
acc_op2s111s_Z_AMP acc_op2s121s_Z_AMP acc_bpa_sine_dq_Z
LAE-1Z REFL-EIF-5Z REFL-WIF-5Z
Analysis Types and Requirements:
Modal
Free boundary conditions used to
assess separation of elastic modes
Fixed-base modal analysis
characterizes dynamic behavior
Evaluates compliance of S/C with LV
requirements
Component frequency requirements
are based on separation from support
structure/vehicle modes
S/C Primary Mode separation from
launch vehicle modes is key for
reducing loads generated by coupling
between the two vehicles
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Example Deformed Shape – First Bending
CLA Interface SRS and As-Run Spacecraft Sine Test
Analysis Types and Requirements:
Dynamic
Dynamic modal characteristics are evident in various types of dynamic environments
Sinusoidal vibration – oscillating load with a specific frequency
Random vibration – amplitude and frequency of load are random in nature
Acoustic excitation – defined by sound pressure level at a given frequency and somewhat
random in nature
Shock Input – short duration high frequency acceleration event and rapid attenuation
Dynamic loads are typically a source for derivation of design loads
Pre-test/flight predictions used to derive loads for stress analysis
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Acoustic Vibration Test Response Sine Vibration Test Prediction – Transfer Function
Analysis Types and Requirements
Quasi-Static
Loads that do not vary in time or
magnitude
Point loads (specific application)
Body loads (gravitational, LV
acceleration)
Boundary Displacement (applied or
global-local approach)
Loads are governed by specific
Launch Vehicle or on-orbit mission
requirements
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Panel Facesheet Failure
Index Contour Plot
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
-3 -2 -1 0 1 2 3
Axia
l A
ccele
rati
on
(g
)
Lateral Acceleration (g)
Quasi-Static Accelerations (Flight) for Launch Vehicle Envelope
Proton User's Guide Rev 7 &
STAR2.4e ICD
Ariane 5
Sea Launch/Land Launch
Soyuz
HIIA
Star2.4e Heritage Design Load
Envelope
Negative acceleration is compression Positive accleration is tension
Launch Vehicle QS Load
Factor Envelope
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Analysis Types and Requirements
Thermoelastic
Temperature loads derived from Thermal Group analysis or design requirement
Apply temperatures to finite element mesh as nodal loads
Multiple loading conditions and combinations often considered to identify worst case condition
Conduction is used to derive nodal loads when detailed temperature gradients are not available
Distortion analysis is used to find resulting displacements (horn pointing, clearance)
Coupled with vendor distortion analysis of reflector surface this feeds into the antenna’s accuracy and performance
Strength analysis is used to validate structure design
Common problem is material CTE mismatch
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Spacecraft Temperature Contour and Deformed
Shape Shown in On-Orbit Deployed Configuration
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FEMAP Models of
Orbital ATK Satellites
FEMAP’s Role in Satellite Design
Efficiency in model creation and model management is key to producing analyses
that support the program’s schedule
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CAD FEM Launch
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CAD to FEM - Overview
Antenna support structure are comprised of
Composite panels
Metallic brackets,
Mechanical fasteners
Bonded clips
Other specialized features that support mission concept of operations
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CAD to FEM – Subcomponent CAD Geometry
Preparation
Solid objects are decomposed into basic shapes which are then used for meshing
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Remove filets Create midsurfaces
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CAD to FEM – Subcomponent CAD Geometry
Preparation
More complex shapes can be
efficiently decomposed using
FEMAP’s Meshing Toolbox
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CAD to FEM – Mesh Connectivity
Subcomponents are then integrated using single DOF elements to model interfaces,
for which FEMAP Custom Tools are very useful
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CAD to FEM – On-Spacecraft FEM
Integrate model to spacecraft
Verify the design loads and complete
integrated analysis
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Modeling Example 1: Reflector Retention and
Release Mechanism
Example 1: Deployment Introduction
GEOStar spacecraft travel to orbit in a “stowed” position.
Loads induced from launch driven stowed design loads
Once on-orbit, solar arrays, reflectors and other structures are deployed
Deployment mechanisms must function reliably, since there is no second chance for on-orbit failure
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CAD
FEM
Stowed Deployed
Example 1: Model Summary
Internal assembly bolted are modeled with preload
Contact with friction defined at cup/cone interface as well as others
Reflector interface loads are derived from on-spacecraft analysis considering acoustic and sine loading from launch vehicle environment
Interface loads are applied for detailed stress analysis
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Mounting
Flange
ERM
Housing
Cup
Cone
Spring
Retainer
Detailed Solid
Mesh of Cup
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Modeling Example 2:
Specialized Meshing Approach of Corrugated Waveguide
Example 2: Corrugated Tube
Problem Statement
Process forms tube from nominal (straight) into desired shape (bend in corrugations)
Forming process changes angle of corrugations
Geometry was not available for formed shape
Detailed stress analysis was required for formed configuration
Generating consistent mesh that accurately represented the formed shape in expanded and
compressed corrugations proved difficult
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Unformed Shape
Formed Shape
Corrugation Expanded
Corrugation Compressed
Example 2: Corrugated Tube
Meshing Approach
Unit rotation was applied to sections of mesh, constrained with RBE2 rigid elements
and SPC
Custom Tool command “Nodes move by Deform” under Post Processing toolbar
Corrugations were compressed and expanded as observed in manufactured shape
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Unformed Shape Formed Shape
(Actual Deformation)
SPC and Rotation
Isometric View of Unformed Shape
SPC
Mesh Fidelity
Example 2: Corrugated Tube
Analysis and Results
Dynamic response and stress analysis performed on assembly
Modal and random test responses correlated very well with numerical predictions
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Detailed Stress Analysis Contour - Random Modal Deformed Animation
Area of Peak Stress
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Modeling Example 3: Model-Test Correlation of an Electronics Assembly
Example 3: Electronics Assembly
Electronics assembly required dynamic assessment and stress analysis
Mass = 100 lbm
Model uses plates, solids, and concentrated mass elements for large chips
FEMAP Layering, grouping features enabled efficient model management
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Detailed Finite Element Model Solid Model
Example 3: Electronics Assembly
Analytically predicted first major mode nearly identical to test
Modal and random test responses correlated very well with numerical predictions
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First Mode
Transfer Function Comparison of Prediction and Test Response
For Random
Deformed Modal Shape – First Mode
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Modeling Example 4: GEOStar Primary
Structure Static Load Test
Example 4: GEOStar Primary Structure Static
Load Test Introduction
Primary structure static load used to verify workmanship and design loads
Forces are applied to structure to simulate various loading conditions
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Finite Element Model Test Plan Article Test
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Example 4: GEOStar Primary Structure Static
Load Test Analysis Results
Attach NASTRAN .OP2 files to large spacecraft primary structure FEMAP models
Use of global plies is ideal for core shear stress plot generation for a panel and load
case envelope when composite panels have multiple layups/ply counts associated
with them
Import analysis results function is easily used to import .CSV raw analysis results
generated using other in-house analytical tools (spreadsheets or MATLAB Scripts)
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Honeycomb Shear Stress Contour Plot Safety Margin Criteria Plot
Example 4: GEOStar Primary Structure Static
Load Test Strain Predictions
Strain gages placed at areas of interest on the structure
Finite Element Model predictions are used as justification to continue with test
FEMAP enables efficient composite element processing
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Test Instrumentation Plan
Thanks for your Attention!
Any Questions?
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