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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

1 Orbital ATK Proprietary

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


A Combination of Two Industry Leaders

Merger of Orbital and ATK was completed in February 2015


A New Global Space and Defense Leader


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


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


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


GEOStar Satellite Bus:

Modular Design Tailored to Customer Needs


5.0 kW

Emergence of GEOStar3 Product in 2014

Orbital Proprietary and Confidential

10

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)


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)


Cygnus Vehicle preparing for Acoustic Testing


13

FEMAP in Multi-Phase Satellite Design-Analysis

Life Cycle

Illustrated Overview of the Satellite Structure

Design Life Cycle


(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

15

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


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

17

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

Orbital ATK Proprietary

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

18

Spacecraft Temperature Contour and Deformed

Shape Shown in On-Orbit Deployed Configuration



19

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

20

CAD FEM Launch


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


CAD to FEM – Subcomponent CAD Geometry

Preparation

Solid objects are decomposed into basic shapes which are then used for meshing

22

Remove filets Create midsurfaces


CAD to FEM – Subcomponent CAD Geometry

Preparation

More complex shapes can be

efficiently decomposed using

FEMAP’s Meshing Toolbox


CAD to FEM – Mesh Connectivity

Subcomponents are then integrated using single DOF elements to model interfaces,

for which FEMAP Custom Tools are very useful


CAD to FEM – On-Spacecraft FEM

Integrate model to spacecraft

Verify the design loads and complete

integrated analysis



26

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


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


Mounting

Flange

ERM

Housing

Cup

Cone

Spring

Retainer

Detailed Solid

Mesh of Cup


29

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


Unformed Shape

Formed Shape

Corrugation Expanded

Corrugation Compressed


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


Unformed Shape Formed Shape

(Actual Deformation)

SPC and Rotation

Isometric View of Unformed Shape

SPC

Mesh Fidelity


Analysis and Results

Dynamic response and stress analysis performed on assembly

Modal and random test responses correlated very well with numerical predictions


Detailed Stress Analysis Contour - Random Modal Deformed Animation

Area of Peak Stress


33

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


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


First Mode

Transfer Function Comparison of Prediction and Test Response

For Random

Deformed Modal Shape – First Mode


36

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

37

Finite Element Model Test Plan Article Test



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)


Honeycomb Shear Stress Contour Plot Safety Margin Criteria Plot


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

39 Orbital ATK Proprietary Strain Field and Gage Placement

Test Instrumentation Plan

Thanks for your Attention!

Any Questions?


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