University of Minnesota

Senior Design II

Nanosat-VFinal Design Review

6 May 2008Minneapolis, MN

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Project Objective

• The aim of this project is to perform and validate thermal, structural and vibrational analyses on the Nanosat-5 satellite.

• The tests will ensure that the vehicle is capable of withstanding loads, vibrations and temperatures, as specified by the University Nanosat Program.

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Thermal Analysis (THRM)

Subsystem Overview

Thermal Analysis TeamDavid Hauth

Chuck HisamotoMichael Legatt

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Objectives of Thermal Analysis

• Assemble list of material properties, temperature critical component profiles

• Provide thermal models of Goldeneye with nodes for each of the temperature critical components onboard

• Determine hot case and cold

case thermal boundary conditions

• Determine temperature history for each temperature critical component

• Assemble list of material properties, temperature critical component profiles

• Provide thermal models of Goldeneye with nodes for each of the temperature critical components onboard

• Determine hot case and cold

case thermal boundary conditions

• Determine temperature history for each temperature critical component

Component Box Placement

• 3 component boxes– 2 for electrical components

• GPS Receiver, Radios, etc.

– 1 dedicated for batteries• Strict requirements for

coatings and narrower allowable temperature range

• IMU• Flight Computer

Battery Box

IMU

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Component BoxesFlight Computer

Thermal Analysis (THRM)

David Hauth

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Theory

• Conventional heat transfer through three modes– Conduction– Convection– Radiation/Re-Radiation

• Most significant means of transferring energy to spacecraft• Sources:

– Solar Radiation» Sun radiates at black body temperature of 5777K» Mean flux of 1367 W/m^2

– Reflected Solar Radiation (Albedo)» Reflected and absorbed light accounts for 100% of energy received from sun» Dependent on ground cover» Goldeneye uses a table of average albedo for every 10 degrees of latitude

– Earth IR Radiation» Thermal equilibrium requires radiating energy equal to the amount absorbed» Higher temperature bodies emit shorter wavelengths of energy» Earth re-emits energy in the IR spectrum» Goldeneye uses a table of average IR fluxes for every 10 degrees of latitude

– Alodine Aluminum (6061 T6)• Thermal conductivity: 167 W/m2

• Specific Heat: 896 J/kg-K• Absorptivity/emissivity:

Solar: .35IR: 0.1

– Emcore Triple Junction GaAs Solar Cells• Annealed at 200 deg C• Absorptivity/emissivity:

Solar: .92IR: .89

– Nusil CV10-2568 Controlled Volatility RTV Ablative Silicone Adhesive• Operating Temperature Range (deg C): -115 to 240

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Analysis Input: Material Properties

Internal Power Generating Components

Thermal Analysis Methodology

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Thermal Analysis (THRM)

Michael Legatt

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Hot/Cold Orbits• Which orbit is hottest, coldest?• Heat Loads

– Solar Flux – Cosmic Microwave Background

Radiation– Internal Power Generation/Dissipation

• Use Beta angle

–Earth Albedo–Earth Infrared

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Beta Angle

Solar Eclipse begins at Beta-star

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Hot Case

Cold Case

Occurs at:

-Beta=Beta-star

-Lowest altitude=250km

Occurs at:

-Beta=0

-Highest altitude=1000 km

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For each satellite face, MatLab/Simulink provides:• Earth IR flux and view factor• Earth Albedo flux and view factor• View Factor to Space

MatLab Code Assumptions– Fluxes are date/time, attitude, altitude, orbital position– Earth Albedo, Earth IR latitude dependent– Input time, RAAN, inclination, and altitude, attitude – Solar Flux: 1327 – 1414 Watts/m2

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Thermal Boundary Conditions

Meshing Conditions

• ANSYS auto-generates mesh based on input of element sizes– ANSYS picks element geometry type: octahedral (cube) or

tetrahedral (pyramid)• Mesh size (approximate): ~1.0 cm• ~760,000 Nodes

• Meshing Refinement– ~5 million nodes

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Thermal Analysis (THRM)

Chuck Hisamoto

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Temperature Critical Components

ComponentOperating Temperature

[deg Celsius]

Storage Temperature [deg Celsius]

RTD Computer -20 to 70 -55 to 125

NovAtel GPS Receiver -40 to 85 -40 to 95

Kenwood TH-D7A radios -20 to 60 N/A

SA-60C GPS antennas -40 to 85 -50 to 90

Sanyo N-4000DRL batteries 0 to 40 -30 to 50

American Power D150-15/5 power supply -25 to 85 -40 to 125

HG1700 Inertial Measurement Unit -30 to 60 -45 to 80

HMR2300 Three Axis Magnetometer -40 to 85 -55 to 125

Worst Hot case, Sun side

Allowable Temperature Range: -115 to 240 deg C

Cells Annealed at 200 deg C

Hot case, bottom

Allowable Temperature Range: -115 to 240 deg C

Hot case, warmer near Standoffs

Allowable Temperature Range: -115 to 240 deg C

Hot case, Isogrids, Standoffs

Allowable Temperature Range: -115 to 240 deg C

Hot case, Battery Box

Allowable Temperature Range: 0 to 40 deg C

Hot case, Component Box (Radio)

Allowable Temperature Range: -20 to 60 deg C

Hot case, Inertial Measurement Unit

Allowable Temperature Range: -30 to 60 deg C

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Thermal Performance – Hot Case

ComponentActual Temperature Range

(deg C)Allowable Temperature Range

(deg C)Pass/Fail

Min Max Min Max  Satellite Solar Panels/Cells -22.41 122.76 -115 240 Pass

   Cells 

Annealed: 200            Battery Box 21.588 23.494 0 40 Pass          Component Box 28.952 33.808 -40 85 Pass

(ADNCS, GPS, etc)                    Component Box 50.749 55.065 -20 60 Pass

(Radios)                    Flight Computer 55.281 58.769 -20 70 Pass          IMU 44.647 46.555 -30 60 Pass

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Thermal Performance – Cold Case

Allowable Temperature Range: -115 to 240 deg C

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Cold case, hot face/cold face

Allowable Temperature Range: -115 to 240 deg C

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Cold case, Isogrids/standoffs

Allowable Temperature Range: -115 to 240 deg C

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Cold case, Component Box (Radios)

Allowable Temperature Range: -20 to 60 deg C

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Cold case, Battery Box

Allowable Temperature Range: -30 to 60 deg C

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Thermal Performance – Cold Case

ComponentActual Temperature Range

(deg C)Allowable Temperature Range

(deg C)Pass/Fail

Min Max Min Max  Satellite Solar Panels/Cells -35.329 29.645 -115 240 Pass

   Cells 

Annealed: 200            Battery Box -19.982 -19.071 -30 50 Pass          Component Box -14.388 -12.524 -40 85 Pass

(ADNCS, GPS, etc)                    Component Box -20.045 -17.584 -20 60 Fail

(Radios)                    Flight Computer -14.949 -14.442 -55 70 Pass          IMU -17.539 -17.003 -40 85 Pass

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Design Conclusions

Hot Case

•All temperature critical components survive orbit within operating ranges•Heat accumulated on “hot side”

-Satellite slow spin maneuver-Addition/changes to coatings

Cold Case

•Radios component box is slightly out of storage temperature range.

-Need for heaters-Small generation needed

•All other components survive within range

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Acknowledgements

•Minnesota Supercomputing Institute-H. Birali Runesha, PhD., Director of Scientific Computing and Applications- Ravishankar Chityala, PhD., Scientific Development and Visualization Laboratory- Nancy Rowe, Scientific Visualization Consultant

•Tom Rolfer, Honeywell International Inc.•Gary Sandlass, MTS Systems Corporation

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Supporting Slides Follow

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References

• Bitzer, Tom. Honeycomb Technology. 1997.• Curtis, Howard. Orbital Mechanics for Engineering Students. 2005.• Gilmore, David (editor). Spacecraft Thermal Control Handbook. Vol.I.

2002.• Griffin, Michael and French, James. Space Vehicle Design. 2nd ed. 2004.• Kaminski, Deborah and Jensen, Michael. Introduction to Thermal and

Fluids Engineering. 2005.• Modest, Michael. Radiative Heat Transfer. 2nd ed. 2003.

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Supporting Slides-Task Breakdown

• Selection of satellite structure geometry, materials, coating and isogrid patterns.• Design/modifications of body geometry 100% Complete• Design component locations/mounting 100% • Design torque coil mounting 100% • Body and housing material selection 100% • Selection of thermal coating 100% • Implement isogrid patterns 100%

• Familiarization of software environment for analysis.• ProE 100% • Ansys 100% • Import methods 100%

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Task Breakdown, cont’d.

• Thermal analysis.• Receive determined component locations 100% Complete• Obtain relevant thermal constants 100% • Obtain relevant material properties 100%• Orbit propagation code for case determination 100% • Determine boundary conditions 100% • Generate thermal model for component heat sources 100% • Run simulations/verify results 50%

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Supporting slides for mike 1

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Satellite Structure

GPS Direct Signal

AntennasSolar

Panels

Lightband Interface

High Gain Antenna41

Supporting slides for mike/dave 2

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Project Scope

– Thermal• Provide thermal models of Goldeneye with nodes for

each of the temperature critical components onboard • Provide complete list of heat sources and their profiles• Determine orbit hot and cold cases• For each component and at each node of the thermal

models determine: – Operating temperature: Temperature at which

the component will function and meet all requirements

– Non-operating temperature: Component specifications are not required to be met. Component can be exposed in a power off mode. If turned to power on mode, damage must not occur

– Survival temperature: Permanent damage to the component

– Safety temperature : Potential for catastrophic damage 43

Boundary Conditions:– Internal Heat Generation

• IMU – 9.7 Watts (operational)• Computer – 9 -19 Watts• Battery < 1 Watt• Component Box 1 (ADNCS Microprocessor, Converter):

– Cold: 1 Watt– Hot: 14 Watts

• Component Box 2 (Radios)– Cold: 3 Watts– Hot: 26 Watts

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Thermal Analysis: Boundary Conditions

ANSYS– Model is much to robust for computing resources– Need to simplify our analysis

• Reduce node refinement at non-critical points• Eliminate re-radiation between some internal components:

– Most likely from boxes to other boxes

• Shorten time steps (length of analysis)– Currently doing 6 orbits

– Analyze Thermal Results

• Design changes if necessary– Test Convergence / Accuracy

Thermal Analysis: Future work

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Top Level Requirements

Requirement Number Requirement Type Verification Document Status

THRM-1Assemble list of material properties, temperature critical

component profiles research GEN-ANA-0001_A verified

THRM-2

Provide thermal models of Goldeneye with nodes for each of the temperature critical components onboard analysis GEN-ANA-0001_A verified

THRM-3Determine hot case and cold case thermal boundary

conditions analysis GEN-ANA-0001_A verified

THRM-4Determine temperature history for each temperature

critical component analysis GEN-ANA-0001_A verified

Provide thermal histories for all temperature critical components under hot and cold worst cases.Provide thermal histories for all temperature critical components under hot and cold worst cases.

Thermal Boundary Conditions -Heat Fluxes

-Fluxes are date/time, attitude, orbit dependent use Simulink/M-files -Double quadruple integrals+ 832 lines=1.5 - 3 hrs run time per 1 orbit

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Boundary Conditions:– Solar Flux: 1327 – 1414 Watts/m2

– Earth Albedo– Earth IR

Source: http://www.tak2000.com/data/planets/earth.htm Extracted from: Thermal Environments JPL D-8160

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Thermal Boundary Conditions - Albedo

-Fluxes are date/time, attitude, orbit dependent use Simulink/M-files -Fluxes are date/time, attitude, orbit dependent use Simulink/M-files

Hot case, Hot face

Hot case, Component Box (GPS receiver, ADNCS, etc)

Allowable Temperature Range: -40 to 85 deg C

Hot case, Flight Computer

Allowable Temperature Range: -20 to 70 deg C

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Cold case, Component Box: GPS, ADNCS, etc

Allowable Temperature Range: -40 to 95 deg C

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Cold case, Flight Computer

Allowable Temperature Range: -55 to 125 deg C

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Cold case, IMU

Allowable Temperature Range: -40 to 85 deg C