Design of Thermal Control
Sub-System(TCS)
Picosat course
May 18, 2006
IAA,National Cheng Kung University, Tainan
J. H. Chou
Department of Engineering Science
National Cheng Kung University
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Outline
I. Review of TCS key concepts
II. Design considerations
III. YamSat thermal design
IV. Summary
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I. Review
. Why do we need TCS for PicoSat?
. Working Temperature: sensors, electronics
and materials
. Temperature uniformity: thermal stress
. PicoSat environment: cold and near vacuum
. Energy source and sink
. Thermal balance and heat transfer path
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Picosat thermal environments
. Three phases:
.launch
.mission lifetime
.reentry self-destruction
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Key issues:
. Environment
. Components temperature specification
. Heat source
. Heat sink
. Heat transfer path and mechanisms
. Control techniques
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Typical temperature range for selected satellite components
Components
Typical temperature range, ℃
Batteries
5 to 20
Electronics
0 to 40
Infrared detectors
On-board computer
Propellant, hydrazine
Solar arrays
Structures
- 200 to – 80
- 10 to 50
7 to 35
- 100 to 100
- 45 to 65
Note: reference only. Check manufacturer’s data for details.
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II. TCS design considerations
Radiation Property
Values
Spacecraft Orientation
and Attitude
Radiation Computer
Program
(Geometric Math Model)
Thermal Control
Hardware Elements
Spacecraft Geometry
Electrical Power
Dissipation
Thermophysical
Property Values
Requirements
-Temperature Limits
-Survivability
Radiation
Exchange Factors
and View Factors
Thermal Analyzer
Computer Program
(Thermal Math Model)
Predicted Thermal
Performance
Comparison
Radiation
Absorbed on
Exterior Surface
ComponentLevel Tests
System-Level
Tests
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Some heat sources:
. Solar and planetary radiation
. Planetary reflection
. Equipment heat sources: electronic devices
batteries
propulsion
. Reentry atmospheric frictional heating
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Emitted
Radiation
Mean value of Direct
Solar Flux 1385+5 W/m2
P
Gs
Albedo (30+5)%
of Direct Solar, a
Low-Earth
Orbit Spacecraft
Earth Infrared
237+21 W/m2
q1
Earth
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Typical heat sinks:
. Satellite space environment (ultimate):
cold and near vacuum condition
. Equipment heat sink (intermediate):
special designed
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Basic heat transfer path and mechanism:
. Solid material: conduction
. Space: radiation
. Atmospheric air: convection (launch &
reentry)
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Available thermal control techniques:
passive control vs active control
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0.25 mil Mylar + 0.001mil aluminized surface
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cos 
F12 
(1  H ) 2
1
H 2  2H
F12  [1 
]
2
1 H
H  h/ R
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Qloss = Qabs,ex + Qabs,in
Qe= Qa
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Tokyo Institute of Technology
"CUTE" (CUbical Titech Engineering satellite)
•Size : 10 cm x10 cm x10 cm &Weight : 1 kg
•COTS(Commercial off-the-shelf) components
.Sun-synchronous polar orbit, Height 650km
Thermal analysis by ANSYS finite element method
package with space temperature of 3K
Estimate the max temperature is about 80 Celsius
degree, and the mininum temperature is -40 Celsius
degree
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Aalborg University, Denmark
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Taken from AAU
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Taken from AAU
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III. YamSat thermal design, NSPO
. New generation of sensors (payload)
.Smaller
. Cheaper
. Faster
. Better
. 10 cm3 x 1 Kg
. Internal space & power limited
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. Mission life duration: 1 month
. Altitude: 650 Km
. Orbit period: 16267 hours
. Power: GaAs and Si solar cells
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YamSat
Thermal Management: passive control,
black painting inside the satellite
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The YamSat TCS ensures the proper thermal environment for
YamSat and thermal interface control with the instruments.
Component Thermal Control
The TCS shall provide thermal control for all thermally
sensitive YamSat components.
Thermal Passive Control
The thermal control shall be achieved through passive
elements, as thermal blankets, insulation, and surface finishes.
Thermal Margins
For all components, an uncertainty margin of 5°C shall be
included in all cases so that the maximum or minimum
expected flight temperature can be determined.
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Selection of Thermal Control Materials
. Materials with low-outgassing characteristics to
avoid the contamination of other spacecraft
equipment.
. All electrically conductive layers of thermal
finishes shall be grounded to the vehicle structure.
. Thermal finishes and materials with low
degradations in solar absorptance.
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衛星軌道環境
Cold
case
Solar
constant
(W/m2)
1321.0
Hot case 1423.0
Earth
Albedo
radiatio coefficient
n(W/m2)
275.0
0.35
201.0
0.25
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Direct Incident Solar
Solar Constant
1423 W/m2 (Hot Case)
1321 W/m2 (Cold Case)
Albedo
Earth IR
Albedo Coefficient
0.35 (Hot Case)
0.25 (Cold Case)
275 W/m2 (Hot Case)
201 W/m2 (Cold Case)
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元件
Tmin（ﾟC） Tmax（ﾟC）
電池（充電）
0
45
電池（放電）
-20
60
CPU
-40
85
Microspectrometer
Magnetometer
-20
40
-40
85
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. Structure: 7075 T6
Al Plate
.Surface properties
. Isolators
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Significant conduction heat loss from components to
structure panels and may cause some unit temperatures,
especially the battery, lower than their allowable temperature
limits.
Thermal isolators were used for screws that fix components
to structure panels to avoid substantial conduction heat loss.
An appropriate combination of surface properties of outer
and inner sides of structure panels to maintain component
temperatures within their ranges.
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Application of thermal isolator
Isolator
Component
Isolator
Structure Panel
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Qualification margin
Acceptance margin
Uncertainties
Predicted
temperature
range
Uncertainties
Acceptance margin
Qualification margin
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VI. Summary
. Satellite environments
. Heating by sun and power dissipation
Worse hot and cold conditions
. COTS components vs ASIC
. Scale down vs New design
. Modular approach
. Passive thermal control:
Thermal isolators
Surface finishes/paints
Controlled duty cycles to manage power dissipation
. Reentry self destruction by atmospheric heating
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TCS design home work:
1. Specify your PicoSat’s missoin thermal
environment
2. Following the analysis of AAU,
estimate your PicoSat’s maximum and
minimum temperature
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References
1.Fortescue, P. W. and Stark, J. P. W. (eds.), Spacecraft
Systems Engineering, 2nd edition, Chapter 8.5 and Chapter
12, John Wiley and Sons, 1994
2.Gilmore, D. G. (ed.), Satellite Thermal Control
Handbook, The Aerospace Corporation Press, 1994
3.Larson, W. J. and Wertz, J. R. (eds.), Space Mission
Analysis and Design, Chapter 11.5, Microcosm, Inc. and
Kluwer Academic Publishers, 1992
4.Any basic heat transfer book for undergraduates
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5.Holmes, W. C., et al., TU Sat 1: A novel communication and
scientific satellite, 16th AIAA/USU Conference on Small
Satellites, 2002
6.Schaffner, J. A., The electronic system design, analysis,
integration and construction of the Cal Poly State University CP1
CubeSat, 16th AIAA/USU Conference on Small Satellites, 2002
7.Tsai J-R, “Thermal Analytical Formulations in Various satellite
Development Stages”, 8th AIAA/ASME Joint Thermophysics
and Heat Transfer Conference, St. Louis, Missouri, USA, June
2002.
8.Tsai J-R, “Satellite Thermal System Verification - Thermal
Balance Test and Thermal Vacuum Test”, 4th pacific International
Conference on Aerospace Science and Technology, Kaoshiung,
Taiwan, May 2001.
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