Design of Thermal Control Sub-System(TCS)

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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
- 200 to 80 On-board computer
- 10 to 50 Propellant, hydrazine
7 to 35 Solar arrays -
100 to 100 Structures
- 45 to 65   Note reference only. Check
manufacturers data for details.
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II. TCS design considerations
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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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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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Qloss Qabs,ex Qabs,inQe 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 5C
  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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??????
Solar constant (W/m2) Earth radiation(W/m2) Albedo coefficient
Cold case 1321.0 275.0 0.35
Hot case 1423.0 201.0 0.25
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Direct Incident Solar Solar Constant 1423 W/m2
(Hot Case) 1321 W/m2 (Cold Case)
Albedo Albedo Coefficient 0.35 (Hot Case) 0.25
(Cold Case)
Earth IR 275 W/m2 (Hot Case) 201 W/m2 (Cold Case)
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?? Tmin(?C) Tmax(?C)
??(??) 0 45
??(??) -20 60
CPU -40 85
Micro-spectrometer -20 40
Magnetometer -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
• Specify your PicoSats missoin thermal
  environment
• Following the analysis of AAU, estimate your
  PicoSats 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.