Sat Tech: Thermal Control Flashcards
Thermal Conditions in Space (3):
- Environment: Sun, Albedo & Atmos. Radiation, etc.
- Internal: Electronics, RTG & Batt., Propulsion sys.
- Maneuvers: Air-breaking, reentry.
Reasons why a thermal assessment is important (4):
- Electronics, mechanical components, propellant, etc. only operate well in a certain temperature range.
- Propellants require a well-defined temperature window.
• Extreme temperature gradients or large temperature fluctuations in a very short time cause thermal
distortion of components
– Structural damage
• Internal systems are heat sources and require heat dissipation.
Heat Sources: External (3)
1) Sun: Radiates all bodies in Solar System
2) Planets: Albedo (reflecting radiation from the sun)
3) Planetary IR Radiation
Heat Sources: Internal (3)
1) Propulsion System
2) Heaters: for propellant tanks heat
3) Electric Systems: creates resistance producing heat dissipation
Thermal Control Methods (3)
- Operation: choice of orbit or s/c alignment with external heat sources (Sun etc.)
- Surface properties: every object emits and absorbs energy in the form of IR radiation.
- Others: Use of heaters, heat pipes, radiators, shutters etc.
Thermal Control: Passive Methods (4)
1.- Material Choice:
• Material with preferable α/ε ratio to regulate equilibrium temperature
2.- Shadow:
• Use of (black) structures to block sunlight
3.- Multi-Layer Insulation:
• Reduces the heat loses by thermal radiation
• No thermal contact between layers
4.- Heat Pipes:
• Working fluid evaporates to vapour absorbing thermal energy
Thermal Control: Active Methods (3)
- Reflector mirrors & cooling down with helium
- Radiators: Heat transfer via conduction
- Shutters and Louvres: Mechanism to control the amount of incident energy