Sat Tech: Thermal Control

Question 1

Thermal Conditions in Space (3):

Answer 1

• Environment: Sun, Albedo & Atmos. Radiation, etc.
• Internal: Electronics, RTG & Batt., Propulsion sys.
• Maneuvers: Air-breaking, reentry.

Question 2

Reasons why a thermal assessment is important (4):

Answer 2

• 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.

Question 3

Heat Sources: External (3)

Answer 3

1) Sun: Radiates all bodies in Solar System
2) Planets: Albedo (reflecting radiation from the sun)
3) Planetary IR Radiation

Question 4

Heat Sources: Internal (3)

Answer 4

1) Propulsion System
2) Heaters: for propellant tanks heat
3) Electric Systems: creates resistance producing heat dissipation

Question 5

Thermal Control Methods (3)

Answer 5

1. Operation: choice of orbit or s/c alignment with external heat sources (Sun etc.)
2. Surface properties: every object emits and absorbs energy in the form of IR radiation.
3. Others: Use of heaters, heat pipes, radiators, shutters etc.

Question 6

Thermal Control: Passive Methods (4)

Answer 6

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

Question 7

Thermal Control: Active Methods (3)

Answer 7

1. • Reflector mirrors & cooling down with helium
2. • Radiators: Heat transfer via conduction
3. • Shutters and Louvres: Mechanism to control the amount of incident energy