Passive Thermal Control

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Passive Thermal Control

• Presented by
• Marc Jarmulowicz

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What is going on?

• Sun gives off radiation
• No atmosphere or convection to distribute energy
• Spacecraft must reflect and radiate unwanted
  energy to maintain temperatures for humans and
  electronics

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Diagram
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Physics

• Emissivity is the amount a material emits
  radiation
• A white material will emit very low amounts of
  energy, whereas a black material will emit a
  great deal of energy
• Absorptivity relates to the amount of radiation
  that a material will absorb from an energy source
• a white material absorbs very little radiation,
  while a black material will absorb a great deal
  of radiation

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Temperature requirements

• Satellite components (temperature range)
• Liquid Propellant 44.6 - 95 F
• Batteries 41 - 68
• Electronics 32 - 104
• Structural Elements -47 - 149
• Solar Arrays -146 - 212
• Infrared sensors -326 - -110

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The solution

• To maintain the internal temperature of a
  spacecraft, different levels of active and
  passive thermal control systems are used

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What is PTCS?

• A Passive System
• Low energy use
• Low maintenance
• Low cost
• Low weight

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Different Missions Different Solutions

• Deep Space Craft
• Extremely low energy
• Orbit may take craft close to Sun as well as Deep
  Space
• ISS
• High heat generation
• Space Shuttle
• Re-entry heat dissipation

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Exploration Satellites

• Multi-Layer Insulation
• Made of Aluminized Kapton, Gold plated
• Good at reflecting radiation both from the
  environment and back into the craft.
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• Optical Solar Reflectors (OSR)
• Panels used to reflect sunlight and radiate
  energy
• Made of Quartz tiles
• Louvers
• Bimetallic controlled vanes that expose or
  insulate the internals of a spacecraft to space.

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ISS

• MLI
• Insulates and reflects radiation
• Protects Kevlar from radiation damage
• Surface Coatings
• Changes e and a of any outer skin not protected
  by MLI
• Does not insulate as well as MLI, but is cheaper
• Heaters
• Used to protect active systems from damage under
  extreme circumstances
• Heat pipes
• Not effective enough for energy rejection, but is
  effective for air conditioning.

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Space Shuttle

• Reinforced Carbon-Carbon (RCC)
• Most important part of re-entry TCS
• Withstands temperatures of 3000 F
• High-temperature Reusable Surface Insulation
  Tiles (HRSI)
• Tiles used on the bottom side of the Space
  Shuttle to withstand 500 F re-entry
• Fibrous Refractory Composite Insulation Tiles
  (FRCI)
• Same as HSRI except three times the tensile
  strength and 100 deg F higher operating
  temperature
• Advanced Flexible Reusable Surface Insulation
  Blankets (AFSRI)
• Replaces the original LRSI (Low-Temperature
  Reusable Surface Insulation Tiles) with a lower
  weigh quilt like material
• Felt Reusable Surface Insulation (FSRI)
• Felt Reusable Surface Insulation Nomex material
  that makes up 50 of orbiter upper surface
• Thermal Barriers
• Ceramic cloth that helps insulate the orbiter
  from its own TCS

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Key concepts

• Radiation
• Emissivity and Absorptivity
• Temperature ranges
• In space
• In spacecraft
• Lightweight MLI and Ceramics

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Questions?