1 spacecraft thermal design introduction to space systems and spacecraft design space systems design
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SpacecraftThermal Design
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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What are the conditions the spacecraft must face in space?
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Spacecraft Thermal Design
1. What is the source of heating and cooling for a s/c in space?a) Sun, internal, earth, moon, other planets,
atmospheric friction, micrometeorites
b) Radiation to cooler environment – deep space, other components
2. How does the thermal conditions in space differ than on the ground?
a) No natural air convection source to conduct heat to or from areas of the spacecraft
b) Vacuum – extreme, fast temperature variations
3. What are the extremes that a spacecraft will see in space?a) Sunlight vs eclipse
b) Operation extremes – Tx, Thrusters
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4. What is the range of temperatures that the s/c components can operate?
a) -55C to 125C Military Specifications
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
5. Will the space environment change over time in space?
a) Solar cycle, orbit changes due to perturbations & seasons
Spacecraft Thermal Design
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1. Conduction and radiation
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
2. Spot electrical cooling with devices such as peltrier coolers.
3. Move heat from hot areas to cool areas by conduction, fluids and heat pipes.
How is heat transferred in the space environment?
Spacecraft Thermal Design
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Sources: (where heat comes from) Sinks: (where heat goes)
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Space Environment
Heat generated internally
Spacecraft Thermal Design
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How will the s/c thermal requirementschange with the operational scenario?
Internal heat generation and dissipation
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
1. When transmitters are on
2. When thrusters are firing
3. When solar arrays are deployed
5. When spacecraft fuels are used
4. When satellite orientation is changed
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Conditions for s/c equipment
•Non operating temperature range
•Operating temperature ranges
•Switch-on temperature limit
Design limits of the devices
Hot and cold turn on
Damage occur at extremes
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Spacecraft Thermal Design
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Spacecraft Thermal Design
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Effects of temperature ranges on components
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Spacecraft Thermal Design
Temperature
Electronics Too Low Too High
Permanent
damage
Operates out of design ranges
Operates incorrectly
Permanent
damage
Operates incorrectly
Solar Arrays
Upredictable
Batteries
Better efficiency Lower efficiency
Poor efficiencyCan’t charge
Better efficiency (to a point)
Stress components
Too Low Differential Too HighStructuresExcess stressesStresses
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Thermal control of components
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Spacecraft Thermal Design
How do you control thermal conditions on a spacecraft?
Thermal coatings on exterior
Thermal coatings on interior
Change passivity and emissivity of exterior surface of spacecraft
Change to cool off or head up spacecraft exterior surfaces
Move heat from subsystem boxes to other parts of spacecraft
Move heat from interior components to boxes
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Methods of heat transfer
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Spacecraft Thermal Design
ConvectionHeat transferred by liquid or gas
ConductionHeat transferred in a solid or non circulating fluid
RadiationHeat transferred by electromagnetic waves
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Analysis
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Spacecraft Thermal Design
Conduction
Q = in watts heat flow
k = thermal conductivity (W*m-1K-1)
A = cross sectional area = m2
x = path length – m
T = temperature in K (273 + T0C)
A
Q
T2 T1
Q = (T1-T2) watts/m2kAx
QAssumes not loss from sides
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New materials?
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Spacecraft Thermal Design
What about nanotubes?
What about diamonds?
????
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Q =
T4
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Spacecraft Thermal Design
Analysis
Radiation
Q = in watts heat flow /unit time /surface area = emissivity
= Stefan-Boltzman’s constant 5.670 x 10-8 W*m-2K-4
T = temperature in K (273 + T0C)
Q
T
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Radiation Equilibrium
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Effects of Coatings
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Changing S/C temperatures by selection of exterior surface
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Changing S/C temperatures by selection of exterior surface
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Radiation when surface hastransmissivity
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Radiation with surface likesolar cells
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Active & PassiveSystems
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Passive HeatPipes
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Passive HeatPipes
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Read section 11.5 fromSMAD
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Thermal Control Components
• Surface Finishes• Insulation• Louvers• Heat Pipes
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Design Considerations
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
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Remember when doing thermal design for satellites,
always keep your cool!
Introduction to Space Systems and Spacecraft DesignSpace Systems Design
Spacecraft Thermal Design