In spacecraft

Spacecraft

A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

 design, the Thermal Control System (TCS) has the function to keep all the spacecraft parts within acceptable temperature ranges during all mission phases, withstanding the external environment, which can vary in a wide range as the spacecraft is exposed to deep space or to solar or planetary flux, and rejecting to space the internal heat dissipation of the spacecraft itself.

The thermal control is essential to guarantee the optimum performance and success of the mission, because if a component encounters a temperature which is too high or to low, it could be damaged or its performance could be severely affected. Thermal control is also necessary to keep specific components (such as optical sensors, atomic clocks, etc.) within a specified temperature stability requirement, to ensure that they perform as efficiently as possible.

The thermal control subsystem can be composed both of passive and of active items and works in two ways:

• protects the equipment from too hot temperatures, either by thermal insulation from external heat fluxes (such as the Sun or the planetary infrared and albedo flux), or by proper heat removal from internal sources (such as the heat dissipated by the internal electronic equipment).
• protects the equipment from too cold temperatures, by thermal insulation from external sinks, by enhanced heat absorption from external sources, or by heat release from internal sources.

Passive Thermal Control System (PTCS) items include:

• multi-layer insulation
  Multi-layer insulation
  Multi-layer insulation, or MLI, is thermal insulation composed of multiple layers of thin sheets often used on spacecraft. It one of the main items of the spacecraft thermal design, mainly intended to reduce heat loss by thermal radiation. In its basic form, it does not appreciably insulate...
  
   (MLI), which protects the spacecraft from excessive solar or planetary heating as well as from excessive cooling when exposed to deep space
• coatings that change the thermo-optical properties of external surfaces
• thermal fillers to improve the thermal coupling at selected interfaces (for instance on the thermal path between an electronic unit and its radiator)
• thermal washers to reduce the thermal coupling at selected interfaces
• thermal doublers to spread on the radiator surface the heat dissipated by equipment
• mirrors (secondary surface mirrors, SSM, or optical solar reflectors, OSR) to improve the heat rejection capability of the external radiators and at the same time to reduce the absorption of external solar fluxes
• radioisotope heater unit
  Radioisotope heater unit
  Radioisotope heater units are small devices that provide heat through radioactive decay. They are similar to tiny radioisotope thermoelectric generators , and normally provide about one watt of heat each, derived from the decay of a few grams of plutonium 238, although other radioactive isotopes...
  
  s (RHU), used by some planetary and exploratory missions to produce and store electrical power for TCS purposes

Active Thermal Control System (ATCS) items include:

• thermostatically controlled resistive electric heaters to keep the equipment temperature above its lower limit during the mission cold phases
• fluid loops to transfer the heat dissipated by equipment to the radiators. They can be:
  • single-phase loops, controlled by a pump
  • two-phase loops, composed of heat pipe
    Heat pipe
    A heat pipe or heat pin is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces....
    
    s (HP), loop heat pipe
    Loop heat pipe
    A loop heat pipe is a two-phase heat transfer device that uses capillary action to remove heat from a source and passively move it to a condenser or radiator. LHPs are similar to heat pipes but have the advantage of being able to provide reliable operation over long distance and the ability to...
    
    s (LHP) or capillary pumped loops (CPL)
• louver
  Louver
  A louver or louvre , from the French l'ouvert; "the open one") is a window, blind or shutter with horizontal slats that are angled to admit light and air, but to keep out rain, direct sunshine, and noise...
  
  s (which change the heat rejection capability to space as a function of temperature)
• thermoelectric coolers
  Thermoelectric cooling
  Thermoelectric cooling uses the Peltier effect to create a heat flux between the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other side against the...
  
  

Events

The most important event in the field of space thermal control is the International Conference on Environmental Systems

International Conference on Environmental Systems

The International Conference on Environmental Systems, or ICES , is an annual technical conference focusing on human spaceflight technology and space human factors...

, organized every year by AIAA.

See also

• Environmental Control and Life Support System
  Life support system
  In human spaceflight, a life support system is a group of devices that allow a human being to survive in space.US government space agency NASA,and private spaceflight companies...
  
  
• Temperature control
  Temperature control
  Temperature control is a process in which change of temperature of a space is measured or otherwise detected, and the passage of heat energy into or out of the space is adjusted to achieve a desired average temperature....