question: If the vacuum of space is a thermal insulator, how does the ISS dissipate heat?
comment: Vacuum insulates against *conduction*. It does not insulate against *radiation*; in fact radiant heat travels better through vacuum than through anything else.
passages: In a dependent space suit (such as the ones used in the Gemini program or within lunar orbit on the Apollo program), the heat is carried back to a host spacecraft through an umbilical connection, where it is ultimately radiated or sublimated via the spacecraft's own thermal control system.
   To allow mid-infrared observations within the JWST, the MIRI instrument has an additional cooling system. It works roughly similar to how most refrigerators or an air-conditioner works: a fluid is brought down to a cold temperature in the warm section, and sent back to the cold section where it absorbs heat, then it goes back to the condenser. One source of heat is the left-over heat of the spacecraft, but another is the spacecraft's own electronics, some of which are close to the actual instruments to process data from observations. Most of the electronics are in the much warmer spacecraft bus, but some of the electronics needed to be much closer, and great lengths were taken to reduce the heat they produce. By reducing how much heat the electronics make on the cold side, then less heat needs to be removed.
   The radiators of the International Space Station are clearly visible as arrays of white square panels attached to the main truss.
  
  Section::::Current Technologies.:Heat pipes.
  
  Heat pipes use a closed two-phase liquid-flow cycle with an evaporator and a condenser to transport relatively large quantities of heat from one location to another without electrical power.
  
  Section::::Future of Thermal Control Systems.
  
  BULLET::::- Composite materials
  
  BULLET::::- Heat rejection through Advanced Passive Radiators
  
  BULLET::::- Spray cooling devices (e.g. liquid droplet radiator)
  
  BULLET::::- Lightweight thermal insulation
  
  BULLET::::- Variable-emittance technologies
  
  BULLET::::- Diamond films
  
  BULLET::::- Advanced thermal control coatings
  
  BULLET::::- Microsheets
  
  BULLET::::- Advanced spray on thin films
   The International Space Station (ISS) External Active Thermal Control System (EATCS) maintains an equilibrium when the ISS environment or heat loads exceed the capabilities of the Passive Thermal Control System (PTCS). Note Elements of the PTCS are external surface materials, insulation such as Multi-Layer Insulation (MLI), or Heat Pipes. The EATCS provides heat rejection capabilities for all the U.S. pressurized modules, the Japanese Experiment Module (JEM), the Columbus Orbital Facility (COF), and the main power distribution electronics of the S0, S1 and P1 Trusses. The EATCS consists of two independent Loops (Loop A & Loop B), which both use mechanically pumped fluid state ammonia in closed-loop circuits. The EATCS is capable of rejecting up to 70 kW, and provides a substantial upgrade in heat rejection capacity from the 14 kW capability of the Early External Active Thermal Control System (EEATCS) via the Early Ammonia Servicer (EAS), which was launched on STS-105 and installed onto the P6 Truss.
   Because the space environment is essentially a vacuum, heat cannot be lost through heat convection, and can only be directly dissipated through thermal radiation, a much slower process. Thus, even though the environment of space can be extremely cold, excessive heat build-up is inevitable. Without an LCVG, there would be no means by which to expel this heat, and it would affect not only EVA performance, but the health of the suit occupant as well. The LCVG used with the Apollo/Skylab A7L suit could remove heat at a rate of approximately 586 watts.
   In an independent space suit, the heat is ultimately transferred to a thin sheet of ice (formed by a separate feed water source). Due to the extremely low pressure in space, the heated ice sublimates directly to water vapor, which is then vented away from the suit.
   For ideal black bodies, the brightness temperature is also the directly measurable temperature. For objects in nature, often called Gray Bodies, the actual temperature is only a fraction of the brightness temperature. The fraction of brightness temperature to actual temperature is defined as the emissivity. The relationship between brightness temperature and temperature can be written as:
  
  formula_10
   The station's systems and experiments consume a large amount of electrical power, almost all of which is converted to heat. To keep the internal temperature within workable limits, a passive thermal control system (PTCS) is made of external surface materials, insulation such as MLI, and heat pipes. If the PTCS cannot keep up with the heat load, an External Active Thermal Control System (EATCS) maintains the temperature. The EATCS consists of an internal, non-toxic, water coolant loop used to cool and dehumidify the atmosphere, which transfers collected heat into an external liquid ammonia loop. From the heat exchangers, ammonia is pumped into external radiators that emit heat as infrared radiation, then back to the station. The EATCS provides cooling for all the US pressurised modules, including "Kibō" and "Columbus", as well as the main power distribution electronics of the S0, S1 and P1 trusses. It can reject up to 70 kW. This is much more than the 14 kW of the Early External Active Thermal Control System (EEATCS) via the Early Ammonia Servicer (EAS), which was launched on STS-105 and installed onto the P6 Truss.
   If changes in external temperatures or internal heat generation changes are too rapid for the equilibrium of temperatures in space to take place, then the system never reaches a state of unchanging temperature distribution in time, and the system remains in a transient state.
   Section::::Reception.:Reception upon shutdown.
   The effect is used in satellites and spacecraft to reduce temperature differences caused by direct sunlight on one side of a craft by dissipating the heat over the cold shaded side, where it is dissipated as thermal radiation to space. Since 1961, some unmanned spacecraft (including the Curiosity Mars rover) utilize radioisotope thermoelectric generators (RTGs) that convert thermal energy into electrical energy using the Seebeck effect. The devices can last several decades, as they are fueled by the decay of high-energy radioactive materials.
   A fluid (also called heat transfer fluid) passes through the receiver and becomes very hot. Common fluids are synthetic oil, molten salt and pressurized steam. The fluid containing the heat is transported to a heat engine where about a third of the heat is converted to electricity.
   The next layer is an absorption space. This absorbs most of the light entering the collector. It usually consists of an air gap of around 10 cm thickness with one or more absorption meshes suspended vertically in the space. Often window fly screen mesh is used, or horticultural shade cloth. The mesh itself can hold very little heat and warms up rapidly in light. The heat is absorbed by air passing around and through the mesh, and so the mesh is suspended with an air gap on both the front and back sides.
   VIP2 runs at LNGS, where the background radiation introduced by cosmic rays is strongly reduced. Data are taken in alternating runs without current (background) and in runs with current (signal). By analysing the detected energy spectra in the region where Pauli exclusion principle violating transitions are expected, upper limits on the probability for a violation of the Pauli exclusion principle are obtained.
  
  Section::::Results.
   In a vacuum or in outer space, there is no convective heat transfer, thus in these environments, radiation is the only factor governing heat flow between the heat sink and the environment. For a satellite in space, a 100 °C (373 Kelvin) surface facing the Sun will absorb a lot of radiant heat, because the Sun's surface temperature is nearly 6000 Kelvin, whereas the same surface facing deep-space will radiate a lot of heat, since deep-space has an effective temperature of only a few Kelvin.
  
  Section::::Engineering applications.
  
  Section::::Engineering applications.:Microprocessor cooling.
   The radiative heat exchange depends on the local surface temperature of the enclosure and the properties of the surfaces, but does not depend upon the media. Because media neither absorb, emit, nor scatter radiation.
  
  Governing equation of heat transfer between two surface "A" and "A"
  
  where 
  
  If the surface of the enclosure is approximated as gray and diffuse surface, and so the above equation can be written as after the analytical procedure
  
  where formula_9is the black body emissive power which is given as the function of temperature of the black body
  
  where formula_11is the Stefan–Boltzmann constant.
  
  Section::::Kernel function.
   The NIRSpec instrument operates at -235 °C and is passively cooled by cold space radiators which are mounted on the JWST Integrated Science Instrument Module (ISIM). The radiators are connected to NIRSpec using thermally conductive heat straps. The mirror mounts and the optical bench base plate all manufactured out of silicon carbide ceramic SiC100. The instrument size is approximately and weighs including 100 kg of silicon carbide. The operation of the instrument is performed with three electronic boxes.
  
  NIRSpec includes 4 mechanisms which are:
   BULLET::::- The most common type of heater used on spacecraft is the patch heater which consists of an electrical-resistance element sandwiched between two sheets of flexible electrically insulating material, such as Kapton. The patch heater may contain either a single circuit or multiple circuits, depending on whether or not redundancy is required within it.
   One of the challenges for a Mars habitat is for it to maintain suitable temperatures in the right places in a habitat. Things like electronics and lights generate heat that rises in the air, even as there are extreme temperature fluctuation outside. There can be large temperature swings on Mars, for example at the equator it may reach 70 degrees F (20 degrees C) in the daytime but then go down to minus 100 degrees F (−73 C) at night.
  
  Examples of Mars surface temperatures:
  
  BULLET::::- Average −80 degrees Fahrenheit (−60 degrees Celsius).
   Since the core material of a VIP is similar in thermal characteristics to materials used in conventional insulation, VIPs therefore achieve a much lower thermal conductivity ("k"-value) than conventional insulation, or in other words a higher thermal resistance per unit of thickness. Typically, commercially available VIPs achieve a thermal conductivity of 0.004 W/(m·K) across the centre of the panel, or an overall value of 0.006-0.008 W/(m·K) after allowing for thermal bridging (heat conduction across the panel edges) and the inevitable gradual loss of vacuum over time.
  
  Section::::Comparison to conventional insulation.
   Although robotic spacecraft use thermal radiation almost exclusively, many manned spacecraft have short missions that permit open-cycle evaporative cooling. Examples include the Space Shuttle, the Apollo command and service module (CSM), lunar module and portable life support system. The Apollo CSM and the Space Shuttle also had radiators, and the Shuttle could evaporate ammonia as well as water. The Apollo spacecraft used sublimators, compact and largely passive devices that dump waste heat in water vapor (steam) that is vented to space. When liquid water is exposed to vacuum it boils vigorously, carrying away enough heat to freeze the remainder to ice that covers the sublimator and automatically regulates the feedwater flow depending on the heat load. The water expended is often available in surplus from the fuel cells used by many manned spacecraft to produce electricity.
   Namely, it consists of an open 3He-4He dilution cryostat cooling spiderweb-type bolometers at 100 mK; cold individual optics with horns at different temperature stages (0.1, 1.6, 10 K) and an off-axis Gregorian telescope.
  
  The CMB signal is measured by the 143 and 217 GHz detectors while interstellar dust emission and atmospheric emission are monitored with the 353 (polarized) and 545 GHz detectors.
  
  The whole instrument is bafﬂed so as to avoid stray radiation from the Earth and the balloon.
   Modern CPU heat pipes are typically made of copper and use water as the working fluid.
  
  Section::::Applications.
  
  Section::::Applications.:Spacecraft.
  
  The spacecraft thermal control system has the function to keep all components on the spacecraft within their acceptable temperature range. This is complicated by the following:
  
  BULLET::::- Widely varying external conditions, such as eclipses
  
  BULLET::::- Micro-g environment
  
  BULLET::::- Heat removal from the spacecraft by thermal radiation only
  
  BULLET::::- Limited electrical power available, favoring passive solutions
  
  BULLET::::- Long lifetimes, with no possibility of maintenance
   Regarding heat removal, internal loops have been installed that collect heat generated by crew and equipment. They transport the heat to external loops, which then transfer the heat to surface (radiators) from which it is radiated towards deep space. The active systems are able to work across a range of operating powers because the application parameters can be changed during the operations by a controller. On the other hand, they have complexity that in space is often reflected in a greater involvement of resources (mass and time of the astronaut) and in a higher probability of malfunction.
   Heat is transferred either by conduction or convection. When water is heated, kinetic energy is transferred by conduction to water molecules throughout the medium. These molecules spread their thermal energy by conduction and occupy more space than the cold slow moving molecules above them. The distribution of energy from the rising hot water to the sinking cold water contributes to the convection process. Heat is transferred from the absorber plates of the collector in the fluid by conduction. The collector fluid is circulated through the carrier pipes to the heat transfer vault. Inside the vault, heat is transferred throughout the medium through convection.
  
presuppositions: The vacuum of space insulates against radiation. 
corrections: The vacuum of space insulates against conduction, not radiation.
raw_presuppositions: The vacuum of space insulates against radiation.  The vacuum of space is a thermal insulator.
raw_corrections: The vacuum of space insulates against conduction, not radiation. The vacuum of space does not insulate against radiant heat.