Thermal management of spacecraft | Wikipedia audio article
In, spacecraft. Design, the, function, of the thermal, control, system. TCS. Is to keep all the spacecraft's. Component. Systems, within, acceptable. Temperature. Ranges, during, all mission, phases. It. Must, cope with 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 with ejecting, to space the internal, heat generated. By the operation. Of the spacecraft. Itself. Thermal. Control, is essential to, guarantee, the optimum, performance and. Success, of the mission because, if a component, is subjected, to temperatures. Which are too high or too low it, could be damaged, or it's 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 overheating 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 emitted by the internal. Electronic. Equipment. Protects. The equipment, from temperatures. That are too cold, 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. Components. Include. Multi-layer. Insulation. 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 it's radiator. Thermal. Washers, to reduce the thermal coupling. At selected. Interfaces. Thermal. Double is 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. Radioisotopes. Heater units, brew, used, by some planetary, and exploratory. Missions, to produce heat for TCS, purposes. Active, thermal control. System. Atcs. Components. Include. Thermostatically-controlled. Resistive. Electric, heaters, to keep the equipment, temperature. Above its lower limit, during the missions, cold phases. Fluid. Loops to transfer, the heat emitted by equipment, to the radiators. They. Can be. Single-phase. Loops, controlled. By a pump. Two-phase. Loops, composed. Of heat pipes HP. Loop, heat pipes. Lhp, or capillary. Pumped, loops corporal. Louvers. Which, change the heat rejection. Capability. To space as a function, of temperature. Thermoelectric. Coolers. Topic. Thermal. Control. Systems. Environment. Interaction. Includes. The interaction. Of the external, surfaces. Of the spacecraft. To the environment. Either. The surfaces. Need to be protected. From the environment or. There has to be improved, interaction. Two. Main goals of environment. Interaction. Are the reduction, or increase of. Absorbed. Environmental. Fluxes. And reduction. Or increase of heat losses to, the environment. Heat. Collection. Includes. The removal of dissipated. Heat from the equipment in, which it is created. To avoid unwanted, increases. In the spacecraft's. Temperature. Heat. Transport. Is taking, the heat from where it is created, to a radiating. Device. Heat, rejection. The heat collected and, transported has. To be rejected, at an appropriate temperature. To, a heat sink, which is usually. The surrounding. Space environment. The. Rejection. Temperature. Depends. On the amount of heat involved, the, temperature. To be controlled, and the temperature. Of the environment into. Which the device radiates. The heat. Heat. Provision. And storage. Is to, maintain, a desired temperature, level. Where heat has to be provided, and, suitable, heat storage, capability. Has to be foreseen. Topic. Environment. For, a spacecraft the. Main environmental. Interactions. Are the energy, coming from the Sun and the heat radiated. To deep space. Other. Parameters. Also influence, the thermal, control, system. Designs, such, as the spacecraft's. Altitude. Orbit. Attitude.
Stabilization. And spacecraft, shape. Different. Types of orbit, such, as low-earth orbit. And geostationary. Orbit, also affect. The design of the thermal, control, system. Low-earth orbit. Leo. This. Orbit, is frequently. Used by, spacecraft. That monitor, will measure the, characteristics. Of the earth and, its surrounding. Environment and. By unmanned, and manned space, laboratories. Such, as EU our ECA, and the international. Space station. The. Orbits, proximity. To the earth has, a great, influence on, the thermal, control system. Needs with the Earth's infrared. Emission, and albedo, playing, a very important. Role as well as the relatively, short orbital. Period, less, than 2 hours and long eclipses, duration. Small. Instruments. Or spacecraft. Appendages. Such as solar panels, that have low thermal inertia, can, be seriously. Affected by this continuously. Changing. Environment. And may require very. Specific, thermal. Design, solutions. Geostationary. Orbit, geo. In this, 24-hour. Orbit. The Earth's influence. Is almost, negligible, except. For the shadowing, during, eclipses. Which, can vary in duration. From zero at solstice to, a maximum. Of one point two hours, at equinoxes. Long. Eclipses. Influence. The design of both the spacecraft's. Insulation. And heating systems. The. Seasonal. Variations. In the direction, and intensity. Of the solar, input have, a great impact, on the design. Complicating. The heat transport, by, the need to convey, most of the dissipated. Heat to the radiator in. Shadow and the heat rejection, systems. Via, the increased, radiator. Area, needed. Almost. All telecommunications. And. Many, meteorological. Satellites. Are in this type of all beds. Highly. Eccentric, orbits. Heo. These, orbits, can have a wide range of, Apogee, and perigee, altitudes. Depending. On the particular mission. Generally. They, are used, for astronomy. Observatories. And the TCS, design, requirements. Depend, on the spacecraft's. Orbital, period, the number and duration, of the eclipses. The relative, attitude. Of earth sun, and spacecraft the. Type of instruments. On board than, their individual. Temperature. Requirements. Deep. Space, and planetary. Exploration. An interplanetary. Trajectory. Exposes. Spacecrafts. To a wide range of, thermal environment. More severe, than those encountered. Around Earth's orbits. Interplanetary. Mission, includes, many, different sub. Scenarios. Depending, on the particular, celestial. Body in. General. The, common, features. Are a long mission, duration. And the need to cope with extreme thermal. Conditions. Such. As cruisers. Either close, to or far, away from the Sun from, 1 to 4 to 5, astronomical. Units, low, orbiting, of very cold or very hot, celestial. Bodies, descends. Through hostile. Atmospheres. And survival. In the extreme, dusty, icy. Environments. On the surfaces. Of the bodies visited. The. Challenge, for the TCS. Is to provide enough, heat rejection. Capability. During the hot operating. Phases, and yet still survive, the cold inactive. Ones. The. Major problem. Is often the provision, of the power required, for that survival. Phase. Topic. Temperature. Requirements. The, temperature. Requirements. Of the instruments. And equipment on, board are the main factors.
In The design of the thermal, control, system. The. Goal of the TCS, is to keep all the instruments. Working within their allowable. Temperature, range, all. Of the electronic. Instruments. Onboard the, spacecraft such. As cameras, data, collection. Devices, batteries. Etc, have. A fixed, operating, temperature. Range. Keeping. These instruments, in, their optimal, operational. Temperature, range, is, crucial, for every mission. Some. Examples. Of temperature. Ranges, include. Batteries. Which, have a very narrow operating. Range typically. Between minus. Five and twenty see. Propulsion. Components. Which have a typical, range of five to forty C for safety, reasons, however, a wider, range, is acceptable. Cameras. Which, have a range of minus, 30 to, 40, see. Solar. Arrays which, have a wide operating. Range of minus. 150. To 100. C. Infrared. Spectrometers. Which, have a range of minus, 40, to 60, see. Topic. Current. Technologies. Topic. Coating. Coatings. Are the simplest, and least expensive. Of, the TCS. Techniques, a. Coating. May be paint or a more sophisticated, chemical. Applied. To the surfaces. Of the spacecraft. To lower or increase, heat transfer. The. Characteristics. Of the type of coating, depends. On their absorptivity. Emissivity. Transparency. And reflectivity. The. Main, disadvantage. Of coating, is that it degrades, quickly due, to the operating. Environment. Topic. Multi-layer. Insulation. MLI. Multi-layer. Insulation. MLI, is the most common, passive, thermal control, element, used on, spacecrafts. MLI. Prevent, both heat losses to, the environment. And excessive. Heating from the environment. Spacecraft. Components. Such as propellant. Tanks. Propellant. Lines, batteries. And solid, rocket motors. Are also covered, in mli blankets. To maintain, ideal operating. Temperature. MLI. Consists, of an outer cover, layer, interior. Layer and an inner cover layer. The. Outer cover. Layer needs, to be opaque to sunlight, generate. A low, amount of particulate. Contaminates. And be able to survive, in the environment, and temperature. To which the spacecraft. Will be exposed. Some. Common, materials. Used for the outer layer, of fiberglass. Woven. Cloth, impregnated. With PTFE. Teflon, PVF. Reinforced. With Nomex, bonded, with polyester, adhesive. And fep. Teflon. The. General, requirement. For the interior, layer is that it needs to have a low immittance. The. Most commonly, used material, for. This layer is Maya that is aluminized. On, one or both sides. The. Interior. Layers are, usually, thin compared, to the outer layer, to save weight and are perforated. To aid in venting, trapped air during, launch. The. Inner cover faces. The spacecraft. Hardware. And is used to protect the thin interior, layers. In urk lovers are often not aluminized. In, order to prevent electrical. Shorts. Some. Materials. Used, for the inner covers, are Dacron, and Nomex, netting. Miler. Is not used because of flammability. Concerns. MLI. Blankets. Are an important. Element of the thermal, control system. Topic. Louvers. Louvers. Are active, thermal control. Elements. That are used in many different forms. Most. Commonly. They are placed over external. Radiators. Louvers. Can also be, used to control heat transfer. Between internal. Spacecraft. Surfaces. Or be placed on openings, on the spacecraft walls. A. Louver. In its fully open, state can reject, six times, as much heat, as it does in its fully closed, state, with, no power required, to operate it. The. Most commonly, used louver. Is the bimetallic, spring. Actuated. Rectangular. Blade louver, also, known as venetian. Blind louver. Louver. Radiator, assemblies. Consist, of five main, elements. Base plate blades. Actuators. Sensing. Elements. And structural. Elements. Topic. Heaters. Heaters. Are used in thermal control. Design, to protect, components. Under cold case, environmental. Conditions. Or to make up for heat that is not dissipated. Heaters. Are used with thermostats. Or solid-state, controllers. To provide exact, temperature. Control, of a particular, component. Another. Common, used for heaters, is to warm up components, to, their minimum, operating, temperatures. Before the components. Are turned on. 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 captain. The. Patch heater, may, contain, either a single, circuit, or multiple. Circuits, depending. On whether or not redundancy. Is required, within, it. Another. Type, of heater the, cartridge, heater is, often, used to heat blocks of material, or high-temperature. Components. Such as propellants. This. Heater, consists. Of a coiled, resistor.
Enclosed, In a cylindrical, metallic. Case. Typically. A hole is drilled in, the component. To be heated, and the cartridge, is potted, into the hole. Cartridge. Heaters, are usually, 1/4, inch or less in diameter, and. Up to a few, inches long. Another, type, of heater used, on spacecraft is. The radioisotope, heater. Units, also known, as Russ. Russ. Are used for, traveling, to outer planets. Past Jupiter due to very low solar, radiance, which, greatly, reduces. The power generated. From solar, panels. These. Heaters, do not require, any electrical. Power from, the spacecraft and. Provide, direct heat, where it is needed at. The. Center, of each crew is a radioactive, material, which. Decays, to provide, Heat. The. Most commonly, used material. Is plutonium. Dioxide a. Single. Rule aise just, 42. Grams and, can fit in a cylindrical, enclosure. 26. Millimeters. In diameter and. 32. Millimeters. Long. Each. Unit. Also generates, one W, of heat at, encapsulation. However, the heat generation, rate, decreases. With time a. Total. Of. 117. Ruffs were used on the Cassini, mission. Topic. Radiators. Excess, waste heat, created, on the spacecraft is. Rejected. To space, by, the use, of radiators. Radiators. Come in several different forms. Such, as spacecraft. Structural. Panels flat. Plate radiators. Mounted, to the side of the spacecraft and, panels, deployed, after, the spacecraft. Is on orbit. Whatever. The, configuration. All radiators. Reject, heat by infrared, IR, radiation. From. Their surfaces. The. Radiating. Power depends. On the surfaces. Immittance and temperature. The, radiator, must, reject, both the spacecraft. Waste heat, and any, radiant. Heat loads from the environment. Most. Radiators. Are therefore given. Surface, finishes. With high IR, immittance, to maximize, heat, rejection, and, low solar, absorptance. To limit heat from the Sun, most. Spacecraft. Radiators. Reject, between, 100. And, 350. W, of internally. Generated. Electronics. Waste heat, per square meter. Radiators. Weight, typically varies, from almost nothing if, an existing, structural. Panel, is used as a radiator, to, around 12, kilograms, per square meter for a heavy deployable. Radiator. And its support, structure. The, radiators. Of the International. Space Station, are clearly visible as, arrays of white square, panels, attached, to the main truss. Topic. Heatpipes. Heatpipes. User, 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. Topic. Future. Of thermal. Control, systems. Composite. Materials. Heat, rejection, through, advanced. Passive, radiators. Spray cooling, devices, eg. Liquid. Droplet, radiator. Lightweight. Thermal, insulation. Variable. Immittance technologies. Diamond, films. Advanced. Thermal control, coatings. Micro. Sheets. Advanced. Spray-on thin, films. Silvered. Quartz, mirrors. Advanced. Metalized polymer-based. Films. Topic. Events. A major. Event, in the field of space thermal.
Control, Is the International. Conference on. Environmental. Systems organized. Every, year by a IAA. Topic. Sunshield. In spacecraft. Design. A sunshield. Restricts. Or reduces. Heat caused by sunlight, hitting a spacecraft. An. Example. Of use of a thermal, shield, is on the infrared, Space, Observatory. The. ISO, Sun shield helped, protect the cryostat, from, sunlight and, it was also covered, with solar, panels not. To be confused, with concept. Of a global scale, Sun shield in geoengineering. Often. Called a space sunshade, or sun, shield, in, that. Case the spacecraft. Itself, is used to block sunlight on, a planet, not, as part the spacecraft's. Thermal, design, an example. Of a Sun shield in spacecraft. Design, is the Sun shield. JWST. On the plan James, Webb Space Telescope. Topic. See, also. Environmental. Control, and life support, system. Space. Sunshade. Temperature. Control. Topic. Bibliography. Gilmore. DG. Satellite. Thermal, control, handbook, the, Aerospace. Corporation, press. 1994. Karam. Rd, satellite. Thermal, control, for, systems, engineer. X' progress. In astronautics. And Aeronautics, aia. A. 1998. Gilmore. DG. Spacecraft. Thermal, control. Handbook 2nd. Ed the Aerospace. Corporation, press. 2002. Temporalis. MN. And W. Pinter, Craner, current. And future techniques. For spacecraft thermal. Control. One, design. Drivers. And current, technologies. The, first of August, 1996. Web. The fifth of September. 2014.
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