About cosmic warmth and cold
On hot summer days, it's time to talk about the heat and cold of space. Thanks to sci-fi films, scientifically and not very scientifically popular programs, many were entrenched with the conviction that space is an unimaginably cold place in which the most important thing is to find how to keep warm. But in fact, everything is much more complicated.
Photos of cosmonaut Pavel Vinogradov
To understand the heat or cold in space, you must first return to the basics of physics. So what is warm? The concept of temperature applies to bodies whose molecules are in constant motion. When receiving additional energy, the molecules begin to move more actively, and with the loss of energy - more slowly.
Three facts follow from this fact:
1) vacuum has no temperature;
2) in vacuum there is only one method of heat transfer - radiation;
3) an object in space, in fact, a group of moving molecules, can be cooled if to ensure contact with a group of slowly moving molecules or to heat, ensuring contact with a rapidly moving group.
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The first principle is used in a thermos where vacuum walls keep the temperature of hot tea and coffee. Likewise, they transport liquefied natural gas in tankers. The second principle defines the so-called external heat exchange conditions, that is, the interaction of the Sun (and / or other radiation sources) and the spacecraft. The third principle is used in the design of the internal structure of spacecraft.
When they talk about the temperature of the cosmos, they can mean two different temperatures: the temperature of the gas scattered in space or the temperature of a body in space. As everyone knows, there is a vacuum in space, but this is not quite so. Almost all the space there, at least inside the galaxies, is filled with gas, it’s just that it is so strongly thinned out that it has almost no thermal effect on the body placed in it.
In a rarefied cosmic gas, molecules are extremely rare, and their effect on macro-bodies, such as satellites or astronauts, is insignificant. Such a gas can be heated to extreme temperatures, but due to the rarity of the molecules, space travelers will not feel it. Those. for most ordinary spacecraft and ships it does not matter what the temperature of the interplanetary and interstellar medium is: at least 3 Kelvin, at least 10,000 degrees Celsius.
Another thing is important: what our cosmic body is, what temperature it is, and what sources of radiation are nearby.
The main source of thermal radiation in our solar system is the sun. And the Earth is quite close to it, therefore, in near-earth orbits, it is very important to adjust the "relationship" of the spacecraft and the Sun.
Most often, man-made objects in space are trying to wrap up in a multi-layered blanket, which does not allow the satellite’s heat to go into space and does not allow the rays of the Sun to fry the delicate insides of the apparatus. The multi-layered blanket is called EVTI - screen-vacuum insulation, “golden foil”, which is not really gold or foil, but a polymer film coated with a special alloy, similar to the one in which flowers are wrapped.
However, in some cases, and in some manufacturers, the ETW is not similar to foil, but performs the same insulating function.
Sometimes, some surfaces of the satellite are specially left open so that they either absorb solar radiation, or take heat into space from the inside. Usually, in the first case, the surfaces are covered with black enamel, which strongly absorbs the radiation of the Sun, and in the second case - with white enamel, which reflects the rays well.
There are cases when on board the spacecraft devices must operate at a very low temperature. For example, the Millimetron Observatory and the JWST will observe the thermal radiation of the Universe and for this, both the mirrors of their onboard telescopes and radiation receivers need to be very cold. At JWST, the main mirror is planned to be cooled to - 173 degrees Celsius, and on the "Millimetron" - even lower, to - 269 degrees Celsius. In order for the Sun not to heat the cosmic observatories, they are covered by the so-called radiation screen: a kind of multi-layered solar umbrella, similar to EVTI.
By the way, just for such “cold” satellites a small heating from rarefied cosmic gas and even from relict radiation filling the entire Universe of photons becomes important. This is partly because the Millimetron, that JWST is sent away from the warm Earth to Lagrange, for 1.5 million km. In addition to solar umbrellas on these scientific satellites there will be a complex system with radiators and multi-stage refrigerators.
On other, less complex devices, heat is also discharged in space through radiation from radiators. Usually they are just covered with white enamel and try to place either parallel to the sunlight, or in the shade. On the meteorological satellite " Electro-L " it was required to cool the matrix of the infrared scanner to -60 degrees Celsius. This was achieved with the help of a radiator, which was constantly kept in the shade, and every six months the satellite was turned 180 degrees so that the inclination of the earth’s axis did not cause the radiator to fall under the sun’s rays. In the days of the equinoxes, the satellite had to be kept slightly at an angle, causing artifacts at the poles of the Earth to appear in the photographs.
Overheating is one of the obstacles in creating a spacecraft with a powerful nuclear power source. Electricity on board is derived from heat with an efficiency much less than 100%, so the excess heat has to be dumped into space. The traditional radiators used now would be too big and heavy, so now in our country work is underway to create drip-emitter refrigerators in which the coolant in the form of droplets flies through outer space and gives it warmth by studying.
The main source of radiation in the solar system is the Sun, but the planets, their satellites, comets and asteroids make a significant contribution to the thermal state of the spacecraft that flies around them. All these celestial bodies have their own temperature and are sources of thermal radiation, which, moreover, interacts with the outer surfaces of the apparatus in a different way than the more “hot” radiation of the Sun. But the planets also reflect solar radiation, and planets with dense atmospheres reflect diffusely, atmosphereless celestial bodies - according to a special law, and planets with a rarefied atmosphere like Mars - still completely different.
When creating spacecraft, it is necessary to take into account not only the "relationship" of the device and space, but also all the instruments and devices inside, as well as the orientation of the satellites with respect to radiation sources. In order for some not to heat others, and others not to freeze, and to maintain the working temperature on board, a separate service system is being developed. It is called the “Thermal Management System” or the SOTR. It may include heaters and refrigerators, radiators and heat ducts, temperature sensors, and even special computers. Can be used active systems or passive, when the role of heaters perform working devices, and the radiator - the apparatus body. It is such a simple and reliable system created for the private Russian satellite "Dauria Aerospace".
More complex active systems involve circulating coolant or heat pipes, similar to those often used to remove heat from the central processor to the radiator in computers and laptops.
Compliance with the thermal regime, often, is a decisive factor in the efficiency of the device. For example, Lunokhod-2, sensitive to changes in temperature, died because of some ridiculous handful of black regolith on its roof. Solar radiation, which was no longer reflected by thermal insulation, led to overheating of the equipment and failure of the "lunar tractor".
In the creation of spacecraft and spacecraft, the observance of the thermal regime is carried out by individual engineers on COTR. One of them - Alexander Shaenko from "Dauria Aerospace", was engaged in the DX1 satellite, and he helped in the creation of this material. Now Alexander has been engaged in reading lectures on astronautics and creating his own satellite , which will popularize space, becoming the brightest object in the sky after the Sun and the Moon.
Therefore, we in “Dauria” need a new specialist in CRTR. If you have such a friend, let him write to our Skolkovsky office.
Photos of cosmonaut Pavel Vinogradov
To understand the heat or cold in space, you must first return to the basics of physics. So what is warm? The concept of temperature applies to bodies whose molecules are in constant motion. When receiving additional energy, the molecules begin to move more actively, and with the loss of energy - more slowly.
Three facts follow from this fact:
1) vacuum has no temperature;
2) in vacuum there is only one method of heat transfer - radiation;
3) an object in space, in fact, a group of moving molecules, can be cooled if to ensure contact with a group of slowly moving molecules or to heat, ensuring contact with a rapidly moving group.
')
The first principle is used in a thermos where vacuum walls keep the temperature of hot tea and coffee. Likewise, they transport liquefied natural gas in tankers. The second principle defines the so-called external heat exchange conditions, that is, the interaction of the Sun (and / or other radiation sources) and the spacecraft. The third principle is used in the design of the internal structure of spacecraft.
When they talk about the temperature of the cosmos, they can mean two different temperatures: the temperature of the gas scattered in space or the temperature of a body in space. As everyone knows, there is a vacuum in space, but this is not quite so. Almost all the space there, at least inside the galaxies, is filled with gas, it’s just that it is so strongly thinned out that it has almost no thermal effect on the body placed in it.
In a rarefied cosmic gas, molecules are extremely rare, and their effect on macro-bodies, such as satellites or astronauts, is insignificant. Such a gas can be heated to extreme temperatures, but due to the rarity of the molecules, space travelers will not feel it. Those. for most ordinary spacecraft and ships it does not matter what the temperature of the interplanetary and interstellar medium is: at least 3 Kelvin, at least 10,000 degrees Celsius.
Another thing is important: what our cosmic body is, what temperature it is, and what sources of radiation are nearby.
The main source of thermal radiation in our solar system is the sun. And the Earth is quite close to it, therefore, in near-earth orbits, it is very important to adjust the "relationship" of the spacecraft and the Sun.
Most often, man-made objects in space are trying to wrap up in a multi-layered blanket, which does not allow the satellite’s heat to go into space and does not allow the rays of the Sun to fry the delicate insides of the apparatus. The multi-layered blanket is called EVTI - screen-vacuum insulation, “golden foil”, which is not really gold or foil, but a polymer film coated with a special alloy, similar to the one in which flowers are wrapped.
However, in some cases, and in some manufacturers, the ETW is not similar to foil, but performs the same insulating function.
Sometimes, some surfaces of the satellite are specially left open so that they either absorb solar radiation, or take heat into space from the inside. Usually, in the first case, the surfaces are covered with black enamel, which strongly absorbs the radiation of the Sun, and in the second case - with white enamel, which reflects the rays well.
There are cases when on board the spacecraft devices must operate at a very low temperature. For example, the Millimetron Observatory and the JWST will observe the thermal radiation of the Universe and for this, both the mirrors of their onboard telescopes and radiation receivers need to be very cold. At JWST, the main mirror is planned to be cooled to - 173 degrees Celsius, and on the "Millimetron" - even lower, to - 269 degrees Celsius. In order for the Sun not to heat the cosmic observatories, they are covered by the so-called radiation screen: a kind of multi-layered solar umbrella, similar to EVTI.
By the way, just for such “cold” satellites a small heating from rarefied cosmic gas and even from relict radiation filling the entire Universe of photons becomes important. This is partly because the Millimetron, that JWST is sent away from the warm Earth to Lagrange, for 1.5 million km. In addition to solar umbrellas on these scientific satellites there will be a complex system with radiators and multi-stage refrigerators.
On other, less complex devices, heat is also discharged in space through radiation from radiators. Usually they are just covered with white enamel and try to place either parallel to the sunlight, or in the shade. On the meteorological satellite " Electro-L " it was required to cool the matrix of the infrared scanner to -60 degrees Celsius. This was achieved with the help of a radiator, which was constantly kept in the shade, and every six months the satellite was turned 180 degrees so that the inclination of the earth’s axis did not cause the radiator to fall under the sun’s rays. In the days of the equinoxes, the satellite had to be kept slightly at an angle, causing artifacts at the poles of the Earth to appear in the photographs.
Overheating is one of the obstacles in creating a spacecraft with a powerful nuclear power source. Electricity on board is derived from heat with an efficiency much less than 100%, so the excess heat has to be dumped into space. The traditional radiators used now would be too big and heavy, so now in our country work is underway to create drip-emitter refrigerators in which the coolant in the form of droplets flies through outer space and gives it warmth by studying.
The main source of radiation in the solar system is the Sun, but the planets, their satellites, comets and asteroids make a significant contribution to the thermal state of the spacecraft that flies around them. All these celestial bodies have their own temperature and are sources of thermal radiation, which, moreover, interacts with the outer surfaces of the apparatus in a different way than the more “hot” radiation of the Sun. But the planets also reflect solar radiation, and planets with dense atmospheres reflect diffusely, atmosphereless celestial bodies - according to a special law, and planets with a rarefied atmosphere like Mars - still completely different.
When creating spacecraft, it is necessary to take into account not only the "relationship" of the device and space, but also all the instruments and devices inside, as well as the orientation of the satellites with respect to radiation sources. In order for some not to heat others, and others not to freeze, and to maintain the working temperature on board, a separate service system is being developed. It is called the “Thermal Management System” or the SOTR. It may include heaters and refrigerators, radiators and heat ducts, temperature sensors, and even special computers. Can be used active systems or passive, when the role of heaters perform working devices, and the radiator - the apparatus body. It is such a simple and reliable system created for the private Russian satellite "Dauria Aerospace".
More complex active systems involve circulating coolant or heat pipes, similar to those often used to remove heat from the central processor to the radiator in computers and laptops.
Compliance with the thermal regime, often, is a decisive factor in the efficiency of the device. For example, Lunokhod-2, sensitive to changes in temperature, died because of some ridiculous handful of black regolith on its roof. Solar radiation, which was no longer reflected by thermal insulation, led to overheating of the equipment and failure of the "lunar tractor".
In the creation of spacecraft and spacecraft, the observance of the thermal regime is carried out by individual engineers on COTR. One of them - Alexander Shaenko from "Dauria Aerospace", was engaged in the DX1 satellite, and he helped in the creation of this material. Now Alexander has been engaged in reading lectures on astronautics and creating his own satellite , which will popularize space, becoming the brightest object in the sky after the Sun and the Moon.
Therefore, we in “Dauria” need a new specialist in CRTR. If you have such a friend, let him write to our Skolkovsky office.
Source: https://habr.com/ru/post/234121/
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