On hot days summer days It's time to talk about the heat and cold of space. Thanks to science fiction films, science and not-so-popular science programs, many have become convinced that space is an unimaginably cold place in which the most important thing is to find how to warm up. But in reality everything is much more complicated.

To understand whether it is warm or cold in space, we must first return to the basics of physics. So what is heat? The concept of temperature applies to the molecules of a substance that are in constant motion. When additional energy is received, the molecules begin to move more actively, and when energy is lost, they move more slowly.

Three conclusions follow from this fact:
1) vacuum has no temperature;
2) in a vacuum there is only one way of heat transfer - radiation;
3) an object in space, actually a group of moving molecules, can be cooled by contact with a group of slowly moving molecules or heated by contact with a quickly moving group.

The first principle is used in a thermos, where vacuum walls hold the temperature of hot tea and coffee. Liquefied natural gas is transported in tankers in the same way. The second principle determines the so-called conditions of external heat exchange, that is, the interaction of the Sun (and/or other sources of radiation) and the spacecraft. The third principle is used in the design of the internal structure of spacecraft.

When they talk about the temperature of space, they can mean two different temperatures: the temperature of gas dispersed in space or the temperature of a body located in space. As everyone knows, there is a vacuum in space, but this is not entirely true. Almost all of the space there, at least inside galaxies, is filled with gas, it’s just so rarefied that it has almost no thermal effect on the body placed in it.

In rarefied cosmic gas, molecules are extremely rare, and their impact on macro bodies, such as satellites or astronauts, is insignificant. Such 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 doesn’t matter at all 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- this 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, they try to wrap man-made objects in space in a multi-layer blanket, which prevents the satellite’s heat from escaping into space and preventing the sun’s rays from frying the delicate insides of the device. The multilayer blanket is called EVTI - screen-vacuum thermal insulation, “gold foil”, which is actually not 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 from some manufacturers, EVTI is not similar to foil, but performs the same insulating function.

Sometimes some surfaces of a satellite are deliberately left open so that they either absorb solar radiation or remove heat from the inside into space. Usually, in the first case, the surfaces are covered with black enamel, which strongly absorbs the radiation of the Sun and poorly emits its own, and in the second - with white enamel, which absorbs poorly and studies well.

There are times when instruments on board a spacecraft must operate at very low temperatures. For example, the Millimetron and JWST observatories will observe the thermal radiation of the Universe, and for this, both the mirrors of their onboard telescopes and the radiation receivers need to be very cold. At JWST, the main mirror is planned to be cooled to - 173 degrees Celsius, and at Millimetron - even lower, to - 269 degrees Celsius. To prevent the Sun from heating up space observatories, they are covered with a so-called radiation screen: a kind of multilayer solar umbrella, similar to EVTI.

By the way, it is precisely for such “cold” satellites that slight heating from rarefied cosmic gas and even from photons of cosmic microwave background radiation that fill the entire Universe becomes important. This is partly why Millimetron, that JWST is sent away from the warm Earth to the Lagrange point, 1.5 million km away. In addition to sun umbrellas, these scientific satellites will have a complex system with radiators and multi-stage refrigerators.

On other, less complex devices, heat loss in space is also carried out through radiation from radiators. Usually they are covered with white enamel and they try to place them either perpendicularly sunlight, or in the shade. On the Elektro-L weather satellite, it was necessary to cool the infrared scanner matrix 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 tilt of the earth's axis did not lead to the radiator being exposed to the sun's rays. On the days of the equinoxes, the satellite had to be held at a slight angle, which is why artifacts appeared in the images near the Earth's poles.

Overheating is one of the obstacles in creating a spacecraft with a powerful nuclear power source. Electricity on board is obtained from heat with an efficiency of much less than 100%, so excess heat has to be dumped into space. Traditional radiators used today would be too large and heavy, so work is now being carried out in our country to create droplet radiator refrigerators, in which coolant in the form of droplets flies through outer space and gives off heat by studying it.

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 near them. All these celestial bodies have their own temperature and are sources of thermal radiation, which, moreover, interacts with the external surfaces of the apparatus differently than the “hotter” radiation of the Sun. But planets also reflect solar radiation, and planets with a dense atmosphere reflect diffusely, atmosphereless celestial bodies - according to a special law, and planets with a rarefied atmosphere like Mars - in a completely different way.

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 relative to the radiation sources. To ensure that some do not heat others, and others do not freeze, and that the operating temperature on board is maintained, a separate service system is being developed. It is called the “Thermal Management System” or SOTS. It may include heaters and refrigerators, radiators and heat pipes, temperature sensors and even special computers. Active or passive systems can be used, when the role of heaters is performed by operating devices, and the radiator is the body of the device. This simple and reliable system was created for the private Russian satellite Dauria Aerospace.

More complex active systems use circulating coolant or heat pipes, similar to those often used to transfer heat from the CPU to the heatsink in computers and laptops.

Compliance with the thermal regime is often a decisive factor in the performance of the device. For example, the Lunokhod 2, sensitive to temperature changes, died due to 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 “moon tractor”.

In the creation of spacecraft and ships, the maintenance of thermal conditions is carried out by individual SOTP engineering specialists. One of them, Alexander Shaenko from Dauria Aerospace, worked on the DX1 satellite, and he helped in the creation of this material. Now Alexander is busy giving lectures on astronautics and creating his own satellite, which will serve to popularize space, becoming the brightest object in the sky after the Sun and Moon.

> How cold is it in space?

What is the temperature in outer space in orbit? Find out how cold it is in outer space, vacuum temperature, absolute zero, value in the shadow.

If we had the opportunity to travel between stars and pass through intergalactic space, we would have to end up in some pretty cold places. So don't forget to pack a few sweaters because it's going to be cold. But how cold is it in space and what is the temperature in space?

Well, unlike your house, car and swimming pool, there is no temperature in a vacuum. So the question raised actually sounds pretty stupid. Only if you yourself find yourself in space can you determine what the temperature is in outer space outside the ship.

There are three methods of heat transfer: conduction, convection and radiation. Heat one side of a metal pipe and the temperature will be transferred to the other (conduction). Circular air is able to transfer heat from one side of the room to the other (convection). But in a vacuum, only the last method works.

The object absorbs photons of energy and heats up. At the same time, photons produce radiation. Heating occurs when an object absorbs more than it emits. Otherwise, it will cool down.

There is a point where you can't get more energy out of an object. This is the minimum possible temperature, equated to absolute zero. But there is one interesting point here - you will never reach this mark.

Let's visit the International Space Station with its temperature in space in orbit. Bare metal heats up to 260°C when exposed to constant sunlight. This is incredibly dangerous for astronauts, who are also forced to go into outer space. Therefore, it is necessary to apply a protective coating. But in the shade the object cools down to -100°C.

Astronauts may experience sudden changes in temperature depending on which side they face the Sun. Of course, this is compensated for by spacesuits with heating and cooling systems.

Let's go even further. The further you move away from , the lower the temperature in space becomes. Pluto's surface temperature reaches -240°C (33 degrees higher absolute zero). The temperature of gas and dust between stars is 10-20 degrees above absolute zero.

If you climb as far as possible, you will get a temperature of 2.7 Kelvin (-270.45°C). This is already the temperature of the relict radiation that permeates the entire Universe. So yes, it's damn cold in space!

Perhaps one of the oldest and most widespread myths about space is this: in the vacuum of space, any person will explode without a special spacesuit. The logic is that since there is no pressure there, we would inflate and burst, like a balloon that was inflated too much. It may surprise you, but people are much more durable than balloons. We don’t burst when we get an injection, and we won’t burst in space either - our bodies are too tough for a vacuum. Let's swell up a little, that's a fact. But our bones, skin and other organs are resilient enough to survive this unless someone actively tears them apart. In fact, some people have already experienced extremely low pressure conditions while working on space missions. In 1966, a man was testing a space suit and suddenly decompressed at 36,500 meters. He lost consciousness, but did not explode. He even survived and fully recovered.

People are freezing

This fallacy is often used. Who among you hasn't seen someone end up outside a spaceship without a suit? It freezes quickly, and if it is not brought back, it turns into an icicle and floats away. In reality, the exact opposite happens. You won't freeze if you go into space; on the contrary, you will overheat. The water above the heat source will heat up, rise, cool, and then again. But there is nothing in space that could accept the heat of water, which means cooling to freezing temperature is impossible. Your body will work to produce heat. True, by the time you become unbearably hot, you will already be dead.

Blood boils

This myth has nothing to do with the idea that your body will overheat if you find yourself in a vacuum. Instead, it is directly related to the fact that any liquid has a direct relationship with environmental pressure. The higher the pressure, the higher the boiling point, and vice versa. Because it is easier for a liquid to change into a gas form. People with logic can guess that in space, where there is no pressure at all, the liquid will boil, and blood is also a liquid. The Armstrong line is where the atmospheric pressure is so low that the liquid will boil at room temperature. The problem is that while liquid will boil in space, blood will not. Other liquids, such as saliva in the mouth, will boil. The man who decompressed at 36,500 meters said that the saliva “cooked” his tongue. This boiling will be more like blow-drying. However, blood, unlike saliva, is in a closed system, and your veins will hold it under pressure in a liquid state. Even if you are in a complete vacuum, the fact that the blood is locked in the system means that it will not turn into gas and escape.

The sun is where space exploration begins. This is a large fireball around which all the planets revolve, which is quite far away, but warms us without burning us. Considering that we could not exist without sunlight and heat, it is surprising that there is a big misconception about the Sun: that it burns. If you've ever burned yourself with fire, congratulations, you've been hit with more fire than the Sun could ever give you. In reality, the Sun is a large ball of gas that emits light and heat energy through the process of nuclear fusion, when two hydrogen atoms form a helium atom. The sun gives light and warmth, but does not give ordinary fire at all. It's just a big, warm light.

Black holes are funnels

There is another common misconception that can be attributed to the depiction of black holes in movies and cartoons. Of course, they are “invisible” in their essence, but for an audience like you and me they are portrayed as looking like ominous whirlpools of fate. They are depicted as two-dimensional funnels with an exit on only one side. In reality, a black hole is a sphere. It doesn't have one side that will suck you in, rather it is like a planet with a giant gravity. If you get too close to it from any direction, that's when you will be swallowed up.

Re-entry

We have all seen how spaceships re-enter the Earth's atmosphere (so-called re-entering). This is a serious test for the ship; As a rule, its surface becomes very hot. Many of us think that this is due to friction between the ship and the atmosphere, and this explanation makes sense: it is as if the ship was surrounded by nothing, and suddenly begins to rub against the atmosphere at a gigantic speed. Of course, everything will heat up. Well, the truth is that friction removes less than a percent of the heat during reentry. The main reason for heating is compression, or contraction. As the ship rushes back toward Earth, the air it passes through compresses and surrounds the ship. This is called a bow shock wave. The air that hits the head of the ship pushes it. The speed of what is happening causes the air to heat up without having time to decompress or cool down. Although some of the heat is absorbed by the heat shield, beautiful pictures re-entry into the atmosphere is created by the air around the device.

Comet tails

Imagine a comet for a second. Most likely, you will imagine a piece of ice rushing through outer space with a tail of light or fire behind it. It may come as a surprise to you that the direction of a comet's tail has nothing to do with the direction in which the comet is moving. The fact is that the comet's tail is not the result of friction or destruction of the body. The solar wind heats the comet and causes the ice to melt, causing ice and sand particles to fly in the opposite direction of the wind. Therefore, the comet's tail will not necessarily trail behind it in a trail, but will always be directed away from the sun.

After Pluto's demotion, Mercury became the smallest planet. It is also the closest planet to the Sun, so it would be natural to assume that it is the hottest planet in our system. In short, Mercury is a damn cold planet. First, at Mercury's hottest point the temperature is 427 degrees Celsius. Even if this temperature remained throughout the entire planet, Mercury would still be colder than Venus (460 degrees). The reason Venus, which is almost 50 million kilometers farther from the Sun than Mercury, is warmer is due to its carbon dioxide atmosphere. Mercury cannot boast of anything.

Another reason has to do with its orbit and rotation. Mercury completes a full revolution around the Sun in 88 Earth days, and a full revolution around its axis in 58 Earth days. Night on the planet lasts 58 days, which gives enough time for the temperature to drop to -173 degrees Celsius.

Probes

Everyone knows that the Curiosity rover is currently engaged in important research work on Mars. But people have forgotten about many of the other probes we've sent out over the years. The Opportunity rover landed on Mars in 2003 with the goal of conducting the mission within 90 days. 10 years later it is still working. Many people think that we have never sent probes to planets other than Mars. Yes, we have sent many satellites into orbit, but landing something on another planet? Between 1970 and 1984, the USSR successfully landed eight probes on the surface of Venus. True, they all burned down, thanks to the unfriendly atmosphere of the planet. The most persistent spaceship survived for about two hours, much longer than expected.

If we go a little further into space, we will reach Jupiter. For rovers, Jupiter is an even more difficult target than Mars or Venus because it is made almost entirely of gas, which cannot be ridden on. But this did not stop scientists and they sent a probe there. In 1989, the Galileo spacecraft set off to study Jupiter and its moons, which it did for the next 14 years. He also dropped a probe on Jupiter, which sent back information about the planet's composition. Although there is another ship on the way to Jupiter, that very first information is invaluable, since at that time the Galileo probe was the only probe that plunged into the atmosphere of Jupiter.

State of weightlessness

This myth seems so obvious that many people refuse to convince themselves otherwise. Satellites, spacecraft, astronauts and others do not experience weightlessness. True weightlessness, or microgravity, does not exist and no one has ever experienced it. Most people are under the impression: how is it possible that astronauts and ships float because they are far from the Earth and do not experience its gravitational attraction. In fact, it is gravity that allows them to float. While flying around the Earth or any other celestial body with significant gravity, the object falls. But because the Earth is constantly moving, these objects do not crash into it.

The Earth's gravity tries to pull the ship onto its surface, but the movement continues, so the object continues to fall. This eternal fall leads to the illusion of weightlessness. The astronauts inside the ship also fall, but they seem to float. The same state can be experienced in a falling elevator or airplane. And you can experience it in a plane free falling at an altitude of 9000 meters.

Despite all the common myths, space is actually neither cold nor hot. Only matter can have these properties, and space is the absence of matter. Science says that heat is a measure of molecular activity. Because there are very few atoms or molecules in space, it is an almost perfect vacuum.

Astronaut Buzz Aldrin (NASA archives)

Only the presence or distance of heat sources determines boiling or freezing temperatures and, accordingly, human sensations - whether it is cold or hot at the moment. This is precisely why the issue of thermoregulation and the habitable capsule of a spacecraft, and especially the spacesuit, is so important. After all, judging by the reports of the astronauts and the film and photographic materials they presented, in spacesuits they spent hours (or even 10-12 hours) in outer space (that is, either under the sizzling Sun or in its icy shadow), and the spacesuit was both their only shelter and almost their home.

And when, in 1969 and in the next three years, American astronauts cheerfully jumped on the lunar surface, everyone, of course, paid attention to the backpacks on their backs. Workers all over the planet looked with undoubted respect at this masterpiece of advanced American technology. After all, this universal backpack provided the astronaut with everything he needed. Since space was “cold”, as everyone believed at the time, the backpack had to provide sufficient heating. And also normal pressure, oxygen supply, removal of excess moisture, etc. Then, however, they remembered that the Moon is hotter than boiling water during the day (the Sun heats its surface to 120°C), and the astronaut rather needs cooling systems. But this aroused even greater respect for American technologists: what wonderful support systems they have created - they save you from the heat and from the cold!

Photo of the Moon (archive wordpress.com)

Briefly, this system and the backpack containing it are called PSZHO - Portable Life Support System (PLSS - Portable Life Support System). A ready-to-use PSJO weighs 38 kg on Earth and just over 6 kg on the Moon, and is 66 cm long, 46 cm wide and 25 cm thick. The total volume of the backpack is therefore 0.66 x 0.46 x 0.25 = 0.076 cubic meters. m. NASA claimed that the PSJO provided the astronaut with complete life support for several hours. There were: an oxygen cylinder, a carbon dioxide neutralizer, a device for removing moisture, a container with water for cooling, another container with waste water for disposal, a heat exchanger, a sensor system for monitoring the vital functions of the body, a powerful walkie-talkie for transmitting a signal to Earth, 4 liters water. And to top it all off, the batteries are big enough to power all the equipment in this backpack.

Wits, however, note the analogy of the system with the blowhole of whales and sperm whales: when they return from the ocean depths to the surface, they must throw out exhaust air and steam with a powerful fountain. And astronauts are also other waste products. That is, they had to walk on the Moon in a halo of either fountains of steam or fine ice crumbs emitted from the spacesuits by sweat, urine and other natural emissions of the body. Okay, let’s say that NASA did not publish these images for ethical reasons.

But how was all this done from a technical point of view? NASA claims that the astronauts wore coveralls that had thin plastic tubes filled with water sewn into them, connected to a water tank: “A more efficient cooling system was used using water-cooled underwear with thin plastic tubes sewn into them.”

Buzz Aldrin (NASA archives)

The hot air in the spacesuits, created by the metabolic processes of the astronaut’s body, was apparently removed using this system into the PSZHO heat exchanger. When the suit began to accumulate excess heat, the astronaut pressed a button, activating the mechanism for releasing waste water from the heat exchanger outlet. “Water erupted from the suit, turned into ice and was sprayed into space,” the astronauts testify.

The only advantage of plastic is its flexibility. Otherwise, plastic is the worst choice for a cooling system because it is a good thermal insulator. The system could only work if there was enough water in the PSJO. How much water is required to complete the task? The surface area of an astronaut is approximately 0.75 square meters. m. Using an emissivity of 0.2, we find the absorbed solar radiation: 1353 W / m² × 0.2 × 0.75 m² = 203 W.

Proponents of NASA's official version claim: "The PSJO was designed to dissipate the metabolic heat generated by the astronaut at a rate of 1,600 British thermal units (BTU) per hour." Since 1 BTU per hour rounded equals 0.293 Watts, we get 469 Watts. This must be added to the thermal radiation of the Sun: 203 + 469 = 672 W.

Now it is necessary to calculate the heat emitted by the shadow side of the suit. But first we will have to make certain assumptions about the temperature of the air and the spacesuit. The higher the temperature, the easier it is for the cooler to work.

Let's assume that the temperature of the spacesuits was +38°C, i.e. +311°K. Now we can apply Stefan Boltzmann's formula. To do this, let's invert the original equation:

Thus, rounding the result, we get radiation of 80 W. Subtract it from 672 and we get 592 watts. To round up, add 8 W for various thermal radiation from walkie-talkies, water pump, etc. Total 600 W. There are 860 calories in one watt. Taking the extreme case (operating at 100% efficiency) into account, it is necessary to produce enough ice to withstand 516,000 cal per hour. In 4 hours, it accumulates 2,064,000 calories.

To reduce the temperature of 1 g of water by 1°C, a loss of 1 calorie of heat is required. To form ice, 1 g of water must lose another 80 calories. Thus, a drop in temperature from +38°C to freezing point (0°C) entails the transfer of 38 calories, plus another 80 calories for freezing - a total of 118 calories for every gram released through the outlet. If you divide 2,064,000 calories by 118, you get 17,491 grams that need to be released. This is 17.5 liters, or 0.0175 cc. m, i.e. almost a quarter of the volume of PSZHO. This amount of water weighs 17.5 kg on Earth, which is 46% of the weight of the backpack!

Let's now look at things realistically. Using an efficiency of 40% (this is a fairly high figure for most mechanisms), we get much more impressive figures, indicating that the PSJO simply could not accommodate even a cooling unit! But the backpack also contains an oxygen cylinder, a carbon dioxide neutralizer, a device for removing moisture, a container with water for cooling, a container with waste water, a heat exchanger, a sensor system, a walkie-talkie, and powerful batteries! Don't you think that only a wizard could design such backpacks?

However, let's continue about cooling. If we divide 17,491 g of water by 240 minutes, it turns out that approximately 70 g of water had to be spewed out of the outlet per minute, escaping from the suit as “frozen steam”. The last expression sounds something like “fried ice,” but NASA experts seem to be accustomed to paradoxes.

However, all this does not matter, since theoretical calculations contradict real facts. According to the officially published cross-sectional diagram of the PSJO, the water container is only 7.6 cm in diameter and 35.5 cm in length. Accordingly, the volume of this container is 1600 cubic meters. cm (1.6 l). This water would only last for 25-30 minutes with an impossible 100% efficiency! But NASA told us about 4 hours! Maybe invented new way water concentration? Of all the achievements of the space age, this would be the most amazing!

Photo detail of Michael Collins' spacesuit (NASA archives)

If we look at things realistically, then our space heroes had to carry a sun umbrella with them. Keeping them out of direct sunlight would have saved them a lot of overheating problems, at least while they were hopping around on the Moon.

But even if they were hiding behind some kind of umbrella while jumping, why weren’t the lunar modules covered with anything? They stood for hours under the scorching sun. Imagine your car sitting in the sun for several hours last summer! You probably won’t be able to forget the feeling of boarding it for a long time, right? But for some reason the astronauts suddenly declare that a freezing cold awaited them in the lunar modules.

Buzz Aldrin wrote that it was so cold in LEM that he had to turn down the air conditioning in his suit. On the other hand, Collins said: “The 2.5 hours allotted to them passed very quickly, after which they climbed back into the lunar module, closed the door and pumped air into the cabin.” This is very strange, since the spacesuit’s air conditioner (if it existed at all!) could not work under normal pressure conditions inside the LEM. He was only able to function in a vacuum! Doubts creep in: did these two astronauts fly to the same Moon?..

August 21, 2014 at 12:30 pm

About cosmic heat and cold

Dauria Aerospace company blog

On hot summer days, it's time to talk about the heat and cold of space. Thanks to science fiction films, science and not so popular science programs, many have become convinced that space is an unimaginably cold place in which the most important thing is to find how to warm up. But in reality everything is much more complicated.

Photo cosmonaut Pavel Vinogradov

To understand whether it is warm or cold in space, we must first return to the basics of physics. So what is heat? The concept of temperature applies to bodies whose molecules are in constant motion. When additional energy is received, the molecules begin to move more actively, and when energy is lost, they move more slowly.

In rarefied cosmic gas, molecules are extremely rare, and their impact on macro bodies, such as satellites or astronauts, is insignificant. Such 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 at all 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.

However, in some cases and from some manufacturers, EVTI is not similar to foil, but performs the same insulating function.

Sometimes some surfaces of a satellite are deliberately left open so that they either absorb solar radiation or remove heat from the inside into space. Usually, in the first case, the surfaces are covered with black enamel, which strongly absorbs solar radiation, and in the second case, with white enamel, which reflects the rays well.

On other, less complex devices, heat loss in space is also carried out through radiation from radiators. Usually they are covered with white enamel and they try to place them either parallel to the sunlight or in the shade. On the weather satellite" Electro-L"It was necessary to cool the infrared scanner matrix to -60 degrees Celsius. This was achieved using a radiator, which was constantly kept in the shade, and every six months the satellite was turned 180 degrees so that the tilt of the earth's axis did not lead to the radiator being exposed to the sun's rays. On the days of the equinoxes the satellite had to be held at a slight angle, which is why artifacts appeared in the images near the Earth's poles.

More complex active systems use circulating coolant or heat pipes, similar to those often used to transfer heat from the CPU to the heatsink in computers and laptops.

Compliance with the thermal regime is often a decisive factor in the performance of the device. For example, the Lunokhod 2, sensitive to temperature changes, died due to some ridiculous handful of black regolith on its roof. Solar radiation, which was no longer reflected by the thermal insulation, led to overheating of the equipment and failure of the “moon tractor”.