41

All of the displayed radiators depend more on convection than they do on radiation. There is no convection in space. Finned radiators in space tend to have the fins in the same plane rather than parallel planes (the first image) or differing planes (the last two images). The ideal spacecraft radiator has a very small cross section to solar radiation and a ...


39

Fans work by moving cool air (or other fluid) over a warm surface. If there is no air, like in space, a fan will serve no purpose. Cooling things in space is actually a bit tricky because of this - objects on earth tend to lose most of their heat through conduction or convection, but in the vacuum of space, all you can do is radiate heat, which a fan will ...


36

At least for the Space Shuttle, freezing was OK, but thawing out was bad for piping. Hydrazine contracts when it freezes, so it can 'superpack' (more fluid flows in, then freezes, etc.)...then when it thaws out, there is more than can fit in the pipe, and it can burst. In the Space Shuttle's auxiliary power unit, hydrazine plumbing was allowed to sustain ...


30

Soviet planetary probes sometimes had pressurized compartments, so I suspected that they might contain fans. This answer confirms that Venera-8 had a fan. The illustration in the answer has the inner parts mislabeled, though. The fan is really #15 in the drawing. Reading through the source linked in that answer also confirms that Venera-5 had a similar ...


29

Convection isn't a usable heat dissipating function in space, because there is no convecting medium. Radiation, however, works extremely well. Any body in space will radiate in a wide range of wavelengths, and will also absorb radiation. So any part of a space craft or satellite facing the sun will absorb heat (a net gain) and any facing away will radiate ...


29

Salyut 7 had a active cooling system as well. The heat exchangers are the large white panels, perpendicular to the solar panels, to be seen in photographs of the station. This is necessary on all space stations in active mode as the energy produced by solar panels (apparently 4.5 kW in case of Salyut 7, an order of magnitude more in case of the ISS) needs to ...


26

Was the lunar module also used to perform a barbecue roll? Yes, although it took them a while to get there, according to the Apollo Flight Journal. Starting at about 7 and a half hours after the accident, the crew began rotating the spacecraft periodically 90 degrees at a time to approximate the effect of the passive thermal control roll: 063:24:52 Lousma: ...


24

According to Wikipedia launch windows to Venus occur every 19 months. In some cases multiple successful probes were launched with the same design at the same time so I'll group those together (the Soviets launched two similar/identical missions per launch window they actually used to ensure mission success through redundancy). I'll label each mission with ...


24

With typical active radiators on spacecraft, heat is transferred away from the sources into the radiators through forced convection - as heated coolant. At that point the only concern remaining is to remove (radiate) it from the radiators (and as little as possible back into the spacecraft or into other radiators). They are big and they face as much into ...


24

Space in the vicinity of the Sun is not that cold, perhaps even out to Jupiter. One side of the spacecraft will be receiving sunlight while the side shielded from sunlight radiates into empty space. One simple solution to this is to put the vehicle into barbecue mode: The vehicle is made to slowly rotate, thereby preventing one side from getting too hot and ...


20

Multi-fin radiators are worse per unit mass. But for an RTG, it is absolutely vital to provide a very large thermal gradient between the (very small) core and the outer layers. Adding more fins still improves radiation in sum, you just get less radiation per fin. Since the cooling requirement of an RTG is high and absolute, designers have no other choice ...


17

2kW is not that much on Earth You've mentioned radiation and convection in your answer (you forgot conduction). Turns out the properties of Earth's atmosphere make conduction and convection way better than radiation for moving heat around. For an illustration, consider the size of a portable, 2kW, oil-filled radiator: this one lists the size as ...


16

Yes, you would like to conserve the energy, but sadly that is not possible. The problem is: The energy you have is heat. The second law of thermodynamics states that entropy always increases, and that means that while every process in the spacecraft produces heat, going in the opposite way is impossible. You can produce energy from heat if you have a ...


15

To add to Rory's answer, satellites also use heat pipes to transfer heat from the hot side to the cold side; they are highly thermally conductive. Consider a cube-shaped satellite, with one side facing the sun. By using heat pipes or otherwise distributing the heat, the radiative area can be increased to up to 6 times the sun-facing side. Keeping the ...


15

Sputnik-1 was filled with dry nitrogen pressurized to about 1.3 bar and had a fan to control gas temperature between 20° and 30° C. See Wikipedia in german or english. A picture of Sputnik-1 design with the cooling fan can be found here. Korabl-Sputnik 1, an unmanned early prototype of the later manned Vostok spacecraft, had a biological cabin with a ...


15

As referenced in another post in this SE, energy from the sun, for example, will heat up a craft on the side facing the sun, unless mitigated by reflective material. The shadow side of the spacecraft will radiate as heat into empty space. In the case of a flat surface, the energy direction is generally "away." If there is a fin adjacent to the radiating ...


14

The Olympus satellite (1989-053A, 20122) lost pointing and power for long enough that all the fuel froze. It was recovered after a couple months and the fuel defrosted. I couldn't easily find what fuel was used, but it must either be hydrazine or a derivative. The 21-Sep-1991 New Scientist article Nine-week battle that saved Olympus explains: Engineers ...


13

In general satellites are not "painted". They are covered in a variety of Multi-Layer Insulation (MLI) blankets with varying optical qualities. I have seen MLI in silver, black, and gold - sometimes on the same spacecraft. In addition, spacecraft often have radiators (most usually silver) and sometimes even louvers that cover radiators. A spacecraft is ...


13

1) There is no superconducting magnet in AMS-2. This would have required cooling with liquid helium resulting in a limited life time of only 3 years because of helium evaporating. Instead, they used a normal, rare-earth magnet. It has a lower field strength and is heavier, but does not require any power or cooling. The cooling in AMS-2 is only for the ...


12

Most of the time (when it's not maneuvering for experiments and/or visiting vehicles) the ISS maintains a "fixed" attitude in the noninertial Local Vertical, Local Horizontal reference frame. This means that it rotates about the Y body axis (the "port / starboard" axis) at a rate of one revolution per orbit, about 0.067 degrees per second. For easier ...


11

As a first approach, you can assume all electric power will be turned into heat. Some of the power will be used to do something first, but electrical and mechanical resistance will eventually turn all power into heat.


10

I just saw this and recognized my research, ha ha. I realize this is an older question but I wanted to give my two cents. The published article is a bit deceitful in describing the technology (which frustrates me) so I wanted to straighten things out. You are exactly right in that the finite surface area will offset almost any gains from increases in ...


10

You've asked a question that is very difficult to answer accurately without in situ measurements, which apparently we don't have. The short answer: We don't know closer than ~100K! There was an experiment planned for the Mars Surveyor Lander, "MTERC" (Mars Thermal Environment and Radiator Characterization), that would have made those measurements. But that ...


10

The effect of a fan in an electronic device is to accelerate the temperature exchange between circuits and atmosphere. But that temperature exchange works in both directions. When the atmosphere is even hotter than the electronics you expose to it, then improving the flow with a fan will make the part even hotter. That's the principle behind a convection ...


10

I think what other answers have missed or glossed over is solar irradiation. A radiator facing flat edge into the sunlight will be a strong heater, not a radiator. With 1440 watt/m^2 it's about impossible to break even on radiating out through the 'dark' side vs absorbing through the sunlit side if both have similar surface area. So, radiators are made in ...


9

A space station must expel the heat from its electronics. This heat can be considerable, which usually requires large radiators. If the station is dead, then the heat is expelled, without having the heat from the electronics to power it. Also, Salyut 7 was designed to have constant hot water available for the astronauts. The heat from this needed to be ...


8

The RTGs powered the Apollo Lunar Surface Experiments Package. This is also the first thing that comes up when you google "Apollo RTG".


8

There are many ways to control the temperature of a satellite and the distribution of heat within a satellite. Often they are wrapped in multi layer insulation, which gives them their typical golden shine, or other surface treatments like white paint are applied. Other measures include retractable blinds, orienting the satellite in a specific way to the sun, ...


8

There are two considerations I would guess motivate the hydrophobic properties of the thermal protection system: The first is protection against the wear of use to increase the lifetime of the material. Falcon 9 encounters high exposure to water from the sea-journey return but also from the Merlin exhaust during re-entry and landing burns. The exhaust of ...


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