Hot answers tagged

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 ...


34

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 ...


26

The big difference between the two darker RTG fins (Black and Grey) and the white RTG fins, is that the white fins were destined for use in an atmosphere (Mars). The presence of an atmosphere, even as diffuse as Martian air, would allow increased heat transfer from the RTG fins via convection and conduction, vs. the space based versions which would entirely ...


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 ...


23

There is one area of exploration on Earth that approximates conditions on Venus, namely that of deep oil and gas mining, and a few additional areas of technology, near avionics engines, and even auto engines. The stated goal for such electronics is to function at 200 C or higher. The most promising technology for surviving high temperatures is Silicon ...


21

Answer: Thermal radiating coating technology has improved, so they are no longer forced to be sub-optimally black in visible light. They can now be white and reflect incident sunlight to improve thermoelectric efficiency by staying cooler. The color has nothing to do with the atmosphere. It has to do with sunshine! Curiosity's MMRTG is producing about 2 kW ...


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 ...


16

A single number is impossible to give, unless you exactly specify the kind of metal. So I'll answer in the general sense. The first question to answer is "How much energy does the sheet absorb?". This is given by the Inverse-Square Law: $$ I={\frac {P}{A}}={\frac {P}{4\pi r^{2}}}$$ For Mars, this works out to $~ 589\frac W {m^2}$ of energy. 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 ...


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

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 ...


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.


11

There are multiple possible improvements for moving the coolant, in pumping systems. There are piezoelectric pump and electrohydrodynamic pumping systems being worked on, with main advantage being increased reliability. One other candidate would be thermoelectric aka Peltier effect pumps. Similar tech would have ample applications in terrestrial cooling ...


11

We have plenty of metallic materials that could stand the heat of Venus's atmosphere, including copper, nickel, cobalt, iron, titanium, tungsten, and chromium, to name but a few (here's a list of elemental melting points), as well as a large number of alloys including carbon steel and stainless steel. Even the sulfuric acid isn't a huge problem with some of ...


11

When this was captured, it was at the end of the rocket flight. Looking carefully at this, I don't see any other similar nozzles. Furthermore, I didn't see any evidence of this being used in flight. I'm going to assume from all of this that it must be the vent value for the LOX, which was mentioned in the video recording immediately before. What happens ...


11

OK, I found an answer on my own in a caption to the NASA Image of the Day #1740 (11 August, 2010): Into the Light Reflecting on his experience as he emerged from the craft into the daylight on the Expedition 24 mission's second spacewalk, astronaut Doug Wheelock said "the colors of the Earth just explode at you as you exit toward the ...


11

This question is intriguing because of the nature of the thermal cycles. This is the maximum theoretical efficiency of a thermal cycle (Carnot cycle), no ifs, ands, or buts about it. You can obtain very low temperatures from space, because space is at a low temperature. You'll often hear the Cosmic Microwave Background (CMB) cited for this, but that's ...


11

The insulation's job is also to prevent ice from forming on the rocket's skin (and breaking off during ascent). Shards of ice are more dangerous than chunks of foam. Even if ice were no problem, for the Space Shuttle it'd be very difficult to design insulation that comes away cleanly from the tank without hitting the orbiter. For classic rocket designs, ...


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

Why not a satellite-based telescope to observe Mercury in the thermal infrared? Space-borne satellites that are designed to look at the Sun (e.g., SOHO) aren't instrumented to look in the thermal infrared, while satellite-based telescopes that are instrumented to look in the thermal infrared in general don't point anywhere close to the Sun. One issue with ...


10

Orbiting satellites have to deal with darkness all the time when Earth is between the satellite and the sun, and these periods last for much longer than an eclipse does for the satellite. So although I'm no expert, I expect that any satellite designed to function above the dark side of the planet would have no problems with an eclipse.


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 ...


9

Enthalpy released is about 165 kJ / mol of $\require{mhchem}\ce{CO2}$. 2,000 lb of water is about 50 kmol, requiring 25 kmol of $\ce{CO2}$. Thus long-term average heat output is 165 kJ * 25000 / 1 year = 130 watts, which is trivial compared to the overall ISS heat profile. The Sabatier equipment probably runs at a peak-to-average power ratio somewhat ...


9

The sample return capsule is designed to keep its contents below 75 °C. It is a flight-proven design, reusing technology developed for the Stardust mission. The return capsule’s structure consists of a graphite-epoxy material covered with a Thermal Protection System making use of NASA’s PICA heat shield technology – Phenolic-Impregnated Carbon Ablator. PICA ...


9

They tend to be a combination of a highly reflective material, aluminized mylar usually, with a thin mesh in between the layers. The goal is to reflect as much light as possible (specifically those wavelengths emitted by objects at human-body temperature), and keep direct contact between elements to a minimum. Wikipedia has a great picture, shown below.


8

The two systems that I know of that were qualified for skip entry, Apollo and Shuttle, did so purely for cross-range capability. The skip entry would have been used for an emergency return that could not wait for a more favorable alignment with respect to the landing/splashing site. The purpose of qualifying those vehicles for skip entry was not related to ...


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

Is it normal for thrusters to “ice up”? The thing circled in your photo is a LOX vent, not a thruster. The puffy white object is solid oxygen. Your question is directly answered at T+1.05:25 in the Iridium-6/GRACE-FO webcast: Currently you can see the camera on Stage 2, looking at the upper stage engine, that white object you see is solid oxygen, very ...


Only top voted, non community-wiki answers of a minimum length are eligible