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 ...


25

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

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 ...


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 ...


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 ...


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 ...


7

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 ...


5

1) Is simple to answer - to get rid of heat. Aluminium has a reflectivity of about 90% in the range below 1000nm wavelength. At a perihelion of 0.2 AU the total power of the Sun is about 30 kW/m² of which maybe 2 kW/m² are absorbed by the sail. A large emissivity helps in getting rid of that. 2) Massive Chromium has an emissivity of about 0.3 in the IR ...


5

BlackBody Radiation For all intents and purposes, we should consider spacecraft radiators as blackbody radiators. Wikipedia reminds us that blackbody emission is completely independent of the shape of the radiator: Black-body radiation has the unique absolutely stable distribution of radiative intensity that can persist in thermodynamic equilibrium in a ...


5

Following @JCRM's lead: rocket horsepower questions to the rescue! See this answer and this answer for derivations and explanations. Power If we assume that most of the kinetic energy of the air molecules striking the spacecraft is converted to heat (perhaps it's more like half or 2/3) then we can use the concept of "rocket power" which is really ...


5

So this isn't for the main radiators, but the ISS uses intermeshing finplates to transfer heat between the electrical boxes on the P6, P4, S4, and S6 trusses and the corresponding heat rejection systems. Unfortunately, I'm not able to find a picture, but imagine the top picture of your question, but with two of them facing each other, fins interleaved.


5

The original spy satellites used film cameras. They were pressurized with a half atmosphere of nitrogen. What’s really interesting is that they didn’t need to be, according to the manufacturer. This predates the Mercury program, so I get the sense this was tacked on to the earliest space program to prepare for “Man in Space” The interior of the spacecraft ...


5

Note this is not a complete answer, but it is much too long and has too much maths for a comment. The summary is that cooling a phone in space is very unlikely to be a problem (in particular the answers which claim that phones won't work in space for thermal reasons are almost certainly wrong), and conductive cooling (by attaching the phone to the structure ...


5

New Horizon's Integrated Electronics Modules are not pressurized. The spacecraft's thermal control system works by managing radiant and conductive heat transfer, not by convection. The approach taken by New Horizons is to retain heat like a thermos bottle – New Horizons is already in the vacuum of space where no conductive and convective heat will be lost ...


4

Rocket Labs Electron rocket is made of carbon fibre, this gives them the black color you describe. It is not painted black deliberately, in fact they do not paint it at all to save weight. The Falcon 9 is painted white partly to preserve the aluminium structure, partly to increase its albedo. However SpaceX have stated that the thermal effects are so minimal ...


4

The radiator in space has the full meaning of the word "radiator" - it radiates the heat. No other heat exchange is available. In order to radiate the heat efficiently, it has to be black - not ideally black, but black enough around the dominating wavelengths of its temperature. In this regard, fins can help - they can make the surface "blacker" by multiple ...


3

Few seem to have noted that the thermal conductivity of the fins can substantially affect the transfer of hear energy from the source to the radiation point. This is affected by material and thickness. When designing convective heatsinks this can be a major design factor. One point re radiative transfer is that some of the energy gets to other surfaces ...


2

Here's my view - I'd welcome further thoughts on anything I've got wrong. Design practice Choices in thermal design have to pay attention to how well known the material properties are. e.g. better to choose a well known, or stable, parameter rather than one whose nominal properties are just right. I wouldn't be so bold as to state this is the criteria ...


2

I heard an interesting talk in which the professor suggested an array of inverted conical radiative fins for space applications and showed simulations of its comparisons with hollow cylindrical radiative pin fin. They found it to be more effective as once in space drag due to such a design wouldn’t be an issue...so it was mostly only suggested for ...


2

Fins are not really bad for radiative heat transfer. They just face an inevitable point of diminishing returns. Those diminishing returns place a limit on how many fins should practically be included. The optimum is greater than zero but less than a dense packing of fins. Draw a boundary around any isothermal object radiating heat energy into space. The ...


1

In short: the answer is yes to all of the above and the amount of each depends on details. Thermal design of spacecraft usually starts out with assumptions regarding the size, total heat loads, and temperature limits of components. Manned spacecraft have an additional level of complexity due to the requirements needed for comfortable living in cramped ...


1

Radiative heat transfer is effectively by glow: either visible light glow in the case of the sun or an incandescant light bulb, or infrared glow in the case of cooler objects. As such, what matters is how good a view (line-of-sight) that a distant observer has of the surfaces. In your five-finned design you have taken six 1m2 sheets of aluminium and ...


1

Your argument seems to be that you have increased the surface area by a factor of up to 5. Assuming perfect heat conduction within the heatsink, you will radiate 5x more power with that arrangement. But I think you have neglected to consider where that radiation ends up. Let's set up a coordinate system where the original flat radiator is in the XY plane, ...


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