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When will I need radiators?


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In the current version, you only need them if you a) are using nuclear engines, particularly on really long burns and/or when used in large quantities or B) passing really really close to the sun, though I'm not entirely sure how much they;d help in that scenario. Nothing else generates enough waste heat to make much of a difference.

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Radiators are more or less exclusively for use with the nuclear engines during long burns. Radiators aren't really necessary or don't help at all with most other types of heating in the game; most engines don't put out enough heat to make radiators necessary, and they don't help with re-entry heating. I'm not sure if they would be useful for spacecraft in low solar orbits, or for Moho visits (I didn't need them for my Moho mission, though I didn't use the nuclear engines).

Also, regarding radiator usage with the nuclear engines: You should mount the radiators on whatever part the engines are attached to (usually a fuel tank). This will really help dump the heat more effectively and keep all your delicate bits safe and non-melty. You also don't need more than one medium-size deployable radiator per engine, unless you're going to Moho. Usually one small deployable radiator is enough, and for short burns (<800m/s) you really don't need them at all.

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Radiators are more or less exclusively for use with the nuclear engines during long burns. Radiators aren't really necessary or don't help at all with most other types of heating in the game; most engines don't put out enough heat to make radiators necessary, and they don't help with re-entry heating. I'm not sure if they would be useful for spacecraft in low solar orbits, or for Moho visits (I didn't need them for my Moho mission, though I didn't use the nuclear engines).

Also, regarding radiator usage with the nuclear engines: You should mount the radiators on whatever part the engines are attached to (usually a fuel tank). This will really help dump the heat more effectively and keep all your delicate bits safe and non-melty. You also don't need more than one medium-size deployable radiator per engine, unless you're going to Moho. Usually one small deployable radiator is enough, and for short burns (<800m/s) you really don't need them at all.

Thanks for the clarification re: solar visits - I didn't need any in Moho orbit either.

I can verify that on a small-ish single-engine nuclear transfer stage, two small radiators and a couple small radiator plates are just enough cooling for 2000m/s or so single burns (high-speed Jool transfers), though my batteries and science experiments start nearing 50% thermal warnings near the end of the burn.

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Radiators are one of the most weirdest parts in the game. They added plenty of them for almost no reason.

They seem to work the opposite way they should do.

In orbit around Moho you can get a bit hot but the most fragile pieces can resist a temperature of 1200°C and the temperature around Moho is around 500°C, so it's ok.

1444094303-2015-10-06-00007.jpg

I can even get to 1 000 000 000m without exploding :

1444094341-2015-10-06-00008.jpg

But if I dare to add radiators, I can barely stay in Moho orbit :

1444094420-2015-10-06-00010.jpg

My guess is that I add surface to my vessel so it receives more sunlight and thus is getting hotter.

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But the radiators are supposed to face edge on to the sun, so that the ratio of re-radiating area to area exposed to sunlight should be much higher....

I'm almost certain that temperature increase from sunlight is fudged in the game. For instance, building a giant sun shield and hiding your craft behind it doesn't work; you still get warm just as much. That leads me to believe that light exposure does almost nothing, and it's largely just the ambient temperature that's increasing as you approach the sun.

(Mind you, I haven't tested this extensively. There are probably others who can give more reliable info than myself.)

Because radiators are so good at radiating, they are also incredibly good at soaking up ambient heat if they are colder than that (since the game treats absorbing ambient hint simply as some weird sort of 'negative' blackbody radiation). So while a normal craft might stay cool longer, radiators will rapidly ingest heat and pour it into the vessel.

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Then they need to change the radiators, so that the way they angle to the sun is not just a cosmetic effect... but its linked to a behavior where they get treated as if the ambient vacuum temperature is at nearl CBR levels - of course, its more complicated in an atmosphere.. the convection heating should still be there, the heating due to insolation should be strongly reduced.

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Then they need to change the radiators, so that the way they angle to the sun is not just a cosmetic effect... but its linked to a behavior where they get treated as if the ambient vacuum temperature is at nearl CBR levels - of course, its more complicated in an atmosphere.. the convection heating should still be there, the heating due to insolation should be strongly reduced.

I don't know if it's directly tied to light per se, but there is a raycast and the amount of surface area and emissivity of the part does play a role. A radiator flat side on to the sun is going to absorb more heat from the sun than a radiator panel edge on.

To quote Nathankell:

The way 1.0 works, absorption = emissivity, so those solar panels are absorbing solar (heating) flux at quite a high clip. What you need are panels that align perpendicular to that, i.e. with their narrow edges facing the sun; they will take in next to no solar flux and thus radiate out maximally.
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That being the theory, but then why don't sunshields work? Hide a probe core behind a 3.75m heatshield (or other object of similar size), and set SAS to hold radial-in. This should guarantee no solar flux whatsoever. But everything I've read about the topic claims that it will still heat up, and all of the top designs in the Solar Limbo Challenge went completely unshielded.

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That being the theory, but then why don't sunshields work? Hide a probe core behind a 3.75m heatshield (or other object of similar size), and set SAS to hold radial-in. This should guarantee no solar flux whatsoever. But everything I've read about the topic claims that it will still heat up, and all of the top designs in the Solar Limbo Challenge went completely unshielded.

Whatever you use to hide the probe core, that part itself receives a huge flux at that distance (even 2.5m is already huge and you want 3.75m?). You definitely want to minimize exposure before optimizing radiation, because latter is harder, in space.

Unless you unload the vessel until periapsis, load for circularize - but that sounds exploiting.

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That's not what I'm asking though.

I want to know whether or not such a shield prevents parts behind it from receiving heat from the sun. Not through conduction, but from ambient heating. I've been given the understanding that it doesn't. Which makes no sense in the light of NathanKell's quoted statement above.

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