Radiators

[Kerbface]

Will this game ever include thermal radiators that are needed to prevent ships from overheating?

[Scotius]

RTGs already have radiator fins. When career mode is implemented, it's probable we'll get some sort of nuclear and fusion reactors in mid to late stages of technological progress. Maybe there will be radiators as separate parts, or maybe to cut down part count radiators will be integral parts of reactors. It's hard to tell now.

[Splode]

You don't just need radiators for nuclear reactors, Scotius.

Thermal fins would be really handy for cooling engines in deep space, and could be required for life support systems depending on how far squad takes it.

[Kerbface]

Yeah, I'm not sure but don't all ships need some sort of radiators? Even without any heat generating parts, they'd get a lot of heat from the sun.

[Spatzimaus]

Yeah, I'm not sure but don't all ships need some sort of radiators?

Not "all", but pretty much yes. It's a common misconception that space is cold; if you're in deep space, far from any star, then you'll only be a few degrees above absolute zero. But near a star, your temperature is just based on how much energy each molecule is absorbing, so just because there's very little matter in orbit doesn't mean that it doesn't get really hot.

In theory, any object in orbit around Earth is receiving the same energy density (in watts per square meter) that the surface is, and radiant energy density is proportional to the fourth power of temperature. But, there's one minor effect you have to remember: geometry. A sphere, like Earth, has a cross sectional area of pi*R^2, but a surface area four times that. Effectively, Earth's atmosphere transfers heat around the planet, to keep the dark side from freezing, and even on the part that's being directly lit there'll be areas where the light comes in obliquely and so doesn't warm as much (see: the poles). An object in orbit doesn't have that; it spends most of its orbit in direct sunlight. (Also, if it's small enough, there's really no "dark side", and it's much more likely that there'll be a surface perpendicular to the sunlight.)

So yes, manned craft have radiators to keep the crew from boiling. On the space shuttle, the radiators were on the insides of the cargo bay doors, which is why the doors stayed open while in orbit even if they weren't launching any payloads. Space telescopes don't worry as much about radiators, since most are built with a reflective shield that faces the Sun, and the critical bits are cryogenically cooled to prevent thermal noise from interfering with measurements.

[loppnessmonsta]

The "radial cooling system" or whatever its called (It's under aerodynamic parts) seems to actually work with jet engines. maybe i wasn't paying close enough attention, but it seemed like if i had one in-line with the engine, i could go max throttle and not overheat at all.

if i'm not just imagining it, it's a start.

[azazel1024]

Technically on orbit stuff is getting more energy. IIRC in LEO it is roughly 1KW per M^2. Where as at Earth's surface, high noon at the equator it is around 860W per M^2 due to atmospheric absorbtion.

It would be nice to see radiators at some point to cool parts. Hopefully either radiators will work kind of like monopropellant where it'll cool anything on the ship, so long as it is attached, or else like fuel tanks where you can connect directly to a part you want to cool, or indirectly using coolant hoses (like the fuel connector hoses).

Hopefully we don't get to the level of detail of needing them for life support and every little thing. Needing them to cool things like fission/fusion power plants, NERVA rockets and maybe the mainsail or similar in space would be kind of cool. Much more than that would get a little excessive (and introduce some problems).

[sporkafife]

I think it would be cool if certain parts of the rocket (engines firing, nuclear reactors etc.) generated heat. It could work like a resource but instead of being a good resource, it makes parts overheat and explode/malfunction if they exceeded the amount of heat they can handle and naturally dissipate. And radiator parts can be added to the ship release that heat resource effectively out into the vacuum of space - whereas in atmospheres, the heat drains away naturally due to convection. Maybe even some modders could then use the excess heat resource to generate electricity with some sort of Stirling engine part or something

It would be difficult to do right, and I'm sure there's a better way but I just think it would work nicely with the existing resources

Edited April 22, 2013 by sporkafife
typos, typos, typos!

[Spatzimaus]

Technically on orbit stuff is getting more energy. IIRC in LEO it is roughly 1KW per M^2. Where as at Earth's surface, high noon at the equator it is around 860W per M^2 due to atmospheric absorbtion.

I'd left out the atmospheric absorption part because it's not actually going to make a difference. Less energy hits the surface, true, but the energy absorbed by the atmosphere is still entering the system, and will heat the planet up, so you can't just subtract it. It might take a few intermediate steps of thermal emission and absorption, but about half of that energy will eventually get down to the surface. And a similar amount of thermal emission from the surface, going upward, will likewise be absorbed by the atmosphere and possibly re-radiated back down (sometimes called the "Greenhouse Effect"), so the energy that DOES hit the surface will have a higher impact on temperature than a similar amount of energy would in space. The net result is that the effective energy density at the surface is the same as you'd get in orbit.

But I also left out albedo, although I mentioned it tangentially; if the thing in orbit is reflective (shiny metal or white) then it won't absorb nearly as much energy from the start, and so not need to cool off as much, although things reflective in one wavelength aren't necessarily reflective in others. Like I said before, most space telescopes have a reflective shield they place between themselves and the Sun, to minimize the amount of energy they have to dissipate, and most satellites are left as reflective metal. There's a reason we paint pretty much everything white (including the space suits).

On the other hand, if the object is black (say, the reinforced carbon-carbon tiles on the Space Shuttle or a heat shield) then it'll absorb more energy, and so have more heat to worry about later on. For comparison, Earth's reflectivity is about 30-35% depending on how many clouds there are on a given day, so it's easily possible to have a space vessel that absorbs a larger fraction of the incoming energy than the Earth does.

[azazel1024]

More than anything, it is a YMMV situation. The same satellite placed on Earth's surface is going to have less solar light power density than one in orbit. During the daytime with the sun hitting it, the atmosphere absorbs some of it and even though a lot is re-radiated and will be absorbed by the satellite, it is at a slower rate as it is spread through the day and night time.

So at any given moment, the satellite does receive less solar power than in space, even if over the course of an entire 24 hour period, the amount of radiation received is roughly the same amount. The power levels are lower during the daytime and higher at night.

You also have the issue that in space, you are radiating as a black body. There is no conduction/convection either in surfaces it is touching or in to the surrounding atmosphere. This is the biggest problem. Even ignoring solar input, the active heat of the space craft with all of its systems running is often times enough to cook the ship (Skylab, though that was a solar reflector issue more than anything). Of course, the converse is if running at little to no power, temperatures tend to plummet (Apollo 13), at least if the space craft is designed to shed heat mostly passively.

[sal_vager]

Protip, you can use any radial attached part as a heat sink, try it on SRB's

The only issue is with the Jumbo-64, it's so big that heat cannot reach other parts (it's a bug), but you can fix that by putting something else between the tank and the engine, people use the smaller tanks or cubic struts for this

[Scotius]

I remember someone using a lot of ladder parts as heat sinks on his Moho lander. It was back in 0.17 days, when your craft would overheat and explode on Moho from solar radiation.