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Radiators
Radiators are used to dissipate any excess heat on a spacecraft. Contrary to popular belief, space is not, in fact, very cold. The temperature of space is very low, but since it is almost completely empty, no noticeable amount of convection (the primary method of heat dispersal on Earth) will occur. In space, the only way to dissipate heat is by radiating it away. Objects will dissipate heat depending on their temperature according to the Stefan-Boltzmann law, which states objects will radiate away heat with respect to their area and the fourth power of their temperature. Accordingly, the best way to get rid of heat in space is to stick out a large, flat radiator and get it as hot as possible while still being tolerable.
In the game, radiators are absolutely essential. They dissipate the waste heat generated by reactors, solar panels, microwave transceivers, and plasma engines. They are also required use any of the generators, as they serve as the cold bath. They radiate away waste heat to prevent your ship from overheating, which can cause components to shut down from the excess heat. A fission reactor will SCRAM if it gets to hot and can only be restarted with an EVA'd Kerbal. Antimatter reactors, fusion reactors, and other components will also shut down, but can be restarted remotely.
Unupgraded, radiators have relatively pitiful heat dissipation, and may not be able to even support an upgraded fission reactor practically. It is very important to research Experimental Electrics as fast as possible as a result.
The effectiveness of radiators is dependent on how full your waste heat bar is. The fuller the bar gets, the hotter the radiators become and the more waste heat they dissipate. It is normal to see your waste heat bar to go up at first. If you have enough radiators, it will eventually stabilize. It is only problematic if your waste heat bar exceeds 95%, which will cause components to shut down. Another thing to note is that the efficiency of generators depends on the ratio of the temperature of your reactors and the temperature of your radiators. The hotter your reactors are and the colder your radiators are, the closer you will get to the theoretical maximum efficiency of the generator. Thus, the more radiators you have, the more efficient your generators will be. This effect is usually not significant unless you have upgraded radiators and non-upgraded fission reactors, in which case it is possible for your efficiency to drop close to zero.
The amount of waste heat your craft generates is based on the energy it produces and the efficiency of the various components. The more energy you create and the less efficient your components are, the more heat you will also create. Reactors produce thermal power, which is consumed by thermal rocket nozzles and generators. Thermal nozzles dump all the heat out of the back along with the propellant, and so any thermal power they consume will not produce waste heat. Generators are not perfectly efficient and so whatever thermal power is consumed and not converted into electricity will become waste heat. For example, if a generator is running at 25% efficiency, 25% of the thermal power will become electricity and the other 75% will become waste heat. Any thermal power that isn't consumed by a generator or thermal nozzle will create an equal amount of waste heat.
Main Article: Waste Heat Management
If you want to be safe, a good rule of thumb is to have enough radiators to dissipate an equal amount of heat that your reactors will produce at 100% power. The level of power reactors produce and radiators radiate can be found in the VAB. In practice, you can usually get away with less radiators, especially if you are using only a thermal rocket nozzle. Fission and fusion reactors run at a minimum of 30% power, so you should always have enough radiators to radiate that much power. Antimatter reactors have no such minimum. Solar panels produce half as much waste heat as they do electric charge (1 EC/s = 1 kW). This amount is usually small enough that any radiator can handle it, unless you have an excessive amount of solar panels or you are very close to the sun.
The collapsible radiator panels are designed to be effective in space, and thus radiate much more heat than the inline or radial radiators. The inline and radial radiators are designed to be more effective at in-atmosphere cooling, and so get a large bonus to convection. They are also usually sufficient to cool small solar-powered craft.
All radiators are less effective in space, so be sure to test your craft in both environments before venturing into deep space or you may find misfortune.
- Mass: 0.005 t
- Maximum Heat Radiated: 0.013 MW / 2.127 MW
- Maximum Temperature: 970 K / 3500 K
- Radiator Area: 0.25 m^2
- Convection Bonus: 20x
- Mass: 0.02 t
- Maximum Heat Radiated: 0.050 MW / 8.509 MW
- Maximum Temperature: 970 K / 3500 K
- Radiator Area: 1 m^2
- Convection Bonus: 20x
- Mass: 5.0 t
- Maximum Heat Radiated: 470.8545 MW / 21272.76 MW
- Maximum Temperature: 1350 K / 3500 K
- Radiator Area: ? m^2
- Convection Bonus: ??x
- Mass: 0.05 t
- Maximum Heat Radiated: 0.063 MW / 10.636 MW
- Maximum Temperature: 970 K / 3500 K
- Radiator Area: 1.25 m^2
- Convection Bonus: 20x
- Mass: 0.2 t
- Maximum Heat Radiated: 0.942 MW / 42.546 MW
- Maximum Temperature: 1350 K / 3500 K
- Radiator Area: 5 m^2
- Convection Bonus: 20x
- Mass: 0.8 t
- Maximum Heat Radiated: 3.767 MW / 170.182 MW
- Maximum Temperature: 1350 K / 3500 K
- Radiator Area: 20 m^2
- Convection Bonus: 20x
- Mass: 0.2 t
- Maximum Heat Radiated: 18.834 MW / 850.91 MW
- Maximum Temperature: 1350 K / 3200 K
- Radiator Area: 100 m^2
- Mass: 0.8 t
- Maximum Heat Radiated: 75.337 MW / 3,403.64 MW
- Maximum Temperature: 1350 K / 3500 K
- Radiator Area: 400 m^2
- Mass: 3.2 t
- Maximum Heat Radiated: 301.347 MW / 13,614.57 MW
- Maximum Temperature: 1350 K / 3200 K
- Radiator Area: 1600 m^2