# Mass and efficiency of heat radiators

Probably the only reasonable way how to get rid of waste heat in space is radiating the heat away. Most of the current satellites and probes probably do not produce much waste heat. However, assuming we would like to deploy a spacecraft that produces a lot of waste heat, what are technical parameters of the best radiators we could use?

In particular, I am interested in:

• How heavy the radiator is per square meter, including the cooling liquid?
• What is the temperature of the radiator, if the spacecraft is to be cooled to 300 K?
• You underspecify the problem: how much, exactly, is the sat generating, in W? Nov 26, 2014 at 5:34
• lockheedmartin.com/us/products/HeatRejectionRadiators.html Nov 26, 2014 at 5:37
• I am asking what is our best option, if the heat dissipation is the limit. I am not sure, what is realistic maximum total power to be dissipated. Tens of megawatts? Hundreds? I am trying to imagine limitation by the waste heat disposal if we started to use VASIMR engine with high power input. Nov 26, 2014 at 8:41
• Now if we only had the means to use that heat to propel the craft a La. Pioneer Anomaly Nov 26, 2014 at 12:24

## 1 Answer

You can infer the state of the art from the following quote from Gilmore's 2002 handbook:

Most spacecraft radiators reject between 100 and 350 W of internally generated electronics waste heat per square meter. The upper end of this range is typical of a radiator that runs at a fairly high temperature (say 40°C) and experiences a relatively modest heat backload from the environment or other spacecraft surfaces.

The lower end of the range might represent a radiator running below room temperature in low Earth orbit, where environmental backloads can be substantial. The actual sizing is determined by a thermal analysis that considers the desired operating temperature, worst-case satellite waste heat, environmental heating, and radiative and conductive interactions with other spacecraft surfaces. Weights for radiators typically vary from almost nothing, if an existing structural panel is used as a radiator, to around 12 $$kg/{m^2}$$ for a heavy deployable radiator and its support/deployment structure.

The thing to keep in mind, though is that heat rejection capability goes as the fourth power of the radiator temperature. A VASIMR engine or an NTR nuclear engine have higher operating temps (limited by avionics, of course) than a cryo tank, and you'd generally have many more problems with the latter.