Reply To: EmDrive + Focus Fusion = Space Access for all?

[HermannH]

Tulse wrote:

Radiating waste heat into deep space isn’t so difficult, on condition you shield your radiator from the sun. After all, space shows us a 3 Kelvin black-body and that’s really cold.

Right, but that is purely radiative cooling, which as I understand it isn’t nearly as efficient as conductive or convective cooling — there’s a reason that thermos bottles use vacuum flasks. As “cold” as space may be, you can cool things far more efficiently on earth by, for example, dumping heat into a lower temperature fluid. (I’m sure that some one with way more technical expertise could clarify what sized radiator would be needed to dump 5MW of heat into space.)

I used this calculator to get the blackbody radiation at 300 degrees Celsius. It is a surprising 6 kW / square meter.

The radiation is highly sensitive to the operating temperature; at 200 degrees Celsius it is less than 3 kW / square meter.