Re: Active vs Passive

On 13-Apr-00 at 13:05, Bell, Brian K (Brian_Bell@dscc.dla.mil) wrote:

> Superconductors conduct two ways. Ambient solar radiation will heat
the
> side of the spacecraft facing the system's star greater than the
> background. You can't duct this with superconductors without the
> superconductors heating and defeating the purpose of using them to
direct
> the heat.

Sure you can.  You refrigerate the outside of the ship, you take the
heat
from the refrigeration process and dump it into your unidirectional 
superconducting wire, which would glow read hot (assuming it didn't
stop superconducting.)

Of course, if you want to be directional you have to trail the wire 
inside a cone such that only radiation directed in the preferred
direction escapes.

It doesn't sound very efficiant to me and I find it hard to believe
something like this would be used, but it could be done.  We do
it now with heat exchangers, its just that the air/ground is a bit
better at siphoning off the waste heat.

Roger