There seems to be some misinformation over at the Project Rho site:
http://www.projectrho.com/rocket/rocket3w.html
In particular, this bit:
----begin----
And if you try to focus the emissions into some very narrow cone you
know to be safe, you run into the problem that the radiator area for a
given power is inversely pro****tional to the fraction of the sky
illuminated. With pro****tionate increase in both the heat leakage
through the back surfaces, and the signature to active or semi-active
(reflected sunlight) sensors.
----end----
Now, this doesn't really make any sense. While it is true that a
blackbody (or gray body) has emits energy through a solid angle
directly pro****tional to its output, ie, through a solid angle of one
steradian a blackbody will emit 1/4pi it's output, it is _not_ true
that this is some sort of thermodynamic constraint, at least, so far
as I can tell. I've checked several of my old books, I've checked
online, and this afternoon at lunch I mentioned this to a solid-state
type (admittedly not a thermodynamicist) who said it was definitely
news to him.
So what's the argument for this? Or to put it another way how would
not following the quoted relation****p violate any proposition of
thermodynamics?
I've given a sketchy explanation <a href="http://groups.google.com/
group/rec.arts.sf.written/browse_thread/thread/7f6677c7015a43af/
8b01df62f33eea3e?hl=en&">here:</a>
One poster has avowed that this somehow goes against the 2nd Law, but
wasn't terribly specific how.
So what are the arguments for and against? And is the original quote
something that was just misunderstood by the author?
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