Re: Detection sources

Thomas.Barclay wrote:

>PS - I think I have to question Oerjan on his comments on the
>radioation of heat/IR. Though I agree with the physics he is
suggesting >(that energy is a wave-particle duality and one can emit
without having >air to conduct the heat), I can only conclude this
emission is very >inefficient because the Space Shuttle engineers had
to put quite a bit of >thought into how to dispose of waste heat.

Conduction and convection are much more efficient mechanisms for
transporting heat than radiation is, certainly. However, radiation is
what's most readily available to spaceships :-/

>So obviously the radiation of IR/heat energy isn't sufficient without
such >additional methods - at least as it pertains to keeping the
shuttle a nice, >habitable vehicle.

The problem here is that the shuttle is out in space for a week at a
time or so. FT warships tend to stay out for much longer periods - how
much "bunker mass" would they need just to stay cool? How have the
various space stations handled the excess heat problem? 

>Now, whether this means the radiation is insufficient for detection
>(since something IS radiated despite the vacuum outside) remains a
>topic for debate. 

Any IR sensor (sight, goggles, binoculars, whatever) detect IR
radiation, rather than convection or conduction. (OK, they can see heat
being convected away from a warm body - but they see the IR radiation
being radiated from the warm air or fluid doing the convection... and
as for heat *conduction*, well - if the sensor has to physically touch
its target in order to detect it, it probably isn't that much use in
deep space <g>)

Regards,

Oerjan Ohlson
oerjan.ohlson@telia.com

"Life is like a sewer.
  What you get out of it, depends on what you put into it."
- Hen3ry