Originally posted by AviH:
First thanks for the very prompt responses and pointers to sites…
I found Sigs' site very depressing 
...One thing the site does show is that my concept of "Submarine" warfare is wrong – in submarine warfare detection ranges are short and accuracy is low (all relative to air combat) In space if we use the heat signature of power reactors and maneuver drives ranges are high…
Well one thing to remember that despite the formatting and real attmept at accuracy; the site is a copy & paste of information. The sites author is not a physical scientist, has no training or advanced degree in any physical science. Simply reading lots of books and an interest does not give the level of knowledge neccessary to look behind the equations so to speak. So be not depressed!
The determinant is not so much the heat put out, but the "heat" at the observers location. It will basically decrease as the the inverse of the distance squared i.e., viewed as a point source. Actually, you really want to look at power density emitted, it makes it easier to find the siganture at any distance. Temperature is a bit misleading, something can be hotter than the sun but much, much dimmer, since the amount of power output by the sun is simply enormous.
Another disconnect with current tech I don't see mentioned often is the power required for weapons and drives. Usually the requirements are so high that no material exists (this includes cooling systems which rely on materials for heat transfer) that could possibly hold the power plant needed to supply this power. That is, the excess waste heat is so high it would simply melt any material we know of or those even three orders of magnitude better.
As others have mentioned there are so many things about Traveller that are impossible under our current technology and more importantly, understanding of the laws of physics, what's wrong with postulating something that allows for the "sub-hunt" idea.
The one non-realistic piece of physics you may "have" to accept for a playable game is FTL travel. Accepting this may lead to a solution for our heat problem. If a jump drive can send an object into jump space, is it such a leap to think that it might not be able to send energy (heat) into jump space? Unlike an object this heat is far easier to send in, never emerges or emerges on a large sphere somewhere else. In a sense advacened fusion engines use some sort of anomoly field that allows them to shunt waste heat into jump space. (Maybe also a reason why a damper can't just shut your power palnt down). When the "system" from a thermodynamic point of view is viewed as including jump space, no violation of thermodynamics occurs. Having the energy remerge is no problem either as long as it contains no information content.
In addition, viewing jump space as part of the "system" also helps avoid violation of the conservation of energy and momentum.
If you need a couple of real world physics "hooks" that might hint to the existence of jump space to support in game rationales. Maybe normal objects, or past/present jump civilizations, do interact with jump space. Potentially this in and out is part of the explanation of the missing mass of the universe, the so called dark matter, and maybe also a physical basis for vacuum free energy. In addition, if heat energy remerges with a bit of a shift, it might explain the background microwave radiation. (I know we have an explanation for this already but the uniformity wasn't initially expected. Maybe the initial expectation was right and something else explains the microwave background.) Just some ideas.
I personally like a "sub-hunt" potential for game reasons but want hiding to be hard, requiring special engines (or really well tuned engines, or both) that can shunt more heat to jump space etc., operating on low power etc. Making a well tuned engine a quiter engine also puts part of being stealthy in the hands of players and makes engineers all the more valuable.
