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It's been established that cloaking devices such as those used by the Romulans or in the USS Defiant require a great amount of energy to sustain.

But wouldn't the energy have to go somewhere or end up violating at least several laws of thermodynamics. Either the temperature within the cloaked area would have to increase or they would have to dump the energy somewhere?

Note 1: Getting rid of heat is a critical problem on many of our current (21st century) spaceships (ie. satellites). Space isn't cold, just well insulated.

Note 2: If the federation used passive cloaking such as the current class of metamaterials that bend EM radition around themselves, that'd be one thing, but they'd still have to deal with the considerable energy created by the warp core running -- and all those human bodies, life support systems, etc.

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@Sachin Shekhar - unless replicators can violate the second law of thermodynamics, there are limits to the efficiency of any device which attempts to turn heat back into useful work, see bluffton.edu/~bergerd/nsc_111/thermo4.html and bluffton.edu/~bergerd/nsc_111/thermo5.html (especially the bottom of each page) –  Hypnosifl Jul 15 at 3:58
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@Sachin Shekhar -- I did say "unless replicators can violate the second law of thermodynamics". However, if they could violate the 2nd law in Star Trek they could build perpetual motion machines which generate useful energy forever, and wouldn't need to ever refuel their ships. –  Hypnosifl Jul 15 at 4:08
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How is this off topic? Although it is asking for a real world explanation, it does relate directly to a cited work of fiction. –  Xantec Jul 15 at 11:59
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@Sachin Shekhar - and my point is exactly the one I've been making, that unless they can violate the laws of thermodynamics (which they probably can't since starships seem to require fuel and don't have perpetual motion machines, in Voyager they had to have "replicator rations" to avoid using up too much energy for example), converting heat completely back into some useful non-heat form of energy is generally impossible, regardless of what specific technology you use. You can convert some of it back, maybe a higher proportion than any modern technologies, but never 100%. –  Hypnosifl Jul 15 at 13:37
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@Sachin Shekhar - not violating conservation of energy, violating the second law of thermodynamics, because doing that would be a spontaneous decrease in the entropy of the system containing the heat, the meal, and the replicator converting one to the other. And such a thing is exactly what physicists mean when they talk about the impossibility of perpetual motion machines, see the first paragraph of chem.uci.edu/undergraduate/applets/bounce/demon.htm –  Hypnosifl Jul 15 at 14:25
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up vote 12 down vote accepted

The Klingon Bird of Prey Owner's Workshop Manual, which was coauthored by Rick Sternbach (Sternbach and Michael Okuda were the technical consultants on Star Trek: The Next Generation and subsequent shows, and they wrote the Next Generation Technical Manual which is often treated as canonical), describes the Klingon cloak on p. 46:

The cloaking field acts to mask the presence of the Bird-of-Prey through quantum teleportation, by actively transporting matter and energy from outside the envelope to the other side almost entirely unchanged and detectable only with the fastest and most sensitive instruments. Matter and energy produced inside the envelope, from sources like the ship's impulse engines, are temporarily stored within the field. An extremely small fraction of the total energy flux from local space, approximately 0.003 per cent, penetrates the cloak to allow for sub-light navigation.

An EM field produced by the emitter on the ship's exterior performs the actual cloaking by way of a complex spatial phasing of most incoming radiation. This phasing involves the short-range, almost instantaneous, quantum teleportation of radiation and particles through the cloak envelope as well as the ship itself. While the process is not 100 per cent efficient, it works well in the majority of situations a Bird-of-Prey is likely to encounter.

The bolded sentence explains what happens to heat generated from within--it is somehow stored within the field of the cloak itself, which must act as a heat sink while the ship remains cloaked. I would guess the heat can be dumped into space when the ship decloaks.

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Your last sentence is interesting - that means decloaking is not just a quiet sneak around the corner, but a huge bang advertising HERE I AM if the heat is dumped in a rather short timeframe... –  Benedikt Jul 15 at 6:04
    
How would the heat dumped into space? Space is mostly vacuum, so the heat dissipation is very small, or so I have read. –  Flamma Jul 15 at 9:09
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@NateKerkhofs Other than just saying "the ships can move so it must work," we know that the cloak does allow for ionized gas to exit the field, as demonstrated in Star Trek VI. –  Xantec Jul 15 at 12:02
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@Benedikt - couldn't the thermal radiation be aimed in a particular direction, say be enclosing it in a force field which has a single "hole" that allows it to escape into space? Might not be much greater than the radiation given off by firing impulse engines. –  Hypnosifl Jul 15 at 13:40
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@Benedikt Every time someone decloaks, its instant "CAPTAIN! Klingon bird of prey Declocking off the Starboard Bow!" "RED ALERT". It's always alarming, but the entire point of declocking in battle is to attack instantly. So while it's a big advertisement, so is the photon torpedo hitting the ship with it's battle shields down. –  cde Jul 15 at 23:30
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