Dumping heat

[Batman]

Sure it sounds good, but like a few people posted above there are some glaring draw backs to the method used. And since Saxton is a physicist he it seems he would have thought about that. Ohh well at least it sounds better than the techno wank of ST, which is not that good at all.

At least Saxton's methods work. Unlike a lot of those presented by Treknobabble.
By all means come up with a better solution to the problem.

[Batman]

They're not exactly drawbacks per se, it just requires some unusual assumptions to make sense of really.

The neutrino detection thingy most certainly is. Of course, we don't know there's any way around it so Wars likely just decided to live with it.

[Ender]

Sure it sounds good, but like a few people posted above there are some glaring draw backs to the method used. And since Saxton is a physicist he it seems he would have thought about that. Ohh well at least it sounds better than the techno wank of ST, which is not that good at all.

At least Saxton's methods work. Unlike a lot of those presented by Treknobabble.

We don't actually know that yet, I'm still trying to ascertain the efficiency of neutrino generators. It could end up being like the waste heat laser concept, where it creates more waste heat then you get rid of. But given what we see in nature, I'm doubtful that is the case.

By all means come up with a better solution to the problem.

Cap the ships output at a couple of GW and have them pump the coolant through blocks of ice that flashes to steam and is vented out the back?

[Batman]

Let me rephrase this. At least Saxton's methods aren't obviously unworkable at first glance unlike a lot of the Treknobabble ones.
And capping reactor power does NOT solve the problem. It DOES AWAY with the problem in the first place. Slight difference.

[Connor MacLeod]

The neutrino detection thingy most certainly is. Of course, we don't know there's any way around it so Wars likely just decided to live with it.

Depends on how snesitive the neutrino detectors are. And it may not work as well if they angle the radiation away in a single direction.

[Batman]

Depends on how sensitive the neutrino detectors are.

With that kind of intensity real-world neutrino detectors likely have a good chance of picking them up. Somehow I don't think Wars ones are going to do worse.

And it may not work as well if they angle the radiation away in a single direction.

Which brings back the momentum problem mentioned earlier.

[Ender]

Depends on how sensitive the neutrino detectors are.

With that kind of intensity real-world neutrino detectors likely have a good chance of picking them up. Somehow I don't think Wars ones are going to do worse.

And it may not work as well if they angle the radiation away in a single direction.

Which brings back the momentum problem mentioned earlier.

"single direction" for neutrino generators really just means "single axis".

Collaminate the beams, put them through some void spaces you shield and route passageways around, or stick the radiators out on where no one deals with them (EG Acclamator) and you are good.

[Adrian Laguna]

And it may not work as well if they angle the radiation away in a single direction.

Which brings back the momentum problem mentioned earlier.

They could just angle it in the direction opposite to their current acceleration vector.

[Ender]

And it may not work as well if they angle the radiation away in a single direction.

Which brings back the momentum problem mentioned earlier.

They could just angle it in the direction opposite to their current acceleration vector.

Not a good plan, you then either need to pipe the coolant system throught he bulk of the ship to the nose (creating significant design and cooling issues), or shoot it through the on axis of the ship rendering the largest volume of space unavailabe out of all your mounting options. Further, depending on the amount of waste heat you are dumpiong it could affect your acceleration. On top of that, the most energy to dump will come in battle from the shields, and the ships are notable not accelerating at that time.

[Adrian Laguna]

Not a good plan, you then either need to pipe the coolant system throught he bulk of the ship to the nose (creating significant design and cooling issues), or shoot it through the on axis of the ship rendering the largest volume of space unavailabe out of all your mounting options. Further, depending on the amount of waste heat you are dumpiong it could affect your acceleration. On top of that, the most energy to dump will come in battle from the shields, and the ships are notable not accelerating at that time.

I see how it won't work. However, piping the coolant system to the nose wasn't necessary under my plan. They could have just had the system dump neutrinos only toward the rear, dorsal, ventral, and lateral sides. That's something of a moot point though, seeing as the system seems to be a bad idea overall.

[NoXion]

Aren't neutrinos incredibly non-interacting?

[Batman]

Aren't neutrinos incredibly non-interacting?

They are. But since Wars ships would be emitting them in quantities exceeding those detectable by real-world means they should be detectable by Wars means.
Hence people looking for a way to dump them somewhere nobody's looking.
And no, 'subspace' is not an option.

[Darth Wong]

Why is detection a problem? Is anyone here under the belief that an ISD must always run its reactor at maximum power even when it's running silent and trying to avoid detection? The neutrino output could be very low when the ship is coasting and attempting to avoid detection, and when it's unloading with its main weapons and accelerating at full power, its neutrino output would spike but detection would be a non-issue under those circumstances. It's not as if anyone could possibly miss a Star Destroyer firing all its weapons and accelerating at full throttle.

[Ender]

Why is detection a problem? Is anyone here under the belief that an ISD must always run its reactor at maximum power even when it's running silent and trying to avoid detection? The neutrino output could be very low when the ship is coasting and attempting to avoid detection, and when it's unloading with its main weapons and accelerating at full power, its neutrino output would spike but detection would be a non-issue under those circumstances. It's not as if anyone could possibly miss a Star Destroyer firing all its weapons and accelerating at full throttle.

Except that thanks to jamming, they do. Jamming is a very important part of battles for that reason. Except you can't jam passive sensors, which neutrino sensors would be. If you try, you just make yourself more detectable. Given the drawbacks of active sensors and the fact you can fight entirley by pasive ones, if neutrino detection was used as a sensor they would be highly prized and jamming far less useful. This is not the case, so we must explain why.

[Agemegos]

It's not as if anyone could possibly miss a Star Destroyer firing all its weapons and accelerating at full throttle.

Except that thanks to jamming, they do. Jamming is a very important part of battles for that reason.

Jamming is an important part of battles because it prevents the enemy from locating and ranging you. Jamming doesn't prevent them from detecting you (ie. telling that you are in the area). Jamming is like screaming so loud that a bat reliant on echolocation can't hear its echos for the din. The bat will certainly know that you are there.

Except you can't jam passive sensors, which neutrino sensors would be. If you try, you just make yourself more detectable. Given the drawbacks of active sensors and the fact you can fight entirley by pasive ones, if neutrino detection was used as a sensor they would be highly prized and jamming far less useful. This is not the case, so we must explain why.

An ISD firing all its weapons and accelerating at full throttle would stand out like a sore thumb to passive visual sensors, passive IR sensors, and just about any other passive EM sensor. You could eyeball the thing from across a solar system. E25 watts is s respectable fraction of the power output of a Sun-like star, and some of that energy will degrade to heat in processes outside the hull.

We are inclined to think that warfare in space might be rather like submarine warfare: dominated by sneaking and lurking in fragile vessels with devastating weapons, with a strong chance that the combatant who first detects the other will get in a decisive first hit. This is because because we on Earth find it rather hard to detect asteroids in space, and a spaceship might well be about the same size as a small asteroid, or even smaller. So we expect that spaceship will find it difficult to detect one another.

A closer consideration of the situation of spaceships and the sensitivity and resolving power of telescopes in space suggests a very different situation. Within a range of a billion kilometres or so any sort of spaceship drive is likely to be astronomically spectacular, and spaceships can't even change course without lighting a drive. And then any crewed spaceship has to be a lot warmer than any asteroid and a lot cooler than any star--in fact, about the temperature of Earth's atmosphere (which is why we can't do any astronomy using those wavelengths from the ground). Which means that the wavelength (ie. colour) of its thermal emissions will stand out. Whole-sky scanning for a spaceship 'running silent' might be slow, but unless it lights its drive you get plenty of time. And if it does light its drive it ought to be dead easy to locate.

Actual stealth is not likely to be a workable strategy for warships in space, except in the highly unusual circumstances in which there is something to hide behind. Battle in general will be dominated by 'speed' (acceleration, delta-v) and firepower. So if an ISD's neutrino fulx can be detected, so what? It wasn't trying to hide anyway. Except, perhaps, in ambush near a bunch of rocks, in which case it can probably power down the generators.

[Ender]

It's not as if anyone could possibly miss a Star Destroyer firing all its weapons and accelerating at full throttle.

Except that thanks to jamming, they do. Jamming is a very important part of battles for that reason.

Jamming is an important part of battles because it prevents the enemy from locating and ranging you. Jamming doesn't prevent them from detecting you (ie. telling that you are in the area). Jamming is like screaming so loud that a bat reliant on echolocation can't hear its echos for the din. The bat will certainly know that you are there.

Passive sensors can locate and range as well. See tanks and subs.

Except you can't jam passive sensors, which neutrino sensors would be. If you try, you just make yourself more detectable. Given the drawbacks of active sensors and the fact you can fight entirley by pasive ones, if neutrino detection was used as a sensor they would be highly prized and jamming far less useful. This is not the case, so we must explain why.

An ISD firing all its weapons and accelerating at full throttle would stand out like a sore thumb to passive visual sensors, passive IR sensors, and just about any other passive EM sensor. You could eyeball the thing from across a solar system. E25 watts is s respectable fraction of the power output of a Sun-like star, and some of that energy will degrade to heat in processes outside the hull.

Yes, you should. But thats not how it happens. Therefore a reconciliation must be sought. That shields block infared wavelength light and neutrinos is one way to do this. In that scenario, the sensors would need holes in th shields that would be so large that the danger would offset the advantage. The result would be reliance on FTL, subspace, and radar sensors.

Actual stealth is not likely to be a workable strategy for warships in space, except in the highly unusual circumstances in which there is something to hide behind. Battle in general will be dominated by 'speed' (acceleration, delta-v) and firepower.

Close accelerations (within an OoM) and delta Vs make speed unimpressive, and to have that firepowr you need to give up speed anyhow.

So if an ISD's neutrino fulx can be detected, so what? It wasn't trying to hide anyway. Except, perhaps, in ambush near a bunch of rocks, in which case it can probably power down the generators.

Simple fact is is that if passive sensors wee able to be used, they would be as we would see more things like homing missiles, and the jamming over the DS would not have been an issue. This is not the case. An explanation as to why is needed.

[The Dark]

.....that's a lot of neutrinos. Assuming entirely tau neutrinos of maximum energy, an ISD would give off 3.47E45 neutrinos per second, compared to Sol's 2E38 neutrinos per second, which are split 40/60 among the weak electron neutrinos and the stronger muon and tau neutrinos.

edit: Ah, it's in the ICS. OK, I was wondering where it came from, since I haven't gotten my hands on the AOTC ICS yet.

Where'd you pull tha from?

I was using the 90% efficient reactor I postulated in the OP, which generates the minimum energy needed for an instantaneous jump to hyper. This generator would generate 1E24 watts of waste heat, which means dumping 1E24 joules per second of energy. An electron neutrino is <2.5 eV, a muon neutrino <1.7 MeV, and a tau neutrino <1.8 MeV, so I used 1.8 MeV as the energy level for neutrinos to minimize the number thrown off by an ISD's reactor. Since 1 MeV equals 1.60217653E-13 joules, it's a simple equation (which I screwed up the first time by using milli-eV instead of mega-eV ).

1E24 / 1.60217653E-13 = 6.24150948E36 MeV / second
6.24150948E36 / 1.8 = 3.467505266E36 maximum energy tau neutrinos / second

Note that if any of the neutrinos are the weaker muon or electron neutrinos, the number required jumps higher. This is the minimum number of neutrinos a 90% efficient reactor capable of generating an instantaneous hyper jump would generate.

[Agemegos]

Passive sensors can locate and range as well. See tanks and subs.

In general passive sensors don't range things as well as active. Radar-aimed guns are much more accurate in range than guns aimed by optical range-fingers, as well as working in conditions of reduced [optical] visibility.

An ISD firing all its weapons and accelerating at full throttle would stand out like a sore thumb…. You could eyeball the thing from across a solar system. E25 watts is s respectable fraction of the power output of a Sun-like star, and some of that energy will degrade to heat in processes outside the hull.

Yes, you should. But thats not how it happens. Therefore a reconciliation must be sought. That shields block infared wavelength light and neutrinos is one way to do this.

If the shields block IR and neutrinos, then waste heat will not escape. It will accumulate inside the shields. If it also blocks re-radiation of weapons energy from targets and from teh exhaust plume you have more to worry about than just waste heat.

Actual stealth is not likely to be a workable strategy for warships in space, except in the highly unusual circumstances in which there is something to hide behind. Battle in general will be dominated by 'speed' (acceleration, delta-v) and firepower.

Close accelerations (within an OoM) and delta Vs make speed unimpressive, and to have that firepowr you need to give up speed anyhow.

It is comparative speed and comparative firepower that count. Even if both sides are unimpressive, the 'faster' ship can get away, the ship with more firepower can win the fight. As contrasted with submarines (the context), where any combatants are armed powerfully enough, and battle can in many circumstances go to the side that gets teh drop on the other, regardless of speed and total firepower.

So if an ISD's neutrino fulx can be detected, so what? It wasn't trying to hide anyway. Except, perhaps, in ambush near a bunch of rocks, in which case it can probably power down the generators.

Simple fact is is that if passive sensors wee able to be used, they would be as we would see more things like homing missiles, and the jamming over the DS would not have been an issue. This is not the case. An explanation as to why is needed.

It is. And it has to be an explanation that makes sense.

The explanation that ISDs are stealthy because they convert the waste heat of their generators to neutrinos doesn't cut the mustard. (1) Neutrinos in such quantities would themselves be detectable (2) Drive exhaust and incandescant material in the weapon beams ought to be visible by eyeball for tens or hundreds of millions of kilometres.

Teh explanation that ISDs keep their waste heat, their engine exhaust, and the incandescent wreckage of their targets inside opaque screens doesn't make sense, besides which it is not what we see either.

[Ender]

Passive sensors can locate and range as well. See tanks and subs.

In general passive sensors don't range things as well as active. Radar-aimed guns are much more accurate in range than guns aimed by optical range-fingers, as well as working in conditions of reduced [optical] visibility.

I'd be interested in any numbers of further reading on this you could provide.

Yes, you should. But thats not how it happens. Therefore a reconciliation must be sought. That shields block infared wavelength light and neutrinos is one way to do this.

If the shields block IR and neutrinos, then waste heat will not escape.

You realize shields are one way, right? We see this on the droidekas and the engines, and its stated in the essential guides to weapons and technology. So it won't be restrictive.

It will accumulate inside the shields. If it also blocks re-radiation of weapons energy from targets and from teh exhaust plume you have more to worry about than just waste heat.

Energy shields are one way for certain, and the evidence that particel shields have to be dropped contradictory (states in text they need to be dropped, but we see a torpedo stopped by shields agaisnt the engines at Endor). Thuis this is not a concern. Shields would stop your sensors from reading the incoming emisions (barring what you had sticking out beyond the shields) but not what you throw out.

It is comparative speed and comparative firepower that count. Even if both sides are unimpressive, the 'faster' ship can get away,

Typically warships are extremely close. Note that the Executor and its escorting Imperators both pulled 3,000 Gs above Endor. Like I said, they are all in the same order of magnitude, in fact it appears that there is less then 1,000 Gs difference between the fastest and slowest ships.

As for firepower, like I said, if you are running, you lose you heavy firepower. The heavies throw out as much as the main engines when they go for a full enfilide fires. This is one of the reasons we see so little manuvering going on during fleet battles.

the ship with more firepower can win the fight.

The technicalities of shields make that a bit more complicated. In terms of raw firepower, an Imperator has 3 dreadnaught class star frigates outgunned by close to 30x. Yet the Dreadnaughts take it down.

As contrasted with submarines (the context), where any combatants are armed powerfully enough, and battle can in many circumstances go to the side that gets teh drop on the other, regardless of speed and total firepower.

Except the evidence shows that this is how it goes.

It is. And it has to be an explanation that makes sense.

I must also mesh with the observed evidence, first and foremost. turbolasers don't makes sense - they behabe like the bastardized children of lasers and particle beams. But the explanation provided in the AOTC ICS does match what we observe.

The explanation that ISDs are stealthy because they convert the waste heat of their generators to neutrinos doesn't cut the mustard.

You realize that is the oficial explanation, right?

(1) Neutrinos in such quantities would themselves be detectable

Yes, hence the issue. I suppose its possible they collaminate it into a beam; while it would be nonsteerable, and pair production and CoM means you would have an opposite beam shooting out the other direction (thus limiting where you could mount it) and the neutrino flux could be deadly if you got in the path it could solve this issue somewhat.

(2) Drive exhaust and incandescant material in the weapon beams ought to be visible by eyeball for tens or hundreds of millions of kilometres.

Exhaust you should get scattered gamma flashes from collisions, particularily when it is turning. But you need not get thermal reading from the exhaust plumes. I can have an ice cube moving at .99 C afterall. Temperature is relative, and a low temperature is going to have very little emissions. This also fits with what we see on film; from an Imperator going full bore the thermal glare is only about 13 terawatts. Visible to the lengths you describe, but not on an interstellar scale.

The tracers on the weapons I'm not sure what you are talking about. They are only a few kilowatts in strength, its not a thermal glow there dude; we see they are green and the human eye can't see green hot because of how our eyes are rigged. Same with purple. Anywyas, the essential guides confirm its nonthermal in nature.

Teh explanation that ISDs keep their waste heat, their engine exhaust, and the incandescent wreckage of their targets inside opaque screens doesn't make sense, besides which it is not what we see either.

Why would they mask the targets?

[The Dark]

I'm not sure how low-temperature you could really get an ion engine. Current engines, with a thrust that essentially wouldn't budge an X-Wing, let alone an ISD, have an exhaust temperature of about 300 degrees Celsius. It also would tend to be more visible than a rocket exhaust of similar temperature (not saying there is such a cold rocket, but comparing apples to apples), since the charge on the ions would tend to cause them to repel and scatter more thoroughly than a rocket exhaust. Essentially, the exhaust from ion engines physically cannot be gathered into a collimated beam (neutrinos might be.....I'm dubious we know enough about neutrinos to say one way or the other). The ion engines on a star destroyer would have to be far more energetic to propel its mass, which would tend to involve a higher exhaust velocity (as there are definite limits to how many ions you can cram through an engine at once), which means a stronger charge and thus a more energetic, more detectable exhaust plume.

You realize shields are one way, right? We see this on the droidekas and the engines, and its stated in the essential guides to weapons and technology. So it won't be restrictive.

If it allows the heat/neutrinos out, then it offers no stealth, as you can just detect the heat/neutrinos "popping into being" at the edge of the shield.

[Sriad]

Which brings back the momentum problem mentioned earlier.

They could just angle it in the direction opposite to their current acceleration vector.

Not a good plan, you then either need to pipe the coolant system throught he bulk of the ship to the nose (creating significant design and cooling issues), or shoot it through the on axis of the ship rendering the largest volume of space unavailabe out of all your mounting options. Further, depending on the amount of waste heat you are dumpiong it could affect your acceleration. On top of that, the most energy to dump will come in battle from the shields, and the ships are notable not accelerating at that time.

...so vent neutrinos out the back of the ship IN the direction of thrust? With engines and all, it seems it would be relatively simple.

[OmegaGuy]

There was a thread on this at SB.com

http://forum.spacebattles.com/showthread.php?t=97247

[Darth Wong]

Why is detection a problem? Is anyone here under the belief that an ISD must always run its reactor at maximum power even when it's running silent and trying to avoid detection? The neutrino output could be very low when the ship is coasting and attempting to avoid detection, and when it's unloading with its main weapons and accelerating at full power, its neutrino output would spike but detection would be a non-issue under those circumstances. It's not as if anyone could possibly miss a Star Destroyer firing all its weapons and accelerating at full throttle.

Except that thanks to jamming, they do. Jamming is a very important part of battles for that reason. Except you can't jam passive sensors, which neutrino sensors would be. If you try, you just make yourself more detectable. Given the drawbacks of active sensors and the fact you can fight entirley by pasive ones, if neutrino detection was used as a sensor they would be highly prized and jamming far less useful. This is not the case, so we must explain why.

You're assuming that ISD jammers are intended to accomplish the nigh-impossible task of preventing detection of the ISD itself, rather than making it difficult to detect fighters and missiles launched from that ISD.

[Darth Wong]

There was a thread on this at SB.com

If anyone there made any good points, then raise them here. Otherwise this is of no interest.

[Agemegos]

In general passive sensors don't range things as well as active. Radar-aimed guns are much more accurate in range than guns aimed by optical range-fingers, as well as working in conditions of reduced [optical] visibility.

I'd be interested in any numbers of further reading on this you could provide.

I can't cite anything specific, but I was thinking of the first-salvo accuracy of American radar-aimed battleship guns as compared to Japanese battleship guns aimed by optical rangefinders. The active sensors (radar) gave range as well as bearing by the principle of echosounding, and it seems to my that any active sensor must do the same unless it is emitting-detecting something with infinite speed. Passive sensors can give you range as well as bearing either by triangulation (optical rangefinders) or by calculating from signal-front delay or phase delay at a number of recievers. But the accuracy of that approach is limited by the separation of your detectors.

That shields block infared wavelength light and neutrinos is one way to do this.

If the shields block IR and neutrinos, then waste heat will not escape.

You realize shields are one way, right?

Then they won't keep neutrinos and IR from reaching any detectors.

It will accumulate inside the shields. If it also blocks re-radiation of weapons energy from targets and from teh exhaust plume you have more to worry about than just waste heat.

Energy shields are one way for certain, and the evidence that particel shields have to be dropped contradictory (states in text they need to be dropped, but we see a torpedo stopped by shields agaisnt the engines at Endor). Thuis this is not a concern. Shields would stop your sensors from reading the incoming emisions (barring what you had sticking out beyond the shields) but not what you throw out.

I see, I misunderstood. I though the claim was that the ISD's shield would make it stealth. I wasn't thinking in terms of a shield around the detector blinding it. That seems possible in principle, but the countermeasure is obvious: sensors on pylons or drones outside the shields.

It is comparative speed and comparative firepower that count. Even if both sides are unimpressive, the 'faster' ship can get away,

Typically warships are extremely close. Note that the Executor and its escorting Imperators both pulled 3,000 Gs above Endor. Like I said, they are all in the same order of magnitude, in fact it appears that there is less then 1,000 Gs difference between the fastest and slowest ships.

Well, I was sketching general principles. If all ships' performance is effectively the same, then firepower ought to be all that counts.

But 1,000 gees difference in ships that pull 3,000 gees is a significant performance difference: 33%. You don't have to be orders of magnitude faster than you opponent to choose the terms of engagement.

As for firepower, like I said, if you are running, you lose you heavy firepower.

True, but if you have more legs than the other guy you either get away, or else catch up right close and let him have it. He has to stop running if he wants to shoot back, and if he keeps running you can catch him again. (These simple tactical analyses are, of course, heavily modified when you can force engagement by threatening a stationary asset, or when the faster ship has a safe refuge in range, or somehow runs out of room to flee.

the ship with more firepower can win the fight.

The technicalities of shields make that a bit more complicated.

Granted. Armour did the same with big-gun battleships, too. WWI battlecruisers were essentially battleships without armour, and the theory was that they would be able to 'out-gun what they can't out-run'. What happened in practice was that their battleship guns were overkill against anything except a battleship: the difference between an eight-inch gun and a fourteen-inch gun doesn't make a lot of difference to either a cruiser or a battlecruiser. And when the battlecruisers went in against the heavies (eg. Jutland) it really mattered that each 14"-15" shell hit did a lot more damage to an essentially-unarmoured battlecruiser than it did to a battleship with over a foot of armour plate and the scantlings to back it up.

Anyway, though that is interesting stuff I'm afraid I've led us onto a bit of a tangent. If submarine-like 'lurk and devastate' tactics do work in space it doesn't particularly matter what tactics would be like if they didn't. Let's get back on track.

Except the evidence shows that this is how it goes.

It is. And it has to be an explanation that makes sense.

I must also mesh with the observed evidence, first and foremost.

Indeed. An explanation that doesn't mesh with the observations that it is trying to explain is no explanation at all. But on the other hand, an explanation that doesn't mesh with teh things we are trying to explain observations in terms of isn't an explanation either.

In this instance, invoking neutrinos to explain the (observed) low temperature of ISDs would fail as an explanation if it didn't mesh with what we know about ISDs. But on the other hand, it would also fail if it didn't mesh with what we know about nneutrinos. At very least it would require further explanation.

The same is true of explanations of the drives and weapons that chew up the non-waste part of the power output: the engines, shields, and weapons.

The explanation that ISDs are stealthy because they convert the waste heat of their generators to neutrinos doesn't cut the mustard.

You realize that is the oficial explanation, right?

I realise that it is an official statement of some sort, and that it is offered as an explanation. But it only succeeds as an explanation if it is consistent with what we know of neutrions. If it isn't, for instance if it demands further explanation of why those neutrinos are not as detectable as neutrinos actually are, then it is at least insufficient.

(1) Neutrinos in such quantities would themselves be detectable

Yes, hence the issue.

Good. I see that we are on teh same page, even if I am sometimes a bit over-abstract or even obscure.

I suppose its possible they collaminate it into a beam

No, I don't think it is possible. We'd better ask someone whose physics background is in thermodynamics rather than electromagnetism, but I have a strong suspicion that such a beam would represent a lot of energy at very low entropy. In other words this would violate the Second Law of Thermodynamics.

They might possibly concentrate it into a cone, and point the cone away from know enemy sensors, I suppose. But I thinki thermodynmics requires that this would cost energy, and sets a fairly broad lower limit on the width of the cone.

(2) Drive exhaust and incandescant material in the weapon beams ought to be visible by eyeball for tens or hundreds of millions of kilometres.

Exhaust you should get scattered gamma flashes from collisions, particularily when it is turning. But you need not get thermal reading from the exhaust plumes. I can have an ice cube moving at .99 C afterall.

Only if the process you use to accelerate the icecube is godawful efficent. It takes roughly a 1500 joules of heat to heat a gram of ice from absolute zero to 273K and melt it. But the kinetic energy of a gram of anything at .99c is {1sqrt(1-v^2/c^2)-1}mc^2 = 6.08*0.001*3E8^2 = 5.5E14 J. Your engines have to be 99.9999997% efficient to accelerate an icecube to 0.99c without evaporating it.

Besides which, kinetic energy tends to degrade to heat. I expect that an icecube whipping through the interplanetary medium at 0.99c is going to heat itself by friction, and explode into a puff of incandescent vapour. Lets say that the interplanetary medium consists of five million hydrogen attoms per cubic metre. The cross-sectional area of the icecube will sweep out 3E8 cubic metres per square metre per second, so from the point of view of the icecube the interstellar medium is a beam delivering 1.5E15 hydrogen atoms per square metre per second. At 0.99c those atoms have a kinetic energy of (gamma-1)mc^2. Gamma is 6.08 we calculated before. The mass of a hydrogen atom is about 1.7E-27 kg. c^2 is 9E16. That's 1.4E6 Wm^-2, which is about a thousand times as bright as sunshine. It will evaporate 700 metres of ice a second.

Temperature is relative, and a low temperature is going to have very little emissions.

No, temperature is an absolute. Low temperature exhausts, and low temperature wreckage will have low emissions, but I don't think that either one is plausible without a lot of furtehr explanation.

This also fits with what we see on film; from an Imperator going full bore the thermal glare is only about 13 terawatts. Visible to the lengths you describe, but not on an interstellar scale.

Well, over an interstellar scale the ISD can outrun its own emissions anyway.

The tracers on the weapons I'm not sure what you are talking about. They are only a few kilowatts in strength, its not a thermal glow there dude; we see they are green and the human eye can't see green hot because of how our eyes are rigged. Same with purple. Anywyas, the essential guides confirm its nonthermal in nature.

Actually, I was not thinking som much of the glow of the bolts. I was thinking in terms of incandescent wreckage from the targets.