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Heat Disposal on ships

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Re: Heat Disposal on ships
Post by ericth   » Fri Apr 14, 2017 2:06 pm

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MaxxQ wrote:Stuff deleted for Brevity
The Rolly Things™ behind the "conning tower" (not really what it is, we just call it that) are the heat sumps that dump the heat into the wedge/Alpha wall.


So THAT's what they are!
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Re: Heat Disposal on ships
Post by Somtaaw   » Fri Apr 14, 2017 2:23 pm

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kzt wrote:
DerHenker wrote:ships in orbit could dissipate the heat into the ionosphere of the planet which they are orbiting. Missiles in ballistic segments won't be in ballistic for too long probably.

Say 2 minutes, with an exawatt fusion reactor running. How hot will a 150 ton missile get when the incredibly efficient reactor radiates a mere gigawatt a second into the missile body? Assume it's all made of iron to make this easier.

It takes 450j to heat up a kg of iron 1C. So it takes about 70 MW to heat up the missile by 1 degree c. So with a gw a second in waste heat in 2 minutes the missile will be 1700 degrees warmer than it was at the start.

Oh, and at 1700C it's radiating blue-white light, so that might impact tracking and such.


Must be the battlesteel, somehow has absolutely ridiculous heat shedding ability
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Re: Heat Disposal on ships
Post by Bill Woods   » Sat Apr 15, 2017 3:58 am

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Daryl wrote:Much as I love the series, heat disposal is just one of the unique physics attributes of the Honorverse. Accellerating a 6 megaton SD at 450 gs/s requires absurd amounts of energy that comes from wedge technology, could never come from a nuclear fusion reactor. Essentially a perpetual motion machine plus.
In Flag in Exile he talks about bombarding installations with 0.99C missiles. I'm too rusty to do the maths but under relativity a 100 ton missile at that speed would be much heavier with the mass coming from E=MC2, so a lot of energy.

At 0.99c, kinetic energy would be about 6 times rest mass, or about 130 megatons per kilogram. Putting an explosive warhead on it would be superfluous.

Of course, reaching 0.99c is hard. If a ship is going 0.8c, and launches a standard Mk23 missile, it'll almost reach 0.96c, packing 'only' 53 Mt/kg.
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Re: Heat Disposal on ships
Post by JohnRoth   » Sat Apr 15, 2017 8:03 am

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The waste heat thing keeps coming back and coming back and coming back. Here's the key quote:

Mission of Honor, Chapter 9 wrote:It wasn't perfect, of course. The system's greatest weakness was that it couldn't give complete coverage. Like any stealth system, it still had to deal with things like waste heat, for example. Current technology could recapture and use an enormous percentage of that heat, but not all of it, and what they couldn't capture still had to go somewhere. And, like other navies' stealth systems, the MAN's dealt with that by radiating that heat away from known enemy sensors. Modern stealth fields could do a lot to minimize even heat signatures, but nothing could completely eliminate them, and stealth fields themselves were detectable at extremely short ranges, so any ship remained vulnerable to detection by a sufficiently sensitive sensor on exactly the right (or wrong) bearing.


Let's assume for the sake of an example that "enormous percentage" is 80%. Then 80% of the recirculated heat also is captured and reused, for another 16%. Etc. Either there's something wrong with my math, or you can run a superdreadnaught on a pair of AA batteries.

Well, that's a bit of an exaggeration, but it makes more sense to me than dumping it into the next hyper band. To dump it you still have to collect it, and in any case Ghost class ships can't dump the heat there. Nor can LACs, etc.

To answer the obvious question: it's quantum magic, similar to "spooky action at a distance," aka quantum entanglement.
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Re: Heat Disposal on ships
Post by JohnRoth   » Sat Apr 15, 2017 2:41 pm

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DerHenker wrote:ships in orbit could dissipate the heat into the ionosphere of the planet which they are orbiting. Missiles in ballistic segments won't be in ballistic for too long probably.


kzt wrote:Say 2 minutes, with an exawatt fusion reactor running. How hot will a 150 ton missile get when the incredibly efficient reactor radiates a mere gigawatt a second into the missile body? Assume it's all made of iron to make this easier.

It takes 450j to heat up a kg of iron 1C. So it takes about 70 MW to heat up the missile by 1 degree c. So with a gw a second in waste heat in 2 minutes the missile will be 1700 degrees warmer than it was at the start.

Oh, and at 1700C it's radiating blue-white light, so that might impact tracking and such.


Somtaaw wrote:Must be the battlesteel, somehow has absolutely ridiculous heat shedding ability


Nah, it isn't shedding heat, it's using an enhanced version of the thermoelectric effect to convert most of it to power.
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Re: Heat Disposal on ships
Post by Vince   » Sat Apr 15, 2017 3:09 pm

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JohnRoth wrote:The waste heat thing keeps coming back and coming back and coming back. Here's the key quote:

Mission of Honor, Chapter 9 wrote:It wasn't perfect, of course. The system's greatest weakness was that it couldn't give complete coverage. Like any stealth system, it still had to deal with things like waste heat, for example. Current technology could recapture and use an enormous percentage of that heat, but not all of it, and what they couldn't capture still had to go somewhere. And, like other navies' stealth systems, the MAN's dealt with that by radiating that heat away from known enemy sensors. Modern stealth fields could do a lot to minimize even heat signatures, but nothing could completely eliminate them, and stealth fields themselves were detectable at extremely short ranges, so any ship remained vulnerable to detection by a sufficiently sensitive sensor on exactly the right (or wrong) bearing.


Let's assume for the sake of an example that "enormous percentage" is 80%. Then 80% of the recirculated heat also is captured and reused, for another 16%. Etc. Either there's something wrong with my math, or you can run a superdreadnaught on a pair of AA batteries.

Well, that's a bit of an exaggeration, but it makes more sense to me than dumping it into the next hyper band. To dump it you still have to collect it, and in any case Ghost class ships can't dump the heat there. Nor can LACs, etc.

To answer the obvious question: it's quantum magic, similar to "spooky action at a distance," aka quantum entanglement.

It's not quite that bad, although it's bad enough. A spider drive ship can't dump heat into the next higher band, unless it is A) in hyperspace and B) in a gravity wave or C) transiting a wormhole terminus*. But in normal space, it has to radiate all the heat it can't use back to space.**

A LAC, pinnace, or missile, unless it is coasting with its wedge completely off, can use the wedge to dump heat into the next higher hyper band. This works in normal space as well as hyperspace (as long as the LAC, pinnace, or missile is in a hyperspace rift).

* David has said 'why do you think the spider ships can't transit wormholes?' or words to that effect on this forum. Since transiting wormholes require Warshawski sails (as well as a hyper drive), we can infer that a spider drive carries Warshawski sails and therefore can make use of gravity waves. As well as using the sail to dump heat to the next higher hyper band.

** A spider ship could in theory have its Warshawski sails up in normal space (not in preparation for transiting a wormhole) and dump heat into the alpha band of hyperspace, but I don't see how that would help the spider ship carry out its mission, since it relies primarily on not being detected. Obviously, a LAC pinnace, or missile cannot do this as they lack Warshawski sails.
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Re: Heat Disposal on ships
Post by kzt   » Sat Apr 15, 2017 3:41 pm

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Missiles have no wedge when they have no wedge. The wedge on a stage cannot be shut down and restarted, nor can its strength be altered once started. The nodes burn out once you shut it down, and they burn out if you keep it running.
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Re: Heat Disposal on ships
Post by Vince   » Sat Apr 15, 2017 5:42 pm

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kzt wrote:Missiles have no wedge when they have no wedge. The wedge on a stage cannot be shut down and restarted, nor can its strength be altered once started. The nodes burn out once you shut it down, and they burn out if you keep it running.

True, but any fusion powered dual or multi drive missile that incorporates coasting (wedge off) in its flight profile still has the issue of not having a way to dump heat into the next higher hyper band. The same issue also applies to fusion powered Ghost Rider reconnaissance drones while they have their wedges powered off.
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Re: Heat Disposal on ships
Post by kzt   » Sat Apr 15, 2017 5:54 pm

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Vince wrote:True, but any fusion powered dual or multi drive missile that incorporates coasting (wedge off) in its flight profile still has the issue of not having a way to dump heat into the next higher hyper band. The same issue also applies to fusion powered Ghost Rider reconnaissance drones while they have their wedges powered off.

Exactly.
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Re: Heat Disposal on ships
Post by Somtaaw   » Sun Apr 16, 2017 10:30 am

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Vince wrote:
kzt wrote:Missiles have no wedge when they have no wedge. The wedge on a stage cannot be shut down and restarted, nor can its strength be altered once started. The nodes burn out once you shut it down, and they burn out if you keep it running.

True, but any fusion powered dual or multi drive missile that incorporates coasting (wedge off) in its flight profile still has the issue of not having a way to dump heat into the next higher hyper band. The same issue also applies to fusion powered Ghost Rider reconnaissance drones while they have their wedges powered off.


I think that the Ghost Rider drones actually don't completely turn off their wedge.

We know that Ghost Rider drones can cut their stealth, evidences on numerous occasions from Tsang, to Filareta, and a few of the Solarian provocations post-New Tuscany. This implies it's not simply absorbent hulls but active emitted stealth fields too, which are also inherently detectable, even if you have to really, really be looking for those.

Storm from the Shadows, Ch 43 wrote: In powered-down passive mode, the way Kaplan had left them, their endurance had been good for far longer than the twenty-three T-days since the destruction of Commodore Chatterjee's destroyers. Now, in response to the properly authenticated command codes, they were fully awake once more, faithfully reporting everything they'd seen over those three T-weeks via grav-pulse, which amounted to real-time reporting at this range.


This would imply their capacitors have to be good for running active stealth fields, and sensors, AND the AI core, which I'm going to give it a nominal max of 30 T-days in powered down mode.

And we also know that Honor, on more than one occasion usually while pirate hunting in Silesia, that ships (and therefore Ghost Rider drones) can scale their wedge strengths down, and then back to full strength for combat. So I assume that Ghost Rider drones scale their wedge all the way down to station keeping minimum strength, and then stop moving at all, which also enhances their stealth fields coverage, and allows them to keep that fusion core running without succumbing to the heat detection.
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