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-   -   [Spaceships] Heat Signature, Cloaking Device, and Stealth Hull (http://forums.sjgames.com/showthread.php?t=76114)

Anthony 08-28-2015 09:46 AM

Re: [Spaceships] Heat Signature, Cloaking Device, and Stealth Hull
 
Quote:

Originally Posted by Mailanka (Post 1931644)
Any thoughts on how one would dump all that IR at once?

If you're storing the heat in some form of chemical store (such as fuel tanks), you can dump the chemical store. Depending on the nature of your coolant, you might also let it boil away, which will usually only use up some of your coolant.

Ulzgoroth 08-28-2015 10:06 AM

Re: [Spaceships] Heat Signature, Cloaking Device, and Stealth Hull
 
Quote:

Originally Posted by Varyon (Post 1931625)
A heat sink doesn't store heat, it dumps it. That is, with reactors, the heat sink (main radiator array) is the source of the ship's IR signature. Shutting down the heat sinks should lower your IR signature, and I posted a system for this upthread.

Using 'heat sink' to refer to thermal masses that are used as reservoirs to dump heat into is pretty common. Do you have an alternate term for those?
Quote:

Originally Posted by Varyon (Post 1931625)
Spaceships doesn't currently have a system for dumping the heat that is built up while the main radiators are closed (presumably, it's meant to be something like "once you open the radiators again, all built up heat is gone," but that doesn't seem realistic).

Actually, it does. Page 66. Time with radiators open clears accumulated overheat on a 1-for-1 basis. Whether or not you're still running the hot systems.

Ulzgoroth 08-28-2015 10:17 AM

Re: [Spaceships] Heat Signature, Cloaking Device, and Stealth Hull
 
Quote:

Originally Posted by Mailanka (Post 1931631)
Right, yes, I should clarify. I'm thinking of a system that doesn't use radiators, because it's a ridiculous super science space opera, so the question becomes "How do I justify having a powerful reactor without the IR signature?" So far I'd been using fuel cells, but this discussion of coolant tanks (good catch) made me wonder.

So, you argue that the IR signature comes from the radiators, which makes sense. The rules discussing retracting your radiators seems to be discussing them from the perspective of avoiding damage. If I read you correctly, though, it would also lower your IR signature, because the reason we have radiators is that ships don't radiate IR energy well enough on their own.

Thus, for a spooky, super-science, radiator-less ship, the ship radiates heat well enough without an exposed radiator, but you make the case that it could, instead, choose to dump its heat into a coolant system, reducing the IR signature to, say, +3 for 30 minutes, after which the system starts to overheat

(Super science can, of course, mean anything, but if the only assumption we make is "no exposed radiators" does this pass the smell test?)

I'd say the typical space opera treatment just outright ignores the issue of the heat from the reactor. You can usually detect ships with reactors running more easily, but you do it based on neutrino emissions or something even more hand-wavy, not on the basis of the ship being so hot it glows.

That'd require some fairly heavy reconsideration of Spaceships, though, and doesn't seem to be what you're trying to do.

If you're deciding that the ships do still emit the amount of heat they should be, into normal space, just somehow doing so without anything recognizable as a radiator...which is what Spaceships defaults to, really...I'd agree that having it act like it can retract its mysteriously non-existent radiator for a low-profile mode makes perfect sense.

Optionally, you could make that capability a design option that costs extra, and/or make it a feature only of ships with a Stealth Hull.

Varyon 08-28-2015 11:05 AM

Re: [Spaceships] Heat Signature, Cloaking Device, and Stealth Hull
 
Quote:

Originally Posted by Mailanka (Post 1931644)
Any thoughts on how one would dump all that IR at once?

You have some sort of superscience technology that can pump out large amounts of heat without any sort of radiator, or at least not a large one. Saying it can actually manage several orders of magnitude more heat than it usually pumps out isn't going to break anything. Failing that, use the same technology to actually build some radiators, and you should be able to dump all that heat rather rapidly. It could have a cool visual effect - the ship momentarily unfurls some hidden radiators, there's a sudden IR spike, and the radiators retract again.

As Anthony notes, actually expelling coolant (or using some way to expel all the heat with a portion of the coolant, either through boiling or through using a heat pump to make what you're expelling super-extra-hot first) is another option. This will give you a limited number of uses of stealth.

Quote:

Originally Posted by Ulzgoroth (Post 1931656)
Using 'heat sink' to refer to thermal masses that are used as reservoirs to dump heat into is pretty common. Do you have an alternate term for those?

They're apparently called "thermal stores."

Quote:

Originally Posted by Ulzgoroth (Post 1931656)
Actually, it does. Page 66. Time with radiators open clears accumulated overheat on a 1-for-1 basis. Whether or not you're still running the hot systems.

Ah, so it does.

RogerBW 08-28-2015 11:17 AM

Re: [Spaceships] Heat Signature, Cloaking Device, and Stealth Hull
 
Something like David Brin's refrigeration laser might be tempting - if you know where the enemy is, you can send off your surplus heat in a big coherent beam away from them.

Anthony 08-28-2015 11:47 AM

Re: [Spaceships] Heat Signature, Cloaking Device, and Stealth Hull
 
Quote:

Originally Posted by RogerBW (Post 1931674)
Something like David Brin's refrigeration laser might be tempting.

Sadly, it violates thermodynamics, and if you're going to violate the second law of thermodynamics you might as well just declare you have a device that turns waste heat into useful power, meaning you don't have any heat you need to get rid of in the first place.

RogerBW 08-28-2015 02:07 PM

Re: [Spaceships] Heat Signature, Cloaking Device, and Stealth Hull
 
Quote:

Originally Posted by Anthony (Post 1931681)
Sadly, it violates thermodynamics, and if you're going to violate the second law of thermodynamics you might as well just declare you have a device that turns waste heat into useful power, meaning you don't have any heat you need to get rid of in the first place.

Sure, but it does it in a relatively subtle way.


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