Quote:
Originally Posted by Varyon
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.
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). I'd have the radiators be able to handle dumping more heat than the systems normally generate, allowing them to shed built-up heat while the system is still in operation. If a system was filled to capacity, it would take 30 minutes to dump it in this way. If the system is shut down, the radiators can dump heat in half the time. While dumping heat, the vessel is at +2 to IR or a total of +6, whichever is higher (if the systems are shut down, it's at +6 total to detect if dumping at a normal rate, +8 total if dumping at twice normal).
So, let's say we've got a ship with a fusion reactor (+7 IR). If we want to drop this to +3 by closing off the main radiators, it will last for 20 minutes, +20 minutes per full tank of coolant. If the ship has 4 tanks full of coolant, it can stay in stealth mode for up to 100 minutes. At the end of this time, the ship shuts down its reactor and starts dumping heat as fast as possible. It will take 50 minutes to fully flush the system, and it will be at +8 IR during this time. If it instead opted to flush the system while the reactor was active, it would take 100 minutes and leave the vessel at +9 IR.
As for the sort of "heat sink" you're talking about (and that I originally started posting about, before looking it up and finding out a heat sink isn't what I thought it was), a tank of coolant will serve best there. I'd love a more in-depth system for those, but we don't have one currently. The coolant should last an amount of time based on the IR signature of the system(s) being cooled, as well as number of systems. As a first concept, I'd be tempted to say that coolant should be able to cool a single +6 IR system for an hour. Every +1 to IR signature would be -1 SSR to time, every -1 would be +1. Dumping heat would probably follow the above, although with the coolant normally taking an hour to fill it should take an hour to dump (or 30 minutes if dumping it while nothing else is active). For multiple systems, use the average time and divide by the number of systems. For example, take a vessel with 2 fusion reactors, a fuel cell, and a fusion torch. The reactors are each +7 IR (0.7 hours each), the fuel cell is +4 IR (2 hours), and the fusion torch has an internal footprint of +8 IR (0.5 hours). The average is about 1 hour, so divided by 4 systems that works out to 15 minutes per tank of coolant. Superscience coolant should last longer (potentially a lot longer - a cosmic power plant would fill a tank of normal coolant in all of 6 minutes). |
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?)