Heat management is a relatively common trope in science-fiction (more toward hard-SF), and videogame examples include Mechwarrior Online and Kerbal Space Program.
It is regularly evoked on discussions here for Battlescape, at the very least for atmospheric entry, or a potential complement/replacement for energy system.
So, what should Battlescape's thermal management system look like?
First, it needs to be simple. Complexity for complexity's sake is, by itself, bad - but more than that, INS has limited resources and they shouldn't have to sacrifice a significant part of those for it.
As such, I would go for a single global parameter, representing the thermal capacity of the entire ship, and how much heat is in it. It would work like energy, but starting empty instead of full.
Ideally, missiles and other projectiles would have no heat bar, or at most a fixed number if necessary.
For example, the Bomber could have a thermal capacity of, say, 100 MJ (feel free to add/remove zeroes)
It could rise when:
- Entering atmosphere
- Getting close to the star
- Going very fast in atmosphere
- Landing on lava (Why do such a thing? Well...)
- Using thrusters (slightly) and booster
- Entering, using and/or exiting warp
- Using some energy weapons - particularly point defence lasers (side note: RL lasers are atrociously inefficient, described as "a blast furnace that also emits some light")
- Getting hit by some weapons
It could fall when:
- The hotter you are, the faster it goes away (hotter bodies radiate/conduct more heat at once)
- You are in atmosphere (conduction is more efficient than radiation to get rid of heat)
- You are landed, including on (non-lava) oceans (denser stuff conduct heat faster)
- You are docked (comparable to reloading/refueling)
- You fire some physical weapons
- You eject decoys
The last one, in particular, may create interesting gameplay: the hotter you are, the hotter the decoy (and the more heat you get rid of). If the decoy becomes more effective (even accounting for a possible penalty your ship has for being so hot), then you actually have an advantage for maintaining high heat levels during combat - but mind the penalties.
In addition, decoys would serve double duty as expendable heat sinks. But they will probably be a limited resource (whether they replenish by themselves or you have to come back to base for reload).
High heat levels may cause:
- When over the limit, emergency shut-down (that can be overridden)
- When over the limit (and still heating up), damage and/or system failures
- Being easier to detect
- Being easier to target/track (for IR missiles)
When there is heat management, there is generally radiators.
Now, classical, solid radiators may be a problem for artists that have to modify existing ship/concepts/design rules to fit them. But radiators don't have to be solid. There actually are RL concepts for those. For example, the droplet radiator.
IMHO, the best version would be a sort of transparent force-field extending from a hardpoint, containing overheated coolant.
What would it look like?
- When shut down and cool, nothing.
- When running at low heat, a dull cherry red coming from the hardpoints' openings.
- When heating up, it brightens up and goes from red to orange, yellow and even white, while emerging from the hardpoint itself and extend like a sort of lightsabre
- When at max heat, it is a blinding electric blue, and looks like it will cut anything it touches - having it cause extra collision damage to other ships may be an option.
That way, ship design wouldn't have to be significantly altered beyond placing a few more hardpoints, it would provide visual clues on the thermal state of other ships, and it would look freaking cool.
Additional effects may be nice in atmosphere and when hitting things (like the ground or ocean) with it.
Optionally, those radiators could be shut down for silent running - but heat will continue to build up, so be careful...
What about terrain?
Obviously, lava fields should heat your ship up, so there should be some heat terrain parameter.
Extended to all terrain, and a simple atmosphere model, this could affect heat conduction: the colder the place, the faster you cool down. Inversely, hot enough terrain (like lava) may even heat your ship.
On the other hand, hot terrain would more effectively hide you: you may be visible on Pluto, but less so on Earth or even Venus. And near a lava field, good luck finding you with thermal sensors - well, for as long as you can stay there.
Note that contrary to what we see in almost all media, lava is not dangerous only when you touch it. It radiates lots of heat, and heat surrounding air even more so. Atmosphere above lava should be hotter, to dangerous levels if you go close enough, even if lava radiation is too costly to implement.
This would also help gameplay, to make it more challenging to sneak by lava fields.
This wall of text may look a bit long for a simple gameplay system, but describing energy management would hardly be shorter - and if this replaces it, it may not add that much mechanics, quantity/resources-wise.
tl;dr: Heat management could be interesting, be it in addition to or instead of energy. There are obvious things like atmospheric entry, but even keeping it simple, there could be more gameplay there, with sensors and weapon use, while still keeping things relatively simple.
This is just a first draft, feel free to tear it apart and (if possible) rebuild it better!