Thermal management system

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!


I think the eve online mechanic of overclocking modules should be implemented. It’s a good fit if thermal capacity of a ship in general is added.

Could you detail this mechanic and how it could translate in Battlescape for non-EVE players, please? :slightly_smiling:

You press the overclocking button on the modal you want to overclock Every cycle it does a certain % of damage to the modal, depending on type. Once the modal is 100% damaged you can’t use it until you repair it in a station.

That being said, heat management would be a ultra nightmare while in space. Without some sort of heat-sink ejection plates.

I wonder if compressed air blasting onto and through heat-sinks would make static heat-skins efficient. Although also a waste of air, but would be a cool mechanic for sustained combat rather then burst.

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This sounds like a different mechanic from thermal management. What would be the effect on heat on this system?

Heat management is a nightmare in space indeed. That’s why half of the solar panels of the ISS are at a 90° angle from the others: they are heat radiators, not solar panels.

Thermodynamics are one of the first walls hard-SF enthusiasts and writers hit.

That said, AFAICT heat radiation rises linearly with surface, but with the fourth power of temperature. The ships of Battlescape are already running on magitech, so having a forcefield that can resist to stupid high temperatures isn’t a problem.
So while solid radiators are limited to about 3000°K and bagels (go higher and anything melts), those ships can have force-field-contained stupid-hot coolant as radiators at a ridiculous sky blue 12000°K, or whatever hellish number we decide to go with.
At this temperature, even if our lightsabre radiators are relatively short, they can still dispose of massive amounts of heat. It would also shine like Hell’s tanning bed, vaporise nearby ice surfaces and create truly spectacular fire contrails in atmosphere, if those last two are in budget for particle effects.

And INS can relatively easily have a believable system, as they can tweak the radiator effect colour, light level and to a lesser extent size to whatever fantastic level they want.

And really, how often can you put lightsabres on starships in the name of realism?

In atmosphere, you would obviously use air cooling to drive efficiency up. In space, this would be using air as non-regenerative coolant/ejector heat sink. It would probably not make much of a difference, given how little air a starship would contain. And storing more air wouldn’t be efficient: better use more efficient heat sinks and eject those instead.
Which is how I suggest we dual-use decoys.


We dispose heat by shooting our enemies with heat rays of death - and if thermodynamics complains, it gets shot next. :stuck_out_tongue:

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This is a great idea, a unified heat management system can tie in a bunch of different game mechanics for something very interesting.

A suggestion:
Put atmospheric entry and high speed in atmosphere into a single heat factor. Heat load from flight in atmosphere is related to: density * velocity ^3

To add a bit more accuracy: an aircraft with less drag has higher heat loading factor, a craft with better aerodynamics (lower drag) will have a higher heat load than a craft with higher drag if they are flying at the same altitude and velocity. This is thoroughly non-intuitive, so perhaps not a great candidate for inclusion.

EDIT: Heat flux is proportional to (density)^(1/2) * velocity^3

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I like the idea of such system. I think core gameplay of I:B should come first, but it’s indeed a great addition to add 1. immersion and 2. to add more content to manage as a player/pilote.


[citation needed]

why should the aircraft that loses less energy to the surrounding medium due to drag have higher thermal load?

conservation of energy already disagrees with you, you dont have to call intuition into that

Part of it would be core level, the same way energy is.
I would suggest experimenting with heat instead of energy, even. I think both may be a bit redundant, and heat allows for more interesting gameplay than energy - but then again, gameplay experimentation should help there.

That makes sense; IIRC this is how KSP manages it.

I actually made a mistake here…

Heat Flux is proportional to (density)^(1/2) * velocity ^3

I agree that heat is the more interesting mechanic to track, it is more physical for spacecraft and incorporates both energy and player decisions outside of that.

I’d like an explanation of that as well. Nothing that I understand about aerodynamics supports this notion. At least, as stated. Perhaps the terms used are intended to mean something that I’m not familiar with.

A more aerodynamic, streamlined, object has a weaker shock wave that lies closer to the vehicle body. The weak shock wave and small shock layer do not remove energy from the flow before it hits the vehicle surface. That creates the conditions for very high stagnation point heat loading. Here, the flow energy is transformed from kinetic to heat energy at the vehicle surface.

A blunt body has a strong shock wave which stands off from the body, kinetic energy is transformed into heat energy at a distance and then convected around the vehicle.

If you look at any re-entry vehicle ever created, they are not low-drag vehicles. On the contrary, they are at different places high drag vehicles. Even ICBM RVs, the re-entry vehicle which carries it’s speed furtherest into the atmosphere, has a rounded nose. This is because the heat flux decreases for un-aerodynamic shapes.

A more telling example is to compare space plane designs of the early 50s (all pointy shapes similar to supersonic vehicles) to the space shuttle, with it’s massively rounded leading edges and nose.

The more exact relation for the stagnation point heating (which drives heating elsewhere on the vehicle) is: heat flux ~(density / nose radius of curvature)^(1/2) * Velocity^3

The inverse dependence upon nose radius of curvature represents the effect of shock layer standoff from the body.
The derivation comes from a similiarity solution to the compressible boundary layer, evaluated in the region of the stagnation point.

As I said, non-intuitive.


So you’re saying that a streamlined shape gives lower drag and higher heat load.

I’ll echo back my understanding of the consequences of this.

For an aircraft, the lower drag is mandatory because you’re trying to maintain a higher velocity, so you find materials that can handle the heat load on the skin. For example, the SR-71 and it’s titanium skin that heats to 230C. Going any faster than that would require materials that could handle the heat. Or engines powerful enough to push a less-streamlined shape made of the same materials.

For a spacecraft entering the atmosphere, velocity is undesirable, so the blunt shape with higher drag and lower heat load is the clear choice.

So if I have one set of materials for one world with standard engines and another world with superpowerful engines, the standard engines guys will run streamlined shapes at slower speeds while the superpowerful engine guys will run blunt bodies at higher speeds.

INS, work up some shock wave art.


hm… that way around it makes sense, thanks for the explanation :slightly_smiling:

This is precisely the trade-off for high speed flight. It is the reason why cruising hypersonic aircraft are such a challenge. To cruise, it requires high aerodynamic efficiency. But that high aerodynamic efficiency creates high heat loading, which requires advanced materials. It gets worse that at hypersonic conditions, lift forces are generally lower than at supersonic or subsonic conditions, so there is less room to trade aerodynamic performance for better heat performance.

There is yet another consideration, which argues against including this. As I-Novae isn’t going to run their aircraft designs through a CFD simulation to get metrics, any heat load / drag value is going to be purely arbitrary. In that case, assigning higher heat loads to a fighter is not really valid, because I-Novae hasn’t tested the affect of smaller surface area, etc.

TL;DR - This is an interesting physical phenomenon with high significance for aircraft design. For Infinity, stick to vehicle heat flux equal = k * (density)^(1/2) * V^3, where k is a parameter chosen to balance each vehicle and produce desired relationships.

One last thought here: with the physical considerations in mind, a streamline aircraft shouldn’t have significantly lower heat loading than a blunt aircraft. K should probably scale on a relationship of: frontal surface area / drag coefficient.

It should not be simply K = small for fighters, K = big for bombers.


Thank you so much for this! This makes a lot of sense! I love learning about aerodynamics that I didn’t know.

Funfact about SpaceX is their breaking burn(hypersonic retropropulsion) at reentry is effectively using this idea when decreasing speed by convential rocket methods by also by creating that larger shock cone. The exhaust is actually working as a heat shield for the rocket and it’s engines by creating that barrier to prevent convection.

I hope I’m getting my terminology correct.


I came across this video and thought it might be useful toward discussion about atmo reentry and heat management. It explains everything in a really straightforward way.

I can’t remember where it was discussed but I assume there will be some kind of gameplay restriction for punching down vertically into a planet’s atmosphere from space at top speed. I know we are dealing with advanced space ships but if they can be damaged with a collision they can be damaged slamming into a dense atmosphere :stuck_out_tongue:


This is amazing I love it. Thanks for sharing!