How does Overheating generate?

[MalfunctionM1Ke]

Hi Guys as the topic says,

I am pretty curious what creterias must be met to have an engine overheat

As you see below. I have a two ships docked together, both with 2x Nerva engines but only the front engines overheat.

Is it the parts around it in a radius that will overheat it?

[Geschosskopf]

I think something's wonky with overheating. I have the same question. I mean, I'm a fireman so I know a little about how heat moves around . In your pic, the lower engines are exposed not only to their own operating heat but also the radiant heat from the flares of the upper engines, so they should be overheating before the uppers. But NNNNNNOOOOOOOOOOOOOO, it's the other way around.

However, I don't pay it much mind. I've burned nuke engines for 15 minutes at a time and while they overheat a little, they never come anywhere near filling the bar and exploding.

[MalfunctionM1Ke]

Yeah but the other thing is the Mainsail.

Overheating under an Orange tank but working absolutely fine when I put a X200-8 between them.

Very mysterious

[UbioZur]

In Unity (the game engine of KSP), Overheating is dependant of the distance of the center of mass of the attached object.

Since the Jumbo is Long, is center of mass is further away of the attach node that other tanks, and this is why make the mainsail overheat.

A quick fix is to put small tank under it (plus it had a bit of fuel).

[MalfunctionM1Ke]

That explains almost everything. But it is not a very realistic model.

[Rhomphaia]

Yeah but the other thing is the Mainsail.

Overheating under an Orange tank but working absolutely fine when I put a X200-8 between them.

Very mysterious

It is actually the orange tank that is the problem there.

Parts dissapate heat into the parts connected to them. But I think it applies only in a stack or radially parent to child, but not child to parent. Since your rear engines are on a longer stack there are more parts to dissipate the heat.

In the case of the orange tank, It is just to long for the game engine to detect the connection, so there is no heat dissipation.

[WafflesToo]

That explains almost everything. But it is not a very realistic model.

Realistic? THIS! IS! KERRRRRRBAAAAAAAAL!!!

[Kulebron]

I sometimes put a 1 kg strut between Mainsail and the orange tank.

[Geschosskopf]

@ UboZur & Rhomphaia

Thanks for the info on how overheating works. As in, very strangely. While we're on the subject, maybe you all could answer a few more questions?

In the real world, heat moves by convection, conduction, and radiation. Convection requires a surrounding atmosphere so isn't a factor in space. What you all have described above is a somewhat wonky way of doing conduction. Am I to understand, then that radiation isn't a factor at all? Geez, that's usually the primary means of fire spread in real life. For instance, a major house fire will melt the vinyl siding right off another house 100 feet away and possibly even set it on fire without any sparks flying between the 2.

But we all build rockets like the in the OP's pic, with the fire from radial engines burning just a few feet away from central fuel tanks. It's always worried me that the radiant heat from these fires would overheat the central tanks but it's never happened. Does the tank heat up at all from this? I usually put radial engines out on long I-beams to minimize such heating but now I'm wondering if this matters at all.

OTOH, though, rocket fire does affect nearby parts, as seen on the F3 list when Sepratrons remove side tanks. Why does this happen in this situation and not the above? Or is this the result of direct flame impingement and not radiant heat?

Thanks in advance.

[Rhomphaia]

Rocket exhaust only damages parts that it impacts directly, there is no real radiation modeled.

[Geschosskopf]

I suppose that's a good thing