Heat Systems and radiators

[Orbital Vagabond]

Based on a recent DevNotes, it sounds like the devs are moving to a "skin heating" model instead of a "thermal mass" model we have for heat now. The reason for this change was stated that it was impossible to appropriately balance the thermal masses in several command parts.

I may be misunderstanding this, and hence the rest of this post may not be terribly relevant.

While this is a good change, I still miss the interesting heat management from the drills in v1.0. I think keeping both heat systems would allow interesting game play while allowing balance for all appropriate systems.

I think it would be interesting to keep both systems, and track external temperature and internal heat. Skin-atmosphere interactions generate "skin heat", and machinery like drills and nukes generate "core heat". Skin heat would dissipate into the environment via convection and radiation. Core heat would slowly conduct into the skin, where it would increase skin temperature and dissipate as above. Also, core heat could be reduced using radiators, which require electricity. Making the radiators "active" helps because it represents that the system is pumping coolant around the vessel, so radiators can be placed anywhere and still dissipate core heat.

Parts can fail with surface temperature reach a certain threshold (hull rupture) or core heat exceeds a certain threshold (catastrophic explosion).

By limiting the use of radiators to dissipate core heat, the mechanism shouldn't be exploitable for removing skin heat generated during re-entry. Radiators shouldn't be effective at dissipating entry heat anyway.

Anyway, just a thought on the heat systems.

Edited June 16, 2015 by Orbital Vagabond

[Red Iron Crown]

I read it as the skin temperature mechanic being added in addition to the current thermal system rather than in place of it. Could be wrong, though.

[Orbital Vagabond]

Like I said, I may have misunderstood what the plan is.

My information is coming from this post:

1.0.3 news! Mu's been putting hours into it, he noticed even before 1.0 that balancing heating for command pods and cockpits is mutually exclusive, so they're introducing a new heating system called Skin Heating - basically, rather than seeing a part as a part, you see it as things surrounded by a shell of metal that heats up and cools down quicker - this basically makes things easier to balance overall. Same system as in Deadly Re-Entry actually [...]

So there may have been nuances in what was said during the 'cast that I'm not getting. To me, this sounds like a replacement heating system instead of an additional one, especially since they nerfed the bajebus out of the heat from drilling system, and changed the efficiency to be engineer based.

I'm sorry, but I'm not going to go watch the stream... I seriously cannot stand those...

[Starwaster]

The idea behind which is that currently, in order to raise the temperature of a part by one degree, you have to put enough heat into it to overcome its entire thermal mass. (thermal mass = mass * specific heat) Default specific heat is 800 but can be varied using a part's thermalMassModifier but STILL requires that the part's entire mass is used in the calculation

Skin uses only a fraction of that mass.

It's a modification of the existing thermal system.

[basic.syntax]

I re-listened, the relevant time mark for heat comments starts at 11:55. I think OWK summarized it correctly. Mu speaks carefully, the general thrust seems to be that skin-based heating is a replacement system.

A new heat system doesn't exclude the possibility of a return to the original heating mechanic of the ISRU parts, and may even make it more viable. But nothing has been said, that's just my speculation.

[Starwaster]

I re-listened, the relevant time mark for heat comments starts at 11:55. I think OWK summarized it correctly. Mu speaks carefully, the general thrust seems to be that skin-based heating is a replacement system.

A new heat system doesn't exclude the possibility of a return to the original heating mechanic of the ISRU parts, and may even make it more viable. But nothing has been said, that's just my speculation.

It's just a matter of part.AddThermalFlux(kilowatts)

[Rickenbacker]

Just re-posting this here from the "heat and aero" thread:

We need dedicated radiators, if we're to have heat. And the best, easiest way to handle those, IMO, is to make them work like the batteries and electricity producers do - if you have any radiators installed, any heat generated anywhere gets transferred to them automagically through invisible heat pipes, and radiated at whatever rate the radiators can handle. Any heat the radiators CAN'T handle gets transferred to the parts next to the heat source, the way it works now.

This should probably also apply to reentry heat, but that wouldn't make it an easy cheat to avoid the weight of heat shields, as any decent size radiators would probably break off from aerodynamic forces during reentry. So heatshields would still be needed there.

No need to make it overly complicated. We need radiators that let us use hotter engines, and we need a reason to use heat shields. The above suggestion covers both, I think.

[Orbital Vagabond]

Just to be clear, in my view there are two distinct sources of heat generation: Internal generation (drills, nukes) and external generation (atmospheric interaction).

Heat generated by internal sources shouldn't be able to be dissipated by methods designed for external sources, e.g. ablation

Heat generated by external sources shouldn't be able to be dissipated by methods designed for internal sources, e.g. radiators (Radiators require a heat gradient between the inside of the vessel, and the outside. When re-entering, the outside is hothothot).

As long as these two criteria are met, and is otherwise reasonable, the solution is acceptable IMO.

Rickenbacker's solution DOES tend to work, but I think it might get iffy in thin atmospheres.

[Murph]

As far as I can see, the only engine that really needs thermal management right now is the LV-N, and I regard its current heat output as fundamentally broken. We do not need radiators or other thermal management added, we need the LV-N fixed so that it doesn't generate a completely absurd amount of heat in the first place. There's no basis in reality for the current behaviour of the LV-N, as the heat generated by the reactor is transferred to the fuel and dumped out of the exhaust in the Los Alamos / NASA NERVA design.

Fix the LV-N, forget needless complexity of adding radiators (which require huge surface area pointing directly outwards (away from all other parts of the craft) to work in space. The inwards pointing surface area of the type of radiator used road vehicles is entirely useless in space, as it loses the majority of its ability to function without air flow. A road vehicle type radiator might even provide less cooling in space than a thin flat sheet of metal, as the honeycomb gaps would actually reduce its ability to radiate heat into the vacuum, as they reduce the outward facing surface area.

[Starwaster]

As far as I can see, the only engine that really needs thermal management right now is the LV-N, and I regard its current heat output as fundamentally broken. We do not need radiators or other thermal management added, we need the LV-N fixed so that it doesn't generate a completely absurd amount of heat in the first place. There's no basis in reality for the current behaviour of the LV-N, as the heat generated by the reactor is transferred to the fuel and dumped out of the exhaust in the Los Alamos / NASA NERVA design.

Ironically, the only time an NTR might use a radiator is when it's NOT in operation

[Orbital Vagabond]

I hear what you're saying, Murph, but this isn't just about the Nuke. In 1.0, the game had an interesting heat-based mechanic with drills. This mechanic was basically removed from the game (nerfed into oblivion) and could be reinstated with radiators.

Beyond the nuke and revising the drills to be similar to their old configuration, there's a lot of interesting things that could be done with a robust heat mechanic, e.g. fission reactors to produce heat (useful to power stations beyond Duna's orbit); The hotter they get, the more electricity they produce, but the more likely you are to cause it to exploded unless you have enough radiators.

[RidingTheFlow]

Engine precooler works well enough as "dedicated radiator" for me (and yes, it works perfectly to cool LV-N engines in the vacuum).

[Windspren]

How would radiators use electricity? Is this something from IRL? I thought that radiators worked by radiating away heat in the form of blackbody radiation, not by using electricity.

[Red Iron Crown]

How would radiators use electricity? Is this something from IRL? I thought that radiators worked by radiating away heat in the form of blackbody radiation, not by using electricity.

Usually a coolant is circulated from hot parts to the radiators, by a pump that consumes energy.