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PSA: Nuclear engine overheating


THX1138
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Let us know how it performs in vacuum, I really should start some tests outside of the atmosphere.
Reporting back in, that design worked much better than the previous. I managed a ten minute burn at about 0.5 TWR. The first half was full-bore, I only started reducing the throttle when the NTRs were reaching about 2100. Once the burn was finished ... well, this is six minutes after the burn:

sXiG6a6.png

It takes a long time for the ship to dissipate that heat.

Anyway, I think the LV-N could drop its heat production to 100. It would still require radiative parts but the heating would be much less punishing. OTOH, I'm pretty sure I can do my tour with this thing just fine.

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After giving it a fair chance, I'm sorry to say I no longer find the LV-N engine fun to play with. When I saw the liquid fuel requirement and the increased mass I was excited and couldn't wait to try it.

However, the massive heat production from the engine effectively locks you out from playing the game at regular intervals. To me, that is not fun gameplay. Spamming parts to act as "radiators" is not a viable workaround when I'm already working with hundreds of parts and a low framerate.

Either the heat production from the LV-N needs to be toned way down, or we need a SINGLE heat-sink part that can be placed above an LV-N to remove all heat problems from the engine.

Edited by Kerano
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After giving it a fair chance, I'm sorry to say I no longer find the LV-N engine fun to play with. When I saw the liquid fuel requirement and the increased mass I was excited and couldn't wait to try it.

However, the massive heat production from the engine effectively locks you out from playing the game at regular intervals. To me, that is not fun gameplay. Spamming parts to act as "radiators" is not a viable workaround when I'm already working with hundreds of parts and a low framerate.

Either the heat production from the LV-N needs to be toned way down, or we need a SINGLE heat-sink part that can be placed above an LV-N to remove all heat problems from the engine.

Well there are 2 easy solutions to this IMHO.

#1- When the Interstellar mod is patched for 1.0 simply copy the necessary radiator files to your game and use these. I plan on trying that myself eventually, unless we get stock ones.

#2- Edit the .cfg file for the Nerva, and reduce the amount of heat it generates to manageable levels. Barring good radiators this is the easiest solution.

I plan to try the trick with the airbrakes because they are small enough and stick almost anywhere. If the stock solutions doesn't work, I'll customize my game to make it fun again.

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I played around with the values tonight, I think dropping the heat production from 240 to 100 would be about right. It still means you'll need some radiative parts for craft with more than, say, two engines, but a simple craft with seven of those 800 tanks and a single NTR did a seventeen minute burn on those settings without overheating (1500 heat at that point). My revamped tug with the mess of radiators and four NTRs was well on its way to overheat about ten minutes in. Both of those craft could manage transfers to pretty much anywhere in the system.

Multiple NTRs will obviously cause problems.

Still, I feel like stock right now is just fine and a single, or even double, NTR is more than manageable with a few extra parts, considering burn times and such. It would get hairy braking at Moho for sure, but an enterprising player could manage.

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I wonder if having an engineer aboard does anything like it does for the isru and drills...

an excellent point. I will do the test after I come back from work.

Looking at the game files quickly, engineer will not work, since it doesn't have that bit of code to handle it. Should be moddable.

The drill has got this:

AutoShutdown = true
GeneratesHeat = true
TemperatureModifier = 50
UseSpecializationBonus = true
SpecialistHeatFactor = 0.2
SpecialistEfficiencyFactor = 0.1
SpecialistShutoffTemp = 0.40
DefaultShutoffTemp = 0.25
Specialty = Engineer
EfficiencyBonus = 1.0

Edited by Torham234
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Still, I feel like stock right now is just fine and a single, or even double, NTR is more than manageable with a few extra parts, considering burn times and such. It would get hairy braking at Moho for sure, but an enterprising player could manage.

Might make sense to add some weight efficient conventional emergency engine (similar to the nukes combined thrust) for hairy situations, although that might screw with your delta-v. Not that it could get worse than new stock.

Edited by Temeter
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Is it me, or does this seem off.

pulled from config file.

"

// heatConductivity = 0.06 // half default

emissiveConstant = 0.8 // engine nozzles are good at radiating.

"

is the heatConductivity suppose to be commented out. Has anyone removed the first set of // and tested the engine?

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Did a lot of tests in sandbox mode with different 1.25m parts above the LV-N and came across a few interesting things. Summary: Part directly above LV-N should contain minimal or no fuel mass.

* The part directly above the LV-N always gets the brunt of the heat.

* Thermal mass seems to be the key value in the debug right click menu. The lower the better. If it's too high on a small part it'll overheat QUICKLY above an LV-N.

* Fuel adds a lot of thermal mass. A small Mk1 tank full of fuel will overheat quickly. Empty the same tank, and now it will heat up much more slowly... so slowly that the LV-N itself will usually explode first on 100% power instead of the empty tank.

* Engine pre-coolers seem to be a decent choice above LV-N engines mainly because of their low fuel mass. They don't dissipate heat in space though.

* Structural fuselages work even better, due to the complete absence of fuel. Wastes a part though.

* Ore containers actually work brilliantly, especially when full. Ore itself doesn't add any thermal mass, and depending on your ship you may actually have a use for ore containers anyway.

* Dipping into 1000x time warp briefly will reset thermal values to default levels for all parts on the ship. Nice to know if you're in a tight spot and all else fails.

Edited by Kerano
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Did a lot of tests in sandbox mode with different 1.25m parts above the LV-N and came across a few interesting things. Summary: Part directly above LV-N should contain minimal or no fuel mass.

* The part directly above the LV-N always gets the brunt of the heat.

* Thermal mass seems to be the key value in the debug right click menu. The lower the better. If it's too high on a small part it'll overheat QUICKLY above an LV-N.

* Fuel adds a lot of thermal mass. A small Mk1 tank full of fuel will overheat quickly. Empty the same tank, and now it will heat up much more slowly... so slowly that the LV-N itself will usually explode first on 100% power instead of the empty tank.

* Engine pre-coolers seem to be a decent choice above LV-N engines mainly because of their low fuel mass. They don't dissipate heat in space though.

* Structural fuselages work even better, due to the complete absence of fuel. Wastes a part though.

* Ore containers actually work brilliantly, especially when full. Ore itself doesn't add any thermal mass, and depending on your ship you may actually have a use for ore containers anyway.

* Dipping into 1000x time warp briefly will reset thermal values to default levels for all parts on the ship. Nice to know if you're in a tight spot and all else fails.

... are you talking about, in my experience more thermal mass the better. If possible use 14t lf tank and you can do 10 minute burns at full bore.

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* Thermal mass seems to be the key value in the debug right click menu. The lower the better. If it's too high on a small part it'll overheat QUICKLY above an LV-N.

* Fuel adds a lot of thermal mass. A small Mk1 tank full of fuel will overheat quickly. Empty the same tank, and now it will heat up much more slowly... so slowly that the LV-N itself will usually explode first on 100% power instead of the empty tank.

These two are exactly backwards, IME. Parts with higher thermal mass gain temperature more slowly than those with less thermal mass for a given amount of heat energy input, that's what thermal mass is.

* Ore containers actually work brilliantly, especially when full. Ore itself doesn't add any thermal mass, and depending on your ship you may actually have a use for ore containers anyway.

I don't think that is exactly correct. Resources have their own specific heats defined in ResourcesGeneric.cfg, ore included. Not at my KSP computer to check, ore might have a low enough specific heat that it doesn't add much thermal mass but it must add some.

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Couldn't you just place a heat shield between the LV-N and the fuel tank facing the LV-N? Seems to work for my spaceplanes so far.

Nerv tend to explode after a few minutes in space. I was able to thrust them about 6 minutes at full power with my asteroid tug after some trial-and-error without too much overheating:

C356068BED79E013EC19DD161CDD53A433C4FBDF

We still need radiator but it's not to hard after you know how to keep it cool.

Also is very cool looking! :D

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Yeah the thermal mass isn't adding up, must be something else. Well whatever the cause, structural fuselages, ore containers and empty fuel tanks are 1.25m parts which don't preemptively explode in space when attached to an LV-N. Useful to know.

- - - Updated - - -

I don't think that is exactly correct. Resources have their own specific heats defined in ResourcesGeneric.cfg, ore included. Not at my KSP computer to check, ore might have a low enough specific heat that it doesn't add much thermal mass but it must add some.

Not according to the values displayed in debug. 200 for both full and empty small ore container.

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Just looked, it's emissiveConstant is 0.95, so it's probably a good one to use.

Tried it tonight the Airbrakes stay orange with debug colouring while everything around them is bright yellow.

heatConductivity = 0.06 // half default seems to the main difference to wing configuration.

They do seem like they aren't conducting the heat as fast as other parts.

To bad it does look cool to have them on there.

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Just a note for people using nuclear engines to keep an eye on the overheating because things have changed. I alt + tabbed out and came back to find I had no engines when previously they'd have been okay if left at 90% thrust (I have four grouped close together). Now they're overheating at 50% continuous thrust.

This reminds me of something I found myself running across in 0.90.

HDVVhWG.png

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Bottom line is, the nukes are unbalanced.

They make burn times long as it is. Having to throttle down to prevent overheating is madness. Having to add stupid looking extra parts just to make the engine work properly is madness.

Squad need to fix these asap.

- - - Updated - - -

This is a petty cosmetic thing, but I really wish the thermal display's color spectrum was blue for cold parts, transitioning to red, then yellow, then white. It's just odd for cold parts to be red.

Also agreed. it is very misleading..

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This is a petty cosmetic thing, but I really wish the thermal display's color spectrum was blue for cold parts, transitioning to red, then yellow, then white. It's just odd for cold parts to be red.

Maybe I'm misreading you, but shouldn't it move from red to white to blue? Blackbody radiation is opposite the shower handles: hot parts glow red, hotter parts glow white, and really really hot things glow blue.

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Maybe I'm misreading you, but shouldn't it move from red to white to blue? Blackbody radiation is opposite the shower handles: hot parts glow red, hotter parts glow white, and really really hot things glow blue.

That would be more realistic, but I think the playerbase in general is likely more intuitively familiar with shower handles (I certainly am). Just my opinion. :)

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Maybe I'm misreading you, but shouldn't it move from red to white to blue? Blackbody radiation is opposite the shower handles: hot parts glow red, hotter parts glow white, and really really hot things glow blue.

Amorymeltzer is correct. Except that solid objects aren't going to get blue-hot before vaporizing...but the hottest stars are bluish hot.

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