[1.0.5] Atomic Age - Nuclear Propulsion - Red Hot Radiators

[Starwaster]

So, i've got a 'little' problem, might be an integral issue of stock ksp's heat radiator system:

From what I'm seeing, heat radiators basically 'suck' the heat out of all hot parts on the ship? My current vessel is very large, and it's engines apparently are causing too much heat for the radiators, killing them (all ~16 of them) basically as soon as i start them. Even with heat cheat the heat from the radiators spreads very, very fast through the ship via conduction. Which would be issue nummer 1, is there something I can do about?

Issue number two is caused by the 'ignore max temp' cheat. Now the vessel is safe in orbit, but the heat won't radiate anymore. Context menu claims Infinity Heat, which does not sound too likely to radiate anyway. Maybe killed the number's bit-limit. Shot the thing into solar orbit and max radiation/timewarp, but no change. Some way to fix the ship, disabling the heat cheat instakills them (also casuses performance issues)? It's not the worst of cases, since it has no crew and I might get the next up via Hyperedit (first ship took like an hour to start ). I'd love to know if there isn't some kind of advanced trick to fix stuff like this, tho!

Wow, think it checks for NaN but maybe not Infinity...

You might try quick saving then reloading, that might let it start radiating ... otherwise you're editing your save file to fix the temperatures.

Long term, what you need is to add more radiators or less engines.

[Temeter]

Thx for the answer. The real problem is that i'm not talking about the ships own heat. Heck, the actual ship has 30 Lightbulbs and they seem to work just fine! It's the launcher system, might be something about the behemoth mod or just the functionality of the radiators clashing with the scale of heat production...

I'd put the radiators to the bigger tanks, but heat is spreading through the whole thing.

Whole thing feels a bit buggy, tho: The radiators heat up ultra fast, much faster than the actual engines. The engines itself aren't that heat, its only the heat surge coming from radiators.

Quicksaving/reloading doesn't work. Checked the safe, apparently only the tempExt is Infinity. Normal temp are numbers around 2.11322593762756E+299, which does seem to be like a lot. To my knowledge there is no point in correcting by hand, since the ship has like 360 parts. Again, its not a big problem either.

Edited July 5, 2015 by Temeter

[Starwaster]

Thx for the answer. The real problem is that i'm not talking about the ships own heat. Heck, the actual ship has 30 Lightbulbs and they seem to work just fine! It's the launcher system, might be something about the behemoth mod or just the functionality of the radiators clashing with the scale of heat production...

I'd put the radiators to the bigger tanks, but heat is spreading through the whole thing.

Whole thing feels a bit buggy, tho: The radiators heat up ultra fast, much faster than the actual engines. The engines itself aren't that heat, its only the heat surge coming from radiators.

Quicksaving/reloading doesn't work. Checked the safe, apparently only the tempExt is Infinity. Normal temp are numbers around 2.11322593762756E+299, which does seem to be like a lot. To my knowledge there is no point in correcting by hand, since the ship has like 360 parts. Again, its not a big problem either.

Not familiar with Behemoth, but if you say it's not the lightbulbs then I guess it's that. Has it properly been updated for 1.0? Engines scale their heat output by mass. (or by thermalMass ... I think)

I guess to actually guarantee that they overheat when they 'need' to. If someone has an engine with high output before 1.0 then it might be giving the engine a LOT of heat ...

[Temeter]

Fixed posts, checked a bit more: The heat only happens as soon as the launch clamps are decativated, the engines by itself run correct. The few heat radiators that survive after detaching clamps jump down to 23 kelvin. Definitly some kind of bug...

Behemoth Mod has been updated and otherwise works fine (large SRBs get hot but never explode, engines stay at reasonable temperatures). Found a lot of other and partly similar issues in the support forum. Seems like an issue of the game.

edit: It's possible to fix it by switching all temp(ext) Infinites to reasonable numbers, because then radiation/timewarp can actually kill the heat, no matter how ridiculous the numbers are. Makes me wonder why it switched to infinite in the first place.

edit2: Seems like there is also a (connected?) bigger issue with external part temperatures not being found (or not being defined?). It's spammed in the debug menu and, as long as heat convection is enabled, utterly cripples the framerate/simulation. Gonna be a nightmare to find out what is happening.

Edited July 6, 2015 by Temeter

[Starbuckminsterfullerton]

Yes thats exactly what I did, added intakeAtmo to the intakes. Didnt use the CRP "IntakeAtm" because according to the google doc it has 0 density, just checked interstellar tho, which is where this comes from and there it has standard intakeAir density, so i guess that's a mistake in the CRP doc. For air turbo rockets, since they should still work in vacuum I think you don't wanna use any additional intake resource at all, might be enough to give it better ISP in atmo, but not sure on exact performance of those in relation to atm density, check if you can find any precise info, if it's more complex than that you could try making it an airbreather without the need for intake resource, but have it use the jet parameters like atmcurve to precisely tune the performance.

For mk2 texture, you could always edit one of the stock textures.

Thanks for the response, I helps to know how other modders are doing things so everything can work together. I had thought about forgoing the intake resource, but I couldn't think of a way to require the presence of an intake part without one. I hadn't thought of the jet parameters, that is a good idea it might be the solution.

I could use the intakes and then create another engine mode for vacuum.

Should have thought of the stock textures for MkII, I think I have an mbm converter extension for unity.

Edit: noticed you might be planning on a ramjet, sounds cool and I am really curious to see how you make it work. You would have to disable throttle somehow right?

Edited July 6, 2015 by Starbuckminsterfullerton

[Whirligig Girl]

Are you sure this engine is low tech enough to be part of the very first aviation node?

[Porkjet]

Oh, nope, not at all, looks like you've not installed the community tech tree, it's supposed to be in a custom node that comes after aerospacetech. I do need to put the default node somewhere else to account for this.

[PanzerAce]

I've already experimented with ramjet settings, again had to cheat up the thrust compared to information i got on Project Pluto quite a bit to make it work, probably due to higher drag in KSP. It's really challenging to fly, or even boost it up to sufficient speed to get self sustaining thrust, but also much fun smashing through the landscapes a few meters above the ground at mach 3. Gotta be real careful to keep up enough speed at all times, too slow and it couldnt keep up the thrust. Also it overheated quickly, had to turn on cheats etc. Anyway, this is much fun and would fit nicely so I'll definetly make a proper nuke ramjet at some point.

Bolded the relevant part. My understanding (mostly from Atomic Rockets and wiki-walking, along with a bit of stuff from my 6 year old senior thesis) is that the solution to the overheating problem with Pluto was essentially to push it even faster through the air for the increased coolant/intake air flow through the engine.

[Dunrana]

I decided to give this mod a try, and was pleasantly surprised. This mod is TREMENDOUS and should be in the stock game!

[Starwaster]

Bolded the relevant part. My understanding (mostly from Atomic Rockets and wiki-walking, along with a bit of stuff from my 6 year old senior thesis) is that the solution to the overheating problem with Pluto was essentially to push it even faster through the air for the increased coolant/intake air flow through the engine.

Well that sure beats my idea for the bucket of water...

[rabidninjawombat]

Not sure why ive never downloaded this O_o these are amazing! Thanks Porkjet!

[Kuansenhama]

Yes. The lightbulb seems a tad OP with the 1500isp and all that thrust but I guess the high mass and absurd cost balance it out pretty well. This makes the list of top 3 mods I can't live without.

[akron]

Awesome work there. Great update!

[Starbuckminsterfullerton]

Yes. The lightbulb seems a tad OP...

Nuclear lightbulbs just are that good... or at least they are in theory. KSP is a bit different than other games in that it has to allow for 'OP' things because technology improves. Just like you say they have to be balanced with things like mass and cost. Fortunately we have cost now, it makes more things possible for modders, but balance in this game still does present an interesting challenge.

[Starwaster]

Nuclear lightbulbs just are that good... or at least they are in theory. KSP is a bit different than other games in that it has to allow for 'OP' things because technology improves. Just like you say they have to be balanced with things like mass and cost. Fortunately we have cost now, it makes more things possible for modders, but balance in this game still does present an interesting challenge.

Actually, no, they're not. The in-game stats are a fair match for what a real lightbulb would possess if we could build one.

Except that those stats are for liquid hydrogen. In the game, what we have is 'LiquidFuel' which is way too dense to be hydrogen. You need hydrogen to get an Isp that high. Denser propellants should have a lower Isp and higher thrust.

The net result is similar to that of the stock LVN where you're getting LH2 levels of performance but much higher levels of delta-V for a given volume of fuel. IRL you'd need quite a bit more tankage than you do with the lightbulb in the game.

The only way it's not OP is if you're using Real Fuel and convert the lightbulb to LqdHydrogen (same stats)

[Temeter]

Actually, no, they're not. The in-game stats are a fair match for what a real lightbulb would possess if we could build one.

Except that those stats are for liquid hydrogen. In the game, what we have is 'LiquidFuel' which is way too dense to be hydrogen. You need hydrogen to get an Isp that high. Denser propellants should have a lower Isp and higher thrust.

The net result is similar to that of the stock LVN where you're getting LH2 levels of performance but much higher levels of delta-V for a given volume of fuel. IRL you'd need quite a bit more tankage than you do with the lightbulb in the game.

The only way it's not OP is if you're using Real Fuel and convert the lightbulb to LqdHydrogen (same stats)

Honestly, I don't find the size to make it harder to use in RSS/RO. Your rockets are bigger anyway, and having a huge Liquid-Hydrogen stage isn't much of an issue in a 10m rocket. Baloon-Cryo-Tanks are afaik even a bit more light in RO, aren't they?

That said, the boiloff is imo the true culprit. Makes LH2 almost impossible to use on the long range missions you'd use a nuclear engine for. RO does provide a config to use Ammoniak tho, which has basically no boiloff in a cryo-tank on earth's solar orbit level. 'Only' 1100 ISP, but that's quiet neat, too.

Edited July 10, 2015 by Temeter

[Tellion]

RealFuels did some time ago offer the possibility of actively cooling tanks, but it seems to have disappeared ._.

[Temeter]

RealFuels did some time ago offer the possibility of actively cooling tanks, but it seems to have disappeared ._.

That sounds awesome! I've read about ServiceModule tanks being better at protecting cryo fuel, maybe it's included there? Assume it would need special ressources for cooling, too (would be cool too!).

Well, off to annoy nathan with questions!

[Tellion]

As I recall, it was just a little radiator fin that would do the job. I don't even know if it required power, but it helped a ton with using LH2 fuel.

[Temeter]

As I recall, it was just a little radiator fin that would do the job. I don't even know if it required power, but it helped a ton with using LH2 fuel.

Interesting. I wonder if current radiators work too?

[Starwaster]

Interesting. I wonder if current radiators work too?

If you mean stock radiators, no not at all. They say they're active but the parts that want cooling have to be hotter than the radiator. I think the person who coded it wasn't thinking of things like... air conditioners.... refrigerators.... both of which use compression to be able to move heat from cool areas to hot radiators.

So no, you cannot use the stock radiators to do the job.

And the RF ones are not coming back.

[Temeter]

If you mean stock radiators, no not at all. They say they're active but the parts that want cooling have to be hotter than the radiator. I think the person who coded it wasn't thinking of things like... air conditioners.... refrigerators.... both of which use compression to be able to move heat from cool areas to hot radiators.

So no, you cannot use the stock radiators to do the job.

And the RF ones are not coming back.

Aw, I assumed so.

So it's just not realistic either. Generally, how does e.g. the conceptual nuclear stage for the manned mars mission work? It's using liquid hydrogen. Does it just have the first part of the departure stage using nervas?

[Starwaster]

Aw, I assumed so.

So it's just not realistic either. Generally, how does e.g. the conceptual nuclear stage for the manned mars mission work? It's using liquid hydrogen. Does it just have the first part of the departure stage using nervas?

A real nuclear engine's reactor is kept from overheating by the propellant flowing through it. It is in no danger of overheating while it is in operation. IIRC, the ground tests would fire continuously for at least 20 minutes or until they ran out of hydrogen.

It's when you shut it off that overheating is a problem. You can't just flip a switch and shut the engine off while it's at full thrust. Instead, there is a 'cooldown' thrust stage where the engine is gradually throttled back. During this cooldown, Isp gradually drops down to (or by???) 40%. (which means that a nuclear engine burn has to be precisely calculated even more than usual)

Another method of cooldown following a burn involves a nozzle plug which descends out the bottom of the reactor core and plugs up the nozzle. Hydrogen is pumped in to cool it down and is vented. (has to be done in a manner that it doesn't cause unwanted deltaV changes. Such as venting from opposing sides perpendicular to the long axis)

Cooled down, each engine outputs 128 kW of heat which can be used to provide electrical power. (this is either a 'Bimodal' or 'Trimodal' depending on whether it also has the 'afterburner' feature. 'Bimodal' has been used flexibly to refer to an NTR that has either but not both of afterburner and electrical generation)

[Tellion]

That was very interesting to read, but he might have wondered how they want to deal with the boiloff. Or in any case, I wonder that

[Svm420]

A real nuclear engine's reactor is kept from overheating by the propellant flowing through it. It is in no danger of overheating while it is in operation. IIRC, the ground tests would fire continuously for at least 20 minutes or until they ran out of hydrogen.

It's when you shut it off that overheating is a problem. You can't just flip a switch and shut the engine off while it's at full thrust. Instead, there is a 'cooldown' thrust stage where the engine is gradually throttled back. During this cooldown, Isp gradually drops down to (or by???) 40%. (which means that a nuclear engine burn has to be precisely calculated even more than usual)

Another method of cooldown following a burn involves a nozzle plug which descends out the bottom of the reactor core and plugs up the nozzle. Hydrogen is pumped in to cool it down and is vented. (has to be done in a manner that it doesn't cause unwanted deltaV changes. Such as venting from opposing sides perpendicular to the long axis)

Cooled down, each engine outputs 128 kW of heat which can be used to provide electrical power. (this is either a 'Bimodal' or 'Trimodal' depending on whether it also has the 'afterburner' feature. 'Bimodal' has been used flexibly to refer to an NTR that has either but not both of afterburner and electrical generation)

That was interesting thanks for the info!