I've just got 14 minutes out of the nuclear engines. Stock parts

[Greenfire32]

yeah...we definitely need radiators of some kind. Mining resources has no real value since all the ISRU does is overheat as soon as you turn it on (at least for me anyway).

So, while I like having heat-management as another aspect of the game, we also need ways to....you know...manage the heat...

[Brotoro]

http://upload.wikimedia.org/wikipedia/commons/e/e0/Bimodal_Nuclear_Thermal_Rocket.jpg

It is my understanding that the black, conical bit at the bottom includes radiators.

I'd believe that. Those engines are bimodal designs that are meant to operate in a mode for generating electrical power (in addition to being a rocket engine), and I can't see how they could accomplish that without a radiator.

[tater]

I'd believe that. Those engines are bimodal designs that are meant to operate in a mode for generating electrical power (in addition to being a rocket engine), and I can't see how they could accomplish that without a radiator.

That's true, they are indeed bimodal, and hence run all the time without coolant (propellant) spraying through the core and out to space.

Edited May 1, 2015 by tater

[Requia]

First, I'm not sure real nervas overheat as much

It'd be flat out impossible for a real one to overheat as a result of operator error in vacuum (dumping multiple tons of superheated hydrogen into an oxygen rich atmosphere is probably a really bad idea though). Unlike other rockets, you don't make more heat the more fuel you dump into it, the heat output is fixed. Throttling it down won't prevent a meltdown if one is gonna happen (though it might happen slightly faster, since the rocket exhaust carries some of the heat away).

Thanks for this test though, damn thing just melted my fuel tank, 14 minutes should be more than enough though.

[Aerindel]

Are you using mammoth engines as mid-stage?[/quote

Yes, but they are ejected at about 50km and the last bit to orbit is accomplished with atomic engines. I'm not saying I need that specific craft to work, I was just making a point that at this point in my game, after I've been playing for two years, I'm not really interested in sending small one craft missions anymore, those are too easy. I want to be able to build giant go anywhere do an anything ships after I've unlocked the entire tech tree. These ships are very hard to get into orbit, they often require assembly or at least refueling in orbit, and they are hard to fly, often needing 20 minute burns to get anywhere. I don't think they are easy or a cheat and I don't see why the LVN's needed to be nerfed. Don't forget, they don't just have overheating issues now, they also only have 75 percent of the thrust they used to, and the fuel tanks for them only hold half as much.

[Frozen_Heart]

only have 75 percent of the thrust they used to

I swear that they've always had 60kN?

[m4v]

First, I'm not sure real nervas overheat as much.

Real NERVAs probably don't overheat like that, however with a real one you will have to deal with the deadly radiation of an unshielded nuclear reactor and the mass of the shadow shield protecting the rest of the vessel. Sounds like a fair trade-off.

[Aerindel]

Real NERVAs probably don't overheat like that, however with a real one you will have to deal with the deadly radiation of an unshielded nuclear reactor and the mass of the shadow shield protecting the rest of the vessel. Sounds like a fair trade-off

Not at all, that would be fun to design around. I love the idea of making giant ships with long truss structures isolating the engines behind shields, We could build ships like the the one in the beginning of Avatar.

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I swear that they've always had 60kN?

Your right, I was looking at the wrong engine.

[Frozen_Heart]

Real NERVAs probably don't overheat like that, however with a real one you will have to deal with the deadly radiation of an unshielded nuclear reactor and the mass of the shadow shield protecting the rest of the vessel. Sounds like a fair trade-off.

I always stick my LV-Ns and isotope generators well away from crew compartments, isolated by heavy equipment, fuel, and where needed metal panels. I'm always working with those restraints so if they're added that isn't a problem.

[Brotoro]

I ain't 'fraid of no RTGs.

[regex]

I always stick my LV-Ns and isotope generators well away from crew compartments, isolated by heavy equipment, fuel, and where needed metal panels. I'm always working with those restraints so if they're added that isn't a problem.

As stated before (I should copy this statement for easy reference), if that isn't enough, the fact that you're pushing what is essentially kerosene with the thermal properties of Aerozine 50 through it and still getting liquid hydrogen isps without worrying about proper handling of liquid hydrogen (a heat mechanic, I might add) should be a fair trade-off.

They're much more manageable in 1.0.1, though. heatProduction is down to 100 from 240 (the values are changed from the previous because of how thrust is calculated in based on vacuum isp, instead of SL isp as in 1.0) and its emissiveConstant has been raised to 0.83.

[Commissioner Tadpole]

Honestly, the new heat system is so frightingly complex I've just said "screw it" and deactivated it. (Still amazed at how the game doesn't treat space as being cold, though)

Dealing with radiation from RTGs and Nervs, on the other hand...

[regex]

Still amazed at how the game doesn't treat space as being cold, though

Space isn't "cold". This is also the reason why it takes longer to radiate heat away from the craft in space.

[m4v]

I always stick my LV-Ns and isotope generators well away from crew compartments, isolated by heavy equipment, fuel, and where needed metal panels. I'm always working with those restraints so if they're added that isn't a problem.

I very much doubt that that will work given that the shadow shield of a nuclear engine is a very heavy thing made of specific materials designed to stop gamma and neutron radiation.

There's another issue, are you careful about where you point your ship too? because I wouldn't want to be anywhere closer than 200km of the wrong end of a nerva.

edit: note that the "wrong end" is anywhere but the very front of the vessel, inside the narrow shadow of the shield.

Edited May 1, 2015 by m4v

[Frozen_Heart]

wouldn't want to be anywhere closer than 200km of the wrong end of a nerva

You do realise that the exhaust of a NERVA isn't radioactive right?

[m4v]

You do realise that the exhaust of a NERVA isn't radioactive right?

uhm, yes? is the nuclear reactor the thing spewing the gamma and neutron radiation.

[Frozen_Heart]

uhm, yes? is the nuclear reactor the thing spewing the gamma and neutron radiation.

The reactor will be giving out radiation but as it spreads out so quickly it won't be a problem past a km or so. The intensity follows the inverse square law and so becomes vanishingly small very fast.

[tater]

Honestly, the new heat system is so frightingly complex I've just said "screw it" and deactivated it. (Still amazed at how the game doesn't treat space as being cold, though)

Dealing with radiation from RTGs and Nervs, on the other hand...

Regex beat me to this, but it bears saying again, as many people don't understand this. Vacuum is an insulator (hence the thermos, as the joke says, "it keeps hot things hot, and cold things cold---but how do it know?").

ALL heat generated needs to be radiated.

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uhm, yes? is the nuclear reactor the thing spewing the gamma and neutron radiation.

There is a shilled on the top of the engine, and the crew compartment is supposed to be within the solid-angle shielded. I never hang nervas on the side, I always have them on the bottom, with the crew compartment on top.

[Canopus]

The LV-N shouldn't need radiators unless they add a secondary setting just for generating electricity without producing thrust.

[Legendary Emu]

Look on the bright side: You can make cool retro atomic rockets with wings and stoof.

[Radam]

They're much more manageable in 1.0.1, though. heatProduction is down to 100 from 240 (the values are changed from the previous because of how thrust is calculated in based on vacuum isp, instead of SL isp as in 1.0) and its emissiveConstant has been raised to 0.83.

Last I looked in cfg, the heating value for lv-n is now 432. So it has to have something to do with something else.

[regex]

Last I looked in cfg, the heating value for lv-n is now 432. So it has to have something to do with something else.

You didn't read what I wrote. Because of how thrust calculation changed to be based off max thrust (vacuum thrust) the calculation for heatProduction has changed. To get the old value use (ispSL/ispV*heatProduction) = oldheatProduction. In this case, 185/800*432 = 99.9.

[Requia]

Later designs didn't even have that low thrust. Their TWR was pretty good.

By Kerbal standards yes. By real world standards not so much. Best design I can find numbers for is about 7 to 1.

[Tobyz28]

Alternate solution: Higher tier, higher cost, higher mass nuclear Engine with better heat dissipation further up the tech tree.

I agree radiators would be "cool" (haha) but at the same time i don't want to feel like i'm forced to have to use the same formula every time to use a NERVA engine.

[Geschosskopf]

I agree radiators would be "cool" (haha) but at the same time i don't want to feel like i'm forced to have to use the same formula every time to use a NERVA engine.

You've got ModuleManager, right? Just make a cfg file that tweaks the various values of the LV-N to whatever you think is best. Then it doesn't matter how the LV-N works in stock, you can make it do whatever you want. I thought the stock overheating totally ruined the thing, so I changed it so I no longer have to worry about it.

ModuleManager is seriously the single best mod out there, because it makes everybody a modder without having to edit any of the original files.