So how do LV-N's work now heat wise?

[XOIIO]

It sounds like now LV-N's can only be run for a specific amount of time before they overheat and explode rather than before 1.0 when they would just get about 3/4 of the way there and stop? I also ran it on the launchpad for a full minute and it didn't heat up at all, I'm assuming due to the changes and the LV-N not having actual combustion taking place anymore?

I'm going to miss that cherry red glow

[Timk]

I just did several 10 minute burns with no problem -- about half of the thermal bar was lit.

[Snark]

Testing it on the launchpad won't really tell you anything, because stuff cools off much faster in air than in vacuum (also, LV-N's have a much worse Isp in atmosphere, which means much less thrust... I wouldn't be surprised if that also means less heat, though I haven't tested that.) You could probably burn an LV-N on the launchpad forever without a problem.

They'll build up heat all right. A one-minute burn will get them warm, going full-throttle for multiple minutes has the potential to overheat. Just how much of a problem it is depends on various factors, such as what you have the engine attached to (e.g. how much heat capacity it has). They can definitely explode, and if you like the red glow, have no fear, you'll be seeing plenty of it. The main thing is getting rid of it.

[cybersol]

You won't miss it as much as you think, because with 10 minute burns half the rocket will glow cherry red instead, especially at night. Best tip is to attach the nukes directly to their own largish tanks to use their high thermal mass. If you like low TWR with long burns, additionally adding parts that radiate heat could also be useful (wing C works well).

[XOIIO]

Yeah they used to heat up instantly in the atmosphere though, whereas now they don;t, must be the heat model. It sucks that they have changed this though and that you need to have them on their own tanks, I used to do 3 on an orange tank as a pretty nice setup for interplanetary missions.

At least now you don't need oxidizer.

[cybersol]

Yeah, but not using oxidizer is also a stealth reduction in effectiveness unless you switch to Mk2 or Mk3 liquid fuel only tanks, which have a better dry mass ratio that normal tanks with no oxidizer. The reduction comes because the engines still use the same mass of total fuel per second, but now it all is LF instead of LF/Ox.

[RuBisCO]

1. Jet fuel tanks bleed heat.

2. Air brakes in space look like radiators and are at least good in aerobraking.

[Red Iron Crown]

I wrote a little post about managing LV-N heat here, it is certainly manageable if you design with heat absorption and flow in mind.

[Sharpy]

Instead of running it at full throttle, put it at some 4 notches up, fine-tune with engine thrust limiter (right-click the engine), crank up phys-wrap to 4x (alt+.), and it will not overheat. Sure most maneuvers will leave you with enough time to go for a lunch (and interplanetary burns - to watch a movie after the lunch) but it works, and it works fine. 5000 dV in two hours real time (8h game time) - quite doable.

[RuBisCO]

This nuclear tug I can run at full throttle until it is at ~80% empty.

Edited June 12, 2015 by RuBisCO