Is the LV-N broken?

[Argon]

I saw where it has overheating issues, limited it to 88.5%. Doesn't overheat, works fine when attached to a liquid fuel fuselage. *shrug* Poll should have a third option: Knows how to use it, works fine.

I think the problem is less of "don't know how to use it" and more of "small fast accelerating craft does not have the thermal mass to absorb the heat generated", so it is not a lack of knowledge.

-Argon

[Kerano]

The heat on the LV-N definitely needs toning down. Requiring part spam to reduce heating is not a solution, neither is limiting to 20% thrust on an already low-thrust engine.

The mass increase, liquid fuel requirement and bump further back in the tech tree already nerf the LV-N enough. The main purpose of the engine is supposed to be for long deep-space burns, and right now it can't be used in that way. It's no longer a reward to unlock at the end of the tech tree, it's just a source of endless frustration.

[Kerr_]

I always viewed the LV-N as a specialty engine, for interplanetary travel or moving large objects between moons.

[eevenson]

Or you build a craft that spreads heat:

http://i.imgur.com/wAV0Uhe.jpg

Not a single part included for extra radiation, and that's without using the cargo to further radiate heat. Full thrust, 0.32t/w with cargo and full tanks. Doesn't overheat.

How do you get this thermal view?

[Brotoro]

While heat pumps and radiators sound like lots of fun to play with...I think I'd prefer it if the heat generation of the nuclear engine was simply toned down (since Squad hasn't fixed the problems with running KSP under OSX...and as they have been adding more and more parts in recent versions, the problem has been getting worse and worse -- so I like the no-additional-parts solution).

Edited April 30, 2015 by Brotoro

[Sean Mirrsen]

Indeed, the LV-N was never intended for small craft. It's got terrible TWR and high mass, it was always intended for moving large ships around, those that can take the heat produced by it.

If you want to move small ships somewhere, use a 909. Or ions.

[Guest]

How do you get this thermal view?

You can do it through the debug menu, or by visiting the link in my sig and getting a little mod.

[Renegrade]

A fair point as well, but they could have just nerfed atmo ISP not vacuum.

That wouldn't do it - most of the launch is spent at vacuum or near-vacuum conditions. Blanket nerfs are pretty much required. Besides, the system was rather small and trivial even on pure-chem flights.

Anyhow, if anything, I'd like to see heat management become a thing for other engines too.

[Geschosskopf]

Or you build a craft that spreads heat:

http://i.imgur.com/wAV0Uhe.jpg

Actually, this pic shows how messed up the heat system is in KSP. That central tank being bathed in fire along both sides should be exploding instantly. Tractor/puller spaceships are totally unrealistic and should not work. That to me is a bigger problem than the LV-Ns overheating from use.

In real life, heat transfers in 3 ways: convection, conduction, and radiation. While KSP now claims to handle all 3 of these, it really doesn't, as your pic makes quite clear. There should be an immense amount of radiant heat coming from those flames and impinging on the side of the central tank.

[Temeter]

How do you get this thermal view?

AltF12 for debug menu, physics>heat, there heat saturation and context menu options.

Or even better, get the thermal helper, which creates a button in the stock toolbar.

http://forum.kerbalspaceprogram.com/threads/117893-1-0-regex-s-Useful-Mod-Emporium

Actually, this pic shows how messed up the heat system is in KSP.

It's a single feature missing. Exhaust heat radiation. KSP is a game, not a simulation.

[Frank_G]

It is ok, IF we get a nice set of foldable radiators soon. Otherwise i agree, that the Nerv is not really usable at its maximum potential, which is a pain for large scale interplanetary missions.

[Wolf Baginski]

Somebody is complaining about not being able to use a nuclear rocket in-atmosphere?

[LadyAthena]

I see alot of complaining about small craft blowing up with nuclear engines, and then in the same sentance the words "unrealistic".....

....

..

.

Put a nuclear engine on a Cessna, and see what happens... Without a proper and extremely heavy heat sink and or massive coolant accessory your engine isn't gonig to run very long.

Sure this has made space planes rather difficult and not something worth building to much, but that is a whole different problem. New parts for space planes need to be added with better engines to help them.

There's a reason why even in today's world you only see Nuclear powered anything on the water, with a sufficient, and steady mass supply of cold water to control the heat, and why most if not all Nuclear power plants are built near a mass supply of water.

The heat system in the game is just fine. The nuclear engines are just fine. They are NOT supposed to be used for small craft. THAT is unrealistic. What they need to do is make new parts to incorporate this new mechanic of heat, heat sinks of varying sizes and new engines for space planes that don't require nuclear engines earlier in the tech tree.

Oh also Tip: If you're complaining about not being able to use Nuclear Engines in the atmosphere you're doing something horribly wrong to begin with.

[Armchair Rocket Scientist]

"The NERVA is realistic guys, just place wing parts all over it to radiate the heat" - This is saying that the part is realistic, you just need to make unrealistic modifications to make it work. Wings are not realistically meant to radiate heat, and they are not a solution for this if you want to aim for realism. Give us some radiator parts to deal with the heat.

People saying "Just add a whole bunch of radiators" may be my new pet peeve. Not all of us are running the game on a supercomputer; if your computer can handle 200 parts without becoming a slideshow, having to use fifty of them on radiators just to make two engines operate at full throttle is utterly ridiculous, and I would consider it game-breaking.

[Laie]

Put a nuclear engine on a Cessna, and see what happens... Without a proper and extremely heavy heat sink and or massive coolant accessory your engine isn't gonig to run very long.

Nonsense. Gameplay-wise, if you want to limit it to bigger craft, make it bigger and heavier. Like 20 tons, 800 thrust. But don't require people to spam a dozen parts in a game where part count matters so much.

Realism-wise, the heat is not supposed to go into the craft, but into the propellant (and thus vanish into space). The hotter the exhaust, the better the ISP, so you want to run it as hot as possible. What's possible is determined by available materials. A good design grows just as hot as it's materials allow.

[Guest]

Actually, this pic shows how messed up the heat system is in KSP. That central tank being bathed in fire along both sides should be exploding instantly.

Instantly is pretty much too soon, it would probably take a good couple of seconds or more. Anyway, that's hardly an issue because you could pretty easily build that as a pusher with the same heating results.

There should be an immense amount of radiant heat coming from those flames and impinging on the side of the central tank.

This is true. Not sure how to handle it programmatically, though. You could raycast I suppose but, as ferram4 showed way back when, doing too many raycasts would cause lag. Calculating part locations would probably be even slower than raycasts, but I don't know too much about that. A spherical hitbox, maybe? I think it's a tough problem to solve, which is probably why you don't see radiative heat from exhaust (well, maybe if the part were immediately behind it?)

There's a reason why even in today's world you only see Nuclear powered anything on the water, with a sufficient, and steady mass supply of cold water to control the heat, and why most if not all Nuclear power plants are built near a mass supply of water.

A solid-core NTR is much the same as a conventional nuclear reactor, but your reaction mass is basically the coolant. By all accounts, you should need to cool the craft/engine when the engine isn't firing. Of course, if you're encasing your NTR within an aerodynamic frame to get it into orbit (which you'd probably need), you would have to handle the radiative heat from the engine while it was firing.

People saying "Just add a whole bunch of radiators" may be my new pet peeve. Not all of us are running the game on a supercomputer; if your computer can handle 200 parts without becoming a slideshow, having to use fifty of them on radiators just to make two engines operate at full throttle is utterly ridiculous, and I would consider it game-breaking.

I feel the same way when someone claims I'm "uncreative" for wanting procedural parts in the game. Also, the tug I showcased in another thread comes to @130 parts with lander, of which 40 are radiator parts (10 per engine). If I used bigger wing parts I could probably bring that down to 20 (5 per engine)? Not sure. Wing radiators aren't the only solution: bigger fuel tanks, more mass, less engines, will all help manage the heat. Bigger thermal mass is one of the reasons my tug can manage four LV-Ns at the same time. I could potentially cut the radiator count down some by simply adding another fuel tank, how cool is that?

[Redshift OTF]

Ha! Yeah, build a ship that spreads the heat. That's a wee bit difficult when you're putting them on space planes. Your options a far more limited.

I agree. This is another example of creativity being stifled because the use of a major component in the game has been narrowed.

[Mister Kerman]

I think "wing-radiators" are a terrible necessity for dealing with heat issues caused by the LV-N's new characteristics. I like to be creative, not clever. This part is important for interplanetary space exploration. I won't complain that the game should change to suit the way I play the game in particular, but I'm not happy about making ridiculous workarounds in order to make something basic like an engine work.

I'll try my best to deal with this new engineering hurdle. I just wish there was something less silly like a single part designed to deal with it in a sensible/realistic fashion, like a radiator.

[Sean Mirrsen]

You're free to use the cheat menu to ignore heating, by the way.

I think it's a nice technical challenge. Getting anywhere you want should not be easy just because you have what amounts to cutting-edge modern-day technology.

Edited April 30, 2015 by Sean Mirrsen

[Guest]

Also, there's a 1.0.1 update coming at some point. We may see the LV-N's heat production brought down, who knows?

[Temeter]

I agree. This is another example of creativity being stifled because the use of a major component in the game has been narrowed.

You mean narrow in the terms of having only a single viable long range engine that completely outperforms every single other engine in the game and does not have a single downside?

[Frozen_Heart]

You mean narrow in the terms of having only a single viable long range engine that completely outperforms every single other engine in the game and does not have a single downside?

Its downside is its huge weight, low thrust. very high cost, and position right at the end of the tech tree.

They may as well have not added the overheat and maxed the thrust at 20.

[Sean Mirrsen]

Its downside is its huge weight, low thrust. very high cost, and position right at the end of the tech tree.

They may as well have not added the overheat and maxed the thrust at 20.

"Huge weight and low thrust" can be summed up as "Low TWR". Its low TWR is balanced by its spectacular fuel efficiency. Also by it not using oxidizer, theoretically making pure LF/Mono SSTO spaceplanes possible. Highly theoretically, of course. I haven't been able to make one so far.

It's an interplanetary transfer engine for large ships now. Pretty much as it should be. It might be running a little too hot at the moment, but it's nowhere near so dramatic as to call it "broken".

[Temeter]

Its downside is its huge weight, low thrust. very high cost, and position right at the end of the tech tree.

They may as well have not added the overheat and maxed the thrust at 20.

That would just make it painful to use. There is rarely ever a reason not to use nukes, long burns aren't a problem in space outside of timed precision maneuvers (whenever they happen). Even a duna lander often gets more than 700ISP at ground level. Btw, on duna the engines also would be much better cooled thanks to the atmosphere, too.

And it still is a pretty damn good engine. You just need to take care and check out how long you can burn a single time and everything is good. The heat is very well managable, no clue why people are pretending this would be the end of world. I only can assume that most complainers didn't even try to actually deal with the heat.

Edited April 30, 2015 by Temeter

[Geschosskopf]

It's a single feature missing. Exhaust heat radiation. KSP is a game, not a simulation.

Hmmm, do we agree that the old aerodynamic drag model was fundamentally flawed due to being based on mass? OK, so the heat model is fundamentally flawed because it doesn't take actual radiant heat into account at all and goes overboard on conduction. Convection, meh, that only happens in atmospheres and ships spend most of their time in vacuum, so it isn't that big a deal.

Maybe I take this a bit personally because I'm a firefighter so my life revolves around the mechanics of heat transfer. But in real life, radiation is by far the most important way heat moves from 1 thing to another. It's how we cook our meals, it's why fires keep us warm, and it's the driving factor in burning down houses. Radiant heat is where most of the energy goes and it moves line-of-sight at the speed of light. Conduction, OTOH, is a comparatively slow, weak process that depends on the thermal conductivity of the material the heat is trying to move through. So having parts explode from conducted heat while ignoring the effects of radiant heat is just blatantly wrong.