LV-N and why

[Monkeh]

It's already been said but just to re-iterate:

The nuclear engines are heavier but twice as efficient. This means, roughly, you need half as much fuel to go anywhere with the nukes than with conventional rockets. The extra weight in the engine is, normally, countered by having to take A LOT less fuel with you. This all depends on the size of your crafts. If they are small then screw the nukes and use others, but for larger craft they are the bomb.

I use the Kerbal engineer which shows how much delta v your rocket has as it flies. If i have built in a nice nuke interplanetary stage then as the rocket goes through the first stages, burning millions of fuels, you still see the total delta v going up due to the atmosphere thinning out and the nukes getting ever more efficient when they start to burn.

So the rocket starts with, say 10,000 m/s delta v and as we reach the edge of the atmosphere after burning for a few minutes, we have 11,000 m/s left.

They are the best at the long, slow burn with ridiculous efficiency.

[Djolox]

Use it on interplanetary missions because of efficiency and Isp

[Monkeh]

*efficiency due to ISP (?)

[TheDarkStar]

It's already been said but just to re-iterate:

The nuclear engines are heavier but twice as efficient. This means, roughly, you need half as much fuel to go anywhere with the nukes than with conventional rockets. The extra weight in the engine is, normally, countered by having to take A LOT less fuel with you. This all depends on the size of your crafts. If they are small then screw the nukes and use others, but for larger craft they are the bomb.

I use the Kerbal engineer which shows how much delta v your rocket has as it flies. If i have built in a nice nuke interplanetary stage then as the rocket goes through the first stages, burning millions of fuels, you still see the total delta v going up due to the atmosphere thinning out and the nukes getting ever more efficient when they start to burn.

So the rocket starts with, say 10,000 m/s delta v and as we reach the edge of the atmosphere after burning for a few minutes, we have 11,000 m/s left.

They are the best at the long, slow burn with ridiculous efficiency.

Note that LV-Ns become the most efficient engines somewhere around 1800m.

[capi3101]

I have set up a formula to compare engine efficiencies before (in that case, it was a question of at what point the 48-7S became more efficient than the LV-909) and I've gone ahead and applied the necessary data for comparison (mass of the engines and their respective vacuum Isps) to the same formula to try and figure out where the "tipping point" is (i.e. the deadmass - anything other than fuel tank or engine - at which point, regardless of the amount of fuel involved, the heavier engine is more efficient). The idea is to see how much delta-V the heavier engine generates given the same payload and same amount of fuel and then to see how much fuel is required by the lighter engine to produce the same amount of delta-V. If the lighter engine requires less fuel, it's more efficient; if it requires more, the heavier engine is more efficient.

The tipping point in the case of LV-909-vs-LV-N is 0.87065 tonnes, so if you're pushing anything heavier than that, you're generally better off with the nuke.

[Skorpychan]

I use the nuke for orbital maneuvering, but it's WAY too heavy and low thrust for my tastes in landers. I prefer them to have a nice high TWR in case I start the burn too late, and to be able to decelerate nice and efficiently at half throttle in case I need to abort.

[Anton P. Nym]

I use LV-Ns for almost all my interplanetary stages; the fuel mass generally drowns out the higher mass of the engine in those cases. Only with sub-ton probes do I switch to the LV-909 or the wee Rockomax engines.

I also use LV-Ns for my persistant Munar shuttles that take cargos & crews to the moons and back; they've made about a dozen trips each thanks to refuelling missions.

-- Steve

[Monkeh]

Here's me going all over Minmus with a single nuke and loads of science stuffs.

I landed and took off four times and still had over 5,000 m/s left in the tanks. I could have gone to Jool and back as well, probably twice, but it was late and I was tired, so I came home and got over a thousand science for my second trip to Minmus. This is why LV-N's are 'Da bomb!'

[Skorpychan]

That's not that much science for Minimus. I got like 1400 the other day with one lander and jetpacking someone around to get samples from biomes.

Mostly jetpacking, anyway. Ran out of fuel too early, and had to walk 6KM back to the lander. Even on x4 physics warp, I had to wedge 'W' down and sit there with a book supervising it.

[lajoswinkler]

That's not that much science for Minimus. I got like 1400 the other day with one lander and jetpacking someone around to get samples from biomes.

Mostly jetpacking, anyway. Ran out of fuel too early, and had to walk 6KM back to the lander. Even on x4 physics warp, I had to wedge 'W' down and sit there with a book supervising it.

How do you wedge your keys?

[StuLong]

How do you wedge your keys?

Six sided die and a suitable stable weight on top.

[Skorpychan]

Six sided die and a suitable stable weight on top.

This. A handy piece of plastic laying around, and my phone.

[vetrox]

I hevent used the nukes in a while. Probably becuase I have only been to duna (although my dres mission hasnt got any nukes on it)

I plan my dv accordingly and i prioritise twr over excess dv. I'm too impatient to do all those burn times.

On a side note I would like to point out that the LV-N's are quite long. On some of my craft they just owuld take up too much space or look wierd. I have a vacuum shuttle-tug. I have one with an lv-n and one with 909's and the one with 909's is just a better shape for what I was after and tugs smaller stuff around with ease. (took my kerbin space station from kerbin to the mun then took it to minmus. Maybe it just has centemental value that makes me prefer it.)

[maccollo]

LV-N will almost always give you more delta V than any other engine for the same stage mass.

The only times when this is not the case is when the mass fraction is significantly improved by using a different engine, and by different engine I mean the rockomax 48-7S.

This happens when your rocket minus the engine weights 1.7 tons or less. At that point the 48-7S gives you more deltaV per unit of fuel.

[Seret]

Personally I build really small

For you the LV-N doesn't make sense then. Off the top of my head I think the point at which the LV-N becomes viable is about 7t. For everything above that it's the most efficient engine.

[Mmmmyum]

Yeah I've played around with RSS a bit too much now to build big. I find it makes my lower stages way too big, besides I almost never take more than 20t to orbit. Don't really see why I should bother with ungainly rockets