LV-N and why

[Mmmmyum]

I see on the forums that a majority of the people here use it for nearly everything. I just don't really understand why people think it's the best engine for interplanetary burns, as the rocket equation relies on mass, which the LV-N has a lot of.

Personally I build really small, and I've never really needed to use it. (I used it on the escape burn and orbital injection from Kerbin to Eeloo, that's all)

Why do you use it?

[SargeRho]

Isp of 800s.

[Superfluous J]

I use it because when I put it on most any rocket, the total dV of that rocket goes up. If it doesn't, I don't use it and instead use a different engine or set of engines that causes my dV to be highest.

[Skorpychan]

Isp of 800s.

That's why. Two of them are capable of hauling my interplanetary missions without much trouble, and without overheats.

One would be more efficient, but I'd have to push things instead of hauling them behind, and that would risk the whole thing folding in the middle and exploding.

If I cared to use longer outriggers, I could probably drag pretty much anything around without having to conform to Rockomax tank size plus a bit.

[RocketPilot573]

Even with the huge mass, the Isp of 800 is still better in most cases.

[Naten]

I find my Falcon Heavy rocket's half-empty Skipper-powered stage (~half an X200-32 tank, if that's the biggest silvery-gray 2.5m Rockomax tank's name) has enough dV to send itself into a Kerbol escape trajectory. (It was empty for testing.)

¯\_(ツ)_/¯

[7499275]

I don't use it, for 2m stages I use the poodle and for 1m stages I use that little lander engine I forget the name of it htough.

[MBobrik]

I see on the forums that a majority of the people here use it for nearly everything. I just don't really understand why people think it's the best engine for interplanetary burns, as the rocket equation relies on mass, which the LV-N has a lot of.

.

1. Pushing big stuff. If your Eve seashore lander/ascent vehicle got 160 ton, 2.5 ton per engine is negligible, however the more than 2x smaller fuel consumption is not. The same goes for landing at medium to low gravity (mostly) airless worlds like Duna or the Mun.

2. Loads of dV. Eeloo, Moho.

3. In case the gravity is low enough, Nuke gives your (big)skycrane much longer hover time. Or, if you do biome hopping, you can hop more times before refueling.

Edited January 5, 2014 by MBobrik

[Eric S]

As the 5thHorseman said, sometimes it gives the best delta-v results. Basically, the engine gives twice as much total thrust from the same amount of fuel as any of the stock engines except the ion engine, so if you're using any significant amount of fuel, the extra fuel mass you'd have to bring would be more than the extra mass of the engine. Now, if you design small focused probes, you're less likely to need the fuel amounts that would make the LV-N worth it.

Basically, as the mass of the craft increases, whether from payload or from fuel, the delta-v you get from an LV-N increases compared to the amount of delta-v you'd get from any other engine. This is more true in the case of the payload mass increasing than fuel mass, but it's still true in either case. Even the lightest stock pod, the OKTO2, on top of an FL-T800 fuel tank, gets more delta-V from an LV-N, despite it's extra mass, than it would from an LV-909 or a Rockomax 48-7S. Now, I'll admit that in the case of a probe that light, you'd be better off breaking it into separate stages or adding drop tanks from the delta-v point of view, but as your payload mass goes up, that gains less and less.

[TMS]

Why: http://forum.kerbalspaceprogram.com/threads/45155-Mass-optimal-engine-type-vs-delta-V-payload-and-min-TWR

[Sgt. Cookie]

In simple terms? It's the most efficient Liquid Fuel/Oxidizer engine. The thrust is low, yes, but you're going to be burning for a hell of a lot longer than other engines.

Here's a simple experiment you can do:

Grab the Kerbal X stock craft (Don't change anything, yet) and attempt to fly it to the Mun, difficult but doable. Success is not necessary here.

Whether you've succeeded or failed, replace the final engine for the LV-N and then fly to the Mun. Unless you're seriously inept, you'll get to the Mun with over half your tank still left.

[Lazro]

I think that for payloads over 9 tons, it's best used, but for 9 tons and under you're better off with the 48-7s.

[Alchemist]

The thing is heavy and low thrust, meaning that it isn't really better than normal rockets for landers or relatively low delta-V maneuvers. Nuclear powered lander can end up as heavy (or even heavier) as conventional (you might see real benefits if going for multiple landings with in-orbit refueling or hovering all around something like Minmus).

What it really excels at is... Have you tried building interplanetary ships with about 10 km/s or more delta-V for orbital maneuvers? (going to Moho and back or visiting moons of Jool) At this point you start with considering ISP firs and other weight reduction tricks only after. And here goes the trick with nuclear landers - using the same engines for cruise and landing!

Edited January 5, 2014 by Alchemist

[Mmmmyum]

I generally build to delta-v requirements. I also like using the lightest, smallest vehicles. That heavy LV-N makes your first stage quite a bit heavier (generally my stage to orbit in stock sizes, minus boosters of course)

[technion]

It is worth noting, a small tank and command module have a much better dv with an LN-909 or similar than an LV-N, due to the impact of that weight.

[6.forty]

It is worth noting, a small tank and command module have a much better dv with an LN-909 or similar than an LV-N, due to the impact of that weight.

Any time I consider the LV-N, I think "Is this the most appropriate tool for the job?" A wrecking ball can make easy work of demolishing a building, but it's not quite appropriate to tear down your backyard fence with one.

[Kasuha]

That thing below the rover doubles as my space program's universal lander and interplanetary engine. Weighing some 30 t it does not meet the 9 t per engine efficiency metric, but it still means I dont have to carry one set of engines to travel between planets and another set to land somewhere. And it definitely meets the metric when getting off.

Besides, KSP is a game. You don't need to be efficient all the time.

Edited January 6, 2014 by Kasuha

[TMS]

I wonder to what extent the introduction of finances to the game will influence the choice of this engine?

Presumably, it will be expensive as a means of balancing its efficiency?

[Superfluous J]

I wonder to what extent the introduction of finances to the game will influence the choice of this engine?

I'm hoping a lot. Anything that encourages us to dig deeper into our parts for a solution makes me happy.

Presumably, it will be expensive as a means of balancing its efficiency?

Presumably they both will. Or possibly the 48-7S will get a nerf and the LV-N's unique fuel will make it harder to just slap on any old design. Or both. Or all 4 of those things. Now I'm confusing myself. How about "all"?

[crazyewok]

I just like things that are nuclear

[lajoswinkler]

I used to use it for every mission, but now I'm using chemical engines to get to Mün, Minmus, Eve and Duna. I find that more realistic and challenging.

Of course, if I need to haul something heavy to the outer planetary bodies, I will resort to LV-N. I do wish there was a wide type of it so I wouldn't have to bother with struts.

[SRV Ron]

LV-N are best used for interplanetary burns. Otherwise, they are way too heavy for landers where the elimination of two tons per higher efficiently engine will be more then offset by the much lighter but less efficient LV-909 or the Rockomax 48-7.

[blizzy78]

I do wish there was a wide type of it so I wouldn't have to bother with struts.

KSPX does have one that has higher trust, but also weighs 5 t. But it's also wider.

[lajoswinkler]

KSPX does have one that has higher trust, but also weighs 5 t. But it's also wider.

I don't really like using mods. I had a few instances where they would mess with the game. Also I don't have a powerful computer.

But ok, I'll try. YOLO xD

[SRV Ron]

I do wish there was a wide type of it so I wouldn't have to bother with struts.

Nova Punch has two of the 2.5 meter size for your larger rocket needs. One is standard length, the other, listed as a fusion engine, is quite compact. They are, of course, proportionally more powerful and extremely heavy.