LV-N Engine Fuel Consumption Seems Too High

[ThomJ]

Just curious about the fuel flow for the LV-N in KSP 1.0. It seems abnormally high at 1.53 units of LF/second. I understand that the oxidizer requirement was removed and that the part needs to be balanced for that, but really? Between the increased mass of the engine and the overheating, there is almost no benefit to using this engine when compared to the LV-909 "Terrier" which has only a slightly higher fuel burn (1.60 units/second), a SIGNIFICANTLY lower mass (0.5 compared to the 3.0 of the LV-N), is cheaper to purchase, and doesn't have to deal with overheating. Am I the only one experiencing this? Is this a bug, or intended behavior?

I also performed the "rocket equation" found here (http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) for a small test ship and figured I would have about 5.4km/s of delta-v. In testing, I only got about 3.0km/s out of it.

KSP 1.0.0 for Steam

No mods

[TinfoilChef]

I've noticed that once the LV-N begins to overheat it's thrust drops drastically and doesn't return to 60KN until it cools off, could this be affecting the dv you get from it?

[ThomJ]

I haven't noticed any loss in thrust due to to overheating, at least not with the test ship.

[sal_vager]

The LF use is doubled from .90 as they don't draw O anymore, you still need the same mass through the engine

[ThomJ]

The LF use is doubled from .90 as they don't draw O anymore, you still need the same mass through the engine

I guess that makes sense, but it still doesn't explain why my delta-v calculations were way off. Maybe i'm just bad at math? Either way, I guess if it's intended then i'll just have to learn to deal with it.

[paelleon]

Even I noticed that the LV-N ISP rating, shown in the part description, is not right. I have much lower Dv with my test ships using them, infact I'm using the LV-909 too.

[ThomJ]

I've done a lot of testing with the LV-N and it turns out it's not as bad as I originally thought, as long as you only use it on large ships that can absorb the heat. The benefits of not having to carry the oxidizer on an already 40+ ton interplanetary drive are also pretty significant and I found that in the post above, my math was indeed off and the Dv you get is roughly the same as pre 1.0. I've only built a couple small IP drives and I was able to send a medium sized station to Gilly (and had I not gone the wrong way around Eve I could have brought it back). So to sum up, LV-N's are still good for interplanetary travel, but only interplanetary travel (assuming the heat is dissipated properly). But if you're within the Kerbin system or sending out small probes from a larger ship (to some of Jool's moons for example), I would definitely agree that the terrier is the way to go.