LV-N Atomic Motors on Spaceplanes?

[MessyMix]

Hi guys!

I've recently started playing again (since 0.90 Beta); I stopped for a while from version 0.24 because of life. Now, when I check out some videos on Youtube I find that many people are now using the LV-N engine on their crafts, even though a) it's pretty damn heavy thrust isn't high therefore c) low TWR. The only positive I can think of is the high efficiency, but otherwise, why are many people using LV-N's on their spacecrafts? (Apologies for the noob question!)

P.S. I find that the KSP community has the absolute best community ever!!

Thanks guys!

~Messy

Edited May 13, 2015 by MessyMix

[andruszkow]

Apart from the Ion engine, the LV-N has the highest vacuum ISP in the game, which makes it good for interplanetary roundabouts.

I don't think there's much more to it than that.

[cybersol]

Due to being heavy but efficient, their real niche is long interplanetary stages. I typically build reusable LV-N tugs to haul things around between planets. One or more tugs docks to the payload and pushes/pulls it around the Kerbol system.

[KerbMav]

Hyperdrive-Docking-Tugs ... or what were they called?

http://forum.kerbalspaceprogram.com/threads/42925-Gentlemen-s-Naval-Battle-Club%28Attention-moderators%29?p=1024612&viewfull=1#post1024612

[Kuzzter]

I used LV-N in previous versions because I could refuel in LKO and go anywhere. I like them even more now, as the turboramjet+nuclear combo uses only liquid fuel so no need to carry oxidant.

[Sean Mirrsen]

A different benefit of the new LV-N is that it uses LiquidFuel only, the same as the regular air-breathing jet engines. This theoretically allows you to have an SSTO spaceplane that only uses, and has the tankage for, one type of fuel. With a refueling station in orbit, such a design could theoretically go pretty far, compared to a conventional rocket-powered craft that would need to carry extra mass in now-useless oxidizer.

The catch, of course, being that a turbojet/nuclear SSTO is hilariously inefficient when it comes to getting to orbit.

edit: and ninja'd.

[MessyMix]

Thanks for all your replies guys! Didn't realize it's now liquidfuel only xD

Side question(s): Because a turbojet/nuclear is so inefficient at getting into orbit, what do you guys suggest in it's place? What setup would you use to get to Mun? Mimmus? Other planetary systems? Obviously I see that as distance goes up, the importance / positive aspects of using a LV-N increase exponentially.

Thanks once again!

[KerikBalm]

Rapier + LV-N, only carry the minimum amount of oxidizer needed to get to orbit (and maybe a little for the Mun, the LV-N is certainly enough for landing on Minmus)

[MarvinKitFox]

Obviously I see that as distance goes up, the importance / positive aspects of using a LV-N increase exponentially.

Remember of course that Distance is irrelevant, only needed Delta-v is.

For example, The surface of MoHo is quite a bit further than the surface of Eeloo.

And a low solar orbit is **dozens** of times further still!

[Geschosskopf]

LV-N's also got a ridiculous, unrealistic, and fundamentally broken overheating mechanism in 1.x, which basically prevents them from making long burns without themselves or whatever they're attached to blow up. To work around this, you have 2 options. The preferred method, especially for spaceplanes, is self-help modding via ModuleManager, to make the heat essentially the non-issue it should really be. The other alternative is to only attach LV-Ns to really huge friggin' tanks that can absorb the silly, unrealistic, and fundamentally broken overheat without exploding. This, however, isn't really an option for spaceplanes.

[Sean Mirrsen]

LV-N's also got a ridiculous, unrealistic, and fundamentally broken overheating mechanism in 1.x, which basically prevents them from making long burns without themselves or whatever they're attached to blow up. To work around this, you have 2 options. The preferred method, especially for spaceplanes, is self-help modding via ModuleManager, to make the heat essentially the non-issue it should really be. The other alternative is to only attach LV-Ns to really huge friggin' tanks that can absorb the silly, unrealistic, and fundamentally broken overheat without exploding. This, however, isn't really an option for spaceplanes.

Uh.

This is from a hypersonic egress through the atmosphere, and burning for six minutes straight with two LV-Ns at full throttle. No alterations or hacks. Barely past orange, nowhere near overheat temperatures. You just need proper design.

(On that note, can we have some Mk2 nosecones without oxidizer storage? The extra line in the resources bar is annoying me, it's never meant to be filled on this design.)

Edited May 13, 2015 by Sean Mirrsen

[Kuzzter]

This is from a hypersonic egress through the atmosphere, and burning for six minutes straight with two LV-Ns at full throttle. No alterations or hacks. Barely past orange, nowhere near overheat temperatures. You just need proper design.

(On that note, can we have some Mk2 nosecones without oxidizer storage? The extra line in the resources bar is annoying me, it's never meant to be filled on this design.)

Seconded, my turbonuke SSTO works just great thank you. I find a 28t ship with 2 nukes and 3 jets works perfectly. I have gotten it into orbit with 1900 m/s dV remaining.

@Sean Mirrsen, I have edited my own Mk2 parts to have no oxidizer. It's not hard to do. Just make a new subfolder under GameData (mine is called 'LiqFuelParts') and copy over the relevant files from the Squad parts folder. For example to make a liq fuel only Mk2 bicoupler you need bicoupler.cfg. bicoupler.mu and mk2adapters1m.dds.

Then edit the .cfg file as follows, deleting the Oxidant section and adding units of liquid fuel to compensate. My edits in red.

PART

{

name = mk2_1m_LFBicoupler

module = Part

author = Kuzzter

rescaleFactor = 1

node_stack_top = 0.0, 0.9375, 0.0, 0.0, 1.0, 0.0

node_stack_bottom01 = 0.625, -0.9375, 0.0, 0.0, -1.0, 0.0

node_stack_bottom02 = -0.625, -0.9375, 0.0, 0.0, -1.0, 0.0

node_attach = 0.0, 0.0, 0.7, 0.0, 0.0, -1.0, 1

TechRequired = advAerodynamics

entryCost = 19800

cost = 860

category = Propulsion

subcategory = 0

title = Mk2 LF Bicoupler

manufacturer = KuzzCo Engineering

description = One engine is not enough? Don't need oxidant? We got you covered!

attachRules = 1,1,1,1,0

stackSymmetry = 1

mass = 0.29

dragModelType = default

maximum_drag = 0.2

minimum_drag = 0.3

angularDrag = 2

crashTolerance = 50

breakingForce = 50

breakingTorque = 50

maxTemp = 2000 // = 3000

fuelCrossFeed = True

NoCrossFeedNodeKey = bottom

bulkheadProfiles = size1, srf, mk2

MODEL

{

model = Squad/Parts/FuelTank/mk2Adapters/bicoupler

}

MODULE

{

name = ModuleLiftingSurface

useInternalDragModel = False

deflectionLiftCoeff = 0.3

dragAtMaxAoA = 0.2

dragAtMinAoA = 0.1

}

RESOURCE

{

name = LiquidFuel

amount = 400

maxAmount = 400

}

}

...and save. Note that the filenames stay the same, the part will be a unique part because it is in a different folder from the Squad parts folder. When you load the game next, the new part will look exactly like the LFO bicoupler but the name and descriptions will change. Do this for any other parts you like.

Edited May 13, 2015 by Kuzzter
Had wrong fuel amount in sample .cfg

[Red Iron Crown]

^^ You don't even need another folder, just change the name of the cfg and leave it in the same place. The stock Mk2 and Mk3 tanks that come in LF and LFO tanks work this way.

[Kuzzter]

^^ You don't even need another folder, just change the name of the cfg and leave it in the same place. The stock Mk2 and Mk3 tanks that come in LF and LFO tanks work this way.

Yes, thanks Red you're right of course. I suppose I just like leaving the stock Squad folders as they are, I'm afraid to muck around too much in there

[Temeter]

You could also go for the modular fuel tank mod, that should be the easiest way to do it:

http://forum.kerbalspaceprogram.com/threads/64117

[Alshain]

I've certainly attempted such a thing, but in the end for practicality LV-N on a plane makes no sense at all. A plane has wings and jet engines to get it through the atmosphere, those wings and engines have mass. You are better off having an interplanetary transport launched by a rocket that sits in orbit and use the space plane to get to it than hauling all the mass of wings to other planets. Unless, you are going to Laythe.