Scott Manley weighed in on the Nuke discussion - what do you think?

[ShadowZone]

I stand by my previous statements. It is irrelevant what is possible in the game, only what is realistic. It is unrealistic to use the LF-only tanks with the LV-N, as the fuel density is far too high. That is the only necessary factor to make me consider it to be cheating to use them with it. It is a hack by the game, to avoid introducing another fuel type, and is quite clearly balance around using LF+O tanks with the O part empty. I don't need the devs to handcuff me in choices, I'm quite capable of recognising that it's very unrealistic to use the LF-only tanks with the LV-N, now that I have reviewed the evidence.

We absolutely do not need more LF-only tank options, as they would push the LV-N towards being overpowered. It is just fine as-is, used with LF+O tanks. There is no problem to solve, it is not broken, nothing needs urgently fixed.

Squad, please DO NOT give us any new LF-only tanks for the LV-N, they are not in any way needed.

I am sorry, but I cannot let the "unrealistic" argument count. Squad themselves have very clearly stated that KSP is a game first and not a simulator. And if a game allows certain options stock then it is by definition not cheating. If you don't want to play that way because it doesn't fit your playstyle, please go on and do that. I'll be over here slapping LF tanks on my LV-N vehicles

Why don't we need more LF tank options? Jets and spaceplanes could use the variaty of LF only adapter parts.

Regarding fuel density: both LF and O are 5kg per "unit" and only have different amounts because engines need more O than LF so tanks can drain evenly. Now that's something I regard as highly unrealistic. Real life RP-1 has 0.81 g/cm³ while LO2 has 1.41 g/cm3. But I don't worry about this, cause I just want stuff to fly into space and look awesome

[Gkirmathal]

I am more concerned with the NERVA engines overheating when it's not supposed to because you have cryogenic fuel cooling the reactor down in the first place. The engine is only supposed to overheat when you run out of fuel to cool down the unit.

Agreed, but most to none here, will or want to recognise that it is currently flawed. So spare your troubles on the issue, it is like talking to a wall

[GoSlash27]

I agree with Levelord.

LV-Ns are not unfairly nerfed at all. They have an optimal range of DV, acceleration, and payload where they are the best engine to use. Attempting to use them outside of this range makes them less efficient than other engines and that's exactly how it should be.

The more troubling problem is the heat management issue. KSP doesn't have dedicated heat exchangers like we have IRL and an LV-N shouldn't be overheating anyway so long as it has fuel.

I do hope it gets fixed, because I don't use LV-Ns even when they're the best engine for the job due to this issue.

Best,

-Slashy

[TheMoonRover]

Remember, Squad has always said KSP is a game first, a simulator second. From a game perspective, the Nuclear Engine was ridiculously OP. It used the same fuel type as any other rocket engine, but with more than double the ISP, making it the go to engine for anything except take-off and landing on medium to large planets/moons, and small probes where the 48-7S gave more delta-v and the ion engine had a manageable TWR. Overheating was rarely a major issue, and could easily be worked around.

By making it use only liquid fuel, it puts the engine in its own category, and means it needs a different approach to use, which for some reason people seem to have been failing to adjust to. The engine is much more balanced now because of this, although I would argue it has not been nerfed; it has simply changed. Yes, the mass has increased, but in the long run it doesn't make a huge amount of difference.

Using the LF-only over LF+O tanks is not cheating because the game allows it, and it is neither OP enough or sufficiently niche/edge-case to really be classified as an exploit (from a game perspective, unless you count keeping part counts down so the Physics runs more smoothly. In an accurate simulator, yes, of course it is exploitative, but remember that KSP is primarily a game; if you want realism that's what realism mods are for.)

I admit the heating may be flawed, but it's easily work-round-able without going out of your way, at least from Kerbin outwards. (I have yet to visit Eve and Moho in 1.0, but suspect that a Moho capture would be the only thing which causes a major issue, as it should be IMO.)

So basically I agree with Scott Manley in that "The Nerva hasn't been nerfed, you're just using it wrong."

[Torquemadus]

I've always regarded the fuel in KSP to be an abstraction that represents the variety of different fuel types that the different engines in the game would use. The LV-N stretches this abstraction somewhat, but that's the price we pay for simplification.

One possible compromise would be to introduce some "cryogenic" versions of the existing fuel tanks. The description for these tanks could say that they have been specially designed for use with the LV-N, and contain extra insulation to keep the fuel contained therein at the required temperature. These tanks would contain liquid fuel only, but would be given a somewhat lower capacity compared to aviation fuel tanks. The tanks could then be marked with suitable labels warning of the cryogenic hazard posed by the fuel.

[Dodgey]

Aside from the heating issue I don't see a problem with them at all. As has been said when used in the correct circumstances they still are better than other engines but aren't a be all end all engine anymore.

[Miro Beero]

You should be able to pick any fuel tank and you can store X amount of units into it.

You should be able to choose what the ratio of X units is. Thus every part becomes usable for everything you want to build.

Why build more parts? - just fix the parts you have to be multi-purpose.

[Mister Spock]

Does Scott Manley ever post here?

[enroger]

I edited the cfg file of LV-N to use liquid hydrogen (Using Cryogenic Engine mod by Nertea you can switch tank type from LF/Ox to LH2). Yup it turns out LH2 has such an abysmally low density that the tank's dry mass actually weight more than LH2 they store. It would be more realistic that way, but also a huge engineering challenge to get LV-N to do anything, people can stop bitching about LV-N already, squad actually made it easy for us if anything....

[GoSlash27]

I edited the cfg file of LV-N to use liquid hydrogen (Using Cryogenic Engine mod by Nertea you can switch tank type from LF/Ox to LH2). Yup it turns out LH2 has such an abysmally low density that the tank's dry mass actually weight more than LH2 they store. It would be more realistic that way, but also a huge engineering challenge to get LV-N to do anything, people can stop bitching about LV-N already, squad actually made it easy for us if anything....

^ This too. The problem with powering the LV-N with LH2 is that it's useful envelope winds up outside the boundaries of anything you'd ever need to do in KSP. Pushing large-ish payloads beyond Duna at low acceleration is a good job for the LV-N as it sits. Anything else isn't a good job for it and shouldn't be.

Best,

-Slashy

[enroger]

^ This too. The problem with powering the LV-N with LH2 is that it's useful envelope winds up outside the boundaries of anything you'd ever need to do in KSP. Pushing large-ish payloads beyond Duna at low acceleration is a good job for the LV-N as it sits. Anything else isn't a good job for it and shouldn't be.

Best,

-Slashy

Goes without saying I switch it back to LF immediately, screw reality!

[Brotoro]

...In reality, the LV-N can't actually run on KSP's LF it has to use LH...

No...you are wrong. There have been studies to use nuclear thermal rocket engines with other propellants besides liquid hydrogen (methane, carbon dioxide, water, etc.).

...You can cheat and use plane tanks...

Well, it's a good thing we have people like you around to let us know what combinations of engines and tanks are cheating in our single-player sandbox game.

[Vorg]

Some mods have multi function containers. In the VAB, you right click the part to set which type of container it is. Seems like a simple fix that keeps part count down while expanding LF/LFO to all tanks. Biggest thing I don't like is that now jets now take fuel from all tanks at the same time even across seperatrons. Infact that is really the only control you have in that they pull from the other side of them first. It's a real pain with mixed engine craft, esp before you unlock fuel lines to give rockets back the fuel stolen by the jets. We need a better fuel routing control.

[Superfluous J]

The last thing we need is to double, triple, or quadruple the number of tanks available. The way it is now is a pretty decent compromise that doesn't add any extra tanks.

[Screeno]

You know what, I think the only thing it needs is its gimbal back! IRL all engines have gimbal, NERVA did! Also it could do with a teeny bit more thrust, perhaps 65 Kn?

[enroger]

Some mods have multi function containers. In the VAB, you right click the part to set which type of container it is. Seems like a simple fix that keeps part count down while expanding LF/LFO to all tanks. Biggest thing I don't like is that now jets now take fuel from all tanks at the same time even across seperatrons. Infact that is really the only control you have in that they pull from the other side of them first. It's a real pain with mixed engine craft, esp before you unlock fuel lines to give rockets back the fuel stolen by the jets. We need a better fuel routing control.

Goodspeed Fuel pump mod does it for you: http://forum.kerbalspaceprogram.com/threads/118176

[magnemoe]

We really only need a few 2.5 meter tanks, 2.5 is important as its the standard for most larger utility parts.

The Mk3 parts is perfect for larger ships.

[Archgeek]

You know, I can't help but notice that the thrust is still 60kN, and the fuel flow unchanged from the old vacuum minimum of 1.53/s. As a result it goes through an LF-O tank in the same time it used to go through an LF+O tank. If anything, that's a buff, since we don't have to take that oxidizer upstairs! It's tempered by the extra .75 tonnes of engine we have now, but it still severely undermines people's standing.

What's worse, if you're taking spaceplane parts up for dedicated nukeage, you're looking at let's say 2 mk1 fuselages over an FL-T800 tank, getting 300 LF with a dry mass of .3 for the fuselages, over 360 with a .5 dry mass for the FL-T800. Or if you're cool, you use mk2 short tanks instead, getting 400 LF with a .29 dry mass, beating the FL-T800 for both fuel and mass. I guess persons are complaining that they cannot abuse that as much as they'd like?

[Brotoro]

...If anything, that's a buff, since we don't have to take that oxidizer upstairs! It's tempered by the extra .75 tonnes of engine we have now, but it still severely undermines people's standing.

No. It's not a "buff" to not carry the oxidizer in the tank. With only the liquid fuel, you have less propellant in the tank. You get much less delta-V from the tank.

[Wjolcz]

I seriously hope there won't be more parts and instead we will get a tweakable to turn LF/O tanks into LF-only ones. That way the LF-only mk2 and mk3 spaceplane parts wouldn't be needed anymore and maybe some RAM would be freed.

[Tiaga]

Aside from the heating issue I don't see a problem with them at all

I agree completely. Nuclear engines were not fun pre-1.0. Now they are less fun.

[Archgeek]

No. It's not a "buff" to not carry the oxidizer in the tank. With only the liquid fuel, you have less propellant in the tank. You get much less delta-V from the tank.

Unless I didn't read the fuel flow-numbers right, the engine should burn through the same tank without oxidiser in the same time as it once burned through both. Thrust is still 60kN, and 60kN for the same time as before but without the mass of the oxidiser that was can only result in more delta-v. Sure, theoretically the rocket equation would state that higher wet mass with the same dry mass should give more delta-v (actually less dry mass because the engine was lighter then), but due to the way the game works (accelerating dynamically by thrust over current mass times time while mass changes) the oxidizer didn't really "count" as propellant. If one were to compare the working delta-v of nuclear craft in both .90 and 1.02, they'd find a crossover point where the new engine did better, once the lack of oxidiser mass overcame the added engine mass.

Though thinking about it...this may've screwed with mechjeb and KE's calculations.

[Frostiken]

The proper solution is for Squad to stop being lazy and expand the 'tweakables' options to let us play with fuel amounts, quantities, and types. It's practically trivial to do so. If you want to restrict it to certain tanks, have some 'universal tank' technology and only specific parts that can be played with. This also would've fixed the ROUND-8 debacle.

[iVG]

I think Squad did the right thing for stock Ksp however the hydrogen tanks would have to be even bigger so they left the ISP unchanged to balance out again. In the latest dev build of near future propulsion, there are hydrogen fuel tanks which hold a bit more h2 for the volume but are slightly larger. There are also config files which increase the ISP of the stock nuke to 900 which is much closer to reality.

Net result is similar but adds a nice dynamic to the Ksp - managing your tank sizes is the real issue even without the boil off And those tanks are specifically made for h2 only.

I suggest you give it a try and once you're done you'll see stock 1.0.2 is not that far off. I used to use lf fuel switch but hey, there's a better and much more realistic alternative!

[Laie]

Or if you're cool, you use mk2 short tanks instead, getting 400 LF with a .29 dry mass, beating the FL-T800 for both fuel and mass. I guess persons are complaining that they cannot abuse that as much as they'd like?

For the looks I prefer to provide proper tips & tails, which currently are only available as LF+O parts.. creating a strong incentive to place as many tanks as possible between the Mk-to-anything adapters. Yes, there's a mod for that. But I'd much prefer a proper stock solution.

Ceterum censeo: I'm very much tempted to use six or ten Nervas for every large Mk3 tank. Contrary to what the fuel misers want to make one believe, this is a sensible design: better TWR than a Skipper, more delta-V than a Poodle. However, the kind of mission where I'd need such a heavy tug already have 150+ parts to begin with; while technically I could have 4-5m/s2 acceleration from Nervas, in practice this doesn't work out because part count, lag, and heat. It's weight is by no means the worst downside of that engine.

- - - Updated - - -

Unless I didn't read the fuel flow-numbers right, the engine should burn through the same tank without oxidiser in the same time as it once burned through both.

While previously you needed 45t of LF + 55t of O to get a certain delta-V, now you get the same range by burning 100t of LF only. People are complaining that you now have to bring more tank to carry the same amount of propellant (the spaceplane tanks have a slightly worse mass ratio than LF+O tanks; and LF+O tanks without O are, of course, considerably worse)