Increase TWR for lower ISP a fair trade off? Mod the Nerv

[Waxing_Kibbous]

Just looking for some engineering input here- I'm thinking of making a MM config that would add TWR to the Nerv (and maybe the ion engine) while keeping the in game balance of it. So, if one has a 30 minute burn with the Nerv, can we reduce it to 3 minutes while keeping the same amount of dV used? I'd only want to change the vacuum settings just to keep transfer burns shorter.

 Again, not a stock game request, just looking to tweak my own experience and perhaps free up time in other players lives as well

[Gaarst]

Multiply the thrust by 10. Same mass, 10x TWR, same Isp, same dV. Know that it will also increase your atmo thrust, you'd have to mess with atmo curve to keep it somewhat the same as before (though exactly the same won't be possible).

Though at this point, the NERV really just becomes a stupidly OP Skipper.

Edited May 23, 2016 by Gaarst

[Waxing_Kibbous]

20 minutes ago, Gaarst said:

Multiply the thrust by 10. Same mass, 10x TWR, same Isp, same dV. Know that it will also increase your atmo thrust, you'd have to mess with atmo curve to keep it somewhat the same as before (though exactly the same won't be possible).

Though at this point, the NERV really just becomes a stupidly OP Skipper.

An ideal condition for the higher thrust could be to increase 10x only when in orbit, I'm not sure if that is possible with MM though. Another idea would be to create a right-click option to turn on high thrust and use it just for transfer burns.

Edited May 23, 2016 by Waxing_Kibbous

[Gaarst]

43 minutes ago, Waxing_Kibbous said:

An ideal condition for the higher thrust could be to increase 10x only when in orbit, I'm not sure if that is possible with MM though. Another idea would be to create a right-click option to turn on high thrust and use it just for transfer burns.

Yes, on second thought, MM could enable you to make a double mode engine out of the NERV (like the RAPIER or afterburners) which would increase its thrust. You'd then be able to keep the original config for atmospheric use and switch to the other one for vaccuum.

Though I don't know how to do this, so I won't be able to help you any further.

[Streetwind]

1 hour ago, Waxing_Kibbous said:

So, if one has a 30 minute burn with the Nerv, can we reduce it to 3 minutes while keeping the same amount of dV used?

Not sure if you're aware what you're saying here, but that's kind of a nonsensical statement Mabye you wanted to type something else instead?

A transfer burn to the same target orbit generally takes the same dV regardless of whether you do it in a second or a minute. Additionally, as long as Isp stays the same, the amount of fuel expended (in physical volume and mass) also stays the same. Okay, you start to get precision losses as the burns get longer, especially in tiny Kerbin's low orbit, so there's that...but unless you're going way past the point where it is more comfortable to just split the burn, we're talking a few percent here.

So if you want to keep fuel usage the same and just have more TWR, thrust is all you really need to change, so you can do what @Gaarst suggested. Of course, that is a buff with no trade-off... what you will have done there is essentially the same as taking the Skipper and buffing its Isp to NTR-levels. So in order to remain "balanced" with the rest of the stock engines, a NERV buffed to ten times its thrust would have to drop its Isp down to something like 350. And then you might as well just use a Skipper in the first place

The straightforward way to get shorter burns with NTRs, by the way, is to mount more of them. You mount about twelve to fourteen of them, and end up with roughly ten times the TWR (depends on your ship's mass). Of course, all that extra dry mass will ruin your vessel's dV... it will probably not be much greater than if you had just... you guessed it... used a Skipper in the first place This is not an accident, but rather illustrates the balanced tradeoff between thrust, dry mass and Isp between different engine types. For specific applications, specific engines are better than others; and the LV-N is specifically not the engine suitable for keeping burns short.

I mean, you're free to make your LV-N as overpowered as you want. It's your game - if you want to imagine your Kerbals living in a universe where super-powerful NTRs are an everyday thing, then by all means, knock yourself out! I'm just trying to help you understand the relationship between the values you seek to modify, and the game design ideas behind them. It's always easier to break the rules if you know the rules

Edited May 23, 2016 by Streetwind

[Kerbart]

1 hour ago, Waxing_Kibbous said:

Just looking for some engineering input here- I'm thinking of making a MM config that would add TWR to the Nerv (and maybe the ion engine) while keeping the in game balance of it.(...)

Not to pile onto what the others said (well, kinda... I'll admit) but the low TWR of the Nerv is the game balance. Unless you want to change the I_sp - but in that case, why not simply pick another engine, like the Terrier, Reliant or Swivel?

[Waxing_Kibbous]

OK, so it appears the proper answer is to design around not using nukes in the first place, and I will also look into some alternate nuke engines from mods as well. See, this is why I consulted the engineering team first

[Kerbart]

If your issue is a big & heavy craft (given your 30m burn time), consider piling on more engines. You keep the I_sp, might lose a bit of DV due to extra mass (but at the quoted burn times not that much, hahaha) and you'll have the rewarding sight of lighting up a dozen (or more!) engines when kicking off for your journey!

[Jovus]

I have exactly the right sig for this.

Take the MM patch in my sig, remove the Oxidizer from the second mode, and you're ready to go.

[Norcalplanner]

Modular Rocket Systems by Necrobones has the quad-nuke, which helps increase the thrust of a NTR craft while keeping the part count down and having a more natural rocket shape.

If you want to go LFO, I recommend the Penguin from SpaceY expanded. Same weight and thrust as the Skipper in a 3.75m part, bit with an Isp of 400.

[sebi.zzr]

Well,i wouldn't alter any cfgs or designs,if your burn time seems too long,you can simply use physics time warp (Alt+ .) while accelerating.
In short 4X time warp = 4/burn time

[Terwin]

If you want to keep your part-count down, I would recommend tweakscale, it will scale up your parts increasing functionality in line with the increased mass.

(example: a 400% drill has the same stats(weight, energy usage ore production, etc) as 64 normal drills(4x4x4=64) but also has 4x the reach for getting past long pieces of infrastructure(and takes a lot more surface area).

I generally use a 2.5m nerv in place of ~5 normal sized engines for example.

 

But anything that actually improves performance over using multiple stock parts is not really on par with the 'balance' of stock parts(Nuclear Lightbulb from Atomic age for example has 1500 isp and ~7.5 times the thrust of a nerv not to mention gimble and 850isp in atmosphere.  Even at 20 tons it is still the go-to engine for any ship large enough to use full size ISRU to extend it's range) 

[Matuchkin]

Or we can add in-game time warp that you can turn on while performing maneuvers, like in Orbiter. That will solve all these problems.

Edited May 23, 2016 by Matuchkin