[0.90]Kerbal Isp Difficulty Scaler v1.4.2; 12/16/14

[NathanKell]

Nope, not if you're using FAR, which you bloody well should if you care about realism.

Then it's a flat 0.3333 multiplier in both cases.

Or whatever it is for FAR adjusted, should be the same in both cases.

(Because FAR:real is also 1/3, since 3.1km/s, the minimum to orbit, is 1/3 of 9.3km/s)

EDIT: All this has basically convinced me to make a modpack that gives all parts realistic masses, to go along with this mod. See discussion in the StretchyTanks thread re: correct tank dry masses.

Oh, one more thing: airbreathers. Unless you're using a scramjet, you should really be limited to 5-600m/s tops before switching to rockets. That keeps the proportion of dV gained by jet and gained by rocket proportional with real life, where transition speed is approx 1800m/s max for even ramjets.

Edited October 20, 2013 by NathanKell

[NathanKell]

So rather than clog this up further I made a new thread, which might be of interest. Talking about masses, now, because I think a flat 1/3 scalar for Isp, assuming using FAR, is spot on, and we shouldn't fake better mass ratios here, we should just change masses.

The thread, for discussion of a total realism overhaul, is here:

http://forum.kerbalspaceprogram.com/threads/54327-Realism-Overhaul-Brainstorming

[Autochton]

Oh, one more thing: airbreathers. Unless you're using a scramjet, you should really be limited to 5-600m/s tops before switching to rockets. That keeps the proportion of dV gained by jet and gained by rocket proportional with real life, where transition speed is approx 1800m/s max for even ramjets.

The exception to this would be SABRE style intake precoolers, which give non-scramjet engines air up to Mach=5 or so. The B9 version (the common SABRE-analogue in KSP at the moment) models this by giving the intakes the precooled level of air, since there isn't a ready way to adjust intake air according to whether a precooler is present. As a result, the precooler part is just a bit of structure, not an actually functional part. I honestly wish it could be brought to work like in real life, though.

[hyperionxl]

I can't for the life of me get a rocket into orbit. The few times I have done it seem like a complete fluke and I'm left with a sliver of fuel in my final stage.

Anyone wanna show off their lower-tier rockets with Real/Real Adjusted? Attempting to get through career mode with this mod is a boat load of fails. 70 launches and only 2-3 stable orbits >.<

[Miller]

This mod is great, however i have a question. How does it differ from Modular Fuel System?

[NathanKell]

The exception to this would be SABRE style intake precoolers, which give non-scramjet engines air up to Mach=5 or so. The B9 version (the common SABRE-analogue in KSP at the moment) models this by giving the intakes the precooled level of air, since there isn't a ready way to adjust intake air according to whether a precooler is present. As a result, the precooler part is just a bit of structure, not an actually functional part. I honestly wish it could be brought to work like in real life, though.

Um no. Like I said in my post, since we have to divide by 3, Mach 5 _is_ 500m/s in "real" mode.

The point is that while Mach 5 on Earth is 1500m/s or so, that' still only 16% of the dV needed to orbit. So spaceplanes in KSP should also be limited, in their airbreathing mode, to 16% of 3100m/s, or 500m/s.

Again, unless they're scramjets, in which case they can top out where KSP planes normally do (1/2 to 2/3 orbital dV)

[jpinard]

Ferram this is an incredible mod - just what I was hoping to find. But I'm really new to the game so I was wondering. I'm just about to install FAR and wanted to have this offset the smaller engines, but didn't want to go all the way to Earth realism since the Kerbal planet is so much smaller... but would like it so it takes more fuel/engine power to get into orbit. What setting do you suggest I use?

[ferram4]

@hyperionxl: Yeah, it's really difficult to do. Here's an album of a Soyuz-like mission I did, using the FAR to Real Life, adjusted setting; take note of how large the launch vehicle is compared to the orbiter. If you dispense with the orbital module you should be able to cut down the fuel requirements a little bit.

@Miller: Modular Fuels involves changes to tank mass, fuel density, and some Isp changes (I think) to try and make things a bit closer to real life. This mod simply universally scales Isps (primarily) to make things as difficult as you choose. This mod also allows you to have different presets, so that you can have one save where things are ultra-realistic in terms of rocket mass needed to get anywhere and another save where things aren't changed at all.

@jpinard: You can try using the FAR to Stock KSP settings, which will make getting to orbit as difficult as it is in stock KSP; the universal one will be less punishing in atmospheres, but will require more dV for orbital maneuvers; the atmosphere only one won't punish you in space, but will make flying deep int he atmosphere very painful. If you'd prefer it to be a little harder than that, you can simply add a new preset that makes things a little bit harder than either of those.

[a.g.]

What is the proportion curve for balancing the change in atmospheric and space ISP for the "FAR to stock" difficulty setting idea? For instance, does 0.6 atm 0.9 space produce the same difficulty, or are the numbers off? Also, I wonder how enabling the thrust scaling feature affects the "difficulty" in this context.

[allmappedout]

Surely, surely you are the next modder to get approached by Squad?! You've basically reengineered their entire game, without breaking it, and you have a firm grasp of both working within the community and the mathematics behind it all.

You sir, are a genius, a word which Apple have butchered, but one I do not use lightly.

[Camacha]

@hyperionxl: Yeah, it's really difficult to do. Here's an album of a Soyuz-like mission I did, using the FAR to Real Life, adjusted setting; take note of how large the launch vehicle is compared to the orbiter. If you dispense with the orbital module you should be able to cut down the fuel requirements a little bit.

For me that raises whether it is realistic or not. Can you elaborate on that?

Also, are the heavier than real tanks and engines accounted for?

[Autochton]

Um no. Like I said in my post, since we have to divide by 3, Mach 5 _is_ 500m/s in "real" mode.

The point is that while Mach 5 on Earth is 1500m/s or so, that' still only 16% of the dV needed to orbit. So spaceplanes in KSP should also be limited, in their airbreathing mode, to 16% of 3100m/s, or 500m/s.

Again, unless they're scramjets, in which case they can top out where KSP planes normally do (1/2 to 2/3 orbital dV)

Of course we then also run into having the sound barrier at ~110m/s, planes taking off at ~25-35m/s, etc. Eesh. This is something of a can of worms.

[NathanKell]

And so there's the alternate solution.

[ferram4]

@a.g.: To figure it out properly you'd need to integrate along the launch profile to figure out the total dV, accounting for changes in Isp due to air pressure changes and adjust the atm and vac multipliers until the proper dV numbers come out. I would guess that the proper numbers in your example would be closer to 0.9 vac, 0.55 atm, but that's just me making an educated guess.

To be honest, I figured out the atmo-only preset using the method of "Launch a Kerbal X with the universal preset; then launch another one with the atmo-only preset; adjust the atmo-only preset until they had the same fuel in the same orbit." Very ad hoc, but it worked fairly well.

The thrust scaling feature should probably make using the atmo-only preset silly; consider that any atm-rated engines would produce a ton of thrust in vacuum, while vac-rated engines would make no thrust in atmo. Probably not a good idea to use both.

@Camacha: Consider that the real-life Soyuz rocket burns ~95% of its mass to put its payload into orbit, which is very similar to what had to be done on my mission. If the separate orbital module with the hitchhiker, docking port, lights, batteries and adapters were removed the payload would have been reduced enough that a decent chunk of the launch vehicle would become superfluous, I think.

The "adjusted" settings are designed to try and account for the higher dry masses of fuel tanks and the larger masses of engines.

[a.g.]

Does the same fuel in the same orbit mean the same dV left? If you consider the overall mission difficulty rather than just getting to orbit, it probably should take into account the scaling of vacuum ISP by allowing an appropriate percentage of additional mass into orbit.

What I'm looking for actually is some kind of hybrid setting, i.e. some values that reduce vacuum isp less, but don't reduce atmospheric efficiency as much, while providing an overall stock-like level of difficulty. Currently I have it set to 0.6 atm, 0.9 vacuum, thrust scaling on. The low thrust of liquid engines does make using atm-rated SRBs at liftoff more essential, so I think it might count as reducing the average isp of the first stage even more.

[Autochton]

And so there's the alternate solution.

OK, not exactly the spot for it here, but: *SQUEEE*

[StainX]

So with this mod i have to build "bigger" ships to get in orbit with the realism setting... but isn't thats kinda useless if those huge rockets still wobble and are unstable as hell (Saturn V, stock vs Realism)?

[Hodo]

So with this mod i have to build "bigger" ships to get in orbit with the realism setting... but isn't thats kinda useless if those huge rockets still wobble and are unstable as hell (Saturn V, stock vs Realism)?

Not really. If you build a rocket right it wont wobble or be unstable as hell.

[Visari]

I've been doing the career mode starting out with KIDS.

loving the challenge!

Although the tech tree is absolutely unfitting for realism mods such as these, it's still a fun challenge to even get to the Mün (completing my first DRE, FAR, TAC LS, KIDS FAR -> RL, adj manned Münar return mission was really satisfying).

I've been working on a tech tree design that supports realism, especially FAR, starting out with planes, progressing up in a realistic, balanced and fun way to space travel, but it'll be a while before that's usable.

Keep up the great work, Ferram!

[therealcrow999]

Does anyone have any videos on Youtube of this mod? I wanted to see comparisons and see how it works in action.

[NathanKell]

It....requires larger rockets? There's no visual difference. If you want to see how it works, just build a rocket that gives you 9000dv.

[Spartan125]

Advanced SRBs aren't affected by changing the isp values and so their isp remains almost twice as efficient than liquid engines at sea level using the presets.

[ferram4]

I'm not surprised it's incompatible with Advanced SRBs; it's using a different PartModule, which means that KIDS wouldn't know to change it. I'll look into a fix.

[KerbMav]

As I first read the OP it seemed to me to do the same thing as Arcturus mod, decreasing thrust instead of increasing fuel flow in denser atmospheres. Because Arcturus mod is no longer maintained as seems to have problems with jet engines and mod compatibility, I would like to use KIDS instead ... (you know quite well what you did by naming it that way?) ... but it seems to do something completely different?

[Chestburster]

Just use the Stock preset and make sure the "Thrust Varies with ISP" is checked to only have the arcturus functionality enabled.