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

[Matt516]

Wow, thanks for the quick reply. Much appreciated. I'll just estimate or calculate things manually for now.

While you're online, I had a quick question about the FAR->Stock, atmo only setting? I'm using FAR and want to counteract the easier orbiting caused by the reduced drag, but I don't want to deal with increased fuel requirements in space. I would use the 0.38/1.0 setting, but that seems like it would penalize atmospheric flight a bit much. Since you did the math/testing behind the settings, I thought I'd ask - that 0.38 multiplier only "exactly" counters the reduced drag when going into orbit, right? Which means that atmo-only flight is heavily penalized compared to stock, right?

Do you happen to know which multiplier would strike somewhat of a balance between correcting the fuel requirements for orbit, but not penalizing in-atmo planes extensively? I've been playing with multipliers of 0.6 and 1 respectively, which seems to me to be a reasonable balance. Thoughts?

[AngelLestat]

Yeah I also want the same thing that Matt516 wants.

But I dont know if that is possible.

I love FAR, but this push you to use RSS, I would like to use always RSS but not all mods are supported, the graphic quality decrease due to x10 and any mission duration is increased.

So how can I use FAR/Near without decrease so much the difficulty to launch rockets, without change vaccum or atmospheric flights much.

What settings on KIDS may help with this? Or the thing that we are asking is just not possible.

[Matt516]

I'm a little confused, Angel - are you saying that FAR requires the use of the Realism Overhaul (RSS)? Because that really isn't true....

[Diazo]

I think where AngelLestat is coming from is that because FAR has somewhat reasonable aerodynamics, the amount of fuel needed to get to orbit is reduced so much it makes it much easier then in stock.

Hence the comment about using RSS for the larger Kerbin to make getting to orbit harder (require more fuel).

He wants to use this instead and is asking about settings.

My personal preference is a flat setting of .8 across the board, I think it's the FAR to Stock (or maybe the FAR to Real Life) preset.

I have not tried this mod in career mode yet though, that game is going to wait until I get a few more tweaks done to my mods first.

D.

[AngelLestat]

What I mean to said, is like FAR is a realistic aerodynamic model, you need highest velocities to experience the loss of deltaV due atmosphere.

So in RSS you had highest velocities and extra time (inside the atmosphere, enoght to note the drag issue).

That is why I am not sure if KIDS may help or not.´

I will try with your parameters Diazo when I find time.

[cantab]

Well the whole point of KIDS is to "correct" the balance changes caused by FAR.

Of course there are always compromises. You can correct the performance for any two of launchers, aircraft, and spacecraft, but not all three.

A few things to consider:

Most of a launch to orbit is done in near-vacuum conditions as far as engine efficiency is concerned. That's why the FAR to Stock Atmospheric preset has to hammer the atmospheric Isp so hard.

For that matter, much aircraft flight is done where the pressure is much closer to vacuum than to sea level too. At 8 km, a reasonable cruising altitude for a basic jet powered craft, the pressure is 0.2 atm. Turbojet or RAPIER powered craft are likely to fly even higher.

In stock the jet engines are already way too efficient. I know FAR changes the jets but I don't know if it really fixes their efficiency. So a nerf to their Isp might not go amiss.

[karamazovnew]

@Matt516 and AngelLestat

ISP Multipliers: these settings control the fuel consumption of your engines and thus your DeltaV. A multiplier of 0.5 means that your DeltaV is halved, because you burn twice as much fuel in the same time, at the same thrust.

- Vacuum Isp Multiplier: This is your main reason for using this mod. It dictates the size of your upper stages and the complexity of your landers. Various mods might require various settings, but the best value I've found, by eyeballing the DeltaV for various rockets is 0.81 (same as Far To Stock KSP, Universal setting for KIDS). Anything less is game breaking if you plan to use most mods (nevermind trying to land on the Mun in stock career).

-Atmo Isp Multiplier: Same as for vaccum, but it only works in atmosphere. This will usually only affect your first stage. On Kerbin, that's below about 30km. Normally, this value has to be as big, or smaller than the Vacuum value. This is very much up to personal taste and it's also affected by the next settings. If you don't enable the thrust settings, a value of 0.61 seems to work nicely. You can easily get an Apollo style rocket that has a 3.75 meter first stage, without the need for any boosters or asparagus. However, if you enable the thrust settings, a value of 0.65 seems to work best.

-Extend curve to 0 ISP: no harm in leaving it on, it will only affect you if you go into atmosphere heavier than 1atm (Kerbin sea level).

Thrust varies with ISP: if you don't use this, thrust and TWR will be the same as stock, both in vaccum and in atmo. If you use it, at sea level, your engine thrust will be multiplied by the Atm Multiplier. So, a setting of 0.5 for that will halve your TWR. Again, this usually affect only your bottom stage. If you don't use powerful enough engines, you will spend more time below 20km (because your speed raises slower). This means you loose fuel because of more time spent in air friction AND gravity turns are slower AAAND your gimbaling is not as effective anymore so it's harder to control your rocket during the gravity turn. With FAR, you will usually throttle down your big engines anyway once you reach 200m/s so it's not THAT bad, the hard part is getting to 200m/s. Normally, even stock 1.25m engines are more than powerful enough to get you off the ground and into orbit. Just use some solid boosters for help. Mods like MechJeb will not show a correct TWR, until you actually launch.

-Engine Rating settings: I don't use these. Unlike the other settings, these don't make the game harder, but easier. If you don't use them, all engines will be affected by the "Thrust varies with ISP" equally. That means that all engines will loose thrust in atmosphere. Why wouldn't you want that? Well, here's a reason. What if you want a real replica of the Saturn 5? 5m bottom stage? Well, in that case, a vacuum multiplier of 0.81 would be HUGE, so you'd have to lower it. You might think that the added weight of fuel would not matter so much in vaccum, where TWR is not important. But even the most powerful engines will just cough up and die on the launch pad. The solution? Break up the engines in two categories:

-- vaccum rated engines (that have low thrust and high isp) that will continue to work as normal, having reduced thrust in atmosphere and reaching their maximum rated thrust as you pass 30km altitude.

-- armo rated engines (hight thrust, low isp) that will start at rated thrust on the launchpad and INCREASE their trust, reaching a new maximum as you pass 30 km altitude.

Also, it stops you from using the KW Vesta VR-1 in your launch asparagus

So why don't I use them? Because with my multipliers, most engines get much too powerful, messing up my 2nd and 3rd stages which I use for circularization, outside the 30km altitude mark.

Hope that helps Again, here are my settings:

Atm ISP multipliers: 0.65

Vac ISP multipliers: 0.81

Extended Curve: ON

Thrust Varies with ISP: ON

Engine rating settings: both off.

Edited December 29, 2014 by karamazovnew

[Matt516]

Re: Thrust varies with ISP - you're partially right, but it's more than just having the engine thrust multiplied by the Atm multiplier. In stock, every engine always has the same max thrust, and the fuel consumption varies with ISP (so as you go out into vacuum, fuel consumption generally goes down because ISP is increasing). Having that option turned on causes the fuel consumption to stay constant, and the thrust to vary with ISP instead. This is mainly a realism setting, as it shouldn't affect gameplay a huge deal because ISP is the same and therefore delta-V of any given stage is the same.

And re: extended curve, there's certainly no harm in leaving it on when you're roundabout Kerbin. But if you plan on going anywhere with a denser atmosphere than Kerbin, it's gonna hurt you pretty bad.

Edited December 29, 2014 by Matt516

[Buzzer]

I was reading some posts back there but didnt find anything... My question is: I´m using FAR, AJE, RF and RSS so with that, what´s the realistic option for me? I saw this https://github.com/KSP-RO/RealismOverhaul/wiki/First-RO-Rocket and noticed that in the 6th picture a dV of 4218 shows up... I couldnt find any settings that gives it to me. I´m using the FAR to Real Life (adjusted) setting and getting like 2700. So, again, what´s the most realistic setting for me?

Thanks and sorry for my english, it´s not my native language.

[cantab]

Since you're using FAR and RSS you already require a real-world delta-V to orbit. If you want to use stock parts you can use KIDS to make them perform better, but really you'd be better off using modified parts or configs so you get realistic engines rather than fudged ones. Then KIDS would just sort out scaling maximum thrust with altitude, and not change Isp (leave atmo and vac both at 1).

[Buzzer]

So I just create another preset in KIDS with both atmo and vac at 1.0 and leave the Extended Curve and Thrust Varies off? Thanks for now.

[AngelLestat]

Hope that helps Again, here are my settings:

Atm ISP multipliers: 0.65

Vac ISP multipliers: 0.81

Extended Curve: ON

Thrust Varies with ISP: ON

Engine rating settings: both off.

Thanks a lot karamazovnew, I will keep your post in mind each time I test different parameters.

The only drawback of reduce the isp of engines inside atmosphere is the case we want to use those engines to land or hover.

[rossmohax]

@Matt516 and AngelLestat

- Vacuum Isp Multiplier: This is your main reason for using this mod

I am really confused with this one. FAR and NEAR change aerodynamics, why there is a need to change ISP in vacuum where those modes have no effect?

[cantab]

Because FAR, NEAR, and for that matter Stock Drag Fix reduce drag, they reduce delta-V required to reach orbit. This increases payload fraction of launchers using the same parts, so the same payload goes up on a smaller rocket, which some players don't like. Reducing the engine specific impulse reduces payload fraction of launchers, counteracting the effect of lower drag. The simplest approach is to reduce the specific impulse in all conditions.

[Renegrade]

Little note here - the 0.25 issue reported earlier of a conflict between AJE and KIDS is still happening in 0.90 with AJE 2.02 :/

[karamazovnew]

I am really confused with this one. FAR and NEAR change aerodynamics, why there is a need to change ISP in vacuum where those modes have no effect?

Sorry for the late reply.

KIDS is more than just a "FAR to Stock" fix. It allows you to make the game as hard as you want, by controlling how much fuel you need to bring. Do you like how the small stock rockets can take you to Duna and back? Most don't. The settings that I posted above make the game very hard on the Hard Career difficulty. I can easily reach orbit early in the career. But after that I need to get inventive, I need to choose, I need to grind, I need to improvise, I need to simplify. Do I really need that extra battery? Do I really need Repair Parts, extra ablative shielding? Better not accept that "Explore the Mun" contract too fast I'm at my limit at almost every launch, and I absolutely love it. And it's all because of KIDS and the "Vacuum Isp Multiplier".

For example, let's assume that I play in STOCK and the only mod I use is KIDS. I want to crash into the Mun. Whatever rocket I put into orbit, the payload needs a fixed 900 dV to reach the Mun and crash into it. In stock, maybe that's just a small tank of fuel with a small engine. Simple, light. But if I reduce the Vacuum Isp (and Atm to the same value), I need more fuel to get the same dV in space. That 900dV suddenly requires an extra tank of fuel on my Lunar Impactor XS. So I need to make the payload bigger. That means that I have to put a bigger payload in orbit in the first place. That means an even bigger middle stage, heck, maybe so big that I have to put a more powerful engine in it just to keep my TWR above 1 to be able to circularize before reaching Ap at 70km. That means that my first stage now becomes humongous with the biggest engine that I have, just to get it to 15km. Even so, I might need to put some extra boosters now, pushing my launchpad weight limit to the max, my max parts number beyond max. Even with a seemingly high value of 0.81 for the KIDS multipliers, I'm always barely able to continue in career mode. And I like that.

Let's assume that then I install FAR. The only thing that changes is what happens in the first 30 km or so. Suddenly, my "barely able to reach orbit" rocket has fuel to spare. Suddenly, I can reduce the size of my first stage, and my second stage (but not my payload). A difference of 5-900dV that FAR saves you means that suddenly your game isn't "at the edge hard" anymore. So only then I reduce the Atm ISP Multiplier.

But then I think to myself: what is this part that I've never used before? Solid Rocket Booster? What is that for?! My 2.1 TWR first stage is good enough for me. Well, that's when you enable the Thrust Varies with Isp setting.

Hope that explains why I said "Vacuum Isp Multiplier: This is your main reason for using this mod"

[rosenkranz]

Quick question.

I'm currently doing a playthrough using the 6.4x mod. So ksp isn't quite RSS sized. However, I don't really feel like using Real Fuels to get stuff to orbit.

I was thinking to use KIDS to boost my ISP a pinch. What might be a decent persentage? Or is is really suppose to be nigh impossible to get to orbit with just 1.25m parts?

Edit: I should probably note that I am already using FAR. It should be 7500dV to a 200km orbit.

[NathanKell]

Nigh impossible? Methinks you might need to rethink your build or your ascent. Should be able to get about a ton into orbit with a T800/LV-909, a couple 800s and an LV-T30, and then six BACCs staged 4 and then 2. (i.e. first stage 4 BACCs, second stage 2 BACCs, third stage LV-T30, fourth stage LV-909). Maybe you're playing with ~LOLSOKERBAL~ TWRs? You don't need high TWR.

[Kesa]

Hi, I'm using Realism overhaul, so I have real fuel, which set Isp to realistic values and scale the thrust with Isp, but does not seem to extend Isp curve to pressure greater than 1 bar (at least from what I see from KER's VAB readout). So I wanted to know if it works fine with RF, despite Overlaping features, and if I can use KIDS only for pressure higher than 1. If I do, how should I configure KIDS (No preset config seems to suit my need)? Nothing but the extend "Extend curve to Zero Isp" enabled?

More few question, just for curiosity, how does this mod change the Isp? What does a rocket Isp curve looks like in reality in KIDS in RF and in stock?

Edited January 21, 2015 by Kesa
My SRBs don't have higher Isp at atmo than in Vacuum

[Wercho]

BUG Report:

I seem to have stumbled on an incompatibility between this and Procedural Parts SRBs. Specifically, when I have "Thrust varies with Isp" on, KIDS seems to override the custom thrust of a PP SRB. Turning off the thrust varying seems to fix the problem. I have screenies if that helps.

Logs: These were taken from a sandbox game in which I went back and forth from the VAB to the launchpad a bunch of times, changing settings on KCT and KIDS until I narrowed down what was causing it.

KSP.log

output_log.txt

EDIT: System specs

Windows Vista x64

KSP 0.90 x32

KIDS 1.4.2

PP 1.01 (there is a 1.02 out, but it only changes the part model according to the changelog)

+ a bunch of other mods

EDIT2: More info: Kerbal Engineer shows the correct thrust in the VAB, but incorrect on the pad with KIDS "Thrust varies with Isp" on (because KIDS "Thrust varies with Isp" doesn't take effect in the VAB). It is clear based on my small rocket shooting up to mach 4 very fast that the thrust is actually set to the 284 kN displayed on the pad by KER, and not the desired 70kN selected in the VAB.

Edited January 21, 2015 by Wercho

[rynak]

Crosslinking apparent incompatibility with SRBs from procedural parts mod:

http://forum.kerbalspaceprogram.com/threads/106975-0-90-Procedural-Parts-Parts-the-way-you-want-em-v1-0-Jan-11?p=1691961&viewfull=1#post1691961

(Scroll down a bit for post about it probably being related to KIDS)

The relevant issue from github is this:

https://github.com/Swamp-Ig/ProceduralParts/issues/96

In short, procedural SRBs let one set the thrust in the editor. But once entering flight, it seems that KIDS applies the default thrust (instead of the custom one), if "thrust varies with ISP" is enabled in KIDS.

[tajampi]

This mod is amazing

Everything looks much more realistic when you have a 10% payload fraction with FAR!

Cheers!

[Invader Myk]

I installed this and FAR, set KIDS to "FAR to Real Life, Adjusted", then spent 20 launches (punctuated by a few ragequits) trying to get back to orbit.

Excellent mod btw.

[rottielover]

I wanted to try this mod, so I installed FAR, KIDS, FASA and used the "Far to Real Life Adjusted" pre-set.

Unfortunately the Apollo CSM on top of the Saturn V from the FASA pack can just barely reach a stable orbit. So I'm not sure if I'm missing something in the setup steps required, or if I have something installed wrong ?

[NathanKell]

You installed "FAR to Real life". That means you now need a rocket as powerful as real life to get into orbit. That means a rocket that, without KIDS, would give you 9.5km/sec of delta V.

With KIDS set to that preset, see how much delta V your rocket has. If it has less than 3500m/s, you are not going to space today.