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[0.90] RSS Stock Parts - Stock part tweaks for simpler Real Solar System play (v0.1)

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Have you ever wanted to give the Real Solar System mod a try, but don’t want to deal with the huge Realism Overhaul mods list? Would you like to fly around Earth (or an Earth scaled Kerbin) with same old parts you’ve been using for the last few months or years? Or do you just want to be able to show off your RSS scale creations to your fellow KSP’ers and actually have them recognize all your craft designs? If any or all of these are true, RSS Stock Parts is for you.

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What is RSS Stock Parts?

RSS Stock Parts is a simple Module Manager based tweak to many of the stock KSP parts to bring them in line with various, NASA, Russian, SpaceX, etc… designs so that they can be used on full (10x) scale planets at a difficulty level that closely simulates real life launches. RSS Stock Parts aims enable you to transition from playing stock, to full scale with a minimum amount of re-learning mechanics and installing additional mods.

What exactly does RSS Stock Parts change?

It’s very simple, RSS Stock Parts simply adjusts the weights of the various engines and fuel tanks in stock KSP to fall in line with the relative Thrust to Weight and Wet to Dry mass ratios that actual real life rockets have. That’s really all there is to it. The only other parts that received any changes are the cargo bays, that had their weights tweaked to be more in line (though still heavier than) the new weights of the fuel tanks that they share dimensions with. Everything else stayed the same.

How exactly did I go about determining the new mass values?

I started out by looking at the values of several well known and successful real life parts. The Saturn 5 F-1 and J-1 engines, the Space Shuttle SRB’s and SSME’s, SpaceX’s Merlin engines, various Soyuz engines, and the Lunar Lander engines. I also looked at the Shuttle’s external tank and the Saturn 5’s fuel tanks. After I had an idea of the range that the real life engines and fuel tanks fell into I went to the KSP parts and started dividing them into categories. For the engines, 1st stage lift engines like the Mainsail and KS-25x4 and so forth were matched up in TWR with engines like the F-1 and Merlin’s (TWR of mid 80’s to mid 00’s generally) Upper stage engine like the Skipper and KR-2L were brought in line with the SSME’s and other similar engines (TWR mid 50’s to mid 70’s). And landing engines like the 909 and Poodle were matched with the Lunar lander engines (TWR’s in the mid 20’s to 30’s).

For the fuel tanks I matched the dedicated rocket (1.25m, 2.5m, & 3.75m) fuel tanks up to fall in line around the Shuttle’s ET and the Saturn 5 in terms of wet to dry mass ratios, and then scaled the Mk3, Mk2, & Mk1 plane tanks to be slightly less efficient as they scale farther away from the rocket tanks. (Mk3 is fairly close, Mk2 with it’s lifting body starts to lose a fair bit of relative efficiency) Monoprop tanks were also brought in line, though they should in general be sightly less efficient than standard fuel tanks. Finally for the Cargo bays I simply made them weight 50% more than the same size of fuel tank to account for the mechanics of the bay mechanism.

Time for a few Example stats?

Mainsail: Old Mass; 6.0 - New Mass; 1.6
Skipper: Old mass; 3.0 - New Mass; 0.9
48-7s: Old mass; 0.1 - New Mass; 0.08 (48-7s was very strong, so needed minimal tweaking)
NERVA: Old Mass; 2.25 - New Mass; 1.75 (Best guess based off experimental NERVA’s TWR’s)

Orange tank: Old (Dry) Mass; 4.0 - New (Dry) Mass 1.2
NASA 14400 (Giant) tank: Old (Dry) Mass; 10.0 - New (Dry) Mass 2.7 (Fixed ratios being off for NASA parts)
Mk3 Long tank: Old (Dry) Mass; 6.0 - New (Dry) Mass 2.0
Mk3 Long cargo bay: Old Mass; 6.0 - New Mass 3.0 (50% heavier than long tanks due to door mechanics)

That really is all there is to it. Nearly every engine/fuel tank was tweaked in this manner (Jet engines were not at this time).

What does this mean in practice?

Simply, it means that you need a rocket that looks something like this to get a single kerbal to orbit and home, or to a station orbiting in LEO:


While a rocket like this will get the weight of a full Orange Tank to a station orbiting in LEO, and the upper stage can be landed back on Earth for recovery:


So what all do you need to make this work?

The Only thing actually required for RSS Stock Parts to work is Module Manager.

That said, RSS stock parts was designed to be used with:

Module Manager (REQUIRED)

Real Solar System (this is why we are tweaking the parts after all)

NEAR or FAR (the stock soup atmosphere does not go well with Real Solar System)

In addition, Kerbal Engineer gets a high recommendation, and will make it much easier to determine if you have sufficient d/v to accomplish your goal.

With just these mods, RSS is completely playable using RSS Stock parts, and your game will maintain a very stock feel, just bigger. Because RSS Stock Parts is nothing more than a Module Manager tweak for the mass of stock parts, it shouldn't however have any compatibility issues with any other mods you wish to add, nor should it have a perceptible increase to memory usage.

Sound good?

DOWNLOAD - Kerbal Stuff

Module Manager (REQUIRED) Download

License; http://en.wikipedia.org/wiki/GNU_General_Public_License

- - - Updated - - -

Let me know what you guys think in terms of balance, feel free to try out different values on your end (CFG is very easy to change) and let me know if there’s any changes you feel should be incorporated into the official version and I’ll give it a look.

Also let me know on your thoughts, should RSS Stock Parts stick to tweaking only the base required parts and mass ratios, or should I look at tweaking the mass of parts like cockpits and crew modules also. Also Should I play with the ISP’s of the various engines (Lower ISP of lift engines like mainsail, raise ISP of upper stage engines like skipper) or should I leave them as they are on stock so everyone knows what they are getting into. Tweaking them would balance the lesser TWR of upper stage engines compared to 1st stage engines better, while keeping it as is maintains the most stock like experience possible.

Let me know what you guys think, I played with this a little in .25, but just figured out how to make it a MM tweak instead of manually editing every part CFG, so now I can actually release it. (So basically balance testing has just been by me so far)

Edited by Yargnit
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is it compatible with Real Fuel ?

It was specifically designed as a simpler alternative to Real Fuel for people who want to be able to play on real scale KSP, but don't want to deal with new fuel systems etc. Real Fuel already makes similar tweaks, plus a whole lot more, so if you are using Real Fuel this would be fairly redundant. It shouldn't physically break it, but it probably won't exactly mesh well due to trying to tweak the same values. (Whichever tweak loaded last would override the changes made by the one that loads first)

I really like this, makes it a lot easier designing rockets in RSS. Is it available on CKAN?

I've never used CKAN, I wouldn't know what to do to make it available on there.


I'd highly recommend rescaling as well (1.6x should be spot on). This is because otherwise your pods will have only about 1/3 the drag they should on reentry, making reentry much, much harder.

I know a lot of the Realism overhaul stuff for RSS tweaked the sizes of parts. I specifically wanted to keep the stock .625/1.25/2.5/3.75m sizing to retain as close to the stock experience as possible. Shouldn't the drag work out the same that it does using NEAR/FAR on a regular scaled Kerbin, except with a correct scale height for Earth? The pods haven't had their mass values reduced at all.

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The number that controls how "tough" a reentry is, is called the ballistic coefficient: It's given as kg/m^2, i.e. how many kg of mass per m^2 of frontal area (i.e. Cd * S). With the pods as they are, it's rather high--since you have the real mass, but 39% of the surface area, that means your BC is 2.56x as high as real life. The higher the BC, the less you'll slow down high in the atmosphere, and the more you'll slow down in one big kerbal-squishing, metal-bending whump down low.

Here's the issue: when you're reentering on regular Kerbin, you're only going maybe 2-3km/sec. That means that final big whump isn't that bad. On Earth, however, you're at reentering at 3-6 times that velocity--8km/sec to 13km/sec. Is it survivable? Sure. But it's a lot harder--both in terms of heating and Gs--than it would be with real ballistic coefficients.

Your other option, of course, is to multiply payload masses by 0.4 or so. That will yield the same result for the crewed pods.

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  • 2 weeks later...
  • 1 year later...

It was only hosted on KerbalStuff, which is now defunct, and even if you could download it, it has a couple of pretty severe weaknesses,  In addition to the re-entry issue that @NathanKell mentions above, it only affects stock parts -- mod parts get left out in the cold.  There are a couple of better options if you're looking for a lightweight mod to make parts perform more realistically:

  • ROMini makes parts 60% bigger (so 1, 2, 4, and 6 meters in size) and makes TWRs and fuel mass fractions more realistic.  It only affects parts with stock resources (LiquidFuel, Oxidizer, Monopropellant, SolidFuel, XenonGas, and Ore).
  • SMURFF (by me) only makes parts lighter to modify fuel mass fractions and ballistic coefficients.  In addition to the stock resources, it also handles some resources used by mods like Near Future Propulsion and Cryogenic Engines (ArgonGas, LqdHydrogen, Lithium).  If you use this one, you might want to pick up a mod that adds bigger rocket parts, like SpaceY -- it's not impossible to get to the Moon with 3.75m parts, but it's far from easy (see the spoiler block below for the "Uranus V").



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