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[1.8+] Real Fuels


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The previous Modular Fuel System has split into Modular Fuel Tanks (taken care of by taniwha; for all your stock-resource modular-tank needs) and Real Fuels (by me, modular tanks and engines using real resources). Use one OR the other.


Contributors: NathanKell, Butcher, DRVeyl, Al2Me6, siimav, Standecco, Chestburster, Starwaster, taniwha, swamp_ig, ialdabaoth (obviously, but back again!), blowfish

ialdabaoth (who is awesome) created Modular Fuels, and this is a fork of the RealFuels branch.

Required mods (get them by installing RealFuels in CKAN):

* Module Manager by sarbian, swamp_ig, and ialdabaoth. See thread for details: http://forum.kerbalspaceprogram.com/threads/55219

* Community Resource Pack: See thread for details: http://forum.kerbalspaceprogram.com/threads/91998

* SolverEngines by NathanKell and blowfish. See thread for details: http://forum.kerbalspaceprogram.com/threads/122976

Includes ullage simulation code based on that by HoneyFox in EngineIgnitor, reused under MIT License. See end of readme for license details.



Real Fuels does the following:

* It converts resources to use 1 unit = 1 liter at STP, and changes tank capacity to accord with that.

* It allows any supported tank to be filled with exactly how much or how little fuel you want, of whatever type you want (though different tanks may allow or disallow certain fuels; jet fuel tanks won't take oxidizer for instance). Tank dry masses are set to replicate real-world rocket stages.

* Real world fuels are added, and engines/RCS can use them, with realistic stats (NOTE: You NEED an engine pack in order for engines/RCS to use the new fuels).

* Engines/RCS can have multiple configurations (for example, an upper stage could support a kerosene + liquid oxygen mode, and a liquid hydrogen + liquid oxygen mode). These modes have different thrust, Isp, etc.

* Engines/RCS can have varying techlevels: different performance characteristics for the same part, based on the techlevel you select (techlevels can be tied to R&D nodes for career games).

* Configs and techlevels can have their own unlock costs

* Engines can have limited throttling, and can have limited ignitions.

* Engines can be subject to ullage requirements.

* For advanced features, engines use ModuleEnginesRF (powered by SolverEngines).


1. Delete any existing ModularFuelTanks folder or RealFuels folder in your KSP/GameData folder. Remove CommunityResourcePack and SolverEngines if they exist as well. This is VITAL.

2. Extract this archive to your KSP/GameData folder

3. Download and install an engine pack. Your choices currently are Stockalike RF Configs or RealismOverhaul. See the second post in the RealFuels thread for information.


You can access RF-related GUIs ingame by tweakables, or by going to the Action Group Editor mode in the VAB/SPH (i.e. where you assign things to action groups) and clicking on a tank, engine, or RCS module. If supported, the GUI will appear.

For tanks:

At the top will appear the total tank mass (wet), the tank dry mass, the available, used, and total volume (in liters). Below appears the set of resources that may be added to the tank, and the current amounts and max amounts (if any).

If there are engines on the vessel, and available volume in the tank, autoconfigure buttons will appear at the top of the list, one for each fuel mixture used by the engines on the vessel. When you hover the cursor over an autoconfigure button, a tooltip will appear showing the engines that use that mixture. Click an autoconfigure button to automatically configure remaining volume for that mixture.

Note that gases and electric charge have multiple "units" per tank liter, since gases are given in liters at STP but stored under pressure, and electric charge is in kJ.

When you right-click on a tank, you can also access the 'remove all' and the 'configure for' buttons.

For engines/RCS:

At the top are buttons for changing the current engine's configuration. Then there are the buttons for changing techlevel. They will have X if a change in that direction is unavailable. Below that are stats for the current config and TL. NOTE that if your RCS uses a fuel that is set to STACK_PRIORITY_SEARCH rather than ALL_VESSEL (anything except MonoPropellant) you need to have fuel feeding your RCS thrusters (i.e. treat them like radial engines). It is suggested you get CrossFeedEnabler to help with this.




Install via CKAN (preferred) or Download

Source on Github


License remains CC-BY-SA as modified by ialdabaoth.

Pictures of RF in action:



Edited by NathanKell
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Engine Configs

Download and install ONLY ONE.

"Stockalike" engine configs updated by Raptor831 based off work by Chestburster.


Real Engines. It comes with Realism Overhaul, and converts engines that look like real engines into their real counterparts.


Reaching for the Stars, a set of alternate history realistic engines (and other things) developed for my RftS universe.


Roll your own configs. Here is the spreadsheet I use to make engine configs. It's currently set for RftSEngines because that's what I use. Docs on the first sheet.


It's always at that link, so keep it around and check it for updates.


Stockalikes: this set is mostly as of MFS 3.3, as updated by Chestburster and myself (though J_Davis and Chestburster are currently reworking it to use all the new goodies in RF v4). This tries not to change thrust or mass from what you're used to, with only a couple necessary exceptions (when TWR is *way* out of whack, mass was changed). Supports the most engines.

RealEngines: by RedAV8R and SFJackBauer, it uses various models (from various parts packs) to represent real-world engines like the Merlin 1D, the SSME, the RS-27, Vulcain 2, RD-107, etc. Like the other two, only the patches are included; you need the part packs too. RealEngines supports the least number of engines, but each one is lovingly set to be an exact 1:1 performance clone of a real engine, with as close a model as could be found. However, each of those supported engines will have configurations available for all its known real-life variants, so you get more engines than you might think.

Reaching for the Stars Engines: by me, it's a set of realistic engine configs: that is, a set of configs that mimic real-world performance but where no particular engine is a 100% copy of a real-world engine. It's designed for the universe I describe in my Mission Reports series. Because I'm not constrained by needing to duplicate the look of realworld engines, RftSEngines does support Squad engines and many others. Many engines have their sizes, masses, and roles changed quite a bit.

Edited by NathanKell
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Q: How do I add RF tank support to a part / edit a TANK_DEFINTIION?

A: See this helpful guide by TaranisElsu.

Q: My engine doesn't have fuel / my tanks are empty!

A: in RF v4, because each engine is liable to have its own mixture ratio, tanks default to empty of all resources. You must fill them once you place them.

Q: My RCS doesn't work!

A: RCS is now also modular, and most RCS fuels need fuel crossflow. Make sure you (a) set your RCS thrusters to desired mode, (B) filled a tank with the appropriate resource, and © have a fuel feed from the tank to the RCS. If you placed a radial engine where the RCS thruster is, and it would get fuel, then you have a fuel feed. If not (for instance, the path goes through crossfeed-disabled parts, or the tank is radially mounted without a fuel line) then the thruster won't get fuel.

Q: What happened to LiquidFuel and SolidFuel?

A: In RF v4, the only stock resource used in SolidFuel; LiquidFuel is no longer pulling duty as Kerosene/RP-1; instead I have added a Kerosene resource. I have not yet added different solid-fuel resources, however, so all solid fuel parts will need approximately 4.2315x as much SF as they had before to have the same total mass of solid fuel.

Q: How do I configure this for a non-rescaled solar system?

A: RF is designed for real-world performance. Engines and tanks in stock KSP (and stock-balanced mods) perform much worse than their real counterparts; engines are about 3.2x as heavy for their thrust and role, and tanks about 4x as heavy (in terms of dry mass). This means that if you use RF on a solar system with Kerbol-level deltaV requirements, you won't need much rocket. There are two solutions for this. First, you can use KIDS to rescale the difficulty. If you want to need real-life-size rockets, use .3333, .3333 multipliers; if you want something closer to a stock KSP experience, use a higher (but less than 1.0) multiplier for each. If you just want something like a stock KSP experience (with heavier engines and tanks), then open RealFuels/RealSettings.cfg and find useRealisticMass = true and change the true to false. You will get approximately stock-KSP-level performance out of your engines and tanks.

Q: How come my nuclear engines are so bad?

A: They do mass somewhat more than they used to (well, only at low tech levels), but they have a higher specific impulse even at lower tech levels than they did in stock KSP. However, what's changed is that fuels now have realistic densities. This means if you use a NTR in its default fuel mode (Liquid Hydrogen), you will need to pack a gigantic volume of fuel. That's because LH2 has a density less than 1/14 what you're used to, so to pack the same mass of fuel (and mass, not volume, is what matters in rockets) you're going to need 14x as much tankage. If you want to compare the performance of a NTR with a chemical engine, make sure you compare total fuel mass, not fuel amount, and make sure that you have a good (full/empty) mass ratio. Since NTRs are much, much heavier than chemical engines, if you only need a little delta V, it can make more sense to go chemical, since the better mass ratio of a chemical engine and its fuel will win out over the higher Isp of the NTR. However, for large delta V requirements (where you're talking, say, 5km/sec or more) then an NTR is a great choice, since you only need your dry mass * 82% in fuel to get 5km/sec delta V with a low-end NTR, whereas for hydrolox you need 215% your dry mass in fuel. The figures for kerolox or storables are even worse.

Both these issues are hidden in stock KSP, where, unlike the chemical engines which have about 1/4 the TWR of real engines, the NTRs have about the correct TWR for modern engines (or a full 3x what they should for 60s-era), and where NTRs use the same (density) fuel as chemical engines. So if you load up an existing craft, your mass ratio will plummet both due to the lower density fuel (less mass of fuel) and the heavier NTR. Add more tanks until the total mass is about what it used to be, and you should see somewhat similar performance, unless you only wanted a little bit (1-3km/sec) of delta V.



*Kerosene aka RP-1) and LOx is the "standard" / "benchmark" mixture. It's what the early launchers used, and what many still do. It's non-toxic, quite dense, and the LOx is only mildly cryogenic, which means LOx boiloff is not a big issue except for weeks+ missions. For all these reasons, RP-1/LOx is the fuel of choice for lower stages.

*Liquid H2 and LOx is a high-performance mixture. It gives you more "bang for your buck" but it's less dense so you need more tanks (though the tanks are lighter per liter). However, engines burning LH2/LOx generally have a lower TWR than other engines (in MFS, 75%). Also, it is generally less efficient at sea level (proportionally) than other fuel mixtures. The main complication however is that LH2 must be kept extremely cold; boiloff is a serious issue even in insulated (cryogenic) tanks. You should always use cryogenic tanks with this mixture; they mass less for hydrolox than do regular tanks. Given these advantages and disadvantages, LH2/LOx is best for upper stages that are fired during the launch or a few days after; however, some lower-stage use has been done (Delta IV, Ariane 5, Shuttle / Ares / SLS) though often in combination with solid boosters.

*Liquid Methane and LOx is midway between RP-1/LOx and LH2/LOx: lower performance than hydrolox but denser, and less cryogenic.

*Various hypergolics. They are various nitrogen-based storable (but highly toxic) liquid fuels. They perform less well than RP-1/LOx (about 95% the specific impulse for modern hypergolics), but are slightly denser and non-cryogenic: they can be stored for months at a time. Given their advantage in density, in actual use they are better than 95% as efficient--tankage for them masses much less. Further, another key advantage is that they do not need ignition: hypergolic means that if the two substances are put in contact, they will burn with no outside trigger. N2O4 is the highest-performing oxidizer; MMH and Aerozine-50 are the highest-performing fuels (UDMH is more stable but has slightly worse performance). Other oxidizers (Nitric Acid, Nitrous Oxide) have lower performance, especially when used with a mixture of Amines rather than a hydrazine derivative like MMH, AZ50, or UDMH. N2O4 and MMH (or another fuel) is often used for high-performance bipropellant RCS (Gemini, Apollo, Shuttle, etc.).

*Kerosene and Hight-Test Peroxide is hypergolic when the HTP is heated and run over a catalyst bed. It's storable, non-toxic, very dense, but has lower performance than kerolox.

*Alcohol (75% Ethanol, 25% Water) and LOx was used before kerolox; it is worse in just about every respect compared to kerolox.

*Hydrazine, Nitrous Oxide, and HTP can be used as monopropellants. Hydrazine has by far the highest performance, but is very toxic.

*Solid Fuel is very dense, allows high thrust (since there is no engine per se to feed the fuel through, just a nozzle), but has low specific impulse, only slightly better than Hydrazine monopropellant. However, it took many years to develop larger and larger solid fuel motors, and solid fuel motors don't scale as well as liquid fuel (since the entire casing must resist the pressure of combustion, the casing itself forming the thrust chamber).

====Nuclear (Liquid Fuel)====

In general: the less dense the fuel, the higher your specific impulse and the lower your thrust.

*Liquid Hydrogen is the benchmark. Highest performance, but least dense. Same drawbacks as hydrolox, above, except worse, because ALL the fuel is liquid hydrogen

*Liquid Methane has lower performance, but is much more dense and so, despite, the lower specific impulse, the lower tank mass often leads to higher total deltaV for your stage. Considerable increase in thrust.

*Liquid Ammonia has lower performance but also less of a thrust increase than Liquid Methane.

*LOx-Augmented NTR: This involves pumping LOx into the nozzle along with the expelled, superheated LH2, thus having them combust. Thus you get a hybrid between a chemical rocket and a NTR. Massive thrust increase (8x or so) with a drop in efficiency down to about 65-70% what the NTR gets in pure-LH2 mode.



(Note: All tanks are pressurized, but some tanks are highly pressurized; you need the latter for pressure-fed engines.)

* Default: Your regular tank type, roughly equivalent to the tanks used for Titan or Saturn I/V. Note that in order to match Titan tanks, it's lighter than it should be for other cases. Features minimal insulation for cryogenic resources (equivalent to the insulation on Saturn V's S-IVB).

* Structural: A heavier version of Default, used for aircraft/spaceplanes (or to simulate old, massive tanks). Example: A jet plane's tank, or the R-7's.

* ServiceModule: Used for service modules and other pressure-fed tanks. You need this for pressure-fed engines (RCS are pressure-fed engines). Due to supporting up to 200atm of pressure rather for resources than just the 1.8 or so that non-highly-pressurized tanks do, it's much heavier. Also can store electricity and life support resources. Features more insulation for the cryogenic resources. Examples: Able/Delta upper stage, Apollo Service Module.

* Fuselage: A heavier version of ServiceModule, used for aircraft/spaceplanes (or to simulate old, massive tanks). Examples: the electronics and life support section of a spaceplane, the WAC Corporal sustainer.

* Cryogenic: Highly insulated tank. Has the level of insulation (and low boiloff) of a modern cryogenic tank. Slightly heavier than Default due to the increased insulation. Example: Delta IV Common Core Booster.

* Balloon: Light, fragile tank. In real life the tanks must be kept pressurized at all times (even when empty of propellants) or they will collapse, and if left unmonitored they can collapse. In addition they are much less strong than other tank types, and one cannot attach heavy things to their sides or place heavy masses above them under high acceleartion. Ingame, however, their only major disadvantage is that they cost more. Example: Atlas sustainer (pre-Atlas III).

* BalloonCryo: Same as Balloon, but with more insulation (to the level of type Cryogenic). Example: Centaur upper stage. The Shuttle ET falls in between this and type Cryogenic.



In order to have realistic engine performance, RF divides engines into types and tech levels. While type cannot be changed in game (it is determined by chamber pressure, area ratio, cycle type, etc., all abstracted as "engine type" and applied, as well as can be done given how unrealistic most KSP engine models are, to most stock and mod engines), tech level can. Tech level represents the advances that are applied to a specific model of engine over time.

For example, the venerable LR87 used in the Titan rocket went through upwards of 11 revisions over time, and was converted to use all three main fuel types (kerolox, i.e. kerosene [RP-1] and Liquid Oxygen; hypergolic NTO / Aerozine-50; and hydrolox, i.e. Liquid Hydrogen and LOx). Its Isp and thrust-to-weight ratio increased considerably through the revisions.

Terms: SL = sea level, TWR = thrust to weight ratio. Note that in RF, all engines include the mass of their thrust plate, so RF TWRs will be about 20-30% lower than real life engine stats.

So, first RF classifies each engine it supports by type. The types are:

O = Orbital maneuvering system. Designed for tons and tons of restarts, and vacuum-only use. Pressure-Fed. High vac Isp, very poor SL isp, lowest TWR. Usually hypergolic. Real life examples: Apollo SPS, Shuttle OME. KSP example: LV-1

U = Upper stage. At most a couple restarts. Same Vac Isp as O, better SL Isp, better TWR. Real life example: the Titan's LR-91. KSP example: KR-2L Rhino.

U+ = Upper stage optimized for vac use. Aka "O with a turbopump." Highest Vac Isp (higher than O). Lower TWR than U. That's what + means, higher vac, lower SL, lower TWR. Real life examples: the Centaur's RL-10. KSP examples: LV-909, Poodle.

L = lower stage. No restarts. Lowest Vac Isp, highest SL Isp barring Aerospike, highest TWR. Real life examples: RD-170 and 180 on Zenit and Atlas V. Fuel is usually kerolox, though could be hypergolic or even hydrolox. KSP example: the Mainsail, obviously.

L+ = same changes as U+: higher IspV, lower IspSL, lower TWR. Designed for a single-stage-to-orbit stack (or at least an engine that's never staged away even if boosters are). Real life example: Space Shuttle SSME. Note that in real life most rockets have large lower stages and small upper stages, so most real life lower stage engines are somewhere between L and L+, if not outright L+. KSP example: LV-T45, Skipper.

A = Aerospike. Note that in real life nozzle losses are only 15% or so, and most of the efficiency loss at sea level is because there's air there, not because the nozzle is the wrong shape. For now they have the Isp of a U in vacuum, and 0.9x that at sea level. Real life examples: J-2T-250k (plug nozzle mod of the Saturn V J-2), the linear aerospike on the X-33. KSP Examples: obvious.

S = Solid.

S+ = Solid for vac use, lower SL, higher Vac Isp.

N = Nuclear Thermal. Approximately same ratio of IspV to IspSL as U. Uses a solid core reactor to heat reaction mass. Very low TWR, very high Isp. Real life examples: the various Project NERVA engines, RD-0410. KSP example: LV-N.

NOTE: RCS uses type 'L' for the Isp and TWR multipliers; in terms of actual performance it's like O.

What Isp an engine has is determind by grabbing its type, checking its tech level, and getting the appropriate entry in the TLTIsps area of RealSettings.cfg. Then any appropriate multipliers are applied (in the engine CONFIG).

Engines have minimum tech levels; they aren't available before that. You can, however, upgrade past that. In fact, you are HIGHLY encouraged to upgrade any engine, after placing it in the VAB, to your maximum available TL. Engines default to the lowest TL they can.

Rough TL to year table:

TL0: 1945-1955, WW2 and early rocketry.

TL1: 1957+, early Space Age rockets (straddles the divide between Redstone/Vanguard/R-5, and Atlas/R-7).

TL2: 1962+, Gemini and Saturn I (not IB), Voskhod/Molniya.

TL3: 1967+, Apollo

TL4: 1968+, Apollo Applications Program, N1, etc.

TL5: 1978+, Shuttle etc.

TL6: 1985+, the Shuttle era, 80s and 90s LVs.

Tl7: 2005+, the present day.



It can cost funds or science to unlock an engine config and/or increase the tech level. Upgrade costs are controlled by global settings and by per-part settings. In general, it costs a fixed amount of funds and/or science to unlock an engine config, and it costs a fixed amount of funds and/or science, times (desired new tech level - original engine tech level) to unlock a new tech level (so going from TL3->4 is less expensive than 4->5 for a starts-at-TL3 engine).

CONFIG settings:

If a CONFIG has an entryCost, that will be its cost in funds to unlock. If it has a sciEntryCost, that will be its cost in science to unlock. If it has a techLevelEntryCost, that will be the base cost in funds to unlock a new TL (see above re the per-TL costs changing), and same for techLevelSciEntryCost. Per-config entry costs can also have multipliers and subtractors. This means if one CONFIG is very similar to another CONFIG (on that or another engine), you can get a reduction in cost if you've unlocked the other CONFIG. You can add a entryCostMultipliers {} node to the CONFIG and have a list of the other config(s)' names and their multipliers, like LR89-NA-6 = 0.5 (which will mean the current config costs only half as much to unlock if LR89-NA-6 is unlocked). This applies to both funds and science. You can do the same with the entryCostSubtractors {} node, except in this case, the value is subtracted from the final cost, rather than the final cost being multiplied by the value. In this case, the subtractive value will be multiplied by configCostToScienceMultiplier if the cost is a science cost (see below for configCostToScienceMultiplier).

Global settings (configs):

configEntryCostMultiplier: if no specific costs are set, then config entry cost will be (this * config.cost). So if the config has no extra cost (or a negative cost), the entrycost will be 0. Default 20.

configScienceCostMultiplier: Works like above for creating the science entry cost. Default 0.

configCostToScienceMultiplier: Used when subtracting from a config unlock science cost based on other unlocked configs. See above. Default 0.1.

Global settings (techlevels):

techLevelEntryCostFraction: The fixed cost in funds for unlocking a new techlevel for a CONFIG, if it is not specified in the CONFIG (see above), is based on the this times the sum of the config entry cost and the part's entry cost. Default 0.1.

techLevelScienceEntryCostFraction: The fixed cost in science for unlocking a new techlevel for a CONFIG, if it is not specified in the CONFIG (see above), is based on the this times the sum of the config's science entry cost and (the part's entry cost times configScienceCostMultiplier). Default 0.

usePartNameInConfigUnlock: If true, the part name will be prepended to the config name when checking for whether configs are unlocked. If you tend to use the same name for configs across multiple engines (i.e. both Mainsail and Poodle have `LqdOxygen+LqdHydrogen` configs) you want this true. If you are RO and each CONFIG represents a specific engine (and multiple parts may implement the same engine) you want this false. Default true (but RO sets it to false).



RealFuels now integrates limited ignitions and support for ullage and pressure-fed engines.

* To start an engine, you must have the resources it requires to start, and you must have ignitions remaining.

* If ullage is enabled for the engine, and your propellant stability is not "Very Stable", there is a chance that vapor can get in the feed lines and the engine will flame out. You will need to set the throttle to 0 to reset things, then stabilize your propellants. Some forward RCS thrust, or thrust from ullage motors like small SRBs (solids and RCS aren't subject to ullage issues) will do that. Then you can try throttling the engine up again to restart it.

* If the engine is pressure-fed, it requires highly-pressurized tanks (see above for tank descriptions). It will not ignite and run without such tanks.

New parameters in ModuleEnginesRF:

ullage: Whether ullage simulation is enabled. Defaults to false.

pressureFed: Whether the engine is pressure-fed. Defaults to false.

ignitions: the number of ignitions the engine has. Defaults to -1 (unlimited).

IGNITOR_RESOURCE nodes: If you specify limited ignitions, an engine will consume these resources when it ignites, and will fail to ignite (but still use up an ignition) if they are not available. name defines the resource name (like ElectricCharge) and amount defines the amount required (just like EngineIgnitor).

Note that if you used to configure Engine Ignitor per-CONFIG in RF, those configs are still compatible. You only need to worry about the above parameters if you don't have ModuleEngineIgnitor {} nodes in you CONFIG nodes.

Edited by NathanKell
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Excellent work but perhaps with things seeming to get more complicated as far as the number of mods go maybe you could include all the realism based mods (RSS,DRE,MFS,RF,RT2,and RO) In a single realism pack (probably included as part of realism overhaul) and already configured for realism with a single master config. I just thought it would make things easier for you but obviously up to you.

Edited by Zander
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Awesome, finally out :) However, i'm not playing with Realism Overhaul and real solar system, so i want to use real fuels, but with stock engine and tank masses. When using the stockalikes engines config the engines are a lot lighter than in the stock game, the mainsail is 1.875t instead of stock 6t for example. And i don't see any engines that can use any other fuels than LOx/liquidfuel, LOx/LH2 and MMH/N2O4, though i can still fill the tanks with any fuel i want. Maybe i've done something wrong, or have i just misunderstood what the stockalikes config is supposed to do? Regardless, awesome work :)

Edited by shabbycow
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w00t! Thanks a lot for the update man

A request, could we have support in the future for this mod? It adds - among other things - some very nice tank textures...C:


Edited by Dante80
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Quick question as this is a little confusing: From you engineconfig RealismOverhaul downloads, do I only need to copy the engine config file(s) to the realfuels folder and if so, what are the names of the files I'll need to copy.

Also, if I have the entire RealismOverhaul mod already, aren't the files there already used or do I need to copy them anyways?

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Thanks folks :)

Zander: To be clear, you need RF, *not* MFT. MFT is there if you used to use MFS-nonRF, i.e. you just want modular fuel tanks for stock resources.

Yes, a pack is planned.

shabbycow: set useRealisticMass to false in RF/RealSettings.cfg

The "stock" MFS3.3 engine configs were made for MFS3.3 and thus don't use any of the new features or resources from RF v4. Hopefully Chestburster (or someone else? Volunteers?) will make a new set of "stock" engine configs using the new features and resources.

Dante80: Nertea and I were going to work on NFPP compatibility but we both got busy. I'll check in regarding that.

Zappa: In case of either RO download, it's a download of the full RO package. Delete your existing RO folder, then extract the one from the package (I haven't released v3 yet; these are preview builds of it that take advantage of RFv4 features). That's all you need to do.

AbeS: Neither RftSEngines nor RealEngines yet include Engine Ignitor configs; they will shortly. RFv4 supports the support of EI, if you will.

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you would get some OP and underpowered engines like that, not sure the current tweaks without rescales would be convenient.

No you wouldnt. The rescaling is a purely visual change, and it should be done to either all the parts or none of them. RO currently ruins many designs by not having things fit together. Actually, you can't tell the size of something in KSP except by comparing it to other parts. Therefore resizing things to real life size accomplishes nothing.

I, too, would like a version with no size changes, just changes to mass and thrust and so forth.

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It is just visual, but not really...

For example the NP 5m Bearcat with Real Engines it has a thrust of 38870 KN. With the rescale is has a diameter of 10 meters, using it with just a full 10m x 20m tank you still have a really big TWR. Imagine using that same thrust but with a 5m engine, you would need a tank of 5m x 80m (assuming it has the same densities) which is insane!

I'm not saying it is bad to get some configs that don't rescale the engines, but the existing configs need the rescales for their stats otherwise it won't make sense. I think that's what Nathan meant by a stock like configs

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ZacAttack42: You understand there's this thing called ballistic coefficient, right? KSP parts have the mass of their real-size equivalents despite being smaller. That means unrescaled parts have FAR less drag than they should. This changes ascent profiles and (much more importantly) can really mess up reentry.

So no, it is _very_ far from a purely visual change.

EDIT: Yup, AbeS has it. If you just want "engines with nifty new fuel modes" use the Stock-MFS engine config. Realism Overhaul doesn't make sense without using real-scale.

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set useRealisticMass to false in RF/RealSettings.cfg

This only changes the fueltank masses though, engines remain the same. Is there another setting i've missed? Or is it more work than that? I took a look at various files and looked for other settings that seemed relevant, concluded that i have no idea what i'm doing and gave up :sticktongue:

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Ensure A) you have the correct download and B) an engine configuration (posted in the second post just under the original post). Works fine on my modded installation with B9, KW Rocketry, AIES, KSPX, KSPI, Fatman NTRs, Spherical/Toroidal Tanks, SDHI service module, and stretchy tanks. I have approximately a dozen or two more mods but none that include parts that would be affected by this mod.

@Nathan, regarding naming conventions; should Ammonia be LqdAmmonia or Ammonia?

Pre-edit edit: Helps to not think about diluted household ammonia when talking about rocket fuel. Nevermind!

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Yea I had a brain-fart while I was thinking about it for a second and my fingers were typing faster than my single operational brain cell was functioning.

I just loaded up every tank from KW's newest release in the VAB; They're all functioning correctly on my end with regards to tank volume and bringing up the RF GUI.

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