Modular Fuel System Continued v3.3 (OBSOLETE)

[Starwaster]

Thank you for your answers, I was aware of the density difference, probably should have said that, but I still don't understand. Why would you go with a lighter, but much larger, more likely to be unstable, rocket? Can someone give me an example where LH2/LOX would be preferable over another mix, other than nuclear engines since they seem to require it? I'm not complaining BTW, this is an awesome mod, and an awesome modder, I just want to know why its there and what I should use it for.

So far in my games I tend to go for the smallest rocket I can get with the most Delta V for whatever payload I may be transporting, mass doesn't matter as long as it can get to where I want it, and LH2/LOX doesn't seem to play well with that way of construction.

It's not about making lighter rockets. It's about making lighter stages.

Look at the Saturn V. The bottom stage used kerosene (RP1) & liquid oxygen (LOX). The upper two stages used H2 & LOX. Did that lower the delta V available to those stages? Yes, it did. But by lowering the mass of the upper stages they increased the delta V of the lower stage because it had less load to bear. Or it also let them increase the payload that could be lifted to orbit.

The point at which you would consider H2&LOX is the point at which you're looking for ways to lessen the load being carried by the stages underneath.

[Starwaster]

I've identified a bug that decreases the dV a bit everytime you change the amount of fuel/size of a fuel tank with the R-key.

It doesn't seem to matter if you decrease or increase the size, the dV drops anyway. And after launching and reverting back to VAB, sometimes the dV drops by a significant amount, roughly half, compared to pre-launch. I also noticed one instance of my TWR being significantly lower (noticeable by the rocket not lifting off properly) than in VAB.

I'm not sure which of the mods is causing this or if it even might be MFS/StretchySRB confusing MJ2, however I did make a KSP_win test folder sans all the irrelevant crap just to confirm this bug.

Mods used:

RealSolarSystem 5.1

ModularFuelTanks 3.2 RFRM

StretchySRB v5

MechJeb 2.1

ModuleManager 1.5

Steps to reproduce:

(SNIP!)

Hope this helps!

Suggest you use the AG editor to look at the tank's dry mass and fuels. Sounds like it's not updating fuel properly.

Use the editor to remove all fuel from the tank then reconfigure for the attached engine. That should serve as a workaround.

Edited November 21, 2013 by Starwaster

[erbmur]

First of all just want to give a big thanks for keeping this mod going!

I seem to have run into an issue though. With this mod installed, engines don't seem to have the orange glow they get after running full power. I have confirmed that it is not an issue with any other mod as the glows re-appear after removing the modular fuel folder from gamedata, and they disappear when i copy the folder back in.

Has anybody else noticed this issue as well?

EDIT: It appears to affect only the smaller less powerful engines, and i'm guessing its due to them just being less powerful and therefore producing less heat.

Edited November 21, 2013 by erbmur

[NathanKell]

Hm. I took a look through the part files and I see your point. The Vesta does meet your criteria, though, in being a 120kN engine at .6mt, coming in at 21:1 (piss poor in real life), but this is actually better than the Wildcat-V.

Yeah, and the Vesta and the Mav-1D have a fair resemblence to the single/dual RL-10.

The real problem of course is that in stock MFS we feel obligated to keep engines' mass and thrust the same, whereas in my own engine work I feel free to change ALL THE STATS so that's where I spend most of my time. But from now on Chestburster is taking over maintenance of "stock" MFS engine stats, so they'll be a bit more like they used to be.

(For a taste of how I see all the engines, see KATO-Engines or its successor, coming soon, RftS-Engines)

Savage117, it all comes down to mass. Do you get more dV, or less, for the same total mass (engine+tank+fuel)? The answer for hydrolox is "way more dV". Even if you're not using cryogenic tanks. If you are, then it's way, /way/ more.

Note that just because a tank is the same size doesn't mean it'll mass the same; a jumbo-64 containing LH2/LOx will have lower dry mass than one containing RP-1/LOx. Even though the total tank volume is the same (LH2 tanks are lighter per unit of volume).

Now you might think, jeez, all these giant tanks mean so much drag loss! Well, drag losses are very minimal, so you at most might lose 50m/s from switching your entire launcher from kerolox to hydrolox (WAG). On the other hand, you probably have 1.25x the delta V now, for the same mass. You do the math.

Finally another advantage of Hydrolox (in MFS) is that while the Isps ferram cites are available early on with Hydrolox (TL2/3), it takes until TL6 or so for kerolox to get those figures, so you're better off comparing hydrolox's 380-450s to kerolox's 270-340s. Much bigger increase then.

MAKC: Because MFS rounds fuel quantity, and ST rescales in itty-bitty chunks (1% at a time), rounding errors add up during scaling. When you have approximately the right size tank, go into the tank editor, and remove and re-add your MFS fuel tanks; that will correct the ratios. The way it works internally is this:

MFS normally rounds fuel quantities (to 4 sig figures, or to the nearest integer if > 1000). When you start rescaling a ST, rounding is turned off, but the rounded ratio (not the correct ratio) is the starting point. When you move your cursor off the tank, quantities are rounded again. That means you get rounding errors twice, but it's the price you pay for nice numbers in MFS. I'm considering turning rounding off entirely, however, since AFAIK most people who use MFS use ST, and does it really matter if your amount of fuel isn't a nice round number?

erbmur: Ah, try changing the heat multiplier in MFS/RealFuels/RealSettings.cfg

So that your engines don't overheat (who designs engines that overheat!?) I turned down heat production. But the emissive texture is tied to heat production...Your edit-guess was entirely correct.

(lower-TWR engines I made produce less heat proportionally.)

What I should probably do, since the heat mechanic is silly, is just use heat production to tailor the graphics.

[sephirotic]

I can understand the point of the much lighter and optimal ISP of LH2+LOX for upper stages and escape-burn stages. It is also very useful if you want to simulate a mining mission like one of the proposed Mars missions to send empty tanks to mars to mine LH2 +OX on ice caps for a return vehicle.

I don´t see, however, any advantage in all possible designs i could come with for a interplanetary mission to Jupiter (RSS), where NERVAs would be advantageous.

Yes, you gain advantage in mass per d/v unit, but the volume is so much higher than a RP1 or even LH2+LOX that to get the same d/v in a interplanetary booster module with a NERVA, you will need so much more orange rockomax 64 tanks that i simply can´t put pratically into orbit easier.

I haven´t made many precise calculations, but so far:

1 Single orange rockomax 64 tank + a LH2/O2 poodle engine:

12,88t - 10065 m/s

Same engine, RP1+LOX layout:

34,48t - 10133d/v

A reasonably light payload in both cases with a fairly good amount of D/V for a interplanetary travel.

You can clearly see the advantage of LH2+LOX, even tough less atoms are carried for the same volume(in pratice, the SAME sized vessel) they deliver pratically the same level of d/v with almost a third of the mass. Great. The much lighter layout also means you can either use a smaller lifter rocket design, or by using the same for a heavier payload, could put you in a higher orbit and in the end sending you further and giving more D/V for the overall mission.

However, even the heavier RP1 per m3 version, can be launched without so many overengineering in a single launch. IT still serves it purpose without boilling off being so much of a issue.

Now NERVA and LH2 is a whole different matter: For designing an interplanetary booster that even comes close of the same level of d/v (perfomance) of the previous setting, i would need something like a 5 rockomax 64 (a center tank with another 4 radially attached ones) with doen´t even come close to the LH2+LOX setting:

Exact same vessel with a nerva engine and filled with LH2 (1 rockomax 64tank):

5.39tons, 4485 d/v

Yes it's lighter, but mass vs D/v per see is hardly significantly better than the LOX+LH2 configuration. We are looking at 781m/s per ton of d/v for the LOX+LH2 setting, and 832m/s per ton of d/v for the NERVA+LH2 only layout. It's a gain of d/v that i hardly believe in the ends presents any advantage since it would have to have much larger palyoad vessels that would actually needs over-engineering for the lifter and gives much more drag, specially with far in the ascension to orbit stage.

I love all these realism mods, but they killed the NERVAs, i wonder if they were that much impractical IRL?

I am considering the idea of boost the ISP of the NERVAs to 910s, the same as the Russian RD-0410. Tough I do realize it had a worse TWR witch would imply in worsen performance.

Edited November 21, 2013 by sephirotic

[Starwaster]

First of all just want to give a big thanks for keeping this mod going!

I seem to have run into an issue though. With this mod installed, engines don't seem to have the orange glow they get after running full power. I have confirmed that it is not an issue with any other mod as the glows re-appear after removing the modular fuel folder from gamedata, and they disappear when i copy the folder back in.

Has anybody else noticed this issue as well?

EDIT: It appears to affect only the smaller less powerful engines, and i'm guessing its due to them just being less powerful and therefore producing less heat.

Probably because overheating was toned down. If they don't heat up there's nothing for thermal animationnto grab onto

[NathanKell]

KSP NTRs (You don't call all hydrolox engines J-2s or SSMEs, right? NERVA was a NTR*) are more or less correct in their TWR, though a hair low in Isp. TWR is around 1.8-2.5 for small NTRs, IIRC.

Also, you really should use StretchyTanks, and KJR. Then the size of the thing doesn't mean lotsa-parts or wobble, just "more mass."

You need to compare the same total mass ratio in a nuclear and non-nuclear stage; only then will you get a good comparison. Comparing a rocket with a mass ratio of, what, 10:1, to one that's about 2:1, is _not_ a good comparison.

*Apologies; this isn't directed at you per se. I'm just really tired of people using NERVA like it's the same thing as NTR, instead of a project name/name of a few engines (NERVA Alpha, Gamma, 1mlbf, etc).

[Starwaster]

Bottom line is, you need multiple or bigger tanks of H2. Thats common sense really, I think you even answered your own question.

Yes that is how it would be IRL.

No, not everyone agrees nuclear is the way to go, (IRL. Zubrin for example)

Regardless, you cant expect a fair comparison using a single tank. An NTR vessel wouldnt have the same design, not with H2; its Isp is double that of a chemically fueled rocket; Isp governs how much thrust you're getting per kilogram which is mass. but at a fraction of the density of course you need to compensate with more H2.

Keep in mind, too that the nuclear engines are still using stock values which in turn are based on prototypes that never flew. Production versions would have had better performance, both Isp and thrust.

Edit: @Nathan, 111 and 333 KNt of thrust are well in the capabilities for NTR and somewhat higher Isp too. (NERVA figures for both were based on 2500K - 2700K chamber temps. If you go a bit higher to about 3000K it gets better)

Edited November 21, 2013 by Starwaster

[sephirotic]

Of course i realize comparisons should be done by factor of mass, but volume can´t be completely disregarded since larger volumes influences in drag and balance of a rocket design.

ANother VERY important factor in detrimental to NTR's is it VERY LOW TWR. (i do know nerva was the name of a solid-type, NTR, everyone keeps calling NTR nervas in the forum and i got the bad habit from then, don´t worry, i understand your feeling and the difference, specially because the NERVA was never actually put into a functional rocket, whereas the much less famous RD0410, did, witch it should receive more merit for.)

Regardless, you cant expect a fair comparison using a single tank. An NTR vessel wouldnt have the same design, not with H2; its Isp is double that of a chemically fueled rocket; Isp governs how much thrust you're getting per kilogram which is mass. but at a fraction of the density of course you need to compensate with more H2.

I'm not completely noobish when it comes to rocket science i know more than the basics such as ISP. (tough i'm not really that great with math, i admit that much).

ISP isn´t all that matters for rocket engines. In fact, the amount of d/v a REAL vessel can have is a direct relationship of the % of fuel mass vs engine weight + structural and payload weight. By having a heavier engine with higher ISP you automatically diminish it's ISP advantage. So, by changing the Engine's TWR to more realistic weights, (the poodle witch i used for comparison, previously, was configured to 0.614 tons, 266TWR) you are also affecting the amount of d/v you can achieve with the same payload and fuel.

So the NTR isn´t actually 80% better than the Poodle (80% higher ISP) it is hardly 20% better. (I don´t really know if the influence ofTWR vs ISP is linear so I am only doing an aproximation here).

Since you didn´t like my previous comparsion where i wanted to keep the same design AND STRUCTURAL MASS unchanged to only evaluate the influence of the engine used, here is a new comparision taking in account more pratical design´s for the NTR for a given goal of D/V:

NTR: 12.79t - 9473d/v - 740ms per tonne

POODLE: 13.52t - 10077m/s 745ms per tonne

So the poodle has actually a HIGHER d/v per mass and payload, since it has LESS structural and ENGINE mass % than fuel!

Not to mention less drag due to less volume.

I can hardly see any advantage in using the NTR as it is. I guess i'll try tweaking the .cfg of the RealFuel folder to give the NTR the same d/v of the RD0410 - 910s. Maybe i'll even push it a little bit further, to 1000s to see if starts to compensate more.

Edited November 21, 2013 by sephirotic

[Starwaster]

Of course i realize comparisons should be done by factor of mass, but volume can´t be completely disregarded since larger volumes influences in drag and balance of a rocket design.

ANother VERY important factor in detrimental to NTR's is it VERY LOW TWR. (i do know nerva was the name of a solid-type, NTR, everyone keeps calling NTR nervas in the forum and i got the bad habit from then, don´t worry, i understand your feeling and the difference, specially because the NERVA was never actually put into a functional rocket, whereas the much less famous RD0410, did, witch it should receive more merit for.)

If it never flew I wouldn't call it functional. They had plans for it maybe, just as we did for ours. No more than that.

I can hardly see any advantage in using the NTR as it is. I guess i'll try tweaking the .cfg of the RealFuel folder to give the NTR the same d/v of the RD0410 - 910s. Maybe i'll even push it a little bit further, to 1000s to see if starts to compensate more.

I suggest checking out out the RF config in my signature. It was designed primarily to beef up the NTR a bit, including alternate fuels. They're not limited to hydrogen. (keep in mind though that the MFSC version isn't fully tested, it was finalized for MFS and converted to MFSC and might have mistakes)

[Goozeman]

I can understand the point of the much lighter and optimal ISP of LH2+LOX for upper stages and escape-burn stages. It is also very useful if you want to simulate a mining mission like one of the proposed Mars missions to send empty tanks to mars to mine LH2 +OX on ice caps for a return vehicle.

I don´t see, however, any advantage in all possible designs i could come with for a interplanetary mission to Jupiter (RSS), where NERVAs would be advantageous.

Yes, you gain advantage in mass per d/v unit, but the volume is so much higher than a RP1 or even LH2+LOX that to get the same d/v in a interplanetary booster module with a NERVA, you will need so much more orange rockomax 64 tanks that i simply can´t put pratically into orbit easier.

I haven´t made many precise calculations, but so far:

1 Single orange rockomax 64 tank + a LH2/O2 poodle engine:

12,88t - 10065 m/s

Same engine, RP1+LOX layout:

34,48t - 10133d/v

A reasonably light payload in both cases with a fairly good amount of D/V for a interplanetary travel.

You can clearly see the advantage of LH2+LOX, even tough less atoms are carried for the same volume(in pratice, the SAME sized vessel) they deliver pratically the same level of d/v with almost a third of the mass. Great. The much lighter layout also means you can either use a smaller lifter rocket design, or by using the same for a heavier payload, could put you in a higher orbit and in the end sending you further and giving more D/V for the overall mission.

However, even the heavier RP1 per m3 version, can be launched without so many overengineering in a single launch. IT still serves it purpose without boilling off being so much of a issue.

Now NERVA and LH2 is a whole different matter: For designing an interplanetary booster that even comes close of the same level of d/v (perfomance) of the previous setting, i would need something like a 5 rockomax 64 (a center tank with another 4 radially attached ones) with doen´t even come close to the LH2+LOX setting:

Exact same vessel with a nerva engine and filled with LH2 (1 rockomax 64tank):

5.39tons, 4485 d/v

Yes it's lighter, but mass vs D/v per see is hardly significantly better than the LOX+LH2 configuration. We are looking at 781m/s per ton of d/v for the LOX+LH2 setting, and 832m/s per ton of d/v for the NERVA+LH2 only layout. It's a gain of d/v that i hardly believe in the ends presents any advantage since it would have to have much larger palyoad vessels that would actually needs over-engineering for the lifter and gives much more drag, specially with far in the ascension to orbit stage.

I love all these realism mods, but they killed the NERVAs, i wonder if they were that much impractical IRL?

I am considering the idea of boost the ISP of the NERVAs to 910s, the same as the Russian RD-0410. Tough I do realize it had a worse TWR witch would imply in worsen performance.

The trick with nuclear engines in real life is that the tanks have absolutely absurd mass ratios. Because LH2 is so sparse, the tank can have a very thin wall (~1mm for 10mx30m tank made of titanium alloys.) With a basic support structure and some piping included, such an LH2 tank can have a mass ratio of 30-50:1 or better, much better than the BOTs in KSP (9:1). Mind you, such a tank cannot take significant axial load, so it cannot be used as a lower stage, but it works great if you put a couple in space and then dock them to an interplanetary stage.

As far as Nuclear engines go, the best ever designed was a more recent PWR engine with a TWR of 5:1 and an ISP of 950s. NERVAs (the actual project) tested to ~820s with a 3.5:1 TWR. 1000s or so is about the limit for current material science tech.

[Savage117]

Thank you all for your answers, especially you NathanKell for taking time out of all your projects.

I didn't expect to start such a heated debate, sorry about that. Thanks to all your answers I now have a pretty good idea of what to use Hydrolox for.

But another question came up while reading your posts. I am aware that certain fuels require insulated fuel tanks, but how do we know which ones are insulated? The only tank I know is insulated is the Orange Rockomax 64, haven't got it in career yet with MFSC installed, but none of the other tanks before it have any indicator on whether they are insulated or not, that includes stretchy tanks, which I have been using the most.

Thank you all for your time.

[NathanKell]

NP.

If the tank says "Tank type: Default" when you mouseover it in the parts list then it has only minor insulation. If it says Cryogenic, then it's insulated.

[BrickedKeyboard]

Ok, I'm trying to figure out how to use "Real Fuels".

The problem is, I go to the GUI for an engine and choose a higher tech level. The tech level displayed does not update.

Furthermore, I have to choose the engine tech level for every single engine in the game when I place it? There is no way to click somewhere to say "I am now tech level 2"? Or am I missing something somewhere. There appears to be no documentation.

[Starwaster]

Ok, I'm trying to figure out how to use "Real Fuels".

The problem is, I go to the GUI for an engine and choose a higher tech level. The tech level displayed does not update.

Some of the engines don't always have TL increases, not sure if that's deliberate or not. Which engine were you trying to modify the TL of?

Furthermore, I have to choose the engine tech level for every single engine in the game when I place it? There is no way to click somewhere to say "I am now tech level 2"? Or am I missing something somewhere. There appears to be no documentation.

Currently yes, you do. I think Nathan at some point intends to tie it into the R&D....

[NathanKell]

Yes, I do intend to key it to nodes. I've been...a bit busy of late, for obvious reasons.

I second Starwaster's question: Which engine, which version of MFSC (RF? RFRM?), and if you click and click and nothing happens, upload the output_log

[NathanKell]

Changelog:

v3.3 = \/

*Swapped how thrust and mass are changed by TL increase.

*Made the battery multiplier (how much charge per unit of volume) configurable in MFSSettings

*Changed Xenon around. Tanks now hold 1/10 what they used to, and Xenon is now 10x as dense. It's kept pressurized at a hopefully reasonable temperature to yield that 0.2 g/cc density (what I've set it to).

*Changed tank masses again to try go get them ever closer in line with the real world.

*Added Balloon tanktype (practically no basemass; structural integrity kept by internal pressure). C.f. Atlas missile / LV. Same for BalloonCryo. Since the tank goes all the way to the skin they hold slightly more (at least the StretchyTank ones, the only ones so far, do).

*Fixed propellant ratios so that they are displayed in percents rather than 0.x ratios that get rounded.

*Added tooltips for hovering over autofill buttons to say which engines use that mixture.

*Added SRFirefox's fix for NTRs so nuclear fuel lasts longer. Also increased ElectricCharge generation.

*Added Syntin; changed Methane to LqdMethane to comport with other fuels.

[Guest]

Finally, I can start work on Soyuz-U2 and (later) on Buran. Turns out the latter used Syntin in it's OMS.

[AdmiralTigerclaw]

So I've a question:

Are modular fuel tanks applied to specific mods on a part-by-part basis? (As reffering to the 'supported mods' section.)

Because I can't help but think there should be a way for MFS to identify tanks even when you don't have them 'accounted for', throw their base values into an algorhythm, and spit out the information used by MFS.

[Morrigi]

The link to the realism overhaul release thread in the OP is broken.

[Guest]

Oh, and it turns out I need your calculator updated, Nathan. With turbopump simulation, calculating Syntin loads turned out more complicated than I anticipated.

[Starwaster]

So I've a question:

Are modular fuel tanks applied to specific mods on a part-by-part basis? (As reffering to the 'supported mods' section.)

Because I can't help but think there should be a way for MFS to identify tanks even when you don't have them 'accounted for', throw their base values into an algorhythm, and spit out the information used by MFS.

Tanks need to have the ModuleFuelTank MODULE added to their part configuration. The way part addons work makes that a requirement. Adding the MODULE code is trivial and is done via ModuleManager. If a mod or parts pack is said to be supported then MFS has configuration files that set up those tanks for MFS support.

[dnulho]

I am working on designing a life support mod (see my Sig) and I am wanting to simulate the presence of air by having a total of say 100 units in the Command pod 1. It has 70/100 N2, 28/100 O2, and 2/100 H2 (or whatever else). Does MFS have the capability to say that the total of these 3 resources cannot exceed 100? or would I have to say that there is 70/70 N2, 28/28 O2 and 2/2 H2? If it is the second, what would it take to add this capability to MFS?

Progress,

[Starwaster]

You have to specify amount and max amount for each resource. MFS has no provision to limit their totals other than keeping them from going over max.

to add them you need a TANK_DEFINITION that defines the three tanks you will need for your three resources.

Then you need to define the TANK for each r esource. look in the resource folder for real fuels for examples

[stevron]

Not sure if I should ask in here but is there a .cfg or a guide or something to set the kethane convertors to Real Fuels?