Modular Fuel System Continued v3.3 (OBSOLETE)

[Chestburster]

It happens sometimes on my install too. Try to save and reload your craft, that should solve it.

[Starwaster]

Okay, found a problem. None of the current config packages include a copy of modulemanager.dll. I've tried adding the most recent version manually, however that winds up breaking all SRB symmetry above 2 fold. Only two of the 3+ boosters will appear in the stage in the VAB (No single/numbered icon mixes), and only appear on the launchpad when launching (and not necessarily in the correct stage). That last bit isn't a bug caused by this mod though. It appears to be caused by the most recent version of Module Manager.

ModuleManager does not cause it. Don't know what causes it but it's been around since 0.22 came out.

Here's how to mitigate the trouble that it can cause. Place only one. I.e. don't be in symmetry mode. Make sure that the part is in the stage you want it. Then grab it and press the symmetry key. (as many times as needed if you're not placing it on something already in symmetry mode).

Even though you can't see the other copies they WILL be where you want them in the same stage as the others. I'm confident enough with that system that seldom bother reloading the craft to make sure.

[xandalis]

ModuleManager does not cause it. Don't know what causes it but it's been around since 0.22 came out.

Here's how to mitigate the trouble that it can cause. Place only one. I.e. don't be in symmetry mode. Make sure that the part is in the stage you want it. Then grab it and press the symmetry key. (as many times as needed if you're not placing it on something already in symmetry mode).

Even though you can't see the other copies they WILL be where you want them in the same stage as the others. I'm confident enough with that system that seldom bother reloading the craft to make sure.

Actually, when MM is installed (and any MM dependent mod, I tried different combinations, all caused this problem under MM 1.5), this happens. However if the .dll is the ONLY thing other than the Squad directory in GameData, it doesn't cause the problem. So, it is the current version of MM (by process of elimination). Also, I did try the method you suggested, no dice either. I discovered this after updating from a fresh install, with the most recent versions of the mods I planned to use (and had used successfully in combination before). Procedural Wings came with a 1.5 version of MM and that's when I discovered the problem initially. I've already let them know over on the MM thread.

[Starwaster]

Okay, found a problem. None of the current config packages include a copy of modulemanager.dll. I've tried adding the most recent version manually, however that winds up breaking all SRB symmetry above 2 fold. Only two of the 3+ boosters will appear in the stage in the VAB (No single/numbered icon mixes), and only appear on the launchpad when launching (and not necessarily in the correct stage). That last bit isn't a bug caused by this mod though. It appears to be caused by the most recent version of Module Manager.

No, I've been seeing this bug since long before 1.5 came out.

It has a much better chance to be something in MFS than ModuleManager. There would have to actually be a patch file making changes to the SRB altering symmetry.

[Starwaster]

It is a problem with Modular Fuels.

MFS is running into a problem with SRBs that have ModuleFuelTanks added to them.

The following error is generated once for each SRB over two.

NullReferenceException: Object reference not set to an instance of an object
  at ModularFuelTanks.ModuleFuelTanks.UpdateSymmetryCounterparts () [0x00000] in <filename unknown>:0 

  at ModularFuelTanks.ModuleFuelTanks.OnStart (StartState state) [0x00000] in <filename unknown>:0 

  at Part.ModulesOnStart () [0x00000] in <filename unknown>:0 

  at Part+.MoveNext () [0x00000] in <filename unknown>:0 

(Filename:  Line: -1)

[Schilcote]

This has probably been asked a couple times before, but not in the last few pages. I'm running KSP at low resolution, and the fuel configurator gizmo goes off the bottom of the screen. Is there any way to move it? I noticed a screenshot up a ways had scroll bars in that window, how do you get those?

[Starwaster]

This has probably been asked a couple times before, but not in the last few pages. I'm running KSP at low resolution, and the fuel configurator gizmo goes off the bottom of the screen. Is there any way to move it? I noticed a screenshot up a ways had scroll bars in that window, how do you get those?

By updating to the latest version

[Dante80]

A question. I installed this, but for some reason stretchy tanks do not seem to work. You can select them in the action group menu, but changing height and diameter of the tank does not change the amount of fuel used.

[Starwaster]

A question. I installed this, but for some reason stretchy tanks do not seem to work. You can select them in the action group menu, but changing height and diameter of the tank does not change the amount of fuel used.

Make sure you have the latest version of MFSC and Nathan's latest Stretchy Tanks files.

[Dante80]

Yep, I think I do. V5 for the SRB and I got the MFS today from the OP. I also didn't get the real fuel types, maybe I installed wrong...

[NathanKell]

Dante80: try with RF, just in case.

Also, try this. Place a tank. Go to action groups, click on it, check the Tank Volume it says at the top of the new gui.

Go back to part mode, rescale it.

Go back to actions, check tank volume again. Has it changed?

[Dante80]

Used RF, fixed. Thanks man, time for some humongous H2 stages..XD

I think a good idea for a next release would be to bind the engine tech level with career progression.

[Savage117]

I feel like im missing something here, but what is the point of the LH2/LOX mix? No matter what engine i use it for it always has worse Delta V than any other mix. Haven't tried it with jets though, not sure I could use it for jets. I don't use it right now, the other mixes work fine, I'm just wondering why it's there if it has such a large disadvantage compared to the other mixes.

[MAKC]

I feel like im missing something here, but what is the point of the LH2/LOX mix? No matter what engine i use it for it always has worse Delta V than any other mix. Haven't tried it with jets though, not sure I could use it for jets. I don't use it right now, the other mixes work fine, I'm just wondering why it's there if it has such a large disadvantage compared to the other mixes.

Liquid hydrogen has a density of ~70 kg/m^3 compared to RP-1 which has a density of ~807 kg/m^3. You basically need more of it.

[Goozeman]

I started using KW rocketry expansion pack with MFS a few days ago and noticed that the Maverick-1D is listed as an upper stage engine. What is the reasoning behind this? If anything, we need smaller upper stage engines, not larger. From its description, the M-1D is supposed to be a larger, 2-nozzle Wildcat-5. Shouldn't this make it a L or L+ at best?

[Starwaster]

I feel like im missing something here, but what is the point of the LH2/LOX mix? No matter what engine i use it for it always has worse Delta V than any other mix. Haven't tried it with jets though, not sure I could use it for jets. I don't use it right now, the other mixes work fine, I'm just wondering why it's there if it has such a large disadvantage compared to the other mixes.

By propellant mass, LH2 will always outperform other fuels. As MAKC said, because of its lower density you need more of it, if you are trying to achieve the same Delta-V as a similar stage with a different propellant.

So, to answer your question, you first need to know what your goal is. If you need more Delta-V in that stage then consider going with a denser fuel.

If however you need a lighter stage then you go with the LH2 mix.

With a nuclear engine your choices are limited in RF to just the LH2 so you need much larger tanks. The Real Fuels link in my signature gives more fuel options for nuclear engines, but it's still a WIP.

[NathanKell]

I started using KW rocketry expansion pack with MFS a few days ago and noticed that the Maverick-1D is listed as an upper stage engine. What is the reasoning behind this? If anything, we need smaller upper stage engines, not larger. From its description, the M-1D is supposed to be a larger, 2-nozzle Wildcat-5. Shouldn't this make it a L or L+ at best?

Its nozzle is closer to vacuum-optimized than most (and actually looks more like a double Vesta than a double Wildcat-5 IMO). And we actually do need larger upper stage engines, since we actually have none.* Almost all the "upper stage" engines released are actually tiny OMS engines with pathetic TWR; we need engines that can be used in the second stage, not the last stage.

*Name a single upper stage engine in the 75-200 thrust range. Let alone one with decent TWR.

[Goozeman]

Its nozzle is closer to vacuum-optimized than most (and actually looks more like a double Vesta than a double Wildcat-5 IMO). And we actually do need larger upper stage engines, since we actually have none.* Almost all the "upper stage" engines released are actually tiny OMS engines with pathetic TWR; we need engines that can be used in the second stage, not the last stage.

*Name a single upper stage engine in the 75-200 thrust range. Let alone one with decent TWR.

I presume you mean 2nd stage engine in 1.25m, otherwise the Poodle fits the bill rather well.

IMO, if you need that much thrust in a second stage, use an L or L+ engine. Otherwise, design your first stages to hit ~1500-1700 m/s at burnout, and you'll find that the low thrust of the upper stage engines isn't an issue.

I don't suppose it would be possible to have a Sea Level/Vacuum option in configuring engines? Sometimes I find that I only need a 50kN engine in the sea level stage, or conversely as you pointed out, I need a 200kN 1.25m upper stage engine. The vacuum option would see a hit to TWR while giving a substantial increase in Isp.

[Guest]

The problem is, to do that, you'd need to change the nozzle expansion ratio. Upper stage engines look different than lower stage ones. Check out BobCat's NK-33 and NK-43. They're identical except for the latter's nozzle, which is much larger. Quite a lot of lower stage engines have a vacuum version, but this also changes their exterior appearance.

[NathanKell]

That's what L/L+ vs U/U+ _is_. A U/U+ engine isn't really an orbital maneuvering engine like the Poodle or LV-909; it's a (relatively) high-TWR engine with a vacuum nozzle and some chamber pressure increase. Like the LR-91 or J-2, or the NK-43.

The poodle doesn't fit the bill because its TWR suggests it's a pressure-fed many-restart engine, like Apollo SPS. Actually the Skipper is a good example of a 2.5m U.

But it would be nice to be able to toggle an engine's type, at least until we can have fully procedural engines.

Edited November 20, 2013 by NathanKell

[Goozeman]

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.

[Savage117]

By propellant mass, LH2 will always outperform other fuels. As MAKC said, because of its lower density you need more of it, if you are trying to achieve the same Delta-V as a similar stage with a different propellant.

So, to answer your question, you first need to know what your goal is. If you need more Delta-V in that stage then consider going with a denser fuel.

If however you need a lighter stage then you go with the LH2 mix.

With a nuclear engine your choices are limited in RF to just the LH2 so you need much larger tanks. The Real Fuels link in my signature gives more fuel options for nuclear engines, but it's still a WIP.

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.

[MAKC]

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:

1. Mk1 pod

2. KI-1000 tank

3. LV-T30 Liquid Fuel Engine (tech level 1)

4. MechJeb 2 (AR202 Case)

5. Stretch the tank until TWR starts going down to around 1.50 and below.

5a. Optional step: launch and revert to VAB.

6. Keep making the tank bigger and notice the dV increasing as you'd expect until you move cursor off the tank and StretchyTank updates and adjusts the dV down.

7. Make the tank smaller and notice dV going down as expected.

8. Make the tank bigger and notice dV still going down as you would not expect.

Hope this helps!

[AdmiralTigerclaw]

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.

Most of your weight in a tank part is in the fuel. A 3-4 ton tank part using Fuel and Ox can be cut to .9 tons with LH2 and LOX. Which means that to equal the weight of the old configuration, you need 4 times the tanks. But you'll get equal or greater total delta around 2 tanks of LH2-LOX

So while you are physically bigger, you get double your value for the same MASS. And THAT's what really matters in the final goal.

Depending on how you configure it, you can get a larger payload into orbit because you can squeeze in an extra engine. Or you just get more range out of your final payload.

Essentially, the payoff is in LH2 configs allowing you to scale up. But the tradeoff is in ensuring you deal with structural weaknesses.

I find value in using LH2 in a mid-stage. It lightens the load on the launch stage, but allows for greater ISP at your orbit eject stage giving you greater range, assuming you're going to use it early before the long term boil-off can take its toll. Essentially, use it as a mid stage for starting long missions, or the late stage for short missions.

[ferram4]

LH2/LOX is very good for getting the most dV out of the mass of your upper stages.

Let's say that you're launching two versions of a two-stage rocket, one with RP-1/LOX fueling both stages, the other with a LH2/LOX upper stage. Assuming both upper stages are the same percentage fuel by mass, here's how things compare for the upper stage, depending on the engine you use:

RP-1/LOX Isp: 320s - 380s

LH2/LOX Isp: 410s - 470s

The ranges are based on whether you use a vacuum-optimized or a atm-optimized engine. For the atm-optimized engines, you gain 28% more dV by using LH2/LOX; for vacuum-optimized, you gain 23% more dV. If for some reason you need to use an atm-optimized LH2/LOX engine for your upper stage, but you can use a vacuum-optimized RP-1/LOX engine due to TWR requirements, you still gain 7.8% more dV.

An alternative to increasing dV is that you can reduce the mass of the upper stage while maintaining the same dV. That might allow you to use a smaller, more efficient lower stage engine, boosting the dV of that stage. Or you could get rid of SRBs that you needed to get it going. Or you can split the difference and launch a slightly larger payload to orbit, taking advantage of the slightly lower mass of the upper stage to pile more on top of it.

If you're using FAR there's the added benefit that LH2/LOX is less dense than most of the payloads you'd be sending up, while RP-1/LOX is denser, which means that RP-1/LOX rockets will be less stable than LH2/LOX rockets. Ultimately, LH2/LOX is unwieldy, but it allows you to do more with less, which is quite dramatic when you consider that mass increases exponentially with increasing dV.