Modular Fuel System Continued v3.3 (OBSOLETE)

[SRFirefox]

I'm trying out the Real fuels for the kerbin sized stuff. I noticed that you need loads and loads of H2 to feed the now fuel hungry LV-N's... My question is, what (if any) advantage does LV-N's give with real fuels?

In Real Fuels? Not nearly as much as in Real Life . If you can launch an infinite amount of mass into orbit, then tank volume of hypergolic fuels becomes alot less than take volume of H2 nuclear fuel. That said, no rocket scientist looks at it by volume, but by launch mass. Look at the mass of the H2 tanks. It's tiny compared to any other fuel. The balloon tanks from StretchySRB make this even more apparent. This, combined with the efficiency of even a medium-efficiency NTR makes the cumbersome task of launching huge H2 tanks into orbit worth it - the resulting mass fraction (useful vehicle mass + dead weight vs fuel) is much better for a NTR than for a traditional chemical rocket. You're too used to stock KSP to notice the advantages. Let's ask Tsiolkovsky and his rocket equation to demonstrate. We'll assume we're going to stock Jool with no aerobraking in either direction, hauling the whole ship, which comes out to 9km/s or so dV.

340s ISP hypergolic rocket

9000 = 340 * 9.81 * ln(mass fraction)
2.70 = ln(mi/20)
2.718^2.7 = mass fraction
mass fraction = 14.9

800s ISP nuclear thermal rocket

9000 = 800 * 9.81 * ln(mass fraction)
1.15 = ln(mass fraction)
2.718^1.15 = mass fraction
mass fraction = 3.16

Thus we see that you will need less than a quarter the mass in fuel to make the trip with an NTR, assuming tankage mass is equal (which is not always the case). However, I think you can see the advantage of only needing 2.16 tonnes of fuel for every tonne of spacecraft instead of 13.9 tonnes of fuel for every tonne of spacecraft. So yes, it is still worth it to make the launches of LH2. You'll just need to strap on some cryocoolers (thermal fins in MFS) and make some tanks big enough to haul the fuel you need. I suggest multiple launches to make life easier on yourself. If you're not using stretchySRB, then I suggest either KWRocketry or NovaPunch for some of their larger tanks (especially the 5M NP tanks).

[Starwaster]

I'm trying out the Real fuels for the kerbin sized stuff. I noticed that you need loads and loads of H2 to feed the now fuel hungry LV-N's... My question is, what (if any) advantage does LV-N's give with real fuels?

H2 in LVNs provides the best Delta-V per kg of H2. You need less of it by mass.

As you've noticed, its low density means you need more by volume.

The next update will allow additional propellants, denser propellants. (methane, ammonia and water)

Edited December 15, 2013 by Starwaster
propellant, not fuel.

[jrandom]

Yea I see that, but I'm still wondering how to feed the LV-N with enough H2 to make it viable. I guess I just need to keep at it.

I haven't actually used nuclear engines with RSS/RO yet, so I don't really know what I'm talking about.

Edit... should have read the rest of the thread before responding.

[rottielover]

In Real Fuels? Not nearly as much as in Real Life . If you can launch an infinite amount of mass into orbit, then tank volume of hypergolic fuels becomes alot less than take volume of H2 nuclear fuel. That said, no rocket scientist looks at it by volume, but by launch mass. Look at the mass of the H2 tanks. It's tiny compared to any other fuel. The balloon tanks from StretchySRB make this even more apparent. This, combined with the efficiency of even a medium-efficiency NTR makes the cumbersome task of launching huge H2 tanks into orbit worth it - the resulting mass fraction (useful vehicle mass + dead weight vs fuel) is much better for a NTR than for a traditional chemical rocket. You're too used to stock KSP to notice the advantages. Let's ask Tsiolkovsky and his rocket equation to demonstrate. We'll assume we're going to stock Jool with no aerobraking in either direction, hauling the whole ship, which comes out to 9km/s or so dV.

340s ISP hypergolic rocket

9000 = 340 * 9.81 * ln(mass fraction)
2.70 = ln(mi/20)
2.718^2.7 = mass fraction
mass fraction = 14.9

800s ISP nuclear thermal rocket

9000 = 800 * 9.81 * ln(mass fraction)
1.15 = ln(mass fraction)
2.718^1.15 = mass fraction
mass fraction = 3.16

Thus we see that you will need less than a quarter the mass in fuel to make the trip with an NTR, assuming tankage mass is equal (which is not always the case). However, I think you can see the advantage of only needing 2.16 tonnes of fuel for every tonne of spacecraft instead of 13.9 tonnes of fuel for every tonne of spacecraft. So yes, it is still worth it to make the launches of LH2. You'll just need to strap on some cryocoolers (thermal fins in MFS) and make some tanks big enough to haul the fuel you need. I suggest multiple launches to make life easier on yourself. If you're not using stretchySRB, then I suggest either KWRocketry or NovaPunch for some of their larger tanks (especially the 5M NP tanks).

Thank you, your post was very helpful and very informative!

Now I just have to find this part you talk about (cryocoolers)? I have stretchy tanks, I'm looking to see where these coolers are.

[NathanKell]

you want the Cryogenic Super-Stretchy or the Balloon Cryogenic Super-Stretchy. The Cryo one has a similar structural coefficient to the regular tank, the BalloonCryo has a similar structural coefficient to the Balloon tank.

[Dante80]

Nathan, he was actually talking about this..I think.

So yes, it is still worth it to make the launches of LH2. You'll just need to strap on some cryocoolers (thermal fins in MFS) and make some tanks big enough to haul the fuel you need.

Speaking of which, I remember seing a thermal fin somewhere. Nucleonics?

[NathanKell]

Oh, sorry. Yes, that's in MFS, I believe in the Science tab. Maybe utility?

[rottielover]

I forgot to ask, is there info somewhere, or maybe some has already done this, To make the AIES pack compatible with this mod?

Edit: went back to OP and saw that AIES and FASA are both supposed to be supported already. Maybe I messed something up, but for me. MFS with real fuels is working on stock, and other mods like the shuttle engine pack, KW, NovaPunch, B9. Just not FASA and AIES?

Am I supposed to install the first download link as well as the real fuels link?

Edited December 15, 2013 by rottielover

[DasBananenbrot]

Nope only the Real fuels link

[rottielover]

Hmm. I will try re-installing, cause I'm not seeing any cooling fins in the science tab either.

[rottielover]

I found the problem. I'm playing in career mode, the thermal fin part is missing the "TechRequired = " line.

[NathanKell]

Ah. Right. And same for the other new parts.

[Starwaster]

I thought of a few ways that RCS can be made to use MMH/NTO or anything else you might want it to. Came to me when I wasn't even thinking about it.

Actually there's a few ways probably. Basic method is using ModuleGenerstor to convert NTO/MMH into MonoPropellant. Everything else is variations on that scheme.

Very basic is using a MM config to add a small MonoPropellant reservoir to anything with an RCS module that uses the MonoPropellant resource. Add a ModuleGenerator that turns MMH/NTO into MonoPropellant.

More complex would be a checkbox in the MFS GUI that will add the generator to to any tank you added MonoPropellant to

[Starwaster]

I have not yet had a chance to test this myself. As I alluded to above, this is a configuration that will add a ModuleGenerator to all RCS parts that already use MonoPropellant. (this on the off chance that someone is using some modded RCS part that uses a different singular resource so this doesn't screw up their stuff)

It also adds a small buffer resource of MonoPropellant. The generator will suck in MMH & N2O4 and produce MonoPropellant. The buffer isn't strictly necessary... I think.... but there's a nagging feeling that I should put one there so I did. Probably this means you don't even have to add separate monoprop tanks so if you have engines that use MMH/N2O4 then you can dedicate all tanks to those resources.

The generator is set to turn MMH / N2O4 into MonoPropellant at the same rates that rocket engines would consume them. So you shouldn't get an imbalance in those two resources. But if for any reason you run out of any one of those resources, AFAIK the generator will continue to suck in the other resource without producing MonoPropellant.

Again, untested (I'll test it myself when I get a chance today) but this should work. Extreme beta edition, try it at your own risk.

(requires ModuleManager 1.5+ or MM 1.3 + Sarbian Extensions)

save as real_RCS.cfg anywhere in your GameFolder hierarchy.

Edit: Ok, just tested my own crazy creation and it works. Except that it gulps down that fuel far faster than it needs to..... Just a few test maneuvers totally drained my tanks. I don't think it's a mass conversion rate because I don't think ModuleGenerator cares about mass ratios at all.... just resource units worth. But it occurs to me that while the tank drains in fractions, the generator is going to always convert at the rates I told it to even if it means that some is wasted.... So I revised the code to do it in fractions, and dammit, am I the ONLY one that when typing code on the forums keeps pressing ctrl+S to save???? Please tell me I'm not alone

Edit #2: Oh CRAP. Total damned failure. I should have known this. I did know this once but it's been so long since I messed with ModuleGenerator that I totally freakin forgot that ModuleGenerator drains all INPUT_RESOURCE with absolutely no regards as to whether or not:

1. There's a need for the OUTPUT_RESOURCE
   
2. There's ROOM for the OUTPUT_RESOURCE
   

Which really really sucks because aside from that small detail? It was totally freakin working. Totally man. Back to the drawing board. (but not today, too much to do on my own KSP project that I started on recently)

Edited December 16, 2013 by Starwaster

[AbeS]

Isn't there a way to make it work like a relay? (with hysteresis) for example assuming the RCS thruster has 1 monopropellant, If it goes below 0.1 the generator turns on, and if it goes above 0.9 it turns off.

[Starwaster]

Isn't there a way to make it work like a relay? (with hysteresis) for example assuming the RCS thruster has 1 monopropellant, If it goes below 0.1 the generator turns on, and if it goes above 0.9 it turns off.

None that I know of. The generator can be manually turned on and off but that's it.

I was poking around at the module definition and there's a parameter there that I've never seen used, resourceThreshold. I have no idea what it does, it's not documented and not used in any stock parts that I've ever looked at and it had zero effect when I tried setting it to various values.

What I think could work is making a plugin that implements a new part module that uses and overrides ModuleGenerator. It could activate/deactivate whenever its output resource needs refilling (and possibly when one of its input resources is empty). Have to think about it some more.....

[jrandom]

What I think could work is making a plugin that implements a new part module that uses and overrides ModuleGenerator. It could activate/deactivate whenever its output resource needs refilling (and possibly when one of its input resources is empty). Have to think about it some more.....

You could take a look at how TAC Life Support does it. Its generators have the option of freezing operation off when all output resource containers are full. That exact behavior is what you're looking for.

[NathanKell]

Ooh, TACLS generators respect full containers? The stuff Starwaster was talking about was exactly the process I went through making Real Gemini (I even had the generator code commented out in the CFGs for a while ) and eventually decided it wasn't worth the hassle, and I didn't have time to write my own generator handler. But if TACLS generator code can do that, woohoo.

[Starwaster]

You could take a look at how TAC Life Support does it. Its generators have the option of freezing operation off when all output resource containers are full. That exact behavior is what you're looking for.

Sounds worth checking out for sure.

[AbeS]

What about Kethane converters? Should be similar I guess

[rottielover]

How do I add the engines from the RLA stocklike pack to use modular fuels?

[Starwaster]

What about Kethane converters? Should be similar I guess

I think you're right. I think they also respect full containers. I dont know if missing inputs is an issue for them because I think it only takes one input... I think.

How do I add the engines from the RLA stocklike pack to use modular fuels?

at its most basic it needs ModuleEngineConfigs added. Look at engines.cfg to see what that looks like. One of the configurations should match what that engine already uses, preferably as its default. OR: you should replace the resources used in ModuleEngines to match the default in ModuleEngineConfigs. First entry is the micro engine which does just that to change LiquidFuels+Oxidizer to MMH+N2O4

[Razorcane]

That's not true. By editing the config, I was able to allow my shuttle patch to use two fuels for RCS, although I couldn't control the mixture ratio, so the leftovers were unbalanced, but it still worked. Still, it would be nice to be able to change RCS units to use your fuels, that way we can leave out monopropellant tanks if we want.

[NathanKell]

Razorcane: by setting multiple resources? But I thought the class only internally supported one resource! Weird.

[Starwaster]

Razorcane: by setting multiple resources? But I thought the class only internally supported one resource! Weird.

Yeah that's the way it seems to read... Resource name is jet a string, no list that I could see... What did you do exactly razorcane? Just set resourceName twice once for each fuel?