[1.8+] Real Fuels

[JT2227]

I'm using Real Fuels with RSS, and I'm having problems. NASA proposed missions to Mars use Liquid Hydrogen and NERVA engines, so I tried the same. No matter what I do, I can't get it to last more than 100 days. Since NASA has plans for using Liquid Hydrogen, I assumed there was a way to keep it stored for long periods of time. I know its next to impossible to stop boiloff, but is there any way to slow boiloff enough to utilize it like NASA plans to?

By reconfiguring the NTR for “bimodal†operation [9]

(both thrust and power production), the BNTR can

generate 10’s of kilowatts of electrical power (kWe) for

crew life support, high data-rate communications, and

zero-boiloff (ZBO) LH2 propellant storage using an

active refrigeration system.

Part of this article from Stanford (http://large.stanford.edu/courses/2015/ph241/gerrard2/docs/20120009207.pdf) shows that at least Stanford believes that LH2 refrigeration systems are possible. Are there any mods out there that simulate this part of realfuels?

Extra stuff (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110004377.pdf)

Edited October 14, 2015 by JT2227

[chrisl]

I posted this originally on the RO thread but someone pointed out that boil off was handled exclusively by Real Fuels so here goes. With the current boil off system, cryogenic fuel simply disappears, right? In other words, the boil off system determines that x amount of LH2 should be lost due to boil off, so that much LH2 is simply deducted from what's in the fuel tanks. Assuming that is a correct assumption, could the system be altered so that rather than simply deducting the cryogenic fuel, it would instead be converted into the appropriate gas? If there is not storage for that gas, the result would still be that the fuel would stop being available, but this would allow for the storage and use of that gase. From there it would be possible to try to replicate systems such as the Integrated Vehicle Fluids that ULA is working on for their ACES stage. I would think it would also be possible to replicate active refrigeration systems by then allowing the gas to be refrozen (though I'm aware that true long-term cryogenic fuel storage is about keeping the fluid cold versus re-cooling it after it's warmed up).

[Starwaster]

I'm using Real Fuels with RSS, and I'm having problems. NASA proposed missions to Mars use Liquid Hydrogen and NERVA engines, so I tried the same. No matter what I do, I can't get it to last more than 100 days. Since NASA has plans for using Liquid Hydrogen, I assumed there was a way to keep it stored for long periods of time. I know its next to impossible to stop boiloff, but is there any way to slow boiloff enough to utilize it like NASA plans to?

By reconfiguring the NTR for “bimodal†operation [9]

(both thrust and power production), the BNTR can

generate 10’s of kilowatts of electrical power (kWe) for

crew life support, high data-rate communications, and

zero-boiloff (ZBO) LH2 propellant storage using an

active refrigeration system.

Part of this article from Stanford (http://large.stanford.edu/courses/2015/ph241/gerrard2/docs/20120009207.pdf) shows that at least Stanford believes that LH2 refrigeration systems are possible. Are there any mods out there that simulate this part of realfuels?

Extra stuff (http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110004377.pdf)

The answer to your question was literally one page back. Nobody expects you to read the entire thread, but just a modest amount of effort would have helped you find this: http://forum.kerbalspaceprogram.com/threads/128502

I posted this originally on the RO thread but someone pointed out that boil off was handled exclusively by Real Fuels so here goes. With the current boil off system, cryogenic fuel simply disappears, right? In other words, the boil off system determines that x amount of LH2 should be lost due to boil off, so that much LH2 is simply deducted from what's in the fuel tanks. Assuming that is a correct assumption, could the system be altered so that rather than simply deducting the cryogenic fuel, it would instead be converted into the appropriate gas? If there is not storage for that gas, the result would still be that the fuel would stop being available, but this would allow for the storage and use of that gase. From there it would be possible to try to replicate systems such as the Integrated Vehicle Fluids that ULA is working on for their ACES stage. I would think it would also be possible to replicate active refrigeration systems by then allowing the gas to be refrozen (though I'm aware that true long-term cryogenic fuel storage is about keeping the fluid cold versus re-cooling it after it's warmed up).

Could the system be altered to allow conversion of cryo propellants to gas? Yes. It is 'possible'. I don't think anyone has plans to do so though I am currently revamping the boiloff code to cool tanks down. That's very close to completion and a beta version is available, also a 1-2 pages back. (check my posts)

Also: re: refrigeration. Again, one page back, this link was posted: http://forum.kerbalspaceprogram.com/threads/128502

[JT2227]

The answer to your question was literally one page back. Nobody expects you to read the entire thread, but just a modest amount of effort would have helped you find this: http://forum.kerbalspaceprogram.com/threads/128502

Could the system be altered to allow conversion of cryo propellants to gas? Yes. It is 'possible'. I don't think anyone has plans to do so though I am currently revamping the boiloff code to cool tanks down. That's very close to completion and a beta version is available, also a 1-2 pages back. (check my posts)

Also: re: refrigeration. Again, one page back, this link was posted: http://forum.kerbalspaceprogram.com/threads/128502

My goodness gracious, I am so sorry! Thank you so much for linking that!

Edited October 15, 2015 by JT2227

[dimovski]

3% structural fraction for kerolox at OF 2.5:1. 22.3% structural for LH2 only (you'd use a ballooncryo tank instead, not Default, for this reason ). 2.76% for LOX only.

You didn't ask, but 6.4% for OF 5.5:1 hydrolox.

Thanks for the quick and useful reply!

If I can, I'll give some rep to you now.

But now I have another question... These dimensions aren't all that feasible then, right? Or did they plan on compressing the hydrogen and oxygen...?

[NathanKell]

You're most welcome!

On the contrary, those dimensions look correct: that's the same diameter but twice the height of the Saturn S-II stage, which was 490t wet (vs 800t for Blok V-II) S-II was a pure cylinder with integral tanks and had a common bulkhead, so that explains the higher volume utilization.

[dimovski]

Then I must be missing something... If the structural fraction of LH2/LOX is 6,4%, once we calculate phi from density and mass ratios, we should get a dry density of 0,0234t/m^3, and a wet density of 0,36734t/m^3.

If V-II is a cylinder, 10m in diameter (so 5m radius) and 50m high, it's volume should be 5^2*pi*50, thus 1250pi m^3, roughly 3930m^3. A wet weight of 800t would mean that the density is 0,2035. Now, if we assume that the actual tank isn't a full 50m, but only around 40, that's still only 0,2544...

Same for V-III...

I must be missing something obvious here...

[NathanKell]

Per that cite, 690t of LOX and LH2. Let's assume it's at 5.5:1, that's 2010 m^3. The total stage volume, assuming a cylinder, is 3926 cubic meters. So only half the stated volume is used by the LH2 and LOX, which would make sense for a conic N1-style non-integral-tank stage.

Note the N1's structure:

[Starwaster]

Updated my preview version of Real Fuels with revamped boiloff.

Bugs fixed:

• Tank surface area more accurately calculated. (I was off by a factor of at least 10x)
  
• Converted heat leakage from watts to kilowatts. This means that if a calculation produced a heat leak of 1 watt, it was being interpreted as 1 kW instead of 0.001 kW. (yikes!)
  
• Increased cryogenic insulation.
  
• Fixed boiling point temperatures for LqdMethane & LqdAmmonia
  

https://www.dropbox.com/s/25hzx1lrlcw72w1/RealFuels_Boiloff_Revamp.zip?dl=1

Edited October 17, 2015 by Starwaster

[madmac]

I seem to have a bug. The aero bee og aj-10 engines does not work all of the sudden. Feed pressure too low no matter what. Even ultra simple craft like guidance unit, a tank and the engine on the surface of earth. Activating the engine under heavy acceleration does not help either. Anyone having the same problem?

Edit: When starting a new career it works again. But in my advanced career it does not work!

Edited October 17, 2015 by madmac

[NathanKell]

It's a pressure fed engine. It needs highly pressurized tanks to feed it, i.e. tank type Fuselage or tank type ServiceModule.

[madmac]

It's a pressure fed engine. It needs highly pressurized tanks to feed it, i.e. tank type Fuselage or tank type ServiceModule.

Yeah that was the problem. Strange when constructing the same craft in different careers, the results were different. I guess the tank type is not the same by default all the time.

[NathanKell]

In career, Fuselage and Structural are the only two tanks unlocked at the start, and of the two, Fuselage is the default.

In sandbox, all tanks are unlocked, and the tank type Default is the default type, and it's not highly pressurized.

[Pro7ech]

How can I change the number of ignition an engine can have? I can't find any file with those configs...

Edit : do I need to look in the ROh configs?

Edit 2 : I found it, here is an example for the LR91 Vacuum Engine (from the AIES pack)

Steps :

1) Find the name of the Engine and the mod it is from (or if it is stock). For my example I took the LR91 Vacuum Engine is frome the AIES pack (because cmon, hypergolic engine with only one ignition??)

2) Go to GameData -> RealismOverhaul -> RO_SuggestedMods -> AIES (name of the mode) -> Open RO_AIES_Engine.cfg (RO_"name of the mode"_Engine.cfg).

3) Find the part concerning the "LR91 Vacuum Engine". There is a line with "%ignitions = 1", change it to "%ignitions = 3" if you want 3 ignitions possible. Save and Exit.

4) Reload game and enjoy LR91 Vacuum Engine with 3 available ignitions.+

Attention! Some engines are configured to use the turbo pumps exhaust for some roll control, they have an ignition too, change it too and/or do not mistake it for the main engine ignition config (or you will end up with 3 ignition for the turbo pump and 1 ignition for the main engine, makes sens haha). Also, you need to delete and put again engines that are already on spacecraft (they do not update).

If you have an trouble reading the .cfg file because it's in one big block, copy past it in excel. It will make it look nice and easy to read. You can copy it back to the block note (with ctrl+a), but don't forget to save the initial config file in case you mess something up.

Edited October 23, 2015 by Pro7ech

[Starwaster]

How can I change the number of ignition an engine can have? I can't find any file with those configs...

Edit : do I need to look in the ROh configs?

Edit 2 : I found it, here is an example for the LR91 Vacuum Engine (from the AIES pack)

Just FYI, that engine uses hypergolic fuels. There's a reason it was given unlimited ignitions

[Pro7ech]

Just FYI, that engine uses hypergolic fuels. There's a reason it was given unlimited ignitions

For me it had 1 ignition only, this is why I changed it, I could not understand why it only had one. In the ROH config file the LR91, like many other hypergolic engines, is (at least for me) set at 1 ignition.

Edited October 23, 2015 by Pro7ech

[Starwaster]

For me it had 1 ignition only, this is why I changed it, I could not understand why it only had one. In the ROH config file the LR91, like many other hypergolic engines, is (at least for me) set at 1 ignition.

Ack my bad. I misread part of your text to say that its ignitions were set to -1 (instead of 1) which means unlimited. (so why did they give it only 1 then...? weird)

Edit: Oooh there were multiple versions of it and only later versions used hypergolic fuels....

Edited October 23, 2015 by Starwaster

[StoryMusgrave]

Just because an engine is hypergolic doesn't mean it should have multiple restarts.

In the case of the LR-91 as used by the Titan series was only fired once, regardless of RP1/LOX or hypergolic.

[Pro7ech]

Just because an engine is hypergolic doesn't mean it should have multiple restarts.

In the case of the LR-91 as used by the Titan series was only fired once, regardless of RP1/LOX or hypergolic.

I agree, but it all end up in the goal of the initial design. It was not designed to be reignited, but it could have been designed for. I'm doing a mission, and I need a hypergolic engine that can be reignited 2 times. I assume that I should not be difficult to take a well known engine using hypergolic and make a version that can be reignited 2-3 times. I have access to a limited number of parts, I'm trying to achieve my goals with what I have.

[Starwaster]

Just because an engine is hypergolic doesn't mean it should have multiple restarts.

In the case of the LR-91 as used by the Titan series was only fired once, regardless of RP1/LOX or hypergolic.

As I'm well aware. But some of what I'd read about the Titan III leads me to believe that the engine was restartable.

If that's not the case then that's not the case.

[StoryMusgrave]

If a guy wants to edit his own files, to each his own. Sure the LR-91 could have been designed to be reignited. It wasn't, so that's why it is the way it is in RO. Just to answer your question as to why it only had 1 ignition in the config to begin with. It's the premise that was presented that hypergolics should have many/unlimited restarts.

[NathanKell]

Starwaster, are you thinking of the Titan III's third stage, the Transtage? That was restartable, it used AJ10 engines.

[CaelumEtAstra]

Is there a template for the real solid fuels like HTPB, PBAN, APCP, etc.? All of the SRBs just use stock solidfuel, and I want them to be what the mod suggests, REAL fuels.

[NathanKell]

Real Fuels doesn't come with an engine config pack. Realism Overhaul, the only engine config pack I'm involved in, does indeed assign real fuels to real SRBs.

[ebigunso]

Real Fuels doesn't come with an engine config pack. Realism Overhaul, the only engine config pack I'm involved in, does indeed assign real fuels to real SRBs.

It'd be nice if you could adjust proc SRBs to be more inline with other real SRBs, since it's way underpowered right now, and it doesn't have a config for real SRB fuels.

Then maybe you can hand that over to Raptor831 so he can add his adjustment for the stockalike config too, which would be super awesome.

Edited October 24, 2015 by ebigunso