[1.12.x] Cryogenic Engines: Liquid Hydrogen and Methane Rockets! (August 13, 2024)

[carlorizzante]

On 3/7/2017 at 4:25 AM, Wyzard said:

Aerodynamics only matter when you're in the atmosphere.  If your rocket is just meant to go up to LKO and come back down, it's probably not worth using cryogenic engines, but they're much more economical if it's going to be spending most of its time in space, where bulky fuel tanks don't matter.  For example: a crew transport used to move kerbals between a station orbiting Kerbin and one orbiting the Mun.  Cryo/nuke engines let you make more trips back and forth before having to refuel.

If you mine asteroids to refuel your craft in orbit (which is generally cheaper than launching tankers from Kerbin), LH2 will give you more total dV from each asteroid.

Ok so that's the all point in using Cryogenic Engines? I made some comparisons and it seems to me that ships with FH2/O suffer quite a penalty compared to LF/O, for a tiny gain of TWR. Here's an example, same ship (same tank, modules, and same engine), only difference is the use of LF/O vs LH2/O.

LF/O - deltaV 2997, TWR 0.30/0.61

LH2/O deltaV 1957, TWR 0.42/0.65

[MaxL_1023]

It looks like you are using different-purpose engines. Your LF/O configuration looks like a Vacuum engine (2 to 1 SL/Vac ISP Ratio) while your cryogenic engine looks like a sustainer or mid/atmosphere stage (3 to 2 ratio). 

There is a critical TWR where cryogenic engines become more efficient, and it strongly depends on the scale of the rocket. Your example is using a fuel-switched engine?, so it may not be balanced. Try using a Volcano vs Reliant type setup - you will see what 380/422 ISP gets you as opposed to 260-/310. 

[Wyzard]

On 3/14/2017 at 6:49 PM, carlorizzante said:

Here's an example, same ship (same tank, modules, and same engine), only difference is the use of LF/O vs LH2/O.

"Same tank" — that's the problem with your comparison.  LH2 is less dense than LF, so the same-sized tank only holds about half as much fuel mass.  You need to use a bigger tank.

Here's a better comparison.  Build a ship with a stock Mk1-2 command pod, stock 2.5m monopropellant tank, stock Rockomax X200-16 fuel tank, and stock Poodle engine.  It weighs 18.27 tons and gets 1977m/s dV.  Then replace the fuel tank and engine with a HI-M-21 hydrogen tank, configured for LH2/O, and CT2X "Tunguska" engine.  It weighs 19.31 tons and gets 2293m/s dV.  That's 16% more dV for just 6% more mass.  (And note that it's only 6% more mass even though the LH2/O fuel tank is physically twice as big as the LF/O one.)

(The command pod and monopropellant tank are just to have some extra mass besides the propulsion system.  Comparing just the fuel tank and engine alone, there's much less of a difference in dV because the Tunguska engine weighs more than a Poodle, which offsets its greater efficiency.  But on a real spacecraft, that difference is a smaller fraction of the total mass.)

(Edit: The "HI-M-21" tank mentioned above is now named "H250-64" in later versions of the mod, and has slightly different stats, so the ship will weigh 19.526 tons and have 2260m/s dV.  Still significantly better than LF/O.)

Edited September 23, 2017 by Wyzard
Updated to reflect newer mod versions

[carlorizzante]

Thanks, I see. Well, I've never said to be an expert :-D

I'll do some more practice with those configurations. Again, thanks for the clarification!

ps. I didn't use a switchable engine. I did install/remove/reinstall the folder "CryoEnginesLFO". So the ship was exactly the same, just engine and tanks were configured for LF/O or LH2/O accordingly. And for the record, the engine was a Ct10 "Chelyabinsk" (nice name!).

Edited March 15, 2017 by carlorizzante

[TK421d]

I just recently started using this, and had an issue.  Not that it doesnt work, but an interaction i had to deal with:

 

A couple things with cryo tanks installed

1) It goofs up your vab/sph if you use Filter Extensions.  any LF/O tanks only show up in the stock tab.

while trying to figure out why FE was broken it came down to Cryo engines/tanks.

was a simple fix (for me, since i use the LFO patch): i simply manually edited the engine parts to reflect the patch changes, and then deleted the tanks and patches.  everything back to normal.

 

2) in the above discovery/fix i noticed that the tanks and their resource switching add an extroadinary amount of MM bloat,  a normal load of my modded dir was about 16.5k MM patches applied.  as soon as i made the above changes that was trimmed down to 8.3k

 

again, simple fix (for me) but just thought it might be something you wanted to be aware of the next time you are working on this one.

[Nertea]

It's not a problem that I intend to deal with, as far as I know this is a chronic fuel switcher problem.

[Stratickus]

Are there plans to add emmissives to this pack, or are the engines already too cool?

Cheers,

[Nertea]

On 3/24/2017 at 3:17 PM, Stratickus said:

Are there plans to add emmissives to this pack, or are the engines already too cool?

Cheers,

They already do have emissives last time I checked.

[Stratickus]

2 hours ago, Nertea said:

They already do have emissives last time I checked.

Interesting. Just to be clear, I was referring to the engine glow from excessive heat/use.

Cyro Engine on the left, Kerbal Atomics on the right. Infinite propellant and those engines have been running for a while. No other mods installed. 

Cheers,

[Nertea]

19 hours ago, Stratickus said:

Interesting. Just to be clear, I was referring to the engine glow from excessive heat/use.

Cyro Engine on the left, Kerbal Atomics on the right. Infinite propellant and those engines have been running for a while. No other mods installed. 

 

Cheers,

The KA engines just use a very slow throttle-tied glow animation. The CE engines use the older style of actually needing the engine to heat up (it's not in your image) to show the animation. I guess I could change that.

[dlrk]

Does the MFT config work for anyone? I thought it was a procedural parts issue, but it looks like the CFG is supposed add the cryogenic tank type to default tanks too, and it doesn't do that either.

[dlrk]

I solved the above problem, somewhat inartfully. Hopefully someone more knowledgeable RE MM can fix it better than I can.

The Cryogenic tank definition wasn't being added, because it looks Module Manager doesn't do anything with
 

TANK_DEFINITION:NEEDS[ModularFuelTanks,!RealFuels]:FOR[000_CryoTanks]

Changing it to
 

@TANK_DEFINITION:NEEDS[ModularFuelTanks,!RealFuels]:FOR[000_CryoTanks]

replaced all the tank definitions

And % and + do nothing.

Simply removing all that, so it is only TANK_DEFINITION works, but it would probably cause errors without MFT being installed
 

[blowfish]

@dlrk If you remove the FOR does it work?  MM shouldn't have any trouble processing NEEDS on that.

Edited April 3, 2017 by blowfish

[dlrk]

That worked

[Nertea]

55 minutes ago, dlrk said:

That worked

If you have a functioning version I would really appreciate a PR to fix the current one

[PocketBrotector]

Now that Mk4 includes cryo-support for its tankage and Cutlass engine, it seems that it would be good to have the ability to store LH2 or LH2O in procedural wings, since those are popular for use with Mk4 spaceplanes and can already be configured to carry LF/LFO/MP. The below should support both of the procedural wing mods maintained by @Crzyrndm, though I've only tested it with B9 Procedural Wings. Everything seems to be working fine with e.g. fuel ratios and boil-off. Note that these wings aren't ZBO tanks, so they should be probably set to a high fuel priority so that they drain before any true cryogenic storage.

Spoiler

@ProceduralWingFuelSetups:NEEDS[CryoTanks&B9_Aerospace_WingStuff|pWings]
{
	FuelSet
	{
		name = LH2
		Resource
		{
			name = LqdHydrogen
			ratio = 1
		}
	}
	FuelSet
	{
		name = LH2O
		Resource
		{
			name = LqdHydrogen
			ratio = 15
		}
		Resource
		{
			name = Oxidizer
			ratio = 1
		}
	}
}

@PART[B9_Aero_Wing_Procedural_TypeA,Proceduralwing*]:NEEDS[CryoTanks]
{
	MODULE
	{
		name =  ModuleCryoTank
		FuelName = LqdHydrogen
		// in % per hr
		BoiloffRate = 0.05
	}
}

 

@Nertea, if this is acceptable for inclusion in the mod's general distribution, I can submit a PR for it. I presume it would be distributed with CryoEngines since it's more closely related to CryoTanks than to Mk4.

[Nertea]

On 4/6/2017 at 6:58 PM, PocketBrotector said:

Now that Mk4 includes cryo-support for its tankage and Cutlass engine, it seems that it would be good to have the ability to store LH2 or LH2O in procedural wings, since those are popular for use with Mk4 spaceplanes and can already be configured to carry LF/LFO/MP. The below should support both of the procedural wing mods maintained by @Crzyrndm, though I've only tested it with B9 Procedural Wings. Everything seems to be working fine with e.g. fuel ratios and boil-off. Note that these wings aren't ZBO tanks, so they should be probably set to a high fuel priority so that they drain before any true cryogenic storage.

  Reveal hidden contents

@ProceduralWingFuelSetups:NEEDS[CryoTanks&B9_Aerospace_WingStuff|pWings]
{
	FuelSet
	{
		name = LH2
		Resource
		{
			name = LqdHydrogen
			ratio = 1
		}
	}
	FuelSet
	{
		name = LH2O
		Resource
		{
			name = LqdHydrogen
			ratio = 15
		}
		Resource
		{
			name = Oxidizer
			ratio = 1
		}
	}
}

@PART[B9_Aero_Wing_Procedural_TypeA,Proceduralwing*]:NEEDS[CryoTanks]
{
	MODULE
	{
		name =  ModuleCryoTank
		FuelName = LqdHydrogen
		// in % per hr
		BoiloffRate = 0.05
	}
}

 

@Nertea, if this is acceptable for inclusion in the mod's general distribution, I can submit a PR for it. I presume it would be distributed with CryoEngines since it's more closely related to CryoTanks than to Mk4.

If you make a PR to CryoTanks actually, that's where all the mod-agnostic LH2 stuff goes.

[Zapdap]

Any plans to make bigger tanks?  Like 5 meter?  Kerbal atomics engines need a lot of LH2 just to overcome the engine weight.

[Nertea]

58 minutes ago, Zapdap said:

Any plans to make bigger tanks?  Like 5 meter?  Kerbal atomics engines need a lot of LH2 just to overcome the engine weight.

Check the NFT thread for the devblog tomorrow!

[CrazyCanuck]

where can I find the fuel switcher? I can't seem to fill my tanks with liquid hydrogen/oxidizer. also, what is the boil off rate?

[TheRagingIrishman]

@Nertea It was recently brought to my attention that the CryoTanksFuelTankSwitcher.cfg is causing a negative dry mass in a part from MKS when in Liquid Hydrogen configuration. This causes all sorts of problems and explosions.
Some info on the part in question: in stock, it has a dry mass of .25 tons and holds 315 units of Liquid Fuel and 385 units of Oxidizer

also a CryoTanks github issue for moar visibility

[Nertea]

On 4/22/2017 at 9:39 PM, CrazyCanuck said:

where can I find the fuel switcher? I can't seem to fill my tanks with liquid hydrogen/oxidizer. also, what is the boil off rate?

More detail needed, most people don't have this problem. The boiloff rate is 0.05% of tank capacity in 1 game hour. 

21 hours ago, TheRagingIrishman said:

@Nertea It was recently brought to my attention that the CryoTanksFuelTankSwitcher.cfg is causing a negative dry mass in a part from MKS when in Liquid Hydrogen configuration. This causes all sorts of problems and explosions.
Some info on the part in question: in stock, it has a dry mass of .25 tons and holds 315 units of Liquid Fuel and 385 units of Oxidizer

also a CryoTanks github issue for moar visibility

What part? It would be nice to know this. 

However I can tell you that a part with 700 units of fuel needs to weigh 0.4375t in order to properly balanced! So in all likelihood that part is too light, so the patched mass will be negative... in order to fix, make the part obey squaddish balance conventions.

Edited April 26, 2017 by Nertea

[TheRagingIrishman]

1 minute ago, Nertea said:

What part? It would be nice to know this. 

However I can tell you that a part with 700 units of fuel needs to weigh 0.4375t in order to properly balanced! So in all likelihood that part is too light, so the patched mass will be negative... in order to fix, make the part obey squaddish balance conventions.

It's the inflatable tank in MKS. The reason it's light is that it's meant to represent a balloon that starts empty and gets bigger when you add fuel. I'll probably just increase the mass to what you suggested. 

[Nertea]

Just now, TheRagingIrishman said:

It's the inflatable tank in MKS. The reason it's light is that it's meant to represent a balloon that starts empty and gets bigger when you add fuel. I'll probably just increase the mass to what you suggested. 

If it's a part that has some kind of dynamic capacity or special adjustment, it might make sense for it to be excluded from the patch altogether.

[TheRagingIrishman]

1 hour ago, Nertea said:

If it's a part that has some kind of dynamic capacity or special adjustment, it might make sense for it to be excluded from the patch altogether.

No the fuel tank part of it is stock. The special part of it is that the model shrinks or grows based on how much fuel is currently in the part. I think I'll set up a patch to increase its mass if CryoTanks is installed.