[1.12.x] Cryogenic Engines: Liquid Hydrogen and Methane Rockets! (Jan 22, 2022)

[ThreePounds]

Three_Pounds is right about the exhaust. HotRockets encountered exactly the same problem in the early stages of it's development, so there should be a solution buried somewhere in that thread.

Edit: sounds like Nazari just upped the speed/decay rate. Before that it did this:

http://i.imgur.com/23gVMtI.gif

Discussion starts around pg. 4 for anyone else looking.

Haha... that *.gif is funny. It looks like a space water hose rather than an engine.

EDIT: Actually, a static sprite, even if it looked cheap and people might complain because they like the slow-motion presentation, would be the most realistic.

Edited May 5, 2015 by Three_Pounds

[Raptor9]

Every time I turn around Nertea has a new mod out...very nice

[Darth Lazarus]

Sir Nertea

just awesome, as expected some very cool looking engines. can't wait to play around with them.

[Nertea]

These are cool. Ever since NFP was first released I've wanted a lander engine capable of using NFP's LH resource. This definitely fills that.

One idea for a part I'd love to see added here is a radial version of these engines. Way back when in the HOME pack Bobcat had a radial Aerospike that was absolutely perfect for small landers. I build a lot of my landers dropship style so they have a very low vertical profile which means a full length engine can be hard to fit without part clippage.

In any case, with the update to NFP rolling along, eventually I think I'll find it really interesting to try building some hybrid long range landers that use both NFP's super efficent engines for most stuff and these for landing / takeoff.

Radial engines aren't really my cup of tea. It's lots of work to model an engine and a radial engine just seems so... unversatile.

About the LFO config found in the extras folder, do I just copy the .cfg into all the engine folders or do I place them somewhere else? I am unclear on this

Edit:

When I have the LFO config and the Cryoengines folder in my GameData folder the game doesn't fully load but when I take them out it loads properly. Any suggestions?

Insufficient data - log, modlist, etc. Works fine here though.

It occurred to me that the resource system we now have in stock does not generate Hydrogen, so I have written an MM config to allow it to do so.

It produces standalone LH2, and LH2+Ox in what should be the correct ratio to fill tanks evenly.

@PART[ISRU]
{
    MODULE
    {
        name = ModuleResourceConverter
        ConverterName = LH2+Ox
        StartActionName = Start ISRU [LH2+Ox]
        StopActionName = Stop ISRU [LH2+Ox]     
        AutoShutdown = false
        GeneratesHeat = false
        UseSpecialistBonus = true
        SpecialistEfficiencyFactor = 0.2
        SpecialistBonusBase = 0.05
        Specialty = Engineer
        EfficiencyBonus = 1



         INPUT_RESOURCE
         {
            ResourceName = Ore
            Ratio = 0.5
            FlowMode = STAGE_PRIORITY_FLOW
           }
         INPUT_RESOURCE
         {
            ResourceName = ElectricCharge
            Ratio = 30
         }
         OUTPUT_RESOURCE
         {
            ResourceName = LqdHydrogen
            Ratio = 1.0
            DumpExcess = false
            FlowMode = STAGE_PRIORITY_FLOW
         }
         OUTPUT_RESOURCE
         {
            ResourceName = Oxidizer
            Ratio = 0.1
            DumpExcess = false
            FlowMode = STAGE_PRIORITY_FLOW
         }
    }
    MODULE
    {
        name = ModuleResourceConverter
        ConverterName = LH2
        StartActionName = Start ISRU [LH2]
        StopActionName = Stop ISRU [LH2]     
        AutoShutdown = false
        GeneratesHeat = false
        UseSpecialistBonus = true
        SpecialistEfficiencyFactor = 0.2
        SpecialistBonusBase = 0.05
        Specialty = Engineer
        EfficiencyBonus = 1



         INPUT_RESOURCE
         {
            ResourceName = Ore
            Ratio = 0.5
            FlowMode = STAGE_PRIORITY_FLOW
           }
         INPUT_RESOURCE
         {
            ResourceName = ElectricCharge
            Ratio = 30
         }
         OUTPUT_RESOURCE
         {
            ResourceName = LqdHydrogen
            Ratio = 1.1
            DumpExcess = false
            FlowMode = STAGE_PRIORITY_FLOW
         }
    }
}

I did test it, and it is much better than my prior attempts at MM configs in that it works, but feel free to correct me on the fuel ratios, etc.

Oh, and this should be up to date with the changes to heat behavior as of 1.0.2.

Yep, ratios are right. Should be fine.

Hello Nertea!

I really love your mods and I have decided to make a separate install of KSP next to my mostly stock install to play only with your mods because they fit thematically so well together. I love those LH2/LO2-Engines, they are awesome!

I have yet to see if the density of LH2 is believable in the tanks, but even if it isn't, there sure is a way for me to adjust that to my liking.

But there is one thing that I find really odd. It's the presentation of the exhaust stream of the engines. This slow-motion effect looks cool when you turn the engine or throttle it and the exhaust "lags behind". But it isn't really believable to anyone remotely familiar with how engines work. You even show us those amazingly pretty shock diamonds in the exhaust stream (whether they should occur in a vacuum or not is an entirely different story) which make my heart jump with joy! However, as the high Isp of these engines indicates, the exhaust should me moving several km/s and therefore should update instantly as you turn or throttle the engine. Could you consider changing the system to a more static approach? It'll look so much better for the slightly trained eye!

Thank you and keep up your excellent work!

I might take another pass at it eventually, perhaps when I do the RO versions. Not really a priority though.

LH2 capacity is calculated based on approximate volumes of stock tanks and is correct assuming 1U= 1L (CRP definition). Oxidizer is about 1U=5L so it's a bit confusing.

[MatterBeam]

Hi Nertea!

Amazing set of engines. Just a question. Have you fixed the 'Volcano's' thrust values? They're currently identical to an engine with half the weight.

[riocrokite]

Hi Nertea!

Amazing set of engines. Just a question. Have you fixed the 'Volcano's' thrust values? They're currently identical to an engine with half the weight.

? I can see 1.75t for volcano vs 1.25-1.5 for lt30/lt45. I don't see reason to change their thrust since it's IMHO only atmo engine that could compete with unbalanced stock ones

[MatterBeam]

? I can see 1.75t for volcano vs 1.25-1.5 for lt30/lt45. I don't see reason to change their thrust since it's IMHO only atmo engine that could compete with unbalanced stock ones

What I meant was that the Volcano at 1.75tons has the same thrust (275) as the 'Tusunga' at 3.25tons.

[riocrokite]

What I meant was that the Volcano at 1.75tons has the same thrust (275) as the 'Tusunga' at 3.25tons.

yah, it's just one engine is atmospheric lifter (more thrust and lower isp) and second is vacuum one (much less thrust and higher isp).

You can observe similar things in stock engines; re-l10 poddle 2.5m has similar thrust and weight as lt30 1.25m.

[MatterBeam]

yah, it's just one engine is atmospheric lifter (more thrust and lower isp) and second is vacuum one (much less thrust and higher isp).

You can observe similar things in stock engines; re-l10 poddle 2.5m has similar thrust and weight as lt30 1.25m.

I see... I just checked the atmospheric ISP for both engines and saw the major difference.

However... I see no point in ever firing a 3 ton 275kN thrust engine inside an atmosphere, ever.

[wasmic]

I see... I just checked the atmospheric ISP for both engines and saw the major difference.

However... I see no point in ever firing a 3 ton 275kN thrust engine inside an atmosphere, ever.

That's because it's not supposed to be used in the lower atmosphere.

[MatterBeam]

That's because it's not supposed to be used in the lower atmosphere.

So the heavier engine's only advantage is atmospheric performance, and it's not supposed to be fired in an atmosphere?

Quick calculation shows me that:

3 ton engine.

275kN of force

For a payload of 10 tons and a TWR of 1.0, you'll only get 1060m/s of dV, which is entirely pointless.

[Temeter]

Nah, the vaccum performance, it's 450 for the tunguska vs 410 for the volcano. The latter is actually better in atmosphere.

Personally, after toying some more around, I still find the tunguska lackluster, too. It's just not strong enough as an upper stage engine, and the new atmo really rewards high t/w ratios, which makes the skipper even better. It only has a bit of a place in interplanetary travel where it's actually good in very small range of ~3k dv with 0.5+t/w, but it get's otherwise outclassed by more weight efficient lfo engines (or volcanos) and utterly destroyed by nukes (which are ofc still more expensive). And all planets further than duna require at least 4k dv to allow for a return.

[MatterBeam]

IMO, the Volcano's thrust should be increased to 400-600 to make it competitive with the Skipper as a heavy but more efficient high atmosphere/second stage lifter.

[curiousepic]

If I wanted to make nuclear engines run on LqdHydrogen, do I only need to change the propellant in the cfgs? Or would the atmosphere curves/ISP change due to the difference in resource density?

- - - Updated - - -

It occurred to me that the resource system we now have in stock does not generate Hydrogen, so I have written an MM config to allow it to do so.

It produces standalone LH2, and LH2+Ox in what should be the correct ratio to fill tanks evenly.

Nice! Was just looking for this kind of thing. Should go along nicely with changing nuclear engines to use LqdHydrogen also.

[undercoveryankee]

If I wanted to make nuclear engines run on LqdHydrogen, do I only need to change the propellant in the cfgs? Or would the atmosphere curves/ISP change due to the difference in resource density?

Isp is momentum transferred per mass of propellant, so the numbers don't change with the density of the propellant. Change the propellant name, and the rest is automatic. I can post the MM config that I use when I get home from work.

[Nertea]

IMO, the Volcano's thrust should be increased to 400-600 to make it competitive with the Skipper as a heavy but more efficient high atmosphere/second stage lifter.

But the Volcano is a 1.25m engine, designed to compete with the LV-T30 . I really think you meant another engine.

[riocrokite]

But the Volcano is a 1.25m engine, designed to compete with the LV-T30 . I really think you meant another engine.

IMHO volcano is best cryo balanced engine from all atmospheric ones, it is also looking cool stacked on 2.5m quadcoupler as a replacement of single 2.5m atmo cryo engine. Buffing it further would mean that I'd rather use quadcouplers and more volcanos than 2.5m cryo atmo engines for lifting purposes.

[MatterBeam]

But the Volcano is a 1.25m engine, designed to compete with the LV-T30 . I really think you meant another engine.

IMHO volcano is best cryo balanced engine from all atmospheric ones, it is also looking cool stacked on 2.5m quadcoupler as a replacement of single 2.5m atmo cryo engine. Buffing it further would mean that I'd rather use quadcouplers and more volcanos than 2.5m cryo atmo engines for lifting purposes.

Yes, sorry.

I meant the Tunguska engine weighing 3.25 tons and producing only 275kN thrust. If at 400 thrust, it could compete with the Skipper as a heavier but more efficient engine.

[Sufficient Anonymity]

Yes, sorry.

I meant the Tunguska engine weighing 3.25 tons and producing only 275kN thrust. If at 400 thrust, it could compete with the Skipper as a heavier but more efficient engine.

I think it's currently set up to compete with the Poodle - agreed that at its weight, it'd be better off being pitted against the Skipper and thus receiving a slight thrust buff.

[igor_perusco]

disclaimer: i am not criticizing the mod or modder, i love the mod, just require clarification

I noticed when using this mod's patch to switch contents on fuel tanks, the amount of liquid hydrogen between LH2/Ox and all LH2 tanks is not consistent.

On a given fuel tank, when filled with LH2/Ox the oxidizer takes up exactly half of the tank's volume with regards to stock balance.

Example: FL-T400 holds 400 units of LFO, in the LH2/Ox setup the oxidizer takes up exactly half of that, 200 units

This leads to reason the remaining half of the volume is being occupied entirely by the LH2 (within reasonable limits).

Example: FL-T400 holds 200 units of oxidizer and 2000 units of lqdhydrogen, stands to reason the 2000 units of lqdhydrogen take up the same space 200 units of oxidizer would.

When filling the tank with purely LH2, the amount added barely accounts for any of the extra space

Example: FL-T400 holding 2200 units of LH2, only 200 more than the LH2/Ox variant, 180 *stock* units or the equivalent of 1800 units of lqdhydrogen vanished into thin air.

I noticed the same formula for calculating LH2 tankage applies to the Near Future mods too, so i assume this is intended and not a typo.

Is there a reason for this balancing? Is it supposed to be like this to balance the engines in the Near Future Propulsion pack? (i'm asking because i haven't messed around with the engines much, just the tank models, they look amazing)

Interesting to note: if the tanks *would* fill with LH2 to their maximum logical volume it would open up interesting design possibilities. The oxidizer and lqdhydrogen take up the same space and are used by engines in a 1:1 volume ratio, so two tanks could be stacked but one filled with only the heavy oxidizer and one with the lightweight hydrogen (hard to pull off with stock LFO tanks). Makes me think of how the space shuttle tank mass is distributed in real life, could help a lot with spaceplane balancing

Edited May 6, 2015 by igor_perusco

[Nertea]

LH2 tanks are volumetrically correct. It appears that the other ones are not. They should be about 1/3 less capacity than they are right now (Jumbo should have 2271 Ox, 22,710 LH2). That's problematic because tank volumes are already high. So the probably more reasonable option is to increase the capacity of the LH2 only tanks by 1/3 to compensate.

[hieywiey]

Could we get a RL10 analog and/or lookalike? About the size of a LVT-45 or a LVT-30, but without that whole 1.25 meter bit, basically just the engine bell. That would help for making Centaurs (both the one engine and two engine variants, I know it technically is considered to be a single engine but whatever), S-IV (not to be confused with the S-IVB) and DCSS.

Also, I'm confused because hydrogen is sparse, but this mod makes it barely lighter than LFO (which I presume is RP-1 a.k.a. Kerosene, and Liquid Oxygen); US RP-1's density is 0.81 g/ml, while LH²'s density is 0.07085 g/ml. And the tanks seem to hold more than the LFO tanks, which seems wrong.

[Nertea]

Both of your questions are answered in the OP. First, the fuel!

Known Issues:

• Currently the LH2/OX tanks hold too much fuel compared to their LH2 counterparts. I'm investigating what the best solution to this is given that tank sizes shouldn't be gargantuan.
  

For more information, read the post direction above yours.

This bit covers your request. Which won't be done for months.

Future Plans:

• Realism Overhaul version (correct sizes, friendlier attachment)
  

Modding is 25% fun, 25% sadness and 50% frustration.

[Shrike99]

I do have a minor complaint, related to the discussions i have seen on the last few pages

i think i can remedy it with some simple config edits, but i am completely unfamiliar with Interstellar fuel-switch

The Pure LqdHydrogen tank config has a mass fraction of 1.623...

Using LV-Ns patched to use LqdHydrogen, this gives a maximum single stage delta v of only about 3800m/s

With that fuel mass fraction the same-massed skipper gives better total mass for any delta-v requirements over about 125m/s, regardless of payload.

And that was using a skipper, which has the same mass as the LV-N and lower isp than some other chemical engines, the numbers get worse using say, a poodle or lv-909

I understand that this is to give them the correct volume given the poor density of Lh2?

Even so, is there some way i can edit the config so that i can:

A. reduce tank dry mass so that the mass fraction is improved, but volume is constant

or

B. Unrealistically compress the hydrogen somewhat, improving mass fraction

Additionally, and on an unrelated note, i would like to ask about changing the pure Oxidizer and Liquidfuel configs slightly

In FSfuelswitch the pure configs kept the 9:11 ratio, so an ftl-800 with 360-LF and 440-Ox, would have 720-LF or 880-Ox in its pure storage mode. Now i understand that they have the same mass and volume, and that is why Interstellar fuel switch gives equal numbers, but from my point of view, you would only use pure oxidizer if you were planning to also have tanks with pure liquidfuel, but the 800-800 system in place means that the fuel mixture is incorrect when you do this, making it rather redundant.

The liquidfuel-only option does of course make sense, either for aircraft or for non edited LV-Ns,

but i would still like to change this behavior if i can, and since i was asking about fuel configs anyway i thought i'd mention this too.

Anyway, help of any form would be appreciated.

[igor_perusco]

Additionally, and on an unrelated note, i would like to ask about changing the pure Oxidizer and Liquidfuel configs slightly

In FSfuelswitch the pure configs kept the 9:11 ratio, so an ftl-800 with 360-LF and 440-Ox, would have 720-LF or 880-Ox in its pure storage mode. Now i understand that they have the same mass and volume, and that is why Interstellar fuel switch gives equal numbers, but from my point of view, you would only use pure oxidizer if you were planning to also have tanks with pure liquidfuel, but the 800-800 system in place means that the fuel mixture is incorrect when you do this, making it rather redundant.

The liquidfuel-only option does of course make sense, either for aircraft or for non edited LV-Ns,

but i would still like to change this behavior if i can, and since i was asking about fuel configs anyway i thought i'd mention this too.

You want to be able to stack two identical tanks on top of eachother, fill each with only one type of fuel, and have them feed a LFO engine, right?

The problem with the above is:

Currently LFO engines use a 9:11 (unit AND volume) ratio of LF to O. Cryogenic engines in this pack use a 1:10 (ksp unit) or 1:1 (volume as supplied by the tanks in this mod) ratio of LH2 to O

If balancing were to be done so that the LF and O tank setups would provide 9:11 ratio of fuel to eachother, you would not be able to build separate LH2 an O tankage to feed a cryo engine properly

If balancing were to be done so that the LH2 and O tank setups would provite the 1:1 ratio of fuel to eachother (volumetrically), you would not be able to build separate LF and O tankage to feed a LFO engine properly

note: i'm going about this with the assumption that you're keeping the *as is* balancing for LH2/O tanks in this mod (1:1 volume ratio between LH2 and O)

Lose/lose situation :c

A thing you, i or someone else could do with a handy MM patch is balance the only LF and only O tank setups on a 9:11 ratio to eachother, the LH2 only tanks would have to hold a lot more to allow for separate LH2 and O tanks feeding a cryo engine.

example: the FL-T800 would have the setups 360/440 LFO ; 4000/400 LH2/O ; 720 LF ; 880 O ; 8800 LH2 (the large amount of LH2 on the LH2 only tank would help with both feeding a cryo engine AND a nerva in LH2 setup, win win, except realism oriented people would be upset)

another setup: 360/440 LFO ; 4000/400 LH2/O ; 654.54 LF ; 800 O ; 8000 LH2 (this would bring down the volume on the LH2 tank a bit and bring it in line with the LH2/O tank setup, the problem with this way is you get very little volume in the LF tank too and realism oriented people would still be upset)

Of course on both setups you'd want to give the LF and O tanks altered dry mass (.9 and 1.1 times the standard tank mass) to preserve balancing. The only way i see to go about this semi realistically would be to have the cryo engines use a more extreme (volumetric ratio) of LH2 to O2 (2:1, 3:1 or 4:1) but without altering tank dry mass that would make the cryo engines useless.

EDIT: I'd like to add i prefer the as-is balancing if it's of any worth to anyone, i don't believe in realism in ksp. Legit looking awesomely modelled engines with a "Cryo!" sticker slapped on the side? YES; real life fuels setups, nah. There's RSS and real fuels and whatnot for that.

Also i pretty much have a patch doing exactly what you want, problem is it's for the firespitter tank switcher, i'll post it here if it's ok and if you're intereted

Edited May 7, 2015 by igor_perusco