Nertea

[1.8.x] Cryogenic Engines: High Isp chemical rockets! (Updated Nov 6)

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This should work for those wanting an LFO option


@PART[cryoengine*]:HAS[@PROPELLANT[LqdHydrogen]:FINAL
{
@MODULE[ModuleEngine*] {
@PROPELLANT[LqdHydrogen] {
@name = LiquidFuel
@ratio = 0.9
}
@PROPELLANT[Oxidizer] {
@ratio = 1.1
}
}
}

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Awesome work! I didn't know cryogenic rockets were that efficient.

Yep, Hydro-lox is really efficient, Now we need some Lithium Hydrogen Florine Engines. 542 ISP, Probably the highest chemical rocket ISP recorded

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That fuel switch thingy messes with the filter by resource button in the editor as none of the tanks show up that hold LFO by default when I filter for LF. Is there anything that can be done about it?

Edit: Also, when I right-click an LFO tank in the editor's parts list, can the info about LFO capacities be restored despite the fuel switch capability?

Edited by Honeybadga

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I did some further stat comparison for vac engines (best vac stock vs new cryo)

Testing rigs [0t = 40kg for probe control, I used ore containers to simulate heavy weight], for stock engines I took 2 longest matching diameter tanks + 1 engine. I added more tanks for LH/Ox to balance tanks/engines weight within ~1% error range.

******** 1.25m vac engines comparison ************

-----------------dV of cryo engine is--------------------

2% better (0t cargo) ------------ 17% better (48t cargo)

---------------------- dv ------------------------------

6179 vs 6303 cryo --------------------- 507 vs 593 cryo

----------------TWR comparison -----------------------

0.64-3.97 vs 0.59-2.43 cryo ââ€â€š 0.11-0.12 vs 0.1-0.11 cryo

===========================================

********** 2.5m vac engines comparison ***********

-------------------dV of cryo engine is-------------------

2.6% worse (0t cargo) ----------- 12% better (96t cargo)

-------------------------- dv ---------------------------

6942 vs 6758 cryo -------------------- 1626 vs 1823 cryo

-------------------- TWR comparison --------------------

0.3-2.29 vs 0.38-1.78 cryo ââ€â€š 0.13-0.21 vs 0.17-0.25 cryo

===========================================

********* 3.75m vac engines comparison ***********

----------------- dV of cryo engine is ------------------

4% better (0t cargo) ---------- 16% better (192t cargo)

------------------------ dv ---------------------------

6211 vs 6458 cryo ------------------ 1690 vs 1958 cryo

------------------- TWR comparison -------------------

1.2-7.68 vs 0.9-4.68 cryo ââ€â€š 0.56-0.93 vs 0.42-0.67 cryo

===========================================

So yah not suprisingly cryo vac engines shine with heavy payloads (with light ones performance is comparable to stock or even worse).

I think the cryo vac balancing is very nice right now. Maybe 2.5 needs little tweaks to be more inline with 1.25 and 3.75. Currently it 2.5m cryo differs from 1.25 and 3.75 versions in 2 things; cryo engine has more thrust (TWR) compared to stock but worse dV performance to stock ratio compared to 1.25 and 3.75m.

- - - Updated - - -

considering atmo cryo engines comparison - it's much harder for many reasons. However playing with different configurations I consistently get 200-300 less dV to orbit even with boosters. Then this is compounded by the fact that they have often TWR less than 1 in atmo (with comparable atmo dV to stock) so they don't accelerate rocket comparably fast compared to stock lifters when there's a need for this. Comparison for 3.75m is even worse since stock 3.75m 4000 kN engines are IMHO unbalanced and too op in every respect (thrust, isp and mass wise compared to stock 2.5m and 1.25m equivalents).

edit: a quick comparison between atmo 2.5 stock and cryo engines:

-------------------------------------------------------------------------------------------------------------------

Final orbital speed when fuel runs out, max thrust all the time, flying straight upwards, no payload except mk1-2 capsule:

2770 cryo atmo 2.5 (2.5m pod, 3 jumbo tanks LH2/OX)

2860 cryo atmo 2.5 (2,5m pod, 2 jumbo tanks LH2/OX)

3370 stock single atmo 2.5 (2.5m pod, 2 jumbo tanks LF/OX)

3490 stock dual atmo 2.5 (2.5m pod, 2 jumbo tanks equiv LF/OX)

------------------------- same test but added 6 biggest boosters with separators ----------------------

4046 cryo 2 jumbo tanks

4230 stock single 2 jumbo tanks

4100 stock dual 2 jumbo tanks equiv

------------------------------------------------------------------------------------------------------

So we can see that even without payload and with added boosters cryo atmo engines are worse than stock even though on paper they have 200more dV in atmo and vac.

------------------------------------------------------------------------------------------------------

So yah personally I have currently no incentive to use cryo atmo engines over stock (except beautiful flame and look ;))) However cryo vac engines are very viable as 2nd stage and are really interesting alternative to stock atm :)

Edited by riocrokite

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Honestly I think these cryo's are a bit overpowered. Their Isp might be realistic but right now that means really really overpowered. I changed the values myself, the maximum vac value was 405, but most were around 390 or so.

Engines are beautiful though, and I like the fuelswitch thing.

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Honestly I think these cryo's are a bit overpowered. Their Isp might be realistic but right now that means really really overpowered. I changed the values myself, the maximum vac value was 405, but most were around 390 or so.

Engines are beautiful though, and I like the fuelswitch thing.

Well higher ISP is balanced by heavier tanks (for every 100ton of LOX you carry about 12.5t of structural 'tank' weight, but for LH2/Ox this number is much higher: 22t).

So in the end gains aren't that high; with typical cargo you have like 10-12% gain of dV over stock chemical engines (and it's still much lower than LV-N). Plus you can't refuel those engines unlike stock ones so I wouldn't call them overpowered. Just my opinion.

Edited by riocrokite

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Well higher ISP is balanced by heavier tanks (for every 100ton of LOX you carry about 12.5t of structural 'tank' weight, but for LH2/Ox this number is much higher: 22t).

So in the end gains aren't that high; with typical cargo you have like 10-12% gain of dV over stock chemical engines (and it's still much lower than LV-N). Plus you can't refuel those engines unlike stock ones so I wouldn't call them overpowered. Just my opinion.

Yeah I decided that they werent unbalanced but I preferred just using LiquidFuel for convinience so I put the ISP down rather a lot (in the 370-390 range) and am using them with Liquid Fuel, love these models so much and I find they don't end up OP with LiquidFuel because the ones I have set to 390 Vac ISP have such large vacuum nozzles that they can't reliably be used as landers and they are heavier than their counterparts like the LV-909 and poodle so they get balanced quite well. this is just a personal preference though I do love everything you've done with these still!

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Plus you can't refuel those engines unlike stock ones so I wouldn't call them overpowered. Just my opinion.

Are you saying we can't just dock at an orbital fuel depot and refuel our LH2/O tanks?

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Are you saying we can't just dock at an orbital fuel depot and refuel our LH2/O tanks?

The stock resource system doesn't produce hydrogen.

I think it's "fixable" through the following MM patch...


@PART[ISRU]
{
MODULE
{
name = ModuleResourceConverter
ConverterName = LqdHydrogen
StartActionName = Start ISRU [LqdHydrogen]
StopActionName = Stop ISRU [LqdHydrogen]

AutoShutdown = true
GeneratesHeat = true
UseSpecializationBonus = true
TemperatureModifier = 500
SpecialistHeatFactor = 0.2
SpecialistEfficiencyFactor = 0.25
SpecialistShutoffTemp = 0.40
DefaultShutoffTemp = 0.25
Specialty = Engineer
EfficiencyBonus = 1.0

INPUT_RESOURCE
{
ResourceName = Ore
Ratio = 0.5
}
INPUT_RESOURCE
{
ResourceName = ElectricCharge
Ratio = 30
}
OUTPUT_RESOURCE
{
ResourceName = LqdHydrogen
Ratio = 1
DumpExcess = false
}
}
}

Disclaimer - I've only just woken up; there might be a stray curly brace somewhere.

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@Nertea, your engine configs are an example to every engine maker. Well done!

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The stock resource system doesn't produce hydrogen.

No, what I mean is are we able to pump LH2 between tanks back and forth or not?

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Another gem, Nertea. Thanks, now I have no desire to remain at work today. :confused:

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I'll patch in the fixed launch effects in a few days I have to spend some time catching up with other mods.

OMG yes, now I don't have to do this. I'm starting to think you can read my mind. Now all we need are some fuel tanks and I'll never have to use stock parts again. I'm working on a set that has a more standardized form than the random squad ones and was planning to include H2/LOX versions, but they won't approach this level of quality.

I can't tell if you've done emissives yet, but if you haven't and plan to can I suggest doing the 'inside only' look, instead of making the whole bell orange?

Also, can I ask how you determined the H2 fuel ratios for the stock tanks?

Edit: also, I think Yucutan is spelled Yucatan.

There are indeed emissives, they're more subtle and hopefully realistic (based mostly on Merlin 1D vac images from the last SpaceX launch).

That fuel switch thingy messes with the filter by resource button in the editor as none of the tanks show up that hold LFO by default when I filter for LF. Is there anything that can be done about it?

Edit: Also, when I right-click an LFO tank in the editor's parts list, can the info about LFO capacities be restored despite the fuel switch capability?

Mmm, annoying. Well, best I can do right now.

I did some further stat comparison for vac engines (best vac stock vs new cryo)

I'll keep watching, but it's possible that I might add more thrust for the non-vacs. Also, once new NFP gets released, there will be better mass-ratio LH2/O tanks available.

The stock resource system doesn't produce hydrogen.

I think it's "fixable" through the following MM patch...

Yeah, I might add this in too!

No, what I mean is are we able to pump LH2 between tanks back and forth or not?

Yeah totally.

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That fuel switch thingy messes with the filter by resource button in the editor as none of the tanks show up that hold LFO by default when I filter for LF. Is there anything that can be done about it?

Filtering for FSFuelSwitch will pull them up

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These are really nice models.

I agree! Nert really has the stock look down. Definitely using these in my next playthrough (once I get done updating mods, heh)

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These are beautiful. Really excellent work. These seem quite well balanced, and I absolutely love the way the resource is handled. I'm thinking about putting a MM .cfg on the LV-N to make it use your hydrogen.

Honestly, my compliments, these engines are instant classics.

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Also, once new NFP gets released, there will be better mass-ratio LH2/O tanks available.

Did you make new tanks specifically for LH2/O? Or are you adding FuelSwitch functionality to your existing tanks?

Yeah, I might add this in too!

I hope that NFP includes an [optional?] MM patch to add ISRU conversion options for not only LH2, but also Xenon and Argon.

Edit:

Perhaps NFE could even include an ISRU conversion process for Ore to DepletedUranium, which would be interesting because it would make the centrifuge much more valuable.

Edited by Fraz86

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I am adding FuelSwitch between LH2 and LH2/O to the existing LH2 tank series. And the centrifuge can now sift out EnrichedUranium from Ore, but it's really really inefficient.

Not sure about LH2/Argon/Xe ISRU right now.

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And the centrifuge can now sift out EnrichedUranium from Ore, but it's really really inefficient.

Awesome, that sounds like a great solution!

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