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[1.11.x] Cryogenic Engines: Liquid Hydrogen and Methane Rockets! (Mar 9, 2021)


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Apologies for taking more of your time, I've got this far but I'm stumped as to how to make it work:

Spoiler

@PART[*]:HAS[@MODULE[ModuleCryoTank]]:FINAL
{
   @MODULE[ModuleCryoTank]
   {
    @BOILOFFCONFIG
    {
OUTPUT_RESOURCE
  {
    @ResourceName = Hydrogen
    %Ratio = 0.5
    %FlowMode = ALL_VESSEL
  }
}
}
}

 

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This is a great mod that adds a lot of diversity when designing rocket stages. Building a rocket that takes advantage of cryogenic fuel is a challenge.

If anyone's wondering what this mod changes when building rockets with LH2 engines, well, it depends. Cryogenic Engines can make your rocket more expensive or less expensive, but they will surely make it taller.

Smaller rockets will always be more expensive and 50% to 100% taller, but big rockets might be either more, or less less expensive (but still taller). It depends on the engines used, so it's worth experimenting.

Examples:

Spoiler

1. Comparing the deltaV with the same weights (but who cares about the weight?)

Using a Mk1-25 command pod and a Jumbo tank for reference, I took 2 smaller tanks for LF/Ox that weighed exactly as much as the bigger hydrolox one. The engines used in the comparison were the top-of-the-line vacuum 'Terrier' (345s ISP) and the hydrolox equivalent, also top-of-the-line vacuum 'Hecate' (465s ISP). They weigh practically the same and have practically the same thrust.

Using the cryogenic fuel in the rocket and a tank that weighed exactly as much as the stock one, the deltaV increased by 20% for the same weight, the size of the cryogenic tank was just a bit over 2 times larger, and the cost of the cryo tank+fuel+engine was about 4 times more expensive than the stock cost.

2. Keeping the same deltaV and the same TWR with a 1.25 Mun rocket: stock PT Series Munsplorer with 3.5 LF/O stages versus a modified PT Series Munsplorer with 1 LF/O + 2.5 LH2/O stages (the lander had to use LF/O for size purposes):

The almost-cryogenic 1.25 Mun rocket became about 50% taller, 15% more expensive and 35% lighter. Still not worth it to use cryogenic engines (unless you want to shave off some weight... but why?)

3. A massive 5 meter-wide 335t 7000dV lifter for a 11.5 payload (and a 0.8t fairing) with also a LF/O lander:

The cryogenic version was 12% LESS expensive (yay!) 45% lighter and only 1/3rd taller, surprisingly.

When it comes to the individual stages:

Cryo, top to bottom: 16k credits, 36,6k credits and 43,2k credits.

Kerbolox, top to bottom: 16.1k credits, 30.2k credits and 68,7k credits.

As you see, LH2 first stages have the most potential to decrease the costs.

 

 

Edited by Krzeszny
I was wrong about CE making rockets more expensive
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On 9/16/2020 at 8:48 PM, EimajOzear said:

Apologies for taking more of your time, I've got this far but I'm stumped as to how to make it work:

  Hide contents

@PART[*]:HAS[@MODULE[ModuleCryoTank]]:FINAL
{
   @MODULE[ModuleCryoTank]
   {
    @BOILOFFCONFIG
    {
OUTPUT_RESOURCE
  {
    @ResourceName = Hydrogen
    %Ratio = 0.5
    %FlowMode = ALL_VESSEL
  }
}
}
}

 

Same question here.

I searched all configs, also those in my RO backups, and did not find anything helpful.

 

Edit:

Perhaps it's necessary to patch away the boiloffconfig block and then patch a weird ResourceConverter into the tank, that converts LqdHydrogen to Hydrogen when no EC/s is used, and does NOT convert LqdHydrogen to Hydrogen when EC/s is used.

So a "negative" power consuming resource converter that needs electric power to NOT convert.

:/

Edited by Gordon Dry
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On 9/23/2020 at 6:58 AM, Krzeszny said:

Nice mod.

If anyone's wondering what this mod changes when building rockets, I've done a super simple comparison. In short, the mod adds a very expensive way (I'm talking up to 5 times) to increase the deltaV by something around 20% while making the rocket 2 times bigger. For fans of huge rockets that can afford to build them.

Using a Mk1-25 command pod and a Jumbo-sized LH2/Ox tank for reference, I also took 2 smaller tanks for LF/Ox that weighed exactly as much as the bigger hydrolox one. The engines used in the comparison were the top-of-the-line vacuum 'Terrier' (345s ISP) and the hydrolox equivalent, also top-of-the-line vacuum 'Hecate' (465s ISP). They weigh practically the same and have practically the same thrust.

Using the cryogenic fuel in the rocket and a tank that weighed exactly as much as the stock one, the deltaV increased by 20% for the same weight, the size of the cryogenic tank was just a bit over 2 times larger, and the cost of the cryo tank+fuel+engine was about 4 times more expensive than the stock cost.

Which, if you assume that each LFO stage is normally 2.5x the mass of it's payload (3.5x including it's payload), and you have a 10ton final payload on a 3-stage rocket, means that a LF/O rocket might be: 10*3.5^3 = 428.75t [1]. If you make all 3 stages cryo, your stage ratio is (2.5*.8)+1 = 3, so 10*3^3 = 270t. 63% the mass. The rocket equation adds up! (In practice you might increase Dv instead and go to a 2.5 stage design, but that's more complicated)

EDIT: You can compute any hybrid, assuming there is no LFO stage above a cryo stage, as: (P*3^C)*3.5^L, where P is payload mass, C is the number of cryo stages on top, and L is the number of LFO stages below.

Edited by lordcirth
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3 hours ago, lordcirth said:

Which, if you assume that each LFO stage is normally 2.5x the mass of it's payload (3.5x including it's payload), and you have a 10ton final payload on a 3-stage rocket, means that a LF/O rocket might be: 10*3.5^3 = 428.75t [1]. If you make all 3 stages cryo, your stage ratio is (2.5*.8)+1 = 3, so 10*3^3 = 270t. 63% the mass. The rocket equation adds up! (In practice you might increase Dv instead and go to a 2.5 stage design, but that's more complicated)

EDIT: You can compute any hybrid, assuming there is no LFO stage above a cryo stage, as: (P*3^C)*3.5^L, where P is payload mass, C is the number of cryo stages on top, and L is the number of LFO stages below.

I didn't know about that rocket equation. Nice to know. About that mass ratio constant, how can you be sure that 2.5x applies to all rockets and not just LFOx-powered ones (let's call them kerbolox)?

Also, the ISP I used was the vacuum ISP, so I imagine the deltaV would be much different and also incomparable during launches, as hydrolox and kerbolox rocket engines have different start and end points when it comes to their ISP's.

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2 minutes ago, Krzeszny said:

I didn't know about that rocket equation. Nice to know. About that mass ratio constant, how can you be sure that 2.5x applies to all rockets and not just LFOx-powered ones (let's call them kerbolox)?

Also, the ISP I used was the vacuum ISP, so I imagine the deltaV would be much different and also incomparable during launches, as hydrolox and kerbolox rocket engines have different start and end points when it comes to their ISP's.

In reality, you would probably keep the mass ratio the same, and increase delta-v, then remove a stage if possible. But that's too complex and specific for this rough estimate. It was intended more as a demonstration of how these efficiency gains grow exponentially.

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  • 2 weeks later...

Tharsis's extended model has an error caused by the animation nCDFOlf.png

Speaking of extending nozzles, would it be possible to have different Isp with the nozzle extended and retracted? Maybe it's a good idea for a future update.

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The CryoEnginesRestock  patch makes the  LH2 Rhino   completely OP if Etna is the baseline. Patched LH2 Rhino compared to Etna has higher TWR , 1.5x higher thrust, half the cost, higher Isp (and a smaller size if I recall?) 

Edited by Krzeszny
formatting errors etc.
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  • 3 weeks later...
  • 3 weeks later...
  • 1 month later...

Had a weird issue with Cryo Tanks where selecting a foil tank would cause FPS to drop below 1, and the tanks had both foil and polyhedral textures. I reverted to 1.5.3 and the performance was fixed, but not the textures. (Reverting Core also didn't seem to make a difference)

Edited by lordcirth
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CryoEngines 1.2.0

  • Marked for KSP 1.11.x
  • Updated DynamicBatteryStorage to 2.2.1
  • Updated B9PartSwitch to 2.17.0
  • Updated CryoTanks to 1.5.5
  • Updated DeployableEngines to 1.2.3
  • Updated ModuleManager to 4.1.4
  • Waterfall configuration for all engines
  • Stromboli can be stored in inventories
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  • 2 weeks later...

It seems that most of cryo engines spawn with shroud on despite turning it off. Moreover the shroud just keep on the engine after separation, so the rocket looks a bit strange. Is it a known issue? Is there any workaround?

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15 minutes ago, Darkherring said:

It seems that most of cryo engines spawn with shroud on despite turning it off. Moreover the shroud just keep on the engine after separation, so the rocket looks a bit strange. Is it a known issue? Is there any workaround?

This sounds on the surface like B9PartSwitch isn't working correctly. Do you have an up-to-date version for your install?

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1 hour ago, Nertea said:

What KSP version are you using (and the most recent version of the mod, I assume)?

KSP 1.11
CryoEngines 1.2.0
Here is the log

I'm using also Decoupler Shroud mod, which might be messing with shrouds, but I'm getting the same problem when engine is covered by procedural interstage.

EDIT:
After uninstalling Decoupler Shroud issue persists
5Huj23H.png

Edited by Darkherring
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CryoEngines 1.2.1

  • Updated CryoTanks to 1.5.6
  • Deconflict Waterfall and CryoEngines configs (zorg)
  • Fix cargo parts for KSP < 1.11
  • Rework how engine fairings work in general to be more robust
  • Recompress some normal maps to improve visuals of engines
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  • 2 weeks later...

I have an issue where boil off is happening despite plenty of EC, probably only in timewarp. I've noticed two different ships now where cooling is enabled and they have plenty of EC and solar panels, but after timewarping several days, lots of fuel boil off happens. :(

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