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


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1 hour ago, PickledTripod said:

Awesome. My Odin-powered space shuttle is now unflyable since it lost 4.5 tons in the back. Once adjustments are made it'll perform better than ever before though, thanks for the update!

Sorry about that, that engine was seriously under-specced though!

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Its still in heavy developement:

The concept is a Falcon 9-style reusable first stage with a hydrogen lifting-body upper stage. The idea for a reallife application would be to have full reusability without the insane mass ratios of an SSTO.
Im using this on a x3,2 rescaled Kerbin with FAR, so i need about 5500m/s delta-v (otherwise the rockets are to small for my taste), its designed for a ~85t payload to LKO, as a part of a Duna colony mission architecture.

The upper stage:

jsyf38A.jpgKobgNha.jpgLmkCh66.jpg

Im using lots of Tweakscale on this, also i had to cheat a bit (reducing the mass of some tanks and the large cargobays), otherwise it wouldnt fly that well on landing. Now its about 88t empty, it would be about 115t without those teaks. That higher dry wheight wouldnt be a problem on launch, i have reserves, but sadly parts have an extreme density in KSP compared to reallife. It comes with an OMS that yields about 400m/s delta-v.

 

The lower stage:


Ia8XCOV.jpgrOPV7RN.jpg

Its currently expendable, but im testing a new, larger lower stage that is supposed to fly back to the launchsite:

aMh82rU.jpg (hard to see, but i added a 5. SSME between the 4 allready used. That should make landing a lot easier due to lower TWR if only the center ones are running.

Now with the tweaked stats of the Yucatan a reusable first stage should be easier, since the upper stage has a bit more Delta-V.

Edited by Elthy
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Hey ... problem with the cryo tanks.

1) Start with a single fuel tank in the VAB. (I used the MRS 1-2 conical tank.)

2) Empty it.

3) The reported dry weight when you left click the part is correct, but the "Engineer's report" for the VAB is wrong. (The dry mass of this tank should be 0.375t. The engineer's report reads .8t, so probably 2x.)

4) Launch it to the pad. Now when you left click the part, it says the dry weight is 0t.

5) MechJeb consistently reported to me that the vessel mass was 0.375t in the VAB and also on the launch pad. But I'm not sure if that means MechJeb is just reading the part file or whether it really was 0.375t to the game and the problem was how things were being reported on the screen.

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OK I did a little more testing and confirmed some things.

1) The "engineer's report" in the VAB is definitely displaying 2x<dry>+<wet> mass. So somehow the dry mass is being added twice to the engineer's report VAB weight. Assuming this value is used anywhere, that kind of sucks for early career missions, where the pad is weight limited.

2) The behavior was the same whether I used a tank from a random mod, a stock tank, or even one the cryo tanks from Nertea. The left-click "dry mass" is correct in the VAB but is reported as 0 when outside the VAB, and the "Engineer's Report" mass double-counts the real dry mass.

All this behavior stops when the cryo-tanks mod is removed from game data. (Well, of course the dry mass reporting stops because that seems to be coming from this mod, but also the engineer's report stops reading 2x the dry mass.)

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7 minutes ago, blowfish said:

Probably an issue with Interstellar Fuel Switch, not CryoEngines specifically.  Everything in KSP seems to use a different method of determining a part's mass.  It's kind of a mess.

It is an IFS bug. IFS is setting part mass here, and telling KSP that the module itself weighs that amount again here (should use one or the other, not both). Got bitten with this one myself with B9PWings

Edited by Crzyrndm
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But it works fine if IFS is in Gamedata and CryoTanks is not. So how can you say it's "an IFS bug"? (I didn't try it the other way, because Nertea's stuff require IFS to work.)

29 minutes ago, Crzyrndm said:

It is an IFS bug. IFS is setting part mass here, and telling KSP that the module itself weighs that amount again here (should use one or the other, not both). Got bitten with this one myself with B9PWings

So did you figure out a workaround?

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45 minutes ago, Crzyrndm said:

It is an IFS bug. IFS is setting part mass here, and telling KSP that the module itself weighs that amount again here (should use one or the other, not both). Got bitten with this one myself with B9PWings

Well it's slightly complicated because the engineering report uses the prefab mass, so in order to get the engineer's report to display correctly, you need the module mass to be the part's mass - part prefab's mass.

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11 hours ago, StickyScissors said:

Is there a patch around here to update procedural parts to the new LH2/OX ratio from one of the recnt updates? or is that up for the PParts dev to solve?

Do they need a patch? I just checked, and my procedural tank has exactly the same fuel ratio as the modified stock tanks. That said, it's dry weight is higher, the 9t stock tank is 1.28t dry, while a proc tank with the same amount of fuel is 2t dry.

Edited by Temeter
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8 hours ago, Temeter said:

 

Do they need a patch? I just checked, and my procedural tank has exactly the same fuel ratio as the modified stock tanks. That said, it's dry weight is higher, the 9t stock tank is 1.28t dry, while a proc tank with the same amount of fuel is 2t dry.

Hmm, i'm running both CryoEngines and PParts latest versions and they definitely burn LH2 faster than Oxidizer.

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12 hours ago, StickyScissors said:

Hmm, i'm running both CryoEngines and PParts latest versions and they definitely burn LH2 faster than Oxidizer.

Strange. Maybe try reinstalling the mods? Solved some Issues with Interstellar for me some while ago.

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@mikegarrison @blowfish @Crzyrndm

I noticed the same issues regarding the dry mass indicated in the Engineer's Report (doubled) and in-flight right-click (zero). As far as I can tell, they're purely display errors with no actual impact on gameplay, but annoying nonetheless. If any of you know a different way to set up the IFS config that avoids these issues, I'd be happy to re-work the fuel-switching patch.

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21 minutes ago, Fraz86 said:

@mikegarrison @blowfish @Crzyrndm

I noticed the same issues regarding the dry mass indicated in the Engineer's Report (doubled) and in-flight right-click (zero). As far as I can tell, they're purely display errors with no actual impact on gameplay, but annoying nonetheless. If any of you know a different way to set up the IFS config that avoids these issues, I'd be happy to re-work the fuel-switching patch.

It would have to be a code fix in IFS.  Perhaps you could report this in that thread?

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10 hours ago, StickyScissors said:

Seeing as how it doesn't go down until i start firing the engines, im not sure boiling off is the issue. Especially after *just* launching the craft.

It is possible to easily check the engine fuel ratio:

1. Do you have Kerbal Engineer? Klick middle mouse button on a placed engine, it'll show you the fuel ratio the engine burns! Should be 97,35% LH2 / 6.25 % Oxidizer. At the same time a 9 ton Rockomax X200-16 fuel tank should have 9600/640 with Cryo fuel.

2. You can also check all other tanks, including procedural, with those numbers and basic math: Just take the LH2 fuel in a tank, divide through 97.35, multiply with 6.25, and you should have the amount of Oxidizer in the tank. If the number is of, then it's an issue with false fuel ratios!

Edited by Temeter
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