NFT Fuel Tank Capcities and Ratios Discussion

[Nertea]

I'm probably going to take a few posts to chew through all of this. I'll address some things (that are easy to answer, heh) and get to others later.

I don't understand why LqdOxygen is of the table, its a real Oxidiser and MORE dense than stock Oxidiser, It compensates for LqdHydrogen low density. I though after CRP 0.4 the new LqdOxygen would be adapted by most mods, and I though the CryEngines mod used it. Now to my horror I found it still used the stock Oxydiser which leads to a lot of confusion and hand waving which isn't necessary. For KSPI I made the convention to use either use real resources, or Kerbal fantasy stock resources like LiquidFuel, but I do everything to avoid mixing them.

Because it is literally pointless to me. Confusion comes when there are hundreds of fuel types that are completely arbitrary. I made the choice to introduce one resource and one alone, because there is really no point in introducing another. What does it add? A different string. What headaches does it create? Many. In my view, Oxidizer= LqdOxygen. That entry in CRP is there for RF folks (and you) to do what you want, probably with boiloff and a slightly different density. Not for all mods to standardize around.

Where cones the logic come from that LF has a density of 5.5? My sources say it should be 5, not 5.5. Where does the extra 10% come from?

My proof: a 3200 Unit fueltank filled with LiquidFuel has a Liquid mass of 16 ton, now the same tank with (3200x5=) 160000L of Water has the same liquid mass of 16ton!! If the value was 5.5, the tank of water would have weighted 17.6 ton.

My, more rigid, volumetric proof: a Jumbo-64 tank contains 6400 units, is 2.5m in diameter, and is 7.5m high. Math gives us 36815 L, which is actually closer to 5.75 units per L. Simple.

[FreeThinker]

Because it is literally pointless to me. Confusion comes when there are hundreds of fuel types that are completely arbitrary. I made the choice to introduce one resource and one alone, because there is really no point in introducing another. What does it add? A different string. What headaches does it create?

You don't have to support hundreds of resources, just the second most important resource in rockery: Oxygen! There are lot's of things LqdOxygen resource would add:

It adds

1. higher Oxidation performance,
   
2. Higher Density,
   
3. Lower Specific Heat
   
4. Lower Boiling Point
   

which will all add dept cryogenic realism to Modular Fuel Tank or to the upcoming Interstellar Fuel Switch 2.0 which will simulate Cryogenic cooling.

LqdOxygen also offers better mod compatibility with KSPI-E and Real Fuels and any other mod that uses Oxygen (as the LiquidOxygen can be decompressed to Oxygen Gas) like TAC that allow Kerbals to breath it.

When you say A Hydrogen, you should also say B Oxygen. THey Go together like Ying and Yang. With one side missing, the other get's into trouble.

Btw, why call the mod Cryognic Engines mod when you only use half of the 2 main ingredients?

Edited June 8, 2015 by FreeThinker

[FreeThinker]

My, more rigid, volumetric proof: a Jumbo-64 tank contains 6400 units, is 2.5m in diameter, and is 7.5m high. Math gives us 36815 L, which is actually closer to 5.75 units per L. Simple.

So If I assume your 5.5 to be true, than if I convert Jumbo-64 tank (which contains 6400 units) to 1unit/1Liter Water resource, using 5.5 conversion, the tank would suddenly hold 5.5x6400 = 35.2 metricTon of Water while the same tank can only hold 32 metricTon LiquidFuel !!!!

Just because Squad failed to put the incorrect amount of resource in a tank, doesn't mean we have to repeat this failure. I bet they started with a smaller tank (rockomax X200-8), calculated it's mass, rounded it down to a nice looking number (3 ton) and then started making larger versions, propagating the rounding error.

Edited June 8, 2015 by FreeThinker

[Fraz86]

You don't have to support hundreds of resources, just the second most important resource in rockery: Oxygen! There are lot's of things LqdOxygen resource would add:

It adds

1. higher Oxidation performance,
   
2. Higher Density,
   
3. Lower Specific Heat
   
4. Lower Boiling Point
   

which will all add dept cryogenic realism to Modular Fuel Tank or to the upcoming Interstellar Fuel Switch 2.0 which will simulate Cryogenic cooling.

LqdOxygen also offers better mod compatibility with KSPI-E and Real Fuels and any other mod that uses Oxygen (as the LiquidOxygen can be decompressed to Oxygen Gas) like TAC that allow Kerbals to breath it.

When you say A Hydrogen, you should also say B Oxygen. THey Go together like Ying and Yang. With one side missing, the other get's into trouble.

Btw, why call the mod Cryognic Engines mod when you only use half of the 2 main ingredients?

Cryogenic Engines already has both "main ingredients"; as Nertea stated above, "In my view, Oxidizer= LqdOxygen". I previously made the same assertion at the bottom of this post. If Oxidizer is LOX (which is frankly the most reasonable assumption anyway), then most of your objections are moot.

Density and mod compatibility are really the only legitimate issues. As my previous post addresses, the difference in density is modest (0.91 vs 1.14). As for compatibility, utilizing already existing stock systems rather than inventing your own is generally the best way to ensure that everyone is on the same page. It is KSPI-E et al. who are interfering with compatibility by implementing a redundant resource, and I believe Nertea is right to abstain.

So If I assume your 5.5 to be true, than if I convert Jumbo-64 tank (which contains 6400 units) to 1unit/1Liter Water resource, using 5.5 conversion, the tank would suddenly hold 5.5x6400 = 35.2 metricTon of Water while the same tank can only hold 32 metricTon LiquidFuel !!!!

I don't see the problem. LiquidFuel is presumably kerosene or RP-1, both of which have real-world densities around 0.81 g/ml (water is 1.0). Therefore, if anything, Nertea's LF density is a bit high at 0.91, but I don't think it's anything to worry about.

Edited June 8, 2015 by Fraz86

[FreeThinker]

Cryogenic Engines already has both "main ingredients"; as Nertea stated above, "In my view, Oxidizer= LqdOxygen".

Can you breathe Oxidiser? No? Then it's not Oxygen!! That's because Oxidizer have properties that are very similar to Dinitrogen Tetroxide, which is a Oxidiser which can be stored like stock Oxidier at room temperature, but you can not breath it, as it would kill you!

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I don't see the problem. LiquidFuel is presumably kerosene or RP-1, both of which have real-world densities around 0.81 g/ml (water is 1.0). Therefore, if anything, Nertea's LF density is a bit high at 0.91, but I don't think it's anything to worry about.

It's a common mistake to think LiquidFuel beeing RP-1/Kerosine. I made the same mistaken presumption, but I was wrong because it's already been proven by NathanKell that LiquidFuel is Unsymmetrical dimethylhydrazine, which works together with Dinitrogen Terroxide in a well known UMDH/N204 mix which has similar performance, density, ignition and storage requirements as stock LiquidFuel/Oxidiser mix.

Edited June 8, 2015 by FreeThinker

[grungar3x7]

A question, why is the code pulling different units for the components, eg. Squad Fuel Units and Liters? If the conversion is finalized at SFU's, why not feed those converted numbers into the code? I'm no code monkey, and all those snippets read like Greek to me, but this seems to be the heart of the issue.

[pacbard]

Can you breathe Oxidiser? No? Then it's not Oxygen!! That's because Oxidizer have properties that are very similar to Dinitrogen Tetroxide, which is a Oxidiser which can be stored like stock Oxidier at room temperature, but you can not breath it, as it would kill you!

- - - Updated - - -

It's a common mistake to think LiquidFuel beeing RP-1/Kerosine , I did the same thing, but I was wrong because it's already been proven LF is Unsymmetrical dimethylhydrazine, which works together with Dinitrogen Terroxide in a well known UMDH/N204 which has similar performance, density, ignition and storage requirements as stock LiquidFuel/Oxidiser.

Look - sorry I'll be very blunt with you - I respect your work and what you did for KSP, but no matter how you put it, or how good of an argument you make, liquid oxygen is not going to happen. Simply there isn't any tangible benefit to add liquid oxygen as a resource. Trying to make sense of stock oxidizer properties just requires to suspend all beliefs of anything real. Heck, we need to have a fudge factor for LH2 density to fit enough fuel in a tank to lift the rocket off the launchpad. I just gave up and I think that this thread should be about balancing the NFT tanks for their LH2 and LH2-OX configurations because right now they are way out of whack. Anything beyond that is really just a moot argument.

If you want, I'll write for you a liquid oxygen patch (the one that I linked earlier could work with a few tweaks, mostly tank mass needs to be worked out using the real fuels tank densities) and you can include is in KSPI as an extra patch. I don't know if Nertea is fine with it or if it is even allowed by modding rules. Just let me know what you want me to do.

[Fraz86]

Can you breathe Oxidiser?

Given that I'm assuming Oxidizer is LOX, yes, I suppose you could breathe it once it has been gasified.

Oxidizer have properties that are very similar to Dinitrogen Tetroxide, [...] LiquidFuel is Unsymmetrical dimethylhydrazine, which works together with Dinitrogen Terroxide in a well known UMDH/N204 which has similar performance, density, ignition and storage requirements as stock LiquidFuel/Oxidiser.

We'll have to agree to disagree on this one. I don't think the performance/density/ignition/storage requirements of fuels in KSP were set with enough concern for realism to make these characteristics a meaningful indicator of what LF & OX are "supposed" to be. I think the KSP developers wanted simple generic/archetypal resources, and they intentionally avoided introducing various largely redundant fuel options. Kerosene/RP-1 and LOX are the most generic/archetypal "rocket fuel" and "oxidizer." Moreover, jet engines also use LiquidFuel, which only makes sense if LF is something like Kerosene/RP-1. Jet engines do not run on unsymmetrical dimethylhydrazine.

Regardless, I don't see how any of this helps to support your original objection to Nertea's density calculation for LF. It looks like the density of unsymmetrical dimethylhydrazine is 0.79 - even lower than kerosene/RP-1!

Edited June 8, 2015 by Fraz86

[FreeThinker]

It's an mistake to look only at a resource density when comparing Oxygen with Oxidiser, with that logic why use Oxidizer at all as it has the same density as Liquid Fuel. So why bother? Because it matters!!

It especially matters if you look at the bigger picture. For example, how are you supposed to produce in the field (ISRU). Oxygen can be found almost anywhere, Oxidizer, requires a source of Nitrogen which is much less abundant and is highly complex to produce. Oxygen is harder to store but offers better performance due to being a better Oxidizer, that means you the high temperature and therefore higher Isp!. You can't offer cryogenic performance without Cryogenic characteristics. It's like love and marriage, you can not separate them

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Regardless, I don't see how any of this helps to support your original objection to Nertea's LF density calculation. It looks like the density of unsymmetrical dimethylhydrazine is 0.79 - even lower than kerosene/RP-1!

I said the MIX is similar, not the individual resource. Dinitrogen Tetroxide has a density of 1.44 when used with dimethylhydrazine, it evens out.

So, Why do I keep repeating my self? because it matters! When trying to balance a mod, I leaned that reality has a natural ability to balance a game. Trying to correct inconsistency with other inconsistencies only makes things worse.

Edited June 8, 2015 by FreeThinker

[pacbard]

A question, why is the code pulling different units for the components, eg. Squad Fuel Units and Liters? If the conversion is finalized at SFU's, why not feed those converted numbers into the code? I'm no code monkey, and all those snippets read like Greek to me, but this seems to be the heart of the issue.

It is the heart of the problem. We agree that 1 fuel unit of liquid fuel or oxidizer = 5.5 liters of liquid hydrogen. However, if we use this conversion to fill the tank we get tanks that hold very little liquid hydrogen, making is to engines that use liquid hydrogen (mostly converted nuclear engines) end up working really poorly. The rocket equation tells us that the only thing that matters in space travel is the wet/dry ratio of your rocket. If you have a tank that holds very little propellant weight in relation to its mass, you are going to have a very difficult time getting any delta v (yey logarithms!).

Part of the balancing is to increase the engines' ISPs (which results in them drawing less propellant mass and increasing the delta v output from the tank). The other part is to rebalance the wet/dry ratios so the cryo tanks are usable again.

Another problem with the cryo tanks is that the current IFS code fills them with about 3 times more LH2+OX than it should, which compounds the problem even further when you compare performance of nuclear engines and performance of cryo engines with the same fuel-switched tank.

[Fraz86]

It's an mistake to look only at a resource density when comparing Oxygen with Oxidiser , with that logic why use Oxidiser at all as it has the same denisity as Liquid Fuel. So why bother? Because it matters!!

This especially becomes true if you look at the bigger picture. Like how are you supposed to produce in the field (ISRU). Oxygen can be found almost anywhere, Oxidiser, requires a source of Nitrogen which is much less abundant. Oxygen is harder to store but offers better performance due to being a better Oxidiser, that means you het high temperature and therefore higher Isp!. You can't offer cryogenic performance without Cryogenic characteristics. It's like love and marriage, you can separate them

[...]

So, Why do I keep repeating my self? because it matters! When trying to balance a mod, I leaned that reality has a natural ability to balance a game. Trying to correct inconsistency with other inconsistencies only makes things worse.

In my view, what you're discussing here simply is not consistent with the spirit of stock KSP. Players who wish to delve into such issues should use realism mods. For the rest of us, its sufficient to accept that the game does not simulate all of the real-life challenges of spaceflight, including the difficulty of cryogenic fuel storage. Realism proponents should not try to impose their desires onto modders who choose to maintain a more stockalike paradigm.

Not to be rude, but I don't think that this is a discussion worth continuing. It's far off topic. Nertea has made it clear that he will continue to use Oxidizer, and that Oxidizer = LOX for the purposes of his mods. I think it's time to accept that and move on.

Edited June 8, 2015 by Fraz86

[Nertea]

Sorry I've been missing, very busy until next week. Yes, Oxidizer, no argument possible .

Reading really indicates that the main problem can be fixed by adjusting the dry mass ratio of the NFT cryo tanks when using oxidizer in them. I'll investigate the patches that have been posted next week.