Fuel Mass Ratios on New Tanks

[Renegrade]

I've noticed the fuel mass ratio on some of the new tanks seems off.

The little R-4 has a terrible ratio (and is incredibly huge for it's 10 liquid fuel) of 1.33:1

The R-11 is much better, but a bit off at 8.18:1

The R-12 donut is a spectacular 31:1

The classic tanks are 9:1 still it seems

(full mass:dry mass)

The RCS values are also all over the place, although that's the way it's always been (the R-10 is 5:1, the R-25 is 7:1 and the FL-R1 is 8.5)....  I only mention this as I recall something about them being updated with new consistent values.  Much data entry.  Such error.  Much ratio.  Wow!

Edited March 10, 2018 by Renegrade

[RuBisCO]

Yeah I think the mass ratios are really off there. The gold tanks should have better mass ratios in my opinion than any other tanks at the cost of being more expensive and easier to damage. And of course the ratios should be depend on surface area to volume, thus the R-4 should be better then the R-11, which should be better then the R-12, not the other way around as it is now. I have also noticed the fuel:ox ratio is not correct with the R-11, the normal fuel:ox ratio is 9:11, the R-11 those has left over oxidizer and a fuel:ox ratio of 4:5.

Looking at the config file here are the fuel and weight ratios:

	R-4 'Dumpling'	R-11 'Baguette'	R-12 'Doughnut'	'ROUND-8' (KSP 1.3.1)
Wet Mass	0.4475375	0.3038	0.31	0.3375
Dry Mass	0.3375	0.03375	0.01	0.0375
Wet:Dry Ratio	1.32603703703704	9.00148148148148	31:1	9:1
Fuel	10	24	27	27
Ox	12	30	33	33
Fuel:Ox Ratio	5:6	4:5	9:11	9:11

As you can see something is very screwy with the 'R' Series of tanks, despite being nice and shiny. Editing the config files here is what I would change

	R-4 'Dumpling'	R-11 'Baguette'	R-12 'Doughnut'
Wet Mass	0.1625	0.4875	0.325
Dry Mass	0.0125	0.0375	0.025
Wet:Dry Ratio	13:1	13:1	13:1
Fuel	13.5	40.5	27
Ox	16.5	49.5	33
Fuel:Ox Ratio	9:11	9:11	9:11

What you see underline is what you will have to change.

Edited March 10, 2018 by RuBisCO
Added tables

[GoSlash27]

RuBisCO,
 Could you please add this info to the bug tracker here?

https://bugs.kerbalspaceprogram.com/issues/17975

Thanks,
-Slashy

[RuBisCO]

44 minutes ago, GoSlash27 said:

RuBisCO,
 Could you please add this info to the bug tracker here?

https://bugs.kerbalspaceprogram.com/issues/17975

Thanks,
-Slashy

Ok I did it, and added my updated .cfg files.

[Renegrade]

13 hours ago, RuBisCO said:

Yeah I think the mass ratios are really off there. The gold tanks should have better mass ratios in my opinion than any other tanks at the cost of being more expensive and easier to damage. And of course the ratios should be depend on surface area to volume, thus the R-4 should be better then the R-11, which should be better then the R-12, not the other way around as it is now. I have also noticed the fuel:ox ratio is not correct with the R-11, the normal fuel:ox ratio is 9:11, the R-11 those has left over oxidizer and a fuel:ox ratio of 4:5.

 

Normally I'd agree here as that would add some interest and variety to different tank models, aside from size.  Heck, I'd love to be able to right-click and configure a tank with different hull options (more heat resistance, more strength, at the cost of mass, or vice versa, etc).

However, Squad decided to unify tanks to a 9:1 ratio for some reason, and the official game files should probably follow that standard for consistency.  Unfortunately. 

A side note: I'm VERY alarmed that the fuel/ox ratios were wrong.  I had assumed they were correct (it's hard to get that stuff wrong, whereas dry mass/wet mass/fuel mass can get a bit complicated at times).   What the heck?

Yet another side note: I only checked a handful of tanks.  I hope nothing else has changed...

[klgraham1013]

Nice work all!  Hope this makes it in the next hotfix.

[Renegrade]

I've computed some 9:1 values, in the event that Squad is maintaining their 9:1-for-everybody plan.  This uses RuBisCo's dry mass values (which have a good feel to them), but reduces the fuel to make it a 9:1 ratio.

externalTankToroid
    mass = 0.025
    amount = 20.25  // LF
    amount = 24.75  // O

externalTankCapsule 
   mass = 0.0375
   amount = 30.375  // LF
   amount = 37.125  // O

externalTankRound
   mass = 0.0125
   amount = 10.125  // LF
   amount = 12.375  // O

YOU get a 9:1 ratio, and YOU get a 9:1 ratio, and YOU get a 9:1 ratio...

Edited March 11, 2018 by Renegrade
Fixed error in name of tanks

[RuBisCO]

1 hour ago, Renegrade said:

I've computed some 9:1 values, in the event that Squad is maintaining their 9:1-for-everybody plan.  This uses RuBisCo's dry mass values (which have a good feel to them), but reduces the fuel to make it a 9:1 ratio.

externalTankToroid
    mass = 0.025
    amount = 20.25  // LF
    amount = 24.75  // O

externalTankRound
   mass = 0.0375
   amount = 30.375  // LF
   amount = 37.125  // O

externalTankCapsule
   mass = 0.0125
   amount = 10.125  // LF
   amount = 12.375  // O

YOU get a 9:1 ratio, and YOU get a 9:1 ratio, and YOU get a 9:1 ratio...

As I said in the bug fix site you need with switch 'Round' and 'Capsule' around, as the 'Capsule' is thrice the volume of the 'Round'.

2 hours ago, Renegrade said:

Normally I'd agree here as that would add some interest and variety to different tank models, aside from size.  Heck, I'd love to be able to right-click and configure a tank with different hull options (more heat resistance, more strength, at the cost of mass, or vice versa, etc).

However, Squad decided to unify tanks to a 9:1 ratio for some reason, and the official game files should probably follow that standard for consistency.  Unfortunately. 

A side note: I'm VERY alarmed that the fuel/ox ratios were wrong.  I had assumed they were correct (it's hard to get that stuff wrong, whereas dry mass/wet mass/fuel mass can get a bit complicated at times).   What the heck?

Yet another side note: I only checked a handful of tanks.  I hope nothing else has changed...

Well maybe it is time for them to diversify. I mean they already got different skins. 

[Renegrade]

22 hours ago, RuBisCO said:

Well maybe it is time for them to diversify. I mean they already got different skins. 

That would be totally cool, but I'm afraid that they have this 9:1 guideline etched into some crazy stone tablet.  I pushed them on this very same issue some time ago (1.0? 0.90?) when they started doing the 9:1 thing, but the answer was pretty much "nine-to-one, or be done!".   I think the main topic was actually RCS back then, but the 9:1 thing came out somehow.

Anyhow, I've fixed the reversal in my config files, and I'll go back to the other posts now and fix 'em up too.  Thanks for pointing that out.

[Cunjo Carl]

 

22 hours ago, RuBisCO said:

Well maybe it is time for them to diversify. I mean they already got different skins.

 

   I actually happen to disagree in this case. I definitely like the feel of having different tanks with different drymasses and other tradeoffs, but I think in the end it's better if they're all mostly equivalent. A large part of KSP is learning how to make better rockets/planes to go faster and farther, and when all the fuel tanks are equivalent they're just not a thing you need to worry about. I like not worrying about fuel tanks! If some special tanks are better, you'd need to warp your ship designs around them. In practice the difference between the 1/9 and 1/31 tanks is equivalent to about 25s Isp on TWR=1 staged rockets, and upwards of 70s Isp on SSTOs. I think we'd be seeing a lot of doughnut stack rockets emerge! I can definitely see the fun and value of being more freeform in tank drymass choice, but I think it would ultimately lead to silliness. It's the same story with the wings!

[RuBisCO]

1 hour ago, Renegrade said:

That would be totally cool, but I'm afraid that they have this 9:1 guideline etched into some crazy stone tablet.  I pushed them on this very same issue some time ago (1.0? 0.90?) when they started doing the 9:1 thing, but the answer was pretty much "nine-to-one, or be done!".   I think the main topic was actually RCS back then, but the 9:1 thing came out somehow.

Anyhow, I've fixed the reversal in my config files, and I'll go back to the other posts now and fix 'em up too.  Thanks for pointing that out.

Ok ok geez guys, well lets see what fix they come out with in 1.4.1... nnaaahh, here is what I would like to see then (using precious 9:1 wet:dry ratio):

	R-4 'Dumpling'	R-11 'Baguette'	R-12 'Doughnut'	Oscar-B
Wet Mass	0.135	0.405	0.3375	0.1125
Dry Mass	0.015	0.045	0.0375	0.0125
Wet:Dry Ratio	9:1	9:1	9:1	9:1
Fuel	10.8	32.4	27	9
Ox	13.2	39.6	33	11
Fuel:Ox Ratio	9:11	9:11	9:11	9:11
Prop Mass	0.12	0.36	0.3	0.1

Oscar-B needs to be halved to make it all fair by volume. The 'Dumpling' is 133.3333333% the volume of the Oscar-B so I used as prop mass ratio of 120% to make for non-endless decimal numbers. Notice the dry mass are whole numbers in kg divisible by 5 for the R-4 and R-11, nice for number OCD. Underlined is all you need to change in the .cfg file. Other number options:

	R-4 'Dumpling'	R-11 'Baguette'	R-12 'Doughnut'	Oscar-B
Wet Mass	0.144	0.432	0.3375	0.1125
Dry Mass	0.016	0.048	0.0375	0.0125
Wet:Dry Ratio	9:1	9:1	9:1	9:1
Fuel	11.52	34.56	27	9
Ox	14.08	42.24	33	11
Fuel:Ox Ratio	9:11	9:11	9:11	9:11
Prop Mass	0.128	0.384	0.3	0.1
	R-4 'Dumpling'	R-11 'Baguette'	R-12 'Doughnut'	Oscar-B
Wet Mass	0.1485	0.4455	0.3375	0.1125
Dry Mass	0.0165	0.0495	0.0375	0.0125
Wet:Dry Ratio	9:1	9:1	9:1	9:1
Fuel	11.88	35.64	27	9
Ox	14.52	43.56	33	11
Fuel:Ox Ratio	9:11	9:11	9:11	9:11
Prop Mass	0.132	0.396	0.3	0.1

 

Edited March 11, 2018 by RuBisCO
number OCD