Are there any guidelines for the amount of fuel units to volume in parts?

[CommandantAce]

Are there any guidelines for the amount of fuel units to volume in parts? Any general rules for assigning mass to parts?

[Starman4308]

Are there any guidelines for the amount of fuel units to volume in parts? Any general rules for assigning mass to parts?

The typical conversion you see in RealFuels is that 1 unit of LF or oxidizer is about 5L of fuel, and 1 xenon seems to be about 0.1L.

For mass, a tonne is a tonne. RealFuels does knock down the mass of fuel tanks a lot, but that is because KSP fuel tanks have unrealistically low fuel/dry mass ratios.

[CommandantAce]

Thanks for the bit of info. I think the answer I seek is hidden in the specification of the stock parts. I was hoping someone had created a spreadsheet all ready. My question is, in other words, If I create cylinder part X high and Y wide and I want to make it a fuel tank. How would one calculate its mass and capacity?

[passinglurker]

This should help http://wiki.kerbalspaceprogram.com/wiki/Parts#Liquid_Fuel_Tanks the standard 1.25 and 2.5 fuel tanks at the very least follow a pattern. going off that list you need would need .0625 tons of dry mass per 100 units of LFO(45 LF, 55 O). 100 units of LFO will fit in a volume the size of a FL-T100(a cylinder I believe is 1.25 meters in diameter and .625 meters tall but don't quote me on that) as such a FL-T200 is twice as tall and holds twice as much, and the FL-T400 is double of that so on and so forth.

Have you looked at The Opensource Part Competition? It would be a perfect place to get started learning to mod as you don't have to come up with an idea(though a fuel tank would fit well with this weeks theme of landers), you don't have to build a whole parts pack, and there are other people working on the same thing at the same time, so if you get stuck, answers are plentiful.

[Streetwind]

One thing to keep in mind is that stock volume units are completely arbitrary. Thinking of units as "5 liters" only works in the RealFuels context. If you stay stock, that breaks down as soon as you look at anything other than liquid fuel/oxidizer. If you map the apparent volume of RCS tanks to the number of units they contain, for example, you get a totally different result. Xenon gas tanks, again, a totally different result. And so on.

The stock values are chosen with playability in mind; the numbers are handwaved intentionally to make sure that the player gets to see numbers in the resource display during flight that are easy to work with. They are neither very small nor very large numbers. Just a few tens up to a few thousands - perfectly good everyday numbers that even a child has no problems with. As soon as you get into realism conversion mods, you'll immediately notice that the numbers you end up with while using them are anything but simple. TAC Life Support is a 'great' example: it started out with arbitrary volume units that were easy to handle, and then randomly decided to convert to real volume units. Now you specify the resource consumption of your Kerbals in numbers with eight decimal places, and some resources are present in amounts smaller than 1 unit while others go into the hundreds at the same time. The large storage modules meanwhile can post absolutely excessive numbers.

This is sort of a tradeoff you need to decide on making when you create a tank part. Do you go realistic for realism's sake, or do you go unrealistic for playability's sake? There's people who prefer the one approach, and there's people who prefer the other.

Edited December 18, 2014 by Streetwind

[NathanKell]

Yep, RO totally lacks playability. That's why the two thousand people who downloaded it don't play it, I'm sure.

That said, the rest of your post (absent the digs) is spot on: stock numbers don't make any sense, so you'll go mad trying to figure out a volume : units correspondence. At best you see how big your part is in relation to a comparable stock part, and go from there.

[CommandantAce]

This should help http://wiki.kerbalspaceprogram.com/wiki/Parts#Liquid_Fuel_Tanks the standard 1.25 and 2.5 fuel tanks at the very least follow a pattern. going off that list you need would need .0625 tons of dry mass per 100 units of LFO(45 LF, 55 O). 100 units of LFO will fit in a volume the size of a FL-T100(a cylinder I believe is 1.25 meters in diameter and .625 meters tall but don't quote me on that) as such a FL-T200 is twice as tall and holds twice as much, and the FL-T400 is double of that so on and so forth.

Lurker smells what Ace is cookin! There is a pattern there and it would helpful to know for creating stock-alike parts and such. I almost forgot about the data in the Wiki, most of what is needed is there. All that is missing is the dimensions of the parts. What is the height of a jumbo-64 for starters?

[passinglurker]

Lurker smells what Ace is cookin! There is a pattern there and it would helpful to know for creating stock-alike parts and such. I almost forgot about the data in the Wiki, most of what is needed is there. All that is missing is the dimensions of the parts. What is the height of a jumbo-64 for starters?

Actually now that I think about it finding the height of a part like a fuel tank is rather simple just go into the part.cfg and measure the distance between the attachment nodes

PART
{
name = fuelTank3-2
module = Part
author = NovaSilisko

mesh = model.mu
rescaleFactor = 1

node_stack_top = 0.0, [B][U]3.75[/U][/B], 0.0, 0.0, 1.0, 0.0, 2
node_stack_bottom = 0.0, [B][U]-3.75[/U][/B], 0.0, 0.0, 1.0, 0.0, 2
node_attach = 1.25, 0.0, 0.0, 1.0, 0.0, 0.0, 1

TechRequired = heavierRocketry
entryCost = 24200
cost = 12800
category = FuelTank
subcategory = 0
title = Rockomax Jumbo-64 Fuel Tank
manufacturer = Rockomax Conglomerate
description = The largest tank available from Rockomax, the Jumbo-64 holds a vast amount of fuel in a friendly orange insulated container. Contrary to popular belief, the Jumbo-64 is NOT orange flavored and should NOT be tasted.

So according to its part.cfg a jumbo-64 should be 7.5 meters tall.

[CommandantAce]

...and here it is. For standard 2.5 and 1.25 fuel tank parts there are 200 units of fuel per ton.

Fuel = volume * 173.93

Mass wet = volume * 0.24

Mass dry = Volume * 0.03

It's all interesting, I'd like to know the numbers for the MK2 parts. Finding the Volume of those is going to be tricky. Or easy if you have already exported the model. Then the 3D program can tell you and you can tell me. Ace!

I need to know!

Edited December 27, 2014 by CommandantAce

[CaptainKipard]

I remember that someone made a table of all the different parts with the amounts of resources and densities based on part dimensions.

I can't seem to find it right now.

[Talavar]

Are there any guidelines for the amount of fuel units to volume in parts? Any general rules for assigning mass to parts?

You can very easily calculate what should be in a container by size, by comparing what is in other fuel canisters to this chart, http://www.science.co.il/Formula.asp

1: use the parts available and run them through the chart. then do "fuel/volume".

2: run your new part through the chart and get volume.

3: multiply volume by your previously found number from step 1

You now have a new part that is balanced for the game. It's not really that complicated once you break it down.

However, if you need an exact number and cant figure it out, PM me and I'll do the crunch for you.

Edited December 25, 2014 by Talavar

[CaptainKipard]

I remember that someone made a table of all the different parts with the amounts of resources and densities based on part dimensions.

I can't seem to find it right now.

I found it.

[CommandantAce]

I found it.

I'd check the numbers on that. More then a spreadsheet I am interested in the formula by which a parts specifications can be generated. It is not necessary for existing parts but for modders making new fuel tanks, it might be useful.

[CaptainKipard]

There is no formula. The numbers in the cfg are volumes. Just work out the volume of your tank.