Fuel capacity for fuel tanks?

[1096bimu]

I'm trying to make some fuel tanks but the capacity is confusing me.

See, take the Rockomax X200-16 Fuel Tank, it has a capacity of 1,600 Liters. But a cylinder that size with 2.5 meters diameter would have something like 7,000 liters volume. Even if you count in the rescale factor of 1.25 cubed, around a factor of 2, it is still 3,500 liters, more than twice the actual capacity. What is going on?

[maltesh]

Basically, treat the L as an abbreviation for "Liquid Volume Units," rather than liters. They aren't hard-tied to any measurement at this point, so just use them as a guideline for building your tanks. If your tank appears to have twice the internal volume of the Rockomax X200-16, not many will complain if you give it twice the fuel capacity.

[Greys]

I was dealing with this recently and the basic issue is that units of resource are not liters; they're also not the same between resources.

Based on analyzing the volumes vs resources of a few stock parts I have determined that:

LF/Oxy = 173.913 units/m^3

Monopropellant = 129.87 units/m^3

Xenon = 4875 units/m^3

Battery = 1785.714 units/m^3 & 5.6 tons/m^3 (because electricity doesn't have weight*)

[1096bimu]

I was dealing with this recently and the basic issue is that units of resource are not liters; they're also not the same between resources.

Based on analyzing the volumes vs resources of a few stock parts I have determined that:

LF/Oxy = 173.913 units/m^3

Monopropellant = 129.87 units/m^3

Xenon = 4875 units/m^3

Battery = 1785.714 units/m^3 & 5.6 tons/m^3 (because electricity doesn't have weight*)

TECHNICALLY ELECTRICITY DOES HAVE WEIGHT!

just kidding, ty for the info

[Supernovy]

Is that based on cylindrical tanks or cylindrical tanks with spherical end caps?

[Greys]

it's based on: FL-T400, FL-R25, PB-X300, and Z-500; I did not confirm the numbers with multiple tanks, partly because sometimes multiple tanks don't exist, so feel free to manipulate the numbers to your liking, nobody really cares.

[Supernovy]

I meant "Are you assuming that the entire tank is available space for fuel or are you assuming there is some kind of internal tank for example with spherical end caps?"

Sorry I wasn't so clear.

[Greys]

just going by the exterior volume

[Mihara]

What about the dry weight of a tank, and also, how exactly does one determine the size of a stock tank exactly anyway?

I want to make large spherical side-bolt fuel tanks by rescaling the round monopropellant tanks, but can't figure out how much dry weight and fuel volume would be appropriate to match stock scales...

[SunJumper]

I was dealing with this recently and the basic issue is that units of resource are not liters; they're also not the same between resources.

Based on analyzing the volumes vs resources of a few stock parts I have determined that:

LF/Oxy = 173.913 units/m^3

Monopropellant = 129.87 units/m^3

Xenon = 4875 units/m^3

Battery = 1785.714 units/m^3 & 5.6 tons/m^3 (because electricity doesn't have weight*)

Note that a litre would be 1000 u/m^3

Also, don't forget solid fuel.

[Greys]

Dry weight you should just wing, it's the weight of the part without the resources, KSP fills in the rest. If you want you can figure out a multiplier that looks right but whatever you do the dry weight on anything relatively small is going to be less than a ton, probably less than 0.5t, so it's not super important; also by the sound of it you'll be in space before they're emptied so it's all inertial mass.

I'm sure there's more than one way to do it but all the stock tanks come in standard widths, the ones I used should all be 1.25m diameter, then you just estimate their length in comparison. One of the parts is about an 6/16ths as long as it is wide, everything else has rounder numbers.

For scaling a part that already exists the rule of thumb is, for every time you double the volume (rescaleFactor = 2), multiply the resource contents by eight (8).