Liquid Fuel Tank Guide

[ArmoredLipid]

This is a guide to using liquid fuel tanks, so as to power jet engines and nuclear-thermal rockets.

In order of efficiency in storing liquid fuel (with some tanks removed, as they obviously were too heavy, ratios being generalized for radial-size tanks, and all tanks having oxidizer removed):

LFB KR 1x2 "Twin-Boar" Liquid Fuel Engine: about 115 units of LF/ton. (this thing is weird).

All of the FL-T, Rockomax, and Kerbodyne tanks: about 156 units of LF/ton.

All of the Mark 2 and 3 LF tanks: about 174 units of LF/ton.

Mark 1 Fuel Tank: 2.250 tons full/400 units LF = 177.77 units of LF/ton.

Mark 0 Fuel Tank: 0.275 tons full/50 units LF = 181.81 units of LF/ton.

Big-S Wing Strake: 0.500 tons full/100 units LF = 200 units of LF/ton.

Big-S Delta Wing: 1.000 ton full/300 units LF = 300 units of LF/ton. 
 

Engineering outcomes: use Big-S Delta Wings for whenever you only need LF, or if those don't fit (for whatever reason) use the Wing Strake. Mark 0 Fuel Tanks require special adapters, and generally aren't worth the extra weight. For instance, my asteroid-grabbing rocket uses a core of Mark 1 tanks with Big-S Wing Strakes surrounding them.

 

Edited August 15, 2018 by ArmoredLipid

[purpleivan]

Not sure about those figures as the Big-S is 2.0 tons full, not 1.0, so works out to 150 units/ton.

That would seem right in terms of balancing compared with say the Mark 1 fuel tank 177.77 units/ton, as you get the capacity plus the benefit of it's lift and heat resistance.

[FinalFan]

300 units per ton would make the Big-S wing an antigravity device.  I don't think that's the sort of "lift" it's designed to give.  

According to the figures I have access to, the wing strake would score 167 and the wing would score just 150.  This makes sense as these parts do not have the disadvantage of wasted oxidizer storage, but the wing has weight devoted to its lift function. 

The parts dedicated to liquid fuel storage are the best at storing liquid fuel.  

[AeroGav]

Cylindrical tanks have best capacity per mass,   wing parts have best capacity per unit of drag.

 

In a spaceplane that uses most of its fuel getting to orbit (even single stage to Minmus or Duna craft fit in this category) , all fuel goes in Big S strakes if possible.      Big S strakes have 20% of the mass, drag and lift of the Big  S wing,   but hold 33% of their fuel, so are the best choice, but part counts can get stupid on larger vessels.     FAT-455 wings are also highly competitive, but lack heat tolerance.

 

For deep space probes,  or insane Matt Lowne spaceplanes  that go single stage to Eeloo or Moho then back again without refuelling ,  most of the fuel is spent out of the atmosphere so the lowest mass option wins.

 

My payload fraction to orbit SSTO  was all liquid fuelled,  and basically keeps its fuel all in strakes.    Here is a more KerbalX friendly version of the extreme machine

https://kerbalx.com/AeroGav/Andromeda

>>352 kn is not a lot of thrust for an orange tank lifter (less than two Swivels put out)..   fortunately this thing is super slick and makes a lot of lift... drag is only 124kn.

 

Because i am lazy ,  i did use a flipped Big S wing as the starting point, then just clipped more and more strakes to the leading and trailing edges till I had the fuel and lift I wanted.  There's a bit in the mk3 to 2.5m adapter up front too , due to shortage of fuel-less alternatives.     

Also if you search the forum recently,  someone posted a challenge for a NERV only SSTO (no jets or rockets,  NERV sole propulsion from sea level ).   The guy who did it used big S strakes.

Edited September 10, 2018 by AeroGav