Fantastic! Great idea for tank to use these parts from space shuttle, I have to memorise it :) I have a small problem with first wheels mudguards - they look to be too high, to much space between the wheel and the mudguard, but I assume that's the cost of the technic they are made in - using these technic "chair" pannels?
BTW, I am also having difficulties with making the physical tank for LNG tanker trailer, but in bigger scale and more technic / less system and I thought and tried using the curved quarter gear racks 11x11 studs with lift arms attached to them on soft axles, which makes it 21 or 23 studs diameter (it depends whether you put the lift arms directly between gear racks or on the gear racks as second, outer layer). As for now I have postponed this project, due to many circumstances (one of them is the cost of so many soft axles, experimenting with non-Lego hoses which looks very similar to Lego pneumatic hoses).