Rocket Main Tank

Rocket Fuel tanks

In modern launchers, two tanks are used, one for fuel and one for the oxidizer, but it has not always been the case. The Redstone rocket for example used a single tank with an internal separation, as we can see below.

Sloshing and other effects

Special care must be taken to avoid sloshing and vortexes in the tanks, that may lead to bubbles in propellant flow.

Wall thickness and material

Tank material mostly depend on money and on what's available on the market. For robust tanks, we will use 6061 Aluminium or steel.

The thickness of the tank walls obviously depend on the internal pressure, but also on the diameter of the tank. See [1]. Aluminium walls can be 2mm thick and 0.4m wide for a pressure up to 13 bar with no safety factor.

Accessories

Engine fuel supply pipe and valve, tank pressure sensor, fill and drain pipes and valves.

For a cryogenic fuel or a high vapour pressure fuel tank: pressure relief valve, venting valve.

Thermal insulation

Cryogenic fuel tanks benefit from being insulated, which limits vaporization or even prevents boiling.

A list of thermal conductivities (k) is available on Wikipedia.

Material	k (mW/m.K)	density (kg/m3)	availability,comments
PU foam	22	a density of 24 to 32 (1.5 to 2 LB/cu.ft) should be enough	readily available, cheap, sprayedq
Expanded polystyrene	32 to 38	40 to 15 (resp.)	readily available in boards, cheap
cotton	around 30		readily available, cheap
mineral insulation	around 40
neoprene	54	960	readily available, cheap, heavy

A more precise list of low conductivity materials is available here.