Tank pressure is the pressure in the propellant and reactant tanks. Higher tank pressures lead to higher combustion pressures; but, require stronger walls. Inexpensive amateur liquid rockets often have relatively low pressure steel tanks which can withstand twenty atmospheres. Expensive rockets sometimes use high pressure graphite tanks which can withstand fifty atmospheres. Really expensive rockets will use low pressure internally stiffened tanks which can only withstand ten atmospheres along with pumps. Low pressure tanks must have structural stiffeners because their walls are thin and have insufficient stiffness on their own. Nasa rocket tanks are generally engineered to have only barely enough strength, such that they have to be moved carefully. Russian rocket tanks are engineered to be robust and can be moved by cranes with only a couple of attachment points. Tank pressure can be used along with injector efficiency and pump boost to calculate the chamber pressure.

chamber pressure = injector efficiency * ( pump boost + tank pressure )

tank mass = tank pressure * 3.0 / effective tensile * ( fuel volume ratio + oxidizer volume ratio + propellant volume ratio )
 
 

This is used in astropolis.html, bipropellantrocket, tripropellant rocket, pumped rocket and rocket cost.
 
 

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