Propellant usage is the amount of reactant used to power the pump divided by the amount of reactant available. A propellant usage of zero means that there no pump is being used, the reactants are injected directly from pressurized tanks. A propellant usage of one means that there all reactants available are used to power the pump.

Pumps deliver higher combustion chamber pressures and permit lower tank pressure, both of which increase overall performance. However, they generally cost more than the rest of the rocket, partly because of their direct cost and partly because of their indirect cost of lower reliability. Pumps are still worth it in resuable rockets because of the performance boost they provide. In expendable rockets, pumps are generally not quite worth it. Propellant usage is used along with pump efficiency and working temperature to calculate the propellant energy which is in turn used to calculate pump boost and pump power.

propellant energy = propellant usage * pump efficiency * working temperature * 8,314 J * K / kmol / 0.2
 

combustion exhaust = combustion ratio / exhaust molecular

uncombustion = 1.0 - combustion ratio

pump energy = propellant energy * propellant mass ratio / propellant molecular + propellant energy * reactant propellant usage * ( fuel mass ratio * ( uncombustion / fuel molecular + combustion exhaust ) + oxidizer mass ratio * ( uncombustion / oxidizer molecular + combustion exhaust ) )
 

pump boost = pump energy / pump need
pump power = pump energy * fuel flow
 
 

This is used in pumped rocket and rocket cost.
 
 

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