Injector efficiency is the pressure in the combustion chamber divided by the pressure available just before the injectors. The injector efficiency can also be viewed as one minus the ratio of the pressure drop across the injector. An ideal injector has an injector efficiency of one and a junkyard injector has an injector efficiency of point four. Generally there is a tradeoff between injector efficiency and combustion efficiency because an injector that atomizes fluid into smaller drops will drop more pressure than one which atomizes fluid less. The injector efficiency can be used along with the pump boost and tank pressure to calculate the chamber pressure.

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

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

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