In a staged combustion cycle rocket engine, the fuel and oxidizer are fed into turbo pumps which are in turn powered by a pre-burner. My question is how do they ensure that the fuel and oxidizer are always fed in the proper amounts into the engine?
As in, there must be a maximum flow rate that the pumps can push fuel and oxidizer into the engine. There must also be a maximum flow rate that the tanks can push fuel and oxidizer into the pumps. But wouldn't that flow rate decrease as the rocket expends the fuel/oxidizer in the tanks? So is there ever any time in which the flow rate of the pump exceeds the flow rate of the incoming fuel/oxidizer from the tanks? In that case, wouldn't gas bubbles form inside the pump? I'm assuming that would be very bad for the engine. How do they account for this problem?