A feed system keeps a rocket engine supplied with fuel and oxidizer at the right pressure and mixture. Follow the propellant from the tanks, past the valves and pumps, into the thrust chamber.
A propellant feed system is everything between the tanks and the engine: the tanks themselves, the gas that pressurises them, the pipes, the valves and the pumps. Its only purpose is to deliver the right amount of fuel and oxidizer to the thrust chamber at the right pressure, second after second, for as long as the engine fires.
A rocket engine is only as good as its feed system. If the flow stutters, the mixture drifts or the pressure drops, the engine suffers. Drawing the whole chain — tanks, pressurant, lines, valves, pumps, chamber — shows how each part supports the next.
Fuel and oxidizer are stored in two separate tanks, because they would react if they mixed. A pressurant gas, often helium, is fed in from bottles to keep each tank under a small positive pressure, called ullage.
From each tank, pipes run down toward the engine. The ullage pressure keeps liquid moving gently into these lines as the tank drains, so the pumps always have a steady supply to work with.
Propellant valves act as the taps. Opening them starts the flow and lets the engine fire; closing them shuts it down. By setting how far they open, the system can also change how much propellant reaches the chamber and so scale the thrust.
The combustion chamber runs at a pressure far above the tanks. Turbopumps take the propellant from the low-pressure lines and force it up to chamber pressure, in matched pairs so fuel and oxidizer arrive in the right ratio.
Both streams meet in the thrust chamber, where they are injected, mixed and burned. The hot gas is expelled out the back, and the whole feed system — from pressurant to pump — exists to keep that chamber fed correctly.
A small positive pressure, called ullage, keeps liquid flowing into the pumps steadily and stops bubbles forming in the lines. Without it the pumps could pull the liquid apart as the tank drains.
A pressure-fed system pushes propellant with tank pressure alone, which is simple but limits chamber pressure. A pump-fed system uses turbopumps to reach far higher pressure, at the cost of more machinery.
The fuel and oxidizer are handled at different flows and pressures, and they must arrive in a fixed ratio for a clean burn. Matching two pumps to the engine keeps that mixture right.
Partly. Moving a valve changes how much propellant reaches the chamber, which scales the thrust. To stop the engine, the valves simply close and cut the flow.
Fast-moving liquid has inertia, and sharp bends and joints feel that as heavy loads. Sturdy lines and good supports keep the whole system steady under those forces.