The pressure in the Space Shuttle's main engines must be very high to get the vehicle off the ground (with the SRB assist, of course). With such high pressures inside the engine, how do you inject fuel into the engine? I understand that the fuel is passed around the engine so that it cools the nozzle, so that the exhaust doesn't melt it, then into the engine. However I always assumed that the pressure of the fuel going into the engine must be higher than the pressure the exhaust gases exert. If so, how does the Shuttle pump such high pressure fuel into the engines?