The invention relates to a device for supplying fuel for a rocket propulsion unit, comprising a first (6a) and at least a second (7a) fuel circuit, wherein each fuel is brought to an high energy level by a pump (12, 29) and is supplied for combustion by means of injection elements (33), wherein the first fuel is heated in cooling channels (16) extending in a propulsion chamber wall (17) before the fuel is supplied for combustion and wherein the first fuel is subsequently fed to at least the turbines assigned to the pumps (12, 29), wherein a heat exchanger (100) is provided in which the fuel coming from the turbines (24, 28) establishes heat exchange with the fuel coming from a pump (12, 29). The invention also relates to a heat exchanger for utilization in said device for fuel supply.