A power generating unit in accordance with the present invention comprises a pressurized gas source (44) providing pressurized gas containing oxygen to be used in combustion of a fuel; a combustor (42) for providing pressurized gas produced by combustion of a mixture of the pressurized gas provided to the combustor by the pressurized gas source and fuel provided to the combustor by a fuel supply (48); a first turbine (68) driven by pressurized gas produced by the combustor; a gear box (70) driven by the turbine having an output shaft (72); a fuel pump (46) disposed within the fuel supply having a pair of input shafts (64 and 76) for providing pressurized fuel to the combustor in response to rotation of either of the input shafts; a motor (58) coupled to the pressurized gas source having a drive shaft (60) which rotates in response to the pressurized gas applied from the gas source; and a coupling mechanism (62 and 74), coupled to the shafts, for applying driving torque to the fuel pump during rotation of the pressurized gas to the combustor from the input shaft which is rotating at a higher velocity.