A method for generating power in a system (10, 100, 200, 300) that includes a supercritical fluid cycle (92, 102, 202, 302) having a supercritical fluid flowing therethrough, and an air-breathing cycle (94, 104, 204, 304) having air flowing therethrough that does not mix with the flow of the supercritical fluid, the method comprising the steps of: a. activating a compressor input valve (142a, 142b, 142x, 342a, 342b, 342x) and a compressor discharge valve (144a, 144b, 144x, 344a, 344b, 344x) of a first core of a plurality of cores (60, 70, 80) disposed along the supercritical fluid cycle, each core including a compressor (62, 72, 82, 110a, 110b, 110x, 310a, 310b, 310x), and a turbine (64, 74, 84, 114a, 114b, 114x, 314a, 314b, 314x); b. directing the supercritical fluid to the compressor of the first core; c. compressing the supercritical fluid in the compressor of the first core such that the supercritical fluid is discharged from the compressor of the first core as a compressed supercritical fluid; d. directing at least a portion of the compressed supercritical fluid from the compressor of the first core to at least one heat exchanger; e. transferring heat to the compressed supercritical fluid from the air in the air breathing cycle in the at least one heat exchanger (32, 36, 132, 134, 136, 138, 410, 418) such that the compressed supercritical fluid is discharged from the at least one heat exchanger as a heated supercritical fluid; f. activating a turbine input valve (146a, 146b, 146x, 346a, 346b, 346x) and turbine discharge valve (148a, 148b, 148x, 348a, 348b, 348x) for the turbine of the first core; g. directing at least a portion of the heated supercritical fluid from the at least one heat exchanger to the turbine of the first core; h. expanding the heated supercritical fluid in the turbine of the first core such that the first core generates a first level of power in an output device (120a, 120b, 120x, 220, 320a, 320b, 320x); and i. activating at least a second core of the plurality of cores (60, 70, 80) such the second core increases the first level power generated in the output device (120a, 120b, 120x, 220, 320a, 320b, 320x) to a second level of power that is greater than the first level of power. a. activating a compressor input valve (142a, 142b, 142x, 342a, 342b, 342x) and a compressor discharge valve (144a, 144b, 144x, 344a, 344b, 344x) of a first core of a plurality of cores (60, 70, 80) disposed along the supercritical fluid cycle, each core including a compressor (62, 72, 82, 110a, 110b, 110x, 310a, 310b, 310x), and a turbine (64, 74, 84, 114a, 114b, 114x, 314a, 314b, 314x); b. directing the supercritical fluid to the compressor of the first core; c. compressing the supercritical fluid in the compressor of the first core such that the supercritical fluid is discharged from the compressor of the first core as a compressed supercritical fluid; d. directing at least a portion of the compressed supercritical fluid from the compressor of the first core to at least one heat exchanger; e. transferring heat to the compressed supercritical fluid from the air in the air breathing cycle in the at least one heat exchanger (32, 36, 132, 134, 136, 138, 410, 418) such that the compressed supercritical fluid is discharged from the at least one heat exchanger as a heated supercritical fluid; f. activating a turbine input valve (146a, 146b, 146x, 346a, 346b, 346x) and turbine discharge valve (148a, 148b, 148x, 348a, 348b, 348x) for the turbine of the first core; g. directing at least a portion of the heated supercritical fluid from the at least one heat exchanger to the turbine of the first core; h. expanding the heated supercritical fluid in the turbine of the first core such that the first core generates a first level of power in an output device (120a, 120b, 120x, 220, 320a, 320b, 320x); and i. activating at least a second core of the plurality of cores (60, 70, 80) such the second core increases the first level power generated in the output device (120a, 120b, 120x, 220, 320a, 320b, 320x) to a second level of power that is greater than the first level of power.