A method of generating power from at least one heat source associated with a flight vehicle, the method comprising: advancing the flight vehicle at a flight speed of at least Mach 3; circulating a first working fluid through a first fluid loop including, in sequence: compressing the first working fluid through a first compressor; heating the first working fluid through a first heat intake of the first fluid loop, wherein the first heat intake of the first fluid loop is thermally coupled to the at least one heat source associated with the flight vehicle, the at least one heat source associated with the flight vehicle comprising a first surface of the flight vehicle; expanding the first working fluid in a first thermal engine to generate a first work output from the first thermal engine; cooling the first working fluid; and recirculating the first working fluid to the first compressor; circulating a second working fluid through a second fluid loop including, in sequence: pressurizing the second working fluid through a fluid pressure increasing device; exchanging heat from the first working fluid to the second working fluid through a recuperator; expanding the second working fluid in a second thermal engine to generate a second work output from the second thermal engine; cooling the second working fluid; and recirculating the second working fluid to the fluid pressure increasing device; generating a first source of electric power by operably coupling the first work output of the first thermal engine to a first generator; and generating a second source of electric power by operably coupling the second work output of the second thermal engine to a second generator, wherein the first working fluid comprising a first supercritical working fluid. advancing the flight vehicle at a flight speed of at least Mach 3; circulating a first working fluid through a first fluid loop including, in sequence: compressing the first working fluid through a first compressor; heating the first working fluid through a first heat intake of the first fluid loop, wherein the first heat intake of the first fluid loop is thermally coupled to the at least one heat source associated with the flight vehicle, the at least one heat source associated with the flight vehicle comprising a first surface of the flight vehicle; expanding the first working fluid in a first thermal engine to generate a first work output from the first thermal engine; cooling the first working fluid; and recirculating the first working fluid to the first compressor; compressing the first working fluid through a first compressor; heating the first working fluid through a first heat intake of the first fluid loop, wherein the first heat intake of the first fluid loop is thermally coupled to the at least one heat source associated with the flight vehicle, the at least one heat source associated with the flight vehicle comprising a first surface of the flight vehicle; expanding the first working fluid in a first thermal engine to generate a first work output from the first thermal engine; cooling the first working fluid; and recirculating the first working fluid to the first compressor; circulating a second working fluid through a second fluid loop including, in sequence: pressurizing the second working fluid through a fluid pressure increasing device; exchanging heat from the first working fluid to the second working fluid through a recuperator; expanding the second working fluid in a second thermal engine to generate a second work output from the second thermal engine; cooling the second working fluid; and recirculating the second working fluid to the fluid pressure increasing device; pressurizing the second working fluid through a fluid pressure increasing device; exchanging heat from the first working fluid to the second working fluid through a recuperator; expanding the second working fluid in a second thermal engine to generate a second work output from the second thermal engine; cooling the second working fluid; and recirculating the second working fluid to the fluid pressure increasing device; generating a first source of electric power by operably coupling the first work output of the first thermal engine to a first generator; and generating a second source of electric power by operably coupling the second work output of the second thermal engine to a second generator, wherein the first working fluid comprising a first supercritical working fluid.