A method of providing cooling and generating power on board a flight vehicle using heated inlet air associated with the flight vehicle, the method comprising: advancing the flight vehicle at a flight speed of at least Mach 3; circulating a first working fluid (122 or 252) through a first fluid loop (120 or 250) including, in sequence: compressing the first working fluid (122 or 252) through a first compressor (130 or 254); heating the first working fluid (122 or 252) through an inlet air heat exchanger, the inlet air heat exchanger including an inlet air line fluidly communicating with the heated inlet air and a first air-to-loop line (247 or 251) located in thermally coupled relation to the inlet air line; expanding the first working fluid (122 or 252) in a first loop thermal engine (150 or 258) to generate a first work output (152 or 260) from the first thermal engine (150 or 258); cooling the first working fluid (122 or 252); and recirculating the first working fluid (122 or 252) to the first compressor (130 or 254), the method further comprises: circulating a second working fluid (122 or 252) through a second fluid loop (120 or 250) including, in sequence: compressing the second working fluid (122 or 252) through a second compressor (130 or 254); heating the second working fluid (122 or 252) through the inlet air heat exchanger, the inlet air heat exchanger including a second air-to-loop line (247 or 251); expanding the second working fluid (122 or 252) in a second thermal engine (150 or 258) to generate a second work output (152 or 260) from the second thermal engine (150 or 258); cooling the second working fluid (122 or 252); and recirculating the second working fluid (122 or 252) to the second compressor (130 or 254). advancing the flight vehicle at a flight speed of at least Mach 3; circulating a first working fluid (122 or 252) through a first fluid loop (120 or 250) including, in sequence: compressing the first working fluid (122 or 252) through a first compressor (130 or 254); heating the first working fluid (122 or 252) through an inlet air heat exchanger, the inlet air heat exchanger including an inlet air line fluidly communicating with the heated inlet air and a first air-to-loop line (247 or 251) located in thermally coupled relation to the inlet air line; expanding the first working fluid (122 or 252) in a first loop thermal engine (150 or 258) to generate a first work output (152 or 260) from the first thermal engine (150 or 258); cooling the first working fluid (122 or 252); and recirculating the first working fluid (122 or 252) to the first compressor (130 or 254), compressing the first working fluid (122 or 252) through a first compressor (130 or 254); heating the first working fluid (122 or 252) through an inlet air heat exchanger, the inlet air heat exchanger including an inlet air line fluidly communicating with the heated inlet air and a first air-to-loop line (247 or 251) located in thermally coupled relation to the inlet air line; expanding the first working fluid (122 or 252) in a first loop thermal engine (150 or 258) to generate a first work output (152 or 260) from the first thermal engine (150 or 258); cooling the first working fluid (122 or 252); and recirculating the first working fluid (122 or 252) to the first compressor (130 or 254), the method further comprises: circulating a second working fluid (122 or 252) through a second fluid loop (120 or 250) including, in sequence: compressing the second working fluid (122 or 252) through a second compressor (130 or 254); heating the second working fluid (122 or 252) through the inlet air heat exchanger, the inlet air heat exchanger including a second air-to-loop line (247 or 251); expanding the second working fluid (122 or 252) in a second thermal engine (150 or 258) to generate a second work output (152 or 260) from the second thermal engine (150 or 258); cooling the second working fluid (122 or 252); and recirculating the second working fluid (122 or 252) to the second compressor (130 or 254). circulating a second working fluid (122 or 252) through a second fluid loop (120 or 250) including, in sequence: compressing the second working fluid (122 or 252) through a second compressor (130 or 254); heating the second working fluid (122 or 252) through the inlet air heat exchanger, the inlet air heat exchanger including a second air-to-loop line (247 or 251); compressing the second working fluid (122 or 252) through a second compressor (130 or 254); heating the second working fluid (122 or 252) through the inlet air heat exchanger, the inlet air heat exchanger including a second air-to-loop line (247 or 251); expanding the second working fluid (122 or 252) in a second thermal engine (150 or 258) to generate a second work output (152 or 260) from the second thermal engine (150 or 258); cooling the second working fluid (122 or 252); and recirculating the second working fluid (122 or 252) to the second compressor (130 or 254). cooling the second working fluid (122 or 252); and recirculating the second working fluid (122 or 252) to the second compressor (130 or 254).