Abstract: A powerplant is provided that includes a flowpath, a combustor and a water extraction system. The combustor is configured to generate combustion products and direct the combustion products through the flowpath. The combustion products are configured from or otherwise include water vapor. The water extraction system is arranged with the flowpath downstream of the combustor. The water extraction system includes a condensation seeder and a collector. The condensation seeder is configured to direct a plurality of small water droplets into the flowpath to promote condensation of the water vapor to grow the small water droplets into a plurality of large water droplets. The collector is configured to collect the large water droplets.