Abstract: UAV (400, 500, 600) systems and methods for simulation of reduced-gravity environments are disclosed. A UAV (400, 500, 600) system has an ascent vehicle (104), comprising ascent thrust means, and an aerodynamic, free fall descent UAV (102, 706), comprising descent thrust means. The ascent vehicle (104) comprises means to convey the descent UAV (102, 706) to a drop altitude (108), and the descent UAV (102, 706) is separable from the ascent vehicle (104). The descent thrust means is operable, following separation of the descent UAV (102, 706) from the ascent vehicle (104), to provide a thrust component in a descent direction (256), for countering air resistance on the UAV (400, 500, 600). The descent UAV (102, 706) may comprise a sensor system and controller (204), and the descent thrust means may comprise a ducted fan system.