NASA Samarai hybrid-electric VTOL personal-aircraft concept

NASA concept for a vertical take-off and landing personal aircraft that combines a lightweight electric lift system with an internal-combustion cruise engine. This provides longer range than possible on battery power alone. The single-blade prop-rotors are stopped in flight to act as wings. This reduces drag. The concept takes its name from the single-blade rotor's similarity to the samara, or maple seed.