Ultra-Low Noise Vertical Takeoff and Landing, or Development of an Uber Self-Flying, Helipad-Capable, Quiet V-ESTOL Personal Transporter Integrated Flight Demonstrator

Several aspects of this research are completely unique compared to prior attempts to achieve low noise vertical lift solutions, and are an artifact of the incredible opportunity that electric propulsion offers.1. A unique type of vertical lift propulsor is being designed/analyzed/developed to push blade passage frequency harmonics above the human audible range, while also having low tip speeds to limit the other low broadband noise components of community noise. Typically these two requirements would be conflicting and mutually exclusive, however, use of distributed electric motors enables small propulsors to be designed in this way, with tight integration across the airframe. This strategy is shown in the figure to right, comparing the new 20,000 Hz and 285 ft/sec propulsor to 1.5' and 9.7' diameter propellers which have blade passage harmonics at the peak human hearing frequencies along with almost twice the tip speeds (which results in higher broadband noise). A FY17 deliverable includes rapid testing of this propulsor.2. Use of these small propulsors, each capable of 25 lbf thrust, enables their use in far more distributed ways than merely using propellers or fans. This enables advanced concepts to be developed that leverage airframe shielding to a much greater extent for further noise reduction, along with propulsor positioning to achieve directional reflectivity that causes the remaining noise to be focused upwards, and away from the community. Additionally, use of more extreme distribution enables greater spacing across the airframe which provides additional opportunities to ensure robust control across hover and transition flight regimes. New fixed-wing configuration approaches (which also achieve ~5x the Lift/Drag ratio of existing helicopters) are being developed to best leverage these new propulsors to create dramatically improved vertical lift solutions, while also avoiding open prop/rotors that are a danger for close proximity operations. Sub-scale indoor hover testing will investigate the use of distributed thrust control.This research provides a significant potential impact, with community noise being the main obstacle for frequent urban operations. Achieving high L/D ratio and use of electricity-based propulsion also results in a ~30% reduction in operating costs, and when combined with high utilization business models with high productivity vehicles (high cruise speed), the resulting $/mile/passenger in less than half that of helicopters. Validation of these claims are beginning to be echoed by major companies we've reached out during this past year with Airbus just announcing a new major investment initiative into small Urban VTOL Air-Taxi's. (http://www.airbusgroup.com/int/en/news-media/corporate-magazine/Forum-88/My-Kind-Of-Flyover.html)