Silent, Solid-State Propulsion for Advanced Air Mobility Vehicles - NIAC Phase I Final Report

Propeller-driven uncrewed aircraft for urban and suburban package delivery are in development. These aircraft may be able to deliver packages to customers more quickly and at a lower cost, relative to ground delivery vans with human drivers. However, noise generated by their propellers can annoy local residents, leading to community opposition.

Electroaerodynamic (EAD) propulsion is a novel means of generating thrust without any moving parts, by using strong electric fields to ionize and accelerate air. Because EAD thrusters have no moving parts, they are almost silent in some applications. EAD-powered aircraft may therefore be able to complete urban package delivery missions without community opposition to noise. Multistaged ducted (MSD) thrusters consist of multiple EAD electrode stages enclosed inside a duct. It is shown both theoretically and through experiments that MSD thrusters are more efficient and thrust-dense than their exposed counterparts. This is in part because the duct contributes to thrust, as with ducted fans.

Two MSD-powered uncrewed aircraft configurations are presented: a monoplane and a box wing. Both are capable of vertical takeoff and landing; their MSD thrusters tilt vertically to provide thrust in hover, then tilt horizontally for wingborne flight. They were designed and optimized using a multidisciplinary optimization framework, incorporating a one-dimensional physics-based MSD thruster model, coupled with aerodynamic, structural, weight, and power-electronics models.

While both aircraft concepts can fly a nominal out-and-back urban package delivery mission, their feasibility is contingent on four key technological modeling parameters: thruster ionization energy, stage loss coefficient, power-converter specific power, and battery specific power. Advances in all four areas are required, relative to today’s state-of-the-art. Future work should focus on characterizing and improving these technologies.