Design and Performance of the NASA SCEPTOR Distributed Electric Propulsion Flight Demonstrator

Abstract

Distributed Electric Propulsion (DEP) technology uses multiple propulsors driven by electric motors distributed about the airframe to yield beneficial aerodynamic-propulsioninteraction. The NASA SCEPTOR flight demonstration project will retrofit an existing internal combustion engine-powered light aircraft with two types of DEP: small "high-lift" propellers distributed along the leading edge of the wing which accelerate the flow over the wing at low speeds, and larger cruise propellers located at each wingtip for primary propulsive power. The updated high-lift system enables a 2.5x reduction in wing area as compared to the original aircraft, reducing drag at cruise and shifting the velocity for maximum lift-to-drag ratio to a higher speed, while maintaining low-speed performance. The wingtip-mounted cruise propellers interact with the wingtip vortex, enabling a further efficiency increase that can reduce propulsive power by 10%. A tradespace exploration approach is developed that enables rapid identification of salient trades, and subsequent creation of SCEPTOR demonstrator geometries. These candidates were scrutinized by subject matter experts to identify design preferences that were not modeled during configuration exploration. This exploration and design approach is used to create an aircraft that consumes an estimated 4.8x less energy at the selected cruise point when compared to the original aircraft. Nomenclature = coefficient of drag 0 = coefficient of drag at zero lift = coefficient of lift = maximum coefficient of lift ⁄ = ratio of drag to dynamic pressure = battery specific energy = energy use per unit distance, conventional configuration = energy use per unit distance, distributed electric propulsion configuration = aircraft gross weight ℎ = altitude above mean sea level = induced drag constant ⁄ = ratio of lift to drag ( ⁄ ) = maximum ratio of lift to drag = mass of battery pack = power consumption of aircraft at cruise = specific excess power (instantaneous rate of climb capability) = rate of descent = range parameter at cruise power, no reserves = efficiency multiplier = velocity at cruise 0 = stall speed in the landing configuration , ∞ = airspeed velocity

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Takeoff and Performance Trade-Offs of Retrofit Distributed Electric Propulsion for Urban Transport

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Comparison of Aero-Propulsive Performance Predictions for Distributed Propulsion Configurations

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