Reliability and Performance Trade Studies for NASA’s Subsonic Single Aft Engine Aircraft

NASA’s SUbsonic Single Aft eNgine (SUSAN) Aircraft is regarded as a transformational aircraft concept to make commercial flight more efficient. Its series/parallel-partial hybrid propulsion architecture, with sixteen electric propulsors (EP) and an aft turbofan engine, was previously sized for weight and performance objectives without a quantitative safety assessment. To fill this gap, an integrated performance–reliability framework was developed to evaluate certification-relevant “��-EP inoperative” failure conditions under FAA Part 25.1309 regulations by: 1) embedding cable weights and losses into a graph-based propulsion system analysis; and 2) deriving minimal cut sets directly from a propulsion system architecture matrix. Five failure modes (1-, 2-, 4-, 8-, and 16-EP inoperative) are analyzed on SUSAN’s baseline propulsion architecture and four others with redundant electric generator–motor cross-connection schemes. Relative to the baseline, added redundancy increases block fuel by at most 1.5% but, depending on the failure mode, improves system-level failure intensity by up to seven orders of magnitude. These results enable identification of Pareto-optimal system architectures for two objectives: 1) minimum fuel burn; and 2) largest excess safety margin. In addition, the formulation and analyses used for SUSAN enable transparent reuse in future safety trade studies for electrified transport aircraft.