Subsonic Single Aft Engine (SUSAN) Transport Aircraft Concept and Trade Space Exploration

A Review of Novel and Non-Conventional Propulsion Integrations for Next-Generation Aircraft

“…NASA is currently exploring innovative alternatives aimed at reducing the number of hydrocarbon fuel-consuming and power-generating engines from two to one. An example of such a concept in development is the Subsonic Single Aft Engine (SUSAN) Electrofan [179], designed to achieve a 20 MW class Electric Aircraft Propulsion (EAP) system, contributing to the aircraft's electrification and fuel consumption reduction. The SUSAN Electrofan features a series/parallel partial hybrid-electric powertrain, utilizing a fuelburning aft-fuselage propulsor connected to Megawatt-class power generators that support wing-mounted electric propulsors (see Figure 44).…”

“…The DEP systems each adopt an integrated mail-slot nacelle configuration that helps to reduce the wetted area associated with the inclusion of many small individual propulsors. Preliminary low-order multidisciplinary design optimization evaluations suggest that, compared to a reference aircraft based on 2020 technology levels with the Boeing 737-8 as a reference, the SUSAN Electrofan could potentially achieve an 11.1% reduction in block fuel for a 750 nm mission [179,180]. However, the configuration is still under extensive investigation, and different developments and updates are to be expected.…”

“…In this context, it is possible to also consider combinations of different propulsion technologies and their integration into advanced aircraft concepts. This is the case, for example, of the unconventional aircraft architectures studied for the concept SUSAN (Subsonic Single Aft Engine) developed by NASA [179,279] and already cited in Section 3.3 for the case of distributed propulsion. The project proposed different regional aircraft configurations integrating several levels of propulsive technological innovation, such as a single main propulsion unit installed in the aft fuselage area, distributed propulsion, counter-rotating prop-fans and open-rotors, the option of using propulsive elements for boundary layer ingestion, and a hybrid-electric powertrain.…”

“…Another problem that may prevent the effective feasibility of this solution lies in the event of a rotor blade failure, which could critically damage the tail surfaces; (c) is a configuration very similar to the previous one, but to solve the problems related to the installation of the aft open-rotor, the latter is replaced with a ducted turbofan; the protective ventral fin is therefore also removed; and (d) has a T-tail architecture with an aft ducted turbofan and with sixteen electric motors powering ducted fans housed within sub-wing integrated nacelles. The multidisciplinary design studies proposed in [179,279] have preliminarily estimated possible significant reductions in block fuel consumption for the investigated configurations. Although these studies are still conceptual, they indicate interesting directions for the synergetic development of disruptive aircraft and propulsion technologies.…”

Concept Evaluation of Radical Short–Medium-Range Aircraft with Turbo-Electric Propulsion

“…Much of the work reported is related to regional aircraft applications. More specifically for SMR mission aircraft, for example, Jansen et al [4] report on the design and evaluation of hybrid electric aircraft including distributed propulsion, where they investigate the aircraft-level feasibility and potential for a 2500-mile design range and 180-passenger capacity.…”