SUSAN – what is NASA’s subsonic single aft engine aircraft all about?

Designed to minimize environmental impacts and introduce innovative technologies for sustainable subsonic regional transport aircraft, “SUSAN”- an acronym for SUbsonic Single Aft eNgine, is NASA’s advanced hybrid-electric aircraft concept.

Reportedly, the concept uses a 20MW Electrified Aircraft Propulsion (EAP) system to enable advanced Propulsion Airframe Integration (PAI) in transport category aircraft.

With an ultimate goal of hitting net-zero emissions, SUSAN is touted to reduce emission levels by 50%, incorporating the use of alternative fuels to improve fuel efficiency and reduce energy consumption while retaining the speed, size, and range capabilities of large regional aircraft.

NASA Glenn Research Centre

According to reports, NASA is specifically interested in technologies with a viable risk reduction path through ground and flight testing within two years. These technologies should have the ability to potentially transition into the large uncrewed aerial vehicle market ($18B with a 12% growth rate) or the emerging air taxi and small electric plane markets.

Basic requirements for the components are:

  • Generator – 100 kW capable of powering four independent 100V DC buses
  • Energy Storage – Capable of providing a minimum of 100 kW over five minutes
  • Wing mounted propulsors – 5-10 kW 
  • Aft thruster – 75kW high propulsive efficiency in fuselage wake
  • Alternative Fuel Hybrid Engine – 150kW split 50%/50% between aft fan and generator
  • Fuel Storage – should allow two hours of continuous full-power operation of the engine

Tech and specs

Featuring a 20 MW Electrified Aircraft Propulsion (EAP) system which enables advanced propulsion airframe integration (PAI) for aerodynamic benefits, and helps reduce energy use and fuel burn.

SUSAN also features a hybrid powertrain with a single aft turbofan engine producing thrust and electrical power for distributed wing-mounted engines.


Deep Redundancy is provided with a single-use battery that can provide power to the aircraft In the event of engine failure.

Built to carry a maximum of 180 passengers with a 750-mile economic range and a 2,500-mile design range, SUSAN will operate using existing airport infrastructure and current airspace management systems. This eliminates the need for redesigning airports to accommodate new aircraft and ensures effective implementation into the global aircraft fleet.

SUSAN leverages various EAP technologies such as the 1.4 MW High-Efficiency Megawatt Motor (HEMM), the High-Efficiency Electrified Aircraft Thermal Research (HEATheR) power converter, and several advanced material technologies. These innovative components help strengthen the power and thermal management for the aircraft to operate safely at high altitudes and ensure minimal weight for efficient flight.

Therefore, this concept is projected as a new way of making modern aircraft more fuel efficiency and cost-effective through its unique design and hybrid-electric power system.

Collaboration with key industrial players would be instrumental in demonstrating and transitioning these technologies to viable commercial products.



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