Tail Propulsor Generator for NASA SUSAN Sub-Scale Flight Demonstrator

Hinetics performed a detailed study in Phase I to evaluate the integration of a lightweight, high efficiency 150 kW generator-drive subsystem within the SUSAN concept aircraft. Analysis on potential subsystem and system level integration strategies ensured stability and reliability were maintained across all operating conditions of the propulsion system and while maximizing the system level performance. This has set the stage for hardware development for a sub-scale SUSAN demonstration in this Phase II program, helping to increase the TRL of critical technologies for future low carbon aircraft. The Phase II project will include prototype construction of the machine and integration with a Lycoming O-360 engine to de-risk overall system considerations. Because the full scale SUSAN concept utilizes an aft turbine and our topology has clear weight and efficiency benefits at higher shaft speeds, Hinetics will design, build, and demonstrate a higher speed generator for mating to a COTS turboshaft. In parallel, a US-based subcontractor, Beehive Industries, will perform a study on the potential of improving turboshaft efficiencies in the 150 kW power range to become more competitive with combustion engine solutions while maintaining low system mass. The high efficiency and ‘simple’ modular architecture of the Hinetics generator facilitates easy scaling across a broad range of speed and power, and can accommodate both air and liquid-cooling to match the customer’s requirements. Hinetics has demonstrated the world's highest efficiency electric machine topology with exceptional thermal performance across a vast range of speeds and electrical loading. The unique features of the motor include ease of integration within the hybrid system without necessitating additional complex hardware or cooling requirements. The Hinetics team also has patent-pending technology to integrate the motor/generator with the propeller. The generator can be easily configured for simple, indirect liquid cooling with available coolants, and/or axial or centrifugal air cooling depending on the requirements. These features make the Hinetics generator a versatile solution for a variety of hybrid electric aircraft applications. The overall goal of this project is to demonstrate the performance of an integrated engine-generator system with high efficiency, high specific power generator topology for NASA’s hybrid-electric single-aisle commercial airliner concept vehicle. We plan to do this by building the PMSG optimized under Phase I of this project, acquiring a commercial engine, and integrating the engine with electrical sub-system. By doing this, we plan to overcome the challenges in system integration, design of auxiliary systems, system assembly and validate system performance. The integrated system will be tested for full power and will be used to validate the mechanical dynamics and mechanical/electrical transient performance. The proposed generator topology provides best efficiency/specific power at higher speed designs. Thus, a second higher-speed prototype will be designed and built in parallel for integration with a turboshaft engine. Commercial ICE and turboshafts have been identified and preliminary checks have been performed to ensure availability and compatibility of these engines. The end result of this Phase II is two fully integrated powertrains, one IC-based and one turbine-based.
Benefits: Subsonic Single Aft Engine (SUSAN) Electrofan would be the major targeted application for this motor design and system integration study. It will also be applicable to any of the drivetrain testing and qualification programs of NASA in a similar power scale with a few varying details such as cooling availability and drivetrain. While this study is targeted at the generator coupled to aft engine, it is directly applicable to a distributed propulsor or the propulsor in any turbo-electric, hybrid-electric or fully electric concept. In addition, the drivetrain developers can potentially use this study to test the sub-systems and to validate the performance and reliability of electric aircraft drivetrains.