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Electrified Aircraft Propulsion

Description:

Scope Title:

Electrified Aircraft Propulsion (EAP)

Scope Description:

Technical proposals are sought for the development of energy storage systems, power electronic modules for electric aircraft motor drives, and electric machines and converters that will be required for aircraft using turboelectric, hybrid-electric, or all-electric power generation as part of the propulsion system. This subtopic is targeted toward megawatt-class vehicles.

Specifically, novel developments are sought in these areas:

  • Energy storage systems with specific energy >400 Whr/kg at the system level under continuous 2C rate discharge conditions. Materials or strategies to promote rapid charging, novel system designs incorporating passive thermal management, and novel battery designs to passively prevent the propagation of thermal runaway from cell to cell are desirable. This subtopic seeks energy solutions in the Technology Readiness Level (TRL) 3-5 range, appropriate for near-term applications.
  • Converters (inverters/rectifiers) used to convert alternating current (AC) to AC frequency and AC to direct current (DC). Technology should scale to aircraft circuits operating in the 1,000- to 3,000-V range at 500 to 2,000 A. Prototypes can be built at the 100- to 500-V at 10- to 100-A range or at full scale. The converters will be evaluated on the metrics of specific power (kW/kg) and efficiency with objective to exceed 20 kW/kg and 99.5% at full scale.
  • Electric machines for aircraft propulsion used for direct-drive propulsion of fans or propellers or as generators coupled to internal combustion engines, turboprops, or turbofans. Technology should scale to aircraft applications in the 1- to 5-MW range. The electric machines will be evaluated on the metrics of specific power (kW/kg) and efficiency with objective to exceed 20 kW/kg and 98% at full scale.
  • Power electric modules for electric aircraft motor drives that enable high efficiency and high power density. The modules must provide a continuous current rating of at least 250 A, achieve an RDS,on of 3.8 mΩ (at 25 °C), and do so with a 25% margin on Vgs below its absolute maximum rating. The module must achieve a total turn on + turn off switching loss of 12 mJ for a 200-A load while switching 800 V, with a stretch goal of 3 mJ. The module must also be capable of operating at an altitude of 41,000 ft without partial discharge (can be a simulated environment (e.g., vacuum chamber)), and follow DO-160G standards on shock and vibration tolerance. The module must achieve a voltage rating of no less than 1.2 kV. Optionally, it is desirable for the module to have high power density (<24 g per two device phase-leg module, or equivalent), to minimize output capacitance, to minimize stray inductance, to utilize a Kelvin source for gate driving, to provide sufficient cooling area to minimize heat flux (4.2 in2 per two device phase-leg module, or equivalent), to provide sufficient electrical isolation from the cooling surface to any metal oxide semiconductor field effect transistor (MOSFET) terminal, to include an embedded thermal sensor, and to possess a short circuit withstand capability of at least 3 μs. Modules with a voltage rating of 1.7 or 3.3 kV will be considered and can take exception to most of the requirements with justified replacement requirements. Altitude and shock/vibration requirements are mandatory.

Expected TRL or TRL Range at completion of the Project: 2 to 6

Primary Technology Taxonomy:

  • Level 1 01 Propulsion Systems
  • Level 2 01.3 Aero Propulsion

Desired Deliverables of Phase I and Phase II:

  • Research
  • Analysis
  • Prototype
  • Hardware
  • Software

Desired Deliverables Description:

Deliverables vary considerably within the subtopic, but ideally proposals would identify a technology pull area (with a market size estimate) and how the proposed idea addresses the needs of the technology pull area and would then deliver a combination of analysis and prototypes that substantiate the idea's merit. For Phase I, it is desirable that the proposed innovation clearly demonstrates that it is commercially feasible and addresses NASA's needs. Phase II deliverables should be focused on the maturation, development, and demonstration of the proposed technical innovation.

State of the Art and Critical Gaps:

The critical technical need is for lightweight, high-efficiency motors, distribution systems, and fault management. Typically, the weight needs to be reduced by a factor of 2 to 3 and efficiency needs to be improved. Higher efficiency reduces losses and makes thermal management more achievable in an aircraft. 

Technologies that address these gaps enable EAP, which enables new aircraft configurations and capabilities for the point-to-point on-demand mobility market and a new type of innovation for transport aircraft to reduce fuel consumption and emissions.

Relevance / Science Traceability:

EAP is an area of strong and growing interest in the Aeronautics Research Mission Directorate (ARMD). There are emerging-vehicle-level efforts in urban on-demand mobility, the X-57 electric airplane being built to demonstrate EAP advances applicable to thin and short haul aircraft markets, and an ongoing technology development subproject to enable EAP for single-aisle aircraft. Additionally, NASA started the Electrified Powertrain Flight Demonstration (EPFD) project to enable a megawatt-class aircraft.

Key outcomes NASA intends to achieve in this area are:

  • Outcome for 2015 to 2025: Markets will begin to open for electrified small aircraft.
  • Outcome for 2025 to 2035: Certified small-aircraft fleets enabled by EAP will provide new mobility options. The decade may also see initial application of EAP on large aircraft.
  • Outcome for >2035: The prevalence of small-aircraft fleets with electrified propulsion will provide improved economics, performance, safety, and environmental impact, while growth in fleet operations of large aircraft with cleaner, more efficient alternative propulsion systems will substantially contribute to carbon reduction.

Projects working in the vehicle aspects of EAP include:

  • Advanced Air Vehicles Program (AAVP)/Advanced Air Transport Technology (AATT) Project
  • Integrated Aviation Systems Program (IASP)/Flight Demonstrations and Capabilities (FDC) Project
  • AAVP/Revolutionary Vertical Lift Technology (RVLT) Project
  • Transformative Aeronautics Concepts Program (TACP)/Convergent Aeronautics Solutions (CAS) Project
  • TACP/Transformational Tools and Technologies (TTT) Project

 

References:

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