Electrification of the propulsion system has opened the door to a new paradigm of propulsion system configurations and novel aircraft designs, which was never envisioned before. Despite lofty promises, the concept must overcome the design and sizing challenges to make it realizable. A suitable modeling framework is desired in order to explore the design space at the conceptual level. A greater investment in enabling technologies, and infrastructural developments, is expected to facilitate its successful application in the market. In this review paper, several scholarly articles were surveyed to get an insight into the current landscape of research endeavors and the formulated derivations related to electric aircraft developments. The barriers and the needed future technological development paths are discussed. The paper also includes detailed assessments of the implications and other needs pertaining to future technology, regulation, certification, and infrastructure developments, in order to make the next generation electric aircraft operation commercially worthy.

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A review of concepts, benefits, and challenges for future electrical propulsion-based aircraft

https://iopscience.iop.org/article/10.1088/1361-6668/ab695a/pdf

Concept design of a high power superconducting generator for future hybrid-electric aircraft

Bulk (RE)-Ba-Cu-O [(RE)BCO] cuprate HTS have been developed steadily towards a wide range of sustainable engineering and technological applications since their discovery in 1986 based primarily on their unique potential to trap very large magnetic fields (>5 T) at temperatures that are accessible potentially by thermo-electric cooling techniques. Trapped fields of ∼10 T at the surface of individual (RE)BCO bulk single grains and in excess of 17 T in a reinforced two-sample stack are now being achieved reliably. This paper reviews the current state of the art of the processing of large, single grain (RE)BCO bulk superconductors required to trap fields of this magnitude, and specifically via two advanced fabrication approaches; the traditional TSMG process and the more recently developed TSIG technique. The focus of the review is on optimising the critical processing parameters to achieve high-quality, high performance single grain (RE)BCO bulk superconductors specifically for high-field applications. The review also summarises recent advances in processing, such as the integration of the so-called buffer technique into the TSMG and TSIG processing methodologies to achieve improved reliability in single grain growth with a success rate exceeding 90%, the development of a Mg-doped NdBCO generic seed crystal for the successful growth of all rare-earth and light-rare earth based bulk superconductors [(RE)BCO and (LRE)BCO] and the introduction of nano-size stable, non-superconducting phase(s) to the bulk microstructure to improve the intrinsic flux pinning strength of the material, and hence trapped magnetic field. Details of the two-step buffer-aided TSIG technique developed recently that yields dense, near-net shaped, high performance (RE)BCO bulk superconductors with improved superconducting and mechanical properties are also presented. Suitable sample-seed configurations for effective multi-seeding are discussed, which enables the production of high aspect ratio, bar-shaped (RE)BCO quasi-single grains that exhibit improved levitation forces required in Maglev-based applications, for example, are discussed. The electrical, mechanical, microstructural and magnetic properties (including those achieved from a pulsed-field magnetisation approach) of the different (RE)BCO systems are presented and the relevant correlation in properties and performance highlighted, accordingly. Finally, a brief summary of existing applications and prospects for near-future exploitation of these remarkable, technologically important materials, and particularly in the medical and pharma-industries, is provided.

https://iopscience.iop.org/article/10.1088/1361-6668/abde88/pdf

The processing and properties of bulk (re)bco high temperature superconductors: current status and future perspectives

https://iopscience.iop.org/article/10.1088/1361-6668/ab9ace/pdf

Dynamic loss and magnetization loss of HTS coated conductors, stacks, and coils for high-speed synchronous machines

Aerodynamic interaction between propellers of a distributed-propulsion system in forward flight

The authors wish to express their sincere thanks to Dr Nicky Athanassopoulou, Ms Andi Jones and Dr Rob Phaal of Institute for Manufacturing Education and Consultancy Service Ltd for their excellent work in organising and facilitating the Road-Mapping exercise upon which this current work is based. The authors would also like to express their appreciation of the contribution made by the other participants at the workshop: Hari Babu Nadendla (Brunel University), Pavol Diko (Slovak Academy of Sciences), Tomas Hlasek (CAN Superconductors), John Hull (The Boeing Company), Lars Kuhn (evico), Mathias Noe (KIT), Jan Plechacek (CAN Superconductors), Yunhua Shi (University of Cambridge) and Frank Werfel (ATZ). The authors acknowledge financial support for the Road-Mapping exercise on which this work is based from the University of Cambridge EPSRC Impact Acceleration Account (EP/K503757/1).

https://iopscience.iop.org/article/10.1088/1361-6668/aad7ce/pdf

Bulk superconductors: a roadmap to applications

This work was supported by the Siemens Company and by the Engineering and Physical Sciences Research Council (grant number: EP/P00962X/1). Mark Ainslie would like to acknowledge financial support from an Engineering and Physical Sciences Research Council (EPSRC) Early Career Fellowship EP/P020313/1.

https://iopscience.iop.org/article/10.1088/1361-6668/aad786/pdf

Exploiting flux jumps for pulsed field magnetisation

Electric propulsion systems are considered as one possibility to reach the ambitious goals of the European Union’s Flightpath 2050 with regards to greenhouse gas emissions and noise. It has been claimed in several publications that Distributed Electric Propulsion (DEP) offers significant improvement in aerodynamic efficiency and thus a reduction in structural weight of the wing and noise emissions as well as additional degrees of freedom concerning flight control. To not outweigh those advantages by heavier drivetrains, the components within the electric propulsion system have to be extremely lightweight, efficient and reliable at the same time. The German nationally funded project SynergIE evaluates DEP for a 70 PAX regional reference aircaft with two (SE-2), six (DEP-6) and twelve (DEP-12) propulsion units with a turbo-electric drivetrain layout. This study aims to quantify the effect on the specific block fuel consumption for the different numbers of propulsors based on Top Level Aircraft Requirements (TLARs). The approach contains a coupled electric drivetrain system model which is based on physically derived, analytical models for each component linking specific subdomains, e.g., electromagnetics, structural mechanics and thermal analysis. A genetic algorithm is applied to optimise the key performance indicators (KPIs) of the electric system, before the results are fed back to the aircraft sizing process. It has been identified that constraints such as installation space or architectural decisions such as the number of propulsors have significant influence on the drivetrain weight and efficiency and interact with the whole aircraft sizing process, esp. with reference to nacelle weight and drag and thus the block fuel consumption. The study shows that the DEP-6 and DEP-12 project aircraft both have a potential of reducing the specific block fuel consumption by approx. 4.2 % and 5.8 % respectively in case of direct driven propellers, while for a geared-drive scenario a total reduction of up to 7.6 % in case of DEP-6 and 8.5 % in case of DEP-12 is possible, all compared to the direct-driven baseline (BSL) aircraft SE-2.

Design Space Exploration Study and Optimization of a Distributed Turbo-Electric Propulsion System for a Regional Passenger Aircraft

According to Flightpath 2050, the aviation industry is aiming to substantially reduce emissions over the coming decades. One possible solution to meet these ambitious goals is by moving to hybrid-electric drivetrain architectures which require the electric components to be extremely lightweight and efficient at the same time. It has been claimed in several publications that cryogenic and in particular superconducting components can help to fulfill such requirements that potentially cannot be achieved with non-cryogenic components. The purpose of this work was to make a fair comparison between a cryogenic turbo-electric propulsion system (CEPS) and a non-cryogenic turbo-electric propulsion system (TEPS) on a quantitative level. The results on the CEPS were presented in detail in a previous publication. The focus of this publication is to present the study on the TEPS, which in conclusion allows a direct comparison. For both systems the same top-level aircraft requirements were used that were derived within the project TELOS based on an exemplary mission profile and the physical measures of a 220-passenger aircraft. Our study concludes that a CEPS could be 10% to 40% lighter than a TEPS. Furthermore, a CEPS could have a total efficiency gain of up to 18% compared to a similar TEPS.

Comparative Analysis and Optimization of Technical and Weight Parameters of Turbo-Electric Propulsion Systems

In order to determine the spatial distribution of the flexural strength, three-point bend tests have been performed on bar specimens cut from four YBa2Cu3O7− δ single-grain bulk superconductors. A relatively large spread of the room temperature flexural strength, average and standard deviation of 49.3 MPa and 12.7 MPa, respectively, was observed across the four bulk samples. This is attributed to the systemic microstructural variation introduced by the seeded melt growth. In particular, the strength was shown to be related to the local porosity and Y2BaCuO5 content. To further examine bulk-to-bulk variability, indirect tensile (Brazilian) tests were conducted on twelve 16-mm-diameter bulk superconductors from three production batches. The Weibull modulus for these was calculated to be 8.76, suggesting that, despite the large spread in strength with position within a bulk, the batch processing of bulk superconductors can consistently yield samples with comparable overall mechanical strengths.

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Mykhaylo Filipenko

Papers

Bulk superconductors: a roadmap to applications

Exploiting flux jumps for pulsed field magnetisation

Design Space Exploration Study and Optimization of a Distributed Turbo-Electric Propulsion System for a Regional Passenger Aircraft

Comparative Analysis and Optimization of Technical and Weight Parameters of Turbo-Electric Propulsion Systems

Spatial Distribution of Flexural Strength in Y–Ba–Cu–O Bulk Superconductors