Baseline Report - Multi-Disciplinary Design and Optimisation of a Long-Range eVTOL Aircraft

Baseline Report of the Design, Synthesis and Exercise (DSE) carried on during the Spring DSE 2021, group 06, assignment "Multi-Disciplinary Design and Optimisation of a Long-Range eVTOL Aircraft". Tutor: Saullo Giovani Pereira Castro Coaches: Davide Biagini and Ali Nokhbatolfoghahai Institution: Delft University of Technology Place: Faculty of Aerospace Engineering, Delft Submission Date: Thursday 6th May, 2021 Executive summary Around the world, many cities suffer from increasing traffic and congestion problems. Vertical takeoff and landing aircraft are a promising technology to alleviate this problem. Due to their ability to overfly obstacles, move independently of ground infrastructure and take off from anywhere, they could allow for very fast door-to-door transport. It is the aim of this DSE project to explore this market opportunity and design a VTOL aircraft that can carry four passengers over 300 km. Due to the growing relevance of sustainability in transport, the design space will be constrained to electric VTOLs (eVTOL). The mission need statement of the project is as follows: Provide sustainable, personal aerial transportation for intercity travel that is competitive with the current transportation methods while requiring minimal infrastructure. In the report at hand, several aspects of this mission are investigated in detail and the information is used to generate technical requirements. Finally, possible designs for the mission are identified and selected for further analysis. Chapter 2 outlines the functional analysis of all stages of the project. This is a crucial step in the design, since analysing the functions required by the design process and eVTOL provide a clear picture of the use case. On a high level, the functions were investigated in five phases: mission introduction, aircraft design, production and delivery of the aircraft, operation of the aircraft, and disposal of the aircraft. Aircraft operation is of the greatest interest to the customer, which is why it is analysed in greater detail than the others: the steps taken in preflight actions, take-off, cruise, extending the mission, landing and post-flight actions are broken down to up to four levels to capture detail. The result can be seen in the functional flow block diagram and functional breakdown structure. In Chapter 3, the market opportunities for a long-range eVTOL are explored. Among the possible target industries, the commercial transport and private sector were deemed the most promising. With its range of 300 km, the eVTOL could satisfy the needs of intracity travel, but most importantly be used for intercity travel as well. In Europe, 300 km is a typical distance to be covered by commuters and tourists in business and personal trips. It is in this market segment where a long-range eVTOL could hope to gain a lot of traction. Furthermore, it could be a comfortable personal mode of transport for higher income populations. Europe and the United States provide good conditions for this. Europe in particular is suitable since it has many major cities at small distances from each other. Based on previous studies, it was concluded that a market size of 15 billion US dollars could be achieved by 2040 for eVTOLs in the chosen market segment. This corresponds to annual sales of about 5000 units. The team could aim to partake in this with 205 eVTOL vehicles sold per year, priced at 1.53 million apiece. The direct competitors would be helicopters and other eVTOL projects. To inform the sustainable planning of the project, Chapter 4 lays out a literature review on the environmental and social sustainability of eVTOLs. It is found that eVTOLs produce less greenhouse gas emissions than conventional internal combustion engine cars for distances longer than 50 km. Larger distances allow the eVTOL to take advantage of the aerodynamically optimised cruise configuration. However, the sustainability of eVTOLs may be limited by their energy source. Especially Lithium-Ion batteries cause high environmental impact in production and are created from scarce natural resources often obtained from mines with questionable humanitarian standards. Therefore, alternative batteries or hydrogen fuel cells should be considered as alternatives. Management of the technical risk was done in Chapter 5. Technical risks include risks associated with technical failures of the aircraft, but also errors made during the design. First the main technical risks were identified, and given a score based on the severity of the risk. In total 22 risks were identified. Using these scores the most severe risks were selected, a total of 9 risks were deemed necessary to manage. These were managed by either reducing the probability of occurrence or the consequence associated with that risk. For most risks this was done by requiring minor design features to be added to the concepts. In Chapter 6 technical budgets were allocated to the different systems of the aircraft. This can help in the design of the different systems, as the designers have an idea as to how much resources they can use for their system. Budgets were made for weight, cost, thrust, drag and power. Apart from allocating budgets, also the resource contingencies were determined for each design stage. These contingencies represent a margin to the maximum change in budget size for each subsystem. If the contingency is exceed, either a redesign or a change of the initial budget size should be considered. As can be expected, the contingency margins reduce when the design progresses, as the level of detail increases, and with it the uncertainty in resource usage. The requirement discovery (documented in Chapter 7) was initiated with the identification of the stakeholders of the project, as well as their needs. The stakeholders identified for the project were the customer, regulatory bodies, citizens, passengers and the pilot. Their needs were compiled into requirements, that were then further used to create system and subsystem requirements. The subsystems investigated were the propulsion, power, control, structure, cabin, and lifting subsystems. From this, 8 key stakeholder requirements and 14 driving requirements were distilled to guide the design. Finally, Chapter 8 used a design option tree to identify three relevant options for further investigation