A Vehicle Design and Optimization Model for On-Demand Aviation

Abstract

On-demand aviation refers to an envisaged air taxi service, using small, autonomous, vertical-takeoff-and-landing, battery-powered electric aircraft. A conceptual design and optimization tool for on-demand aviation is presented in this thesis. The tool uses Geometric Programming, a class of optimization problems with extremely fast solve times and for which global optimality is guaranteed. The optimization model consists of a vehicle, a sizing mission, a revenue-generating mission, and a deadhead (non-passenger-carrying) mission. Cost per trip, including the additional cost due to the deadhead mission, is used as the objective function. Vehicle noise is computed during post-processing using a semi-empirical method. The tool is used to conduct a study of on-demand aviation from a vehicle design perspective.A trade study is conducted between several different on-demand aircraft configurations. Four configurations are viable: the lift + cruise configuration, the compound helicopter, the tilt wing, and the tilt rotor. Configurations with a higher lift-to-drag ratio, but a higher disk loading, generally weigh less and cost less to operate; configurations with a lower lift-to-drag ratio, but a lower disk loading, are quieter. Using New York City as an example market, it is shown that an on-demand air service will cost significantly less as compared to current helicopter air taxi operations. The two most important costs are pilot salary and battery amortization. If these two costs can be reduced (via vehicle automation and reduced battery manufacturing costs respectively), an on-demand air service becomes competitive with current car ridesharing on the basis of cost per seat mile. Therefore, on-demand aviation has the potential to become a system for everyday commutes.Technological assumptions and vehicle requirements, especially mission range, battery energy density, vehicle autonomy level, battery manufacturing cost, and reserve requirements, have significant impacts on vehicle weight and cost. Vehicle noise can be reduced through the careful selection of key design parameters. However, envisaged noise requirements cannot easily be met, even with the most generous long-termThe author wishes to thank all those who contributed their insights to this work. In particular,

Model Development for a Comparison of VTOL and STOL Electric Aircraft Using Geometric Programming

“…This approach, described in more detail by [12], has been shown to be very powerful for large conceptual design space explorations due to it's fast solution times (on the order of a few seconds) and robust optimization capability. Geometric programming has been used to model both electric STOL [3] and VTOL [9] aircraft.…”

“…As a consequence, this approach lends itself well to modular subsystem model development; the constraints describing the performance of a motor are the same whether that motor is powering a VTOL lift fan or a STOL blowing motor. The majority of the models can be reused for both configurations, and there are well-developed methods for modeling most major subsystems as GPs, such as those described in [9] for various VTOL configurations.…”

“…Preliminary results derived from both STOL and VTOL models will be discussed. As part of this paper, existing literature on STOL aircraft [3][5] [7] [8], VTOL aircraft [9][10] [11], and vehicle design optimization [12] is considered.…”

Safety Considerations in Emerging Electric Aircraft Architectures

“…Due to the likely use of fixed pitch propellers, low rotor inertia, and the lack of mechanical control linkages these vehicles are not capable of autorotation. The primary benefits of multirotor configurations are low cost due to mechanical simplicity and possible noise benefits relative to helicopters due to additional design freedom to vary disk loading, blade frequency, and tip speed [20].…”

Configuration Study of Electric Helicopters for Urban Air Mobility

“…Brown and Harris [6] applied similar assumptions and expanded on this work by including noise and cost considerations, but considered only one mission profile. This study showed potential noise and efficiency advantages for a compound helicopter configuration over tiltrotor, tiltwing, and lift-and-cruise configurations for UAM applications.…”