Net-Zero Aircraft Design Optimisation

Although aircraft fuel efficiency improved by around 50% over the past three decades, rising demand for air travel led to a 34% increase in CO2 emissions just over the past five years. Hydrogen fuel cell aircraft offer the opportunity for truly net-zero flight over much longer distances than battery-electric aircraft. They are particularly suited for the European aviation market, which has an average range of 983 km, but is currently dominated by the Airbus A320 and Boeing 737 with design ranges above 4000 km.
The fallacy of prior hydrogen aircraft concepts was that they followed established kerosene aircraft design practices, as summarised in the works of Torenbeek, Roskam, and Raymer. As a result, existing airframes were reused, current mission trajectories were considered, novel aerodynamic technologies were retrofitted, and wrong design objectives were applied. Hence, there is a need for a physics-based, multi-level sizing method giving an unprejudiced view of the design space.
This will allow the following three questions to be answered: Which are the fundamental design parameters governing the optimum size of a fuel cell? How should current aircraft operating practices be modified to play to fuel cells' strengths? Could a synergistic propulsion airframe integration close the weight and drag gap between hydrogen and kerosene aircraft?
The preliminary work conducted during the MRes phase of the CDT demonstrated the power of a whole-system approach, where the impact of design decisions taken at aircraft level could be tracked down to powertrain component level and vice versa. The purpose of the first year of the PhD is to further the understanding of the physical nature of the FC aircraft sizing problem. An important interim goal of this project is to identify the non-dimensional groups governing the FC aircraft design space; this is important insofar as the conclusions drawn by current studies heavily depend on the assumed technology levels, with the risk of imposing false constraints on the multi-dimensional design space. The remainder of the PhD will likely be built on three pillars: higher-fidelity modelling, experimental design, and collaboration with other institutions, however, a detailed plan is yet to be developed.

In summary, this project aims to strike a balance between realism and minimum climate impact, starting with a clean slate, yet keeping to the laws of physics, in order to realise short- to medium-haul net-zero air travel; not by 2050, but by 2035 as HRH The Prince of Wales challenged the global aviation community in 2020.