Climate change is a pressing issue. Hydrogen aircraft are an excellent alternative to current kerosene aircraft, and appear to be the most viable long-term solution for net-zero flight. One of the main challenges for hydrogen aircraft is to sustain a low boil-off rate. This research explores the solution of active cooling of the LH2 mixture in the fuel tank. It focusses on the construction of a thermodynamic model for cryogenic liquid hydrogen fuel storage in aircraft, a system model for single-stage Reverse Turbo-Brayton Cryocoolers (RTBC), and the conceptual design of the RTBC’s miniature high-speed compressor. This is used for the integrated modelling of the RTBC, compressor and LH2 fuel tank for an exploration study of the carbon neutral hydrogen concept of the long-range Flying-V aircraft. Results show that the RTBC might offer a valuable addition to the Flying-V design space for boil-off control in addition to careful design of the insulation and tank shape.

Sustainability has become an increasingly important issue, and several different governments around the world have been working towards more environmentally friendly approaches throughout different industries. This has led to measures such as the European Green Deal, which aims to make Europe climate neutral by 2050. For the aircraft industry, however, this goal creates a so-called circular causality problem. This is because there may be limited investment in increasing production of alternative energy sources due to the limited availability of aircraft that use them. On the other hand airlines may hesitate due to the limited availability of fuel to buy such aircraft. In order to solve this problem, the carbon neutral ready aircraft has been proposed. The carbon neutral ready aircraft is designed such that it initially is powered by fossil fuels and can then be converted to be powered by a carbon neutral energy source. The carbon neutral energy source that is chosen for this aircraft design is synthetic kerosene. The carbon neutral aircraft has a high wing configuration with a high aspect ratio wing. To cope with the large span of the aircraft it was decided to give the aircraft the ability of the wing tips to be folded up. Furthermore, the wing has support struts which connect the wing to the lower part of the fuselage. The propulsion system of the aircraft has two novel features: two wing mounted ultra high bypass ratio turbofan engines and an electrically powered ducted fan, which ingests the boundary layer at the aft of the fuselage. An additional five-gear configuration was chosen for the landing gear to provide the aircraft with stable ground operations while not creating a need for a fairing which interferes with the boundary layer being ingested by the aft ducted fan. Carrying out the design of this aircraft shows that the aircraft is financially feasible and performs as well as the baseline A320 aircraft in terms of payload and range, while allowing sustainability goals such as the European Grean Deal to be met. The aircraft has a 17 % emission reduction compared to the A320neo, while still employing fossil fuel based kerosene. Furthermore, at least 90% by mass of the primary structure of the aircraft is recyclable. From the recommendations however, it is clear that a lot still needs to be done before the carbon neutral aircraft can enter into service in 2030.