By Bjorn Fehrm
December 11, 2020, ©. Leeham News: We use this Corner to define the time table for our hydrogen airliner program and for what areas we need to conduct risk-reducing research before we embark on an actual design.
As we said in last week’s Corner, we aim to develop a hydrogen airliner for the heart of the domestic market after the COVID-19 Pandemic. It’s a 160 to 180 seat single-aisle turbofan driven airliner, using liquid hydrogen as the fuel.
Figure 1. Airbus ZEROe hydrogen-fueled airliner concepts. Source: Airbus.
A 160 to 180 seat hydrogen airliner
We know from the last Corner, our aircraft will use a classical tube with wings and a classical empennage. The engines will be turbofans, one on each wing. They will be hydrogen-fueled using an evolutionary development of the engines used today on the Airbus A320neo and Boeing 737 MAX.
Entry into service of the aircraft is targeted for 2035, the timetable of the Airbus hydrogen airliner. We spend the time until a program launch decision must be made by 2027 to do risk-reducing research for the most challenging areas of the project.
Areas covered in our risk-reducing research programs
There are several areas where we need to increase our knowledge before embarking on a design of a hydrogen airliner:
- The highest priority is liquid hydrogen tank designs. The LH2 tank is the most challenging area for a hydrogen airliner. It needs ultra-efficient isolation for the -253°C cryogenic storage of LH2. Shall we make it as a vacuum flask design with additional polyurethane isolation (in case of a flask puncture) or a one-wall design with thicker polyurethane isolation?
- Do we design with one big tank placed at the rear or two smaller tanks, preferably placed on both sides of the center of gravity? What are the effects on the cabin?
- We need research on hydrogen fuel and leak detection components. Although the space launcher industry has developed suitable components, these need adaptations for longer-term use in an airliner environment.
- We shall start an engine hydrogen conversion program together with an engine OEM. The risk reduction phase can use an existing engine from the A320neo/737 MAX that is converted to hydrogen. The work will center around combustor design and the heat exchanger we need to turn the liquid hydrogen to gas before entering the engine.
- We shall hook up with a fuel cell manufacturer to develop a 1MW fuel cell to replace the APU function. It shall allow operation on the ground and during flight so we can use a more electrical aircraft architecture.
- We start a ground operation program together with airport authorities that defines storage, liquefaction, and tanking facilities. Technology from the launcher industry is essential for the program. Practical tanking trails with dummy aircraft shall finish the program where different safety scenarios are simulated.
- Together with our regulator, we shall start a safety program, where different safety scenarios are defined and simulated. From these, we shall research how the worst scenarios can be handled and mitigated. An example of a follow-on program is how to evacuate passengers during a hydrogen leak with both freeze and heat damage risks. We also need to understand how to fight such events. What equipment and methods are required. Must the airport fire brigades have different fire engines? Must aircraft safety rules be changed?
In the next Corners, we go through these areas and discuss the challenges, research activities and possible solutions.