Developed by 100 British engineers under the FlyZero project banner, the project is part of the UK government and industry backed Aerospace Technology Institute which will invest a hefty £3.9 billion in research between now and 2026. The aim is to examine all promising paths to zero-carbon intercontinental aviation, and propose solutions that can be put into service by the end of the decade.
The new concept showcases the potential for green liquid hydrogen to be used as a lightweight aviation fuel, with the ATI claiming it uses no CO2 when burned and could offer three times the energy of the kerosene fuel currently used per kilogramme.
The team examined the pros and cons of batteries, gaseous hydrogen, ammonia, liquid hydrogen as a combustion fuel and liquid hydrogen used in fuel cells. Batteries were off the table pretty much immediately, being too heavy and bulky for the job. Ammonia was dropped due to excessive harmful NOx emissions.
Notably, liquid hydrogen offers 60 times the energy of a battery per kilogramme, showcasing why pure battery electric technology isn’t suitable for aircraft.
Using liquid Hydrogen, the ATI FlyZero team put together a concept mid-size airliner with a 54 meter wingspan that it says can fly at the same speeds as today’s airliners, carrying up to 279 passengers and delivering range figures up to 5,250 nautical miles (6,040 miles, 9,723 km) in a single hop. This allows the proposed aircraft to service cities such as San Francisco, Delhi and Beijing within non-stop reach from London.
The liquid hydrogen is stored in cryogenic fuel tanks housed in the rear fuselage (with two smaller tanks in the forward fuselage to keep the aircraft balanced) at around minus 250 degrees Celsius. The fuel powers two turbofan engines through hydrogen combustion.
The ATI says that the necessary new infrastructure for the fuel could be concentrated at a few international airports.
The cryogenic fuel tanks in the aft fuselage with a pair of smaller ‘cheek’ tanks that expand the lower forward fuselage and give the plane its signature look of a ‘squirrel with its cheeks stuffed full of nuts’ look.
While showcasing the concept, the ATI has acknowledged that major challenges remain before hydrogen-powered flight is possible. Producing green hydrogen is currently expensive, although this is likely to fall as demand grows. ATI reckons it could be cheaper to operate hydrogen powered aircraft than conventional aircraft by the mid-2030’s.
One other challenge will be ensuring that any green liquid hydrogen is produced in an environmentally friendly manner, and not through energy created by burning fossil fuels.
There is still some technological and logistic mountains to climb, but not limited to:
- The storage and distribution of a cryogenic fuel onboard an aircraft,
- Developing sustainable technologies for stable and reliable hydrogen combustion in gas turbines.
- Efficient energy conversion and thermal management of hydrogen fuel cells and hybrids.
- Minimizing the generation of other climate impacts i.e., NOx and contrails.
- Minimizing the impact on aircraft structural mass and drag.
- Developing a sustainable hydrogen fuel production infrastructure.”
The FlyZero project has pledged to publish a detailed report for early 2022, including three final aircraft concepts for regional, narrow-body and mid-size airliners, technology roadmaps, economic and marketing reports and sustainability assessments.