Design of a Hydrogen Aircraft for Zero Persistent Contrails

Abstract

Contrails are responsible for a significant proportion of aviation’s climate impact. This paper uses data from the European Centre for Medium-Range Weather Forecasts to identify the altitudes and latitudes where formed contrails will not persist. This reveals that long-lived contrails may be prevented by flying lower in equatorial regions and higher in non-equatorial regions. Subsequently, it is found that the lighter fuel and reduced seating capacity of hydrogen-powered aircraft lead to a reduced aircraft weight, which increases the optimal operating altitude by about 2 km. In non-equatorial regions, this would lift the aircraft’s cruise point into the region where long-lived contrails do not persist, unlocking hydrogen-powered, low-contrails operation. The baseline aircraft considered is an A320 retrofitted with in-fuselage hydrogen tanks. The impacts of the higher-altitude cruise on fuel burn and the benefits unlocked by optimizing the wing geometry for this altitude are estimated using a drag model based on theory proposed by Cavcar, Lock, and Mason, and verified against existing aircraft. The weight penalty associated with optimizing wing geometry for this altitude is estimated using Torenbeek’s correlation. It is found that thinner wings with higher aspect ratios are particularly suited to this high-altitude operation and are enabled by the relaxation of the requirement to store fuel in the wings. An example aircraft design for the non-equatorial region is provided, which cruises at a 14 km altitude at Mach 0.75 with a less than 1% average probability of generating long-lived contrails when operating at latitudes more than 35° from the equator. Compared to the A320, this concept design is estimated to have a 20% greater cruise lift–drag ratio, due to the 33% thinner wings with a 50% larger aspect ratio, enabling just 5% more energy use per passenger-km, despite fitting 40% fewer seats.

Preliminary Performance Analysis of Medium-Range Liquid Hydrogen-Powered Box-Wing Aircraft

“…In Ref. [40], the integration of a fuselage tank in a short-to-medium range aircraft with the same fuselage as the Airbus A320 leads to a reduction in the number of passengers (about 40%) and harmonic range (about 30%) compared to the kerosene version. To counteract the penalty in aircraft operating performance, some authors have lengthened the reference fuselage to accommodate the same number of passengers as the kerosene aircraft.…”

“…In Ref. [40], the design of a short-medium-range hydrogen aircraft, whose fuselage is the same as that of an Airbus A320, is discussed. Ref.…”

Hydrogen-Powered Aircraft at Airports: A Review of the Infrastructure Requirements and Planning Challenges

“…While much recent research focuses on aircraft technologies [9,[33][34][35][36], the requirements to enable alternative-powered flights from an airport planning perspective are not often analyzed. As early as 1976, the National Aeronautics and Space Administration (NASA) sponsored two case studies on the requirement to enable hydrogen-powered flight at San Francisco International Airport and Chicago O'Hare International Airport in the United States.…”