The declared goal of the European Union is to reduce all CO2 emissions from aviation by 2050. In addition, Non-CO2 effects must also be better understood and reduced. These Non-CO2 effects include nitric oxide and water vapor effects and the effects of contrails and aircraft induced cloudiness on the atmosphere. They influence the radiation budget of the atmosphere and contribute 2/3 to the climate impact from air traffic today. New types of aircraft engines such as direct hydrogen combustion, also offer the possibility of reducing these climate effects but there are no measurements available at present.
Hydrogen powered aircraft are now within reach and thus a new research topic evolved that is occupying science and industry alike in designing a sustainable future air traffic. When using hydrogen from renewable energy sources this technology promises the complete avoidance of CO2 emissions. But what about contrails, water vapor and nitrogen oxide emissions?
While nitrogen oxide and water vapor emissions and their effect on the atmosphere have been investigated before, little is known about the properties and climate impact of contrails from hydrogen-powered aircraft. Although the exhaust gas is particle-free, the additional water vapor generated in the engine could lead to the formation of contrails even at lower altitudes.
In order to measure the emissions and the properties of contrails from hydrogen engines for the first time, the Institute of Atmospheric Physics joined the innovative demonstrator project Blue Condor designed by AIRBUS Up Next, a subsidiary of AIRBUS: A glider equipped with a small jet engine is modified by Up Next and The Perlan Project to run on hydrogen. The glider is towed to an altitude of about 9 km with a Grob Egrett from AV Experts, LLC in regions where contrails can form. There the engine is powered and the contrail is measured with the instruments of the Institute for Atmospheric Physics, which are integrated on the Egrett. On board are precise and tested instruments for water vapour, ice particles, aerosols, nitrogen oxides and CO2, and some which were specially designed for the Blue Condor mission. A second glider, which is operated with conventional kerosene, will be measured in a similar air mass in order to characterize both propulsion systems in a comparable atmosphere.
Model studies show that the contrails from hydrogen propulsion could have fewer but larger ice crystals than with conventional propulsion systems because of the increased water vapor emission. Since these larger particles “rain out” more quickly from the atmosphere, the lifetime of the contrails is shorter and the effect on the climate system is therefore reduced.
The flight program is scheduled to take place in April 2023 in the United States. First test flights with the kerosene-powered glider were successfully carried out in Texas in April 2022 by a team of 6 DLR scientists. The study is led and supported by measurements and model simulations of the H2CONTRAIL research group.