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The climate impact of hydrogen-powered hypersonic transport

Pletzer, Johannes and Hauglustaine, Didier and Cohen, Yann and Jöckel, Patrick and Grewe, Volker (2022) The climate impact of hydrogen-powered hypersonic transport. Atmospheric Chemistry and Physics (ACP), 22 (21), pp. 14323-14354. Copernicus Publications. doi: 10.5194/acp-22-14323-2022. ISSN 1680-7316.

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Official URL: https://acp.copernicus.org/articles/22/14323/2022/

Abstract

Hypersonic aircraft flying at Mach 5 to 8 are a means for traveling very long distances in extremely short times and are even significantly faster than supersonic transport (Mach 1.5 to 2.5). Fueled with liquid hydrogen (LH2), their emissions consist of water vapor (H2O), nitrogen oxides (NOx), and unburned hydrogen. If LH2 is produced in a climate- and carbon-neutral manner, carbon dioxide does not have to be included when calculating the climate footprint. H2O that is emitted near the surface has a very short residence time (hours) and thereby no considerable climate impact. Super- and hypersonic aviation emit at very high altitudes (15 to 35 km), and H2O residence times increase with altitude from months to several years, with large latitudinal variations. Therefore, emitted H2O has a substantial impact on climate via high altitude H2O changes. Since the (photo-)chemical lifetime of H2O largely decreases at altitudes above 30 km via the reaction with O(1D) and via photolysis, the question is whether the H2O climate impact from hypersonics flying above 30 km becomes smaller with higher cruise altitude. Here, we use two state-of-the-art chemistry–climate models and a climate response model to investigate atmospheric changes and respective climate impacts as a result of two potential hypersonic fleets flying at 26 and 35 km, respectively. We show, for the first time, that the (photo-)chemical H2O depletion of H2O emissions at these altitudes is overcompensated by a recombination of hydroxyl radicals to H2O and an enhanced methane and nitric acid depletion. These processes lead to an increase in H2O concentrations compared to a case with no emissions from hypersonic aircraft. This results in a steady increase with altitude of the H2O perturbation lifetime of up to 4.4±0.2 years at 35 km. We find a 18.2±2.8 and 36.9±3.4 mW m−2 increase in stratosphere-adjusted radiative forcing due to the two hypersonic fleets flying at 26 and 35 km, respectively. On average, ozone changes contribute 8 %–22 %, and water vapor changes contribute 78 %–92 % to the warming. Our calculations show that the climate impact, i.e., mean surface temperature change derived from the stratosphere-adjusted radiative forcing, of hypersonic transport is estimated to be roughly 8–20 times larger than a subsonic reference aircraft with the same transport volume (revenue passenger kilometers) and that the main contribution stems from H2O.

Item URL in elib:https://elib.dlr.de/189816/
Document Type:Article
Title:The climate impact of hydrogen-powered hypersonic transport
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Pletzer, JohannesDLR, IPAUNSPECIFIED
Hauglustaine, DidierCEA-CNRS, Gif-sur-Yvette, FUNSPECIFIED
Cohen, YannCEA-CNRS, Gif-sur-Yvette, FUNSPECIFIED
Jöckel, PatrickDLR, IPAhttps://orcid.org/0000-0002-8964-1394
Grewe, VolkerDLR, IPAhttps://orcid.org/0000-0002-8012-6783
Date:8 November 2022
Journal or Publication Title:Atmospheric Chemistry and Physics (ACP)
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:22
DOI:10.5194/acp-22-14323-2022
Page Range:pp. 14323-14354
Publisher:Copernicus Publications
ISSN:1680-7316
Status:Published
Keywords:Climate Impact of hypersonic transport ozone layer aviation NOx aviation H2O
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Air Transportation and Impact
DLR - Research area:Aeronautics
DLR - Program:L AI - Air Transportation and Impact
DLR - Research theme (Project):L - Climate, Weather and Environment, L - Air Transport Operations and Impact Assessment
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Earth System Modelling
Deposited By: Grewe, Prof. Dr. Volker
Deposited On:08 Nov 2022 15:16
Last Modified:30 Nov 2022 14:03

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