[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/10355\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EThe quest for hypersonic and hydrogen-fuelled air travel\u003C\/h2\u003E\u003Cp\u003ETraditionally designed for efficiency and safety, passenger planes are now increasingly being developed with climate neutrality in mind as well.\u003C\/p\u003E\n\n\u003Cp\u003ESo the question arises: will people one day be able to count on flying from Paris to New York in less than an hour without contributing to global warming?\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003ESky-high ambitions\u003C\/strong\u003E\u003C\/p\u003E\n\n\u003Cp\u003EThat\u2019s what the EU-funded\u0026nbsp;\u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/id\/769246\u0022\u003ESTRATOFLY\u003C\/a\u003E\u0026nbsp;project proposed: a Mach 8 airliner \u2013 a hypersonic aircraft that can go at least 9 500 kilometres per hour, or about eight times the speed of sound. STRATOFLY, which ran from 2018 to 2021, built on three previous EU research projects in the field.\u0026nbsp;\u003C\/p\u003E\n\n\u003Cp\u003E\u2018It\u0027s going be a real challenge,\u2019 said Nicole Viola, who coordinated STRATOFLY and is a professor at the Polytechnic University of Turin in Italy. \u2018Maybe we\u0027re not ready yet for Mach 8 right now. But I\u0027m sure that I will see a hypersonic airliner in my lifetime.\u2019\u003C\/p\u003E\n\n\u003Cp\u003ESTRATOFLY designed a prototype in the form of a computer model for a hydrogen-fuelled hypersonic plane. The project focused on innovative ways of powering an aircraft able to carry 300 passengers.\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cspan lang=\u0022EN-US\u0022 style=\u0022mso-ansi-language:EN-US\u0022\u003EIn the meantime, the political appetite in the EU for supersonic passenger air travel has waned in large part because of environmental concerns, not least noise and emissions of pollutants that cause climate change.\u003C\/span\u003E\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cspan lang=\u0022EN-US\u0022 style=\u0022mso-ansi-language:EN-US\u0022\u003ERecent EU regulatory initiatives, including a new law to cut aviation emissions, have highlighted the political scepticism in Europe by limiting incentives for supersonic commercial flights.\u003C\/span\u003E\u003C\/p\u003E\n\n\u003Cp\u003EStill, in the worlds of civil aviation and research, ambitious ideas persist to make faster and cleaner aeroplanes.\u0026nbsp;While these technologies might take many decades to enter service, it\u2019s important to dream big now, according to scientists.\u003C\/p\u003E\n\n\u003Cp\u003EThe EU is funding numerous research initiatives covering a range of fundamental technologies, including hydrogen-related ones, to make aviation safe, efficient and clean. The goals are aligned with national, international and business priorities.\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003ENot so fast\u003C\/strong\u003E\u003C\/p\u003E\n\n\u003Cp\u003EThe STRATOFLY design came with plenty of technological challenges. But one of the biggest sticking points wasn\u0027t so much to create an aircraft that could fly fast but rather to design one that could also fly slowly.\u003C\/p\u003E\n\n\u003Cp\u003E\u2018The challenge isn\u0027t in the hypersonic phase,\u2019 said Viola.\u003C\/p\u003E\n\n\u003Cp\u003EThe hypersonic airliner that she and her colleagues dreamed up would need not only to fly at high speeds but also to take off and land at much lower velocities.\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003EI\u0026#039;m sure that I will see a hypersonic airliner in my lifetime.\r\n\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EProfessor Nicole Viola, STRATOFLY\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\n\n\u003Cp\u003EThis produces design challenges. An engine capable of hypersonic speeds, for example, isn\u0027t the best option for lower speeds. A hypersonic engine also needs a huge inlet to \u201cbreathe in\u201d air, which gets mixed with hydrogen.\u003C\/p\u003E\n\n\u003Cp\u003E\u2018As the speed grows, the inlet grows as well,\u2019 said Viola.\u003C\/p\u003E\n\n\u003Cp\u003EBut at a lower speed, less air needs to get sucked into the engine. This requires scientists to make a compromise in the design.\u003C\/p\u003E\n\n\u003Cp\u003EThe 94-metre aircraft contains a massive inlet in the nose, with sliding doors to regulate the air intake.\u003Cbr \/\u003E\n\u003Cbr \/\u003E\nFrom take-off to a speed of around 5\u0026nbsp;000 kilometres per hour, six smaller engines do all the work. Above that velocity, one massive engine extending along the tail thrusts the aircraft forward.\u003Cbr \/\u003E\n\u003Cbr \/\u003E\nBeyond questions of pure design, STRATOFLY demonstrated the advantages of exploiting liquid hydrogen instead of hydrocarbon as an aircraft fuel.\u0026nbsp;\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cb\u003EBack to the future\u003C\/b\u003E\u003C\/p\u003E\n\n\u003Cp\u003EThe STRATOFLY proposal is only a concept designed to demonstrate what a hypersonic airliner could look like. It allows researchers to test and think about new technologies that might take decades to build successfully.\u003C\/p\u003E\n\n\u003Cp\u003EToday, however, the aviation industry might be returning to supersonic airliners like the famed Concorde, which was in service for more than 30 years before being retired in 2003. Used by Air France and British Airways, the Concorde was best known for its Paris-New York and London-New York routes featuring one-way travel times of three to three-and-a-half hours.\u0026nbsp;\u003C\/p\u003E\n\n\u003Cp\u003EBoom Aerospace, a US company, has already signed contracts on supersonic design with United Airlines and American Airlines.\u003C\/p\u003E\n\n\u003Cp\u003EAnd hypersonic flight is attracting attention beyond civil aviation. The space industry is eyeing the technology to build craft that can take off like a plane, a development that could reduce the need for expensive rocket launches.\u003C\/p\u003E\n\n\u003Cp\u003E\u2018Hypersonic is somewhere between aviation and space,\u2019 said Viola. \u2018So, eventually, we will see one of those fields take up the technology.\u2019\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cstrong\u003EClearing the air\u003C\/strong\u003E\u003C\/p\u003E\n\n\u003Cp\u003ERegardless of whether such high-speed flying eventually becomes possible, making aviation fuels cleaner is a growing EU priority. Today, aviation accounts for around 2.5% of global CO2\u0026nbsp;emissions.\u003C\/p\u003E\n\n\u003Cp\u003EHydrogen might be the solution here, according to Professor Bobby Sethi of Cranfield University in the UK.\u003C\/p\u003E\n\n\u003Cp\u003E\u2018We have been researching hydrogen for aviation for a long time,\u2019 Sethi said. \u2018The costs, however, have long dampened enthusiasm. But its introduction is a question of when, not if.\u2019\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003EInvest aggressively in hydrogen to reduce the transition time.\r\n\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EProfessor Bobby Sethi, ENABLEH2\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\n\n\u003Cp\u003EHe coordinated the EU-funded project \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/id\/769241\u0022\u003EENABLEH2\u003C\/a\u003E, which examined the potential of hydrogen in aviation over four years through last November.\u003C\/p\u003E\n\n\u003Cp\u003EThere is much to like about hydrogen, according to Sethi.\u003C\/p\u003E\n\n\u003Cp\u003EIt is one of the most abundant elements on Earth and, if generated with renewable energy, emits no CO2. In addition, the ENABLEH2 research showed that hydrogen combustion systems will deliver lower emissions of NOx, another greenhouse gas, than kerosene.\u003C\/p\u003E\n\n\u003Cp\u003EFurthermore, aircraft powered by hydrogen can fly longer distances than electrified planes, which will likely be used only for short to medium-range flights.\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cb\u003ETransition routes\u003C\/b\u003E\u003C\/p\u003E\n\n\u003Cp\u003EBut then there are the costs. Hydrogen behaves differently than regular aviation fuel, so planes and some airports would need to be completely redesigned\u0026nbsp;\u2013 a transition that could take around 20 to 30 years, according to Sethi.\u003C\/p\u003E\n\n\u003Cp\u003E\u2018We could technically redesign an existing aircraft, like an Airbus A380, to use hydrogen,\u2019 he said. \u2018But you would need to install hydrogen tanks in the aircraft. We can\u2019t just store the fuel in the wings as is done now, which makes the model uncompetitive with regular fuel or sustainable aviation fuels.\u2019\u003C\/p\u003E\n\n\u003Cp\u003EThat\u2019s why most predictions foresee an intermediate period when the industry uses alternative sustainable aviation fuels (SAF), which are generally made from sources such as biomass or waste and produce less life-cycle CO2\u0026nbsp;compared with regular jet fuel.\u003C\/p\u003E\n\n\u003Cp\u003EAccording to Sethi, it would be better to \u2018focus on carbon capture of aviation emissions in the intermediate period and invest aggressively in hydrogen to reduce the transition time.\u2019\u003C\/p\u003E\n\n\u003Cp\u003ERegardless of the path taken, the key for Sethi is a long-term and sustainable future for the industry.\u0026nbsp;\u0026nbsp;\u003C\/p\u003E\n\n\u003Cp\u003E\u2018Aviation has enormous social and economic benefits,\u2019 he said.\u0026nbsp;\u2018It has lowered transport times across the globe drastically and has been a driver of economic growth through, for example, tourism. We can\u2019t let that be destroyed.\u2019\u0026nbsp;\u003C\/p\u003E\n\n\u003Cp\u003E(This article was updated on 10 May 2023 to add EU political context and to mention the existence of an array of European projects in the field)\u0026nbsp;\u0026nbsp;\u003C\/p\u003E\n\n\u003Cp\u003E\u003Cem\u003EResearch in this article was funded by the EU. 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