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NASA satellites will also capture images of contrails forming from the SAF-powered plane as part of the testing, a collaboration between Boeing, the US space agency, and United Airlines.
Boeing's second Explorer demonstrator, a 737-10 destined for United Airlines, will fly with SAF and conventional jet fuel in separate tanks, alternating fuels during testing. NASA’s DC-8 Airborne Science Lab will fly behind the commercial jet, measuring the emissions produced by each type of fuel, and the contrail ice particles.
The researchers aim to understand how advanced fuels, engine combustor designs and other technologies could reduce contributions to atmospheric warming. Tests will assess how SAF affects the characteristics of contrails, the persistent condensation trails produced when airplanes fly through cold, humid air. While their full impact is not yet understood, some research has suggested certain contrails can trap heat in the atmosphere.
“We are honoured to collaborate with NASA, United Airlines, and other valued partners on research that will strengthen the industry's understanding of the benefits of SAF beyond reducing carbon emissions,” said Boeing chief sustainability officer Chris Raymond. “We've solved hard problems before, and if we continue to take meaningful actions, I'm confident we'll achieve a more sustainable aerospace future, together.”
The project is the latest phase in a multi-year partnership between Boeing and NASA to analyse how SAF can reduce emissions and enable other benefits. Compared to conventional jet fuel, SAF – made from a range of feedstocks, such as cooking oil and household waste – can reduce emissions by up to 85% over the fuel's ‘life cycle’. SAF also produces less soot, Boeing said, which can improve air quality near airports.
The collaboration “has the potential to not only help us better understand contrails, but to provide the full scope of what our transition to SAF can provide beyond greenhouse-gas reductions,” said United chief sustainability officer Lauren Riley.
California company World Energy will supply SAF for the tests. Other support includes funding from the US Federal Aviation Administration (FAA), technical expertise and funding from GE Aerospace, and expertise and instrumentation from the German Aerospace Centre (DLR).
“To achieve climate-compatible aviation, we need close international cooperation. The German Aerospace Centre has decades of experience in research on the climate impact of the entire aviation system by advancing measurement technology and simulations,” said Markus Fischer, DLR divisional board member for aeronautics. “The continuation of transatlantic cooperation now finds a new summit, and underlines the international commitment to reduce the climate impact from aviation's CO2 and non-CO2 effects.”
Boeing and NASA conducted SAF emissions ground testing on an Alaska Airlines 737-9 in 2021, and 777-200ER and 787-10 flight-test jets in 2022. Boeing has committed to deliver commercial aeroplanes compatible with 100% SAF by 2030.
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