NASA is studying contrails to determine if more environmentally friendly aircraft fuels might reduce their formation.

Contrails are lines of clouds left by high-flying aircraft formed when water vapor in engine exhaust condenses and freezes. The clouds themselves are made up of ice particles and some scientists worry that a global cumulative effect might be to trap heat in the atmosphere.

"Contrails are believed to be a major source of pollution," said Rich Moore, a research scientist in NASA's Langley Aerosol Research Group Experiment. "With this mission, we're looking not so much at correcting contrails, but at preventing them."

The study involves Boeing's ecoDemonstrator Explorer aircraft, a 737-10, being followed by NASA's flying science laboratory, a DC-8. The 737 switches between tanks of conventional fuel and 100 percent sustainable aviation fuel while the DC-8 measures emissions and contrail ice formation.

Scientists hope the data collected will determine if sustainable aviation fuel will help reduce the formation of contrails.

Research from NASA over the past decade has shown that using sustainable aviation fuels can cut particle emissions, and efforts are focused on matching the performance of conventional fuel without contributing more carbon dioxide.

Still, sustainable aviation fuel (SAF) has a long way to go before becoming commonplace. The World Economic Forum estimates that less than 0.1 percent of global consumption is SAF, which is considerably more expensive than conventional fuel while suffering from a lower energy density - bang per buck if you will.

According to the World Economic Forum: "Planes would therefore need to carry high volumes of SAF to make long-haul flights - such high volumes that it could become impractical."

All the same, Virgin Atlantic did manage a commercial flight from Orlando to London Gatwick in 2018 on SAF.

As for NASA's contrail work, the plan is to publish the results within a year. "One of the most amazing things about this collaboration is that this data will be released publicly with the world," Moore said.

The clock is ticking. Airlines that are members of the International Air Transport Association (IATA) have committed to achieving net-zero carbon emissions from their operations by 2050. Should SAF be shown to cut contrails, progress toward that goal will be highly visible. ®

https://www.theregister.com//2023/10/31/cutting_contrails_with_saf/