Can we really make flying green?

CO₂ emissions from the aviation industry are expected to triple by 2050. But rather than suggesting we give up flying altogether, the Imperial community is working on some clever – and surprising – solutions.

When a 24-hour deluge hit the city of Mumbai in 2005, Swapnil Jagtap (PhD Civil Engineering 2022) wasn’t unduly worried. The city rarely flooded, he reasoned, and even when it did, his flat was not affected. This time, though, was different.

The water rose and rose, and by the time the storm ended, his home was under five feet of water – and the city was devastated. This was the first time Jagtap was exposed to the change in weather patterns brought about by climate change – but it wouldn’t be the last.

In 2017, in Orlando, Florida, he witnessed a level three hurricane: the local community was without power for a week. “And, of course, as someone from a tropical climate, I always thought European heatwaves were weak,” he says. “Not anymore. We need to act on climate change, and I always wanted to use my engineering skills for something impactful, something big. That’s why today, my research is focused on sustainable aviation.”

Right now, decarbonising air travel is one of our biggest challenges – aviation contributes around 3.5 per cent of the total manmade climate forcing across all industries.

This doesn’t seem like a lot, says Rafael Palacios, Professor of Computational Aeroelasticity at the Department of Aeronautics and Director of the Brahmal Vasudevan Institute for Sustainable Aviation, “but then, you realise that everyone has a plan for decarbonisation apart from some very hard-to-decarbonise sectors, aviation being one of them. Aviation is unlikely to be net zero by 2050 – planes have a lifespan of more than 20 years, so we should already be building those sustainable planes by now. The technology is clearly behind the curve.”

And that is what the Brahmal Vasudevan Institute for Sustainable Aviation, Imperial’s flagship multidisciplinary research centre in net zero aviation technologies, is hoping to change. Established with a visionary £25 million gift from Brahmal Vasudevan (Aeronautical Engineering 1990), founder and CEO of private equity firm Creador, and his wife Shanthi Kandiah, founder of legal firm SK Chambers, it opened in 2022.

The Institute is focused on maintaining the benefits of aviation in a way that continues to be safe, accessible and sustainable. “We need to be able to quantify the adverse impacts of aviation on the environment, rethink the way flying currently works within the wider transport system, and propose sustainable solutions valid across the full life cycle of the aviation system,” says Palacios. “Sustainable aviation fuels (SAFs) don’t yet exist in the volume they are needed. Right now, there is a competition of ideas – including biofuels, hydrogen and power-to-liquid fuels – and no clear winners. The Institute will be the perfect place for all these ideas to come together."

Jagtap, who was funded by the President’s PhD Scholarship, was named one of Forbes’ 30 under 30 for one of those ideas: a PhD focused on his new hydrogen aircraft design. Picture an aeroplane and most of us picture a tube wing aircraft, such as a Boeing 777 – essentially a tube with wings. A version of that design capable of carrying cryogenic hydrogen tanks would have to have a fuselage 40 per cent bigger. Or you could design something entirely different, as Jagtap did: a blended wing body aircraft. It sounds dry but the reality is beautiful: a hydrogen-powered aircraft with zero emissions where the wings and the fuselage are a single object: a manta ray of the skies.

Of course, designing such an aircraft is one thing; building it and scaling the systems needed to get it working globally is quite another. Jagtap emphasises that his work is at the conceptual state and, as yet, he hasn’t published his research, though he is hoping to do so later this year. Hydrogen isn’t a magic potion, either: it comes with its own problems.

While hydrogen combustion has zero carbon emissions and creates lesser contrails – the white streaks an aircraft leaves in the sky, which contain harmful particles – producing it conventionally is sufficiently carbon-intense to wipe out any gains.

Airports don’t currently have the infrastructure to handle large quantities of hydrogen either, as it has to be handled in a cryogenic state. “But hydrogen can be produced in 59 different ways – and biofuels in 58 – so I explored these
different ways in my PhD and the best routes we can use to produce these alternative fuels,” says Jagtap. “This helps fuel manufacturers to focus their efforts, improving supply chain and manufacturing efficiency.”

In the absence of abundant and affordable SAFs coming online any time soon, finding ways of burning less conventional fuel is vital. Palacios’s own work seeks to find new ways for planes to be efficient: to free aviation from the constraints of its traditional design concepts. Using computational modelling, he examines what fuel efficiency might look like if those parameters are changed.

What would happen, for example, if wings were much, much longer and thinner? Greater aerodynamic efficiency for a start, he says. “Of course, now you have wings that are 60 metres long, when before they were 30 metres long. That has challenges – firstly, they wouldn’t fit in one of today’s airports. But they outperform current airplanes in terms of fuel efficiency. So, you need much less fuel for the same performance.” He is currently working with Airbus on a possible solution to the airport problem: folding wings.