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  • Writer's pictureBalamir Sahin

Interview with Sebastian Eastham, Research Scientist, Laboratory for Aviation and Environment, MIT


Balamir: Please tell us about yourself.

Dr. Eastham: I’m a research scientist in MIT’s Department of Aeronautics and Astronautics. I’ve spent the last 10 years or so trying to understand how the environment is affected by the aerospace industry.

Balamir: Why did you want to become an aerospace engineer?

Dr. Eastham: I see the aerospace sector as one of humanity’s greatest achievements. I’ve wanted to be a part of that since I was a child, but at the time I thought that meant being a pilot. As I grew and realized that there were many different ways to participate in the industry, I saw that aerospace engineering could let me combine my love for flight with my passion for problem-solving and my desire for a cleaner future.

Balamir: What is the ultimate goal of the MIT Laboratory for Aviation and The Environment?

Dr. Eastham: The Laboratory for Aviation and the Environment (LAE: wants to create a sustainable future for aviation. Through flight we have more than just the ability to go on holiday – flight has made the world more connected than ever before. Flight means travel, freight, and airmail; it means new insights into our planet’s properties through scientific aircraft campaigns; it means firefighting and search-and-rescue; and it means the ability to ferry patients, doctors, and life-saving organs, between cities faster than ever before. But all of this comes at a cost to the environment. LAE wants to bring the environmental impacts of aviation down to zero, so that we can continue to benefit from this incredible industry without further harming the planet.

Balamir: How are you able to model combustion emissions of planes on a global scale?

Dr. Eastham: It takes a lot of data and a lot of computation. The basic requirement is flight schedule data, which tells us the time, aircraft, origin, and destination of every flight which took place over the course of a year. Using aircraft performance data, we simulate each flight computationally and estimate how much thrust was required at each point along the aircraft’s trajectory. At each of those points we use an emissions calculation model, calibrated against measurement data, to estimate emissions. By bringing all of that together we can estimate the emissions from commercial aviation at every point across the globe for every hour in a given year. We still need to make assumptions – for example, if we don’t have radar data then we might have to assume that aircraft are flying “direct” routes from point to point. The degree of accuracy required depends on the application, so we adapt accordingly.

Balamir: What is the basis that you use in order to quantify the impact of the emissions of planes?

Dr. Eastham: Once we have an estimate of the emissions, we have to rely on atmospheric models to try and determine what the environmental impacts are likely to be. When talking about conventional civil aviation, we generally worry most about three specific outcomes: climate change, air pollution, and noise. Different atmospheric models are needed to understand how each will be affected by aviation. For example, understanding the degree to which aircraft emissions of carbon dioxide will affect the climate is a relatively straightforward calculation. On the other hand, we needed to use global “chemistry transport models” (3-D models of the Earth’s atmosphere which simulate fluid mechanics and chemistry) to understand how emissions of nitrogen oxides (NOx) from a flight crossing the Atlantic Ocean can cause air pollution in Asia.

Balamir: How can machine learning help with reducing emissions?

Dr. Eastham: There’s a lot we still have to learn about aviation’s impacts, in part because the sector is so unique – we often can’t draw clear parallels between the effects of aviation and those from other industries. Machine learning is just one of the tools we can use to help us with this. For example, in a recent study we used a machine learning algorithm to identify aircraft condensation trails (“contrails”) in images from the NOAA GOES East geostationary satellite. By some estimates, contrails are causing as much damage to the climate as all the carbon dioxide emitted from aircraft, but contrails are very poorly understood – in part because of a lack of reliable data. Whereas humans can take hours just to mark every contrail in one image from GOES (and often make mistakes), our algorithm was able to process two full years of data and provide evidence of how contrail coverage differs by region, season, and even time of day. By looking at where contrails do or don’t form, we are learning about how we might be able to reduce their formation, persistence, and environmental consequences.

Balamir: What do you think the future holds for the aviation industry in terms of vehicles that use clean energy?

Dr. Eastham: This is an exciting time for the industry. There’s a genuine enthusiasm to identify and reduce the environmental impacts of aviation, but also a recognition that this will be a serious challenge. For example, consider just the question of how to reduce emissions of fossil CO2 from aviation. All of the clean alternatives to fossil-based jet fuel (“Jet-A”) face obstacles. Making battery-electric aircraft practical will require a significant improvement in energy density and a reduction in cost. Biofuel is a promising avenue, but is limited by issues such as land availability and water consumption. So-called “power-to-liquid fuels” may be able to overcome some of these challenges, but they are not yet economically viable. Meanwhile using hydrogen as aviation fuel would require new fueling infrastructure, new aircraft designs, and the development of a large “green hydrogen” industry. And none of these solutions necessarily address contrail formation or the air quality impacts of cruise-altitude emissions. I am confident that the future of aviation is clean, but there is not yet an obvious, scalable solution.

Balamir: What has been your toughest accomplishment so far in your career?

Dr. Eastham: Helping to bring a lab of over 20 researchers through 2020. The driving force behind LAE is its students – our graduate students overcome phenomenal technical challenges every day, and it is only through their brilliance and tenacity that our lab can make progress. Even under normal circumstances it takes a lot of mental fortitude to get through a graduate program, and the sense of camaraderie brought by seeing your peers every day in the lab can help to alleviate that. So the isolation of the lockdown and transition to remote work was, I think, especially difficult for graduate researchers. I am tremendously proud that our research team was able to not only continue their research during such a difficult time, but successfully initiate and complete several major collaborative research projects.

Balamir: What is a big milestone that you are looking forward to in your research?

Dr. Eastham: Seeing a truly zero-impact, long-haul, commercial airliner take to the skies with paying passengers. It will only happen through the concerted effort of many people, but I believe it will happen.

Balamir: To high schoolers like me and to younger generations that want to become aerospace engineers, what would be your advice to be successful in this career?

Dr. Eastham: Three things. One: accept that you’ll make mistakes, and plan for it. “Showing your working” is about more than just making your teacher, professor, or boss happy; the more time you spend explaining your logic, the more likely you are to be able to figure out what went wrong when something doesn’t work out, and fix it. Two: aerospace engineering is a tough, mathematical discipline, so make sure you really invest in your mathematical skills. Three: remember that no matter how much you love aerospace, there are going to be days when nothing works! Every aerospace engineer I have ever met is passionate about aerospace – that’s a given. But the really successful ones are the ones who just keep going no matter how many times they fail.

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