Few explorers have reached the heights, literally and figuratively, that Bertrand Piccard has. He is the quintessential modern explorer, for whom every big mission has a purpose, which generally boils down to environmental and climate-change awareness.

In 1999 he was the first person to circumnavigate the globe non-stop in a balloon, called Breitling Orbiter 3. Then he and André Borschberg, a Swiss entrepreneur and pilot, were first to fly around the world, in stages, in a solar airplane called Solar Impulse. Now he’s in the midst of what looks like his most technologically ambitious mission yet: to fly around the planet in a green-hydrogen fuel-cell aircraft. Planned for 2028, this trip would be the first nonstop zero-emission circumnavigation in human history.

It’s easy to see how this is the logical next step in Piccard’s remarkable career. And yet there was nothing straightforward about the early stages of the journey that got him here. The path to becoming one of the world’s most celebrated aeronaut-aviators began with hang gliding, which Piccard took up in his teens to confront his fear of heights. He did so with a zeal that earned him the European hang-gliding aerobatics championship in 1985.

Still, it would be years before Piccard joined the family business of exploration. In the mid-1990s he earned an MD degree in psychiatry and established a psychiatric practice before a chance opportunity led to a sideline in ballooning. Invited to participate as copilot in a trans-Atlantic balloon race—which he and his teammate won—he immediately became seized with the idea of being the first to circumnavigate the globe in a balloon.

Such a project resonated with his family’s history. His grandfather, Auguste Piccard, was a physics professor-turned-inventor who built the first pressurized aluminum gondola. It enabled him and a colleague to be the first people hoisted into the stratosphere, by a hydrogen balloon, in 1931. Besides being the first person to see the curvature of the Earth, Auguste was the inspiration for the Professor Cuthbert Calculus character in The Adventures of Tintin series of comic novels.

Later, Auguste invented and built the first bathyscaphe. In 1946 he was joined by his son, Jacques, a marine engineer, with whom he made a series of record descents. This work culminated in the Trieste, in which Jacques and a U.S. Navy Lieutenant, Don Walsh, plumbed the depths of the Mariana Trench in 1960, becoming the first people to descend 10,916 meters to reach the deepest spot on Earth.

In an homage to the exploring spirit of multiple generations of Piccards, the captain of the Enterprise starship in various reinventions of the science-fiction series Star Trek starting in 1987 was named Jean-Luc Picard.

IEEE Spectrum interviewed Bertrand Piccard at a pivotal moment in the hydrogen-powered aircraft project, with the plane, called Climate Impulse, about 40 percent built. Piccard spoke about the contributions to the Climate Impulse project of his corporate sponsors, including Airbus, and about why he’s confident that hydrogen will eventually succeed as an aviation fuel.

This transcript has been lightly edited for concision and clarity.

Bertrand Piccard, left, and Prince Albert of Monaco, right, take off during the 25th International Hot Air Balloon week, in Chateau d’Oex, Switzerland, in 2003.Martial Trezzini/AP

You are the grandson and the son of famous explorers. Was there any sort of understanding, spoken or otherwise, that you would go into this business of exploration?

Bertrand Piccard: As a child, I was really inspired by what my grandfather and my father did, but also by why they did it. When my grandfather made the first flight to the stratosphere and invented the pressurized cabin, his goal was to show that it was possible to fly at very high level, above the bad weather, in rare air, less dense air, which means that aviation would be more reliable and more efficient by burning less fuel. And when my father made his dive with a bathyscaphe to the deepest spot on Earth in the Mariana Trench, his goal was to check if there was life down there at a period where the governments wanted to drop their radioactive and toxic waste in the ocean trenches.

So both had a vision that was about protection of the environment, about quality of life, about the use of technology to improve the quality of life. So that was a fantastic example. I was thinking, “Wow, my grandfather and my father, they’re doing good.” Their friends were astronauts, divers, test pilots, environmentalists. So during my childhood, the people coming to our home were people like Wernher von Braun, and American astronauts. I met Charles Lindbergh at the launch of Apollo 12 when I was 11 years old. And those were the moments when I thought that it was the only way to run my life. To be an explorer. There was no question. That was really what interested me. It’s maybe strange to say it this way, but I thought it was a normal way to live, to achieve what has never been done, to try what nobody has achieved. And then, while growing up, I realized that that was not the mainstream. The mainstream is about fears. Fear of the unknown, remaining in the certitudes, in the routine, cultivating the paradigms, the dogmas. Basically, I became an explorer in both dimensions. In the external world with aviation, but also the internal world with psychiatry, psychotherapy, hypnotherapy.

What people forget is that I also have a mother, and it’s my mother who was very much interested in psychology, spirituality, philosophy, and she opened that part of life to me. So basically, I made a combination of what I learned from my father and from my mother.

Solar Impulse 2, the solar powered plane, was piloted by Swiss entrepreneur André Borschberg over the pyramids in Giza, Egypt, prior to landing in Cairo on 13 July, 2016.Jean Revillard/Getty Images

How did you get the idea for Climate Impulse?

Piccard: With Breitling Orbiter, I flew nonstop around the world, but with carbon emissions. With Solar Impulse, there were no emissions, but there were 16 stopovers. So the ultimate flight was still to be done. The ultimate flight is around the world, nonstop, zero emission. And I was thinking, “How can I do that?” And what we found as the most relevant way to do it is with liquid, green, hydrogen. You produce your hydrogen with electrolysis of water through solar energy, wind energy, hydroelectricity, for example, so you have decarbonized hydrogen. You put it at minus 253 degrees Celsius, so it remains liquid. And you use the boil off, that means the little part of hydrogen that is evaporating, and put it through fuel cells that makes electricity for the electric motor.

And this is why now I’m really putting my time and my enthusiasm into this Climate Impulse project because it’s a way to promote the newest technological solutions. It’s a way to show that another future is possible, and that’s very important for me. You can always do better. You can invent. You can challenge yourself. You can challenge the status quo. You can raise enthusiasm, restore hope, bring people with you, and do something better. And I believe this is really what I want to do now in the last part of my life.

What are some of the most important technical challenges that you faced in the design phase of the Climate Impulse plane?

Piccard: There are two parts. One is the aerodynamic part and the other is the propulsion part. So for the aerodynamic, we were supported by Airbus in order to be able to have the most efficient airplane in terms of aerodynamics. And the big part of the propulsion system is the hydrogen tank. How can you keep liquid hydrogen liquid for nine days with exactly the right quantity of it that will evaporate to go to the fuel cell? And for this we’re working with ArianeGroup, for example, the European space-rocket manufacturer. We’re also working with Syensqo, a spin-off of Solvay, as the main technological partner. They are the specialist for the composite materials, the membranes for the fuel cell, the coating of the plane to keep the aerodynamics as good as possible, and all the adhesives.

Right now we are studying how to have an airplane fly on hydrogen for so long. For the test, we will have smaller tanks with hydrogen that will allow us to fly a couple of days to train, to test everything. And then when we go around the world, we will have much bigger hydrogen tanks that will be built out of composite materials.

Bertrand Piccard [center] and Raphaël Dinelli [left] stand inside the wooden frame of an aircraft at a workshop on the Atlantic coast of France.Climate Impulse

You mentioned your partnership with Airbus. Can you describe this partnership a little bit more? What are they helping you out with?

Piccard: First, they did a feasibility study. Because in the beginning, before I was going to bring partners on board and sponsors on board, I wanted to be sure that it was possible. And I said to Guillaume Faury, the CEO of Airbus, “Look, this is a design of the plane I want to use. This is the concept of the plane. Now, what do you think about it?” And he put his team studying the project. They said, “Okay, you can do it, but you have to change quite a lot of things on the structure of the plane.” And so they redesigned the plane. They made a new shape, and they told me: “Like this, you can do it.” So that was really the trigger to go for it. And then I started to go and look for sponsors.

Thanks to the green light of Airbus, I could gather the sponsors needed to launch the construction of the airplane, and now 49Sud has built roughly 40 percent of the plane. It’s a plane that is molded. We’ve received the molds. We put the carbon fiber and the epoxy in the molds and then we cure it. It goes into the oven. It goes outside. We put some more layers. Put it back in the oven. So you’re really building the planes with your hands.

So on one side, it’s the workers making this plane with their hands. On the other side, it’s the most modern materials that you can find in the world, for stiffness, for lightness. For example, our lead partner Syensqo managed to make the plane 10 percent lighter than what was planned just because they have the best carbon-fiber materials.

Who are some of the key members of the team?

Piccard: My partner, Raphaël Dinelli. He’s originally a French navigator for ocean racing. He did the Vendee Globe four times, but he’s also a composite engineer, the CEO of 49Sud, and he’s running the construction of the plane. We partner together and we will fly together.

A model of the twin-hull Climate Impulse aircraft hung over an area in a hangar where Swiss aviation pioneer Bertrand Piccard spoke about the plane, which will be powered by liquid hydrogen. The occasion was the public unveiling of the project in Les Sables d’Olonne, France, on 13 February, 2025.Yohan Bonnet/AP

Why do you have confidence that hydrogen will eventually succeed as an aviation fuel?

Piccard: It’s a very interesting fuel in terms of energy density, and it’s a fuel that is completely clean. It’s not only a question of carbon emission. There are no emissions at all. So it’s good also for quality of air. With hydrogen you have electric motors, so it’s silent. So for the airports, you have no problems with the neighborhood. This is also important. It’s true that we are very, very early in terms of the use of hydrogen in aviation. And there are some people who criticize this project and say, “It’s impossible. Hydrogen is too expensive. You need to change all the airplanes. You need to change all the airports. You need to create a new industry.” And I answer, “Yes. But it’s not the first time that we’ve done this.” The mobile phone industry started exactly like this. It was $15,000 for a mobile phone the size of a suitcase. And people thought that’s a niche. But now we all have a mobile phone in our pockets.

Are you already thinking of a big challenge or project beyond Climate Impulse? Is there another big one in your life after Climate Impulse?

Piccard: I’m afraid to tempt fate [laughs]. I want to finish this one first, and then we’ll see. It’s a big project. It’s not easy, so I really want to focus on it. The ultimate success for hydrogen flights is when you have an airplane taking off like a rocket with liquid hydrogen and oxygen, like the Ariane rocket. It would take 100 passengers to the limit of space, then you cut the engine. You fly parabolic, suborbital, and you can fly from New York to Sydney in two hours. And this is something you can only do if you fly suborbital and you have a rocket engine with oxygen and hydrogen. And I’m not sure I will see this with my own eyes because I’m already 67, but I’m sure that younger generations will see it. And then I hope they will remember that a long time before, there was a Climate Impulse project leading the way to this achievement.