Solar Impulse 2 on a test flight over Payerne, Switzerland. Image via Solar Impulse

Solar Impulse 2 on a test flight over Payerne, Switzerland. Image via Solar Impulse

APEX Insight: Mission engineers assisting with Solar Impulse 2’s solar-powered flight around the world explain that satellite connectivity allows the command center to be in contact with Si2 at all times. From transmission of biometric data to voice and text messages for banter, Si2 is a symbol of future clean energy and the possibilities of a fully connected aircraft.

It’s never certain when or where Solar Impulse 2 (Si2) will land next. Controlling a solar-powered aircraft – part airplane, part glider – can be finicky, explains Julie Conti, press relations officer for Solar Impulse. In other words, there’s no “X” to mark the next stop on Si2’s solar-powered flight around the world.

During the recent crossing of the Atlantic, it was estimated that Si2 might land in Ireland, France, Portugal, Spain, maybe Morocco – altogether an area about the size of India. A landing in France – Le Bourget to be exact – would have had great historical significance, emulating Charles Lindbergh’s solo flight across the Atlantic in 1927. But instead, Si2 made its stop in Seville, Spain.

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Solar Impulse 2 approaching the Statue of Liberty in New York City on June 11, 2016. Image: Solar Impulse

On an earlier leg of the round-the-world flight, Si2 aimed for New York City. The goal was to circle the Statue of Liberty during the day, when it would be easier for crowds to spot the airplane. But instead, the landing had to be squeezed into a weather window in the wee hours of the morning. “Every time we find a good weather window, we go for it,” Conti said. “It would be a pity to say, ‘Let’s wait for a [better] day,’ and have the plane grounded for weeks.”

Airborne Technology Lab

Weather windows are prime opportunities for flying. They are determined with the help of a team of 40 mathematicians, meteorologists, engineers and air traffic controllers at the Monaco Mission Control Center (MCC), who make recommendations on what routes pilots should take and the best times to fly.

To facilitate communication between Si2, at 28,000 feet in the sky, and the MCC on the ground, the aircraft is outfitted with a customized 5 kg Cobham SATCOM antenna that speaks to Inmarsat’s SwiftBroadband satellites. The front-facing components – apps that report on solar cell energy, battery wattage, cabin temperature, altitude, weather updates, air traffic control and even pilots’ biometrics – are serviced by SITAONAIR.

“It’s super reliable,” said Michael Anger, lead mission engineer, Solar Impulse. “Sometimes there are drop-offs of a second, when we go from one satellite to the other … but it doesn’t disturb us at all.” Real-time connectivity is even used to monitor the pilot’s every breath. Conti explained there is one person whose sole responsibility at the MCC is to listen to the the pilot’s breathing, keeping an ear out for nuances that may indicate if the pilot is relaxed or anxious.

Si2 features several of SITAONAIR’s flight tracking, messaging, health monitoring and weather apps – why Aurelie Giles, Corporate Communications for the connectivity solutions provider, refers to Si2 as an “airborne technology lab.” “You don’t have an airline that has the whole shop of apps, and that’s what we’re using Solar Impulse [for], as an inspiration for the commercial sector,” she said. “Our role with Solar Impulse is very much the same as when we provide communications to commercial airlines,” Giles said. “Commercial airlines could have their fleet of aircraft connected from nose to tail in the same way Solar Impulse is connected.”

Keeping the Conversation Going

During the crossing of the Pacific last summer, which lasted a consecutive five days and five nights, André Borschberg, who was piloting Si2, felt “cockpit fever” kick in. His spirits were low; he wasn’t sure he could pull the feat of flying nonstop across the long stretch of ocean from Nagoya to Hawaii.

During these times, chatting with the pilot – not just through the transmission of technical data – is crucial, explained Yves Heller, head of Structural Testing for Solar Impulse and a mission engineer. Through e-mails and voice messages, the MCC is constantly in conversation with the pilots as they fly. Heller likened it to striking a discussion with someone on a long road trip.

But banter aside, conversation is also used to cure boredom and keep the pilots from dozing off. Si2 pilots are allowed to sleep for 20 minutes every three hours, making a long leg as much an achievement of human endurance as it is of solar-powered flight. “No one has ever been in a plane for five days and five nights, alone, eating special food, everything in this 3.8 cubic meter [cockpit] – bathroom and everything,” Conti said.

A Touch of Business-Class Comfort

Designing a cockpit where the pilot’s only physical comfort is his seat was a challenge Lantal’s air-filled cushions held up to. Consider first that the world’s longest nonstop commercial flights clock in at about 17 hours. Si2’s Pacific crossing was 117 hours and 52 minutes – breaking the record for the world’s longest nonstop flight.

Typical foam-padded airline seats may be acceptable on a long-haul flight, but on a nonstop flight upwards of 100 hours, the passenger or, in this case, the pilot, might feel some discomfort, said Lou Rickenbacher, Lantal’s director of Markets. However, Si2 pilot André Borschberg was comfy throughout the duration of the five-day long crossing of the Pacific Ocean thanks to the seat’s pneumatic comfort system (PCS). The secret? A control that allows the pilot to inflate and deflate the seat as needed, plus massage functionality. The Si2 seat is an adaptation of Lantal’s lie-flat business-class seats, which are flying on Air Canada, JetBlue, Lufthansa and SWISS airlines. “If you think about going into the office from nine to five, Monday morning to Friday afternoon, that’s a whole week,” Rickenbacher said, comparing the duration of the pilot’s confined position to a desk job. “So [the seat’s] got to be comfortable.”

Seeing Green

Si2’s quest to fly around the world on only solar energy has gained much attention for pioneering the way toward a fossil fuel-free future in commercial aviation. James Cameron, Leonardo DiCaprio, Pharrell Williams, Ban Ki-moon and Marion Cotillard have tweeted about it.

“The enthusiasm the project brings … it’s transmitted to the world,” Anger said. “We can really inspire people, the younger generations, [to] explore new boundaries, [to] do something new, and also show that the technology we have is already that far that we can fly it in an airplane, day and night, with solar energy.”

Caroline is managing editor at APEX Media.