Belgians guide Solar Impulse 2 around the world


Wim De Troyer and Luc Trullemans, two Belgian meteorologists at the RMI (Royal Meteorological Institute of Belgium) are using their weather forecasts to set the pace for each leg of a flight by Solar Impulse 2, a prototype aircraft that is fully solar-powered.

Solar Impulse 2's flight around the world began in Abu Dhabi on 9 March 2015. Each leg takes three to four days. The flight will involve twelve legs in total, comprising 500 hours' flight time spread over 5 months.

The Mission Control Centre for Solar Impulse 2 is located in Monaco, where a fifty-strong team of engineers, pilots, air traffic controllers and meteorologists work to keep everything running smoothly. The meteorology department is run by two Belgians: Luc Trullemans and Wim De Troyer, who have a crucial role to play both before and during each flight.

Trullemans and De Troyer are constantly screening thousands of data samples on their computers to determine whether a flight is viable and which route is best. “I produce a single table with the most important parameters to give the other team members a clear picture,” explains Trullemans. “It's meant to be easy to read. In fact, you can tell if it's good or bad news by the colours - we use red, orange and green. But each of those tables takes a good three hours of complex calculations to make."

Central to these considerations are the level of cloud cover (the more clouds, the less chance of storing solar power), rainfall, number of sunshine hours, wind speed and direction, and air pressure. Too few hours of sunshine could be fatal. The aircraft must be able to fully recharge its batteries during daytime cruising at 28,000 feet before a four-hour glide down to 6,500 feet for the night flight. If all the boxes are green, Trullemans signals the team to begin preparations for take-off within 24 hours. He also helps to sketch out the ideal flight path, with recommended heights and speeds.

Trullemans is a very prominent figure in his field. The former weatherman has a great deal of experience with major flight endeavours - he was an advisor for the successful balloon flights around the globe by the Swiss Bertrand Piccard in 1999 and the American Steve Fossett in 2002. Raymond Clerc, Director of the Mission Control Centre, is full of admiration for the precision of Trullemans' work. “Last year he forecast strong winds blowing up from 6pm during a planned test flight, which meant it couldn't proceed. In reality, the first strong gust came along at 17:58... (genial laugh). Looks like Luc was out by 2 minutes there.”

The two meteorologists are not the only support for the Solar Impulse project to come from Belgium. The Belgian multinational Solvay is a proud partner of Solar Impulse 2. Since joining the Solar Impulse project in 2004, its research and innovation teams have been essential in minimising the aircraft's weight - thanks to Solvay's unique specialist knowledge of ultra-strong, ultra-light materials - and in maximising the batteries' storage capacity, allowing the aircraft to also fly at night. Solvay is supplying 15 products, which have been used in more than 6,000 of the aircraft's components. Pierre Clamadieu, CEO of Solvay: "As the first historical partner of Solar Impulse, Solvay is now prouder than ever - our recent acquisition of Cytec means that over half the aircraft's structure is now composed of Solvay materials. Once more, Solvay's 'flying lab' demonstrates our contribution to making the impossible possible through our innovative solutions for clean energy and CO2 emission reduction."