Project Spotlight: Solar Impulse flies 3500 miles Across America using only solar energy

A revolutionary airplane, Solar Impulse, successfully flew across the USA in six legs covering more than 3500 miles. It made the trip despite weather challenges and damage to the wing on its final flight. Get to know the Switzerland-based Solar Impulse team and their process for creating the first airplane to fly day and night purely on solar energy.

Solar Impulse Across America - Golden Gate Flight - Revillard

GrabCAD had the opportunity to talk with two of the Solar Impulse team members, André Borschberg and Bertrand Piccard. André (AB) is the Co-founder and CEO and Bertrand (BP) is the Solar Impulse Initiator and Chairman. Both are pilots for the project. Their revolutionary carbon fibre airplane has the wingspan of a Boeing 747 (63.4m / 208ft) and the weight of a small car (1,600kg / 3,500lb). It is the result of seven years of intense work, calculations, simulations and tests by a team of about 80 people and 100 partners and advisors. No one has ever built a plane this big and this light. The 12,000 solar cells in the wing provide four 10HP electric motors with renewable energy. By day, the solar cells recharge the 400kg / 881lb lithium batteries which allow the plane to fly at night.

What are your goals with the Solar Impulse project?

BP: The Solar Impulse project started off with the aim of building an airplane capable of flying night and day without fuel, propelled solely by solar energy. The aim of Solar Impulse is to develop a symbol which will attractively promote a pioneering and innovative spirit, particularly in the field of clean technologies. After the successes of the first historical 26-hour flight in 2010, the European flight in 2011, the international flight to Morocco in 2012, and the latest endeavor of crossing the USA from the West to the East coast, our goal is to fly around the world in 2015.

Our success however will not only come from completing a round-the-world tour without fuel, but will also motivate everyone to implement the necessary measures to reduce our dependence on fossil fuels.

Are you facing a lot of resistance from the aviation industry?

AB: Not at all. Dassault Aviation has been our aeronautical advisor from day one. The reception we received at the Paris Air Show of Le Bourget in 2011 was very positive. The aviation industry sees our project as a long-term vision for the industry.

What were your biggest challenges developing and building Solar Impulse?

AB: Firstly, not having any benchmarks and having to start from scratch surrounded by a lot of people telling us it was impossible. In order to fly day and night powered by solar energy alone and to accomplish a round-the-world tour without fuel, we always knew that the plane would require a large wingspan to reduce drag and a large surface to insert enough solar cells and produce enough energy (200 m2 / ~2152 ft2).

At the same time, we needed to build an ultra-light structure to save a maximum amount of energy and fly throughout the night on batteries. The team had to push the limits of existing technology in all fields. The result is breathtaking: the wingspan of a Jumbo Jet (63.4 m / ~208’), the weight of a car (1600 kg / ~3527 lbs.) and the average power of 24 hours on a scooter.

How available and common is the technology you used on Solar Impulse?

AB: The project was conceived in 2004 – 2005 and relied upon projected technological progress until 2009, especially in the domain of batteries and solar cells. Technologies used were optimized with the project’s partners: 50 developments with Solvay to obtain the best solutions in materials, a 30% improvement in energy density of batteries thanks to solutions provided by Solvay and Bayer Material Science, new flight instruments and man-aircraft interface with Omega, and revolutionary construction devices using carbon fibres with the Décision shipyard.

All this is used in our daily lives for lifts, cars, boats, and airplanes. We use insulation materials which can be used in all homes and household appliances. The engines can be used for electric cars. Batteries have also progressed as a direct consequence of our project.

What was your development process like?

AB: Two distinct phases: the first one consisted in identifying and developing the appropriate technologies and exploring design alternatives in order to achieve weight budget. This was a very open, exploratory phase with few constraints. The second phase came with the design and construction of the airplane, following the choice of technologies and design solutions. This was a very focused and organized phase with constraints and planning requirements.

What are the main differences between your 1st prototype and the final plane?

AB: Mainly four things:

  • Firstly, we want improved performance, that is to say we want to reduce our energy consumption and have more reserves.
  • Then, we’re modifying the cockpit to improve ergonomics.
  • In addition, we need a more reliable aircraft with redundant safety systems and leak-proof electrical circuits in order to fly in humid conditions.
  • Finally, we will have a form of autopilot, that we call Stability Augmentation System (SAS) which will maintain flight altitude and a directional heading so that the pilot will be allowed to rest.

What does your typical day look like?

AB: At Solar Impulse the notion of a “typical day” doesn’t really exist. That’s why I love leading this project so much: every day is different and full of surprise and new things to learn!

Of course the main difference for us is whether we are on or off mission. On-mission periods are typically very hectic and a real endurance test for the whole team, whereas off-mission periods look more like typical office days. But even then, I get to move a lot and work with all the Solar Impulse teams which are separated into three units across Switzerland: the secretariat and communications team in Lausanne, the logistics and operations team in Payerne, and the engineering team in Dübendorf.

Typically, we are faced with very different tasks like managing external relations and communication, answering media enquiries, managing the technical team, working with the engineering team on everything related to interface between the pilot and aircraft, preparing flights (flight simulator, mock up tools etc.), coordinating our partners’ activities, and so on. All these activities can be part of our daily work and we often need to switch from one to the other in the same day.

How many engineers are working with Solar Impulse?

AB: It depends, there is no fixed number really. It mostly depends on the phases we are in. At the moment there are about 50 engineers and technicians in the workshop. On top of it we also have many partners’ contributions, also in terms of human resources.

What design and engineering tools do you use?

AB: Catia from Dassault System for CAD Design, Femap from Siemens for FEM analysis, Recurdyn from FunctionBay for mechanical simulations, Compolix from Even for EFM Post processing, Mathcad from PTC for math.

Larry Page of Google (right), André Borschberg and Bertrand Piccard with Solar Impulse
Pictured: Larry Page of Google (right), André Borschberg and Bertrand Piccard.

What is needed for a revolution in aviation?

BP: Our primary purpose is not to revolutionize aviation, but the way in which people think about energy and clean technologies. If Solar Impulse technologies were used on a massive scale, the world would be able to save up to 50% of the current consumption of fossil energy and produce half of the rest with renewable energies. As for the aviation industry, it is well aware of its need to change. However, this cannot be done quite as drastically as with Solar Impulse. Our project involves zero fuel. Conventional aviation cannot switch straight to zero fuel. Intermediate steps are needed, such as using lighter materials, more direct routes or approaching airports through constant descent rather than performing level landings. Aviation will be the final area of transport able to stop using fuel.

What does it take for the passenger aircrafts to start flying with solar power?

BP: Nowadays, solar drones can be used as telecommunications platforms at lower prices than satellites. We will surely see small solar seater planes, soon. However, we do not foresee solar-powered commercial aircraft in the near future, but we must remember the past anyway.

In 1903, when the Wright brothers succeeded in flying their airplane over a distance of 200m, could you imagine that 24 years later, Lindbergh would cross the Atlantic Ocean? He was alone on board and 30 years later airliners would carry 200 passengers, completing the same journey in eight hours while two men walked on the moon!

What are you working on at the moment?

AB: We have successfully completed our Across America mission flights: the prototype HB-SIA flew across America from May to July in several stages powered only by the sun.

We are currently focusing all our attention to finalize the development of the second HB-SIB plane. The aircraft is undergoing the same structural strength and vibration testing as for HB-SIA. Flight testing is planned for spring 2014, and the round-the-world flight for between April and July 2015.

How are you using the information gathered during the Across America flights?

AB: We systematically try to apply the lessons learned in our mission flights to all our future endeavors. But rather than testing the plane, what we do is draw conclusions to improve our operations. For example, the lessons learned from the Across America mission will be used to adapt flight tactics in strong wind situations, to use our inflatable mobile hangar, to optimize logistics for the team, to integrate the plane in heavy traffic areas, and so on.

Thank you to the Solar Impulse team! We are so glad that we had the chance to connect with the Solar Impulse team as they continue to bring awareness to the way people use energy and uses for clean technologies. In what ways does your company consider energy costs and savings? In what directions do you see clean technologies moving in the future? What companies would you like to see us interview in future Project Spotlights? Let us know in the comments.

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