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Solar Impulse 2, the
#RTW Solar Airplane

Solar Impulse is the only airplane of perpetual endurance, able to fly day and night on solar power, without a drop of fuel.


The chances of succeeding at the first attempt to build a solar airplane capable of flying around the world were judged to be slim, so a more rudimentary prototype, HB-SIA, was first constructed. Lessons learned from this prototype are incorporated in Solar Impulse 2, the Round-The-World Solar Airplane.


This revolutionary single-seater aircraft made of carbon fiber has a 72 meter wingspan (larger than that of the Boeing 747-8I) for a weight of just 2,300 Kg, equivalent to that of a car.

The 17,000 solar cells built into the wing supply four electric motors (17.5 CV each) with renewable energy.

During the day, the solar cells recharge lithium batteries weighing 633 Kg (2077 lbs.) which allow the aircraft to fly at night and therefore to have virtually unlimited autonomy.

Learn more about the challenges of building the Round-the-World Solar Airplane.


Whereas the prototype uses existing technologies, Solar Impulse HB-SIB requires the development of new materials and new construction methods. Solvay has invented electrolytes that allow the energy density of the batteries to be increased; Bayer MaterialScience is allowing the project to make use of its nanotechnologies; and Décision is using carbon fibers that are lighter in weight than any previously seen.

The first wing spar section was delivered to Dübendorf in March 2012. However, during the final test of this central part, the structure of the wing spar succumbed to the load and broke. The initial shock soon turned out to be an opportunity: the flight around the world had to be postponed which opened the door for going to the United States and completing the epic journey across America.

After the official presentation of Solar Impulse 2 to the public on April 9th, flight testing is planned for spring 2014, and the round-the-world flight for between April and July 2015.

Technical Datasheet

Solar Impulse 2's features, in short:

  • Batteries energy density 4 x 260 Wh/kg
  • Airplane Weight 2,3 tons
  • Wingspan 72 meter (236')
  • Solar Cells Thickness 135 micron
  • Solar Cells > 17,000
  • Cockpit Size 3.8 m3


1. A unique opportunity to ask your questions to the pilots below or tweet @solarimpulse, hashtag #DiscoverSi2.
2. Select the best questions by clicking the "^" sign, we will ask them to the pilots.


In 2015, Solar Impulse 2 will attempt the First Round-The-World Solar Flight.
The First #Challenge will be to fly day and night without fuel, up to 7 days in a row.

  • Zero-Fuel
  • Autonomy
  • Batteries
  • Aerodynamism
  • Fly Non-Stop
  • Solar Cells
  • Energy Efficiency
  • Lightweight Structure
  • Perpetual Flight



Can you imagine yourself doing what our pilots are set to do for the Round-The-World Solar flights? Would you see yourself in an unheated and unpressurized 3.8 m3 cockpit, on your own for - not 12 hours - but 5 whole days?

  • Long-haul flights
  • living in a cockpit
  • no heating
  • unpressurized
  • 5days-5nights
  • energy saving
  • focus

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