The Solar Impulse 2 Begins Crossing North America


The Solar Impulse 2 Begins Crossing North America

Barbara Mohr | - 05/12/2016
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© Solar Impulse

The highly publicized, first-ever, solar-powered, manned flight around the world undertaken in the Solar Impulse 2 has just begun its multi-leg navigation of the North American continent across the United States. On May 2, the plane took off from San Francisco, California and headed for Phoenix, Arizona, some 720 miles (1,159 km) away.

The Solar Impulse 2 (Si2) team has two pilots, Swiss aviators Andre Borschberg and Bertrand Piccard, who alternate time in the single-pilot cockpit. The aircraft lifted off from San Francisco at 05:03 PDT local time (12:03 UTC) with Borschberg at the helm, expecting to arrive in Phoenix 16 hours and 23 minutes later.

This epic flight originated March 9, 2015, in Abu Dhabi, UAE where Borschberg flew for 13 hours, landing in Muscat, Oman. Next, the team navigated across Asia, visiting India, Myanmar, and China before crossing to Japan. On June 28, 2015, Borschberg then embarked on a four-day, 21-hour, and 52-minute flight from Nagoya, Japan to Honolulu, Hawaii, which was also the longest, non-stop solo flight on record.

This grueling leg, with the brutally high tropical temperatures, damaged the aircraft’s batteries to the extent that the team postponed the rest of the flight until April 2016. This break during the winter months allowed the damaged batteries to be properly repaired and the days to become longer with increased sunlight for the solar cells.

During daylight hours, the aircraft ascends to 27,878 feet (8,500 meters) where it stores the maximum amount of solar power in its batteries and assumes its top airspeed of 56 mph (90 km/h). At dusk, it descends to 4,750 feet (1,500 meters), runs on stored energy from the batteries, and slows to about 28 mph (45 km/h) in order to stay aloft more easily.

All totaled, the aircraft will travel nearly 22,000 miles (35,405 km) using no fuel and expel zero emissions. The fuselage is constructed of a light-weight carbon fiber. The aircraft has 17,000 solar cells blanketing the wing and tail spans. The cells supply four charge lithium batteries, which in turn power four electric motors.

Each motor is attached to a two-blade propeller that maintains 525 revolutions per minute. The entire system achieves an impressive, record-setting, 94-percent efficiency rate. At a massive 360 feet (110 meters) long, the wingspan is 236 feet (72 meters), which is wider than the Boeing 747. The aircraft is built ten times lighter that the lightest glider and weighs just a mere 5,070 pounds (2,300 kg), which is comparable to a small van.

So far, these are the world records set by Si2:

  • Flight time: 117:52 hours
  • Maximum altitude: 28,000 feet (8,634 meters)
  • Flight plan distance: 4,481 miles (7,212 km)

The journey is intended to promote the use of clean technologies and demonstrate that the impossible is achievable. On the official website,, the message is clear:

“…everybody could use the plane’s technologies on the ground to halve our world’s energy consumption, save natural resources and improve our quality of life. This message is being spread by the pilots to the general public, students, key decision-makers and entrepreneurs all over the world.”

From Phoenix, the plane will fly to New York City – with possibly an additional stop or two along the way – before continuing across the Atlantic, the Mediterranean Sea, and back to Abu Dhabi.

For updates on this story, The UAS Blog will have latest developments.