Circling the globe on the power of the sun: Solar Impulse II ready to leave Honolulu

There’s so much going on in the solar world, but the concept of flying around the world in a plane powered by solar cells is one step beyond.

Hawai`i has some solar flying cred. (Image, the Helios flying wing off Kaua`i. Credit: NASA.)

AeroVironment’s  solar plane Helios flew off Kaua`i’s Pacific Missile Range Facility early in the last decade. Ultimately, the experimental unmanned aircraft crashed in June 2003 in rough weather, but not until it had set some records, including a world record altitude in 2001 for non-rocket-powered flight.

The Helios flying wing reached 96,863 feet on the back of some solar cells and propellers.

Its other mission was to prove that solar planes could fly continuously, using fuel cells to store energy during the day, which could be used to power the plane at night.

(Image: Solar Impulse II over Hawai`i. Credit: Solar Impulse.)

It was Solar Impulse I that accomplished that goal in 2010, staying aloft for 26 hours.

That was then. Today, another solar aircraft, Solar Impulse II is parked in Honolulu, ready for the next leg of its flight around the world. That mission was delayed last year when its flight across the western Pacific damaged some of its batteries.

Solar Impulse II is an idea 15 or more years old, and in some ways it is a descendant of the Helios. While Helios was flying, back in 2002, Solar Impulse pilot Bertrand Piccard consulted with AeroVironment’s late Paul McCready, one of the visionaries in solar-powered flight.

The new Solar Impulse, completed in 2014, is a feather-light but gangly aircraft, with honeycombed wings that stretch 236 feet tip to tip. Its upper surfaces are covered by photovoltaic cells. It has four electric motors powering four propellers, each powered by lithium-ion batteries.

Looks a bit like a giant dragonfly.

SI II launched on its global tour in 2015 from Abu Dhabi. Pilots Piccard and André Borschberg took turns flying the one-seat aircraft. They crossed Asia, hopping to stops in Oman, India, Myanmar, China and finally Japan, and then made their longest flight, from Japan to Hawai`i, last year.

The Japan-Hawai`i leg was the world’s longest-ever solar-powered flight. Pilot Borschberg stayed aloft 8 minutes short of 118 hours. But in doing so, his batteries overheated and were damaged, requiring replacement. That, and weather, kept SI II grounded on O`ahu for most of a year.

But the organizers say they are days from a new liftoff, aimed at crossing the rest of the Pacific and then continuing around the world, back to their Abu Dhabi starting point. The remaining flights are expected to all be shorter than the Japan-Hawai`i marathon of five days aloft.

The eastern Pacific flight's conclusion will be determined by wind or weather.  The plane could land anywhere up or down the West Coast, or as far inland as Arizona.

SI II, in anticipation of taking off in mid-April, performed several takeoffs, extended flights and landings in late March from the runway at Kalaeloa with Piccard at the controls.

In a blog post, Piccard wrote: “It was beautiful to fly #Si2 under the full moon tonight and I really enjoyed it. I even flew with the window open to feel the night breeze. My second

landing was the best: a kiss landing. We call it like that because the plane touches down so smoothly that you can barely feel it.”

Here is a YouTube video on the mission. Here is the Solar Impulse website. The mission is to send the world a message about the potential of clean fuels. Here is their clean fuels website.

You can subscribe to get updates on the voyage here. The most recent information we have is that it should leave within two weeks.

When the Solar Impulse II does take off for its long voyage to the northeast, it will pass over hundreds of Hawaiian rooftops outfitted with the same technology that is keeping this plucky airborne adventurer aloft.

© Jan TenBruggencate 2016