Beijing, May 25 (IANS): Solar Impulse (Si2), the solar plane on a mission to fly around the globe without a drop of fuel, is all set for a challenging 8,000-km journey on Tuesday, flying non-stop from Nanjing in China to Hawaii in the central Pacific, a media report said on Monday.

For Si2, which is powered by more than 17,000 solar cells installed on its 72-metre wings, it will be its greatest challenge yet, BBC reported, adding the experimental aircraft could take five-six days and nights of continuous flight to reach its destination.

So far, Si2's flights were restricted to about 20 hours' maximum duration. The aircraft, which is on a mission to promote clean technologies, left Abu Dhabi on March 9 to complete the first leg of its journey to Muscat in Oman. The second leg of the journey brought it to India, from where it travelled to Myanmar and then to China in the next four legs of its journey around the world.

"It's more in the end about myself; it's going to be an inner voyage," said Swiss entrepreneur and engineer Andre Borschberg on the longest-duration journey Si2 will undertake from Nanjing.

"It's going to be a discovery about how I feel and how I sustain myself during these five or six days in the air," Borschberg was quoted as saying.

The plan is to fly high during the day, up at 28,000 feet, in order to capture energy, and at night the 62-year-old pilot will descend to no lower than 3,000 feet, conserving as much energy as possible.

It will be important that the four lithium-ion batteries powering Si2 are recharged fully during the day. "Even with 100 percent charge, by the next morning we would have only 10 percent or maybe 7 percent. So, if we go into the night with 90 percent charge, we are at zero the next morning," mission director Raymond Clerc said.

A team in the project control room in Monaco will be constantly anlysing the latest weather reports to help the plane find the optimum route.

Co-pilot Bertrand Piccard will take over the plane for the Hawaii-to-Phoenix leg.