By Steve Gorman
(Reuters) - A solar-powered plane halfway through an attempt to circle the globe will be grounded in Hawaii for at least nine months because of battery damage sustained during its record 118-hour flight to Oahu from Japan, the project team said on Wednesday.
The spindly, single-seat experimental aircraft dubbed Solar Impulse is not expected to take off on the next leg of its journey - a planned four-day, four-night flight to Phoenix, Arizona - until late April or early May 2016, the team said.
Additional time is needed to repair the plane's four batteries, which store energy from the sun during daylight hours to keep the aircraft powered overnight, allowing it to remain aloft around the clock on extreme long-distance flights.
The repairs and testing will then push the next available window for completing the plane's trans-Pacific crossing to next spring, in terms of both weather conditions and sufficient hours of daylight.
The batteries became overheated during the aircraft's initial climb after takeoff on June 29 from Nagoya, Japan, en route to Hawaii on the eighth and most challenging leg of the circumnavigation quest, officials for the mission team said.
The team stressed in a statement that the damage was "not a technical failure or weakness in the technology." Instead, flight managers had miscalculated the temperature increases the plane would experience, and the appropriate amount of insulation required, for the tropical climate encountered on ascent.
Still, the pilot, Swiss aviator Andre Borschberg, and his team successfully completed the Japan-to-Hawaii leg, safely landing near Honolulu on July 3 after five days and five nights, or 117 hours and 52 minutes, airborne.
The trip shattered the 76-hour world duration record for a nonstop, solo flight set in 2006 by the late American adventurer Steve Fossett in his Virgin Atlantic Global Flyer. It also set new duration and distance records for solar-powered flight.
Borschberg and co-founder of the project, fellow Swiss pilot Bertrand Piccard, are aiming to achieve the first round-the-world solar-powered flight, alternating turns at the controls for each leg of the voyage.
The aircraft, about as heavy as a minivan, is propelled by energy collected from 17,000 solar cells that simultaneously recharge the batteries.
The aircraft cruises at an altitude of roughly 28,000 feet (8,500 m) at speeds of 30 to 60 miles (48 to 97 km) an hour. Meditation and hypnosis were part of the pilots' training. They also practice yoga and take 20-minute naps every three hours on extremely long flights.
The team hopes to end its feat in Abu Dhabi, where they started on March 9.
(Reporting by Steve Gorman; Editing by Ken Wills)