The long trip from Nagoya, Japan to Hawaii, taking 5 days and 5 nights has taken its toll on the 100% solar powered aircraft. The large batteries that are so essential to the functioning of the Swiss plane overheated on this flight and have suffered irreversible damage.
Despite the hard work of the Solar Impulse team to repair the batteries the solar powered airplane will stay in Hawaii until early spring 2016.
During the first ascent on day one of the flight from Nagoya to Hawaii, the battery temperature increased due to a high climb rate and over insulation. And while the Mission Team was monitoring this very closely during the flight, there was no way to decrease the temperature for the remaining duration as each daily cycle requires an ascent to 28,000 feet followed by descent for optimal energy management.
Overall the airplane performed very well during the flight. The damage to the batteries is not a technical failure or a weakness in the technology but rather an evaluation error in terms of the profile of the mission and the cooling design specifications of the batteries. The temperature of the batteries in a rapid ascent and descent scenario in tropical climates was not properly anticipated.
Irreversible damage to certain parts of the batteries will require repairs which will take several months. In parallel, the Solar Impulse engineering team will be studying various options for better cooling and heating processes for very long flights.
The University of Hawaii with the support of the Department of Transportation will host the plane in its hangar at Kalaeloa airport. Post maintenance check flights will start in 2016 to test the new battery heating and cooling systems. The round-the-world mission will resume early April from Hawaii to the USA West Coast. From there Solar Impulse will cross the USA to JFK in New York before making the Atlantic crossing to Europe and then returning the point of departure in Abu Dhabi.