Solar Impulse Stays in Hawaii until Next Year

Dean Sigler Electric Powerplants, Sustainable Aviation Leave a Comment

A sign on the climb from Salem, Oregon to the Redmond/Bend area indicates that no gas or services exist for the next 52 miles.  It’s worth heeding, since the route goes over mountain passes, and in winter can require tire chains and sometimes long passages behind a snow plow.  Range anxiety happens even for those of us still plugging along in fossil-fueled vehicles.

One of the ostensible advantages of Solar Impulse’s ability to charge itself, is that it has an endless supply of solar fuel and its batteries can make it through the night – depending on the relative lengths of day and night.  Making the longest flight of the round-the-world trip at high latitudes and during summer months was well planned, subject only to obstacles presented by weather.  Even those impediments were handled brilliantly by the team’s meteorologists and mission director.

What couldn’t be foreseen and must have caused moments when Andre’ Borschberg’s discipline, yoga and powers of meditation were put to the extreme test, was the overheating of some of the batteries, reducing their performance and jeopardizing the mission – and Borschberg.

Since the first signs of trouble occurred on the first climb from Nagoya, Japan, that meant each day’s climb to 28,000 feet or more was a tenuous effort, many eyes doubtless scanning the instruments showing temperature and charge.  This was a courageous press onwards.

The team’s announcement postponing further flights this year reflects their disappointment, but adds an optimistic overtone typical of the entire program.

Despite the hard work of the Solar Impulse team to repair the batteries which overheated in the record breaking oceanic flight from Nagoya to Hawaii, the solar powered airplane of Bertrand Piccard and André Borschberg will stay in Hawaii until early spring 2016.

“Following the longest and most difficult leg of the round-the-world journey which lasted 5 days and 5 nights (117 hours and 52 minutes), Solar Impulse will undergo maintenance repairs on the batteries due to damages brought about by overheating.

“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 an over insulation of the gondolas. 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 and 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 quick ascent / descent 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 airplane 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 [to] the point of departure in Abu Dhabi.

“Solar Impulse is attempting a historic first of flying around the world only on solar energy. And while Solar Impulse has completed 8 legs, covering nearly half of the journey, setbacks are part of the challenges of a project which is pushing technological boundaries to the limits. Solar Impulse will try to complete the first ever round-the-world solar flight in 2016 and this delay will in no way influence the overall objectives of this pioneering endeavor.”

Despite the disappointment for all concerned that the flight will be postponed, a few good elements shine forth.  Borschberg and Piccard can attend the December COP21 climate conference in Paris as true heroes; perhaps eliciting more support for their Future is Clean initiative.

And, the lucky Solar Impulse team members remaining to work on the airplane will be wintering in Hawaii.  It’s all good.

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