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Photovoltaics/Aircraft 060217
Sun-powered Aircraft to make round the world flight in 2010
by Shirley Georgi

Adobe Photoshop ImageThis is a visual representation  of the Solar Impulse, a single-pilot aircraft, which is being  designed and built to fly around the world, powered only by solar energy with batteries storing  solar energy during daylight hours for use  during night time flight.  (The artist concept of the plane  is credited to  Oxyde. de-Sapristi / EPFL -Solar Impulse and to the  European Space Agency.)

Bertrand Piccard, a well-known Swiss adventure, is constructing a solar-powered plane and hopes to circumnavigate the globe in 2010.  He and his team members have a goal to complete this flight and promote sustainable development and renewable forms of energy.

The European Space Agency (ESA) through its Technology Transfer Programme is assisting Mr. Piccard and his crew by providing technological expertise.  The Swiss Federal Institute of Technology in Lausanne is the Official Scientific Advisor for the project.  

During 2006 and 2007, the work will revolve around detailed design and assembly of the plane.  By 2008, the first test flights and night flights will be conducted so that by 2009, solar flights of several days duration can take place.  All of this in preparation for 2010 when the plane will circle the globe.

The trip around the world will take place in five stages. Each stage will last three to five days, traveling from west to east.  Because of the prevailing winds and sunlight, the flight path will be mapped between  100 to 300 north of the equator.   Altitude is projected to be between 10,000 and 11,000 meters.  

Three pilots will fly the plane.  Bertrand Piccard, President and initiator of the project; Brian Jones, manager of the sustainable development programme; and Andre Borschberg, Solar Impulse’s Chief Executive Officer.   

The plane itself is lightweight and weighs about  two tons.  It has an 80 meter wide wingspan; the 250 square meters of the wings’ upper surface will be coated with solar panels to power the aircraft . Two propeller engines will utilize that power to  provide about 40 horsepower of thrust to propel the plane along at about 100 kilometers (62) miles per hour.

The batteries  weigh about 400 kilos (880 pounds)  and store excess electricity generated during the day.  At night, all of the stored energy will be used.  Because this  stored battery energy may not be enough to power the plane during all night time hours at a steady altitude, the aircraft will climb to 10,000 meters during the day and  by gliding down to 3,000 meters during the night,   less energy will be used.  To date, the chemistry of the batteries is not known. (BD note: Lithium-ion may be considered.)  

Perhaps some  of the biggest technological gains from the construction of this plane and flight itself will be in research for improved gains in solar panel efficiency and energy storage.  Exploring lighter materials and unique configurations  for batteries might also  help make the design more compact with less weight.  

The cost of the project is  euro 40 million.  Partners supporting the project are Solvay, Dassault Aviation, Altran Technologies and as already stated, the European Space Agency (ESA).  

For more information, see the Solar Impulse and ESA websites.
 Thin-film Solar Cells for the High-altitude Airship
The Air Force Research Laboratory is furthering the adaptation of thin-film cells from terrestrial to space-based applications. Cells have been converted from rigid substrates such as glass to flexible, lightweight substrates such as stainless steel and polymer foils. For aerospace applications, the cells must be able to withstand the environment and have increased efficiency in the  blue-light-rich part of the spectrum. The cells are anticipated to have superior power, better weight and volume characteristics, increased radiation resistance and cost advantages.
AFRL Technology Horizons,
Aug. 2005, p. 48

A visionary project is being proposed to build a flapping wing airplane which will be solar powered. To utilize the limited electricity which can be obtained per unit of area, a very high efficiency device must be used. The flapping wing concept, proposed by the University of Missouri, at Rolla will have wings which mimic the actions of bird wings with  up-down motion and shape morphing to provide optimal performance in climbing, cruising or gliding. The implementation of mechanics will be accomplished with artificial muscle power using plastics which flex when electrically stimulated. NASA is currently funding the development of the wings.
Business Week, May 17, 2004, p 66
Adobe Photoshop Image
(July 2003)  NASA’s Helios, an unmanned prototype, solar electric propeller driven, world record-setting aircraft crashed in Pacific on June 28th. The aircraft was testing an advanced experimental fuel cell system to prepare for a two day mission planned for next month.

The Helios crashed about thity minutesafter takeff near the U.S. Navy’s Pacific Missle Range Facility off the coast of the Hawaiian island of Kauai.   The aircraft began to break apart at an elevation of 3,000 ft.

The $15 million dollar, nonrocket, winged aircraft set an aviation record in August 2001, soaring to a height of 96,863 feet, approximately three times higher than commercial jet flights.  The Helios project was being considered a potential alternative to orbiting satellites; it was designed so as to remain in a stationary spot over the Earth’s surface for an expanded time period.    

The cause of the crash of the plane is unknown as of this date.  Thomas E. Noll of NASA’s Langley Research Center will be in charge of the investigation.

The Helios was built and operated by AeroVironment in Monrovia, California.