Solar Impulse

The Solar Impulse is a Swiss made long-range solar-powered aircraft project. It was developed at the École Polytechnique Fédérale de Lausanne. The project’s goal is to circle the Earth with a piloted fixed-wing aircraft, powered only by solar energy. Bertrand Piccard, a Swiss aeronaut leads the project who was a co-pilot with Andre Borsch berg a Swiss businessman, in the first balloon to circle the Earth non-stop.

The Swiss aircraft is a single-seat monoplane which can stay airborne for up to 36 hours and take off under its own power. Its first test flight was in December 2009. On July 7 – 8, 2010, it flew for 26 hours including 9 hours of night flying. Piccard and Borcschberg also flew from Switzerland to Spain and Morocco in 2012. In 2013 they conducted a successful multistage flight across the United States.

A planned flight of a larger re-designed aircraft was scheduled to circle the Earth in 20 to 25 days, but the 2014 mission was canceled due to a structural failure in 2012. A 2017 attempt is more likely to be considered. The flight will circle the Earth near the equator. Five stops are planned for the pilots to switch. Each flight will last three to four days depending on the pilots physical status.

The project began in November 2003 when Piccard did a feasibility study with the Ecole Polytechnique Federale de Lausanne. The concept was developed during  2004 – 2005. In 2006 simulations of long-haul flights were conducted. From 2006 to 2009 the first prototype was built (HB-SIA). From 2009 to 2011 manned test flights were conducted with the prototype. In 2011 – 2012 more test flights were conducted including a seven stop flight through Europe and North Africa. From 2011 to 2013 a second prototype was built (HB-SIB). In 2013 a successful flight across the continental US. Flight testing of the HB-SIB will be conducted in 2014 with an attempt of a multistage world flight in 2017.

The first prototype HB-SIA has a non-pressurized cockpit and has a limited flight ceiling. Under the customized carbon fibre honeycomb wing structure are four sets of lithium polymer batteries, a ten hp motor and a twin blade propeller. There are 11,628 solar cells on the upper wing surface to generate electricity during the day. This system keeps the aircraft aloft and batteries charged during the day giving it enough charge for night flying. In theory, the HB-SIA could stay airborne 24-hours a day.

Specifications for the HB-SIA:

The length of the aircraft is 71.7 feet, it has a wingspan of 208 feet, height is 21 feet and weighs 3,500 pounds. Cruising speed is 43 mph for up to 36 hours of flight at a height of 27,900 feet with a maximum of 39,000 feet.

The second prototype HB-SIB’s construction began in 2011 and was completed in 2013. It has a wingspan slightly larger than the HB-SIA at 262.5 feet and features a pressurized cockpit. It weighs a little more than the average automobile and has advanced avionics for transcontinental and trans-oceanic flights. Cruising altitude will be 39,000 feet.

Image Caption: HB-SIA on 3 December 2009 in Dübendorf. Credit: Matth1/Wikipedia (CC BY-SA 3.0, 2.5, 2.0, 1.0)