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  • Solar Impulse Simulates 72-Hour Flight
    Posted by Graham Warwick 3:40 PM on Feb 20, 2012

    As a precusor to a round-the-world flight attempt, Switzerland's Solar Impulse will simulate a non-stop three-day flight of its second solar-powered aircraft, HB-SIB, from Feb. 21 to 24. The test will use a full-scale mockup of the cockpit, and pilot Andre Borschberg will remain at the controls throughout the 72-hour "flight".

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    HB-SIB (Concept: Solar Impulse)

    Borschberg and Bertrand Piccard will take turns flying HB-SIB on its 20- to 25-day round-the-world flight, planned for 2014, and the aircraft has a more spacious cockpit than the first prototype, HB-SIA, in which Borschberg completed a 26-hour through-the-night flight in July 2010. The test will assess the demands of long-duration flight.

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    HB-SIA. (Photo: Solar Impulse)

    The slow-flying Solar Impulse will be in the air far longer than previous round-the-world flights. Dick Rutan and Jeana Yeager were aloft for 9 days in the Rutan Voyager in 1986, and Steve Fossett for just 67 hours in the Virgin Atlantic GlobalFlyer in 2005. Even the Breitling Orbiter 3, in which Piccard and Brian Jones completed the first round-the-world ballon flight in 1999, took just under 20 days.

    Monitoring pilot fatigue will be a key part of the simulated flight. Solar Impulse says the ergonomically optimized cockpit includes a seat designed by Lantal to allow the pilot to shift positions "for various reasons, including attending to calls of nature." Piccard and Borschberg will use individualized nutrition plans and rest strategies to control fatigue, the team says.

    Construction of the second aircraft is under way, meanwhile. In a bid to minimize weight, Solar Impulse is using composite technology developed for yacht sails. Using "thin ply technology" invented in Switzerland and developed by North Marine Group, the team says it has been able to lay down carbonfiber layers with a density of just 25g/m2. This compares with 90g/m2 for composites used in HB-SIA (and 80g/m2 for paper, the team points out).

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    Wing spar tool. (Photo: Solar Impulse)

    Thin ply technology uses carbon nanotubes to reinforce the epoxy matrix and provide increased strength at lower weight, Solar Impulse says. The thin layers making up the carbonfiber laminate are precisely positioned by robot. Construction of the wing spar for HB-SIB, which will be more than 70m long when assembled, is now under way.

    Tags: awt, propulsion

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