The first night flight of a solar-powered craft in 2010 was followed by a first international flight in 2011, and first inter-continental flight in 2012.

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Speaking of sun-powered planes, the Solar Impulse just made its final test flight around the San Francisco Bay Area before embarking on a cross-country voyage next week.

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Switzerland is home to several renewable energy projects, including the most advanced solar-powered aircraft, the Solar Impulse, which made its first international flight less than two weeks ago.

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Using solar power, "we are close to the notion of perpetual flight, " he said.

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Since joining NASA in 1988 at the Marshall Space Flight Center in Huntsville, Alabama, she has conducted research for a variety of solar missions.

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Adding flight time to the craft is a matter of choosing longer wings that can hold more solar panels.

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And last year, defence firm Qinetiq flew a solar-powered plane for 54 hours, smashing the official world record for the longest-duration unmanned flight.

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While putting money into renewed human space flight efforts, the proposal cuts scientific research, particularly the study of the other planets in our solar system.

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