By Will Nichols, Source: Business Green

Solar Impulse flight Across America over the Golden Gate bridge – photo J. Revillard

A pioneering solar-powered plane touched down in Washington D.C. on Tuesday, completing a record-breaking journey across the continental United States and offering a glimpse into a zero-emissions future for aviation.

Strong winds had forced the Swiss-built Solar Impulse into a brief unscheduled stop at Cincinnati on Saturday night during the flight between St Louis and Washington. But, not to be deterred, pilot Bertrand Piccard pressed on and landed at Dulles International Airport at 12.15 on Sunday morning, over a month after the plane first set out from San Francisco.

On its journey the Solar Impulse stopped at Phoenix, Dallas, and St Louis, as well as the pit stop at Cincinnati. The plane will now go on limited display at the Smithsonian’s Steven F Udvar-Hazy air and space museum, before the team makes the final flight to New York early next month.

The journey, which reportedly cost around £73m and has been 10 years in the planning, has certainly not been about speed – the plane travels at a 50mph under full power – but is designed to show the potential for solar-powered transport.

Prior to the mission to cross the US, the pioneering plane has clocked up journeys across Europe and into Africa, as well as several flights throughout the day and night. The next goal is to circumnavigate the globe in 2015.

“What we are doing with the Solar Impulse is not for the goal of making a revolution in air transport,” Piccard said yesterday. “But the Solar Impulse does have a goal of having a revolution in the mind-set of the people.”

The plane is covered by around 12,000 PV cells that power 400kg worth of batteries, allowing a cruising speed of around 40mph. On clear days, the pilot will guide the Solar Impulse up to heights of 8,500 metres and let it glide slowly downwards to save power.

Its 64 metre wings are the same length as a Boeing 747-400, but the Solar Impulse only weighs as much as a medium-sized car, which can cause problems in high winds. André Borschberg, who takes turns with Piccard to pilot the one-seater Solar Impulse, admitted he had problems landing in Dallas when strong headwinds actually pushed the plane backwards.

However, Borschberg expressed confidence the weather issues faced durign the trip would set the Solar Impulse in good stead for the 2015 round the world attempt.

“With the successful completion of these last four US flights, we have shown that we are capable of coping with challenging meteorological conditions for our weather-sensitive plane and for our ground operations, and that we could find each time the right solutions to move forward,” he said in a statement. “It has been a succession of fruitful learnings preparing us for the 2015 world tour.”