Solar airplane

Nothing but sunshine in the tank

The sky above the Swiss town of Payerne is picture- postcard blue, and the sun shines brightly. July 7, 9:00 in the morning. The silence is almost complete. The only sound is the gentle hum of an engine that is slowly coming closer. A white airplane – light and delicate, almost like an oversized toy – appears before an impressive alpine backdrop. As it touches down on the runway of Payerne’s military airfield, the guests standing at the fence on the edge of the tarmac break into cheers.

Standing amidst them is Bertrand Piccard with a wide smile across his face. It’s an auspicious day for him, and the sun is a major reason for his good fortune. It plays the leading role in the dream that the Swiss adventurer and visionary is currently sharing with the entire world. Together with André Borschberg, a former military pilot and CEO of Solar Impulse, Piccard wants to fly around the world. With absolutely no fossil fuels. In an airplane that draws its energy exclusively from the sun and stores it as it flies. The successful 26-hour flight that Borschberg just completed at the controls of the solar airplane Solar Impulse HB-SIA is an important step on the way to the planned round-the-world flight.

A team with vision: Bertrand Piccard, test pilot Markus Scherdel and Solar Impulse CEO André Borschberg, who completed the first 26-hour flight

Piccard got the idea for the extraordinary project in 1999. At the time he was studying psychology and, at his third attempt, also copiloted a non-stop flight around the world in a hot air balloon. He started his flight with about four metric tons of liquid propane – and landed with just 40 kilograms. A fuel shortage could have meant the failure of his mission. “I therefore vowed that my next flight around the world would take place with no fuel and no emissions that are harmful to the environment,” says Piccard.

The aviation pioneer’s goal is to get people’s attention, force them to think and to permanently change their behavior with respect to renewable energies and clean technologies. “We want to show what can be achieved by using them,” explains Piccard. “If an airplane flies day and night without fuel, people can no longer claim that it’s impossible to use the same technologies for motor vehicles, heating or air conditioning systems and computers.”

solarimpulse ozellikler

Piccard comes from a famous family of adventurers. His father, Jacques, is considered an important pioneer of deep sea research. His grandfather, Auguste Piccard, was a physicist and an inventor as well as the first person to reach the stratosphere in a balloon.

Chances are good that grandson Bertrand will also make history. Solar Impulse HB-SIA, the first prototype of the novel airplane, was built between 2007 and 2008. Regular test flights have been taking place in western Switzerland since December 2009, while at the same time the airplane is being continuously optimized. Construction of a second prototype will begin shortly. The round-the-world flight is currently scheduled for 2013 and will comprise five stages, each lasting five days.

The final model will represent a completely new technology. Its fuel tank is the sun. More than 10,000 silicon solar cells mounted on the surfaces of the wings produce the electricity that powers the airplane and keeps it aloft. A portion of the energy generated during the day is stored in lithium-ion batteries so that the airplane can continue to fly throughout the night.

The solar energy is fed into four electric motors, each of which has a peak output of 10 hp. The solar plane has a ceiling of around 9,000 meters and can withstand temperatures between minus 45 and plus 80 degrees Celsius.

The pivotal element, however, is the airplane’s weight. The heavier it is, the more energy it uses. It’s no wonder, then, that everything possible is being done to reduce its weight.
In Bayer MaterialScience, Piccard and Borschberg have found a partner that is a leader in this field. “Our technology is crucial for the success of the project,” says engineer Johannes Seesing. The primary focus is on the use of innovative material solutions to reduce the airplane’s weight and energy consumption.

The company’s experts have been working since March 2010 to continuously reduce the weight of Solar Impulse through sophisticated technologies and innovative products. The goal is to trim an additional ten percent from the current version’s weight of 1,600 kilograms. The company’s contribution takes the form of comprehensive technical expertise, high-tech polymer materials and energy-saving lightweight products (cf. graphic on pages 38 and 39). Baytubes carbon nanotubes, in particular, could improve the strength of the structural components while enabling an extremely low weight. Seesing points out that the bar is set high. “Solar Impulse will have the wingspan of a jumbo jet while weighing hardly more than a mid-size car.” Never before has an airplane been built that is so large yet at the same time so light.

During the day, Solar Impulse will fly at an altitude of 9,000 meters to make optimal use of the sunshine. At night the airplane descends to around 1,500 meters, where it can fly very steadily with the minimum expenditure of energy because the lift is greater at higher air pressure.

Special vibration device to counter microsleep

Because the current model does not include an autopilot, aviation pioneer Borschberg had to stay awake for the entire 26-hour flight. If he had dozed off, a special vibrating device would have woken him. “André and I will use meditation and self-hypnosis during the round-the-world flight,” says Piccard. In the future, an autopilot will allow the pilots to rest for at least a short time.

There are still a lot of questions to answer before then, however. One idea being considered, for example, is to recycle urine into drinking water on board because liquid storage tanks would make the airplane too heavy. “Every kilogram that the plane carries uses energy,” explains Piccard.

“I am convinced that they will succeed,” says Seesing, the Bayer expert. “They will fly – and actually circle the world!” But sometimes it takes small steps to make big dreams come true. The adventurers’ next step will therefore be to cross the Atlantic.

Three questions for aviation pioneer Bertrand Piccard

Mr. Piccard, what is driving you to build the Solar Impulse?
I want to make people more interested in the use of environmentally friendly technologies, with the airplane being just one example. We could reduce our petroleum consumption by as much as 50 percent today by using these technologies in a variety of areas. Without changing our lifestyle.

What are the main considerations for the design of the airplane?
Primarily the weight. Every kilo that the plane carries uses energy. The lighter the plane is, the less energy it has to use. This is a challenge, and our greatest goal is to reduce the weight of the second prototype even further.

And you need the right partner to do this?
Yes, we have brought together a whole family of partners, all of whom share the pioneering spirit of the project. They guarantee its feasibility and are dedicated to the advancement of renewable energies. We expect the high-tech materials and energy-saving lightweight products from Bayer MaterialScience to shave 160 kilos off the weight.