SolarStratos, the solar airplane that dream of an altitude record

Science 10 December, 2016

The solar plane has to fly in the stratosphere has been unveiled. Next step: to ensure that the various embedded technologies work well to 24 kilometers altitude

He is there, behind a large curtain in an ice shed Aéropole Payerne: SolarStratos , the solar airplane that will go flirt with the stars flying in the stratosphere about 24 kilometers above our heads. “Time” was able to discover this unique aircraft in the world before its official presentation to the public on Wednesday, 7 December.

With its 24-meter wingspan and its slender line, SolarStratos has the look of a condor and exudes an impression of lightness. “It weighs about 350 kg empty,” says Raphaël Domjan, who will lead this beautiful toy two-seater to 5 million francs. A crossing of the United States from east to west aboard a solar car in 2008, before the first round the world on a solar boat, PlanetSolar, in 2012: eco-adventurer connects the first in fuel in the sun. And first, will be discussed with the plane: Raphaël Domjan aims to beat the altitude record for a manned solar aircraft, held since 2010 by the Solar Impulse André Borschberg with 9235 meters . Good player, it has slipped to “Time” that “all efforts are useful for (…) promote [new technologies for the aerospace sector], I welcome the work of the team of Raphael Domjan” .

But before snatch a medal in his illustrious big brother, SolarStratos still some details to polish. A test phase to start in February 2017 will determine whether this prototype manufactured by the German company PC-Aero is indeed capable of operating in the stratosphere, the second layer of the atmosphere in which the laws of physics can play tricks.

In the stratosphere, “it is certain death”

At about three times the height of Mount Everest, it’s cold: -60 ° C on average. And atmospheric pressure therein is not more than 5% of its value at the sea. Pressurize the cabin? “No, it would increase too much the plane,” said Raphaël Domjan, which will result in a spacesuit specially designed to provide heat and oxygen. Better to have confidence in his equipment to humans, get outside “beyond 19,000 meters is certain death,” he warns.

The pilot will be equipped with a space suit for heat and oxygen supply.
Another component that will be scrutinized in the coming months, the batteries will need to be reliable. We do not know how they will behave in the stratosphere. SolarStratos teams work with their Austrian provider to ensure proper function in low pressure. Same for all the electronics: “It is certified to operate down to -40 ° C, but not at -60 ° C. What will happen at that temperature? “Asks the driver.

20 kilos of solar panels
But technology SolarStratos queen, it is of course its solar panels. These commercial units of the American company Sunpower, which have an efficiency of around 24%. “They are assembled and sandwiched-between different materials to achieve very light and very reliable modules,” says Christophe Ballif, director of the photovoltaic sector in Swiss Center for Electronics and Microtechnology (CSEM) in Neuchâtel. These cells are so light that “everything SolarStratos embarks less than 20 kilos of solar panels,” notes Raphael Domjan. If similar signs to those used in the building had been used, it would have to multiply that weight by a factor of 12.

The plane could also help to better understand the physical phenomena that are played in the stratosphere.

The collaboration between CSEM and SolarStratos has been close since the encapsulation of cells and their integration in the wings were entrusted to the Neuchâtel institution. “We tested the operation of our modules for temperature ranges of -60 to + 90 ° C, said Christophe Ballif and their resistance to high UV radiation doses.”

The stratosphere, this new frontier
If all goes as planned, the stratospheric maiden flight could take place in 2018. Record or not, it would open the second phase of Raphael Domjan offer solar commercial flights at high altitude. But not with that aircraft, which is “a demonstration project” in the words of the adventurer. Are there really a market? The idea divides. Never mind, Raphael Domjan has the sequence of ideas: if human spaceflight do not, there is always the possibility of developing stratospheric solar drones.

Plans are in both study at Facebook, who would distribute Internet through such devices as the side of the Solar Impulse team. These could capitalize on their experience to develop solar drones loaded replace or support some lower-cost satellites. “The stratosphere is the next frontier for aeronautics,” says another source working in the industry.

Raphaël Domjan can also count on the support of Bertrand Piccard, the initiator of the Solar Impulse project. “Raphael is a friend for years. We always support in our respective projects. We both know that cleantech can accomplish incredible things. I am confident that by the age of 10, there will be electric aircraft capable of carrying 50 passengers for short haul flights means. And then all we are doing now look normal. I look forward to this moment. ”

In one part of the hangar in Payerne, a photo exhibition traces the adventure of solar, pioneers of the 1960s to the recent exploits of Bertrand Piccard and André Borschberg. No doubt Raphaël Domjan could see himself writing a new chapter in this story.