The first successful day-and-night flight of a manned prototype solar-powered aircraft, “Solar Impulse HB-SIA” (www.solarimpulse.com), piloted by Swiss native André Borschberg, touched down safely in Switzerland on the morning of 8 July. “I have flown more than 26 hours without using a drop of fuel and without causing any pollution,” exclaimed an exhilarated Borschberg. The spectacular first made headlines worldwide, but what most reports mentioned only briefly was that the flight of a solar airplane, like solar energy in general, would not be possible without innovative, high-tech plastics.

Two leading European plastics producers are at the forefront of the Solar Impulse project being developed by Borschberg and his partner, initiator and president, Bertrand Piccard, also a Swiss native, who once circled the earth in a balloon. Solvay (Brussels / Belgium; www.solvay.com), designated a “main” partner, joined the project in 2004, at an early stage. Bayer MaterialScience (Leverkusen / Germany; www.bayerbms.com), an “official” partner, just recently came on board. Innovation consulting firm Altran (Brussels / Belgium; www.altran.com) is also an official engineering partner. Other main partners are Germany’s Deutsche Bank and Swiss watchmaker Omega.

The ultimate plan of the Solar Impulse project is to develop an aircraft that can fly around the world day and night, propelled solely by solar energy. The HB-SIA has a wingspan similar to that of the Airbus A340 (63.4 metres) and the weight of a mid-sized car (1,600 kg). Around 1,200 solar cells cover its surface to propel four electrical engines and store the solar energy for the night flight in 400 kg of lithium batteries. The next important milestone on the way to a worldwide journey will be crossing the Atlantic Ocean in a second prototype, which is just going into construction.

As a main partner, Solvay is supporting the Solar Impulse project financially as well as supplying technological solutions and materials. More than 6,000 of the parts contain materials from Solvay Advanced Polymers (Alpharetta, Georgia / USA; www.solvayadvancedpolymers.com), Solvay Solexis (Bollate / Italy; www.solvaysolexis.com) and Solvay Fluor (Hanover / Germany; www.solvay-fluor.com), the company says.

Along with helping the project coordinators select the best thermal insulation materials, the Belgian group’s effort is focused on finding the right composite materials and high-performance plastics for metal replacement, as well as polymers for critical applications such as watertight joints or lubrication. Solvay is also looking for methods of encapsulating and assembling photovoltaic cells using the structural material selected for the plane as well as producing photovoltaic materials and the mechanical evaluation and testing of materials under extreme conditions.

Bayer MaterialScience is supporting the Swiss initiative with its technical expertise, high performance engineering polymers and energy-saving lightweight products. A lightweight PU foam moulded by Puren (Überlingen / Germany; www.puren.eu) from starting materials supplied by BMS was incorporated into the cockpit cladding, engine cowling and the wings of the HB-SIA. Thin but strong sheets of BMS Makrofol polycarbonate film are used in the cockpit windows.

The Leverkusen group says the next prototype solar aircraft will contain a significantly greater proportion of its products. It is currently working flat out on developing additional lightweight materials, such as the Baytubes carbon nanotubes, which it believes could improve the strength of structural components while minimising weight. The Swiss partners say they are especially enthusiastic about the prospects of using carbon nanotubes in the plane.