Engineering news
Solar Impulse 2, the first-solar plane to be able to fly for several days and nights without fuel, has begun the first leg of its 22,000-mile flight around the world.
The plane, piloted by Solar Impulse founder Andre Borschberg, took off this morning from Monaco, and will continue on to its first destination Muscat, Oman, before crossing the Arabian Sea to Ahmedabad, India. Borschberg will swap piloting duties with Solar Impulse co-founder Bertrand Piccard during stop-overs.
The lightweight Solar Impulse 2 (Si2), a larger version of a single-seat prototype that first flew five years ago, is made of carbon fibre and weights just 2,300 kg – equivalent to a standard family car. The 17,248 solar cells built into its fuselage supply the sole power for the four electric motors (17.5hp each) that can take the plane to speeds between 30 and 60mph.
The plane has been enhanced in three areas compared with its predecessor: increasing the on-board energy resource, improving its robustness to cope with the extended flying periods and providing a cockpit environment that is tolerable for long distances.
Piccard said: “The plane has, therefore, been developed, to use the project’s own catchphrase, as a ‘flying laboratory’ to utilise a series of state-of-the-art technologies provided by and developed in cooperation with a series of industrial partners.” These have included SunPower for the solar cells and Kokam for the batteries. Specially designed brushless and sensorless 13.5kW electric motors have been made by Etel and turn the 4m diameter propellers at a maximum of 525rpm with an overall system efficiency of 94%.
In addition, they have ensured a more reliable aircraft with redundant safety systems and leak-proof electrical circuits in order to fly in humid conditions. Finally, a form of autopilot, called Stability Augmentation System, will maintain flight altitude and a directional heading so that the pilot will be allowed to rest.
Speaking to PE in January, Borschberg said: “Solar Impulse 2 is not about one revolutionary technology. It’s the mix of many solutions, the sum of all the efforts of our engineers supported by our partners that enable us to achieve the impossible.”
Piccard added: “What we are doing with Solar Impulse is clearly demonstrating the effectiveness of technologies that allow us to save energy and produce it from renewable energies. What we use for our airplane, you can also use.”
After Oman, the plane will head to India, where it will make two stops, then to China and Burma before heading across the Pacific and stopping in Hawaii. Then it will head to Phoenix, Arizona, and New York's biggest airport, John F Kennedy International. The path across the Atlantic will depend on the weather and could include a stop in southern Europe or Morocco before ending in Abu Dhabi. The two pilots are expected to return to Abu Dhabi in late July or even August.
The two pilots will be required to endure extreme conditions, living in a 3.8m3 non-pressurized cockpit, unheated, with external temperatures ranging from -40 to +40 degrees Celsius. Legs of the flights over the Pacific and Atlantic Oceans achieved in 5 days and 5 nights will mean that sleep will only be allowed in the form of short naps of up to 20 minutes 10-12 times, during which time the plane will use its autopilot Stability Augmentation System.