While many of us were asleep, the Solar Impulse 2 completed a successful maiden flight, after having been unveiled on April 9th. Flown by German test pilot Markus Scherdel, the solar-powered plane departed from Payerne Airport in Switzerland at 5:30AM and landed at 7:50AM local time.
Solar Impulse 2 has a wingspan of 236 feet - slightly larger than the first Solar Impulse plane at 208 feet, and larger than a Boeing 747-8i. However, the SI2 only weights about 1 percent of the 747. With a structure made of composite materials and wings covered in sheets of wound carbon fiber, it's truly the most energy efficient plane ever made, outside of an engineless glider. The wings, fuselage and horizontal stabilizer are covered in 17,248 solar cells, at 135 microns thick, which provide energy to the plane's four engines.
Lithium polymer batteries power the four 17.4hp engines, weighing a total of 1,395 pounds, make up a quarter of the plane's total weight. The two-bladed propellers spin at 525rpm. The system is 94 percent efficient.
26 knots is all the speed it takes to get the Solar Impulse 2 airborne, using roughly 500 feet of runway. It can cruise up to 27,000 feet at speeds ranging from 31.5 to 77 knots. At sea level, it only has to fly at 20 knots to remain airborne.
Solar Impulse pilot, co-founder and CEO Andre Borschberg said:
"Imagine energy reserves increasing during flight! To make this dream a reality, we had to make maximum use of every single watt supplied by the sun, and store it in our batteries. We tracked down every possible source of energy efficiency. Today, Solar Impulse is the first solar airplane flying through night and day, the first aircraft to come close to perpetual flight."
Map of Solar Impulse 2's first flight. [solarimpulse.com]
Solar Impulse 2 unveiling video
Indeed, the solar plane does fly at night. On May 23rd of last year, I witnessed the Solar Impulse 1 land at DFW Airport at around 2:00AM, the second stop on its tour across America. Pilot and Solar Impulse CEO Andre Borschberg described that landing as "extremely difficult and very windy" having to approach the airport in a sideways, crab-like motion in order to attain enough ground speed.
Overall, the program has spent 12 years in development, with the ultimate goal of completing a round-the-world flight with no traditional fuel in 2015. The flight is expected to take 500 hours, hence the biggest challenge in developing the plane — how to build a cockpit that will support a pilot for 5 or 6 days at a time. The SI2 cockpit measures only 3.8 cubic meters, and has to house the pilot, food and water for up to a week, a life raft, a parachute, and oxygen bottles. When I met with Borschberg at DFW last year, he said the flight length capability of the plane was really only limited by the endurance of the pilots.
One could easily expect boredom to be a a factor, flying for five or six days at the speed of a car, with no stops to stretch your legs! I can't decide whether to be envious of the pilot or not. Solar Impulse says the pilots will use self-hypnosis and meditation to help maintain concentration and vigilance. A long flight like this sounds a bit torturous, but the end result is setting records for flight endurance and distance-flown on solar power, which is pretty incredible.
Top image & all stats via solarimpulse.com