Solar Impulse 2 airplane

Solar Impulse 2 is the only airplane of perpetual endurance, able to fly day and night on solar power

2/20/15 4:00 am chumakdenis 1

The chances of succeeding at the first attempt to build a solar airplane capable of flying around the world were judged to be slim,but engineers from Solar impulse did it - first solar-powered prototype HB-SIA was constructed.

Now engineers came up with an advanced version of Solar Impulse (Solar Impulse 2) that features a series of improvemets.








The airplane is said to be  able to fly day and night on solar power, without a drop of fuel.

Solar Impulse 2







This single-seater aircraft is made of carbon fiber and has a 72 meter wingspan(larger than that of the Boeing 747-8I).It also weights only  2,300 Kg and has 17,000 solar cells built into the wing supply four electric motors (17.5 CV each) with renewable energy.

During the day, the solar cells recharge lithium batteries weighing 633 Kg (2077 lbs.) which allow the aircraft to fly at night and therefore to have virtually unlimited autonomy.

Sounds cool, isn't it? But one major question remains unanswered: how does this all-electric airplane can fly through 5 consecutive days and nights without using any fuel?

Well, don't expect to hear a simple answer on that one.This required a bunch of highly innovative solutions from engineers and technicians.

Technical challenge №1 - not enough energy to cross so big distances

Solution: more powerful batteries and solar cells

Solar cells









More than 17’000 solar cells, collecting up to 340kWh of solar energy per day and representing 269.5 m square.

More precisely 17'248 monocrystalline silicon cells each 135 microns thick mounted on the wings, fuselage and horizontal tailplane, providing the best compromise between lightness, flexibility and efficiency (23%)

In order to maximize the aerodynamical performance, the plane is built with a wingspan of 72m: wider than that of a Boeing 747 Jumbo jet.









The energy collected by the solar cells is stored in lithium polymer batteries, whose energy density is optimized to 260 Wh / kg. The batteries are insulated by high-density foam and mounted in the four engine nacelles, with a system to control charging thresholds and temperature. Their total mass amounts to 633 kg, or just over a quarter of the aircraft’s all-up weight.

In order to save energy, the aircraft climbs to 8’500 m during the day and descents to 1,500 m at night.

Technical challenge №2 - not enough power to fly over 35,000 km (22,000 miles)

Solution: composite materials such as carbon fibre and honeycomb sandwich.









Average power over 24-hour of a small motorbike (15 hp) with a maximum power of 70 hp (four 17.5 hp engines).

Four brushless, sensorless motors, each generating 17.4 hp (13.5 k), mounted below the wings, and fitted with a reduction gear limiting the rotation speed of a 4 m diameter, two-bladed propeller to 525 rev / min. The entire system is 94% efficient, setting a record for energy efficiency.


Solar Impulse can fly at the same speed than a car, between 36 km/h (20 Kts) and 140 km/h (77 Kts).

At sea level: minimum speed of 45 km/h (20 Kts) and maximum speed of 90 km/h (49 Kts).
At maximum altitude: from 57 km/h (31,5 Kts) to 140 km/h (77 Kts).

Technical challenge №3- airplane weighted too much

Solution: powerful motors

Light as a feather








Prowess of the engineers led by André Borschberg who managed to build the entire structure proportionately 10 times lighter than that of the best glider. Every gram added had to be deducted somewhere else, to make room for enough batteries on board, and provide a cockpit in which a pilot can live for a week. In the end, it is of the weight of just 2,300kg.










Stimulating innovation in the field of sheets of carbon, which now weigh only a third as much as sheets of printer paper (25 g/m2)


The airframe is made of composite materials: carbon fibre and honeycomb sandwich.













The upper wing surface is covered by a skin consisting of encapsulated solar cells, and the lower surface by a high-strength, flexible skin. 140 carbon-fiber ribs spaced at 50 cm intervals give the wing its aerodynamic cross-section, and also maintain its rigidity.

Test flights








The first wing spar section was delivered to Dübendorf in March 2012. However, during the final test of this central part, the structure of the wing spar succumbed to the load and broke. The initial shock soon turned out to be an opportunity: the flight around the world had to be postponed which opened the door for going to the United States and completing the epic journey across America.

After the official presentation of Solar Impulse 2 to the public on April 9th, the airplane will be rigorously tested during 2015, and the Round-The-World flight will be attempted between late February and July 2015.

Where it will set off?

The second generation of the solar-powered Solar Imulse all-electric aircraft will set off from the Persian Gulf emirate of Abu Dhabi for a record-setting around-the-world flight on photons alone.


Previously, the first generation of the giant, four-motor, single-place aircraft, flew from its homebase in Switzerland to Paris, later to Morocco, and then last summer crossed the United States from San Francisco to New York City. Piloted alternatively by co-founders Bertrand Piccard and Andre Borschberg, the globe-girdling flight will cover an estimated 40,000 km and take upwards of five months with extended layovers along the eastward flight route.

The team, which is now in Abu Dhabi after the Solar Impulse 2 airplane was disassembled and loaded aboard a 747 transport aircraft for the flight from Switzerland to the Gulf, announced their proposed flight route. From Abu Dhabi, the plane will fly first to Muscat, the capital of Oman, skirting sensitive Iranian airspace. The next leg will include its first extended flight over over, cross the Indian Ocean to Ahmedabad, India. From there the plane, which will be flying above 18,000 ft (5,400 m) as it lumbers along at a leisurely airspeed of 45-60 mph, and hopefully a bit faster with the help a westerly tailwinds, will make for Varanasi India. Next stop will be Mandalay in Myanmar, followed by Chongqing and Nanjing, China. Most of these legs will be over land, including the rugged Hengduan Mountains along the Myanmar-China border.

Well, let's wish them good luck and wait in anticipation them to start.

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