Sunny side up: Solar planes and a rare aviation appetite

— Pratima H

Updates from an unusual cockpit:

•           Flight Director is quite happy: No problem has been detected on the electrical and propulsion system, stability of airplane is good.

•           After one hour of flight: All very positive signs given we’re an experimental aircraft!

•           Bank angle test OK: Turns at 5° bank angle at different speeds. OK

•           Vibration test: OK Slight vibration felt by the pilot, coming most likely from the landing gear. It could be carbon frequencies coming from the open gear hatch – thus an aerodynamics problem and not related to the engine.

•           Test: Steady heading sideslip to test stability. OK

These may seem frivolous to a veteran pilot or a businessman laden with umpteen air-miles in his pocket. But for a journey that has started not now, not yesterday, not last week or last year but several decades and passionate dreams ago, these updates mean a lot, a lot!

Solar Impulse 2, the solar aircraft of Bertrand Piccard and André Borschberg, has successfully  carried out its first flight out of the Payerne slider-solar-impulse-california-golden-gate-2013aerodrome in Switzerland.

But this is a take-off that better be penciled back not to an early morning this week but instead to 1974 in USA when a solar airplane, California Sunrise I, achieved a 20-minute flight, at an altitude of 100 m and took it another height at over 800 m in the first manned solar-powered flight five years later.

This extraordinary solar radar then blips around 1990 again when the manned Sunseeker aircraft crossed the United States in a number of legs, as long as 400 km and again when NASA’s remotely piloted Helios, achieved a path-breaking altitude of 30,000 m around 2001.

In 2010, Solar Impulse 1 appeared in this runway and piloted by André Borschberg, it managed the first night flight without fuel. Just a few weeks later a solar-powered unmanned drone named Zephyr returned to earth after 14 days in the air.

And this week, the revolutionary single-seater aircraft, a dream nourished obsessively and relentlessly by Bertrand Piccard and André Borschberg, has taken forward this difficult journey ahead.

For 2 hours and 17 minutes, professional test pilot Marcus Scherdel experimented the aircraft’s performance in the skies and achieved a happy alignment between initial results and expected calculations and simulations.

As André Borschberg, Solar Impulse co-founder, CEO and pilot rightly captured, “This inaugural flight is an important stage – a step closer towards the round-the-world flight. It is also a huge emotional step for the entire team and all our partners who have worked on the aircraft. Si2 incorporates a vast amount of new technology to render it more efficient, reliable and in particular better adapted to long haul flights. It is the first aircraft which will have almost unlimited endurance,” said.

“Throughout such an innovative project, each stage is a leap into the unknown. Today suspense was at a high! The results show that our team of engineers can be very proud of the work it has accomplished during the last 10 years,” Bertrand Piccard, Solar Impulse founder, president and pilot chimed in.

Jetfuel finds substitutes

Bertrand and Andre belong to a rare species of dreamers. Their dream is a long one and attempts to attack some nightmarish environmental mistakes that mankind has been making. But the breed of such attempts has been thankfully on the rise.

If 2015 would be about a marquee flight of Solar Impulse around the world, 2017 would be about using landfills to power airplanes in some air pockets at least.

The partnership between Solena Fuels and British Airways has already committed to building the world’s first facility to convert landfill waste into jet fuel and even a location has been zeroed down upon – Thames Enterprise Park, part of the site of the former Coryton oil refinery in Thurrock, Essex.

solarimpulse6This would be a leap in the area of production of sustainable aviation fuel, if the idea takes off as intended, specially as we are talking of some 575,000 tonnes of post-recycled waste here. This level of waste that is normally destined for landfill or incineration, would be converted into 120,000 tonnes of clean burning liquid and  British Airways has made a long-term commitment to purchase all 50,000 tonnes per annum of the jet fuel produced at market competitive rates.

Willie Walsh, chief executive of British Airways’ parent company IAG, had remarked, “The sustainable jet fuel produced each year will be enough to power our flights from London City Airport twice over with carbon savings the equivalent of taking 150,000 cars off the road.”

It has been anticipated that by 2017, British Airways could be able to fuel flights from London’s City Airport to New York’s John F. Kennedy International Airport on trash.

Substitutes find Turbulence

Waste-to-fuel or sun-to-fuel, every dimension matters when we are talking of an industry that is notorious for zillions of carbon footprint spilled all over. With every flight that we board, an Oilzilla of sorts rears its head, thanks to the expensive and environmentally-not-so-friendly jet fuel that is combusted.

That is why the fantasy-like concept of solar planes has caught the fancy and attention of many mavericks since decades. In a solar airplane, at a principal level, one can capture the light of the sun and morph it into electrical energy with the use of those cells that are dappled all over the wings. The resultant energy not only powers the aircraft but can have many incidental uses like operating flight instruments. Thanks to the energy recovery cycle, theoretically, one can imagine an eternal flight, and hence the airplane does not need to land to refuel and can keep flying.

What matters here is the design and aerodynamic performance aspect where innovation has been devoted for so long as everything from shape, material types, and surface area can come into play when it comes to lifting the plane or cruising at certain speeds.Everything needs to be designed with a purpose but every part should fit in the greater scheme of things while also abiding to the strict lightweight guidelines, as a peek into the engineering den housing the structural analysis team led by Geri Piller of Solar Impulse shows.

Placing the extremely-resistant but frail carbon as to the direction in which the fibers must be placed, ascertaining the right thickness of each layer and number of plies to be put, fiddling with some complex manipulations on specialized software for FEA finite element analysis, are just some of the hard tasks that keep the designers busy here.

Yes, on paper, solar planes can churn up even 100% energy efficiency, but issues like the right irradiance or conducive weather conditions like a cloudless sky, poor speed performance (65 kph to 80 kph), fragility of photovoltaic cells,  usually obey Murphy’s law thus bringing performance levels to as low as 12% at times.

A lot of work is going on, and areas like above as well as autonomy, inside pressurization and heating conditions or human-machine interface are being rigorously attacked.

It’s worth the effort too because when you compare these planes to vanilla-fare, on areas like weight, wingspan, and of course, energy savings, there is quite a comparison.

Progress in on its way and one look at the following numbers shows that solar planes have indeed come far from their earlier hangers.

Flying a solar airplane, in numbers:

  • Max bank angle: 5°
  • Take off speed: 26 Kts (47 km/h)
  • Take off within only 165 yards (150 m) approx.
  • Max. Cruise Altitude: 8,500 m (27,000 ft)
  • Min. speed at sea level: 20 Kts (36 km/h)
  • Max. speed at sea level: 49 Kts (90 km/h)
  • Min. speed at 27,000 ft: 31,5 Kts (57 km/h)
  • Max. speed at 27,000 ft: 77 Kts (140 km/h)
  • Wingspan: 72m
  • Empty weight: 2300 kg


For the 2010 Solar Impulse flight, the numbers were:

  • Take-off time: 07/07/2010 – 06:51

  • Landing time: 08/07/2010 – 09:02

  • Flight duration: 26 hours 9 minutes 10 seconds

  • Maximum speed: 68 knots / 125.9 km/h

  • Average speed: 20.6 knots / 38.2 km/h

  • Maximum altitude: 8,720 m (above sea level)

  • Bertrand Piccard and André Borschberg were protected against the ambient cold or heat by high-density thermal insulation in the cockpit structure.

Several feet to go

Incidentally, Bertrand Piccard, President, initiator and pilot of Solar Impulse was born in a dynasty of explorers and scientists who conquered the heights and the depths of the planet . He doubles up as a psychiatrist specialised in hypnosis, and has feats like the Breitling Orbiter project and captaincy of the first non-stop round-the-world balloon flight tucked in his belt.

That’s probably what drives his dream since 2003 when  Bertrand presented the project to the Ecole Polytechnique de Lausanne (EPFL), leading to launch of a feasibility study, and by 26 June 2009, ensured that the aircraft was unveiled in front of 800 guests.

By 2010, his dream was propelled ahead when professional test pilot Markus Scherdel began the first test flights, to examine the airplane’s flight envelope and certify it for night flight.

With André Borschberg at the commands, the first night flight in the history of solar aviation happened, lasting in total 26 hours, 10 minutes and 19 seconds and making 3 world records viz.  maximum altitude (9’235 meters), maximum duration (26h10m19s) and gain in altitude (8’744 meters).

In 2012, they got an invitation to fly across Mediterranean from King Mohammed VI and here the journey that took place in 7 legs, entailed two world records in the first leg itself – free distance and distance with waypoints. Circa 2013, the Solar Impulse flew San Fransolarimpulsecisco-Phoenix-Dallas-St. Louis-Washington D.C.- New York City.

Now the idea is to hit 2015 with the plan to circumnavigate the globe in the northern hemisphere, with 4-5 stopovers along the way. There will be several other flights taking place in the coming months in order for this experimental machine, as is being hinted.

As the team at Solar Impulse anoints these adventures: They will open new horizons for science, but their objectives will be less to conquer unknown territories than to preserve the planet from today’s threats, in order to sustain and improve our quality of life. Is this a new Utopia? A beautiful scene from science fiction? No, a cutting-edge technological challenge! A sufficiently eccentric project to appeal to one’s emotions and get one’s adrenalin pumping: to harness a clean and renewable form of energy, and use it to fly night and day without limit.

This flight and others are more than another set of experiments or adventures and whether they fizz out or come off in flying colours, they add in their own ways, to the big expedition around renewable energies, clean technologies, sustainable development. Solar Impulse itself tags it right – to place dreams and emotions back at the heart of scientific adventure.


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