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July-16.Indd

July-16.Indd

SWATI SAXENA RTICLE A

EATURE F

There have been many efforts to build and fl y a solar-powered that does not guzzle conventional fuels. Although some headway has been made, there is still a long way to go.

batteries or fuel cells are used for this The Solar- purpose. They can be re-charged during Developments’ “Solar One” is a British the day. mid-wing, experimental, manned solar- Solar Plane History powered aircraft designed by David Solar plane history dates back to the Williams was the third solar-powered 1970s when the 27 lb (12 kg) unmanned aircraft to fl y. A motor- type AstroFlight Sunrise, the result of an USA aircraft originally built as a pedal- HE world’s fi rst offi cial fl ight in a ARPA (Advanced Research Projects powered to attempt the Channel solar-powered, man-carrying aircraft T Agency) contract, made the world’s fi rst crossing, the airplane proved too heavy took place on 29 April 1979. Technologists solar-powered fl ight from Bicycle Lake, to be successfully powered by human have been trying since long to look for a dry lake bed on the Fort Irwin Military power and was then converted to greener ways of fl ying aircraft. And what Reservation, on 4 November 1974. , using an can be greener than harnessing the energy The improved Sunrise II fl ew on driven by batteries that were charged of the to power aircraft. 27 September 1975 at Nellis Air Force before fl ight by a array on the A solar powered plane converts Base. wing. The maiden fl ight of “Solar One” into electric energy through Larry Mauro built the Mauro Solar took place at Lasham Airfi eld; Hampshire solar panels, which is used to turn the Riser and accomplished the world’s on 13 June 1979. . The solar panels are made fi rst offi cial fl ight in a solar-powered, The “Gossamer Penguin”, a up of photovoltaic cells, which convert man-carrying aircraft on 29 April 1979. smaller version of the human-powered sunlight into . Photovoltaic cells The aircraft used photovoltaic cells that “Gossamer Albatross” was completely are made up of semiconductor materials produced 350 watts at 30 volts, which solar-powered. The US company, such as silicon and . charged a Hughes 500 helicopter battery, AeroVironment, built it in 1979. A second When this material comes into contact which in turn powered the electric motor. prototype, the Solar Challenger, fl ew 262 with sunlight, the absorbed energy excites The aircraft was capable of powering km (163 mi) from Paris to England. On 7 the electrons and generates electricity. the motor for 3 to 5 minutes, following a July 1981, the aircraft, under solar-power, Solar planes need a source of energy 1.5-hour charge, enabling it to reach a fl ew 163 miles from Cormeilles-en-Vexin to power them at night. Usually electric altitude. Airport near Paris across the English Science Reporter, JULY 2016 34 FEATURETURE ARTICLERTICLE

FROM A SOLAR CELL TO A PV SYSTEM

Solar Module Solar Cell Electricity Meter

AC Isolator

Fusebox

Inverter PV-System

Battery

Charge Controller

Generation Meter

DC Isolator Solar Array Cabling

Mounting

Tracking System

Diagram of the possible components of a

Photovoltaic cells are Military aircrafts need to be fast, quiet of them are also not launched in the made up of semiconductor and agile. Fuel effi ciency is not of primary conventional way. Some are launched by materials such as silicon importance in military applications. hand with a running toss into the air. and cadmium telluride. Solar planes on the other hand are Commercial and military mostly used for surveillance. The shape of use air-breathing engines for propulsion. When this material comes these planes is very different as well. Solar One, two or four engines are used on into contact with sunlight, planes have high aspect ratio (length/ these planes. Whereas, several electric the absorbed energy excites span) wings as compared to commercial propellers (up to 14) power solar planes. or military aircrafts. They are closer to sail The cruising speed of Helios is no the electrons and generates planes in their wingspan. more than 27 miles per hour while electricity. Next, let’s compare the weight 747-400 cruises at 567 miles per hour. The of different planes. NASA’s Helios farthest fl ight for a solar plane has been Channel to RAF Manston near London, solar plane weighs nearly 929 kg while 163 miles per hour. fl ying for 5 hours and 23 minutes. Boeing 747-400 weighs nearly 397000 kg Solar planes, however, win in the Designed by Dr. Paul MacCready the with cargo and F-22 weighs 37875 kg. category of longevity. Regular planes Solar Challenger set an altitude record of Commercial airplanes need to transport need to be re-fueled and hence they need 14,300 feet. passengers and cargo and therefore to be grounded. There have been instances Comparison they need to have big fuselages and are of re-fueling aircrafts using another plane There are some basic differences between very heavy. Military airplanes carry one while in fl ight but it is a very expensive traditional planes such as Boeing 747 or or two people and need to have high task. Solar planes can remain in air for the military aircraft F-22A raptor and maneuverability. Therefore, they are as long as the batteries continue to get the solar powered planes. A commercial lighter. charged by solar energy. plane, such as Boeing 747-400, transports Solar planes are even lighter as The amount of solar energy per hundreds of passengers from one location they are powered only by solar energy square foot of panels in an hour is very to another with decent fuel mileage. and cannot fl y if made very heavy. Most less as compared to the energy produced 35 Science Reporter, JULY 2016 FEATURE ARTICLE Solar planes can help with reconnaissance and can observe a particular spot for days. can do some of these tasks but solar planes are closer to the ground and can see more detail with less expensive cameras. They are less expensive as compared to a Pathfi nder-Plus/HTML/ED02-0161-2.html) Pathfi and can be moved (Source: http://www.dfrc.nasa.gov/Gallery/Photo/ as needed. Pathfi nder-Plus in fl ight over , June 2002 by one gallon (3.78 liters) of jet fuel. Solar kilometers) where they can receive direct satellite and can be moved as needed. panels convert nearly 10-20% of the uninterrupted sunlight. During fl ight, the A solar plane costs nearly 20 million total energy into electric energy used for plane automatically switches between US dollars so they are still very expensive propellers. Since the available power is battery and solar as needed. During as compared to gliders due to the very less, the solar planes are kept very landing, both power sources are cut off so expensive solar panels, which comprise of light so that wind can lift them. They are that it can glide down. They are usually nearly half of the total cost. Boeing 747, on made very thin and light. very slow when coming down due to the other hand, costs nearly 250 million Often carbon-fi ber pipes are used for their lightweight and big wingspan. US dollars. the frame with a strong fabric like Kevlar Solar planes can help with As they are environment friendly, stretched across it. They run on batteries reconnaissance and can observe a solar planes leave no carbon footprint. or fuel cells at night. The solar panels are particular spot for days. Satellites can do And since they fl y at very low speeds, spread all across the wing to utilize the some of these tasks but solar planes are there is no threat to birds. entire open surface area. closer to the ground and can see more But one of the disadvantages is that Solar planes prefer to fl y above detail with less expensive cameras. They solar planes need favorable weather the clouds in the Stratosphere (12 to 20 are less expensive as compared to a conditions for . They can’t stay in Cumulus clouds or turbulent layers of the sky. Let’s have a look at some solar planes.

NASA Pathfi nder, Centurion and Helios (United States) NASA’s Pathfi nder, Pathfi nder Plus, Centurion, and Helios were a series of solar and system–powered unmanned aircraft developed by AeroVironment, Inc. (https://www.avinc.com) from 1983 until 2003 under NASA’s Environmental Research Aircraft and Sensor Technology program (ERAST). Helios/HTML/ED01-0209-3.html) On 11 September 1995, Pathfi nder set an unoffi cial altitude record for solar- (Source: http://www.dfrc.nasa.gov/Gallery/Photo/ powered aircraft of 50,000 feet (15,000 m) during a 12-hour fl ight from NASA Dryden. On 7 July 1997, Pathfi nder raised the altitude record for solar–powered aircraft to 71,530 feet (21,800 m), which was also the record for –driven Helios in fl ight by NASA aircraft. On 6 August 1998, Pathfi nder

Science Reporter, JULY 2016 36 FEATURE ARTICLE (Ref.: www.solar-fl ight.com) (Ref.: www.solar-fl

Solar Flight Inc.’s solar- Sunseeker II: One seat solar plane by Solar Flight Inc. powered airplane Sunseeker, aerial . They were built to develop where the Wright Brothers fi rst fl ew. It the technologies that would allow long- was the fi rst crossing of the United States piloted by Eric Raymond, term, high-altitude aircraft to serve as made by a solar-powered airplane – an became the fi rst solar- “atmospheric satellites”, to perform affi rmation of the technology’s potential atmospheric research tasks as well as and a milestone in aviation history. powered airplane to cross the serve as communications platforms. The Sunseeker II, built in 2002, United States. It used a small was updated in 2005–2006 with a more Solair 1 and 2 (Germany) powerful motor, larger wing, lithium battery packs and updated control battery pack charged by solar Solair 1 and Solair 2 are two German- electronics. In 2009, it became the fi rst designed . The human cells on the wings for takeoff, solar-powered aircraft to cross the Alps, piloted Solair 1 was developed by Günther 99 years after the fi rst crossing of the Alps and then was able to fl y Rochelt and employed 2499 wing- by an aircraft. directly on solar power. mounted solar cells, giving an output of 1.8 kilowatts (kW). This was equivalent to approximately 2.4 horsepower (hp), and (Switzerland) Plus raised the national altitude record to 2.2 kW (3.0 hp). Solar Impulse (http://www. 80,201 feet (24,445 m) for solar-powered The aircraft fi rst fl ew at Unterwössen, solarimpulse.com) is a Swiss long-range and propeller-driven aircraft. Germany on 21 August 1983 for 5 hours experimental solar-powered aircraft Centurion was the third generation and 41 minutes, “mostly on solar energy project, and also the name of the project’s aircraft in the NASA Pathfi nder series and also thermals”. The aircraft is now two operational aircraft. The fi rst short- of electrical-powered fl ying wing displayed at the German Museum in hop (350 m) test fl ight of the Solar Impulse unmanned aircraft. Centurion’s maiden Munich. prototype was made on 3 December 2009. fl ight took place at Rogers Dry Lake on 10 The prototype and its successor, Solar The piloted Solair II made its fi rst November 1998, and lasted a total of 1 hr Impulse 2, are each powered by four fl ight in May 1998 but the propulsion and 24 minutes. The Centurion was later electric motors. Energy from solar cells system overheated too fast. Development modifi ed into the Helios Prototype, which on the wings and horizontal stabilizer stopped when Günther Rochelt suddenly piloted remotely by Greg Kendall reached is stored in lithium polymer batteries died in September 1998. an altitude of 96,863 feet (29,524 m) on 14 and used to drive propellers. In 2010, it August 2001, a world record for sustained completed the fi rst manned 24-hour fl ight horizontal fl ight by a winged aircraft. Sunseeker Series (United States) completely powered by solar power. Unfortunately, on 26 June 2003, the Helios Solar Flight Inc.’s solar-powered airplane In 2012, the Solar Impulse successfully Prototype broke up and fell into the Sunseeker, piloted by Eric Raymond, completed an intercontinental fl ight, the Pacifi c Ocean during a remotely piloted became the fi rst solar-powered airplane fi rst-ever by a solar plane, fl ying a 19- systems checkout fl ight in preparation to cross the United States. It used a small hour trip from , Spain, to Rabat, for an endurance test scheduled for the battery pack charged by solar cells on the Morocco. The following year, the aircraft following month. wings for takeoff, and then was able to fl y set a new world distance record for solar The NASA Helios Prototype was directly on solar power. aviation on a fl ight from Phoenix, Arizona the fourth and fi nal aircraft developed The expedition began in the Southern to Dallas-Fort Worth International Airport as part of an evolutionary series of solar- California desert and with 21 fl ights as part of its multi-segment trip across the and fuel-cell-system-powered unmanned ended in North Carolina, in a fi eld near United States. 37 Science Reporter, JULY 2016 FEATURE ARTICLE worlds-1st-solar-plane-landed-in-ahmedabad/) (Source: Wikipedia) (Source: http://indianexpress.com/photos/picture-gallery-others/ Solar Impulse 2 at the Payerne Air Base in Switzerland “Solar Impulse 2” piloted by Bertrant Piccard, from Switzerland lands in in November 2014 Ahmedabad on 10 March 2015

A second aircraft, completed in 2014, scheduled to return to Abu Dhabi in In 2012, the Solar Impulse and named Solar Impulse 2 (Si2), carries August 2015, upon the completion of its more solar cells and more powerful multi-stage journey. However, due to successfully completed an engines, among other improvements. battery damage, continuation of the fl ight intercontinental fl ight, the In March 2015, the plane began a beyond Hawaii has been postponed until of the Earth, departing April 2016. fi rst-ever by a solar plane, from Abu Dhabi in the United Arab fl ying a 19-hour trip from Emirates. The plane landed in Ahmedabad QinetiQ Zephyr (United Kingdom) on March 10 around midnight and was The QinetiQ Zephyr is a lightweight Madrid, Spain, to Rabat, stationed for six days. It maintained a solar-powered unmanned aerial minimum altitude of around 5,200 meters Morocco. engineered by the United Kingdom on its fl ight to Varanasi. defense fi rm, QinetiQ. As of 23 July a span of 22.5 meters. It uses sunlight to Its 17,248 solar cells and four lithium 2010, it holds the endurance record for charge lithium-sulphur batteries during batteries, weighing 633 kg, supply the an of over two the day, which power the aircraft at night. electric motors with enough renewable weeks (336 hours). It is made of carbon The aircraft has been designed for use in energy for a 24x7 fl ight, up to an fi ber-reinforced polymer construction, the observation and communications relay. altitude of 8,500 meters. It was originally 2010 version weighing 50 kg (110 lb) with The 2008 Zephyr version fl ew for 82 hours, reaching 61,000 feet (19,000 The QinetiQ Zephyr is a lightweight solar-powered m) in altitude in July 2008, the then unmanned aerial vehicle engineered by the United unoffi cial world record for the longest duration unmanned fl ight. In July 2010, Kingdom defense fi rm, QinetiQ. As of 23 July 2010, the 2010 version of the Zephyr made a it holds the endurance record for an unmanned world record unmanned aerial vehicle endurance fl ight of 336 hours, 22 minutes aerial vehicle of over two weeks (336 hours). and 8 seconds (more than two weeks).

Soaring (China) China’s fi rst solar-powered aircraft “Soaring” was designed and built by Danny H. Y. Li and Zhao Yong in 1992. The body and wings are hand-built predominantly of carbon fi ber, Kevlar and wood. The design uses winglets to increase the effective wingspan and reduce induced drag. (Source: http://diydrones.com)

Dr. Swati Saxena has a PhD in Aerospace Engineering from the Penn State University, USA. Address in India: C/o Dr. Ashok Saxena, QinetiQ Zephyr in fl ight 204, Narain Towers, Agra-282002; Email: swati. [email protected] Science Reporter, JULY 2016 38

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