Solar Impulse Explained

Solar Impulse is a Swiss long-range experimental solar-powered aircraft project, and also the name of the project's two operational aircraft.[1] The privately financed project is led by Swiss engineer and businessman André Borschberg and Swiss psychiatrist and balloonist Bertrand Piccard, who co-piloted Breitling Orbiter 3, the first balloon to circle the world non-stop.[2] The Solar Impulse project's goals were to make the first circumnavigation of the Earth by a piloted fixed-wing aircraft using only solar power and to bring attention to clean technologies.[3]

The aircraft is a single-seated monoplane powered by photovoltaic cells; it is capable of taking off under its own power. The prototype, often referred to as Solar Impulse 1, was designed to remain airborne up to 36 hours.[4]

It conducted its first test flight in December 2009. In July 2010, it flew an entire diurnal solar cycle, including nearly nine hours of night flying, in a 26-hour flight.[5] Piccard and Borschberg completed successful solar-powered flights from Switzerland to Spain and then Morocco in 2012, and conducted a multi-stage flight across the US in 2013.[6]

A second aircraft, completed in 2014 and named Solar Impulse 2, carries more solar cells and more powerful motors, among other improvements. On 9 March 2015, Piccard and Borschberg began to circumnavigate the globe with Solar Impulse 2, departing from Abu Dhabi in the United Arab Emirates.[7] The aircraft was scheduled to return to Abu Dhabi in August 2015 after a multi-stage journey around the world.[8] By June 2015, the plane had traversed Asia, and in July 2015, it completed the longest leg of its journey, from Japan to Hawaii. During that leg, the aircraft's batteries sustained thermal damage and took months to replace.

A battery cooling system was installed and Solar Impulse 2 resumed the circumnavigation in April 2016, when it flew on to California.[9] [10] It continued across the US until it reached New York City in June 2016. Later that month, the aircraft crossed the Atlantic Ocean to the city of Seville.[11] It stopped in Egypt before returning to Abu Dhabi on 26 July 2016, more than 16 months after it had left (506 days), completing the approximately 42,000-kilometre (26,000-mile) first circumnavigation of the Earth by a piloted fixed-wing aircraft using only solar power.[12] [13]

In 2019 the Solar Impulse 2 was sold to Skydweller, a Spanish-American company that is developing autonomous unmanned aerial vehicles capable of continuous flight. It plans to use the plane for research and development flights, after which the Solar Impulse 2 is planned to be on permanent display at the Swiss Museum of Transport.

Project development and funding

Bertrand Piccard initiated the Solar Impulse project in November 2003 after undertaking a feasibility study in partnership with the École Polytechnique Fédérale de Lausanne (EPFL).[14] As a mechanical engineer, co-founder André Borschberg directed the construction of each aircraft and oversees the preparation of the flight missions.[15] By 2009, they had assembled a multi-disciplinary team of 50 engineers and technical specialists from six countries, assisted by about 100 outside advisers and 80 technological partners.[16]

The project is financed by a number of private companies and individuals, as well as receiving around CHF 6 million (US$6.4 million) in funding from the Swiss government.[17] The project's private financial backers include Omega SA, Solvay, Schindler, ABB[18] and Peter Diamandis.[19] The EPFL, the European Space Agency and Dassault have provided technical expertise, while SunPower provided the aircraft's photovoltaic cells.[20] [21]

Piccard stated that the entire project from its beginnings in 2003 until mid-2015 had cost €150 million.[22] It raised another €20 million in late 2015 to continue the round-the-world flight.[23]

Timeline

Solar Impulse 1 (HB-SIA)

The first Solar Impulse aircraft, registered as HB-SIA, was primarily designed as a demonstration aircraft. It has a non-pressurized cockpit and a single wing with a wingspan similar to that of the Airbus A340 airliner. Under the wing are four nacelles, each with a set of lithium polymer batteries, a 10hp electric motor and one twin-bladed propeller. To keep the wing as light as possible, a customised carbon fibre honeycomb sandwich structure was used. 11,628 photovoltaic cells on the upper wing surface and the horizontal stabilizer generate electricity during the day to power the electric motors and to charge the batteries allowing flight at night, theoretically enabling the single-seat plane to stay in the air indefinitely.[27] [28]

The aircraft's major design constraint is the capacity of the lithium polymer batteries. Over an optimum 24-hour cycle, the motors can deliver a combined average of about 8hp, roughly the power used by the Wright brothers' Flyer, the first successful powered aircraft, in 1903. In addition to the charge stored in its batteries, the aircraft uses the potential energy of height gained during the day to power its night flights.[29]

Operational history

Maiden flight and other early flights

On 26 June 2009, Solar Impulse 1 was first presented to the public at the Dübendorf Air Base, Switzerland. Following taxi testing, a short-hop test flight was made on 3 December 2009,[30] piloted by Markus Scherdel.[31] Borschberg, co-leader of the project team, said of the flight: On 7 April 2010, the plane conducted an 87-minute test flight, piloted by Markus Scherdel. This flight reached an altitude of 12000NaN0.[32] [33] On 28 May 2010, the aircraft made its first flight powered entirely by solar energy, charging its batteries in flight.[34]

First overnight flight

On 8 July 2010, Solar Impulse 1 achieved the world's first manned 26-hour solar-powered flight.[35] [36] [37] The airplane was flown by Borschberg, and took off at 06:51 Central European Summer Time (UTC+2) on 7 July from Payerne Air Base, Switzerland. It returned for a landing the following morning at 09:00 local time.[38] During the flight, the plane reached a maximum altitude of 8700m (28,500feet).[39] At the time, the flight was the longest and highest ever flown by a manned solar-powered aircraft; these records were officially recognized by the Fédération Aéronautique Internationale (FAI) in October 2010.[40] [41]

International and intranational flights

Belgium and France (2011)

On 13 May 2011 at 21:30 local time, the plane landed at Brussels Airport, after completing a 13-hour flight from its home base in Switzerland. It was the first international flight by the Solar Impulse, which flew at an average altitude of 6000feet for a distance of 6300NaN0, with an average speed of 500NaN0. The aircraft's slow cruising speed required operating at a mid-altitude, allowing much faster air traffic to be routed around it.[42] The aircraft was piloted by Borschberg. The project's other co-founder, Piccard, said in an interview after the landing: "Our goal is to create a revolution in the minds of people...to promote solar energies – not necessarily a revolution in aviation."[43] [44]

A second international flight to the Paris Air Show was attempted on 12 June 2011, but the plane turned back and returned to Brussels because of adverse weather conditions.[45] In a second attempt on 14 June, Borschberg successfully landed the aircraft at Paris' Le Bourget Airport after a 16-hour flight.[46]

First intercontinental flight (2012)

On 5 June 2012, the Solar Impulse successfully completed its first intercontinental flight, a 19-hour trip from Madrid, Spain, to Rabat, Morocco.[47] During the first leg of the flight from Payerne Air Base to Madrid, the aircraft broke several further records for solar flight, including the longest solar-powered flight between pre-declared waypoints (1099.3km (683.1miles)) and along a course (1116km (693miles)).[48]

United States (2013)

On 3 May 2013, the plane began its cross-US flight with a journey from Moffett Field in Mountain View, California, to Phoenix Goodyear Airport in Arizona. Successive legs of the flight ended at Dallas-Fort Worth airport, Lambert–St. Louis International Airport,[49] Cincinnati Municipal Lunken Airport to change pilots and avoid strong winds,[50] and Washington Dulles International Airport.[51] On 6 July 2013, following a lengthy layover in Washington, Solar Impulse completed its cross-country journey, landing at New York City's JFK International Airport at 23:09 EDT.[6] [52] The landing occurred three hours earlier than originally intended, because a planned flyby of the Statue of Liberty was cancelled as a result of damage to the covering on the left wing.[6]

Each flight leg took between 14 and 22 hours.[26] [53] The aircraft's second leg of its trip on 23 May to Dallas-Fort Worth covered 1541km (958miles) and set several new world distance records in solar aviation.[54] Solar Impulse 1 was placed on public display at JFK after its landing. In August 2013, it was disassembled, then transported via a Cargolux B-747-400F to Dübendorf Air Base, where it was placed in storage in a hangar.

Detailed routeSource:[55]
Leg Start[56] StopOriginDestinationDistanceFlight timeAvg. speedPilot
1 3 May 14:12  4 May 08:30Moffett Field, California (KNUQ)Phoenix, Arizona (KGYR)align=right 984 kmalign=right 18 h 18 minalign=right 53 km/hBertrand Piccard
222 May 12:47 23 May 07:08 Phoenix, Arizona (KGYR)Dallas, Texas (KDFW)align=right 1541 kmalign=right 18 h 21 minalign=right 84 km/hAndré Borschberg
3 3 Jun 10:06  4 Jun 07:28 Dallas, Texas (KDFW)Saint Louis, Missouri (KSTL)align=right 1040 kmalign=right 21 h 22 minalign=right 49 km/hBertrand Piccard
414 Jun 11:01 15 Jun 02:15 Saint Louis, Missouri (KSTL)Cincinnati, Ohio (KLUK)align=right 15 h 14 minAndré Borschberg
515 Jun 15:1016 Jun 05:15Cincinnati, Ohio (KLUK)Washington, DC (KIAD)align=right 14 h 5 minBertrand Piccard
6 6 July 09:56  7 July 05:15 Washington, DC (KIAD)New York City, New York (KJFK)align=right 19 h 19 minAndré Borschberg

Aircraft on display

In March 2015, the plane was transported by truck to Paris to be part of the permanent exhibition at Cité des Sciences et de l'Industrie.[57]

Solar Impulse 2 (HB-SIB)

Construction history

Construction started in 2011 on the second aircraft, known as Solar Impulse 2, which carries the Swiss registration HB-SIB. Completion was initially planned for 2013, with a 25-day circumnavigation of the globe planned for 2014. A structural failure occurred on the aircraft's main spar during static tests in July 2012, leading to delays in the flight testing schedule to allow repairs. Solar Impulse 2s first flight took place at Payerne Air Base on 2 June 2014.[58]

Design

The wingspan of Solar Impulse 2 is 71.9m (235.9feet), slightly less than that of an Airbus A380, the world's largest passenger airliner, but compared with the 500-tonne A380,[59] the carbon-fibre Solar Impulse weighs only about 2.3t, little more than an average SUV.[60] It features a non-pressurized cockpit in size[61] and advanced avionics, including limited functionality of an autopilot that allows the pilot to sleep for up to 20 minutes at a time,[62] enabling multi-day transcontinental and trans-oceanic flights.[16] Supplemental oxygen and various other environmental support systems allow the pilot to cruise up to an altitude of .

Operational history

Solar Impulse 2 was first publicly displayed on 9 April 2014. Its inaugural flight took place on 2 June 2014, piloted by Markus Scherdel.[63] The aircraft averaged a ground speed of 30knots, and reached an altitude of 5500feet.[64] The first night flight was completed on 26 October 2014, and the aircraft reached its maximum altitude during a flight on 28 October 2014.

2015–16 circumnavigation of the Earth

The repair work to the aircraft's main spar delayed Solar Impulse 2s circumnavigation of the Earth from 2012 to 2015.[65] The aircraft was delivered to Masdar City in Abu Dhabi for the World Future Energy Summit in late January 2015,[66] and it began the journey from Al Bateen Executive Airport on 9 March 2015.[7] [67] It was scheduled to return to the same location in August 2015.[8] A mission control centre for the circumnavigation was established in Monaco, using satellite links to gather real-time flight telemetry and remain in constant contact with the aircraft and the support team.[68] The route followed by Solar Impulse 2 was entirely in the Northern Hemisphere. It left Abu Dhabi, then it headed east to nearby Oman and India.[69] [70] Twelve stops were originally planned along the route, with pilots Borschberg and Piccard alternating; at each stop, the crew awaited good weather conditions along the next leg of the route.[71] For most of its time airborne, Solar Impulse 2 cruised at a ground speed of between 50and, usually at the slower end of that range at night to save power. Legs of the flight crossing the Pacific and Atlantic oceans were the longest stages of the circumnavigation, taking up to five days and nights.[8] [72] On multi-day flights, the pilots took 20-minute naps and used yoga or other exercises to promote blood flow and maintain alertness.[61] By the end of May 2015, the plane had traversed Asia.[73] It made an unscheduled stop in Japan to await favourable weather over the Pacific, increasing the expected number of legs of the journey to 13.[74] The aircraft began the flight from Japan to Hawaii on 28 June 2015 (29 June, Japan local time).[75] With Borschberg in the cockpit, it reached Hawaii on 3 July, setting new records for the world's longest solar-powered flight both by time (117 hours, 52 minutes) and distance (7,212 km; 4,481 mi). The flight's duration was also a record for longest solo flight, by time, for any aircraft.[76] [77] [78] During that leg the plane's batteries were damaged by overheating because they were packed in too much insulation. New parts had to be ordered, and as it was late in the season, with days shortening in the northern hemisphere, the plane was grounded in Hawaii. The US Department of Transportation stored the aircraft in a hangar at Kalaeloa Airport on Oahu.[79] [80] New batteries were made and installed in the plane. Test flights began in February 2016[81] to prepare for resumption of the circumnavigation once northern hemisphere days lengthened enough to permit multi-day solar-powered flights.[82] [23] A favourable weather window opened in April 2016, and the plane resumed its journey,[9] [83] landing at Moffett Field, in California, on 23 April.[10] During that flight, Piccard, via a live videolink, spoke with Ban Ki-moon and Doris Leuthard before the General Assembly of the United Nations, from the cockpit of Solar Impulse 2, commenting on that day's historic signing of the Paris Agreement and discussing how using clean technologies can create jobs and fight global warming.[84] Additional legs of the flight were added in the US as Solar Impulse 2 flew to Phoenix, Arizona,[85] [86] Tulsa, Oklahoma,[87] Dayton, Ohio,[88] Lehigh Valley, Pennsylvania[89] and New York City, arriving there on 11 June 2016.[90] Piccard piloted the aircraft across the Atlantic Ocean, arriving in Seville, Spain, on 23 June.[11] The aircraft next stopped in Cairo, Egypt, on 13 July,[12] and landed in Abu Dhabi on 26 July, completing the around-the-world trip in a total of 17 stages and 16-1/2 months; it was the first circumnavigation of the Earth by a piloted fixed-wing aircraft using only solar power.[13]

Detailed route

LegStart[91] OriginDestinationFlight timeAvg. speedMax. altitudePilot
1data-sort-value="2015-03-09 03:12" 9 March 2015 03:12 Abu Dhabi, UAE (OMAD) Muscat, Oman (OOMS)data-sort-value="013:01" align=right 13 h 1 mindata-sort-value="772" align=right 772km (480miles)data-sort-value="59.2" align=right 59.2km/hdata-sort-value="6383" align=right 6383m (20,942feet)data-sort-value="Borschberg" A. Borschberg[92]
2data-sort-value="2015-03-10 02:35" 10 March 02:35 Muscat, Oman (OOMS) Ahmedabad, India (VAAH)data-sort-value="015:20" align=right 15 h 20 mindata-sort-value="1593" align=right 1593order=flipNaNorder=flip[93] data-sort-value="103.9" align=right 103.9order=flipNaNorder=flipdata-sort-value="8874" align=right 8874order=flipNaNorder=flipdata-sort-value="Piccard" B. Piccard[94]
3data-sort-value="2015-03-18 01:48" 18 March 01:48 Ahmedabad, India (VAAH) Varanasi, India (VEBN)data-sort-value="013:15" align=right 13 h 15 mindata-sort-value="1170" align=right 1170order=flipNaNorder=flipdata-sort-value="88.3" align=right 88.3order=flipNaNorder=flipdata-sort-value="5182" align=right 5182order=flipNaNorder=flipBorschberg[95]
4data-sort-value="2015-03-18 23:52" 18 March 23:52 Varanasi, India (VEBN) Mandalay, Myanmar (VYMD)data-sort-value="013:29" align=right 13 h 29 mindata-sort-value="1536" align=right 1536order=flipNaNorder=flipdata-sort-value="113.9" align=right 113.9order=flipNaNorder=flipdata-sort-value="8230" align=right 8230order=flipNaNorder=flipPiccard[96]
5data-sort-value="2015-03-29 21:06" 29 March 21:06 Mandalay, Myanmar (VYMD) Chongqing, China (ZUCK)data-sort-value="020:29" align=right 20 h 29 mindata-sort-value="1636" align=right 1636order=flipNaNorder=flipdata-sort-value="79.9" align=right 79.9order=flipNaNorder=flipdata-sort-value="8634" align=right 8634order=flipNaNorder=flipPiccard[97]
6data-sort-value="2015-04-20 22:06" 20 April 22:06 Chongqing, China (ZUCK) Nanjing, China (ZSNJ)data-sort-value="017:22" align=right 17 h 22 mindata-sort-value="1384" align=right 1384order=flipNaNorder=flipdata-sort-value="79.7" align=right 79.7order=flipNaNorder=flipdata-sort-value="4270" align=right 4270order=flipNaNorder=flipPiccard[98]
7data-sort-value="2015-05-30 18:39" 30 May 18:39 Nanjing, China (ZSNJ) Nagoya, Japan (RJNA)data-sort-value="044:09" align=right 44 h 9 mindata-sort-value="2942" align=right 2942order=flipNaNorder=flipdata-sort-value="66.6" align=right 66.6order=flipNaNorder=flipdata-sort-value="8634" align=right 8634order=flipNaNorder=flipBorschberg[99] [100]
8data-sort-value="2015-06-28 18:03" 28 June 18:03 Nagoya, Japan (RJNA) Kalaeloa, Hawaii, US (PHJR)data-sort-value="117:52" align=right 117 h 52 mindata-sort-value="8924" align=right 8924order=flipNaNorder=flipdata-sort-value="75.7" align=right 75.7order=flipNaNorder=flipdata-sort-value="8634" align=right 8634order=flipNaNorder=flipBorschberg[101]
9data-sort-value="2016-04-21 16:15" 21 April 2016 16:15 Kalaeloa, Hawaii, US (PHJR) Mountain View, CA, US (KNUQ)data-sort-value="062:29" align=right 62 h 29 mindata-sort-value="4086" align=right 4086order=flipNaNorder=flipdata-sort-value="65.4" align=right 65.4order=flipNaNorder=flipdata-sort-value="8634" align=right 8634order=flipNaNorder=flipPiccard[102]
10data-sort-value="2016-05-02 12:03" 2 May 12:03 Mountain View, CA, US (KNUQ) Phoenix, AZ, US (KGYR)data-sort-value="015:52" align=right 15 h 52 mindata-sort-value="1113" align=right 1113order=flipNaNorder=flipdata-sort-value="70.2" align=right 70.2order=flipNaNorder=flipdata-sort-value="6706" align=right 6706order=flipNaNorder=flipBorschberg[103]
11data-sort-value="2016-05-12 11:05" 12 May 11:05 Phoenix, AZ, US (KGYR) Tulsa, OK, US (KTUL)data-sort-value="018:10" align=right 18 h 10 mindata-sort-value="1570" align=right 1570order=flipNaNorder=flipdata-sort-value="86.4" align=right 86.4order=flipNaNorder=flipdata-sort-value="6706" align=right 6706order=flipNaNorder=flipPiccard[104]
12data-sort-value="2016-05-21 09:22" 21 May 09:22 Tulsa, OK, US (KTUL) Dayton, OH, US (KDAY)data-sort-value="016:34" align=right 16 h 34 mindata-sort-value="1199" align=right 1199order=flipNaNorder=flipdata-sort-value="72.4" align=right 72.4order=flipNaNorder=flipdata-sort-value="6401" align=right 6401order=flipNaNorder=flipBorschberg[105]
13data-sort-value="2016-05-25 08:02" 25 May 08:02 Dayton, OH, US (KDAY) Lehigh Valley, PA, US (KABE)data-sort-value="016:49" align=right 16 h 49 mindata-sort-value="1044" align=right 1044order=flipNaNorder=flipdata-sort-value="62.2" align=right 62.2order=flipNaNorder=flipdata-sort-value="4572" align=right 4572order=flipNaNorder=flipPiccard[106]
14data-sort-value="2016-06-11 03:18" 11 June 03:18 Lehigh Valley, PA, US (KABE) New York, NY, US (KJFK)data-sort-value="004:41" align=right 4 h 41 mindata-sort-value="265" align=right 265order=flipNaNorder=flipdata-sort-value="56.6" align=right 56.6order=flipNaNorder=flipdata-sort-value="915" align=right 915order=flipNaNorder=flipBorschberg[107]
15data-sort-value="2016-06-20 06:30" 20 June 06:30 New York, NY, US (KJFK) Seville, Spain (LEZL)data-sort-value="071:08" align=right 71 h 8 mindata-sort-value="6765" align=right 6765order=flipNaNorder=flipdata-sort-value="94.3" align=right 94.3order=flipNaNorder=flipdata-sort-value="8534" align=right 8534order=flipNaNorder=flipPiccard[108]
16data-sort-value="2016-07-11 04:20" 11 July 04:20 Seville, Spain (LEZL) Cairo, Egypt (HECA)data-sort-value="048:50" align=right 48 h 50 mindata-sort-value="3745" align=right 3745order=flipNaNorder=flipdata-sort-value="76.7" align=right 76.7order=flipNaNorder=flipdata-sort-value="8534" align=right 8534order=flipNaNorder=flipBorschberg[109]
17data-sort-value="2016-07-23 23:28" 23 July 2016 23:28 Cairo, Egypt (HECA) Abu Dhabi, UAE (OMAD)data-sort-value="048:37" align=right 48 h 37 mindata-sort-value="2694" align=right 2694order=flipNaNorder=flipdata-sort-value="55.4" align=right 55.4order=flipNaNorder=flipdata-sort-value="8534" align=right 8534order=flipNaNorder=flipPiccard[110]
Totalalign=right 558 h 7 min
(23.25 d)
align=right 42438order=flipNaNorder=flipalign=right 76order=flipNaNorder=flipalign=right 8874order=flipNaNorder=flip

Notes:

Post-flight sale

In September 2019 the Solar Impulse 2 aircraft was sold to Skydweller, a Spanish-American company that is developing autonomous unmanned aerial vehicles capable of continuous flight and "carrying radar, electronic optics, telecommunications devices, telephone listening and interception systems".[111] As part of this sale, the Solar Impulse 2 aircraft was transferred from Switzerland to Spain though once Skydweller completes its research and development flights the Solar Impulse 2 will be transferred back to Switzerland for permanent display at the Swiss Museum of Transport.[112] [113] By February 2023, Skydweller Aero had conducted its first autonomous flight and was planning to have a production aircraft operational by 2024; its goal is to operate year-round in latitudes between Miami (26°N) to Rio de Janeiro (23°S).[114]

Honours

In 2015, Swissmint issued a special commemorative coin in anticipation of the Earth circumnavigation mission.[115]

In 2016, the Swiss Post edited a special stamp to honour the achievement of Solar Impulse 2.[116]

External links

Notes and References

  1. News: Cardwell. Diane. Cross-Country Solar Plane Expedition Set for Takeoff. 1 May 2013. The New York Times. 2 May 2013.
  2. Web site: A Speck in the Sky. The New York Times. 21 March 1999. 24 June 2013.
  3. Div, Stav. "Solar Impulse 2: The groundbreaking aircraft demonstrating the possibilities of clean energy", The Independent, 2 June 2016
  4. Web site: HB-SIA Mission . Solar Impulse Project . 5 December 2009 . dead . https://web.archive.org/web/20110726022510/http://www.solarimpulse.com/en/documents/hbsia_mission.php?lang=en&group=hbsia . 26 July 2011 . dmy .
  5. https://web.archive.org/web/20100710042340/http://www.swisster.ch/news/science-tech/swiss-solar-plane-makes-history-with-night-flight.html "Swiss solar plane makes history with night flight"
  6. Web site: Solar Impulse ends cross-country US flight slightly early in NY due to torn left wing. Engadget. 6 July 2013. 7 July 2013.
  7. Web site: Batrawy, Aya. 9 March 2015. Solar-powered plane takes off for flight around the world. Associated Press. 14 March 2015.
  8. News: Pilots to take off from Abu Dhabi for historic solar-powered flight. Al Wasmi. Naser. 25 September 2014. . 7 January 2015 .
  9. Web site: Solar Impulse sets off for California after long lay-off. Jonathan . Amos . 21 April 2016 . BBC.
  10. Berger, Noah. "Solar-powered plane completes journey across Pacific Ocean", The Charlotte Observer, 24 April 2016
  11. Amos, Jonathan. "Solar Impulse completes Atlantic crossing with landing in Seville", BBC, 23 June 2016
  12. Amos, Jonathan. "Solar Impulse: Zero-fuel plane lands in Cairo", BBC News, 13 July 2016
  13. https://www.bbc.com/news/science-environment-36890563 "Solar Impulse completes historic round-the-world trip"
  14. Web site: What happened between 2001 and 2003?. Solar Impulse. 31 December 2003. dead. https://web.archive.org/web/20130820013235/http://www.solarimpulse.com/timeline/view/6652. 20 August 2013. dmy-all.
  15. News: Can solar power fuel future flight. 29 November 2011. CNN. 29 November 2011.
  16. Web site: Major steps. Solar Impulse. 5 December 2009. dead. https://web.archive.org/web/20120915070035/http://solarimpulse.com/en/airplane/major-steps/. 15 September 2012. dmy-all.
  17. Web site: Government supports Solar Impulse with CHF6m. SwissInfo.ch. 18 February 2015. 24 March 2015.
  18. Web site: Piccard. Bertrand. Solar Impulse gets a lift!. 4 April 2014. 4 April 2014. dead. https://web.archive.org/web/20140717023500/http://www.solarimpulse.com/timeline/view/7401. 17 July 2014. dmy-all.
  19. Web site: Peter Diamandis our New Patron. Solar Impulse. Viktoria. Dijakovic. 10 October 2013. 22 March 2015. dead. https://web.archive.org/web/20141216143328/http://www.solarimpulse.com/timeline/view/7292. 16 December 2014. dmy-all.
  20. Web site: Solar Impulse – Around the world in a solar airplane. SunPower. 24 January 2013. https://web.archive.org/web/20120503074601/http://global.sunpowercorp.com/about/sponsor/solar-impulse/. 3 May 2012. dead.
    and Web site: Dijakovic. Viktoria. Construction HB-SIB Solar Cells. Solar Impulse. 17 July 2012.
  21. Web site: Partners, Financing Structure. Solar Impulse. 25 February 2010. dead. https://web.archive.org/web/20110106124812/http://solarimpulse.com/common/documents/partner.php?lang=en&group=partner. 6 January 2011. dmy-all.
  22. Web site: Solar Impulse's troubled round-the-world flight: 'We need to raise €20m'. The Guardian. Joshi . Herrmann. 27 July 2015. 28 July 2015 .
  23. Al Wasmi, Naser. "Exclusive: Solar Impulse headed back to Abu Dhabi the long way round", The National, 8 January 2016
  24. Solar Impulse. 2020. Solar Impulse - Around The World To Promote Clean Technologies. [online] Available at: [Accessed 10 March 2020].
  25. Web site: Lipsey, Sid. Secrets of the Solar-Powered Plane That Might Make History. Yahoo. 4 February 2015. 22 March 2015.
  26. Web site: Across America. Solar Impulse. 2013. 13 June 2013. dead. https://web.archive.org/web/20130629085555/http://www.solarimpulse.com/en/across-america/. 29 June 2013. dmy-all.
  27. News: Engeler. Eliane. Solar plane lands after completing 24-hour flight. Associated Press. 8 July 2010. 27 May 2015. dead. https://web.archive.org/web/20150527103858/http://www.businessweek.com/ap/financialnews/D9GQS2FG2.htm. 27 May 2015. dmy-all.
  28. Web site: Plane. 18 June 2011. Solar Impulse. dead. https://web.archive.org/web/20110628112009/http://solarimpulse.com/common/documents/challenge_solar.php?lang=en&group=challenge. 28 June 2011. dmy-all.
  29. Web site: Description of HB-SIA. SolarImpulse.com. 22 June 2010. 9 July 2010. dead. https://web.archive.org/web/20110726022519/http://www.solarimpulse.com/common/documents/blog.php?lang=en&group=media&id=105&comment=visible. 26 July 2011. dmy-all.
  30. News: Record solar plane's first 'hop'. 3 December 2009. BBC. 4 December 2009. Jason. Palmer.
  31. Web site: Solar-powered piloted plane makes its first 'flea hop'. Tom. Simonite. 3 December 2009. New Scientist. 5 December 2009.
  32. News: Swiss team makes 1st test flight of prototype for round-the-world solar flight. Los Angeles Times. 1 July 2010. 9 July 2010.
  33. Solar Airplane Completes Maiden Voyage. Wired. 7 April 2010. 9 July 2010.
  34. Web site: Solar Impulse Flies on Pure Sunlight. 3 June 2010. Grady. Mary. May 2010. https://web.archive.org/web/20100604034523/http://www.avweb.com/avwebflash/news/SolarImpulseFliesOnPureSunlight_202647-1.html. 4 June 2010. dead. dmy-all.
  35. News: Maron. Dina Fine. Swiss Team to Launch Solar Night Flight. The New York Times. ClimateWire. 6 July 2010. 8 July 2010.
  36. News: Solar Impulse completes record-breaking flight. https://web.archive.org/web/20100709160249/http://www.telegraph.co.uk/earth/energy/solarpower/7878526/Solar-Impulse-completes-record-breaking-flight.html. dead. 9 July 2010. The Daily Telegraph. 8 July 2010. 8 July 2010. London.
  37. Paur. Jason. Solar Airplane to Fly Through the Night (Tonight!). Wired. 7 July 2010. 8 July 2010.
  38. News: van Loon. Jeremy. Solar-Powered Plane Lands Safely After Overnight Flight. Bloomberg BusinessWeek. 8 July 2010. 8 July 2010. dead. https://web.archive.org/web/20100713014428/http://news.businessweek.com/article.asp?documentKey=1377-a4lM164962iU-6B58GM9T9AIUVKONT5V3EIC6KO. 13 July 2010. dmy-all.
  39. News: Solar-powered plane lands safely after 26-hour flight. BBC. 8 July 2010. 8 July 2010.
  40. News: Solar-Powered Plane Flies for 26 Hours. 8 July 2010. The New York Times. Alan. Cowell. 8 July 2010.
  41. Web site: The FAI ratifies Solar Impulse's World Records. 22 October 2010. dead. https://web.archive.org/web/20120127143011/http://www.fai.org/news-of-records/35101-the-fai-ratifies-solar-impulses-world-records. 27 January 2012. dmy-all.
  42. Web site: Solar Impulse: Premier vol international réussi pour l'avion solaire. Planet Techno Science. 14 May 2011. 15 June 2013. fr.
  43. News: Solar-Powered Airplane Makes Historic Flight. https://archive.today/20120709112224/http://blogs.forbes.com/oshadavidson/2011/05/13/breaking-solar-airplane-about-to-make-historic-landing.html. dead. 9 July 2012. 13 May 2011. Forbes. Osha Gray. Davidson. 13 May 2011.
  44. News: Solar Impulse Crosses Border. 16 May 2011. Niles. Russ. May 2011. AvWeb. https://web.archive.org/web/20110519092326/http://www.avweb.com/avwebflash/news/Solar_Impulse_Crosses_Borders_204657-1.html. 19 May 2011. dead. dmy-all.
  45. News: A setback for Solar Impulse: the solar plane favours safety and heads back to Brussels. 15 June 2011. June 2011. dead. https://web.archive.org/web/20110726022858/http://www.solarimpulse.com/common/documents/news_affich.php?lang=en&group=news&IdArticle=90. 26 July 2011. dmy-all.
  46. News: Solar Impulse Plane: A Rare Treat For Crowds in Paris. https://archive.today/20120723122419/http://tv.ibtimes.com/solar-impulse-plane-a-rare-treat-for-crowds-in-paris/890.html. dead. 2012-07-23. 15 June 2011. Marisa. Krystian. June 2011.
  47. Web site: Solar plane completes maiden intercontinental trip. Reuters. 5 June 2012. 6 June 2012.
  48. http://www.solarimpulse.com/timeline/view/6636/en Solar Impulse’s HB-SIA obtains two new world records
  49. Web site: Solar Impulse lands in St Louis in trans-America bid. BBC. 4 June 2013. 13 June 2013.
  50. Web site: Two hops for trans-US solar plane. BBC. 14 June 2013. 14 June 2013.
  51. Web site: Trans-US solar plane reaches Dulles. BBC. 16 June 2013. 16 June 2013.
  52. Web site: Solar Powered Plane Finishes Journey, Lands in NYC. Associated Press. 7 July 2013. 7 July 2013.
  53. Web site: Solar plane leaves Calif. on cross-country trip. Daytona Beach News Journal. 3 May 2013.
  54. Web site: Solar plane completes 2nd leg of trip in Texas. Associated Press. 23 May 2013. 10 July 2013.
    Web site: Solar Plane Completes Longest Leg of Cross-Country Flight. Yahoo News. 23 May 2013. 10 July 2013. ; Web site: FAI Record ID #16815 – Straight distance, pre-declared waypoints. FAI. 9 July 2013. dead. https://web.archive.org/web/20131104130238/http://www.fai.org/fai-record-file/?recordId=16815. 4 November 2013. dmy-all. ; Web site: FAI Record ID #16817 – Free Distance. FAI. 9 July 2013. dead. https://web.archive.org/web/20131104130334/http://www.fai.org/fai-record-file/?recordId=16817. 4 November 2013. dmy-all. ; and Web site: FAI Record ID #16816 – Distance along a course, pre-declared waypoints. FAI. 9 July 2013. dead. https://web.archive.org/web/20131104130155/http://www.fai.org/fai-record-file/?recordId=16816. 4 November 2013. dmy-all.
  55. Web site: Across America Event Summary. Solar Impulse. 9 March 2015.
  56. All start times are given as UTC, and all start dates are 2013.
  57. Web site: Solar Impulse 1 s'expose. 21 January 2019.
  58. Sport Aviation. July 2014. 14. First Flight for Solar Impulse 2.
  59. News: Solar-powered Swiss plane attempts flight around world. 9 March 2015. Al Jazeera. 26 July 2016.
  60. News: Solar Impulse 2 lands in Egypt in penultimate stop of its world tour. The Guardian. 13 July 2016. 26 July 2016.
  61. Reisinger, Don. "Solar-powered plane embarks on longest leg of round-the-world flight", CNET, 29 June 2015
  62. Paur. Jason. After 60 Hours in Cockpit, Pilot of Solar Impulse Feels 'Better Than Expected'. 2012-02-23. Wired. 2020-02-17. 1059-1028.
  63. Web site: Solar plane makes inaugural flight. BBC. 2 June 2014. 2 June 2014.
  64. News: Aviation Week & Space Technology. Solar Impulse Flies Aircraft For Round-the-World Attempt. 9 June 2014. 14.
  65. http://www.solarimpulse.com/en/airplane/hb-sib Timeline: "Without a spar, what's next?"
  66. Web site: Our Adventure. Solar Impulse. 19 January 2015. dead. https://web.archive.org/web/20150120193029/http://www.solarimpulse.com/en/our-adventure/the-first-round-the-world-solar-flight/. 20 January 2015. dmy-all.
  67. Web site: Schreck, Adam. Solar plane pioneers lay out round-the-world flight plan. Associated Press. 20 January 2015. 21 January 2015. dead. https://web.archive.org/web/20150120203222/http://finance.yahoo.com/news/solar-plane-pioneers-lay-round-world-flight-plan-080306681.html. 20 January 2015. dmy-all.
  68. Web site: Solar Impulse launches Mission Control Center in Monaco. ABB Conversations. 23 February 2015. 21 March 2015.
  69. Web site: Mudallal, Zainab. This solar-powered airplane is about to take its first around-the-world flight. Quartz. 16 January 2015. 19 January 2015.
  70. https://www.bbc.com/news/science-environment-36122618 "Solar Impulse lands in California after Pacific crossing"
  71. Molko, David. "Solar-powered plane on round-the-world flight gets stuck in China", CNN, 17 April 2015
  72. Web site: Keyrouz, Wissam. Solar plane revs up for historic round-the-world flight. AFP via Yahoo. 7 March 2015. 22 March 2015.
  73. Amos, Jonathan. "Solar Impulse plane begins Pacific crossing", BBC News, 31 May 2015
  74. Randall, Tom. "This Plane Runs on Sun and Is About to Smash Some Records", Bloomberg L.P., 15 June 2015
  75. [Rebecca Morelle|Morelle, Rebecca]
  76. Archangel, Amber.News: Solar Impulse Sets World Record: 117 Hours & 52 Minutes – Longest Solo Flight Ever . . 6 July 2015.
  77. The Fédération Aéronautique Internationale (FAI) website states that the "Free distance along course" was 7,039.9 km. FAI Record ID #17595, Fédération Aéronautique Internationale. Retrieved 29 July 2015
  78. The FAI does not record this record as official, since the FAI does not have an "any aircraft" category. See "FAI records page", Fédération Aéronautique Internationale, 29 July 2015
  79. Amos, Jonathan. "Solar Impulse grounded until 2016", BBC, 15 July 2015
  80. Molko, Davis. "Solar Impulse: Plane's pilots ground record-setting attempt until 2016", CNN, 15 July 2015
  81. http://phys.org/news/2016-02-solar-impulse-plane-maintenance-flight.html "Solar Impulse plane makes first maintenance flight in Hawaii"
  82. Al Wasmi, Naser. "After months-long hiatus, Solar Impulse 2 gets set to fly again", The National, 11 March 2016
  83. Delony, Jennifer. "Solar Impulse Live: Solar Airplane Pilot Gives Interview While Flying from Hawaii to California", RenewableEnergyWorld.com, 22 April 2016
  84. Morosini, Marco. "A majestic solar dragonfly landed in San Francisco – Is this the future?", The Huffington Post, 28 April 2016; and "Live conversation between UN Secretary-General Ban Ki-moon & Bertrand Piccard", Solar Impulse, YouTube, 22 April 2016
  85. News: Solar Impulse aeroplane reaches Phoenix, Arizona . 2 May 2016 . Jonathan . Amos. BBC News .
  86. Web site: Solar Airplane Lands in Phoenix After Flight From Silicon Valley . Bill . Chappell . 3 May 2016 . 5 May 2016 . NPR.
  87. Ryburn, Stacy. "Solar plane lands at Tulsa International Airport", Tulsa World, 12 May 2016
  88. http://www.nbcnews.com/tech/innovation/solar-impulse-2-lands-ohio-complete-latest-leg-global-trip-n578171 "Solar Impulse 2 Lands in Ohio to Complete Latest Leg of Global Trip"
  89. http://www.nbcnews.com/tech/innovation/solar-impulse-2-lands-pennsylvania-latest-leg-global-journey-n580576 "Solar Impulse 2 Lands in Pennsylvania in Latest Leg of Global Journey"
  90. Rice, Doyle. "Solar Impulse 2 lands in New York City, final U.S. destination", USA Today, 11 June 2016
  91. All start times are given as UTC. All start dates for legs 1 to 8 are 2015; start dates for legs 9 to 17 are 2016.
  92. Web site: Leg 1: Abu Dhabi to Muscat . Solar Impulse.
  93. Solar Impulse team records the distance as 1,593 km. The FAI website states that the "Straight Distance – pre-declared waypoints" was 1,468 km. FAI "Record ID #17429", Fédération Aéronautique Internationale. Retrieved 1 August 2015
  94. Web site: Leg 2: Muscat to Ahmedabad . Solar Impulse.
  95. Web site: Leg 3: Ahmedabad to Varanasi . Solar Impulse.
  96. Web site: Leg 4; Varanasi to Mandalay . Solar Impulse.
  97. Web site: Leg 5: Mandalay to Chongqing . Solar Impulse.
  98. Web site: Leg 6: Chongqing to Nanjing . Solar Impulse.
  99. http://www.solarimpulse.com/leg-7-from-Nanjing-to-Nagoya "Leg 7: Nanjing to Nagoya"
  100. The FAI website states that the "Free distance along course" was 2614.5 km. FAI "Record ID #17558", Fédération Aéronautique Internationale. Retrieved 29 July 2015
  101. http://www.solarimpulse.com/leg-8-from-Nagoya-to-Hawaii "Leg 8: Nagoya to Hawaii"
  102. Web site: Leg 9: Hawaii to Mountain View . Solar Impulse . 21 April 2016 . dead . https://web.archive.org/web/20160424075146/http://www.solarimpulse.com/leg-9-from-Hawaii-to-Mountain_View_CA . 24 April 2016 . dmy-all .
  103. Web site: Leg 10: San Francisco to Phoenix. Solar Impulse . 2 May 2016.
  104. Web site: Leg 11: Phoenix to Tulsa . Solar Impulse.
  105. Web site: Leg 12: Tulsa to Dayton . Solar Impulse.
  106. Web site: Leg 13: Dayton to Lehigh Valley . Solar Impulse.
  107. Web site: Leg 14: Lehigh Valley to New York . Solar Impulse.
  108. Web site: Leg 15: New York to Seville . Solar Impulse.
  109. Web site: Leg 16: Seville to Cairo . Solar Impulse.
  110. http://www.solarimpulse.com/leg-17-from-Cairo-to-Abu_Dhabi "We Are in Abu Dhabi"
  111. News: Renfer . Marc . Dieuaide . Yann . Solar Impulse to be reborn as a military-linked project . November 23, 2020.
  112. News: Solar Impulse to start 'second life' in Spain . September 11, 2019.
  113. Lebleu . Tristan . A Second Life for the Solar Impulse (Si2) Airplane . Solar Impulse . September 11, 2019.
  114. News: Solar-Powered Skydweller Completes First Autonomous Flights . Graham Warwick . February 7, 2023 . Aviation Week.
  115. https://onlinecoin.club/Coins/Country/Switzerland/Twenty_Francs_2015_Solar_Impulse/ "Twenty Francs 2015 Solar Impulse"
  116. "La Poste rend hommage à « Solar Impulse 2 » avec un timbre commémoratif", press release of the Swiss Post published on 27 July 2016 (page visited on 7 September 2016).