| Solar Impulse | |
|---|---|
 Solar Impulse 1 landing atBrussels Airport after its first international flight on 13 May 2011 | |
| General information | |
| Type | Experimentalsolar-powered aircraft |
| National origin | Switzerland |
| Manufacturer | Solar Impulse |
| Primary user | André Borschberg andBertrand Piccard |
| Number built | 2 (including prototype) |
| History | |
| Manufactured | 2009–present |
| First flight | 3 December 2009 |
Solar Impulse is a Swiss long-rangeexperimentalsolar-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 businessmanAndré Borschberg and Swiss psychiatrist and balloonistBertrand Piccard, who co-pilotedBreitling Orbiter 3, the firstballoon to circle the world non-stop.[2] The Solar Impulse project's goals were to make the firstcircumnavigation of the Earth by a pilotedfixed-wing aircraft using only solar power and to bring attention toclean technologies.[3]
The aircraft is a single-seatedmonoplane powered byphotovoltaic cells; it is capable of taking off under its own power. The prototype, often referred to asSolar 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 entirediurnal 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,[6] and conducted a multi-stage flight across the US in 2013.[7][8]
A second aircraft, completed in 2014 and namedSolar 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 withSolar Impulse 2, departing fromAbu Dhabi in the United Arab Emirates.[9] The aircraft was scheduled to return to Abu Dhabi in August 2015 after a multi-stage journey around the world.[10] By June 2015, the plane had traversed Asia,[11] and in July 2015, it completed thelongest leg of its journey, from Japan to Hawaii.[12] During that leg, the aircraft's batteries sustained thermal damage and took months to replace.[13]
A battery cooling system was installed andSolar Impulse 2 resumed the circumnavigation in April 2016, when it flew on to California.[14][15] It continued across the US until it reached New York City in June 2016.[16] Later that month, the aircraft crossed the Atlantic Ocean toSeville, Spain.[17] 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 km (26,000 mi) first circumnavigation of the Earth by a piloted fixed-wing aircraft using only solar power.[18][19]
In 2019, theSolar Impulse 2 was sold to Skydweller Aero, a US-Spanish company using the airframe to develop autonomousunmanned aerial vehicles capable of perpetual flight.[20] It plans to use the aircraft for research and development and flight testing, after which theSolar Impulse 2 will be returned for permanent display at theSwiss Museum of Transport.
Bertrand Piccard initiated the Solar Impulse project in November 2003 after undertaking a feasibility study in partnership with theÉcole Polytechnique Fédérale de Lausanne (EPFL).[21] As a mechanical engineer, co-founderAndré Borschberg directed the construction of each aircraft and oversees the preparation of the flight missions.[22] 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.[23][24]
The project is financed by a number of private companies and individuals, as well as receiving aroundCHF 6 million (US$6.4 million) in funding from the Swiss government.[25] The project's private financial backers includeOmega SA,Solvay,Schindler,ABB[26] andPeter Diamandis.[27] TheEPFL, theEuropean Space Agency andDassault have provided technical expertise, whileSunPower provided the aircraft's photovoltaic cells.[28][29]
Piccard stated that the entire project from its beginnings in 2003 until mid-2015 had cost €150 million.[30] It raised another €20 million in late 2015 to continue the round-the-world flight.[31]
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 theAirbus A340 airliner. Under the wing are fournacelles, each with a set oflithium polymer batteries, a 7.5 kW (10 hp) electric motor and one twin-bladed propeller. To keep the wing as light as possible, a customisedcarbon fibre honeycomb sandwich structure was used.[34] 11,628photovoltaic 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.[35][36]
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 6 kW (8 hp), roughly the power used by theWright brothers'Flyer, the first successful powered aircraft, in 1903.[34] In addition to the charge stored in its batteries, the aircraft uses thepotential energy of height gained during the day to power its night flights.[37]
Data from Solar Impulse Project[34]and Diaz[38]
General characteristics
Performance
On 26 June 2009,Solar Impulse 1 was first presented to the public at theDübendorf Air Base, Switzerland. Following taxi testing, a short-hop test flight was made on 3 December 2009,[39] piloted by Markus Scherdel.[40] Borschberg, co-leader of the project team, said of the flight:
"It was an unbelievable day. The airplane flew for about 350 metres (1,150 ft) and about 1 metre (3 ft 3 in) above the ground ... The aim was not to get high but to land on the same runway at a speed to test its controllability and get a first feeling of its flying characteristics ... the craft behaved just as the engineers had hoped. It is the end of the engineering phase and the start of the flight testing phase."[40]
On 7 April 2010, the plane conducted an 87-minute test flight, piloted by Markus Scherdel. This flight reached an altitude of 1,200 m (3,937 ft).[41][42] On 28 May 2010, the aircraft made its first flight powered entirely by solar energy, charging its batteries in flight.[43]
On 8 July 2010,Solar Impulse 1 achieved the world's first manned 26-hour solar-powered flight.[44][45][46] The airplane was flown by Borschberg, and took off at 06:51Central European Summer Time (UTC+2) on 7 July fromPayerne Air Base, Switzerland. It returned for a landing the following morning at 09:00 local time.[47] During the flight, the plane reached a maximum altitude of 8,700 m (28,500 ft).[48] At the time, the flight was the longest and highest ever flown by a manned solar-powered aircraft; these records were officially recognized by theFédération Aéronautique Internationale (FAI) in October 2010.[49][50]
On 13 May 2011 at 21:30 local time, the plane landed atBrussels 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 1,800 m (6,000 ft) for a distance of 630 km (391 mi), with an average speed of 50 km/h (31 mph). The aircraft's slow cruising speed required operating at a mid-altitude, allowing much faster air traffic to be routed around it.[51] 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."[52][53]
A second international flight to theParis Air Show was attempted on 12 June 2011, but the plane turned back and returned to Brussels because of adverse weather conditions.[54] In a second attempt on 14 June, Borschberg successfully landed the aircraft at Paris'Le Bourget Airport after a 16-hour flight.[55]
On 5 June 2012, the Solar Impulse successfully completed its first intercontinental flight, a 19-hour trip fromMadrid, Spain, toRabat, Morocco.[6] During the first leg of the flight fromPayerne Air Base to Madrid, the aircraft broke several further records for solar flight, including the longest solar-powered flight between pre-declared waypoints (1,099.3 km or 683 mi) and along a course (1,116 km or 693 mi).[56]
On 3 May 2013, the plane began its cross-US flight with a journey fromMoffett Field inMountain View, California, toPhoenix Goodyear Airport in Arizona. Successive legs of the flight ended atDallas-Fort Worth airport,Lambert–St. Louis International Airport,[57]Cincinnati Municipal Lunken Airport to change pilots and avoid strong winds,[58] andWashington Dulles International Airport.[59] 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.[8][60] The landing occurred three hours earlier than originally intended, because a planned flyby of theStatue of Liberty was cancelled as a result of damage to the covering on the left wing.[8]
Each flight leg took between 14 and 22 hours.[7][61] The aircraft's second leg of its trip on 23 May to Dallas-Fort Worth covered 1,541 kilometres (958 mi) and set several new world distance records in solar aviation.[62]Solar Impulse 1 was placed on public display at JFK after its landing. In August 2013, it was disassembled, then transported via aCargolux B-747-400F toDübendorf Air Base, where it was placed in storage in a hangar.
Source:[63]
| Leg | Start[64] | Stop | Origin | Destination | Distance | Flight time | Avg. speed | Pilot |
|---|---|---|---|---|---|---|---|---|
| 1 | 3 May 14:12 | 4 May 08:30 | Moffett Field, California (KNUQ) | Phoenix, Arizona (KGYR) | 984 km | 18 h 18 min | 53 km/h | Bertrand Piccard |
| 2 | 22 May 12:47 | 23 May 07:08 | Phoenix, Arizona (KGYR) | Dallas, Texas (KDFW) | 1541 km | 18 h 21 min | 84 km/h | André Borschberg |
| 3 | 3 Jun 10:06 | 4 Jun 07:28 | Dallas, Texas (KDFW) | Saint Louis, Missouri (KSTL) | 1040 km | 21 h 22 min | 49 km/h | Bertrand Piccard |
| 4 | 14 Jun 11:01 | 15 Jun 02:15 | Saint Louis, Missouri (KSTL) | Cincinnati, Ohio (KLUK) | 15 h 14 min | André Borschberg | ||
| 5 | 15 Jun 15:10 | 16 Jun 05:15 | Cincinnati, Ohio (KLUK) | Washington, DC (KIAD) | 14 h 5 min | Bertrand Piccard | ||
| 6 | 6 July 09:56 | 7 July 05:15 | Washington, DC (KIAD) | New York City, New York (KJFK) | 19 h 19 min | André Borschberg |
In March 2015, the plane was transported by truck to Paris to be part of the permanent exhibition atCité des Sciences et de l'Industrie.[65]
Construction started in 2011 on the second aircraft, known asSolar 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 mainspar during static tests in July 2012, leading to delays in the flight testing schedule to allow repairs.Solar Impulse 2's first flight took place atPayerne Air Base on 2 June 2014.[66]
The wingspan ofSolar Impulse 2 is 71.9 m (236 ft), slightly less than that of anAirbus A380, the world's largest passengerairliner,[38] but compared with the 500-tonne A380,[67] the carbon-fibre Solar Impulse weighs only about 2.3 tonnes (5,100 lb), little more than an averageSUV.[68] It features a non-pressurized cockpit 3.8 cubic metres (130 cu ft) in size[69] and advancedavionics, including limited functionality of anautopilot that allows the pilot to sleep for up to 20 minutes at a time,[70] enabling multi-day transcontinental and trans-oceanic flights.[23]Supplemental oxygen and various other environmental support systems allow the pilot to cruise up to an altitude of 12,000 metres (39,000 ft).[38]
Data from Solar Impulse Project[24]
General characteristics
Performance
Solar Impulse 2 was first publicly displayed on 9 April 2014.[24] Its inaugural flight took place on 2 June 2014, piloted by Markus Scherdel.[71] The aircraft averaged aground speed of 30 knots (56 km/h), and reached an altitude of 1,700 metres (5,500 ft).[72] The first night flight was completed on 26 October 2014, and the aircraft reached its maximum altitude during a flight on 28 October 2014.
The repair work to the aircraft's main spar delayedSolar Impulse 2's circumnavigation of the Earth from 2012 to 2015.[73] The aircraft was delivered toMasdar City in Abu Dhabi for theWorld Future Energy Summit in late January 2015,[74] and it began the journey fromAl Bateen Executive Airport on 9 March 2015.[9][75] It was scheduled to return to the same location in August 2015.[10][76] A mission control centre for the circumnavigation was established inMonaco, using satellite links to gather real-time flight telemetry and remain in constant contact with the aircraft and the support team.[77] The route followed bySolar Impulse 2 was entirely in theNorthern Hemisphere. It left Abu Dhabi, then it headed east to nearby Oman and India.[76][78] 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.[79] For most of its time airborne,Solar Impulse 2 cruised at a ground speed of between 50 and 100 kilometres per hour (31 and 62 mph), 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.[10][80] On multi-day flights, the pilots took 20-minute naps and used yoga or other exercises to promote blood flow and maintain alertness.[69]
By the end of May 2015, the plane had traversed Asia.[81] 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.[11][82] The aircraft began the flight from Japan to Hawaii on 28 June 2015 (29 June, Japan local time).[83] 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 forlongest solo flight, by time, for any aircraft.[12][84][85] 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. TheUS Department of Transportation stored the aircraft in a hangar atKalaeloa Airport onOahu.[86][87] New batteries were made and installed in the plane. Test flights began in February 2016[88] to prepare for resumption of the circumnavigation once northern hemisphere days lengthened enough to permit multi-day solar-powered flights.[13][31] A favourable weather window opened in April 2016, and the plane resumed its journey,[14][89] landing atMoffett Field, in California, on 23 April.[15] During that flight, Piccard, via a live videolink, spoke withBan Ki-moon andDoris Leuthard before theGeneral Assembly of the United Nations, from the cockpit ofSolar Impulse 2, commenting on that day's historic signing of theParis Agreement and discussing how using clean technologies can create jobs and fightglobal warming.[90] Additional legs of the flight were added in the US asSolar Impulse 2 flew to Phoenix, Arizona,[91][92]Tulsa, Oklahoma,[93]Dayton, Ohio,[94]Lehigh Valley, Pennsylvania[95] and New York City, arriving there on 11 June 2016.[16] Piccard piloted the aircraft across the Atlantic Ocean, arriving inSeville, Spain, on 23 June.[17] The aircraft next stopped inCairo, Egypt, on 13 July,[18] 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.[19]
| Leg | Start[96] | Origin | Destination | Flight time | Distance | Avg. speed | Max. altitude | Pilot |
|---|---|---|---|---|---|---|---|---|
| 1 | 9 March 2015 03:12 |  Abu Dhabi,UAE (OMAD) |  Muscat, Oman (OOMS) | 13 h 1 min | 417 nmi (772 km) | 32.0 kn (59.2 km/h) | 20,942 ft (6,383 m) | A. Borschberg[97] |
| 2 | 10 March 02:35 | Muscat, Oman (OOMS) |  Ahmedabad, India (VAAH) | 15 h 20 min | 860 nmi (1,593 km)[98] | 56.1 kn (103.9 km/h) | 29,114 ft (8,874 m) | B. Piccard[99] |
| 3 | 18 March 01:48 | Ahmedabad, India (VAAH) | Varanasi, India (VEBN) | 13 h 15 min | 630 nmi (1,170 km) | 47.7 kn (88.3 km/h) | 17,001 ft (5,182 m) | Borschberg[100] |
| 4 | 18 March 23:52 | Varanasi, India (VEBN) |  Mandalay,Myanmar (VYMD) | 13 h 29 min | 829 nmi (1,536 km) | 61.5 kn (113.9 km/h) | 27,000 ft (8,230 m) | Piccard[101] |
| 5 | 29 March 21:06 | Mandalay,Myanmar (VYMD) |  Chongqing, China (ZUCK) | 20 h 29 min | 883 nmi (1,636 km) | 43.1 kn (79.9 km/h) | 28,327 ft (8,634 m) | Piccard[102] |
| 6 | 20 April 22:06 | Chongqing, China (ZUCK) | Nanjing, China (ZSNJ) | 17 h 22 min | 747 nmi (1,384 km) | 43.0 kn (79.7 km/h) | 14,010 ft (4,270 m) | Piccard[103] |
| 7 | 30 May 18:39 | Nanjing, China (ZSNJ) |  Nagoya, JapanN1 (RJNA) | 44 h 9 min | 1,589 nmi (2,942 km) | 36.0 kn (66.6 km/h) | 28,327 ft (8,634 m) | Borschberg[11][104] |
| 8 | 28 June 18:03 | Nagoya, Japan (RJNA) |  Kalaeloa, Hawaii, US (PHJR) | 117 h 52 min | 4,819 nmi (8,924 km) | 40.9 kn (75.7 km/h) | 28,327 ft (8,634 m) | Borschberg[84][105] |
| 9 | 21 April 2016 16:15 | Kalaeloa, Hawaii, US (PHJR) | Mountain View, CA, US (KNUQ) | 62 h 29 min | 2,206 nmi (4,086 km) | 35.3 kn (65.4 km/h) | 28,327 ft (8,634 m) | Piccard[14][106] |
| 10 | 2 May 12:03 | Mountain View, CA, US (KNUQ) | Phoenix, AZ, US (KGYR) | 15 h 52 min | 601 nmi (1,113 km) | 37.9 kn (70.2 km/h) | 22,001 ft (6,706 m) | Borschberg[107] |
| 11 | 12 May 11:05 | Phoenix, AZ, US (KGYR) | Tulsa, OK, US (KTUL) | 18 h 10 min | 850 nmi (1,570 km) | 46.7 kn (86.4 km/h) | 22,001 ft (6,706 m) | Piccard[108] |
| 12 | 21 May 09:22 | Tulsa, OK, US (KTUL) | Dayton, OH, US (KDAY) | 16 h 34 min | 647 nmi (1,199 km) | 39.1 kn (72.4 km/h) | 21,001 ft (6,401 m) | Borschberg[109] |
| 13 | 25 May 08:02 | Dayton, OH, US (KDAY) | Lehigh Valley, PA, US (KABE) | 16 h 49 min | 564 nmi (1,044 km) | 33.6 kn (62.2 km/h) | 15,000 ft (4,572 m) | Piccard[110] |
| 14 | 11 June 03:18 | Lehigh Valley, PA, US (KABE) | New York, NY, US (KJFK) | 4 h 41 min | 143 nmi (265 km) | 30.6 kn (56.6 km/h) | 3,002 ft (915 m) | Borschberg[111] |
| 15 | 20 June 06:30 | New York, NY, US (KJFK) |  Seville, Spain (LEZL) | 71 h 8 min | 3,653 nmi (6,765 km) | 50.9 kn (94.3 km/h) | 27,999 ft (8,534 m) | Piccard[112] |
| 16 | 11 July 04:20 | Seville, Spain (LEZL) |  Cairo,Egypt (HECA) | 48 h 50 min | 2,022 nmi (3,745 km) | 41.4 kn (76.7 km/h) | 27,999 ft (8,534 m) | Borschberg[113] |
| 17 | 23 July 2016 23:28 | Cairo,Egypt (HECA) | Abu Dhabi,UAE (OMAD) | 48 h 37 min | 1,455 nmi (2,694 km) | 29.9 kn (55.4 km/h) | 27,999 ft (8,534 m) | Piccard[114] |
| Total | 558 h 7 min (23.25 d) | 22,915 nmi (42,438 km) | 41.0 kn (76.0 km/h) | 29,114 ft (8,874 m) |
In September 2019 the Solar Impulse 2 aircraft was sold toSkydweller Aero, a Spanish-American company that is developing autonomousunmanned aerial vehicles capable of continuous flight and "carrying radar, electronic optics, telecommunications devices, telephone listening and interception systems".[115] 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 theSwiss Museum of Transport.[116][117] By February 2023, Skydweller Aero had conducted its firstautonomous flight in Spain before transferring the aircraft to southern Mississippi in 2024 where it conducted the world's first uncrewed autonomous flight of a solar aircraft.[118] The company intends to build a fleet of aircraft to operate year-round in latitudes betweenMiami (26°N) toRio de Janeiro (23°S).[119] Uncrewed and autonomous, these aircraft will be able to perform military missions and commercial tasks unachievable to manned aircraft and at far less cost than satellites.[120]
Skydweller Aero intends to fly an aircraft nonstop around the world in the coming years.[121]
In 2015,Swissmint issued a specialcommemorative coin in anticipation of the Earth circumnavigation mission.[122]
In 2016, theSwiss Post edited a specialstamp to honour the achievement ofSolar Impulse 2.[123]
