“NASA's Pathfinder, Pathfinder Plus, Centurion and Helios Prototype were an evolutionary series of solar- and fuel-cell-system-powered unmanned aerial vehicles. AeroVironment, Inc. developed the vehicles under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program. They were built to develop the technologies that would allow long-term, high-altitude aircraft to serve as “atmospheric satellites”, to perform atmospheric research tasks as well as serve as communications platforms”. – Wikipedia

Photo: The solar-electric Helios Prototype flying wing is flies over the Hawaiian islands of Niihau and Lehua during the first solar-powered test flight July 14, 2001 from the U.S. Navy's Pacific Missile Range Facility on Kauai, HI. The 18-hour flight was a functional checkout of the aircraft's systems and performance in preparation for an attempt to reach sustained flight at 100,000 feet altitude later in the summer. (Photo Courtesy of NASA/Getty Images)

A Buddhist monk salvages a statue of a Buddhist deity from a monastery around the famous Swayambhunath stupa after it was damaged by Saturday's earthquake in Kathmandu, Nepal, Thursday, April 30, 2015. In mere seconds, Saturday's earthquake devastated a swathe of Nepal. Three of the seven World Heritage sites in the Kathmandu Valley have been severely damaged, including Durbar Square with pagodas and temples dating from the 15th to 18th centuries, according to UNESCO, the United Nations cultural agency. (Photo by Niranjan Shrestha/AP Photo)

A woman takes cover as shots are fired by police officers as they face off with stone-throwing protesters, during an anti-government demonstration in Bujumbura, Burundi, 20 May 2015. Police officers fired shots and teargas canisters in running battles with protesters who demonstrated against Burundi's President Pierre Nkurunziza's bid for a third term. Presidential spokesman man said on 20 May that the country will postpone its parliamentary and local council elections, previously scheduled for 26 May, to 05 June 2015. According to the United Nations' refugee agency, more than 105,000 Burndians have fled the country to seek refuge in neighbouring countries such as Rwanda, DR Congo, and Tanzania. (Photo by Dai Kurokawa/EPA)

In this June 29, 2015 photo, forlorn buildings are seen at Hashima Island, commonly known as Gunkanjima, which means “Battleship Island”, off Nagasaki, Nagasaki Prefecture, southern Japan. The island is one of 23 old industrial facilities seeking UNESCO's recognition as world heritage “Sites of Japan's Meiji Industrial Revolution” meant to illustrate Japan's rapid transformation from a feudal farming society into an industrial power at the end of the 19th century. UNESCO's World Heritage Committee is expected to approve the proposal during a meeting being held in Bonn, Germany, through July 9. (Photo by Eugene Hoshiko/AP Photo)

In this June 16, 2015 photo, an Indian coachman sleeps on his Victoria horse-drawn carriage outside a stable in Mumbai, India. Drivers of Mumbai's iconic horse-drawn carriages can't imagine not plying the roads pulling photo-snapping tourists atop their kitsch-covered chariots. Yet that time is coming, thanks to a court order calling such superfluous “joyrides” a form of animal cruelty and banning them in India's financial capital from June 2016. (Photo by Rafiq Maqbool/AP Photo)

Patients from the Larco Herrera Psychiatric Hospital wear costumes in the likeness of the first governor and founder of the Inca civilization, Manco Capac, right, and his wife Mama Ocllo, during the hospital's Independence Day parade in Lima, Peru, Wednesday, July 22, 2015. The parade is held on the hospital's campus every year ahead of the Andean nation's official Independence Day celebrations on July 28. (Photo by Martin Mejia/AP Photo)

Fishermen jump into a small river to catch trout as they celebrate Fischertag (Fisherman's Day) in downtown Memmingen, southern Germany, July 25, 2015. The annual Fisherman's Day (Fischertag) tradition goes back to the year of 1465 where every fisherman who were born in Memmingen tries to catch trout from the river. The participant who catches the biggest trout will be named the “Fisher King” for one year. (Photo by Michaela Rehle/Reuters)

The moon rises over people gathered on Glastonbury Tor ahead of tomorrow's Blue Moon on July 30, 2015 in Somerset, England. The full moon appearing on July 31 will be what's called a Blue Moon, which refers to the second of two full moons appearing in the same calendar month. The last time this happened was in 2012 and there isn't due another until 2018. (Photo by Matt Cardy/Getty Images)