“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 man takes a picture of part of what is set to be the UK's largest street art project on August 19, 2011 in Bristol, England. The See No Evil art project on Nelson Street in Bristol will see several multi story buildings in the street covered with art over the coming days. Organisers hope that the project, which has involved top graffiti artists from all over the world, will become a major tourist attraction for the west country city, often said to the spiritual home of Banksy. (Photo by Matt Cardy/Getty Images)

A female participant armed with a bottle of ketchup attacks in the annual Vegetable Battle in Kreuzberg district near Oberbaumbruecke Bridge on August 28, 2011 in Berlin, Germany. The event pits Kreuzberg district residents againts Friedrichshain district residents for control of the Oberbaumbruecke, and the two sides pelt each other with rotten vegetables, other foods, ketchup, water guns and styrofoam bats until one side has pushed the other from the bridge. The event had originally been cancelled for today, but so many participants showed up anyway and began battling on the Kreuzberg side, where the situation escalated and began to threaten traffic, that police relented and let them later battle it out on the bridge. Kreuzberg claimed victory. (Photo by Sean Gallup/Getty Images)

Beluga the bog poses as Britney Spears during the 17th annual Tompkins Square Halloween Dog Parade October 28, 2007 in New York City. The event is the largest dog Halloween party in the United States with an annual attendance of over 400 costumed dogs. (Photo by Mario Tama/Getty Images)

“Self-educated photographer, Quebec. I always impassioned myself for the animal world and natural spaces, in particular for the red squirrels and the titmouses. Having reached sixty and more, I am nothing any more has to prove but all has to show”. – Andre Villeneuve. Photo: “Eat and run”. (Photo by Andre Villeneuve)

Francis Sierra, 23, smokes as she competes for the longest ash during the XVIII Habanos Festival in Havana, March 3, 2016. (Photo by Alexandre Meneghini/Reuters)

Medics carry an injured at the explosion site in the busy center of Turkish capital, Ankara, Turkey, Sunday, March 13, 2016. The explosion is believed to have been caused by a car bomb that went off close to bus stops. News reports say the large explosion in the capital has caused several deaths and many casualties. (Photo by AP Photo)

Student, Shoukria positions a stone for cutting at the Turquoise Mountain Gem cutting class on May 18, 2011, in Kabul, Afghanistan. The mineral resources of Afghanistan are relatively unexplored even with Afghanistan's mineral wealth of coal, copper, gold and iron ore, with precious and semiprecious stones, including high-quality emerald, lapis lazuli, red garnet and ruby. Given the country's remote and rugged terrain, on-going instability plus an inadequate infrastructure and transportation means that mining is still difficult. While many are trying to bring positive changes, Afghanistan's mining industry uses unregulated, primitive methods and outdated equipment. (Photo by Paula Bronstein/Getty Images)