Workers install a monument inside Beirut port as a remembrance for the victims of the 04 August harbor blast in Beirut, Lebanon, 27 July 2021. A massive blast on 04 August 2020 rocked Beirut's port in which at least 200 people were killed and more than 6,000 injured, believed to have been caused by an estimated 2,750 tons of ammonium nitrate stored in a warehouse, devastated the port area of Beirut and several parts of the city. (Photo by Wael Hamzeh/EPA/EFE)

An employee walks near a rotary dredge which works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, December 9, 2014. The Borodinsky colliery, 9 km (5.6 miles) long and more than 100 meters (328 feet) deep, annually produces more than 20 million tons of coal and is considered to be the biggest opencast coal mine in Russia, according to official representatives. (Photo by Ilya Naymushin/Reuters)

A worker puts the final touches to a replica of a Beijing opera mask made with lemons and oranges during the 82th Lemon festival in Menton February 12, 2015. Over 20,000 hours work for teams to set up the festival and some 145 metric tons of lemons and oranges are used to make displays during the 82th festival, which is themed “Tribulations of a lemon in China”, and runs from February 14 through March 4. (Photo by Eric Gaillard/Reuters)

Master Sergey Suprun uses a portable radio set as he stands near a rotary dredge which works on the coal face of the Borodinsky opencast colliery, near the Siberian town of Borodino, east of Krasnoyarsk, Russia October 27, 2015. The Borodinsky colliery, 9 km (5.6 miles) long and more than 100 meters (328 feet) deep, annually produces more than 20 million tons of coal and is considered to be the biggest opencast coal mine in Russia, according to official representatives. (Photo by Ilya Naymushin/Reuters)

Flames rage through a pile of tires at the tire dump of Sesena in Toledo, Spain, 13 May 2016. The tire dump reportedly contains over 100,000 tons of tires and reaches to the neighbouring town of Valdemoro in Madrid. According to local authorities, the fire was apparently deliberately started as it had been raining till midnight and the fire started early 13 May 2016 at a small spot in Valdemoro. (Photo by Ismael Herrero/EPA)

Swiss pilot Bertrand Piccard prepares for a test flight of the solar-powered Solar Impulse 2 experimental aircraft in Payerne November 13, 2014. The aircraft, weighing 2.4 tons with a wingspan of 72 meters, is fitted with more than 17,000 solar cells. An attempt to fly around the world in stages using only solar energy will be made in 2015. (Photo by Ruben Sprich/Reuters)

Lebanese people take pictures for damaged grain silos in Beirut port following a huge explosion rocked the city in Beirut, Lebanon, 23 August 2020. According to Lebanese Health Ministry at least 181 people were killed, and more than 6,000 injured in the Beirut blast that devastated the port area on 04 August and believed to have been caused by an estimated 2,750 tons of ammonium nitrate stored in a warehouse. (Photo by Wael Hamzeh/EPA/EFE)

“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)