A prototype battery-powered plane, called Greased Lightning or GL-10 is pictured flying at NASA's Langley Research Center in this undated handout photo obtained by Reuters May 1, 2015. The plane, which has 10 engines and can take off like a helicopter and fly efficiently like an aircraft, is currently in the design and testing phase. (Photo by Reuters/NASA)

A young woman cools herself in a fountain in Budapest, Hungary July 6, 2015. Over the weekend, a heat wave has reached Hungary with temperatures topping 38 degrees Celsius (100.4 degrees Fahrenheit). (Photo by Laszlo Balogh/Reuters)

An officer wipes sweat off the face of a Chinese People's Liberation Army (PLA) honor guard soldier as they rehearse for a welcoming ceremony for New Zealand's Governor-General Sir Jerry Mateparae at the Great Hall of the People in Beijing, Tuesday, July 21, 2015. (Photo by Mark Schiefelbein/AP Photo)

This photograph released by Indian Space Research Organization shows its polar satellite launch vehicle lifting off from a launch pad at the Satish Dhawan Space Centre in Sriharikota, India, Wednesday, February 15, 2017. India's space agency said it successfully launched more than 100 foreign nano satellites into orbit Wednesday aboard a single rocket.(Photo by Indian Space Research Organization via AP Photo)

A man presents a self-made robot that local media reported is able to carry a person, in Heihe, Heilongjiang province, China, April 5, 2017. (Photo by Reuters/China Daily)

Revellers continue to party and dance through the night and day during the second day of the San Fermin Running Of The Bulls festival, on July 7, 2014 in Pamplona, Spain. The annual Fiesta de San Fermin, made famous by the 1926 novel of US writer Ernest Hemmingway “The Sun Also Rises”, involves the running of the bulls through the historic heart of Pamplona. (Photo by Christopher Furlong/Getty Images)

Soma-Nomaoi is a festival that recreates a battle scene from more than 1,000 years ago. It is annually held for 4 days from July 22 to 25 in Haramachi City, Fukushima Prefecture, in the eastern part of Japan. In this historical event, 600 mounted samurai in traditional Japanese armor, with long swords at their side and ancestral flagstaffs streaming from their backs, ride across open fields. Soma-Nomaoi has been designated an Important Intangible Folk Cultural Property.

Photo: A young woman (C) clad in samurai costume leads other local poeple as she rides her horse during a parade at the annual Soma Nomaoi festival in Minamisoma, Fukushima Prefecture, on July 28, 2012. The traditional full-scale festival kicked off for the first time after the accident of the Fukushima Dai-ichi Nuclear Power Plant following the massive earthquake and the tsunami on March 11, 2011. (Photo by Toru Yamanaka/AFP Photo)

A man carries floats as he walks on an algae covered beach as a truck collecting algae passes by, along the coastline in Qingdao, Shandong province, July 6, 2015. (Photo by Reuters/China Daily)