Former Ministry of Defence motorbikes (guide price £650 to £1250) being serviced ready for potential buyers on August 12, 2011 in Colsterworth, England. Witham LTD sells a variety of former MOD equipment and vehicles to foreign countries, domestic companies and private individuals. (Photo by Matthew Lloyd/Getty Images)

The 1963 Batmobile is shown in this photo released by Heritage Auctions, HA.com December 5, 2014. The earliest known officially licensed car of comic book superhero Batman is up for auction on Saturday. The 1963 Batmobile is believed to be the first custom car to be licensed as Batman's swanky ride and could fetch up to $500,000, according to officials with Dallas-based Heritage Auctions. The opening bid is $90,000. (Photo by Reuters/Heritage Auctions)

Yang Juan, an employee at Goopal Group, takes a nap in her seat after lunch, in Beijing, China, April 21, 2016. Office workers sleeping on the job is a common sight in China, where a surplus of cheap labour can lead to downtime at work. But in China's technology sector, where business is growing faster than many start-up firms can hire new staff, workers burn the midnight oil to meet deadlines and compete with their rivals. Some companies provide sleeping areas and beds for workers to rest during late nights. (Photo by Jason Lee/Reuters)

Tao Xiangli gets out of his homemade submarine after operating it in a lake on the outskirts of Beijing September 3, 2009. Amateur inventor Tao, 34, made a fully functional submarine, which has a periscope, depth control tanks, electric motors, manometer, and two propellers, from old oil barrels and tools which he bought at a second-hand market. He took 2 years to invent and test the submarine which costs 30,000 yuan ($4,385). (Photo by Christina Hu/Reuters)

Members of the Women's Fire Brigade with their Chief Officer, March 1916. (Photo by Topical Press Agency)

Microsoft co-founder Paul Allen has spent the last six years working on a giant aircraft capable of launching rockets to space. Today, his company Stratolaunch Systems literally rolled that plane out of its hangar in the Mojave Desert for the first time ever.

An Army Sikorsky R-5 helicopter, undergoing record trials, demonstrates its lifting power by carrying 17 persons and pilot aloft as female onlookers wave in Bridgeport, Conn., January 10, 1946. During the tests records were claimed for altitude speed and both altitude and speed with payload. (Photo by Anthony Camerano/AP Photo)

Russian President Vladimir Putin, right, and North Korea's leader Kim Jong Un pose for photographers during their meeting in Vladivostok, Russia, Thursday, April 25, 2019. Putin and Kim are set to have one-on-one meeting at the Far Eastern State University on the Russky Island across a bridge from Vladivostok. The meeting will be followed by broader talks involving officials from both sides. (Photo by Alexander Zemlianichenko/AP Photo/Pool)