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High-altitude balloons are unmanned balloons, usually filled with helium or hydrogen, that are released into the stratosphere, generally attaining between 60,000 to 120,000 feet (11 to 23 mi; 18 to 37 km). During 2002, a balloon named BU60-1 attained 53.0 km (32.9 mi; 173,900 ft).
The most common type of high altitude balloons are weather balloons. Other purposes include use as a platform for experiments in the upper atmosphere. Modern balloons generally contain electronic equipment such as radio transmitters, cameras, or satellite navigation systems, such as GPS receivers.
These balloons are launched into what is termed "near space"—- the area of Earth's atmosphere where there is very little air, but where the remaining amount generates too much drag for satellites to remain in orbit.
In France during 1783, the first public experiment with hydrogen-filled balloons involved Jacques Charles, a French professor of Physics and the Robert brothers, renowned constructors of physics instruments. Charles provided large quantities of hydrogen, which had only been produced in small quantities previously, by mixing 540 kg (1,190 lb) of iron and 270 kg (600 lb) of sulfuric acid. The balloon called Charlière took 5 days to fill and was launched from Champ de Mars in Paris where 300,000 people gathered to watch the spectacle. The balloon was launched and rose through the clouds. The expansion of the gas caused the balloon to tear and descended 45 minutes later 20 km (12 mi) away from Paris.
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