High-altitude balloons or stratostats are crewed or uncrewed balloons, usually filled with helium or hydrogen, that are released into the stratosphere, generally attaining between above sea level. In 2002, a balloon named BU60-1 reached a record altitude of . The most common type of high-altitude balloons is 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", defined as the area of Earth's atmosphere between the Armstrong limit ( above sea level), where pressure falls to the point that a human being cannot survive without a pressurised suit, and the Kármán line ( above sea level), where astrodynamics must take over from aerodynamics in order to maintain flight. Due to the low cost of GPS and communications equipment, high-altitude ballooning is a popular hobby, with organizations such as UKHAS assisting the development of payloads. History The first hydrogen balloon 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 of iron and 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 it descended 45 minutes later away from Paris. Crewed high-altitude balloons Crewed high-altitude balloons have been used since the 1930s for research and in seeking flight altitude records. Notable crewed high altitude balloon flights include three records set for highest skydive, the first set by Joseph Kittinger in 1960 at 31,300m for Project Excelsior, followed by Felix Baumgartner in 2012 at 38,969m for Red Bull Stratos and most recently Alan Eustace in 2014 at 41,419m. Uses Uncrewed high-altitude balloons are used as research balloons, for educational purposes, and by hobbyists. Common uses include meteorology, atmospheric and climate research, collection of imagery from near space, amateur radio applications, and submillimetre astronomy. High-altitude balloons have been considered for use in telecommunications and space tourism. Private companies such as Zero 2 Infinity, Space