High-altitude balloon
High-altitude balloons (HABs) or stratostats are usually uncrewed balloons typically filled with helium or hydrogen and released into the stratosphere, generally attaining between 18 and 37 km (11 and 23 mi; 59,000 and 121,000 ft) above sea level. In 2013, a balloon named BS 13-08 reached a record altitude of 53.7 km (33.4 mi; 176,000 ft).