High-altitude balloon
（重定向自Stratospheric balloon）
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). In 2002, a balloon named BU60-1 attained 53.0 km (32.9 mi; 173,900 ft).