Launching of a 500,000 cubic meter balloon with the semi-dynamic launching method

Launching a large balloon in a limited launching field is a long standing problem in Japan. The largest balloon ever launched successfully was 200,000 m³ in volume. It was launched in 1973. A larger balloon with a volume of 500,000 m³ was tried later, but it burst during the ascending phase. For launching balloons with a large lift exceeding 500 kg, the conventional static launching method had the most serious problem with possible damage to the polyethylene film of the balloon caused by the holding mechanism. After that, we had developed a new static launching method to launch balloons with a total lift of 1.0 ton. For launching a large balloon with a total lift above 1.5 ton, the new static launching method had a weak point in that if there was an air bubble in the folded part of the balloon, it may puncture the balloon as it is pushed by a spool. To avoid this problem, we developed a semi-dynamic launching method in 1999 using a launcher fixed to the ground leaving a freedom of rotation around the vertical axis. We have launched some balloons using the method and have gradually enriched our experience in using this system.In 2003, we successfully launched a balloon with a volume of 500,000 m³ by using the method. This balloon was made of polyethylene films with a thickness of 20 μm and it is the largest balloon ever launched in Japan.