Development of a 2.8μm film for scientific balloons

Development of a balloon to fly at higher altitudes is one of the most attractive challenges in scientific balloon technologies. After reaching the highest record setting balloon altitude of 53.0km using the 3.4μm film in 2002, we tried to make a thinner balloon film. In 2003, we developed a forming die and an air-ring and succeeded in forming a film with a thickness of 3.0μm and a width of 220cm. Using this film, we manufactured a balloon with a volume of 5000m3 and succeeded in flying the balloon up to an altitude of 46.0km. We then searched for a good combination of resins to make a thinner and wider film and obtained films with widths of 280cm, and a thickness of 3.0μm at first, and then 2.8μm. In 2004, we performed balloon experiments making a 30,000m3 balloon with the 3.0μm film and a 5000m3 balloon with the 2.8μm film. Both balloons were well manufactured and reached the highest altitudes of 50.7 and 42.6km, respectively.