We have been developing plastic balloons made of thin polyethylene films since 1991. Since this balloon is lighter than a normal balloon, it can easily reach an altitude more than 40km with a payload less than 10kgs. In the developement of high-altitude balloons, there are following problems. First, the weight of the balloon must be minimized as much as possible. Second, the large volume balloon with thin polyethylene films must be manufactured carefully. Third, the balloon must be stably launch without being damaged. A ceiling altitude of 48.7km was achieved by the balloon with a volume of 30,000m^3 in 1995. A thin polyethylene balloon with a volume of 120,000m^3 was launched by the new launching method successfully on January 27,1997. The balloon ascended normally with ascending velocity of 275m/minute. and reached the altitude of 50.2km after three hours. These balloons can be used for high altitude observations with low cost, and can be replaced some observations of a small sounding rocket. We describe the launching method and some results of the test flight of the new balloon with the volume of 120,000m^3 in this paper.
大型の薄型高高度気球 (BT 120-1)
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