Kiyoho Matsushima

Three-Dimensional Gore Design Concept for High-Pressure Balloons

Anewdesign concept, named three-dimensionalgoredesign,isinvestigated forthedevelopmentof alargesuperpressure balloon capable of carrying a heavy payload. The theoretical and experimental studies are contrasted with the conventional natural shape balloon design. Each gore of the three-dimensional gore balloon has a bulge of small local radius between adjacent load tapes. This bulge is obtained not by e lm elongation but by adding excess e lm in both the circumferential and meridional directions. The longer edge of the gore is attached to the shorter load tape in a controlled shortening ratio. The e lm tension is zero in the meridian and extremely low in the circumferential direction in proportion to small local radius of a bulge. In addition, the maximum pressure of this balloon does not depend on the balloon volume. Test balloons of several sizes have been manufactured to cone rm the feasibility of the three-dimensional design concept. Indoor full ine ation tests and a e ight test of these balloons have been performed successfully.

Flight demonstration of a superpressure balloon by three-dimensional gore design

Abstract On May 15, 1999, a balloon with a volume of 3,100 cubic meters was successfully launched from Sanriku Balloon Center of Japan. It became a superpressure balloon at 19.2km in altitude with 20% pressure difference to the ambient atmosphere. This is the first superpressure balloon capable of suspending a heavy payload. It was designed by the new ‘three-dimensional gore design’ method and was based on a pumpkin shape balloon with bulges of small radii between adjacent load tapes without the help of film extensibility. The balloon climbed up to 21.6km in altitude by dropping the ballast and held out against a 64% pressure difference over the ambient atmosphere. This flight test proved the capability of large stratospheric superpressure balloons by this new design method.

Feasibility study of EVAL balloons

Abstract For a new balloon material, we have been studying the properties of an EVAL (Ethylene-Vinyl-ALcohol) film during a part of few years. The EVAL film is a product of Kurare Plastic Company, and has mechanical properties similar to that of a Mylar film. Besides this strong mechanical strength, we found that the EVAL film has several characteristics which seems to be suitable for the balloon material. Those are: 1. 1. Sandwiched EVAL films laminated by polyethylene films can be heat-sealed, 2. 2. Gas leakage through the EVAL film is extremely low, and for Helium gas, it is almost 100 times less than that of a Mylar film, 3. 3. The EVAL film is transparent in the optical band, while it efficiently absorbs the infrared radiation from the earth. In 1997, we have carried out a test flight from the Sanriku Balloon Center using a small balloon with a volume of 1000 m 3 . The balloon reached an altitude of 22 km successfully and showed a maximum burst pressure of 2.1 g/cm 2 . In this paper, basic properties of the EVAL film and performance of the test balloon are described.