Japanese researchers developed a 3.4 µm polyethylene film.
Using a highly active Ziegler catalyst in the inflation manufacturing method, it was impossible to fabricate a film of less than 5.6 µm thickness. When research on metallocene catalyst started in 1995, we noted the catalyst and started development of ultra-thin polyethylene film in 1997. The new polyethylene film has the following features compared to the conventional film. The comonomer organization in the metallocene catalyst is even, so the presence of low-molecular weight, high comonomers is extremely low allowing high performance in anti-blocking. Also, since the presence of high-molecular weight, low comonomers is low, the new film is excellent in low temperature sealing and transparency.
Even comonomer distribution and narrow molecular weight range provide excellent performance in shock strength and various mechanical properties. Taking advantage of these properties, in late 1998 we finally succeeded in developing the world’s first polyethylene film of 3.4 micron thickness and 80cm folded diameter. The mechanical characteristics of the newly developed film are: 400kg/cm2 breaking strength and 500% retractability at room temperature; 650kg/cm2 breaking strength and 200% retractability at -80 deg C. These are sufficient for use in the balloon flight environment.
In September 1999, the Japanese succeeded in floating a balloon of 1,000m3 volume made of the ultra-thin film at an altitude of 37km. This was the memorable experiment to celebrate the birth of ultra-thin film, high-altitude balloon. In late 2001, they decided to develop ultra-thin film, high-altitude balloon No.1 (BU60-1) of 60,000m3 volume, challenging the world’s highest altitude record, and to conduct an experiment to evaluate flying performance in FY2002.
Japan was studying the resin, a balloon material, and improvement of film manufacturing method under the slogan “60km altitude.”
JP Aerospace's John Powell wants to build a balloon-launched system that can rise more than twice as high to 100km (60 miles), which is all the way to the space frontier.
This month JP Aerospace launched the latest version of its uncrewed airship prototype, Ascender 36, from its test site in northern Nevada. In a blog posting, Powell said the Ascender 36’s tests.
The first flight of Ascender 36 was a real shake down. It took two hours more than planned to get her into the air. Instead of the forecasted calm morning, they had windy condition with the wind howling from the opposite direction. However when they got her into the air she put her nose up and screamed in to the sky. Our minimum goal was to fly to 7,000 feet. If all went well we would push bit by bit to 10,000 feet. Their goal climb rate was 400 feet per minute. In the end they climbed an average 582 feet per minute and flew all the way to 13,512 feet. They landed her 11 miles down range.
There are more photos from the JP Aerospace facebook page.
Inner helium cells of the Ascender
SOURCES - JAXA (ISAS), JP Aerospace blog and facebook pages