ResearchonBalloontoFloatover50kmAltitude

1、"Research on Balloon to Float over 50km Altitude"Cant we conduct scientific observations using lightweight instruments of about 10kg at altitudes over 50km? This question was raised in 1991. Since we had not yet reached 50km altitude, we were discussing what research and development would

2、be necessary in terms of balloon engineering. To achieve this altitude, we would naturally have to review and redesign the entire balloon system. Thus we determined to proceed with the study and development of all elements in the balloon system, not only the balloon itself, but also its fabrication

3、method, the support mechanism of the balloon head, floating method, and weight reduction of basic onboard instruments using innovative thinking and adopting the advantages of established technology.To float the balloon over 50km altitude, we had to find:1. How to reduce the balloon's weight,2. H

4、ow to fabricate a large-volume balloon under high quality control to withstand the flying environment,3. How to hold the balloon without damage,4. How to float the thin-film, large-volume, high-altitude balloon safely and surely,5. How to realize weight saving, downsizing and reduction in power cons

5、umption of the basic onboard instruments, such as transceiver, telemeter, command, and ballast valve within the weight limitation for payloads.Point 1 depends on whether it is possible to develop a new polyethylene film that is as thin as possible yet stays flexible even in a flying environment of -

6、80 deg C. As for point 2, if we adopt the conventional method using a thermal adhesion machine (electromagnet pressure bonding type of about 2m in length), we cannot fabricate the balloon with sufficient quality control. To solve the problem, we had to develop a new adhesion machine that would

7、allow us to make continual thermal adhesion operations stably under high quality control regardless of the operation space. As for point 3, the total buoyancy of a large-volume balloon is more than 50kg, so it is difficult to hold the balloons head by hand. The development of a new mechanism wa

8、s required, one that could hold the balloons head without damaging it but with the same grip as the palm of the hand. Point 4 depends on whether we can devise a new, Japanese original floating technique, including possibility of the extension of the narrow floating field at the Sanriku Balloon

9、Center (SBC).For point 5, we tried to reduce the weight of the total onboard instruments, including the battery, to about 10kg, equivalent to 10% of the balloons total weight. Working on above five items, we started developing a thin-film, high-altitude balloon that could float above 50km altit

10、ude.Development of thin-film balloon holding equipment As the volume of the balloon increases, total buoyancy increases proportionally. As a result, it is impossible to hold the balloons head in the hands. It was imperative to develop new equipment similar to the palms of the hand to hold the b

11、alloons head, and we developed new equipment using an airbag. As shown in Figure 2, the equipment consists of an airbag to hold the balloon, a cylindrical plate to fix the airbag, an electromagnet to release the cylindrical plate, etc. The balloon is gripped by filling the airbag with air, and raisi

12、ng the pressure to a level comparable to total buoyancy. The equipment can grip the balloon, even one constructed of 3.4 µm thickness film, and yet protects the thin film from damage.Figure 2 Balloon Holding EquipmentDevelopment of a large floating platformThe newly developed large floating pla

13、tform is fixed on a 6m-diameter turntable, and by turning the table we can release the balloon corresponding to the direction of the ground wind. The 4m x 3m board for placing observation instruments can lift the instruments up to 5m by elevator so that we can float the balloon in wind velocity up t

14、o 5m/s. Completion of the large floating platform shown in Figure 3 allows us to release the balloon at full inflation. This method is almost the same as dynamic floating. The launcher to release the observation instruments, however, is fixed. Thus, we completed the Japanese original floating method

15、 suitable for a narrow floating field. We call this method the “semi-dynamic floating method.”Weight reduction of basic onboard instrumentsWe succeeded in reducing the weight of the basic onboard instruments to less than 10kg by the development of: a PCM encoder circuit using serial output type ADC

16、for the telemeter; a PCM encoder and decoder using multiple code coincidence method for the command; a permanent magnet with solenoid movement mechanism for the ballast valve; etc.Figure 3 Large Floating PlatformDevelopment of 3.4 µm polyethylene filmUsing a highly active Ziegler catalyst in th

17、e 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 featur

18、es compared to the conventional film.1. 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

19、new film is excellent in low temperature sealing and transparency.2. Since the range of molecular weight is narrow, very even fabrication is possible.3. Even comonomer distribution and narrow molecular weight range provide excellent performance in shock strength and various mechanical properties.Tak

20、ing advantage of these properties, in late 1998 we finally succeeded in developing the worlds first polyethylene film of 3.4É m thickness and 80cm folded diameter. The mechanical characteristics of the newly developed film are: 400kg/cm2 breaking strength and 500% retractability at room te

21、mperature; 650kg/cm2 breaking strength and 200% retractability at -80 deg C. These are sufficient for use in the balloon flight environment.In September 1999, we 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

22、 celebrate the birth of ultra-thin film, high-altitude balloon. Figure 4 shows the history of the growth in balloon size for thin-film and ultra-thin film balloons. By late autumn 2001, we were able to obtain good results as expected for all the research and development items that the balloon e

23、ngineering team had discussed before. Next, we decided to develop ultra-thin film, high-altitude balloon No.1 (BU60-1) of 60,000m3 volume, challenging the worlds highest altitude record, and to conduct an experiment to evaluate flying performance in FY2002.Figure 4 Development History of Large Ballo

24、onBU60-1 flying experimentThe BU60-1 balloon was 34.37kg in empty weight, 74.5m in length, and 53.7m in diameter. The total weight including 0.8kg of parachute package and 4.6kg of observation instruments was 39.77kg. We mounted two ITV cameras to record images of the balloons inflation and a Sony G

25、PS receiver to measure altitude.At 6:35 a.m. on May 23, 2002, the BU60-1 was floated from SBC carrying the dreams of the balloon experiment team and affiliated researchers. It was floated by the semi-dynamic method using the newly developed balloon holding equipment and large floating platform. The

26、balloon ascended normally at a speed of 260m/min and reached the highest altitude of 53.0km at 10:07 a.m. Figure 5 shows the altitude curve measured by the GPS and Figure 6 shows the image of the balloons full inflation.Figure 5 Altitude Curve of BU60-1Figure 6 Image of Full InflationWith the slogan

27、 of “60km altitude” The BU60-1, the worlds first ever 60,000m3 volume balloon fabricated of 3.4É m thickness film, successfully reached 53.0km altitude. This altitude superseded the previous world record altitude of 51.8km achieved by the ultra large, 1,350,000m3 balloon floated by th

28、e U.S. in 1972. We believe our success is the fruitful outcome of the development of a new film, adhesion machine, balloon holding equipment, large floating platform, semi-dynamic floating method, and research into weight saving on basic onboard instruments.The balloon engineering team is now studyi

29、ng the resin, a balloon material, and improvement of film manufacturing method under the slogan “60km altitude.” We are sure that this dream will be realized some time in the near future.Development of an adhesion machine for the balloonIn FY1991, we began the study and development of the thermal-adhesion machine. The fabrication of big balloons in Japan up to that time had been done by thermal-adhesion machine, an electromagnetic pressure bonding type of about 2m in length. The machine performs adhesive operation in meter units and is easy to handle, so it is suitable for oper