Can’t 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 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 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:
- How to reduce the balloon's weight,
- How to fabricate a large-volume balloon under high quality control to withstand the flying environment,
- How to hold the balloon without damage,
- How to float the thin-film, large-volume, high-altitude balloon safely and surely,
- How to realize weight saving, downsizing and reduction in power consumption 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 -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 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 balloon’s head by hand. The development of a new mechanism was required, one that could hold the balloon’s 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 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 balloon’s total weight.
Working on above five items, we started developing a thin-film, high-altitude balloon that could float above 50km altitude.