Humanity's insatiable drive to challenge limits and achieve "faster, higher, stronger" outcomes finds expression in diverse arenas, notably in the realm of ultra-high altitude balloons (UHABs).

Unlike conventional aircraft reliant on fuel power, UHABs leverage their inherent buoyancy to ascend to remarkable altitudes, facilitating exploration and research in the upper reaches of Earth's atmosphere.

The United States, at the forefront of modern high-altitude balloon technology, embarked on pioneering research in this domain. On August 25, 2002, NASA unveiled the "Big 60," an ultra-high altitude balloon with a staggering volume of 1.7 million cubic meters. This colossal balloon, bearing the weight of the cosmic ray detector LEE weighing 690kg, achieved a remarkable altitude of 49.4km. Its membrane, crafted from 10.2 micron three-layer co-extruded film material, exhibits superior strength and resilience compared to traditional zero-pressure balloon membranes, enabling it to withstand impact loads during deployment.

Meanwhile, Japan's JAXA spearheads advancements in UHAB technology. In 2002, a JAXA test balloon carrying a 10kg payload ascended to an impressive altitude of 53km, showcasing Japan's prowess in this field. Subsequently, a test flight conducted in Hokkaido on September 20, 2013, shattered records by reaching a soaring altitude of 53.7km, establishing a new world record for high-altitude balloon flight. JAXA's balloon, boasting a membrane thickness of merely 2.8 microns, a diameter of approximately 60 meters, and a volume of 80,000 cubic meters, is instrumental in conducting high-altitude meteorological observations. Prior to the advent of such technology, meteorological observations at such altitudes were primarily reliant on sounding rockets.

The development of UHABs holds profound implications. Elevating the balloon's altitude enhances detection coverage and brings operations closer to the space environment. Pushing altitudes beyond 40km or even exceeding 50km augments the balloon's capabilities and broadens its scope of applications, enabling it to meet more demanding testing mission requirements. However, ascending to greater altitudes presents formidable challenges. Lift and load, pivotal design parameters for buoyancy devices, significantly influence balloon design. Balancing these parameters becomes increasingly intricate as altitudes rise.

Achieving lift beyond 40km or 50km necessitates reducing payload and employing thinner balloon membrane materials. Material strength is a critical factor limiting lifting capacity, as increases in lift escalate balloon volume, subsequently exacerbating design, manufacturing, and deployment complexities. Thus, optimizing material strength while minimizing surface density emerges as a crucial strategy to mitigate these challenges. By enhancing material strength while simultaneously reducing surface density, the rate of weight increase in the balloon can be curbed, enabling the realization of higher lift capacities within a relatively smaller balloon volume. This approach not only enhances performance but also streamlines design, manufacturing, and deployment processes.

The exploration of ultra-high altitude balloons epitomizes humanity's relentless pursuit of innovation and discovery. These balloons, propelled by ingenuity and technological advancement, offer a gateway to the uncharted realms of Earth's upper atmosphere, opening avenues for groundbreaking research and exploration. As we continue to push the boundaries of what is possible, the evolution of UHABs stands as a testament to human curiosity and determination to reach new heights.

The evolution of ultra-high altitude balloons (UHABs) represents a testament to human ingenuity and perseverance in overcoming the challenges of exploring the Earth's upper atmosphere. Beyond their scientific applications, UHABs hold promise for various practical uses, including telecommunications, surveillance, and atmospheric research.