The supposed Chinese spy balloon detected by the United States, which according to Pentagon sources has flown over its territory for several days, is an example of the growing use of a technology that in some cases can replace satellites, both in its civil and military applications.
Based on the hot air balloon, the invention developed by the Montgolfier brothers, and equipped with spy devices, especially a camera, spy balloons fly over a certain area in order to gather information.
Its flight height ranges between 24,000 and 37,000 meters, much higher than that of commercial aircraft, which do not exceed 12,000 meters. In addition to the possibility of including a radar, they are propelled with solar energy to control their flight.
The first use of hot air balloons in the military field dates back to the American Civil War (1861-1865), when they took advantage of the height to monitor enemy lines.
Compared to satellites, spy balloons have the advantage of operating at shorter distances than satellites and doing so for a longer time, since they can remain fixed, unlike satellites.
On the other hand, their economic cost is much lower, since they do not need the complex infrastructure of putting satellites into orbit and they are easy to recover. Also, although the balloons cannot be operated directly, they can be guided over a wide area and change their altitude.
Regarding the disadvantages, it should be noted that they do not offer the same level of "persistent surveillance", a strategy that analyzes the level of effectiveness in surveillance and defense tasks of this type of aircraft, including drones. Nor would they make a significant difference compared to the satellite networks currently in orbit around the earth.
Several municipalities around the world have considered the use of these devices to guarantee the safety of cities. In 2018, the Police of the Autonomous City of Buenos Aires reported on its social networks that it had acquired a surveillance balloon and that it had used it suspended during a Copa Libertadores final flying over the River Plate stadium.
In Colombia, the SkyStar 180 aerostatic system was deployed during the visit of Pope Francis to Colombia in 2017. The Jerusalem city council and the Israeli police also used these systems in 2014 to try to stop the wave of attacks and riots suffered by the city.
For a few years there have been some “startups” specialized in launching surveillance balloons into the stratosphere for scientific and commercial purposes, such as World View, from Arizona (USA), a pioneering company in the sector that also aims to offer 2024 a tourist experience.
World View has, specifically, some balloons called Stratollites, which are capable of taking quality photos from 15 kilometers high.
In addition to observing the earth at high altitude, its technology could be used by the United States to fight drug smuggling or human trafficking, whether on land or at sea.
But the future for this technology is uncertain. Alphabet, Google's parent company, decided in 2021 to discontinue its hot-air balloon project to bring internet to rural areas, known as Loon.