In recent weeks, China and the United States have exchanged accusations of espionage, but with a slightly unusual type of spy: a balloon. A Chinese inflatable object was detected and shot down in American airspace. Subsequently, the Asian country, in addition to denying the illegal practice, said that several of these artifacts from the US have already been sighted flying over its territory.
Whether, in fact, the balloons were used for espionage is not clear, but the importance of these artifacts for science, on the other hand, is undeniable.
Cheaper and more versatile, they can be used by several areas, from meteorology to engineering, helping to collect data from the troposphere and even the stratosphere. The most common use of these instruments by science brings a result that we enjoy daily: the weather forecast. Scientists use weather balloons, made of latex and filled with helium gas, which usually have a survival time of a few hours before bursting (from 3 to 6, in general), to collect data from the troposphere (the lowest layer of the Earth’s atmosphere, which goes up to about 15 km, where meteorological phenomena occur), with a radiosonde attached to the floating object.
The probe collects data on temperature, humidity and wind. “This meteorological information obtained from the surface profile up to about 10, 12 kilometers is important for starting meteorological models, which today also rely on satellite information with high-resolution data. This is very important information for weather forecasting, for example, but also locally to determine the atmospheric conditions of stability and instability that will lead to rain”, says Professor Augusto José Pereira Filho, from the Department of Atmospheric Sciences at the University of São Paulo ( IAG-USP).
The Altitude Meteorological Station (EMA), under the responsibility of the Brazilian Air Force (FAB), located at Campo de Marte Airport, in São Paulo, for example, launches two balloons daily: at 9am and 9pm. “The purpose of the soundings is to carry out observation of the upper air, so that alerts can be issued in necessary situations, such as in cases of ice formations and strong winds at altitude”, explained the Air Force Command, in a note.
The size of the balloon used is 1.5 meters, when inflated on the surface, and it weighs about 2 kilos with radiosounding. Made of a material called neoprene, it reaches altitudes close to 30 kilometers. The equipment is inflated with hydrogen gas, instead of helium, according to the Air Force Command. What makes balloons fly is the buoyant force, which results from the difference between the displaced air mass and the total mass of the object. “The (meteorological) balloon, when it’s here on the surface, is a few cubic meters in size, but when it gets there in the stratosphere it gets so big that it ends up exploding and falling”, says Pereira Filho.
And before you despair, thinking that a radiosonde – or other scientific measuring instrument – at high speed could fall on someone’s head, inside the balloon there is a stretched parachute. When the balloon reaches its maximum size and bursts, the parachute becomes free, opens and reduces the load’s falling speed, although even without this feature, the chance of hitting a person is low.
BEYOND METEOROLOGY
Although weather balloons are the most common and are launched daily, other areas can benefit from data collected by this type of object. Engineer Marcus Cisotto, from the Small Satellites Division of the National Institute for Space Research (Inpe), says that his team uses balloons to test payloads that will later be used in nanosatellites. “It’s much cheaper to do a test using a balloon than a satellite”, he says. He says the latter can be 100 times more expensive than the former.
The American space agency (NASA) has a specific department to collect space and terrestrial data, the Balloon Program Office. They, however, use other types of balloons than the meteorological one, the zero pressure ones (open at the bottom and with open ducts hanging on the sides to allow the gas to escape and avoid the pressure inside the balloon) and the super pressure ones (completely sealed without open ducts). They are made of polyethylene, a kind of thin plastic.
While meteorological ones have the capacity to lift loads between 1 and 3 kg, these other types can lift almost 4 tons, carrying larger instruments, such as telescopes, for example. The duration before exploding varies from 3 hours to a hundred days, depending on the type of mission and size (besides, of course, the conditions it will face during the flight). Capable of crossing borders and lasting a series of days in the sky, the Chinese balloon is most likely a zero-pressure type, according to experts consulted by the Estadão. Regarding the non-communication of the loss of control of the object by the Asian scientists (something possible and linked to their limitations), they classify the event as “rare”.
LIMITATIONS
Balloons, as a scientific instrument, have some limitations. The path they follow is determined by currents in the atmosphere. Even with great knowledge of atmospheric conditions, there is a great degree of uncertainty about the path they will follow. “The mechanism (their) is to go up and down. These balloons don’t have the aerodynamics to fly, they are made to float”, says Cisotto, from Inpe. As, in general, there is interest in collecting the payload from the balloon, location systems are coupled, such as GPS. In larger balloons, there is a mechanism to destroy them via remote control, in case they do not follow the intended route.
In the case of weather balloons, according to Pereira Filho, a professor at USP, another limitation occurs when the object enters clouds. “The cloud has more moisture inside it and that can change the measurements.”
RULES
Releasing a balloon in Brazil is considered a crime. In 2017, the Brazilian Air Force reported, on its website, that the release of these objects puts aircraft at risk and can be classified as a crime as established in article 261 of the Penal Code. The practice can also be considered an environmental crime under article 42 of the Environmental Crimes Law.
In a note, the Air Force Command explained that, “with the exception of balloons used exclusively for meteorological purposes, which comply with the provisions set forth in specific legislation, no unmanned free balloon should be operated without the prior approval of the Airspace Control Department ( Decea)”.
“With regard to the application of sanctions to users who fail to comply with current legislation, the Air Force Command, through the Air Force Judgment Board (JJAER), and after due administrative process, has the competence to apply fines and suspensions” , said the command. “If the presence of free balloons not authorized by Decea causes danger to third parties, the FAB has the competence to initiate Policing Measures for the Brazilian Airspace.” Cisotto explains that, for launches made by his team, it is necessary to request authorization from the Regional Space Control Center (CRCEA) and coordination with São José dos Campos Airport, close to the launch site.
The information is from the newspaper The State of S. Paulo.
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