But government officials have offered scant details about what they’re shooting down, leaving many confused about what’s in the sky.
“We need to know a lot more about what is flying over our heads,” said Arthur Holland Michel, a senior fellow at the Carnegie Council for Ethics in International Affairs. “Stuff that flies in the sky … scares us in a primal way.”
There are a number of very common uses for balloons, some creepy and some banal. Here’s a guide to the most interesting.
Balloons have a history in espionage. As early as the third century, Chinese strategists sent lanterns in the air to warn towns of a looming attack. During the Civil War, the Union Army’s balloon corps employed civilian scientists to fly in gas-filled balloons to gain intelligence on the Confederate Army.
China’s spy balloon, part of a vast surveillance operation, is more modern. Balloon experts say it was likely akin to stratospheric balloons, which are frequently used for civilian scientific research.
These helium-filled balloons can fly up to roughly 100,000 feet into the sky, using solar-panel powered sensors to surveil — which government officials confirmed were onboard China’s balloon.
“This is not your great-great-great-great-granddaddy’s balloon,” said Andrew Hammond, a curator and historian at the International Spy Museum.
Every day, hundreds of small balloons help with weather forecasting, said Jesse Geffen, a manager at Kaymont Consolidated, which provides weather balloons to the U.S. government.
Measuring about six feet in diameter, at a cost of roughly $40, these balloons are usually filled with helium or hydrogen, and rise at about 1,000 feet per minute. A tiny sensor measures temperature, humidity, wind speed and direction, shooting the readings to the National Weather Service stations in real-time, Geffen said.
As the balloon ascends, pressure inside it steadily grows. Once it reaches around 90,000 feet, the balloon reaches its limit and bursts into thousands of little biodegradable plastic pieces, Geffen added. This self-destruction minimizes their environmental impact.
Military and research
The U.S. military and scientists use high-altitude balloons for myriad reasons, according to Russ Van Der Werff, vice president of stratospheric programs at Aerostar, which provides balloons to NASA and the military.
Its largest balloon — roughly 800 feet across and 60 million cubic feet in volume — is deployed by NASA to haul heavy space telescopes over 100,000 feet into the sky and monitor how the equipment reacts in near-space-like conditions, he said.
The military uses Aerostar’s smaller balloons to create mobile communication networks in dead-zones, while disaster-relief agencies can power cellphone connectivity in places ravaged by hurricanes.
Van Der Werff said his clients have to register flight plans with the Federal Aviation Administration, similar to pilots. “We certainly haven’t lost any balloons lately, or had any shot down lately,” he said.
Several companies are trying to use balloons for tourism and send humans roughly 100,000 feet — high enough to view the planet’s curvature.
World View, an Arizona-based company, makes balloons to haul sensors and equipment high into the sky, with their largest craft swelling up to 18 million cubic feet, large enough to fit a football stadium inside it, according to Ryan Hartman, the company’s chief executive.
The company is eyeing space tourism next. World View has sold 1,250 tickets for people who want to travel 100,000 feet into the air for roughly six to eight hours, Hartman said. Each ticket costs $50,000 and can be secured with a $500 deposit. The flight would take eight passengers and two crew members, but Hartman was unable to estimate when the first flight will be.
Zero2Infinity, a Barcelona-based balloon tech company, is also exploring tourism, according to José Mariano López Urdiales, its chief executive. Its balloon, which gets to 130 feet in diameter, would hoist a doughnut shaped chamber roughly 110,000 feet into the sky that would ultimately hold four passengers and two pilots.
Space agencies and military units aren’t the only one flying balloons into the sky — amateurs can, too.
Hobbyists across the world launch tiny balloons, many roughly six feet in diameter and filled with helium, into the sky. These balloons are often outfitted with tiny GPS trackers and cameras, and often have a longer range than personal drones.
Some hobbyists use radio transmitters to track these balloons, which can go 40 to 50,000 feet in the sky, though at least one has been documented to reach 110,000 feet.
An earlier version of this article misstated the number of passengers Zero2Infinity's recreational balloon will hold. It is four.