In a World Awash in Satellites, Why Use Spy Balloons?

Suddenly, balloons are everywhere. Ever since the United States spent a week finding, following, and finally shooting down a Chinese surveillance balloon earlier this month, sightings and shootings of similar objects have dotted the military and geopolitical landscape (including, perhaps, some innocent hobbyist balloons). U.S. and Canadian authorities downed three more aerial objects over the weekend over their respective airspaces.

U.S. President Joe Biden said Thursday that those objects were “most likely balloons tied to private companies, recreation, or research institutions” and not tied to China’s spy program but added that “if any object presents a threat to the safety and security of the American people, I will take it down.”

In an era of automated drones and laser-guided missiles, let alone spy satellites, balloons may seem a rudimentary tool of espionage and warfare. But experts note that balloons have a long and lofty history and boast reasons for their continued use even with the advent of far more advanced aerial spying capabilities.

“Historically, balloons are kind of a low entry point technology,” said Thomas Paone, a museum specialist at the National Air and Space Museum in Washington, D.C., who curates the “lighter-than-air” collection. “They’re easy to make, easy to fill up with a lifting gas—whether helium or hydrogen—and they’re easy to launch.”

The use of balloons in warfare and espionage dates back to the French Revolution, with the earliest recorded use in 1794 by the French Aerostatic Corps. They made their U.S. military debut during the Civil War, and a technological leap during World War I saw phone lines attached to the balloons to relay information down in real time. Balloons also played a role in World War II, with the United States using steerable blimps to observe enemy movements and Japan briefly (and mostly unsuccessfully) deploying thousands of balloons to float bombs into U.S. territory. The first U.S. efforts to use balloons for espionage came during the Cold War, through two successive programs known as Project Moby Dick and Project Genetrix, which involved deploying hundreds of balloons with attached cameras over the Soviet Union.

“It really did not prove to be super effective,” Paone said, adding that only a handful of the 500-plus balloons were recovered and many were discovered, causing diplomatic incidents. “The project was scrapped pretty quickly.”

The advent of stealth aircraft such as Lockheed’s U-2 and SR-71, as well as the development of satellites, meant that balloons as an espionage tool by Washington took a relative back seat (though the U.S. military did deploy a version tethered to the ground during the Iraq War in the early 2000s, and the Defense Department has tested stratospheric balloons multiple times in recent years).

But as the past few weeks demonstrate, balloons continue to be very much in use by countries around the world. Ukraine said this week that it took out Russian reconnaissance balloons spotted over Kyiv.

“This is something that the Chinese seem to use a lot,” said William Kim, a consultant at the Marathon Initiative think tank who researches spy balloons. “The U.S. tends to use satellites a lot more.”

Initial assessments from U.S. officials indicate that the Chinese spy balloon shot down in early February was set up to collect electronic communications, known as signals intelligence. Officials said this week that debris recovered off the coast of South Carolina included electronic sensors. Balloons of that nature are typically made out of polyethylene, varying in thickness depending on the degree of internal air pressure, and powered by a large solar panel with an antenna array and additional systems needed to steer the balloon itself.

The Chinese balloon’s sheer size makes it a bit of an outlier when it comes to spy balloons; Pentagon official Melissa Dalton described it as 200 feet tall with a payload the size of a jetliner.

“This is a massive, massive balloon,” Kim said, adding that its altitude of 60,000 feet was at the lower end of the typical range. “This is what’s a little surprising to me, that they would send something like this over the U.S.—it’s so much easier to spot.”

The balloon’s reported use of a rudder to navigate also “doesn’t sound like the most advanced technology” and likely limited its maneuverability, Kim said, with advances in artificial intelligence making balloons more capable of detecting and following wind patterns.

The recent diplomatic fiasco notwithstanding, Kim said there are several advantages to spy balloons that heighten their appeal over more high-tech surveillance methods. The first and most obvious advantage is cost—making a balloon and filling it with helium is simply much cheaper than launching a rocket to place a satellite in orbit. A balloon’s relative proximity to potential targets and slower speed mean it can also more effectively capture data about a more targeted area.

“All things being equal, you’ll get a better performance out of the sensor if you’re at 10 or 20 kilometers [altitude] versus 300 or 250 kilometers,” Kim said. “They’re probably going at 50 miles per hour versus satellites that are moving at something like 15,000 miles per hour, where you’re kind of whipping over the Earth in orbit.”

Paradoxically, the more predictable movements of satellites make them easier to defend against, and balloons have traditionally been effective at evading radar. U.S. officials developed a method to track Chinese spy balloons only in the past year, CNN reported, and the three subsequent shootdowns last weekend were likely a result of the United States adjusting its detection parameters to slower-moving aerial objects after the first balloon.

“We don’t have any evidence that there has been a sudden increase in the number of objects in the sky,” Biden said Thursday, adding that Washington was working to define a framework for better detecting illicit flying objects without getting more benign ones caught in the crossfire. “We’re now just seeing more of them, partially because [of] the steps we’ve taken to … narrow our radars.”

More easily evading radar has been a big part of the appeal.

“We know when the Chinese satellites are overhead,” Kim said. “It really all depends again on the payload, but the balloon itself isn’t going to [trigger] radar. It’s not going to produce a ton of heat if it doesn’t have an engine or anything. So these things can comparatively be a little hard to detect, although not impossible of course.”