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Pentagon officials announced on Thursday that they had detected a Chinese “surveillance balloon” flying over Montana. On Friday the Pentagon’s press secretary said that the balloon is now over the central U.S. and moving eastward at an altitude of about 60,000 feet. Observers on the ground have been able to snap photographs and videos of the object, and the incident has prompted Secretary of State Antony Blinken to cancel a planned trip to China.
Although China’s Ministry of Foreign Affairs quickly claimed that the object is merely a civilian weather observatory blown off course, later on Friday, the Pentagon press secretary, Air Force Brigadier General Patrick Ryder, held a press briefing where he stated, “We know that it’s a surveillance balloon…. We know this is a Chinese balloon and that it has the ability to maneuver.”
This maneuverability is beyond the capabilities of most high-altitude balloons, says John Villasenor, director of the Institute for Technology, Law and Policy and a professor of electrical engineering, law, public policy and management at the University of California, Los Angeles. “The only balloons I’ve ever heard of are the ones that can go up and down or the ones that don’t do anything—they just go completely at the mercy of the winds,” he says. “But the phrasing from these spokespeople seems to suggest some greater degree of control than that. I don’t know what that means, but I think it’s notable…. It adds some more complexity to the whole thing.” In addition to its maneuverability, the surveillance balloon differs from a typical weather balloon in other ways, according to the Weather Channel. First, it has been airborne for days, but weather balloons typically remain up for only a couple of hours. The Chinese balloon is also roughly the size of three buses, whereas weather balloons typically expand to only about 20 feet across.
Scientific American spoke with Villasenor about why the aircraft’s maneuverability is so unusual and how such surveillance balloons compare with satellites.
[An edited transcript of the interview follows.]
Is it possible to steer or otherwise control a typical high-altitude balloon?
It can be controlled, but let me be careful about what I mean by that. Balloons go with the wind. And so the only control that a balloon has is: in some balloons, you can control the altitude—you can make it go higher or lower. To the extent that the wind speed and direction varies with altitude, you can change the altitude, within some limits.
