Why would China send a huge spy balloon to spy on the U.S.?

The balloon carried an underslung payload described as a "technology bay" estimated to be the size of "two or three school buses", and was powered by sixteen solar panels mounted on the payload.[a] The balloon itself was about 90 feet (27 m) in diameter.[34] A U.S. official quoted by CBS News said the craft had a rudder for limited steering.[24] National Security Council spokesman John Kirby said the craft had a propeller and could maneuver.[35] A Chinese Foreign Ministry spokesperson said it had "limited self-steering capability."[36] USNORTHCOM and NORAD Commander General Glen VanHerck estimated the payload weighed over 2,000 pounds (910 kg).[37]


Wouldn't it be better to use a small UAV or stealth plane or satellite? Or is there some kind of political implications using those alternatives would have had against the U.S.? I am trying to understand what kind of outcome the Chinese government was expecting from all of this, and what kind of win they got out of that or expected to get.

If it's too speculative, just tell us the difference in outcome between sending a huge spy balloon and sending a spy plane or any small unmanned vehicle.

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    According to China, this is a civilian weather balloon blown off course. If they're telling the truth, that's the answer. If their lying, it's plausible deniability, which is always a key tactic of espionage/diplomacy.
    – Brian Z
    Commented Feb 7, 2023 at 14:25
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    This question just invites speculation. It's therefore not suitable for this site.
    – Philipp
    Commented Feb 7, 2023 at 15:40
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    @whoisit - Changing the title question didn't help. The body remains the same and the title question is not about politics, it's about technology.
    – Rick Smith
    Commented Feb 9, 2023 at 3:42
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    @BobaFit "Speculation can be fun and educational." Can be but often enough isn't. The experience here is that invitations for speculations just result in lots of conspiration theories. We need facts. Ultimately we cannot know why China would or wouldn't do this. Commented Feb 9, 2023 at 6:32
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    I don't think technical spycraft details are on-topic. Commented Feb 9, 2023 at 23:28

4 Answers 4


Balloons have advantages over satellites. They are cheaper, are closer to the objective resulting in higher optical resolution, have a higher payload resulting in more instrumentation and can also receive more signals like short range communication that cannot be received by satellite. Small balloons may be difficult to spot by radar and may fly so high (>17 km high) that they are difficult to neutralize. Finally they can theoretically stay over a certain position for a longer time and they could in principle carry other military equipment than just surveillance equipment like rockets or drones for example and deploy them at a suitable time.

As long as they aren't lost, they provide a good alternative to satellites with the drawback that once they are spotted, they are clearly a very visible and blatant intrusion (which is also true for every alternative but satellites).

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    The 'once spotted' part makes them mostly pointless to use today. A balloon is easily visible with the resolution of a satellite picture, so essentially as long as there are no clouds above it, it is visible at all times. If you look at the wikipedia article the US knew about it the moment it entered its air space and was able to show its entire flight path since lift off in China.
    – quarague
    Commented Feb 7, 2023 at 15:24
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    @quarague And recent evidence suggests that they have sent a few over and this is the first one we noticed.
    – Joe W
    Commented Feb 7, 2023 at 16:01
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    @quarague: No, the smaller ones are pretty damn hard to spot; so much so that they often carry radar reflectors (to vastly increase their radar signature) when put up over own territory. thedrive.com/the-war-zone/44352/… The [real] question is whether China really thought the airliner-sized one would not be spotted like that or if they were planning for it to just skirt the US as they [likely] did next to Hawaii last year, but something went wrong (this year)... Commented Feb 7, 2023 at 16:30
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    Here's a somewhat in-depth article on US efforts to make their own popularmechanics.com/military/aviation/a38005873/… Commented Feb 7, 2023 at 18:08
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    @quarague Correct and it has also brought to light the fact that they sent over balloons in the Trump years and earlier in the Biden years. This is just the first one that has been spotted while it was over the country ang gotten attention. Evidence shows that the being spotted part wasn't an issue until now.
    – Joe W
    Commented Feb 7, 2023 at 18:38

There are a number of possibilities. And we are in a situation of reduced knowledge. We don't know the nature of what was on the balloon. It's not clear exactly where it was launched. China is a very large place. It is not even necessarily the case it was launched from inside the country. It may have been launched over the ocean, just as an example. It's not clear which group (agency, faction, etc.) launched it.

So let's list some possibilities. With the degree of uncertainty, it's not really possible to make a clear decision as to which is more likely. This is all rank speculation. It may be fun though.

It could be a research balloon as claimed. It could be scientific research, doing things like sampling air temperature, wind speed, chemical content, and so on.

It could be a "look over there" device to distract from something else. Exactly what might be worth such a distraction is difficult to be clear on, since it is not clear exactly who launched it. It's not even clear if the distraction would be meant to distract people in the west or inside China.

It could be an over zealous mid-level type operative. Say about the level of a colonel or junior general. He may have taken some suggestion from a higher-up and just "run with it."

It could be intended to collect data that is difficult to get from satellites. Information like cell phone chatter and such.

It could be a "blue sky" type effort. Hey, let's try this and see what happens. Maybe nothing. Maybe we get lucky. At worst, we learn something about where balloons will go if released from such-and-such place. This is potentially useful information to tuck away for later use.

It could be a "brush back" activity. This is a term from baseball. If the batter is getting too aggressive, you send him a high-and-inside pitch to keep him thinking. The intent of this balloon could have been to say "I can look at you for days."

There was an official visit planned by a US official. Some faction in China may have perceived this as favoring some other faction. They may have deliberately sought to screw up the political relationship just enough to get the trip canceled. They may have perceived this as being such that the favored group was no longer favored.

Finally, my own pet theory. Note that I have nothing more than my own imagination to support this, any more than any of the other possibilities. It could be a thing of taking every slack inch. I'm not sure what the word for this is, but it is definitely present in Chinese political activity. It's even present in the daily lives of Chinese persons. Here is an example I experienced directly. I was in Beijing, waiting in line to get into a dinner theatre restaurant. Since the seats were all numbered and assigned with your ticket, there was no point in trying to rush the door. So, I and my GF were calmly waiting. But it was kind of boring not being able to sit. So I stood on tip-toe to look over the crowd to try to see if the doors were open. When I then stood back down on my heals, I found that the woman who was behind me had scooched so close behind me that her toes were under my heals. She did not even seem surprised I had stood on her toes. Nor did she make any attempt to back up from under my heals. She was trying to gain the few inches in line.

This sort of thing is not rare in places such as the border between India and China. Chinese forces will do things like coming and standing on the line they are not permitted to cross. Then they will walk a few steps over, stand there and look around. Then they will do things like picking up stones and carrying them back. Or bringing lawn chairs and sitting on the forbidden side. And so on. However far they get away with, they push a little farther and a little farther. Eventually it provokes a confrontation. Since this border location outlaws weapons on both sides, it has several times resulted in fights involving shoving, punching, throwing of stones, use of clubs, etc. Such confrontations have escalated to people being killed on both sides.

The idea of the balloon may have been like that. Crowd up so close to the boundary of acceptable behavior, even cross it just a little, to see how far they could get. If they get away with a balloon over the center of the US, then maybe next they try a drone. If they don't, maybe next it's a balloon over Alaska or Hawaii.


Well, the US isn't publicly saying all that much in terms of technological specifics, but they did say that one balloon crashed next to Hawaii last year, which is how they seem to have made their determination as to the exact nature of the equipment on it:

A Chinese spy balloon that crashed off the Hawaiian islands last June also yielded helpful information, including about the nature of the technology China is using, they said.

For instance, some of the balloons are outfitted with electrooptical sensors or digital cameras that, depending on their resolution, can capture highly precise images, officials said. They also are equipped with radio signal and satellite transmission capability, they said.

China has made significant use of balloons to monitor targets on the ground, officials said. The balloons often don’t use the most cutting-edge technology — in most cases, the sensors aboard don’t capture more information than China could obtain with a satellite.

But balloons offer some advantages. They can linger over a target for hours, whereas a satellite orbiting Earth may have only minutes to snap a picture of its target. “If you have a balloon that’s moving extremely slowly you have persistence that you can’t get from a satellite,” said retired Air Force Lt. Gen. Charlie “Tuna” Moore, a former fighter pilot who helped run operations out of NORAD and retired in October as deputy of U.S. Cyber Command.

Analysts think the balloons, like drones, can be remotely piloted — at about 30 to 60 mph, said one official. And because balloons float along high-altitude winds, their paths are less predictable and thus more difficult to track. The balloons are also much cheaper to produce and launch than space-based satellites.

Some of the balloons have been launched from China on flight paths that took them around the entire globe, officials said. [...]

A U.S. official said that “there was no sense that” the balloon’s incursion into continental U.S. airspace on the eve of Blinken’s visit was a deliberate provocation. But, the person added, “We are confident that this was a purposeful global program.”

Although they don't quite say it, one can read between the lines the US may somewhat believe that the balloon shot down might have malfunctioned in some respect (as China says actually happened). Most of the other incidents that the US mentioned don't have a public record, but interestingly enough there was another reported near Hawaii in Feb last year, for which the US scrambled jets. The significant time difference suggest it's not the one that the US says crashed in June. Nonetheless, the Feb 2022 one had its path plotted by some journalists/sleuths. It seemed to stay just out of the US territorial waters. So it is somewhat plausible that most missions till now were planned more carefully in that regard.

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It's also worth mentioning perhaps that the US sees some advantages in this kind of tech for their own use as well...

Balloons’ durability and carrying strength could help them cover the bases neglected by those craft. World View Enterprises, a private company which develops near-space technology for the Pentagon and NASA, calls their balloons Stratollites. These giant pumpkin-shaped aircraft measure up to 800,000 cubic feet in volume. Their gondolas can house daylight and thermal cameras, radar, radio frequency sensors, and solar panels.

With a newly developed sensor that can measure wind patterns, and a design that can execute flight changes efficiently based on those readings, a Stratollite can change altitude, catch winds, and maintain position within 12 miles of a specified target for four days. “We think this has the potential to be a game-changer for us: a great, long-duration, long-dwell surveillance platform,” said Admiral Tidd, Commander of U.S. Southern Command over Central America, South America, and the Caribbean.

The same article notes however that the ability to plot a course and maintain position is rather critical, and that the tech that enables that is actually rather new, even if balloons have been [more or less tentatively] been used for this purpose before:

The USAF’s Project Genetrix released spy balloons disguised as weather balloons over the Soviet Union in 1956, their downward-pointing cameras intending to photograph top-secret installations. This was the only way to see inside the country before satellites, but as the unpowered balloons could only drift at random with the wind, they gathered little useful information.

And there's one other interesting point in another article on a US startup [Urban Sky], namely that the tech that enables reasonably precise positioning is actually rather difficult to miniaturize, which might explain some size aspects in such balloons seen insofar..


One idea is that it was supposed to be an act of humiliation, and not stealthy spying. The USA has caught China losing a face over Nancy Pelosi Taiwan visit, so now China makes USA experience significant emotional discomfort from the spy balloon.

Much like USSR was caused to lose its brick face in the Mathias Rust Red Square landing incident.

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    These balloons have been reported over other countries and new evidence is suggesting that this has been happening long before the trip in question. cnn.com/2023/02/05/politics/…
    – Joe W
    Commented Feb 7, 2023 at 14:29
  • Not sure "rage" is how I'd describe the feeling on the ground here. Commented Feb 7, 2023 at 15:11
  • Yeah not quite either Commented Feb 7, 2023 at 15:53
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    I haven't downvoted, but the obvious difference is that Pelosi's visit was not hidden or denied thereafter as to its nature, but China says the balloon didn't intentionally fly over the US but rather lost control (and that it was a meteo balloon). I suppose this could be a more subtle dig/equivalance as in Biden having "lost control" over Pelosi back then, but would require a bit more of an in-depth analysis to see an equivalence like that. Commented Feb 7, 2023 at 17:33
  • The whole idea of asymmetric conflict is that there are obvious differences in behavior of its sides.
    – alamar
    Commented Feb 7, 2023 at 17:35

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