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Comment by snickerbockers | Hacker News Reader

Im pretty impressed that it made it all the way across the continent in a couple days, i had no idea high altitude balloons could move that fast.

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Winds are seriously fast at higher altitudes — check out the different wind speeds using the "height" option on this site: https://earth.nullschool.net/#current/wind/surface/level/ort...

I poked at the website a bit and the fastest wind speed I could find in the world was roughly 360 km/h. Over the US there were some 250 km/h winds.

That is interesting!

Technically the ballon isn't moving itself in anyway at all, it instead is depending on the wind. As the atmospheric pressure lowers the maximum speed of the wind can increase greatly. For example the speed of the jet stream commonly exceeds 275 miles per hour. It looks like the strongest jet winds were closer to canada, had the jet been in the US it could have made it across the country in a day.

There was mention by the Chinese that is had some motive power of its own, or at least strongly implied when their PR said some the thing like “limited maneuvering capability”. That seems to indicate that it had some. It would a bit surprising if a payload the size of 2-3 school buses wasn’t outfitted with a reasonable amount of controllability, at least some control surfaces even if they inexplicably excluded even minimal and limited propulsion.

Probably ballast control to select favorable winds at different altitudes

A reserve of buoyant gas and/or some weights to drop

"Maneuvering capability" probably means that it can affect its course (probably by ascending or descending to find more favorable winds), not speed.

Not much they could do there. Highly likely just up and down: https://www.scientificamerican.com/article/chinese-spy-ballo...

Unless the Chinese have balloon control tech we’ve never even fathomed before. That would be way scarier than the balloon itself.

"Officials said the balloons are part of a fleet that China uses for surveillance, and they can be maneuvered remotely through small motors and propellers."

https://apnews.com/article/politics-united-states-government...

Imagine the earth is also spinning under the balloon?

That doesn't really matter, but the jetstream does matter. That's why it is going West-to-East to begin with.

It doesn’t matter for the same reason that the earth doesn’t go flying out from under you if you jump into the air. Yes, it’s spinning, but so is everything else, so it nets to 0

The jetstream is fast enough that it factors into any flight at altitude when it comes to fuel estimations and path calculations, up to 12% difference or so iirc.

Indeed this is really obvious to anyone who regularly travels to California and back to the somewhere on the eastern half of the US (or vice versa). The time it takes for the east bound leg is way faster than the west bound leg. Going from San Francisco to Detroit for example is about an hour faster on the east bound direction.

Yeah, atmospheric winds and the jet stream are impressive forces. There is a lot of convection going on up there.

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