Apparently, the Soviet Union developed combat balloons during the early years of the Cold War. I was aware of Imperial Japan's largely unsuccessful attempts to attack the USA with free-floating incendiary device-armed balloons during WW2, and assumed that no other country ever tried to repeat the failed experiment but it turns out I was wrong.
https://www.thedrive.com/the-war-zon...f-spy-balloons
The article includes photos of a helium generating trucks for filling free balloons. Such a vehicle could make for an unusual T2k encounter.
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