1945: A Japanese fire balloon[1] was responsible for causing "a short circuit in the power lines supplying electricity for the nuclear reactor cooling pumps" at

1945: A Japanese fire balloon[1] was responsible for causing "a short circuit in the power lines supplying electricity for the nuclear reactor cooling pumps" at the Hanford Site of the Manhattan Project -- but "backup safety devices restored power almost immediately". [1]: https://en.wikipedia.org/wiki/Fire_balloon https://en.wikipedia.org/wiki/Fire_balloon