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Japanese Balloon Bombs of WWII

In November, 1944, the Japanese began launching unmanned bomb-carrying balloons, which travelled on prevailing winds across the Pacific Ocean to North America. It was hoped that the balloons would start forest fires and cause general panic among the population.

The balloons measured about 33 feet in diameter and 70 feet from the top of the balloon to the payload at the bottom. They were first made of paraffined paper, and later from latex and fabricated silk, and contained hydrogen gas. The payload consisted of 36 sand-filled paper bags for use as ballast, 4 incendiary bombs and 1 33-pound anti-personnel bomb.

The balloons began their three to five day journey from Japan at an altitude of about 35,000 feet, usually travelling at speeds between 80 and 120 miles per hour. As gas slowly leaked from the balloons, they descended in altitude. When they fell to about 25,000 feet, a barometric pressure switch would cause one of the ballast sandbags to be dropped, and the balloons would rise again to 35,000 feet. This up and down pattern continued as the balloons crossed the Pacific Ocean. When the balloons reached the west coast of North America, they were supposed to have exhausted their supply of ballast sandbags and the bombs would then be used as ballast, with one bomb being dropped with each descent to 25,000 feet as they travelled across land. After the final bomb was dropped, a fuse would be ignited and the balloons would destroy themselves in bright orange fireballs.

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