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Today in History: U.S. conducts largest high-altitude nuclear test

7/9/2025

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Summary

Story summary

On July 9, 1962, the United States conducted the Starfish Prime test, the largest high-altitude nuclear explosion in outer space. Launched from Johnston Atoll, this test was part of a series of five nuclear tests performed by the U.S. in space, marking a significant moment in Cold War-era nuclear experimentation.

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Story summary

On July 9, 1962, the United States conducted the Starfish Prime test, the largest high-altitude nuclear explosion in outer space. Launched from Johnston Atoll, this test was part of a series of five nuclear tests performed by the U.S. in space, marking a significant moment in Cold War-era nuclear experimentation.