Project A119 was a once-classified U.S. Air Force plan to detonate a nuclear device on the Moon as a Cold War demonstration after Sputnik (1957). A young Carl Sagan evaluated whether such an explosion could yield scientific data and modeled potential radioactive fallout. Scientists warned the blast would damage the Moon’s pristine surface; the plan was ultimately shelved. Sagan later became an outspoken critic of nuclear weapons and their existential risks.
Carl Sagan and Project A119: The Secret U.S. Plan to Blow Up the Moon
Project A119 was a once-classified U.S. Air Force plan to detonate a nuclear device on the Moon as a Cold War demonstration after Sputnik (1957). A young Carl Sagan evaluated whether such an explosion could yield scientific data and modeled potential radioactive fallout. Scientists warned the blast would damage the Moon’s pristine surface; the plan was ultimately shelved. Sagan later became an outspoken critic of nuclear weapons and their existential risks.
12:23 AM, 11/11/2025Science
Carl Sagan and the Cold War plan to detonate a bomb on the Moon
During the height of the Cold War, the United States and the Soviet Union entertained extreme ideas as they vied for technological and symbolic supremacy. One of the most startling—and once-classified—U.S. proposals was Project A119, a plan to detonate a nuclear device on the Moon as a dramatic demonstration of power.
After the Soviet Union launched Sputnik in 1957, U.S. officials sought an even more visible show of capability. A 1959 report, declassified in 2000, argued that “specific positive effects would accrue to the nation first performing such a feat.” The U.S. Air Force commissioned scientists at the Armour Research Foundation (ARF) in Chicago to study the idea; among those consulted was a young Ph.D. student, Carl Sagan.
Project A119 was primarily conceived as a public-relations gambit. Project physicist Leonard Reiffel later explained that the Air Force wanted an explosion large enough to create a visible cloud from Earth — a lunar mushroom cloud meant to signal U.S. superiority after Sputnik.
"The main aim of the proposed detonation was a PR exercise and a show of one-upmanship," Reiffel said. He also warned planners about "a huge cost to science" from harming the Moon's pristine environment.
Reiffel and others cautioned that a blast could scar lunar features, possibly altering the familiar patterns people on Earth recognize as the "man in the moon." Technically the scheme appeared feasible at the time, using an intercontinental ballistic missile (ICBM) to deliver a warhead on the order of the Hiroshima bomb—or larger.
Sagan’s assigned task was to evaluate whether detonating nuclear devices on the lunar surface could produce any scientifically valuable data, and to model how radioactive debris might behave on the airless Moon. Biographer Keay Davidson later reported that Sagan referenced this work in a 1959 graduate fellowship application to the University of California, Berkeley—an early disclosure that helped bring the project to light decades later.
The Air Force ultimately shelved Project A119. Officials never publicly confirmed a single reason, but explanations offered afterward include concerns about unintended harm to people on Earth, fears of contaminating the Moon, and political or diplomatic risks of staging a nuclear demonstration beyond Earth.
In later years, Sagan became a prominent voice warning of nuclear dangers. In a 1987 speech he said nuclear war could "destroy the global civilization and conceivably ... could end the few million year old experiment, human experiment, on the planet Earth." His involvement in Project A119 remains an unsettling episode in the history of space exploration—one that underscores how Cold War rivalry sometimes pushed scientific judgment aside for spectacle.
Why it matters: Project A119 is an important historical example of how science, politics, and military ambition can collide. Sagan’s early, inadvertent disclosure of his role preserved the story and helped prompt broader public reflection about the ethical limits of technological demonstrations.