To Boost Morale, the US Planned to Nuke the MoonCarl Sagan's top-secret plan for a lunar explosion.

From the show

It really happened

Discover Project A119, the U.S. Air Force's secret Cold War plan to detonate a nuclear bomb on the Moon. This show of force, developed in response to the Soviet Sputnik launch, was intended to be visible from Earth with the naked eye. The project was ultimately canceled over fears of public backlash and contaminating the pristine lunar surface.