Apollo 4 (AS-501) was the first uncrewed test flight of the Saturn V launch vehicle — the massive rocket that would ultimately carry astronauts to the Moon. Launched on November 9, 1967, from Kennedy Space Center’s Launch Complex 39A, it was the first mission ever to lift off from Pad 39A, the same pad that would later launch Apollo 11 and numerous Space Shuttle missions.

The mission was an “all-up” test, meaning all three stages of the Saturn V were flown together for the first time rather than being tested individually — a bold decision championed by NASA administrator George Mueller. All three stages performed flawlessly. After reaching orbit, the S-IVB third stage was reignited to simulate a Trans-Lunar Injection burn, pushing the unmanned CSM-017 Block I Command Module to an apogee of approximately 11,240 miles (18,092 km). The spacecraft then plunged back toward Earth at roughly 24,900 mph, simulating the speed of a lunar return to test the Command Module heat shield under the most extreme conditions possible.

The sheer power of the Saturn V stunned observers. The launch shook buildings 3.5 miles away at the press gallery, where ceiling tiles fell and windows rattled. CBS News anchor Walter Cronkite, broadcasting live, famously exclaimed as his booth shook: “Our building’s shaking here!” The five F-1 engines of the first stage generated 7.5 million pounds of thrust at liftoff.

Apollo 4 was a complete success, validating the Saturn V design and the heat shield for lunar-return velocities. It splashed down in the North Pacific Ocean just 8 hours and 37 minutes after launch and was recovered by the USS Bennington. The mission cleared the way for subsequent Saturn V flights and, ultimately, the Apollo 11 Moon landing less than two years later.