Apollo 5 (AS-204) was the first uncrewed flight of the Apollo Lunar Module — the spacecraft that would ultimately carry astronauts to the surface of the Moon. Launched on January 22, 1968, atop a Saturn IB rocket from Cape Kennedy Launch Complex 37B, the mission aimed to verify that the LM’s descent and ascent engines worked in the vacuum of space and that the two stages could separate successfully.

The mission did not go entirely as planned. The first descent engine burn was intended to last 38 seconds, but the onboard guidance computer shut it down after just 4 seconds because the engine did not build thrust as quickly as the computer expected. Mission controllers at Houston quickly devised an alternate mission plan, taking manual control to fire the descent engine twice more and then the ascent engine, proving all propulsion systems worked. The critical “fire in the hole” test — igniting the ascent engine while still attached to the descent stage, simulating an abort from the lunar surface — was a complete success.

Despite the guidance computer issue, NASA declared Apollo 5 a total success. Every primary objective was met: the descent engine, ascent engine, and stage separation all performed as needed. The success was so thorough that NASA canceled the planned second uncrewed LM test flight (Apollo 6 would test the Saturn V instead), accelerating the path toward crewed LM flights. The LM-1 descent stage re-entered Earth’s atmosphere and burned up on February 12, 1968, while the ascent stage decayed from orbit on January 24, 1968.

Apollo 5 was a pivotal step in the Apollo program. By proving the Lunar Module’s engines and staging worked in space, it cleared the way for Apollo 9’s crewed LM test in Earth orbit and ultimately for the historic lunar landing of Apollo 11 just eighteen months later.