Apollo 10 launched atop a Saturn V rocket carrying Tom Stafford, John Young, and Eugene Cernan on a mission that tested every element of a lunar landing except the landing itself. The crew flew the lunar module to within 8.4 nautical miles of the moon's surface, providing critical data that cleared the way for Apollo 11's landing two months later.
NASA engineers deliberately limited the fuel in Apollo 10's lunar module ascent stage, fearing that Stafford and Cernan might be tempted to attempt an actual landing if given the chance. The mission's playful call signs—Charlie Brown for the command module, Snoopy for the lunar module—belied the intense seriousness of the rehearsal, which tested every procedure short of touchdown.
During the descent toward the lunar surface, the lunar module briefly spun wildly out of control due to a switch error, requiring Cernan and Stafford to fight for stabilization in a tense several seconds that could have ended the mission in disaster.
The mission also set a speed record for human travel, with the command module reaching roughly 24,791 miles per hour during its return to Earth—still the fastest speed ever recorded for a crewed vehicle, a record that remains unbroken as of the early 21st century.