Apollo 10

Firsts

First lunar mission to include a lunar landing module.

Key Dates

Launch: May 18, 1969

Lunar orbit insertion: May 21, 1969

Lunar departure: May 24, 1969

Recovery on Earth: May 26, 1969

Results

Apollo 10 was the second flight of a human crew to the Moon and the dress rehearsal for the next Apollo mission, in which astronauts would first walk on the lunar surface. Using a test version of the lunar module (LM), the crew would try many of the maneuvers that Apollo 11 would perform, short of actually landing on the Moon.

The spacecraft lifted off from Florida’s Kennedy Space Center on May 18, 1969. Just two and a half months earlier, Apollo 9 had conducted exercises in Earth orbit with a similar lunar-module stand-in. In another eight weeks and three days, Apollo 11 – the fulfillment of President Kennedy’s call to land a man on the Moon and return him safely to Earth by the end of the decade – was to be launched.

The Apollo 10 crew was the first in the U.S. space-flight program to consist entirely of experienced astronauts. Commander Thomas P. Stafford and command-module pilot John W. Young had each flown two missions in Earth orbit as part of the Gemini program; lunar-module pilot Eugene A. Cernan had flown one.

After a three-day cruise, Apollo 10 entered lunar orbit. On the mission’s fourth day, Stafford and Cernan entered the lunar module, undocked it from the command module, and began their descent. They dropped to within 47,000 feet (about 14 kilometers) of the lunar surface, tantalizingly close.

According to George Mueller, who was associate administrator of NASA’s Office of Manned Space Flight at the time, “There had been some speculation about whether or not the crew might have landed, having gotten so close. They might have wanted to, but it was impossible for that lunar module to land. It was an early design that was too heavy for a lunar landing, or, to be more precise, too heavy to be able to complete the ascent back to the command module. It was a test module, for the dress rehearsal only, and that was the way it was used.”

They spent more than six and a half hours flight-testing the LM’s communications, propulsion, attitude-control and radar systems. They took numerous photos of the lunar terrain, especially the planned landing sites. And when these exercises were finished, they jettisoned the LM’s descent stage and returned to orbit to dock once again with the command module.

While Stafford and Cernan guided the lunar module into position, Young monitored the procedure with sextant and radio ranging, ready to use the command module to control the docking if the lunar module failed. When re-docking was completed, Stafford and Cernan moved back into the command module and the astronauts jettisoned the LM into its own orbit around the Sun.

On the final day at the Moon, after further surveying and navigation-related tasks, the crew fired the rockets that would propel them out of lunar orbit and send them home. They splashed down in the Pacific Ocean on May 16, 1969, some 400 miles (640 kilometers) east of American Samoa and 3.4 miles (5.5 kilometers) from the recovery ship USS Princeton.

The Apollo 10 Command Module "Charlie Brown" is on display at the Science Museum, London, England.

- Credit: NASA