In this article, we cover Apollo 10, the launch just before Apollo 11.
The purpose of the mission was to confirm all aspects of the lunar landing mission exactly as it would be performed, except for the actual landing. Additional objectives included verification of lunar module systems in the lunar environment, evaluation of mission-support performance for the combined spacecraft at a lunar distance, and further refinement of the lunar gravitational potential.
All components of the Apollo 10 spacecraft were very similar to those of Apollo 9. The major difference in this mission was the inclusion of a fully configured lunar module. Support structures and mass simulators were added for the Modular Equipment Storage Assembly (MESA). The Apollo Lunar Surface Experiments Package (ALSEP) support structure was redesigned and the location of the power system batteries was changed in the descent stage.
Apollo 10 was a “dress rehearsal” for the landing missions that would follow and as such, it was a fully configured spacecraft. Unlike the previous orbiter mission, Apollo 8, which carried a nonfunctioning lunar module test article, this mission included a functional lunar module. This was necessary in order to test descent and return operations, which were the main objectives of the mission. It should be noted, however, that the lunar module was an early design that could not be used for a landing as it was too heavy to return to orbit from the lunar surface.
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.
The Apollo 10 mission took eight days and included a simulated landing on the Moon. All systems in the command and service modules and the lunar module were managed very well. While some problems were encountered, most were minor and none constrained the completion of mission objectives. Communication was generally adequate and the quality of television transmissions extremely good. Crew performance was excellent throughout the mission and timelines were followed very closely.
In the next article, we will cover the details about Apollo 11 Mission.