Apollo 10

Dress rehearsal for the Moon landing

Apollo 10 was the dress rehearsal for humanity's first Moon landing. It successfully demonstrated all major objectives of the upcoming Apollo 11 mission except the landing and moonwalk itself. Expanding on tests conducted in Earth orbit for Apollo 9, astronauts brought a fully functional lunar module to the Moon and flew it within 16 kilometers of the surface, photographing candidate landing sites in Mare Tranquillitatis.

Apollo 10 liftoff
Apollo 10 liftoff Apollo 10 lifts off from Kennedy Space Center pad 39B on 18 May 1969 at 12:49 p.m. local time. NASA

The mission began on 18 May 1969 with the first and only Saturn V launch from Kennedy Space Center's pad 39B, as preparations were already underway at pad 39A to launch Apollo 11 in 2 months. Astronauts Thomas Stafford, John Young and Gene Cernan arrived safely in Earth orbit, re-lit their Saturn V upper stage booster, and blasted away from Earth towards the Moon. They arrived in orbit on 21 May.

Apollo 10 crew
Apollo 10 crew The crew of Apollo 10. From left: Gene Cernan, Thomas Stafford, John Young. NASA

A day later, Stafford and Cernan boarded the lunar module and undocked, leaving Young alone in the command module. The lunar module descent stage engine fired for 27 seconds, dropping Stafford and Cernan into an orbit of 15.6 by 113.5 kilometers above the Moon. Approaching the surface, they tested their spacecraft's landing radar, which would be critical for the Apollo 11 landing. They jettisoned the descent module, fired the ascent module engine, and rejoined Young and the command module in a higher orbit, simulating a return from the lunar surface.

Apollo 10 lunar orbit operations
Apollo 10 lunar orbit operations These diagrams from the original Apollo 10 press kit show how Thomas Stafford and Gene Cernan flew the lunar module to within 16 kilometers of the surface before rejoining John Young in the command module. NASA

Historians and space enthusiasts have since debated whether Stafford and Cernan could have bucked NASA protocol and flown the final 15.6 kilometers to land on the Moon. Cernan later said that the ascent module was under-fueled to discourage the crew; NASA was also still optimizing the lunar module engines and testing the computer-assisted landing system back on Earth. In any case, the crew was not carrying equipment for a moonwalk.

Apollo 10 low over the lunar surface
Apollo 10 low over the lunar surface This view of the Moon's surface was taken from the Apollo 10 lunar module during a test descent to within 16 kilometers of the surface. An attitude control thruster can be seen in the foreground. NASA

The three astronauts spent the rest of their time in orbit tracking lunar landmarks and imaging the surface. They fired their service module engine to return home on 24 May and splashed down in the Pacific Ocean on 26 May, where they were retrieved by the USS Princeton.

Throughout the mission, the crew conducted several live color TV broadcasts, giving the world an in-depth look at conditions inside an Apollo spacecraft. Apollo 10 was also memorable due to the crew choosing the call signs Snoopy and Charlie Brown for the lunar module and command module, respectively, which led to their adoption as unofficial NASA mascots. To this day, NASA offers the Silver Snoopy award for employees and contractors who make outstanding contributions to mission safety.

Apollo 10 Timeline

EventTime (UTC)Date
Liftoff16:49:0018 May 1969
Earth orbit insertion17:00:5318 May 1969
Translunar injection19:28:2018 May 1969
CSM separation from Saturn V upper stage19:51:4218 May 1969
CSM docked with LM/Saturn V upper stage20:06:3618 May 1969
CSM/LM separation from Saturn V upper stage 16:45:0018 May 1969
LOI burn20:44:5421 May 1969
Stafford and Cernan enter LM15:5122 May 1969
LM undocking19:00:5722 May 1969
LM descent burn17:48:0022 May 1969
LM radar acquisition of surface21:21:2222 May 1969
LM closest approach to surface21:40:3322 May 1969
LM ascent stage/descent stage separation23:34:1622 May 1969
LM ascent burn23:44:0222 May 1969
CSM/LM docking03:11:0223 May 1969
LM ascent stage jettisoned05:13:3623 May 1969
Transearth injection burn10:25:2824 May 1969
CM/SM separation16:22:2626 May 1969
Entry interface16:37:5426 May 1969
Drogue parachute deployed16:46:1826 May 1969
Main parachute deployed16:47:0526 May 1969
Splashdown16:52:2326 May 1969
Crew onboard recovery ship 17:3126 May 1969

Apollo 10 Cost

NASA estimated the following direct costs for Apollo 10. Full costs of the Apollo program can be found on the "How Much Did the Apollo Program Cost?" page.

original $inflation adjusted $
Command & Service Module$55 million$463 million
Lunar Module$40 million$337 million
Saturn V Launch Vehicle$185 million$1.6 billion
Operations$70 million$589 million
Total$350 million$2.95 billion

Inflation adjusted to 2019 via NASA's New Start Index (NNSI). Source: "History of Manned Space Flight." February 1975. NASA Kennedy Space Center. Located in NASA HQ Historical Reference Collection, Washington, D.C. Record Number 18194. Box 1.

Resources

Project Apollo

Starting with Apollo 7 in 1968 and culminating with Apollo 17 in 1972, NASA launched 33 astronauts on 11 Apollo missions. Twelve humans walked on the Moon.

Recovering the Crew After Apollo 10's Splashdown
Recovering the Crew After Apollo 10's Splashdown The crew of the Apollo 10 exists the command module after a successful splashdown. NASA