Landing the Eagle on the Moon
Uploaded by Ronald W. Cox
This video contains the actual unedited console recording of the communications at mission control as the Apollo 11 astronauts, Neil Armstrong and Buzz Aldrin, piloted their lunar module (LEM) to the lunar surface using a Delco Electronics built Guidance Computer. It is four minutes and thirty seconds in duration. The video is from a Final Approach film by René and Jonathan Cantin (from the NASA Apollo 11 Video Library) and is a side-by-side composite of the landing film and Lunar Orbiter Frame 5076_h3, with a number of craters matched up in the two views.
Phases of the Lunar Landing (numbers are approximate)
The significance of the "attitude hold" and "program 66" noted in the video are referenced here in the recorded history of the landing as follows: "Nevertheless, Armstrong had time to notice that the LPD indicated 'we were landing just short of a large rocky crater with very large rocks covering a high percentage of the surface'". So at MET 102:43:08 (650 feet), after deciding that he could not stop short of the crater, Armstrong flipped the autopilot mode switch from AUTO to ATT HOLD to take manual control of the LM's attitude. He maneuvered to zero pitch to maintain horizontal velocity and skim over the rocky area.
(ATT HOLD meant the digital autopilot's Rate-Command Attitude-Hold mode, in which the astronaut could command an attitude rate by deflecting a joystick. After the stick was released the autopilot nulled rates to maintain the present attitude.)
At MET 102:43:20 (430 feet) Armstrong flicked a spring loaded toggle switch with his left hand, entering the rate-of-descent mode (P66). Now the computer controlled the spacecraft's thrust to maintain a rate-of-descent commanded by the ROD switch. A flick upward slowed the descent by one foot per second; a flick downward increased the descent rate by the same amount. Using the joystick, Armstrong tilted the LM to null out horizontal velocity and bring the LM to a safe area for touchdown. After some "possibly spastic" control motions because dust kicked up by the exhaust plume distorted his perception of translational velocity, at MET 102:45:40, Armstrong landed the spacecraft safely in the Sea of Tranquility."
Related Links
GM Goes to the Moon
1969, Getting to the Moon
1971, Getting Around on the Moon
Atwood, Donald Jesse Jr
Apollo 11 Lunar Surface Journal: Program Alarms
NASA Office of Logic Design: "Tales from the Lunar Module Guidance Computer" by Don Eyles
"The Apollo Guidance Computer: A Users View" by David Scott
NASA Office of Logic Design: Console Audio of Apollo 11 Landing (over 1 hour duration)
NASA Apollo 11 Video Library
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