LM Descent to the Moon - Part 7 - Crew Comments (1969)

(Apollo 11 LM - DOI to Touchdown Crew Debriefing, 1969)

[The following is a partial reprint of NASA's Apollo 11 crew interviews /1/ during their quarantine that took three weeks after their splash down. Apollo 11 CM splashed down on July 24, 1969.]

Figure 1. ARMSTRONG, COLLINS and ALDRIN.
The Apollo 11 mission, launched on July 16, 1969 and returned to Earth on July 24, 1969. Aboard the space craft were astronauts Neil A. Armstrong, commander; Michael Collins, Command Module (CM) pilot; and Edwin E. Aldrin Jr., Lunar Module (LM) pilot

LM Descent to the Moon - Part 6 - Programming (1971)

(Apollo Lunar-Descent Guidance, 1971)

[The following MIT / NASA's 1971 text, partial reprint of the reference /0/, describes the descent algorithms used in the Apollo Lunar Module computer program (Luminary version 099/1A, about 63,000 lines of YUL assembly code) and flown summer 1969. This paper actually describes an advanced version of the algorithm which was not used since the older version which was more tested at that time (1969) was good enough for the job. What so ever, the text gives a good glance to the manned planetary descent programming.]

Figure 1. Components of the Lunar-Descent Guidance System.

LM Descent to the Moon - Part 5 - Powered Landing Maneuver (1964)

(LEM Powered Landing Maneuver, 1964)

[This is a partial reprint of a 1964 technical paper from MIT/NASA, which explains the mathematics behind the 1960's lunar landings. See /1/ for details. LM was called LEM (Lunar Excursion Module) those days and the first landing was to be done summer 1969, 5 years after this paper was written. The strength of this algorithm is that it is real time adaptive to the variations of the parameters from different sources (and also errors). This algorithm was called "E Guidance" due to the E matrix used in it. The basic LM descent guidance logic was defined by an acceleration command which was a quadratic function of time and was, therefore, later termed "Quadratic Guidance". ]

Figure 0. Look angle "lambda" is relative to the thrust axis

LM Descent to the Moon - Part 4 - Descent Monitoring

REAL-TIME DESCENT MONITORING AND ANALYSIS


During the real-time situation, monitoring of the spacecraft systems and of the trajectory was performed continually both on board by the crew and on the ground by the flight controllers. The real-time monitoring determined whether the mission was to be continued or aborted, as established by mission techniques prior to flight. The real-time situation for the Apollo 11 descent is described here.

LM (Apollo 11) DOI (Descent Orbit Insertion) is done 180 degrees before PDI (Powered Descent Initiation)

LM Descent to the Moon - Part 3 - Practice (Apollo 11, 1969)

APOLLO 11 DESCENT AND LANDING SUMMER 1969

Feb. 24, 1970, Russell A. Larson (left, Massachusetts Institute of Technology project manager for the lunar module flight program) and David G. Hoag (director of the Apollo Group at MIT’s Draper Lab) in the LM mock-up or simulator.

LM Descent to the Moon - Part 2 - Hardware

This part (2) will handle the LM descent hardware in more detail. See part 1 for more general description of the Apollo Lunar Module landing theory and software.

LM Descent to the Moon - Part 1 - Theory and Software

The LM descent from the CSM (Command Service Module) parking orbit (approximately 62 by 58 nautical miles above Moon surface) is illustrated in the following figure. After the LM and the CSM have undocked and separated to a safe distance of several hundred feet, the LM performs the DOI (Descent Orbit Insertion), which is the first and simplest of the two descent maneuvers.

LM Descent