SC Cont: CMC

With the SC Cont switch set the CMC the attitude control of the CSM will be controlled with the onboard PGNS (Primary Guidance and Navigation System). This system has 3 major modes: Free, Hold, Auto. Free will allow the spacecraft to move without any attitude control, whereas hold will command the RCS to hold present inertial attitude. Setting the CMC mode to auto will allow the computer to control the attitude using the DSKY (Display and Keyboard). This is done mostly by using the attitude maneuver subroutine F 50 18. This is brought up by any major program which requests a change in attitude ushc as P40, P41, P23, and P20. The crew is also able to define an attitude maneuver by calling Verb 49 Enter. They then can key Verb 21, 22, 23, 24, or 25 Enter to modify the three registers to display the requested attitude such as +18000. The rows correspond to Roll, Pitch, and Yaw respectively and Enter must be keyed after the entry in each row. Once the desired attitude is entered the operator will key Pro and the display will change from Verb 06 Noun 18 to Flashing Verb 50 Noun 18. When the operator hits Pro again the subroutine will calculate the most fuel efficient path to the attitude and execute it using the RCS. It is important to note that the DAP settings Verb 48 subroutines will greatly affect the speed and accuracy of this maneuver as well as which jets will be used to perform the maneuver. Additionally, crew is able to perform other small maneuvers such as a Passive Thermal Control Roll or holding Orbit Rate at present Attitude by simply changing certain flags in the Flag Soup held in the E-MEM's Noun 01 display. Care must be taken not to overwrite constants which are mission critical, this computer has no const variable definition for overwrite protection.

SC Cont: SCS

The Stabilization Control System serves as a means to manually control the attitude when desired and conserving fuel when possible, while it does save fuel the CMC is still much more fuel efficient for most maneuvers, however, the SCS is more fuel efficient than maneuvering on free attitude control. The SCS takes data from multiple sources: The GDC, SCS related switches, and the BMAGS (Body Mounted Attitude Gyro. Setting the ATT DB (Attitude Deadband) to Max allows for an attitude error of nearly 20 degrees. Setting the Rate switch to High allows an accumulated rate of .5 deg/sec on each individual axis, while rate low maintains a .1deg/sec accumulated rate. This can be zeroed out by going to ATT1/RATE2 on the BMAGs. "The Body Mounted Attitude Gyros, or BMAGs, help to back up to the IMU. The two assemblies are capable of detecting the spacecraft's rate. This information is sent to the Gyro Display Coupler, or GDC, which adds the rate to its current know attitude, updating its knowledge spacecraft's orientation. There are two sets of rate gyros that are referred to as BMAGs one and two. Both of these can be activated or powered off through their rotary switches on MDC-7. Both gyro assemblies are typically caged and determine only the spacecraft's rate. The rate is then sent to the GDC. The three BMAG switches on MDC-1 determine which set of gyros the GDC receives rate data from. Setting a switch to either Rate 1 or Rate 2 determines which BMAG the GDC receives rate from in that axis. BMAG one is capable of being uncaged to determine attitude errors. The center setting of the BMAG switches, Att 1/Rate 2, tells the GDC to accept rate data from BMAG 2 and attitude data from BMAG 1. In order to do this, BMAG one must be uncaged by the ECA. This is done automatically when setting a BMAG switch to the center position." (NASSP Developers)

Virtual AGC

"Here are some other video clips (courtesy of Niklas Beug and YouTube) which take a little longer to watch (20 minutes), but are perhaps even more instructive. Our simulated AGC software has been integrated into the NASSP add-on for the Orbiter space-flight simulator, and is used there to fly simulated Apollo or Apollo-like missions. And you can fly such simulated missions too, using that software, as if you were Neil Armstrong yourself ... assuming you're up the challenge! The videos below show simulated Apollo 11 and 15 lunar landings, using our AGC and the actual original Apollo 11 and Apollo 15 guidance-computer software running on it. Of course, all the fancy graphics is NASSP/Orbiter's and not ours, but the AGC is behind the scenes, helping to run the spacecraft, and the accompanying text describes how the AGC is being used! The Apollo 15 video is quite exciting, as the LM swoops in over the Lunar Apennine Mountains to the landing site in Hadley Rille. (I suppose I should also mention that Nik provided these videos in full HD Quality, though you'll only see a much-reduced quality in the tiny boxes below, so you might want to head over to YouTube itself to watch them, if you want to get the full glory of the things.)" (Virtual AGC Page)