posted 11-28-2021 03:02 AM               

...despite the AGC technology deployment, no one has been able to design a physical connection between the CM's CGC (Command Guidance Computer) and the LM's LGC (Lunar Guidance Computer). Since the CGC is the primary computer throughout the mission, this means that the astronauts must manually enter position and data from one computer to another, a cumbersome and time-consuming task, to top it off, the reference angles of the two vehicles are different, further complicating the LM IMU alignment procedure during in-flight activation.

posted 11-28-2021 07:33 AM               

While each mission to the Moon carried two Apollo Guidance Computers, one in the command module, the other in the lunar module, with the hardware of the two machines nearly identical, the software (programming) for each enabled them to achieve their distinctive functions. The LM AGC was supplemented in the later stages of the descent by readings from a radar altimeter that bounced signals off the Moon’s surface.

Due to the way the two spacecraft were orientated while they were docked, the “up” reference for each AGC was different. A roll to the right for the CM would be a roll to the left for the LM whilst docked, so a gimbal angle for the Command Module needed to be interpreted for the Lunar module.

posted 11-28-2021 09:03 AM               

So according to your statements, if I understand well: a physical link was not necessary between the two computers (AGC and LCG) even if she would be only for the transfer of flight data in case of force majeure as in the flight of Apollo 13.

But was it nevertheless possible, in the case where the second computer could make the conversion of angles and roll of the first.

posted 11-28-2021 06:49 PM               

LM Platform Alignment

During LM activation IMU platform alignment was a top priority so that the LM could be used to perform burns to place the spacecraft on a return to Earth trajectory. Aligning the LM platform before the CM platform alignment was lost, due to the CM power-down, was a challenge. LM PGNS activation was nominal.

A CM to LM docked alignment was performed. The CM pilot provided CM IMU gimbal angles to the commander for the docked LM alignment. The procedure required some pencil and paper calculations and the commander asked Mission Control to do the math to ensure accuracy. The crew reported that debris surrounding the spacecraft made it impossible to recognize constellations needed to perform a CM IMU or LM IMU optical alignment using star sightings.

posted 12-04-2021 03:02 AM               

In the middle of the article, it is written:

Curiosamente, y a pesar del despliegue tecnológico que suponía el AGC, nadie fue capaz de diseñar una conexión física entre el CGC del módulo de mando y el LGC del módulo lunar. Puesto que el CGC era el ordenador primario durante toda la misión, eso implicaba que los astronautas debían introducir los datos de posición y orientación manualmente de un ordenador a otro, una tarea ciertamente tosca que consumía mucho tiempo (para colmo, los ángulos de referencia de los dos vehículos eran diferentes, complicando todavía más el procedimiento de alineación de la IMU del LM cuando se activaba en vuelo).

posted 12-04-2021 08:00 AM               

Curiously, and despite the technological deployment of the AGC, no one was able to design a physical connection between the command module's CGC and the lunar module's LGC. Since the CGC was the primary computer throughout the mission, this meant that the astronauts had to manually input position and orientation data from one computer to another, an admittedly crude and time-consuming task (to top it off, the reference angles of the two vehicles were different, further complicating the LM IMU alignment procedure when activated in flight).

posted 12-04-2021 08:55 PM               

Daniel Marín is an astrophysicist by training and passionate science communicator. He has received the 2012 Bitácoras Award and the 2015 20Blogs Award for the best blog in the science category, as well as the 2013 Naukas Award for the best popular science blog. Collaborator of the magazine Astronomy, he is a member of the AAGC (Astronomic Association of Gran Canaria) and Mars Society Spain. From time to time he usually attends the launch of a spaceship.