
Apollo Guidance Computer Demonstration, at VCF West 2019 [video] - guiambros
https://www.youtube.com/watch?v=YTk7jyiaE1U
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StringyBob
For anyone who's interested, but not seen them, I'd recommend the full series
of videos at
[https://www.youtube.com/watch?v=9iavKBdPo4U](https://www.youtube.com/watch?v=9iavKBdPo4U)
for a spectacular amount of background info.

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exDM69
This video was (someone else?) flying a moon landing in a simulator with an
FPGA emulated Apollo Guidance Computer.

CuriousMarc's series is about restoring a real AGC.

~~~
djmips
Ultimately, they do the same simulated landing with a real AGC. Ideally, this
video would have been demonstrated with the restored AGC but it wasn't
available.

It's the same people. Mike Stewart was one of the main AGC gurus in the
YouTube series.

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semessier
After looking at various sources I still don't understand whether the manual
mode landing was a necessity because:

\- of the computer overload due to the command module (CM) rendezvous radar
being turned on -> which in turn leading to a messy command queue -> commands
being dropped from the queue being filled -> commands being sent out-of-
sequence -> undefined behavior -> the LM getting of path to the wrong landing
region

\- of a stone field after an otherwise nominally controlled descent.

In addition it seems unclear whether during manual flight control mode there
was still any computer control for attitude, rate of decent etc. active.

~~~
quux
In the final phase of landing the AGC was running a program called P66 which
was a semi-manual mode. The astronaut had direct control of the attitude of
the LM but the throttle was calculated by the AGC to maintain a steady Rate of
Descent (ROD). The astronaut controlled the ROD via a switch.

All the Apollo landings were done with P66, I think the AGC did have the
capability to do a fully automatic landing but none of the crews wanted to try
it.

~~~
semessier
so was it planned then to use P65 (fully automatic) for Apollo 11?

It's still not clear what the actual impact of the messed up command queue had
- none, a few wrong thruster firings or getting the landing phase trajectory
completely wrong?

~~~
semessier
actually answering my own question in part, it's explained at
[https://www.hq.nasa.gov/alsj/nasa58040.pdf](https://www.hq.nasa.gov/alsj/nasa58040.pdf)
pp. 21 ff.

: P65 was apparently planned and there was a velocity error amongst others
leading to a navigation error.

What remains open is what material impact the interupt overload on the command
queue had.

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alephnil
This is the recording of a live stream where the camera was turned on well in
advance. The talk starts at 10:45 into the video.

