AGC - Apollo Guidance Computer

A question was asked, "What is AGC?"

Well having worked with communication equipment I probably would have answered, "Automatic Gain Control", but the question was in reference to the Apollo Moon Landings.

A better answer would then be , "AGC - Apollo Guidance Computer."

Pause......

What is an "Apollo Guidance Computer?"

Something that warns you when it is overloaded with data from the RADAR Altimeter when you are trying to land on the Moon.
- LRK -
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http://history.nasa.gov/alsj/a11/a11tcdb.html*
The Apollo 11 Technical Crew Debriefing July 31st 1969*
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*Aldrin*
There are no discrepancies noted in any of the systems that were checked throughout the first 4 minutes. The RCS was surprisingly high in its quantity indications. The supercritical did tend to rise a little bit after ignition and then it started back down again. I don't recall the maximum value that it reached. I guess the first indications that we had of anything going wrong was probably around 5 minutes, when we first started getting program alarm activities.

*Armstrong*
We probably ought to say that we did have one program alarm prior to this; sometime prior to ignition, that had the radar in the wrong spot. In any case, as I remember, we had a 500 series alarm that said that the radar was out of position, which I don't have any way of accounting for. Certainly the switches were in the right positions. They hadn't been changed since prelaunch. But we did, in fact, go to the descent position on the antenna and leave it there for a half a minute or so, and then go back to AUTO and that cleared the alarm. After 5 minutes into descent, we started getting this series of program alarms; generally of the series that indicated that the computer was being overloaded. Normally, in this time period, that is, from P64 onward, we'd be evaluating the landing site and checking our position and starting LPD activity. However, the concern here was not with the landing area we were going into, but rather whether we could continue at all. Consequently, our attention was directed toward clearing the program alarms, keeping the machine flying, and assuring ourselves that control was adequate to continue without requiring an abort. Most of the attention was directed inside the cockpit during this time period and in my view this would account for our inability to study the landing site in final landing location during final descent. It wasn't until we got below 2000 feet that we were actually able to look out and view the landing area.

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Alright, that wasn't fare.
Check out the information at Wikipedia link.
- LRK -

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http://en.wikipedia.org/wiki/Apollo_Guidance_Computer
Apollo Guidance Computer
From Wikipedia, the free encyclopedia

The *Apollo Guidance Computer* (*AGC*) was the first recognizably modern embedded system , used in real-time by astronaut pilots to collect and provide flight information, and to automatically control all of the navigational functions of the Apollo spacecraft . It was developed for the Apollo program by the MIT Instrumentation Laboratory under Charles Stark Draper , with hardware design led by Eldon C. Hall . Based upon MIT documents, early architectural work seems to come from J.H. Laning Jr., Albert Hopkins , Ramon Alonso ,^[1] and Hugh Blair-Smith .^[2] The actual flight hardware was fabricated by Raytheon , whose Herb Thaler ^[3] was also on the architectural team.

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Check the External links section near the bottom of the page as well. - LRK -
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I watched a show on TV this week where they showed the ladies doing the wiring on the computer modules. To hard-wire the logic, two ladies worked together, one person on the front, one at the back, with a tape controlled indexer that positioned a ring to put a needle through that pulled the wire through. After looping around the correct post the ring was indexed again for the lady on the receiving side to pass the needle back through the next spot to the person on the front side. After the wire lacing was done, the wires were stripped of insulation at the posts and spot welded. Then the whole module was run through a logic tester to check for the correct response.

This was back at the beginning of integrated circuits with only a few transistors on each chip.

I have module from a UNIVAC Digital Trainer I got to resurrect from surplus back in the early 70's and these little modules had only two NOR gates made from two transistors, some resisters and some diodes.

Many of these modules were put in a line to make up a register for holding instruction words. I gave the trainer back to surplus when I left the training command but kept one of the modules. Here is a web shot of the module.




- LRK -
http://ed-thelen.org/comp-hist/BRL64-u.html
Example of an oldie.
- LRK -



Thanks for looking up with me.

Larry Kellogg

Web Site: http://lkellogg.vttoth.com/LarryRussellKellogg/
BlogSpot: http://kelloggserialreports.blogspot.com/
RSS link: http://kelloggserialreports.blogspot.com/atom.xml
Newsletter: https://news.altair.com/mailman/listinfo/lunar-update

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http://archive.computerhistory.org/search/
Search for "APG" or Apollo Guidance Computer.
Should show some of the logic modules.
- LRK -
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http://www.computerhistory.org/corphist/view.php?s=refs&id=223&PHPSESSID=23990d493c9ac123ddc1b5ccd9aa65b2
*Title:* Fairchild Micrologic in the Apollo Guidance Computer
*Author:* Eldon Hall, et al.
*Created:* 1965 ca.
*Publisher:* Various
*Cataloguer:*
*Copyright:*

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*Reference:* The decision by MIT's Instrumentation Laboratory in 1962, to design the Apollo Guidance Computer using integrated circuit logic devices was critical to the AGC success and a key moment in the history of computing.

Eldon Hall's book "Journey to the Moon" recounts this decision process:
"Journey to the Moon:The History of the Apollo Guidance Computer" (1996)
AIAA (American Institute of Aeronautics & Ast) ISBN:156347185X
http://www.amazon.com/gp/reader/156347185X/ref=sib_dp_pt/102-5159419-4410516#reader-link

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http://www.klabs.org/history/history_docs/mit_docs/1716.pdf

A Case History of the ACG Logic Integrated Circuits
http://www.klabs.org/history/history_docs/mit_docs/1716.pdf

This pdf is a case history of the integrated circuit used for the logic in the Apollo Guidance Circuit written by Eldon Hall in December 1965. Achieving the required goals of low weight, volume, and power coupled with extreme high reliability necessitated the use of one single, simple integrated circuit for all logic functions. A brief description of the evolution of the computer design is given along with a general discussion of some of the engineering and design problems which arise with the use of a standardized semiconductor monolithic integrated circuit.
Note: The f i r s t prototype computer was operating in July 1963 with the Raytheon built flight computer operating in January 1964.

The page notes that MIT/IL had placed an order with Texas Instruments for 64 ICs at $1000 each in 1959. They were the Kilby mesa process Solid Logic devices. That TI order was not delivered until late 1962. The document also shows copies of purchase orders placed with TI, Westinghouse, Transitron and Motorola for alternate source devices.

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http://www.klabs.org/richcontent/Misc_Content/AGC_And_History/PartsAnalysis/PartsAnalysis.htm

NASA Office of Logic Design

A scientific study of the problems of digital engineering for space
flight systems,
with a view to their practical solution.

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Apollo Guidance Computer

Block 2 Parts Analysis

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You may find reading the comments under this post interesting and informative. - LRK -
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http://www.bautforum.com/showthread.php?t=1422
Bad Astronomy and Universe Today Forum
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I was reading JayUtah's post (CosmicDaves 32 Questions) regarding AGC code, and in my desperate impatience to see some, did some Google work. I drummed up the following link:
http://verdade.no.sapo.pt/moon/landing_hoax.html
Lists some info regarding the AGC, and also has a (rather scruffy) Jpeg of a tiny portion of code. This appears to be part of a larger hoax site I've not seen before, and discusses other conspirasist (sp?) theories. Unfortunately I cant find a way back to a 'main' page [img]/phpBB/images/smiles/icon_frown.gif[/img]

Jay, please post any code you can! If anyone else has more info regarding the computer systems used, please post here also...

Cheers,
widoxm

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WHAT THE MIND CAN CONCEIVE, AND BELIEVE, IT WILL ACHIEVE - LRK

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