A Computer For Apollo

When the space program was started back in the beginning of the 1960’s how to guide the spacecraft in space was a complete unknown.  The problem of calculating burns and orbital insertions was a nontrivial one. At the time all flight control had been analog and in 1960, the computers filled up buildings.  When the call came to go to the moon, one thing was clear though.  A computer small enough to fit on the spacecraft was going to be essential.  That computer would be the Apollo Guidance Computer(AGC).

Recently this post was posted on Hackaday.

Decoding Rediscovered Rope Memory From the Apollo Guidance Computer

What amazing to me was that the computer was ever let out into the wild in the first place.  This is, after all first flight hardware.

http://www.fin24.com/Tech/News/tshwane-geek-tracks-down-first-apollo-computer-20160902

I was intrigued first by the hard wired nature of the software and the use of round memory cores.  I also was interested in the used of integrated circuits.  So I did some digging on this amazing 1960’s hardware.

Here’s a good video of the story of the Apollo Guidance Computer.

https://en.wikipedia.org/wiki/Apollo_Guidance_Computer

Here’s a very early video about the ongoing development of the AGC.

 

Note the DSKY and how it differs from the actual used flight hardware.  Also look a the various construction techniques used to fabricate the components.  At the time the PC boards fabrication techniques were in their infancy and the boards could delaminate, not something you want in a spacecraft.

In fact the construction methods for the AGC come from the robust requirements and hardware from the Polaris SLBM program. This meant doing things that were expensive, but robust.  For instance the wire wrap backplane.  Along with the potted components.  Of course liquid “leakage” cause the entire computer to be sealed hermetically.

Here’s a couple of videos from the computer museum in 1982.

Here’s another video on this remarkable machine.  I find it interesting to see the intermediate steps in technology and how things develop.  Yes better methods of doing things emerge and gain dominance, but when things are changing the winner isn’t always clear.  In the 1960’s the tube was still prevalent for most electronics.  The solid state transistor was still exotic and IC chips were expensive exotics.  So all of the stuff in the videos was the cutting edge for the 1960’s.

 

Here are some links from NASA and other sources.  There is a lot of information on these computers.

http://history.nasa.gov/computers/Part1-intro.html

http://klabs.org/history/history_docs/mit_docs/agc.htm

http://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/apollo/public/visual3.htm

http://ed-thelen.org/comp-hist/vs-mit-apollo-guidance.html

http://www.computerweekly.com/feature/Apollo-11-The-computers-that-put-man-on-the-moon

http://www.ibiblio.org/apollo/ForDummies.html

http://www.drdobbs.com/architecture-and-design/one-giant-leap-the-apollo-guidance-compu/184404139

Of course the manual is always useful.

Click to access aoh-v1-2-02-g+n.pdf

 

Because it’s always interesting to see different approaches to the same problem, here’s a MIT link to the Soviet approach to the problem.

http://web.mit.edu/slava/space/interview/interview-przhiyalkovsky.htm

This was a fun little trip through a piece of space hardware that I had not been familiar with.  I learned some things about engineering approaches that I hadn’t seen before, like rope memory.  It’s also important to understand the shoulders that you are standing on when you move forward. If you know what’s been done you have a better feel for what yo can do.  Also, the 1960’s were when many of the technologies that drove the microcomputers of the late 1970’s came of age.  It’s because the DOD and others were willing to pay 1000’s of dollars for those crude IC’s that the silicon companies were able to drive the technologies forward into the micro processor in the 1970’s. So even if the AGC was not important for itself, the little computer was important for what followed. We should never laugh at the accomplishment of those that came before us.  They started without the tools we take for granted and did it anyway.