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Forum:	Hardware & Flown Items
Topic:	Identifying an Apollo Guidance Computer

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Your Reply: HTML is ON UBB Code is ON Smilies Legend	[QUOTE]Originally posted by apollo16uvc: [B]What an incredible collection Steve! I see you got a DSE on display. Just to clarify, it does not have any tape right? If it does, even a little bit, that may be interesting to get digitized. As long as it has the heads this should be possible... [/B][/QUOTE]
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<table border=0 cellpadding=0 cellspacing=0 width="600"><TR><td bgcolor="#000000"><TABLE BORDER=0 cellpadding=4 border=0 cellspacing=1 WIDTH="100%"><TR bgcolor="#660000"><TD COLSPAN=2><CENTER>T O P I C     R E V I E W</CENTER></TD></TR><TR bgcolor="#494949"><TD valign=top>Jurvetson</TD><TD>So happy to see the details and background research on the Apollo Guidance Computer (AGC) being <A HREF="http://www.collectspace.com/ubb/Forum36/HTML/000560.html">offered by RR Auction</A> from Don Eyles' collection. I have a similar one, with Serial Number "Ray 26" instead of "Ray 8". Does anyone know the source of the details on what each was used for... and the memory modules too? Thanks!</TD></TR><TR bgcolor="#333333"><TD valign=top>mstewart</TD><TD>Steve, I led the restoration of Jimmie Loocke's AGC and did all of the background research for this AGC and its modules. I'd be happy to help piece together some of the history of your AGC! I'll start digging into it tonight. I'll need to know the part numbers on each of your rope modules to pin down the exact program.For starters, though, am I correct in thinking that your AGC has part number 2003993-051?Actually, scratch that -- it appears that by August 31, 1970, this computer had been modified to 2003993-091, which is beyond the scope of the compatibility charts I have. Interesting!</TD></TR><TR bgcolor="#494949"><TD valign=top>SpaceAholic</TD><TD>If he is alluding to his unit repurposed for the F-8 fly by wire testing that may provide a clue.</TD></TR><TR bgcolor="#333333"><TD valign=top>mstewart</TD><TD>The trail of drawings from NARA starts to peter out around Apollo 14 or so, and we don't have anything dedicated explicitly for DFBW. The -091 change is really interesting, and I haven't figured out yet exactly what was changed about the computer for for that.If it still has the DIGFLY ropes in it, then I'd expect their part numbers would *probably* be something around 2010802-5xx or 2010802-6xx, depending on whether the DFBW ropes or the Skylab ropes were released first. We have so little information about DIGFLY that I'm not even entirely sure how many rope modules it took up! I do know that it contained all of the original AGC self-test code that was stripped out of the manned flight ropes to make space, so perhaps it was not all six.Also, for what it's worth, LM-12 flew with a 2003993-091 AGC (likely, but not definitely, s/n RAY 56), so the change wasn't DFBW-specific.Edit — Ah, got it. -091 was a combination of changing the voltage fail alarm circuit limits, as well as installation of the channel 77 restart monitor box onto the test connector.</TD></TR><TR bgcolor="#494949"><TD valign=top>Jurvetson</TD><TD>Thanks y'all! It's P/N 203993-091, S/N Ray 26.The memory modules are all 2003972 Memory B1 -011 Ray 86 Memory B2 -091 Ray 87 Memory B3 -111 Ray 115 And the memory jumper modules are 2003076 with -021 and -031, and S/N Ray 1, 2 and 5.And yes, Scott, this this AGC++ you connected me to (it is connected to IMU, coolant systems and several other boxes besides the AGC). Any clues here would be valued (especially the original uses).</TD></TR><TR bgcolor="#333333"><TD valign=top>mstewart</TD><TD>Ah, okay, very interesting! 2003972-011, 2003972-091, and 2003972-111 together make up Aurora revision 88, which was the final release of the Lunar Module system test program.Is one of the boxes a Coupling Data Unit? If so, what's the part and serial number on that?</TD></TR><TR bgcolor="#494949"><TD valign=top>SpaceAholic</TD><TD> <BLOCKQUOTE>quote:<HR>Originally posted by Jurvetson: this this AGC++ you connected me to <HR></BLOCKQUOTE> Very likely part of the DFBW pallet then.</TD></TR><TR bgcolor="#333333"><TD valign=top>mstewart</TD><TD>I traced it a little bit further... as of October 7, 1970, it was still an unassigned flight-quality LGC, located at AC Electronics.Interestingly, this AGC had three NOR gates fail during factory vibration testing in late 1968.</TD></TR><TR bgcolor="#494949"><TD valign=top>Jurvetson</TD><TD>I will look for a "Coupling Data Unit". I do see: <UL TYPE=SQUARE><LI>"DFCS Interconnect Harness A" with "STAGE III SIM & FLT" and S/N 2 Part No. "MX117926 NASA/FRC DFCS"<LI>"Interface Box Assembly" each with "STAGE III SIM & FLT" S/N 1 Part No. "MX117925 NASA/FRC DFCS"<LI>Apollo G&N System Power & Servo Assembly - LM P/N 6007200 S/N AC 14 Cont. No. NAS 9-497<LI>IMU sphere with P/N 2018808 Rev E, Cured 1-67 Mutron Corp.</UL></TD></TR><TR bgcolor="#333333"><TD valign=top>Jurvetson</TD><TD>And at minute 2 of this impromptu video, you can see the whole rig: <center><iframe width="400" height="225" src="https://www.youtube.com/embed/BZWO484gv1g?start=122" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen>

Jurvetson

And I just posted a bunch of photos here.

mstewart

Whoa, thanks for sharing the pictures, those are great! No doubt about it, that's the DFBW AGC and navigation system.

There's a lot of really interesting things about this. I think the number you're seeing on the IMU is actually 2018806; that is the part number for the insulation for the left hand case heat exchanger.

2018808 is a weight used to balance the stable member.

The IMU itself should be 2018601.

The Coupling Data Unit is on the shelf directly above the AGC. Its part tag will be on the front left corner of the top cover, when facing the big harness that plugs into it. It looks pretty well obscured by the shelf above it, unfortunately.

It's really interesting that they've removed the DFBW ropes and gone back to Aurora — I wonder what it was that they were testing that DIGFLY couldn't do. This G&N System Inventory from 1969 indicates that these modules constituted "Set 8" of Aurora, and were assigned to (and very likely installed in) LM-8. The AGC installed in LM-8 at that time was s/n 49, though.

As for your AGC — as far as I can tell it didn't have any formal assignments before DFBW. Its designation was computer C-12. Here's what I've been able to find of its history:

It was most likely born at the very end of 1966, or in early 1967.

On July 25, 1967, a technical report was written describing a restart that happened on C-12. (The title of this report is listed on this PDF page 84, but we don't have the report itself). Apparently, at this time, it was stationed at Grumman for potential use in a LM. It may have been installed in a LM at some point, but right now I think we only know dash numbers, not serial numbers, for that time period.

According to page 244 of the same document, in early-mid 1968 it was affected by ECP 696, "Recycle of AGC's for Incorporation of Changes." Presumably, up until this point, it had stayed at Grumman, and had not been kept up to date with hardware modifications that had been made. It was shipped to AC or Raytheon for updates.

In June 1968, presumably while being re-tested after the ECP 696 changes, two of its NOR gates failed due to loose conductive particles during vibration testing. Four months later, in October, a third failed in another vibration test. These are listed on this PDF page 41.

After that it seems like it was kept at AC Electronics as a flightworthy computer. This memo from August 31, 1970 lists it as a spare at AC.

This memo from October 6, 1970, which discusses hardware available for use for Skylab, also mentions it as a flightworthy spare located at AC.

I can't speak much to the other parts, unfortunately. All of the MX* stuff is non-Apollo, and the National Archives don't have the drawings (or at least, not in the same collection as all of the Apollo drawings). It looks like custom stuff built for the DFBW tests.

I'll keep an eye open and let you know if I find anything further!

On edit: Hahaha, nevermind, it was installed in a LM! As of December 1967, it was installed in LM-2 as part of guidance system 608, as shown on PDF page 31 of this System Status Report.

Also, your PSA, s/n 14, was assigned to G&N 618 for LM-14, according to PDF page 373 of that AC Electronics Final Report.

Jurvetson

This is absolutely incredible. I am in awe of your research skills and so grateful. Thank you, thank you, thank you.

So, amazingly, my AGC started its life in the Lunar Module that is on display in the Smithsonian... wow.

One question, when you say the memory modules "were assigned to (and very likely installed in) LM-8" that means they contain the software for the Apollo 14 Lunar Module... and I am curious to hear more about the likely installation scenario (tested and removed for some reason?). Thanks!

Ken Havekotte

Absolutely an incredible tour of remarkable aerospace hardware from the world's space faring countries of the U.S. and Russia. Thanks for sharing, Steve, as I very much enjoyed it with everything nicely displayed!

mstewart

Thanks, and it's my pleasure!

The Aurora rope modules don't have any flight software (Apollo 14 or otherwise) in them, unfortunately. But what they do have is a large set of very extensive system tests for all of the LM hardware. There's a large chunk of code dedicated to self-testing the computer -- it checks every control pulse of every instruction, writes to and reads from every memory location, etc. There are a bunch of inertial test routines which torque the IMU around, where the operator verifies the correct alignment was achieved based on FDAI displays. There's routines that will fire each of the RCS thrusters in a sequence to make sure they all work and the mapping is correct, routines that take the descent engine through various throttle settings, etc.

All of this test code was extremely useful for checking out LMs, but also took up a lot of space in the limited memory of the AGC. Some of the computer self-test routines (the extensive divide/multiply tests) were deleted from the Apollo 5 flight ropes to make room, and by the time of Apollo 9 pretty much all of the test code had been deleted to fit all of the flight code in.

Since the flight ropes didn't have the checkout programs, Aurora ropes were what was used on the ground during LM bringup and checkout. Any applicable tests would have been re-run after each hardware change that affected the PGNCS. I don't know the exact timeline, but I believe the Aurora ropes lived inside the LMs for the vast majority of their life on the ground, and were replaced with the flight Luminary ropes only shortly before launch.

apollo16uvc

What an incredible collection Steve!

I see you got a DSE on display. Just to clarify, it does not have any tape right?

If it does, even a little bit, that may be interesting to get digitized. As long as it has the heads this should be possible...

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