Apollo Guidance Computer (AGC) Restoration for 50th Anniversary of Apollo 11

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Winston

Winston

Lorenzo von Matterhorn
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Apollo Guidance Computer (AGC) Restoration for 50th Anniversary of Apollo 11

The one being worked on to restore it to functional status is from the first man-rated Lunar Module LTA-8, the one on display at Space Center Houston:

https://heroicrelics.org/space-ctr/lta-8/index.html

Most of this AGC was NOT potted so it's possible to work on it. Beautiful hardware. They are short on documentation for various AGC development tools (hardware), so they have to reverse engineer them to attempt to get them working. Fascinating video.

 
The guy filming AGC restoration. Quite an electronics restorer himself!:

 
5.0V voltage reference made from discrete components measures 4.999(5) volts after 50 years! Impressive alarm module tested and works perfectly. Copy of receipt for this exact AGC with price and historic signature shown starting at 17:16.

 
What an absolutely incredible effort.

Apollo AGC Part 6: Restoration update, 10 layer PCB design to replace the massive, impressive external solderless breadboard and wiring mess previously seen used to simulate the AGC's DSKY (display and keyboard) and another PCB for the Beagleboard-based rope memory emulator, eBay connector machining to fit, IC reseating, X-raying potted erasable memory module to find the wiring break(s)



Basic theory of operation, period manufacture (incredible) starting at 14:00, and stress test burn-in. I think this must be an earlier version of the AGC. All of the completely custom tooling and machines, techniques, automated test equipment, etc., show the extreme magnitude of just one part of the groundbreaking technologies used in the Apollo program.

 
Apollo AGC Part 8: Restoration Update and a Blinkenlight AGC

 
Here's part of a great Apollo documentary series "Moon Machines" that was on Dsicovery/Science Channel. This one about developing the Guidance Computer.

Rope core memory.....wow. Tedious is too insignificant of a word for that process as used for Apollo, and the impact of detecting and undoing a single mistake anywhere along the way.

 
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Apollo AGC Part 10: Mike demonstrates flying P63, lunar landing, using his new AGC test monitor

 
Apollo AGC Part 11: Samtec manufactures NASA-spec contacts for our AGC

 


It's alive and running programs selected via the virtual (for now) DSKY!!!

 
"There was a short and an open. You'd think they'd cancel out. Ha, ha."

All of these guys are brilliant, especially Mike who did tons of hardware-related work and wrote the virtual DSKY and other troubleshooting software seen being used on the laptop as well.

Apollo AGC Part 14: Bringing up fixed rope memory

 
Apollo AGC Part 16: Digging into potted module B11
 
The AGC restoration team consists of Mike Stewart (creator of FPGA AGC; no wonder he has such deep knowledge of the AGC; he's recreated it in a FPGA!), Carl Claunch, Marc Verdiell (CuriousMarc on YouTube) and Ken Shirriff. The AGC that's being restored belongs to a private owner who picked it up at a scrap yard in the 1970s after NASA scrapped it!

Apollo AGC Part 17: Carl's DSKY hook up, and Ken mines a bitcoin

 
Wow, what a PITA. Luckily, they have beautiful technical documentation which, considering the number of components involved in the Apollo Program and the extremely rushed pace of the program is another factor to greatly admire.

Apollo AGC Part 18: Module B11 rescue, Apollo 13 style

 
In the next part (pending), they play with it!

Apollo AGC Part 19: Restoration complete

 
Apollo AGC Part 20: Electroluminescent DSKY display and PIPA accelerometers


Apollo AGC Part 21: 1960's best video game - we land on the moon with the real AGC

 
Another bad diode. Hope this isn't a trend. The diode type and vendor source for the diodes in this module type was banned from use in the later AGC builds! There are 28 of these diodes in the module. They will be replaced only when they fail. Once again, the great Apollo technical documentation is shown, incredible considering the size of the Apollo program and how everything was being done in parallel due to the time constraint.

Apollo AGC Part 22: Module B11 fails again!

 
Your Smart Toaster Can’t Hold a Candle to the Apollo Computer
Despite what everyone says about the power of modern devices, they’re nowhere near as capable as the landmark early NASA system.
JUL 16, 2019

https://www.theatlantic.com/science/archive/2019/07/underappreciated-power-apollo-computer/594121/

Michio Kaku, the physicist and popular author, put it like this: “Today, your cell phone has more computer power than all of NASA back in 1969, when it placed two astronauts on the moon.”

But these just-so sayings obscure the real power of the Apollo computer. Of course, any contemporary device has vastly more raw computational ability than the early machine, but the Apollo computer was remarkably capable, reliable, and up to the task it was given. You could not actually guide a spaceship to the moon with a smart doorbell.

To understand how significant the Apollo system was, and why its tiny amount of raw processing power is irrelevant, you only have to listen to the OG computer programmer and volunteer NASA historian Frank O’Brien, who has spent his life lovingly detailing the functions of the Apollo Guidance Computer. O’Brien’s father was a pilot, so Frank became a military brat. He was interested in computers from an early age, and when one of his dad’s old friends rose up the ranks at NASA, he came into possession of the technical manuals that governed the operation of the computer.

“At 13 years old, I get a box on Christmas, around two feet on a side, weighed a million pounds,” O’Brien told me. “I open it up, and it had all the technical manuals on Apollo. You had tons and tons of kids looking at Playboys; I was reading about guidance computers.”

Since then, he’s spent countless hours learning precisely how these machines worked. Even as a teenager, he could fly NASA’s Apollo simulator. As an adult, after earning a computer-science degree and working a long stint as a corporate programmer, he wrote the book The Apollo Guidance Computer, an ode to the machine.

[big snip]

Given all this, perhaps it’s not surprising that O’Brien takes umbrage at the idea that a microwave or calculator could be considered “as powerful” as the Apollo computer.

“How do you define power?” O’Brien asks. “It’s great to say, ‘This machine is so powerful.’ What do you mean by that?”

For him, it’s not about the raw number of transistors, but the machine fitting the mission. Capability, not power. “We had to get to the moon, get down, and get back, autonomously. They hit their targets of being accurate after a quarter million miles, hitting a target within 500 to 600 feet and one-tenth of a foot a second,” O’Brien said. “And you go, ‘My watch is more powerful.’ No, it is not.”

The lesson, maybe, is simple: If your phone is so much more powerful than the computers that put humanity on the moon, then why are you just staring at Instagram all day? Computation is means, not end.

Basic summary of the AGC restoration:



Apollo AGC Part 23: Flying realistic Apollo 11 moon landings with the Apollo Guidance Computer

 
First, thanks for posting the AGC stuff.

Michio Kaku, the physicist and popular author, put it like this: “Today, your cell phone has more computer power than all of NASA back in 1969, when it placed two astronauts on the moon.” I share your dissatisfaction with this often restated quote. Briefly, the AGC was a 14 bit fixed point computer, plus one parity bit and one sign bit. At the start they thought they might do 256 RAM and 4K ROM, although they ended up with with considerably more, and of course RAM and ROM are just contemporary terms. I have often thought if they had been given a pallet load of Commodore 64 computers, they would have been overjoyed and made it work.

What was the Russian flight computer state of the art at that time? They had developed a one manned lunar lander or Lunar Cabin, and had flown some unmanned lunar missions. We had a considerable lead in digital computers, but what did they have at the time? It would have made for great PR theater for them to claim that with superior Cosmonauts with the right stuff and training to be able fly their lander by the seat of their pants, while US astronauts had to rely on computers. I'm not asking for a muli-part post on the Soviet program, just some comparative perspective.

The navigation and guidance algorithms are less well known, perhaps due their potential use in missiles. Rudolph Kalman's timely paper in the late 50's really put guidance and navigation on firm technical ground. MIT's Draper Lab was tasked with making it all work. The problem was that the Kalman Filter (actually EKF) would have required the AGC to use double precision, making it too slow. Potter was assigned the task, and he developed the first "square root" formulation of the Kalman Filter that enabled the AGC to function in single precision. Potter's formulation is probably not one of the canonical formulations found in modern textbooks, but it was the first and timely development that enabled the Apollo mission. Potter is one of perhaps thousands of Apollo heroes that were never featured in documetar5y films.

I also recently watched the Collins Radio Story on TV. Collins is based in Cedar Rapids Iowa. Collins did all of the Apollo voice and data communication. Until recently I did not realize that they did all of the Apollo ground tracking and navigation support as well. Although the AGC was capable of autonomous navigation, ultimatly, Apollo relied more on ground tracking.
 
Alan15578 said:
First, thanks for posting the AGC stuff.

Michio Kaku, the physicist and popular author, put it like this: “Today, your cell phone has more computer power than all of NASA back in 1969, when it placed two astronauts on the moon.” I share your dissatisfaction with this often restated quote. Briefly, the AGC was a 14 bit fixed point computer, plus one parity bit and one sign bit. At the start they thought they might do 256 RAM and 4K ROM, although they ended up with with considerably more, and of course RAM and ROM are just contemporary terms. I have often thought if they had been given a pallet load of Commodore 64 computers, they would have been overjoyed and made it work.

What was the Russian flight computer state of the art at that time? They had developed a one manned lunar lander or Lunar Cabin, and had flown some unmanned lunar missions. We had a considerable lead in digital computers, but what did they have at the time? It would have made for great PR theater for them to claim that with superior Cosmonauts with the right stuff and training to be able fly their lander by the seat of their pants, while US astronauts had to rely on computers. I'm not asking for a muli-part post on the Soviet program, just some comparative perspective.
Click to expand...
Great idea for a topic. I've researched some of the Soviet PC and mainframe history, but not that.
 
What's cool is that they can use their on-tour functional AGC and plug into it core memory modules from various other partial AGCs at locations they visit and extract the code. Also, a few demo landings using the AGC are recorded with a Lego LM with LEDs to show thrusters firing.

Apollo AGC Part 24: the AGC goes on tour and meets his creators

 
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Mike Stewart's Apollo AGC clone uses this $86 FPGA development board:

https://www.digikey.com/product-detail/en/terasic-inc/P0082/P0082-ND/2625112

451-02.jpg
 
Locals restore Apollo 11 computer, get it to run moon-landing program
July 15, 2019

https://padailypost.com/2019/07/15/...-computer-get-it-to-run-moon-landing-program/

Excerpts:

You might ask, where does one even get an Apollo computer? Of the 57 so-called Block II designs that were produced, some of course went to space, but most were used for development and testing. No. 14, originally used for testing, was found in an electronics scrap warehouse in Texas by collector and former NASA contractor Jimmie Loocke. During the years of the Apollo program, Loocke had worked as a technician testing lunar modules at what is now Johnson Space Center.

In a strange coincidence, Loocke was at a Houston electronics recycler in 1976 and thought he saw some hardware he recognized. He bought two tons of scrapped NASA hardware, and after years of sorting through it all, eventually realized he had an actual Lunar Module Apollo Guidance Computer on his hands. And not only did he have the computer, but it looked to be in such good condition that perhaps it could actually be powered up.
This was a dream come true for Mike Stewart, a 28-year-old flight software engineer described by Verdiell and others as a living encyclopedia of the AGC. When Stewart met Loocke in July of last year, he had been working for five years on gathering comprehensive AGC documentation in order to create his own replica.

Claunch built a replica of the original display and keyboard box, or DSKY, to operate it. Stewart replicated the original MIT/NASA test equipment. Shirriff reverse-engineered the core rope memory module. Verdiell convinced Samtec to help sponsor the project by building and donating about $25,000 worth of replacement connectors so they could hook up the computer to the test equipment. Samtec had to use 1960s documentation to make them. [but as I said earlier, all of the complex documentation I saw them using looked to be beautifully done and accurate, amazing to me for a crash program that developed so much new technology hardware in parallel so rapidly at a time when such documentation wasn't significantly automated - W]

The project had its ups and downs, technically and emotionally. In late May, Loocke agreed to bring the computer to California, planning to get the precious machine its own seat next to him on the flight. At the last minute, however, United made him check it. And then he arrived at SFO — and the computer didn’t.

“We all had a heart attack,” Verdiell said. The computer had ended up on a different flight. After four hours, they finally got it back. After that, it was 15 days of working all day, every day on the project in Verdiell’s basement lab.

Claunch estimated that the four men collectively put in about $30,000 of their own money into the project — not counting their time and expertise. The company PCBWay also printed some circuit boards for them, gratis.

And after they got it working, they just had to know. They simulated the processor overload that had made the Apollo 11 computer famously crash and restart several times during the moon landing. And were amazed by what they saw.

“The computer restarts in a fraction of a second,” said Claunch. “And it resumes where it left off.”

“The first time Mike simulated the fault, we missed it,” said Verdiell. The computer’s ability to recover from such a critical condition likely saved the mission, he said.

The men were stunned at the number of technological innovations that had gone into the computer — and by the extraordinary and long-lasting quality of the components: integrated circuits, capacitors and transistors, power supply and more.

Carl Claunch's blog:

https://rescue1130.blogspot.com/

One entry there:

https://rescue1130.blogspot.com/2019/07/taking-agc-on-tour-and-demonstrating.html

Thursday, July 25, 2019
TRAVEL CHALLENGES

I flow into Houston on Monday the 15th to meet up with the Apollo Guidance Computer and its owners, Jimmie and June. Early the next morning we would fly to Florida and visit Eldon Hall, the chief designer of the AGC, to demonstrate his 'child' operating once again.

The AGC is large and heavy, but old and fragile. We transported it in a large case with foam padding, placing it into a seat next to me for each flight. This is possible if you buy a seat for the item, it weights less than 165 pounds and can be strapped into the seat securely without blocking other passengers from seeing the overhead signs or exiting the aircraft.

Due to the size, it had a business/first class seat to be sure it could be fit into the seat and fastened in place using a seat belt extender. It was in a window seat and I was traveling next to it. Two big challenges existed - getting it through the army of bridge trolls who would insist it has to be checked as baggage, and lifting a 95 pound unwieldy case up over one seat to place it into the window seat.

On each of the three flights involved, I faced a minimum of five challenges and a peak of seven on the last flight. The ticket was made with a name of Incabin Baggage Claunch and the reservation checked carefully with the airline. Checking in to get boarding passes was no problem, but things went downhill fast.

The guards hired to police the lines into TSA for security checks are focused on making passengers check large suitcases. They enforce size rules and are trained for instant and aggressive action. Usually gentle but persistent discussions, flashing of the boarding pass and unwavering commitment to proceed forward would win out.

In Boston, however, we met a gatekeeper who went ballastic and was dialing for security, refusing to listen to me. She began to berate the porter who was wheeling Jimmie in his wheelchair, until he was able to penetrate her fixation and bring her to listen for a minute. Once she truly comprehended that it had a seat, she let us pass.

TSA was a challenge as well. For two of the three flights, the case with the AGC would fit through the X-Ray scanner throat with about 3/8" of clearance, a tight fit but able to move through. In Boston I had to help move it forward on the exit belt where it was jammed. On the flight from Tampa, the X-Ray machine was smaller and the case could not fit at all. It had to be hand examined there.

The case had wheels that were balky and induced major oscillations as I tried to wheel it, a kind of POGO problem. On the bottom, Jimmie had fastened small casters that would move adequately on stone flooring but drag unmercifully on carpet. They also make an ungodly din, sounding like they were scratching up the floor below; Fortunately it was all bark and no bite.

Airports with an airside tram to the gates have their own gate trolls, fighting viciously to keep the case from traveling on the train. Gate agents needed to be carefully approached and shown the ticket before they understood that the case would be pre-boarded and placed in a seat.

I was able, with some help from Mike or June, depending on the flight, to wrestle the case up into its seat and strap it down. In most cases we were safely past the trolls, but on the last flight one of the flight attendants decided that the bag had to be up front next to a bulkhead, not in the last seat as required by the airline and as it flew on the prior flights.

Yet another troll popping up just when I had it strapped in! I was fine if he wanted to force the people in row 1 to move back to 4 so we could put the case there, but his proposed solution was to strap it into row 7 in economy. I reminded him that I had paid for a first class ticket for the bag. While he was focused on that, his partner went back, saw that the case was securely strapped in, and permitted me to sit down next to it for the rest of the flight.

I don't want to give the impression that all these people were uniformly ill-intentioned or obstructionist. The flight crew on the trip to Tampa were delighted to know what they were transporting. The captain came down to see it and admitted to being a big space fan who happened to live near and know Gene Kranz. We took pictures and they were very helpful.

The other crews offered to help me push it up the ramp when deplaning, or to wheel my carryon bag. Even the ones that initially tried to relocate the bag or get it checked softened and were very friendly and helpful by the end of the flight. Too, TSA agents were willing to work with me, helped to lift the case up and down from the luggage cart to their examination table, and even let me take a luggage trolley into the secure area to wheel down to our gate.

The Ultimate Apollo Guidance Computer Talk

 
Dan Lickly "led the Reentry group that developed the Guidance and Control methods for the Apollo Reentry vehicle. Lickly moved on to lead the programming effort for the SA501 and 502 flights. After that he was in charge of a larger group of programmers that did programming for the AGC on the CSM and LEM."

Living behind the Iron Curtain in Hungary and now an extremely wealthy man, Hungarian-born American software architect Charles Simony who built the first versions of the Microsoft Office suite of applications learned English as a child so he could follow whatever he could find about rockets. The first English word he learned was "propellant."

Apollo AGC Part 25: Dan Lickly and Charles Simonyi Reflect on the AGC

 

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