Thursday, July 25, 2019

Taking the AGC on a tour and demonstrating Apollo 11 landings


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.


Eldon Hall, who was the lead designer of the AGC at MIT, is retired and living in Naples Florida. Jimmie had promised to show him the AGC working again, which meant a trip to Naples and setting up in Eldon's condo. The place was packed with family and space fans looking to meet Eldon and see the AGC work.

It took us two hours to assemble everything, cable it up and test it out, but finally we were ready to provide a demonstration. We had to move furniture and place his large TV near the table with the AGC in order for Mike to see the screen for the landing in addition to the audience. There was a minor issue with the LEGO LM model such that it couldn't be hooked up in time to show the thruster and engine fire, but the DSKY and everything else was working fine.

Mike flew the mission from about four minutes before Powered Descent Initiation (PDI) where he began the landing from the 50,000 foot orbit altitude by firing the descent stage engine. Mike took us through the process, from Program 63 which braked and lowered our altitude through the approach phase of Program 64 and then the semi-manual landing under Program 66 where he flew past some boulders and craters to reach a desirable spot to land. The landing was a success, to the delight of all.

Eldon had a souvenir core rope module which he allowed us to read and archive using the AGC. Mike has shared this code with the world and begun working on understanding how it relates to earlier and later versions of Apollo software.


We flew up to the NYC area to exhibit at the Cradle of Aviation museum in Garden City, near where Grumman built the Lunar Modules. We had the chance to view a nearly completed LM (LM-13) which would have flown to the moon had not NASA cancelled Apollo 18, 19 and 20 missions. Too, we could see an LM simulator and plenty of Apollo related equipment.

We set up to begin demonstrations at noon, attempting a landing on the moon using the software from the Apollo 11 LM Eagle running on our AGC. It was crowded and hectic, but we had the chance to meet quite a few fans of our restoration, who had read from our blogs and YouTube videos that we would be available today for public viewing.

We didn't have microphones and the space was kind of cramped, set up next to the LM Simulator, but we did our best to run many landings, answer questions and interact with the visitors during the day. Due to a private evening event at the museum, we had to tear down and pack up before five.

We did get the chance to visit the museum archives and see the documents given to them by Grumman - a treasure trove. We hope to be able to digitize some of the more important content in the coming months. One document we spotted would be a great aid in building our own LM simulator. It contained all the data and math equations used to build the simulation. That document was perhaps 5 inches thick.


The following morning, July 19, we drove up to Cambridge Massachusetts to the MIT Museum where we had a chance to examine part of an AGC that they have on display. It contained some core rope modules of the Sundial program, which is the test suite for the Command Module which is analogous to Aurora which tests the LM.

Those modules were read and archived, giving Mike even more disassembly and analysis to distract him from sleep over the coming days. We then set up our equipment that evening for the following days events. Given that setup takes about two hours, it was very helpful to complete it tonight.

It also allowed us to get everything cabled and working, including the LEGO LM model. This model will light LEDs on the RCS quadrants of the model as the AGC commands that the thruster fires. It also lights the descent engine bell and modulates the brightness as the engine is varied from 10% up to nearly 100% thrust by the computer.


We had large crowds, with many lined up outside the room after people had filled in aisles and were sitting on the floor in front of the first row. As a result, we ran as many landing demonstrations as we could. While we didn't keep exact count, I believe it was around 11 during the day.

In a couple of them, things went awry but Mike was able to safely achieve a landing even with some challenging conditions. A consequence of how Mike is delivering the landing radar data from the Orbiter/NASSP simulator into the AGC counter memory locations is that the timing between simulator and AGC can misalign.

Since radar data is altitudes and velocities in three dimensions, sequentially entered into the counter, if the timing is off the computer sees a velocity as an altitude, or vice versa, which throws off its computed position and velocity for the LM. In one case, the computer believed we were 1000 feet higher than we really were.

Mike saw based on the shadow, dust clouds and other features that he was much lower than reported, so he took control by moving to Program 66 where he could ask the AGC to control rate of descent while he controlled horizontal velocity. He hovered, nulled out the horizontal velocity over a likely point and gently lowered us to the surface. In that case we were down to 2% propellant left, tight but still safe.

Many more fans of the restoration and the AGC had heard about this visit from our blogs and YouTube videos, as well as the advertising by the MIT Museum. It was a delight to meet with them and talk even though time was tight as we cycled through landing after landing.

Don Eyles sat in the first row and watched one of the landings, quite a distraction to us. He then graciously offered us access to two of his Core Rope modules in order to archive the data on them. After the end of the daytime museum event, there was a break before the adult-only Moon Shots! party began. We used that to read the ropes (and to eat and rest). The evening event allowed us to run through a couple more landings and interact with the visitors before our day drew to a close.


On our final day, July 21st, we had the great privilege of being invited to the 50th anniversary brunch for the Apollonauts, the MIT staff who designed, built and programmed the AGC and related gear. There were over 100 people there who had worked at the Instrumentation Labs, later Draper Labs, including children and grandchildren.

We did perform one landing for the crowd, after a hurried assembly of our equipment amid the bustle of a large brunch meeting in a big tent at the Newton Marriott. We didn't bother setting up the LEGO LM as it would be too hard to see across the large tent. Something was wrong and the DSKY wasn't working either, but again only the closer tables would have been able to see it anyhow.

We did ask that any of the group who had Core Rope modules consider loaning them to us for archiving and we did get a number of commitments that will keep us busy studying the evolution of Apollo software for quite some time.


That evening, I hauled the AGC for its final flight back to Houston. It went home with Jimmie and June while I slept at an airport hotel for my final flight back home to California. It felt odd to board an aircraft without the AGC although the process of check-in, security and boarding went much, much smoother.


  1. Congratulations on a successful trip. Sounds like all the hard work paid off. Sorry to hear about the 'gate trolls', but you get that with every large organization.

  2. I was able to attend the moon shots demo in Cambridge, very exciting to see the real hardware in action after so many years. Wish there had been more time for questions but I understand how busy it was. I'm glad more core ropes are able to be archived.

  3. I am happy to answer any questions you might have through replies here. With the long lines outside waiting to see a demonstration, we had to have the Q&A section cut very short. I wished we had more time to speak with other technologists and followers of the restoration.

  4. Wow, that is all just marvelous. Congratulations on your tour!