Mike and team came to recover the software from the hand-woven rope memory in my Apollo Guidance Computer (AGC), removed from the Lunar Module in the Smithsonian and reused for the first digital fly-by-wire airplane flights. They just released the video.

NASA never saved a copy of the software from the Apollo program. But the magnetic core memories in the computers retain their program. So, Mike Stewart designed and built a rope reader (photo above), and he is using it to read out the programs in the computers that have been saved. Mike doing more Apollo software recovery than all the museums in the world combined.

My TLDR; American won the space race because of superiority in compute from an early bet on the integrated circuit (IC). The Lunar Module guidance computer was the first IC-based computer, and the first contracting award of the Apollo program in 1962. By 1963, Apollo consumed 60% of global IC production. It was essential for real-time trajectory calculations for rendezvous, an essential capability for our lunar mission plans.

My AGC was so rare and valuable that it was reused in the first digital fly-by-wire (DFBW) test flights, as is common on all jets today (instead of a physical connection with cables and pullies, the pilot’s flight controls go to the computer, and the computer controls everything that makes the plane fly). Rather than build a new computer for this, they reused the Lunar Module computer as well as 60% of the Apollo 14 flight software!

My AGC and related components were removed from LM-2 and put into a custom pallet with liquid nitrogen cooling plates so that it could be lowered into an F-8 supersonic jet behind the cockpit, like R2-D2 in an X-wing fighter.

NASA’s pioneering DFBW program was sponsored by Neil Armstrong in 1972. It worked beautifully, giving better control, efficiency and reliability to flight. After this demo, the space shuttle and eventually all jets shifted to this control method. NASA concluded that the DFBW was “one of the most significant and most successful NASA aeronautical programs since the inception of the agency.”

The analysis of my AGC and it memories revealed that it has components that flew to the moon and back on Apollo 12, and it contains Aurora 88, the first Lunar Module rope ever produced, representing the complete LM AGC test set.

Thank you Mike, Marc and Ken for your incredible techno-archaeology and revivalism!

4 responses to “Reading out the Rope Cores from my LM AGC”

  1. jurvetson Avatar
    jurvetson

    Details on my palate with AGC from LM-2Apollo Guidance Computer (AGC) and Navigation System from the second Lunar Module, LM-2Diagram of the items:My earlier post on its user in DFBWHow the Lunar Module improved flight on Earth ✈️The source code had some interesting comments… as memorialized on the t-shirt of the recovery team…

    Reply
  2. sbove Avatar
    sbove

    Unbelievable efforts to build these early SW/HW systems! True tech pioneering by very large teams of cross disciplinary talent & fantastic leadership. More details on wikipedia [en.wikipedia.org/wiki/Apollo_Guidance_Computer ], but some of the most salient:

    "AGC software was written in AGC assembly language and stored on rope memory. The bulk of the software was on read-only rope memory and thus could not be changed in operation, but some key parts of the software were stored in standard read-write magnetic-core memory and could be overwritten by the astronauts using the DSKY interface, as was done on Apollo 14. "The instruction format used 3 bits for opcode, and 12 bits for address. Block I had 11 instructions: TC, CCS, INDEX, XCH, CS, TS, AD, and MASK (basic), and SU, MP, and DV (extra). The first eight, called basic instructions, were directly accessed by the 3-bit op. code. The final three were denoted as extracode instructions because they were accessed by performing a special type of TC instruction (called EXTEND) immediately before the instruction." "Block I AGC initially had 12 kilowords of fixed memory, but this was later increased to 24 kilowords. Block II had 36 kilowords of fixed memory and 2 kilowords of erasable memory." "A simple real-time operating system designed by J. Halcombe Laning consisting of the ‘Exec’, a batch job-scheduling using cooperative multi-tasking, and an interrupt-driven pre-emptive scheduler called the ‘Waitlist’ which scheduled timer-driven ‘tasks’, controlled the computer. " The AGC had a sophisticated software interpreter, developed by the MIT Instrumentation Laboratory, that implemented a virtual machine with more complex and capable pseudo-instructions than the native AGC. These instructions simplified the navigational programs. Interpreted code, which featured double precision trigonometric, scalar and vector arithmetic (16 and 24-bit), even an MXV (matrix × vector) instruction, could be mixed with native AGC code." " In total, software development on the project comprised 1,400 person-years of effort, with a peak workforce of 350 people(!!!!)" "The design principles developed for the AGC by MIT Instrumentation Laboratory, directed in late 1960s by Charles Draper, became foundational to software engineering—particularly for the design of more reliable systems that relied on asynchronous software, priority scheduling, testing, and human-in-the-loop decision capability. When the design requirements for the AGC were defined, necessary software and programming techniques did not exist so they had to be designed from scratch." "Details of these programs were implemented by a team under the direction of Margaret Hamilton. In 2016, Hamilton received the Presidential Medal of Freedom for her role in creating the flight software." "In 2003, an effort was started by Ron Burkey to recover the source code that powered the AGC and build an emulator able to run it, the VirtualAGC. Part of the large amount of source code rescued as a result of this effort was uploaded by a former NASA intern to GitHub on July 7, 2016, attracting significant media attention. The original Apollo 11 Guidance Computer source code was originally made accessible in 2003 by the Virtual AGC Project and MIT Museum. It was transcribed and digitalized from the original hard-copy source code listings that were made in the ’60s. In mid-2016, former NASA intern Chris Garry uploaded the AGC Source code onto GitHub"
    Here’s the GitHub page from earlier transcribing efforts: github.com/chrislgarry/Apollo-11

    Reply
  3. electromechanic812291 Avatar
    electromechanic812291

    Mike’s knowledge of the AGC must make him the world expert now, especially as those original boffins at MIT slowly leave us

    Reply
  4. Ro-bot-tens Avatar
    Ro-bot-tens

    Nice story! Unbelievable the hardware and software reuse

    Reply

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