The Four Computers That Flew Humans To The Moon

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Computers were essential to navigating the Apollo spacecraft to the moon, they were some of the first computers that needed to be small and compact, at least by the standards of the computers of the day. Apollo spacecraft carried 4 onboard computers at launch:
Launch Vehicle Digital Computer on the Saturn V
Apollo Guidance Computer on the Command Module
Apollo Guidance Computer on the Lunar Module
Abort Guidance System on the Lunar Module

The best compilation of documentation on the computers that flew on Apollo is Ron Burkey’s research compiled for the Virtual AGC project

Information and transcripts from the Apollo Missions with some explanations are available from the Apollo Flight Journal site:

For even more technical details on the AGC I recommend CuriousMarc’s series on restoring one to working order

  1. ProfessorSkunk

    As a fellow computer programming nerd, I found this video so fascinating. I hope you do more in the future on how rockets and other space vehicles utilize programming to complete their missions.

  2. Erik 567

    Last week I watched my Blu-ray disc, Apollo 11. It had been a while since last viewing. That is one heck of a good documentary. The large format film used was a very wise choice back them.

  3. O. Salviano

    Nice one.

    Make a video about the support computers on the ground next.

  4. alexssandro meneses

    Are those computers the same that Destin showed on @SmarterEveryday?

  5. Damien Drouart

    2:00 , the LVDC ceramic chips were NOT soldered but retained by springy contacts
    Watch FranLab for a teardown of an LVDC board.

  6. steve shoemaker

    Thanks Scott…!

  7. Rob Heyen

    Excellent presentation. Thank You.

  8. kmotch

    If you genuinely believe those computers flew masons to the moon to play golf and drive a go cart I don’t want YOU anywhere near sharp objects or children….

  9. J Waugh

    looking a tad scruffy there scott!

  10. Hendrik Hendrikson

    The more I see from the Apollo missions, the more amazing it is to see they actually made it to the moon and back.

  11. Il Sopravvissuto

    This is amazing

  12. Wallace

    …’memory banks’…

    That’s a term you don’t hear too much these days !

  13. CJ Carter

    Byte and word lengths were a mess. It felt like I was having to adjust to a different system for every architecture. Things really settled down in the early 80s when personal computing was becoming common if not yet ubiquitous. 8-bit bytes and 16-bit words were all the rage. As welcome as that was, I was more relieved when I stopped having to worry about EBCDIC (or Baudot) popping up when we finally settled on ASCII as our de facto character set of choice for most purposes.

  14. moonasha

    I give up after 4 minutes. I’ll always think of chip designers as wizards from another dimension.

  15. mjncad

    They were state of the art back then; but are
    the equivalent of ‘stone knives and bearskins’ by today’s standards.

  16. Sean McDonough

    8:37 – So what would they have done if a failure occurred which both crashed the AGC _and_ wiped out its last-good-state information?

  17. daffidavit

    I already like the video and I haven’t even watched it yet.

  18. Anonym Anonym

    Inb4 moon landing CTers for once.

  19. Anarchy Antz

    What is funny is my ZX Spectrum 48k from 1982 had more processing power than what took men to the moon.

  20. G ary

    Great video explaining how this worked. If they had a cellphone cradle my phone would have been a great backup system. But the phone would have lost signal like driving into a tunnel. Ahh the good ol days, those guys were brilliant using what was available then. Wow

  21. Eric Farrow

    Thanks for summary, I realize how lucky we are to have raspberry pi ,arduino ,amazing what they did with what they had

  22. Greg Ewing

    Next video: Curious Marc and his team turns up at the National Air and Space Museum begging them to let him dump their LVDC core.

  23. John La Duke

    I wonder if the LVDC code is quietly out of reach because it’s still running on some ICBM booster in a silo somewhere…

  24. Dr Scientist Sounds

    Super interesting, thanks Scott!

  25. Infraclear

    @Scott Manley Great video!
    I noticed that your signature sign-off sounded a little grim; am I mistaken? Hope you’re doing well.

  26. Moritz von Schweinitz

    Do we know anything about the soviet’s N1 rocket’s computers?

  27. Mike Kopack

    Awesome video. I love hearing about all the crazy competing design concepts used in computers back then. Today everything is basically Intel or ARM. Back then there were different ideas and concepts and a willingness to explore. Fascinating!!!

  28. kubeek

    7:00 what is twenty forty eight kilohertz?

  29. MrJackHackney

    We don’t hear too much about the LVDC but seeing how reliable the guidance of the Saturns were I’d say it was well built.

  30. Supple ZombieKitten

    I like 18 bit solution. The more bits the longer the word and the better freedom of expression!

  31. Alexander Sannikov

    “rope memory had to be hardwired at the facory”. this actually gives a new old shine to the word “hardwired”

  32. Kevin Norris

    Fascinating how some of those early computers worked…

  33. Michael Brown

    I just finished reading Jimmy Lovell’s book Lost Moon / Apollo 13. Interesting to see the differences and similarities to the movie.

  34. Simon Keeton

    Just incredible detail. Congratulations, 1m subs well deserved. Sincere thanks for a fair few Corona hours well spent.

  35. Mister Itchy

    I love the message at the end!

  36. D. Schmidt

    Thank you Scott for this great video. I am a big fan of the documentation “moon machines” where they also have an episode covering the computers. But not nearly as detailed as you did! Awesome! I wish people nowadays would appreciate much more that nothing on their smartphone would exist without those geniouses who built the first computers!

  37. Jackalovski

    I knwo it’s ovbious but it’s only just dawned on me that all these computers were single use

  38. Jonathan Engwall

    12:09 to 13:00 that is incredible video!

  39. Gov Shill

    When other players call me out for using Mechjeb in KSP, I let them know about the Apollo guidance computers, on the basis that “If it was good enough for Neil Armstrong…” :-)

  40. Lewis Donofrio

    Good stuff as always, thank you for sharing these gems!

  41. Lewis Stockett

    The analog computers don’t get as much attention and credit. Thanks for pointing them out. A deeper dive into them would be interesting.

  42. Patrick's Music

    As somebody with an appreciation for history and electronics- thank you for this video!

  43. Uncle Duncan's Shack

    Those electroluminescent displays were also not trivial pieces of engineering.
    All this was actually not long ago, I am in my late forties and I have had core memory in my grubby hands.
    It used to fill 19 inch racks here on earth.
    And flashing your dongle in public would buy you a ticket to a stay in club fed.

  44. John Paul Lafferty

    Commonality my ass, I’m going to do it my way! It’s amazing with all the vibrations on launch that they didn’t experience any major failures in these computer systems. I believe it was still the fact that there were persons with nerves of steel who took over the landing of Apollo 11 that made for their successful landing on the moon’s surface and the mission! Bad Asses all of them! I would like if you could go into detail of each sensor’s systems interface into the computer systems that provided information into these computers. Would you? I know it would be long and boring for most but there are a bunch of us who would love to understand this complex interface?? Please? Please?

  45. James Dubben

    Thanks for documenting, and explaining all this

  46. Sven Morgenstern

    Speaking solely for myself…dayum! 👍
    I knew about the LVDC from a friend who’s an IBM bigot, didn’t know that the LVDC source was lost to history. I’ve spent some time reading the online copies of the AGC source; from the standpoint of a former code geek that’s just schweet. Well documented, a pleasure to read.
    Thanks for the look back in time… 👍

  47. marlboro9tibike

    Scott Manley 2020: BUTT!

  48. Toon van der Pas

    Fantastic episode again!
    I know about these computers, but you always manage to provide some new insights and information.
    Thanks Scott!

  49. rybářská vrána

    as always your presentations are fascinating. While I knew some of this (having been an avid follower of US space missions as a child) you have once again given us a comprehensive review of all the pertinent elements. appreciate it. makes our shelter in place easier to deal with.

  50. Ari Loggia

    My grandpa worked on the Saturn V instrument unit back when he worked for IBM

  51. Sklawz

    the smarter everyday chann3shows how each ‘circuit’ was wired by hand. effective but tedious

  52. George Miller

    9:24 So if you want to write a virus for the Apollo computer it will be called… the Coronavirus.

  53. Mike Burch

    Another great effort Scott! Again, I learned a lot. Greetings from Arizona.

  54. Joe Duke

    It’s so great computers flew us to the moon, if we had needed rockets… we’d likely have failed.

  55. TheJimtanker

    I’ve got some very good pictures of the LVDC and IU from Huntsville. Interesting machine.

  56. Bob Blum

    There was one more type of computer flown on all manned Apollo missions: the human brain. I think it came in handy.

  57. Benjamin Riggs

    I’d love to hear more about the analog control computer in the Saturn 5.

  58. Pintuxo

    Always very interesting Scott. Thank you. Future computers will take us to the stars (well, to the planets orbiting those stars).

  59. Tiberius Maximus

    love the footage of the docking manuevers near the moon

  60. Alex Landherr

    Linus Tech Tips and SmarterEveryDay each did great videos on these systems and talked to one of the engineers of the LVDC.

  61. Void Astra

    This video drops as I’m playing Deliver Us The Moon, perfect timing !

  62. Reto Kaderli

    Absolutely amazing!
    Seems with today abundant computing power we find much more opportunities to implement bugs … (no, not only Boeing)

  63. SkylersRants

    Your conclusion had me laughing!

  64. felix mendez

    Wow, the same computers that took Stanley Kubrick to Jupiter and beyond

  65. daniel daniel

    9:27 that demn time traveler

  66. Aubrey Freeman

    *Scott makes a video on fuel cells* Me, a Chemical Engineer: “Ah fuel cells! This is awesome!”
    *Scott makes a video on all of the Apollo computers* Also me: “Ah Electric words! How interesting!” *weeps in Chemistry*

  67. Bill Hunter

    I just sent the link for this page to my brother in law. He worked as a programmer on this project.

  68. Ruben Kelevra

    13:16 well, we still can’t agree on that.

    While the word size is either 8, 16, 32 or 64 the instruction sizes still don’t align.

    x86_64 have 8 bit up to ridiculously 120 bit for instructions. While integers might be 8 bit, 16 bit ,32 bit or 64 bit.

    We have two different types of Endianness – one used on ethernet connections, the other one used for basically everything else.

    We have several different architectures, which use 64 bit and 32 bit integers while using either 32, 48 or 64 bit memory addresses. Our filesystems are sometimes 64 bit, while most USB sticks still cant accept more than 4 GB files, since the filesystem is 32 bit.

    So yeah.

  69. Seán O'Nilbud

    I’m just going to slip the shoulder straps of my mankini before I lube up for this one.

  70. Radio Active

    ‘Apollo 13 writes the AGS right out of the movie’….I knew there was a reason I hated that movie😁

  71. vk3dgn

    1201 Alarm – turn it off and on again (quickly)

  72. AFNacapella

    imagine being a solar scientist right now discovering something amazing about ionized plasma around our sun.

  73. Helium Road

    5:20 “If they’d let a hacker near it” I’m picturing the scene from the first Mission Impossible movie where Tom Cruise is hanging from a cable to hack into an air gapped computer in a high security facility inside CIA HQ.

  74. Neo the One

    Imagine going back in time and showing these engineers a 28-core CPU and 1TB SSD.

  75. Anchor Bait

    Does this include Kerbal Space Pegram Running on my parents Dell computer?

  76. zoperxplex

    Notice how the Lunar Landing Module maneuvers in outer space were more akin to the movement of the repair pods in “2001:A Space Odyssey” than the space ships in “Star Wars”. That underscores Stanley Kubrick’s attention to detail.

  77. Dwayne 73

    I think that I just earned my geek degree. I actually understood everything that Scott talked about. It helped that I also got to view the core memory last month at the US Space & Rocket Center.

  78. Stone 930

    Did anyone else picture techpriests when he mentioned superstitious engineers

  79. kokodin

    fly me to the moon and let me play among the stars
    let me see what spring is like On jupiter and mars…

  80. Steven Larratt

    03:55 and i’m lost 🤣

  81. mr santana

    Those were the 13 longest minutes of my life … Scott took every second and literally crammed it with information, this is good stuff!!

  82. Lawrence D’Oliveiro

    9:11 There was one hardware difference between the CM AGC and the LM AGC: in the Command Module, there were two separate DSKYs. The second one was located in the space behind the main control panel, where the navigator stood while taking sightings through the telescope (and also I think where the crew had to go through to get to the docking hatch).

  83. galfisk

    An interesting fact about core memory is that it couldn’t be read without being erased. Reading is done by trying to set the magnetic polarity of a core, and if it then flips from the other polarity, that generates a pulse.
    Edit: here’s a video about it:

  84. Paul Carpenter

    I’ve been a programmer for over 30 years now and at 3:36 Scott just starts with some pillow talk, then just carries on talking dirty to me!

  85. pentagramprime

    Start writing to your elected representatives.
    Let’s get Scott into that museum (so he can extract the code from that guidance computer).

  86. Raphael Brandão

    10:00 I love how those brilliant engineers that made these hardwares still had a dose of superstition

  87. thhseeking

    So much for the silly notion that “alien technology” got us to the Moon :P Aliens would not be navigating tens or hundreds of light-years with computers like that :D We went to the Moon and back with technology that WE developed. Those engineers and programmers were amazing. No bloatware on those machines :P

  88. Dieter MacPherson

    Let’s get CuriousMarc access to LVDC!!

  89. Kevin Bendall

    Oh, yeah. This takes me back to my Mk. 152 Univac Fire Control Computer in the Navy. 16 bit Simplex, and 32 bit Duplex words. Core memory. Huge power supplies. Chips? What are those fancy new thingy’s? Machine code programming. Grace Hopper and her Micro-secant.

  90. Paul Gracey

    I was in the U.S. Navy in the time frame than these computers were being designed, and was aboard the first of the Navy’s ships to be equipped with solid state computers, the Naval Tactical Data System (NTDS). Like the four different Apollo computers you describe, the several components of the earliest NTDS all used different types of logic, different word structures and and even different logic voltages. As usual at that time the choice was up to the manufacturer with only the intercommunications between devices dictated by the Navy team in charge of the system. There were some strangely named gates used and both positive and negative logic employed. As a technician working with the whole system as installed, it was sometimes a real challenge to follow a chain of commands that were not acting correctly on the display consoles. As with the early PC’s reboots were a common necessity. We had two main computers for redundancy, though there were a few single points of failure in the system. Punched paper tape could pile up on the computer room floor trying to troubleshoot. The craziest comment I heard from one of the industrial designers who came aboard to see how this, essentially prototype, system was working, was when he was shown the reverse writing on plexiglass plotting boards that would have to be done manually when the computers were not working. “No, No! he said. Our system is supposed to replace all that!”
    Thanks for the comprehensive overview.

  91. Suzuran Majere

    Unfortunately, NASM’s LVDC was never loaded with code; I was in contact with them regarding dumping it many years ago and they were open to the idea, but when we did further research to determine what may be on it, we found it was only used for testing.

  92. Upcycle Electronics

    -“If they’d let a hacker anywhere near the thing”-
    *If they take their historical preservation responsibility seriously.*
    Code is not some throw away element of the past. It is highly refined prose that hundreds of people spent thousands of hours refining. It deserves just as much attention as the hardware if not more. I suck at it, but still… I can appreciate it.

  93. Alessandro Bianchi

    Basically the apollo program took less computing power than a recreation in kerbal space program

  94. Mike Stewart

    One of my favorite facts about the AGS is that they implemented their read-only memory by omitting the Y addressing wire through the cores holding 0. This made it so that during writeback, these cores were guaranteed to not flip. However, it did mean that a loss of power could leave you with your hard-wired cores reading the wrong thing. To correct this, the first thing the software does when it boots up is “prime” the hardwired cores by writing to every single location.

  95. Peter Anderson

    Instead of calling it the Back Up Guidance System they should have called it the Back Up Guidance and Orientation Unit Technology, or BUGOUT.

  96. 5Andysalive

    +3 massive IBM 360 mainframe computers on the ground (rtcc) doing the heavy work. Which are almost always completely ignored (especially in silly comparisations of “computing power of a Apollo mission).
    A modern smartphone is stilll much better. But things like “a digital clock is better” are just bullshit.
    Not to mention 3 rather good biological computers on board. And a LOT more on the ground and pre-mission.

    Also some people find it absolutely incomprehensible that you can do serious math with pen and paper or a slideruler… Sir Isaac does not approve.

  97. Alpha Adhito

    Now days you only need one “computer” to do all the task. Its called MechJeb

  98. PsychoLucario

    The AGS was like the can of spam in the back of the pantry, you think you’re never going to need it until the world ends THEN botulism.

  99. 7cle

    Scott, you rock star, you rocket star. You rock and never gimbal lock.

    Cheers man.

  100. technicalfool

    “Notably, the first code flown on an Apollo spacecraft was called…”


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