How did the Apollo flight computers get men to the moon and back ?

How did the Apollo flight computers get men to the moon and back ?

There is much speculation by some, as to how the flight computer aboard the Apollo missions managed to get men to the moon when it had just a tiny fraction of the computing power of something like a modern smartphone.

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But this is quite misleading as there was not one solitary computer controlling the Apollo craft, there were 4 computers and no fancy touch screens, GUI’s or other things in a typical computer of today to waste resources on.
The first of the 4 computers was the Saturn Launch Vehicle Digital Computer or LVDC, this got the rocket from the launch pad to earth orbit.
Then there was the Apollo Guidance Computer or AGC, this is the one which most people think of. There were in fact, two of them, one in the Command Module to get from the earth orbit to the moon and back again. The second was in the lunar module that would control the landing and then the ascent back to the command module and docking.
The fourth computer was one which was never used on any mission because it would control an emergency abort and ascent should something happen during the descent to the moons surface like the landing computer failing or they ran out of fuel.
The Apollo Guidance Computer wasn’t as dumb as many make it out to be. As time when by in Apollo’s development, the tasks that it was meant to do increased in both number and sophistication, this in turn created ever more issues with the limited resources available .
One of the biggest problems was the limited amount of memory due to the technological limitations of the time, this meant that the programmers had to make use of every single byte available.
The AGC also had a unique operating system. Systems like UNIX, Linex, Windows and Apple iOS are in control and share time out to the programs. In the AGC, the programs controlled how much time they got depending on how important they were. So that in the case of an emergency, the highest priority programs would get most of the time and non-essential operations were dropped to free up resources which became the basis of mission critical system for all manned mission afterwards.
The computer had a performance somewhere around that to that of the first generation of personal computers like the Apple II, commodore 64, ZX Spectrum that would arrive 10 years later in the late 70’s.
It had 2k of RAM and 36k of fixed storage magnetic rope core memory, which was woven by hand and took months to assemble, so any software bugs were literally woven into the system.
A comparison between the Apollo Guidance Computer and say an iPhone 6 is tricky because the AGC was not a general purpose computer. It was built for a very specific task, had a unique operating system and with the 48-year gap in the technologies used, we can only really get very rough estimates.
The Apple iPhone 6 uses the ARM A8 processor which has about 1.6 billion transistors in it, the AGC had just 12,300. The iPhone 6 has 1Gb of RAM, about 488,000 times the AGC and in this one, 128Gb of non-volatile storage or about 3.5 million times the AGC.
As for performance, the iPhone 6 is somewhere between maybe 4 and 30 Million times faster than the AGC depending on what type of calculations are being done and if you include the iPhone’s GPU it would be even more.
So, if you had to fly back to the moon in an Apollo craft and given the choice, would you trust your life to a couple of iPhones in place of the AGC’s?, because you would actually have more computing power in just one of them than the whole of NASA had during all the Apollo missions…….

Title: Adam Are You Free?
Author: P C III
Nightingale sounds from Gerry Gutteridge
License: Creative Commons Attribution 4.0


  1. AtollK on October 6, 2019 at 2:50 pm

    BS as usual…..

  2. Roo63 on October 6, 2019 at 2:51 pm

    NASA, lmao. Shame they didn’t go to the Moon & can only reach Low Earth Orbit, even now.

  3. SnoopyDoo on October 6, 2019 at 2:52 pm

    Same reason why till this day nuclear power plants are not controlled by computers.

  4. Phil Dicks on October 6, 2019 at 2:53 pm

    R.A.H. was once talking with some NASA engineers about the lunar orbit of one of the spaceships in either Rocket Ship Galileo, or The Man Who Sold the Moon. The mentioned how accurate it was to the one used by NASA’s lunar missions (only off by a few degrees), the Engineers we’re then shocked when he told the he used a slide rule to make the calculations because back in 1946-1948 there were only about 2 or three computers, and since he was a civilian didn’t have access to them, so he used the old fashioned way to make the calculations.

  5. GregGore on October 6, 2019 at 2:54 pm

    Ok curious droid, explain in detail how they managed to broadcast live TV from the moon back to earth, with the power they had available. Go on then.

  6. Nobilangelo Ceramalus on October 6, 2019 at 3:01 pm

    Take that, ignorant hoax-accolytes. But they never want facts to get in the way of their insane fantasies.

  7. D D on October 6, 2019 at 3:05 pm

    First, try putting punch-cards, punch-card readers and magnetic storage tapes into context in 1969. The mind boggles what computers the Apollo craft must have had on board unless of course the craft were remotely controlled in real time by 40 ton mainframe calculators in Houston. Imagine real time, no delay, full duplex wireless communication with Richard Nixon in the White House from 250,000 mls away. And then dream of microprocessors and the stone age, command line, DOS-like, operating systems that were in an embryonic stage in the 70s and 80s. Mind you, they did have batch files. lol

  8. Abel Arredondo on October 6, 2019 at 3:05 pm

    Thank you bro for the vid

  9. dread true on October 6, 2019 at 3:06 pm

    I don’t trust my Mobile to (potentially) enter at home. Even less to drive my car. I will be crazy if I trusted my mobile to go to the moon.
    Mobiles are good for Apps and writing comments in YouTube.
    Hackers are everywhere

  10. adam x feitan on October 6, 2019 at 3:07 pm

    all nasa videos ,why their face like an actor of th movie’s..not a ….

  11. Lucio Maria on October 6, 2019 at 3:07 pm

    Sure. They went to another planet and back 50 years ago with a Commodore 64. Landing on another planet is sci-fi today.

  12. Joakim Siljelind on October 6, 2019 at 3:09 pm

    Since that computer was powerfull enough to calculate positions and movements of objects in 3 dimensions in real time it would have been poosible to build a few thosound of them to computer animate the moonlanding instead. I wounder if that also would have costed 40 bilion usd? Thank God that Nixon fellow was an honest President and never would have thought about stealing tax dollars like that.

  13. Mike W on October 6, 2019 at 3:09 pm

    They didn’t, it’s fake.

    Once you use low tech to go to the moon once it explodes and you cant go back to the moon ever again…

  14. Eme Ce on October 6, 2019 at 3:10 pm

    Podrías haber hablado de la programadora mujer que hizo posible la jerarquía de programas y la desaceleración de los innecesarios en momentos críticos. Seguís aportando a la invisibilización de la mujer en las ciencias.

  15. rear view on October 6, 2019 at 3:12 pm

    It is the same flight computer used on the Boeing 737 Max !!

  16. DJdefcon4 on October 6, 2019 at 3:12 pm

    If you think they put a man on the moon………..

  17. David Rapalyea on October 6, 2019 at 3:16 pm

    Back in the early 1980’s I used my parts bin 8088 (1st generation?) PC and a single 360 floppy to surf the internet. It would display the entire front page of the New York Times in less then two seconds. However, the title was ASCI text. Eventually the links went from this [NEW YORK TIMES] [EDITORIALS] to this [LINK]. It was a serious impediment to actual information retrieval for a long time.

    I used a file transfer program called CrossTalk to dial up a Unix internet computer. Both CrossTalk and my Personal
    Word Perfect word processor fit on a single 360 floppy and would load into a full sized 1 megabyte RAM card on start up and everything was fast after that. I used a daisy wheel printer at 13 characters per second which was slower then dot matrix printers but had laser printer resolution of course.

  18. Ronald Ramos on October 6, 2019 at 3:20 pm

    The Apollo Abort Guidance System *was* actually used, by the way. It was tested on Apollo 9, accidentally activated on Apollo 10, used during lunar ascent gimbal lock on Apollo 11, and used for most of the return trip of Apollo 13 (including several engine burns).

  19. rrando99 on October 6, 2019 at 3:22 pm

    No two-minute waste of time getting to the point. Thank you for knowing how to present a video, most don’t know how to do it.

  20. Avijit Avi on October 6, 2019 at 3:23 pm

    Thanks for letting us know the informations, Varys.

  21. archivestereo on October 6, 2019 at 3:23 pm

    This is brilliant. It does need to be put in context. As anyone who worked with dos based computers recalls, we used to be able to do a lot more when resources were devoted to the program instead of the interface. My no hard drive 512k ram one 720 floppy Toshiba T1000 did some great productivity software stuff without the burden of running a GUI

  22. Daniel Mogiano on October 6, 2019 at 3:23 pm

    They didn’t you idiot it was a hoax

  23. macieksoft on October 6, 2019 at 3:23 pm

    AGS was actually used during missions. IIRC it was used during Apollo 13. IIRC it was also used during gimbal lock on one mission.
    AGC was actually a GPC.

  24. Amanda Ferguson on October 6, 2019 at 3:23 pm

    Good informative presentation.

  25. David Robert on October 6, 2019 at 3:24 pm


  26. V.S on October 6, 2019 at 3:24 pm

    Rockets cannot fly if there is no air. Period.

  27. Rebel Without Applause on October 6, 2019 at 3:25 pm

    Ok, one of my friends just explained this to me in less than a minute..
    Or, as he put it, in "my money.." He basically said, with the computing power they had at their disposal to get to the moon, it would take approximately 3 days to download a tit and around 2 months for a low res, 5 minute jazz flick.. His eloquent descriptive terminology, however crude, has enlightened me to just how bloody lucky they were to get there and back..! Hats off to them, and especially to the ground crew who are often the unsung heroes in these endeavours.

  28. Roshan Doug on October 6, 2019 at 3:25 pm

    What utter rubbish! It really is the case that if you keep repeating fictionalised stories and nonsense people will eventually start believing. No one will doubt whatever set of ridiculous facts you present.

  29. Dra Dikketrip on October 6, 2019 at 3:27 pm

    Imagine taking off from the moon.

    Bij hand control. No computer timing.

    And you have to time it to something that is rotating around the moon..

    And you have to connect to it.. fly to wards it. Not ram it.
    So you can fly back to earth.

    Your moonlander is not an airplane. Refuel midair is Nice, but connect your moonlander on something in moon-orbit?!

    Well, you now know the moonlanding is fake.

  30. tihzho on October 6, 2019 at 3:29 pm

    Hmm, why "iPhone" and not just "mobile phone"? Was it important to the story to use a brand instead of a generic term?
    /end rant

  31. John Augsburger on October 6, 2019 at 3:29 pm


  32. Dan Walker on October 6, 2019 at 3:30 pm

    Another great film! And some interesting comments below it as well. The way alot of modern software seems to work suggests its size is way out of proportion to what it actually accomplishes. Take the huge operating systems of today. I cannot think they operate efficiently. I believe much "modern" code is very reliant on "legacy" foundations that no-one working today fully understands, hence all the bugs and back-doors. Today’s generation largely have no idea what can be achieved with carefully designed job-specific assembly or similar optimized code. At least that is how it seems to me…

  33. Yogan surian Naik on October 6, 2019 at 3:31 pm

    bollocks! they never went past low orbit. they cant get past the van allen belts. not with a 10cm thick aluminium hull

  34. Puffster on October 6, 2019 at 3:33 pm

    A Commodore 64 was complete trash back in the 80s. That’ s many years later after the moon landing. I just can’t believe it, sorry

  35. Venkat Babu on October 6, 2019 at 3:35 pm

    Speed vortex lines. Empty space is a uniform speed vortex line. And earth is a 11km speed vortex curvature. What is 11km. Diameter of earth is 10km extra 1km. So anything less than 10000 km/sec gets trapped in suns gravity space and reaches sun.

  36. Adam on October 6, 2019 at 3:35 pm

    iPhone 6 is equipped with 128GB, not 128Gb of memory ;P

  37. kronik bass808 on October 6, 2019 at 3:35 pm

    We have never been to the moon!

  38. Cyba IT on October 6, 2019 at 3:38 pm

    Very interesting & informative. Thank you good sir 😉

  39. Jaap Soorsma on October 6, 2019 at 3:38 pm

    I have been taught that these computers had the computing power of a calculator and not a smart phone

  40. Jeff Ewell on October 6, 2019 at 3:38 pm

    Best channel on YouTube for education in space!! Thank you sir!! Well done!!!

  41. BADGUY 1 on October 6, 2019 at 3:38 pm

    The "Executive" routine prioritized every "task" it was responsible to complete. Usually, it could get through all of the tasks assigned to it…but on Apollo 11, during the final approach phase of the landing…the Rendezvous radar inputs began swamping the AGC’s computational time. It turned out there was an electrical phase problem with the two A/D converters tasked with reading azimuth and elevation of the radar. The two CDU’s wound up being supplied with power at different phases. This made the information coming into the AGC incorrect. The AGC kept trying to drive the Rendezvous Radar to it’s proper setting to acquire the Command Module…but was constantly being fed incorrect feed back info from the Radar. Luckily the Rendezvous Radar information was of a lower priority than solving the landing equations and while the DSKY gave a quite upsetting "Malfunction Code"…the codes soon passed and after Neil Armstrong, took command of a portion of the landing responsibility, the "MC’s" ceased occurring…and the landing was successful.

  42. R EE on October 6, 2019 at 3:39 pm

    an i6 ???? why would you use that old crap ??? 😀

  43. Rebel Without Applause on October 6, 2019 at 3:39 pm

    "Houston we have a problem..
    -but on the plus side, their are single horny Russian women in my area looking to hook up.."

  44. David Rodriguez on October 6, 2019 at 3:42 pm


  45. lee williams on October 6, 2019 at 3:44 pm

    Everyone had rotary phones and black and white TVs. I forgot they did have VCR technology.

  46. evkapoc on October 6, 2019 at 3:45 pm

    I dont believe that this calculator had enough capabilities to controll the flight in real time.

  47. Matt Bowen on October 6, 2019 at 3:46 pm

    The thing about computers people don’t realize is that the more components a computer has, the less robust it is to software errors and software has to be made more complex to work with the system

  48. Gabriele Simionato on October 6, 2019 at 3:47 pm

    Those poor Kerbals. How much pain they have gone through.

  49. Diane Hansen on October 6, 2019 at 3:48 pm

    A suggestion – do a video on aircraft computers, particularly those in vehicles like the F35.

  50. Roger Mouton on October 6, 2019 at 3:48 pm

    this is a particularly fascinating area of the Apollo program for me. The sheer ingeniousness of how they designed and built the computers to enable craft to travel to and land on the moon. In a way, they had to be smarter than today’s system designers and developers, because of the extremely limited computing power available.