The Real Story Behind the Apollo 11 Computer Error | WSJ

Perhaps the most dramatic moment of Apollo 11's mission to the moon was when the Eagle began its final descent to the lunar surface and the Apollo Guidance Computer became overloaded. Few were more nervous than the young computer programmer who had written the code for the landing. On the Apollo 11's 50th anniversary, WSJ sat down with programmer Don Eyles.
Photo: Alexander Hotz/WSJ
#WSJ #Apollo #MoonLanding

[@scabbage]

As a developer, I can't imagine the type of stress when you are put in a spot to debug code live, and the outcome of that directly impacts people's lives.

[@jennifermyers66]

I watched him have a nervous breakdown...couldn't eat sleep talk walk as a child it was horrendous seeing my father like that and my mother left him with us 4 kids as I was opening a can of white potatoes to eat remembering NOT TO USE THE STOVE ...THE irony of it all is we got the microwave NOW SO I DONT HAVE TO TOUCH THE STOVE I MISS MY DAD

[@rylandhunstad2341]

And in low level/assembly language, as well

[@gregorymalchuk272]

@@jennifermyers66 Was this guy your father?

[@jennifermyers66]

@@gregorymalchuk272 LUCKY LUCIANO NAME CHANGE John DeCatur Myers....he was the one that did the whole MOON LANDING LIE I SEEN THE MAN THAT DIDNT EXPLODE AND COOK IN THE SHUTTLE

[@snooks5607]

@@jennifermyers66 are.. are you ok?

[@glenwoodriverresidentsgrou136]

Just prior to the Apollo 11 launch the simulation team realized that they had never simulated approach to landing computer failures in training. Accordingly, they ran a few simulated failures with the ground control team and the back up crew. One of the failures they ran was a 1201/1202 alarm. During the simulation the ground crew mistakenly called for an abort. The simulation team explained that an abort was not required under those conditions. The ground controllers then went through all the possible error codes and noted what should be done for each code. They had that handwritten set of notes available to them during the Apollo 11 approach. When the problem occurred for real during the landing of Apollo 11 it was news to the flight crew, because the backup crew was used in the simulation. The ground controllers, however, had seen it before. If you listen carefully to the ground control loop during the actual landing of Apollo 11 you will hear one of the controllers say “that’s just like what we had”. He was referring to the alarms they had previously seen in the simulation. They knew exactly what to do: allow the crew land. The 1201/1202 alarm was caused by the computer being overloaded by the rendesvous radar which was not required for a landing. But Buzz Aldrin, who had a PhD and orbital mechanics and rendezvous, thought it would be best to leave the rendezvous radar on in case they had to abort. He reasoned that the computer would have a head start for the abort rendezvous with the command module. The checklist, however, specifically required the rendezvous radar to be off during landing to prevent this exact situation from occurring. In the documentary movie “In the Shadow of the Moon” Buzz Aldrin admits to this mistake.

[@badguy1481]

I (and several others) did the interpretation of the Guidance Computer software "listing" (shown in the video) and generated the "flow diagrams" for instruction of the flight controllers at the Manned Space Craft Center. When I heard the astronauts say "1201/1202" I thought "Oh my god...they can't continue! They MUST abort the descent!". Thank God I WASN'T the decision maker at that moment.

[@davidc7765]

Im glad you filled in this commonly overlooked information that the error was covered in ground simulation. I will add a little bit more that Gene Kranz wrote in his book "Failure Is Not an Option". Traditionally for the final simulation before a launch, the crew was given a "softball" with the expectation that they would have little difficulty knocking it out of the park. Someone suggested to the simulation manager that these computer alarms should be inserted to actually challenge the crew. I believe it may have been Don Eyles that made the suggestion to include these errors in the simulation. So Yes there was a test simulation of the error. It was in the final simulation before launch. The simulation ended with an aborted landing. Apollo 11 came that close to failing on the first landing attempt.

[@travelinman70]

This is a very important bit of information that was left out of the video. This wasn't a "new" experience that had not been seen before. They had rehearsed and determined what the impact was for all error codes. It was a planned failure that had a defined procedure in place.

[@kentbetts]

@@travelinman70 Well, it was kind of new anyway. It had drawn attention during a simulation a a few days before the landing. It was not an old and familiar error.

[@thewiirocks]

@@travelinman70 There was a lot of information left out of the video. This was basically, "there was a 1201/1202 error, they landed anyway, and BTW here's a programmer for the Apollo computer". This could have been a lot more interesting.

[@MohitSharma-hy9st]

From never have written a single line of code ever and interviewing for insurance jobs at 23 in 1966 to going ahead and programming the computers of Apollo 11 in just 3yrs at 26 in 1969, man this guy is a genius.

[@toulasantha]

May be he copied the code from Google 😂😂😂😂

[@silo18]

Maybe we would all be geniuses if given a similar opportunity

[@xheralt]

Coding was an exceptionally rare profession in those days, when single discrete transistors (or exceedingly simple TTL chips) were state of the art!

[@psfanboy79]

@@silo18 no

[@vagtsal]

that was the boomers world

[@markyounger1240]

I was always impressed by Armstrong at that critical moment being so calm. People playing him in movies usually do a poor job because they want to make him hyper and near panic for dramtic effect. I never understood that because we had actual recordings of exactly how he was. Calm as steel.

[@blockaderunner]

ok boomer

[@airplanes42]

He says in his authorized biography he wasn't out of time or options. A test pilot aborts when he runs out of one or the other or both.

[@RMLOTRJDCMClaL]

In a book about him that I've read (By Leon Wagener, called One Giant Leap: Neil Armstrong's Stellar American Journey) said that he "...possessed the suprahuman ability to face the maw (mouth) of death with steely calm." It baffles me too, I think I would instantly freak out and pee my pants.

[@RMLOTRJDCMClaL]

@Lua 50anos You have to, you're going to be faced with a ton of danger some time or another. Especially test pilots. That's why I could never do that job.

[@davidcarruthers4198]

@@airplanes42 k

[@ratgreen]

I'm amazed they hired someone who didnt code. The good old days where employers would teach you up, instead of treating you like a disposable item.

[@yalezero]

Well, he wasn't some random schmuck off the street. He had a Mathematics degree. The first Computer Science departments in U.S. colleges weren't even formed until the 1960s. It's amazing what these pioneers accomplished in such a short span of time.

[@Hiraaad]

The number of people who knew how to code in the whole country were probably in double digits back then. Are you seriously comparing that time to right now where a 10 year old can learn how to code in just a few weeks in the comfort of his own home?!!

[@larcomj]

although......... there's probably more to the story than that. You can only go so deep in 7 minutes.

[@n057828]

Late 80s I was 17 and started to work on mainframes! IBM techs shipped in from USA dressed in suits 80s! No one landed on moon yet

[@bryanw9840]

ratgreen: nowadays both employers and employees treat each other as disposable items. There is little loyalty and commitment going in either direction.

[@stefanosbek]

Software engineering interviews: 60s: - Can you code? - No -...Good you're hired! 2019: - Do you know Javascript, C/C++, C#, HTML, CSS, NodeJS, .NET, Angular, JQuery and React? - Yes - We'll get back to you!

[@rocketpie3300]

What about python 3??

[@Renxsis]

@@rocketpie3300 that's why they'll get back to him :D

[@ryanmarshall8925]

Two weeks later you receive a letter in the mail, "thank you for your interest, the company have ultimately decided to go in a different direction and we'll not be needing your services" aka "we outsourced bye"

[@vonSoest]

I used to know Basic and Cobol.

[@sidh1603]

@@Renxsis lol

[@DigitalicaEG]

This guy is like a cross between Matt Damon and Philip Seymour Hoffman

[@scabbage]

Lol, spot on!

[@DigitalicaEG]

@@VLADIMIR007ISH thanks babe 😘

[@flotreizzz8197]

With a bit of Elton John

and a northern pike

[@michaelesposito2629]

Lol I thought it was going to be a movie coming out, staring Matt Damon.

[@ljpish]

As a programmer from 74 to 04, watching him pour over the program listing brings back great memories. A great job for this 23yr old back then.

[@MrSteamDragon]

Indeed......’84-‘95. IBM S/370 assembler... the degree of complexity of the programs were measured by how high the listings were 🤣

[@Warpedsmac]

....:Pour"...like coffee?

[@ronhenry2025]

Was bummed he didn't get the insurance job, strolled into the MIT instrumentation lab and was cold hired with no experience. I want that America back.

[@m3chan1zr]

Ron Henry exactly. I don’t think an opportunity like that would be available today. At least not at all in my experience.

[@timazbill7746]

We need a new frontier.

[@williamburgos2963]

Then VOTE for TRUMP and tell your friends to do the same. Make America Great Again Keep America Great

[@kysersose3924]

@@williamburgos2963 VOTE for TRUMP and then go tell your friends how they can also "Fvck Over America....Again". God I hate Trump/Russian Trolls.

[@beardedsawyer6322]

You want that america back? Or maybe turn yourself into what he was.

[@HighSchoolNotes]

He politely didn't mention the "human error" was Buzz Aldrin. Aldrin later admitted leaving the tracking radar on. He was scared they may not be able to find Mike Collins after they left the moon, so at the last minute, he decided to leave the radar unit on, instead of follow procedure. He didn't know the computer didn't have the capacity to track the moon and Collins at the same time. Amazing that Aldrin did this... If they had aborted the mission because of the alarms, you would have to speculate that Aldrin would have never flown again. Come to think about it, he didn't.

[@thinkabout288]

great info thanks

[@dahawk8574]

Andrew, I don't consider this video to be "polite". This is the Wall Street Journal. An otherwise reputable news agency. The title advertises that they're going to deliver "The Real Story", and then they inject this blatant lie into their story. As you've accurately reported, there was absolutely nothing "accidental" about this rendezvous radar being left on. It was fully intentional. Schirra's entire crew had a major issue on 7. None of them ever flew again. Borman had an issue on 8. He never flew again. McDivitt had an issue with 9. He got moved to management. Stafford had a major switch error in the LM going around the Moon on 10. Never flew again. [CORRECTION: Never flew another _Moon mission._ ] And I fully agree with your assessment with Buzz's chances for a follow on mission, if he had wanted one. Deke ran a tight ship. And a big reason for why he did that is because he knew very well that if he let anything slide, he'd be hearing about it from Chris Kraft. No, I don't see any way that Buzz would ever have been given another mission. His deviation from the plan that had been thoroughly scrutinized, tested, and trained to, came extremely close to blowing the entire mission. The worst part of what he did, you did not even mention. Not only did he autonomously decide to do this without consulting anyone. He also did not tell anyone what he was doing. Not his commander. Not anyone on the ground. This is a lesson Buzz should have learned as a 2nd Lt in the USAF. You fly the mission as briefed. You do not deviate from the plan just because in the moment it seems like a good thing to do. This is the very reason why you make a plan. So that everyone has time to consider the ramifications of the actions you've planned to do. To use the crass saying made famous by The Right Stuff... Buzz screwed the pooch. He just got lucky that the pooch didn't get pregnant.

[@dahawk8574]

I could have also added the example set by Apollo 12. ALL 3 crewmembers were given Commands after their mission.

[@dahawk8574]

5Andysalive, without any sources? Did you not read what Andrew posted? He stated very clearly what his source was. Buzz himself. And Buzz is the person I learned this info from too.

[@thinkabout288]

@@dahawk8574 but why did he do it then ?

[@woodsie5474]

I had an uncle who without a high school diploma or college degree designed electronic circuits that stymied engineers so much he was hired to design communication and inertial guidance circuits for Mercury, Gemini, and Apollo missions, and also on the SR-71. He was very good, but died from a heart attack about age 55.

[@kishascape]

Or so the CIA tells you

[@CedrinMedia]

@@kishascape That's disrespectful

[@physicalivan]

bs

[@mooiwiele]

Thank you for honoring his memory! What is his name, if I may ask?

[@Pang_Yau]

Was his name Nikola Tesla?

[@Ihyabond009]

Android: has like 300 MB of free space Play Store: error 1202, not enough memory

[@davidappell3105]

My first PC had an 80 MB hard drive.

[@JanR1995]

Memory isn't equal to storage. It is pretty different.

[@jerkins2470]

@@JanR1995 Knowledge isn't equal to understanding. It would go over your head

[@3dr14ng4]

@@JanR1995 He's not wrong technically. Storage is a part of computer's memory heirarchy.

[@rty1955]

@@davidappell3105 my first computer had 16k and paper tape

[@Dennis-tf2cs]

I received a 1202 error yesterday... after taking a closer look, I realized that I was 2 min late for lunch :)

[@L8nitedave]

So you were then go for lunch

[@braeeee_]

This joke is quite frankly tragic

[@Dennis-tf2cs]

Yes it was a "Go" for lunch👍👍

[@cnccarving]

@@Dennis-tf2cs --. --- / .-.. ..- -. -.-. .... :-)

[@Elastane]

@@L8nitedave underrated comment hahahahaha

[@nikwalker570]

Today, if you want to initiate an emergency call, you have to wait for the Ad to finish.

[@puiiroyte5882]

Hahahaha

[@chuckthebull]

I luled at this one

[@RaquelFoster]

How does Margaret Hamilton not even get a mention? She wrote a lot of that, she was officially the director of all 350 programmers, most reports sound like she was the only one concerned with QA, and she was the one who blew the whistle on the fact that flipping the wrong switch could crash the computer - which she discovered after she let her daughter play with the simulator and her daughter promptly crashed it. Nobody listened to her until Jim Lovell flipped the wrong switch on Apollo 8. They should make a prequel to Apollo 13 called Apollo 8: The Other Time Jim Lovell Almost Died in Space. In the case of Apollo 11 Aldrin flipped the wrong switch because a bad checklist told him to flip the wrong switch. The error code the computer gave was a warning meaning “the computer is overloaded and is prioritizing important stuff so you’re not going to die.” I think she’s been correcting people that it wasn’t the software the broke it was the software that saved them ever since a letter to the editor of some geeky magazine defending her software in 1971.

[@tangolima4148]

even till today this men’s world doesn’t give the credits to the right person. Shameful.

[@ben_car_8115]

I thought the exact same. I was hoping the entire time that they would at least say her name but not a single mention. Literally she is the reason it didn’t fail.

[@elitecoder955]

Or maybe her contribution wasn't much

[@elitecoder955]

@@billcowie Sure sure, but what was her age when she actually made it? Are you stupdi to compare someone who is starting off to someone who was literally at her end? Also she was given the medal on behalf of her husband, who she assisted lol Now back to your hole!

[@lgarcia67]

This does not mentions Margaret Hamilton who was the one who came up with the idea of asynchronously running the code despite of the error. She came up with that concept for fail safe which to this day is used in programming.

[@ben_car_8115]

This really frustrated me as well

[@manuelimboden1582]

Yes, and also that a lot of the fundamental work regarding GNC and soft-landing on the moon has been done by the flight dynamics lab at JPL in the 50s and 60s.

[@sirleinarihcaw7324]

@@ben_car_8115 You and me both

[@sirleinarihcaw7324]

@@ben_car_8115 sounds like the male chauvinistic society that is so prejudicial against women. I'd really appreciate if WSJ did a documentary on Margaret Hamilton.

[@LindaRistevski]

Agreed. Her ingenuity is all but dismissed here.

[@rafflesmaos]

Meanwhile, I'm complaining at work about my horrific python code running too slowly when I have a million times more memory and some absurd amount more processing power to work with. Major kudos to Mr. Eyles for his amazing programming accomplishment and contribution to advancement of humankind.

[@whorton4]

Get an old 8 bit system and program on it for a while. . .Especially one with 4K of memory. Efficiency Grasshopper, Efficiency.

[@jchoward6451]

@@whorton4 I'm not a developer but i was in comp sci in the early days of the IBM pc and i remember our prof pounding the table to save memory, save clock steps. If you knew you'd be dividing by 2, shift right one bit instead of a DIV: much faster that way. This is a fabulous topic, lots of info in the comments too!

[@zenkuru_na]

You see there's your problem, python isn't memory efficient.

[@Visitor2Earth]

One correction: Buzz has publicly admitted that he left the rendevous radar ON while the landing was taking place. That was in direct opposition to procedure. Buzz said that he wanted the rendevous radar ON in case they had to abort the landing. The computer was thus receiving TWO radar inputs, not just the landing radar. THAT is why it went into an error state.

[@badguy1481]

Please check the referenced technical discussion give above by Gary Rudd. Evidently, the check list did NOT prohibit the rendezvous radar from being left on...or turned on. In fact it may have been in the procedures. The PROBLEM: The frequency and phase of the power to the two CDU's, tasked to read the azimuth and elevation angles, were out of phase when the switch was turned on. So they were providing wrong information to the Guidance computer. The Guidance Computer kept interrupting its normal calculations during the final approach.... to process those bogus inputs from the rendezvous radar antenna. It was an electrical power problem that caused the problem...NOT Buzz turning on the Rendezvous Radar Switch.

[@MaxHeadroom4014]

See my reply above - I agree that the program should have been able to handle NORMAL data from both sources at the same time.

[@TrackTruth]

first you would have to believe that anyone landed on the MOON, the real one that is not just a simulation. Buzz didnt handle it well, the lie that is.

[@emmikhei]

Not true. The rendezvous radar was supposed and on and on SLEW according to the introductions. "Last minute" change on the flight plan, probably communicated poorly. The crew did what it had been trained to do.

[@kepler240]

@@TrackTruth you're not very intelligent, are you? Do your homework before you speak. Just because you've got tricked by watching some tv show doesn't mean you have spread your ignorance. Use your own brain and dont rely on others to do it for you.

[@ironroad18]

I didn't know a middle-aged Matt Damon use to work for NASA in the 1960s.

[@adam3839]

That's not Matt Damon. It's the MIT janitor that Robin Williams mentored.

[@axa.axa.]

Middle-aged? That guy looks 70

[@scottl5000]

proves time travel

[@kylezmcgee455]

I was thinking the same lol

[@philwright2480]

*used*

[@bonitaramsingh]

State of art 36k memory on the Comp doing the most complex effort of that time! Thankx for the info. It's both humbling and imbues appreciation for all the hard work people did back than- laying the foundation stones, and then, the stepping stones for others to improve things later. Our lander just crashed on the moon 12 days ago with TB in memory and multifold of advances.

[@chuxmix65]

I had the honor of meeting Mr. Eyles several times in the nineties. Very nice guy. It was only after meeting him a few times that someone told me he "worked on Apollo". He never brought it up. He's got a book out called "Sunburst and Luminary: An Apollo Memoir".

[@badguy1481]

Those were the names, I believe, for the various programs customed designed for each mission. I remember one such program's name that somehow stuck with me: "Sundance".

[@pascalxavier3367]

He never answered me when I told him I had found plenty of errors in their stuff.

[@quaxenleaf]

Thanks very much for mentioning the book! I’m ordering it now...

[@antronargaiv3283]

"Sunburst and Luminary" is well worth reading. This was his first job out of college. The rest of us should be so lucky!

[@cadenza3210]

He explains in that book that the actual overload comes from a possible phase error between two power supplies on the LM. Depending on how they power up, the supplies MIGHT be in phase and might NOT. If NOT in phase and both radars are on, THEN interrupts are generated every power cycles (400x per second) which overloaded the computer. The problem was not just that Aldrin had bother radars on at once, but which power supply he had selected. (The switch had two ON positions.)

[@jggallow01]

The scarcity of memory space forced programmers to be optimally efficient. As they said at the very end, their programming prowess is much more refined than today. Bravo to these great thinkers. USA!

[@miguelcastaneda7236]

Dunc Wilson hmm case in point .. pi is no loger 3.14...they now round off to 3.15..can see trouble coming ahead remember we used to have to go to sixth figure

[@badguy1481]

The problem: Today, with "big fat memories" subroutines like "Average two numbers" or "Round off to the nearest 10th", etc, etc, etc. can be just added to ANY program, willy nilly, with no concern for running out of memory. In the Apollo software there was no room to have MULTIPLE "Average two numbers" or "Round off to the nearest 10th" subroutines. It could only have ONE! So..any program that needed to use one of those subroutines had to wait in line, based on its priority, before it could access that single subroutine. It's like having a car mechanic shop, with priorities on each car, and only ONE wrench, that HAD to be used on each car, available in the shop.

[@LeftfootofOrion]

13 Minutes to the Moon Podcast did a very good break down of this error and the follow on error. A team and the controllers put together a go buy for every alarm that the computer would say and had a go no-go plan for each. It's really impressive how quick the decision was made, and how a simple error made it happen in the first place.

[@kpd3308]

Programming in those days was an incredibly detail-oriented endeavor, and required extensive knowledge in the fundamental workings of the system. Paring the code down to its absolute minimum to minimize memory requirements and optimize speed was quite a challenge. Brilliant!

[@honkhonk8009]

But in a way, the code must be very simple. No bloat whatsoever.

[@kpd3308]

@@honkhonk8009 I agree - making things complicated is easy. Making things simple is difficult.

[@megamind6000]

He is also one of the unsung heroes of mankind's greatest space mission till date. 🖖✌️

[@GH-oi2jf]

Advocate of Free Open World - I would not use the word “hero.” He did not put himself at risk to help someone in need. That’s the definitionof a hero.

[@sidharthcs2110]

One of the greatest

[@ronjose51]

GH1618 that’s your definition. My definition of Hero is the person who invented Air Condition

[@peanutwiggin7259]

Greatest HOAX of Mankind,,,,

[@peanutwiggin7259]

@john smith Sorry I dont speak that,

[@jakubwidlarz]

This man deserves an autobiography deal!

[@demef758]

Because of what, a hundred lines of code? Please!

[@malcolmbacchus421]

He has one. 'Sunburst and Luminary' by Don Eyles published by Fort Point Press. 978-0-9863859-0-2

[@Porkcylinder]

Chapter 12 done some more coding today,had pizza for lunch 😐

[@malcolmbacchus421]

Trucker Not read his book then, obviously. It doesn't have chapter numbers, talks about a lot more than merely diarising coding, and doesn't - as far as I recall - mention pizzas at all. As well as explain much of what went on, it is a memoir, though. If you want a book which is solely about the nuts and bolts of how the AGC worked,mi can recommend 'The Apollo Guidance computer" by Frank O'Brien. In fact, it is interesting reading the two side by side,

[@Porkcylinder]

Malcolm Bacchus chapter 13 done some more coding today BUT also smoked some pot and went surfing 🏄‍♀️ might watch the grateful dead later. Then pizza.

[@giovannibaietti2384]

When I worked, I was a hardware engineer. Over the years I have seen the capacity of RAM and ROM memories (Eprom, EEprom, Flash) grow and I have noticed that software engineers who once cared about optimizing lines of code, possibly using the Assembler language, today, with the C language, do not they care more about HW resource saving: it's not a problem anymore and they don't even think about it. However, the consequence is that systems are slower than they could be. On the contrary, the advantage is that programming is easier and faster.

[@ThomasKundera]

Speed of dev, modularity and re-usability are often prioritized over bare code speed. What the use of paying and engineer 2 years to double code speed while just sitting still will provides you with a 2x faster replacement chip in that same time? There are of course limits to that reasoning, but I'll let you on an example: In the 90's a guy thought that rewriting the whole X11stack in x86 assembly code would certainly improve speed by a lot. He spend years on it. In today times, with x86_64 machines and GPU what the use of that work? Nothing. And a final note: I would likely count by my fingers the number of people able to write faster assembly code on any modern CPU than a decent compiler: with the tens of extended vector instructions, pipe-lining and branching predictions, tons of new registers, cache levels and such, but for a few people (who are either designing such chips or writing compilers), most of us would write way worse code.

[@billmcgahey1926]

the real story requires mention of margaret hamilton, this guy's boss, who inspired the code that gave mission controllers the confidence to continue the landing.

[@tylermerlin8320]

You can tell he's put time into providing as much honest thoughtful insight into his answers as possible. Pleasant individual.

[@alfamaize]

I'm glad he mentioned how important this coding concept ended up being- where you have super high priority code that will always run and background that will end up being skipped (which is the end result of not running things that are not important)- I know we were using that same idea for the basic structure of our time sensitive computations to run automotive engines even 40 years after the landing. After that, computers have gotten fast cheap so that good code writing has long gone. Which is too bad (as others have posted)

[@muzlinkage5929]

No mention of Margaret Hamilton, who wrote the code that saved the mission

[@RideAcrossTheRiver]

Margaret Hamilton wrote code. Apollo 11 was told to ignore the error message.

[@lynnpoint6395]

What is amazing is the youth of many of those engineers. Had we maintained the momentum of the 1960s, we probably wouldn't have landed on Mars by 1980 as many thought we would (getting to Mars is a lot more problematic than we thought in 1969), but we'd probably be there by now, as well as having launched some deep space exploratory vessels as well.

[@iri8032]

Yeah and then the government stopped supporting like they used to back then. Look at all the cool progress we have on tools to fight among ourselves and kill each other woah what a great achievement!

[@msbrownbeast]

Back in the day, programmers made efficient use of the available hardware power, unlike today's bloatware.

[@foxandbarrettshow6916]

I half suspect to see a space x launch go wrong because of a pop up

[@manipunation]

​@@foxandbarrettshow6916 Ever hear of ESA's Ariane 5 rocket malfunction: en.wikipedia.org/wiki/Ariane_5#Notable_launches "Ariane 5's first test flight (Ariane 5 Flight 501) on 4 June 1996 failed, with the rocket self-destructing 37 seconds after launch because of a malfunction in the control software.[33] A data conversion from 64-bit floating point value to 16-bit signed integer value to be stored in a variable representing horizontal bias caused a processor trap (operand error)[34] because the floating point value was too large to be represented by a 16-bit signed integer."

[@jl2594]

@@manipunation our programming professor literally brought this error up in what felt like every lecture. I can see why though, it was a relatively simple and avoidable error but the consequences where devastating.

[@4Gehe2]

These people also had bette access to the hardware and knew more about it. We got so many OS and system combinations nowadays it isn't possible to keep note of all them. It is quite different when you can physically see and touch all the hardware involved.

[@Wilh87]

but but.. i need my node_modules!

[@kallewirsch2263]

If we are talking about "the real story" then the explanation presented in this video is wrong. The "real problem" was a design error in the way the tracking radar communicated with the computer. It did so by sending pulses. Thpose pulses were generated by the radar unit and what should have been done (but wasn't) was to phase synchronize them with the rest of the computer. As a consequence the radar flooded the computer with interrupt requests which took away to many computing cycles such that the computer could not catch up with processing them. This destroyed the carefully adjusted timing of the different tasks which where essential in performing the landing. The "operating system" figured this one out and restarted the system thereby getting rid of those computing requests (which were unnecessary at that time of landing anyway). So the point is not, that Aldrin has turned on the tracking radar. He did so, but if the interface specifications would have included a phase synchonization in the way the radar works, nothing would have happend - no error would have shown up. It was somewhat random how the exact phasing of the radar turned out to be, depending on the exact phase relation when the radar was switched on. This is why this flaw did not show up during testing. Well, one can argue that this problem would not have shown up if Aldrin had not turned on the tracking radar, but this is somewhat misleading. The problem originated in the tracking radar specificatinons itself. When Aldrin turned it on, this just brought the problem to the surface. And THIS is the real story behind the 1201 and 1202 errors (of course in a short form). Don Eyles has written a paper about it, which explains all of that in much more detail. But the way it is presened in this video is a grossly misleading. It was not Aldrins fault ("someone had accidently flipped a switch when it shouldn't have been flipped").

[@johnmilus2889]

Great addition to this discussion! Can you direct us to that paper?

[@kallewirsch2263]

@@johnmilus2889 Sure www.doneyles.com/LM/Tales.html

[@saiello2061]

Why did the landing procedure specify that the radar be turned off during the landing? This implies that NASA were aware of a potential problem with the radar otherwise they would have instructed to leave it on for the reasons that Aldrin was fearful of. If that's the case then it seems to me that two parties were at fault, NASA for not telling the astronauts of the potential problem and Aldrin's for simply not following procedure. Why did NASA not inform the astronauts and why did Aldrin break protocol? Or was it simply the case that NASA were not aware of the radar problem but they decided to include the step of turning it off as a precautionary measure? Either way, the astronauts should have been made aware of the reasons for this decision and Aldrin might have thought twice about not only breaking procedure but negelecting to inform others of what he had done. I'm in no way trying to aportion any blame, just trying to understand what really happened...

[@jameshall1075]

If the sequence was changed to when the radar was activated would it be in phase and be processed by the computer not sending the alarm code? Interesting stuff.

[@waynelast1685]

James Hall don’t understand . When the radar was activated it changed the signals to the computer , that’s it.

[@wendys390]

What a fascinating and illustrative story, I suspect on more levels than it first appears. And it might be a great introduction to any presentation of "the evolution of computing," at least. Many thanks to the uploader.

[@roodborstkalf9664]

In the summer of 1966 they took a random guy aged 21 with a math degree from Boston University, who was rejected a few days earlier by an insurance company, to write major parts of the needed software for the Apollo Project. This sounds rather strange to me. Summer of 1966 is rather late to start software development for the Apollo project. Someone or some group at NASA must have realized in the early sixties that they needed software.

[@magalhacarlos]

On the 1973, at IBM, I used to write programs using 2K of code on a /360 modelo 40.

[@oahuhawaii2141]

In 1977, I programmed a TI-57, which had 50 steps and 8 memory registers. I memorized the key map, as each row/col code represents the function encoded in the program memory. Fun times! Later, I did assembly language for i8080 and Z80 on a CPM system. Loved it.

[@andreika6681]

i did that both of you did in 73 and 77 in 1987 in USSR, we still had punch card input "red" copy of os360 (ЕC-1022) in my university till 1993 ! well, i have to admit, my soviet copy if TI (электроника мк 61) had 102 steps and 15 registers :-)))

[@mig7287]

@@oahuhawaii2141 I loved Z80 assembly. The good old days.

[@jcsahnwaldt]

Punch cards? You were lucky! We had to wire one core after the other with a needle! And when we got home, our Dad would slice us in two with a bread knife.

[@jcsahnwaldt]

kzbin.info/www/bejne/Y3PPmqmarL2FkLc

[@AGTsakumis]

Absolutely fascinating. Thank you!

[@sohailahmed1968]

This guy is greater programmer than anyone exist today Thanks for sharing this great story and introducing this great hero

[@Gmon750]

I can relate to this guy. I graduated college and my first job was writing reports in COBOL and our computer room took up an entire floor of the building, and each 5MB disk drive was the size of a heavy-duty washing machine. My boss, the director took me under his wing and helped me get up to speed in COBOL. Those were the days. He gave me the chance where others would not have. I eventually surpassed my colleagues and moved on to bigger and better things. That one chance gave me the opportunities I have now.

[@ohger1]

SO FREAKING JEALOUS!!!!!!!!!!!!!!!!!!!!!!! Glad his name is finally known for his brilliant efforts.

[@snooks5607]

@john smith yes and bill gates also created Windows 🙄

[@snooks5607]

"Hamilton's team was responsible for developing in-flight software, which included algorithms designed by various senior scientists for the Apollo command module, lunar lander and the subsequent Skylab. Another part of her team designed and developed the systems software." of course she was important but please, have some sense of proportion.

[@snooks5607]

@john smith read your first comment. it's about as ridiculous as claiming one person created Windows, it was an analogy "you turkey".

[@andyfeimsternfei8408]

I remember seeing an interview with Buzz where he says he left the radar on. He wanted to keep track of the command module at all times in case of abort. He took the blame for leaving it on and overloading the computer.

[@suekennedy8917]

No video showing the fake LEM during the fake ascent to the moon so whatever Buzz says is total hearsay and cant be proved. Moon landing was filmed inside the LEM simulator.

[@andyfeimsternfei8408]

@@suekennedy8917 Yes and there's no such thing as global warming too?

[@ct92404]

@@suekennedy8917 Just like I thought...the same few nutcase conspiracy theorists are going to every video about the Apollo missions and posting the same mentally ill blabberings.

[@andyfeimsternfei8408]

@@dr.strangelove5622 Yes, please do! You do realize my snarky reply about global warming was just that?

[@bomblade15]

@ct92404 Right you are about Sue. And note, the only people they reply to are those that praise them. Hit and run trolls.

[@pattycerqua5679]

I've been a computer programmer for 40 years, this guy was a pioneer

[@jimaanders7527]

I was learning to program at that same point in time. Memory was so expensive, even on ground based computers, we had to strain to make the code as compact as possible. We used assembly code (or machine code) because compilers were not efficient at that time. Many years later when I started using "C", the compiler had been developed to be more efficient and it produced programs that were more compact than I could do with a reasonable amount of effort. Now days with cheap memory, the emphasis is on "gee whiz features" and "keen graphics" that use unlimited amounts of memory but the final result is nice. I do like the performance of modern computers.

[@kishascape]

Modern computers 10 years ago maybe. Fad oriented computers today are trash. This type of infantile overindulgence is even slowly stating to infect some Linux distros.

[@CONTACTLIGHTTOMMY]

Hal Laning was the real genius behind-the-scenes. His intuition resulted in a computer able to focus on higher priority tasks. Let there be...Executive Overflow. BRILLIANT work!

[@oahuhawaii2141]

@MisterMac56 : I thought there were 5 computers, 3 from one vendor, and 2 from the other. The primary used a majority logic to decide what to do in case there was a conflict between the computers. The redundancy was added for mission-critical systems, where possible.

[@jimlaning108]

Completely agree!! He was described by his peers at the recent Draper Lab Apollo Celebration as the "most brilliant man in the building". A very humble person. We never heard much about his accomplishments until much later. (And no, I'm not biased!! - Jim Laning, Hal's son)

[@tonycook1624]

@@oahuhawaii2141 That was the redundant computer system used in the Space Shuttle - NOT Apollo

[@jsfbr]

The radar switch that caused the overload resulting in those two error codes coming up was not turned on accidentally, but on purpose, albeit differently from the standard procedure. According to Buzz Aldrin, he turned that radar on as an additional safety precaution, which him mind made sense at the time. But that action had never been planned in advance, so the computer was not ready to handle the additional task normally, hence the error messages.

[@internetguy1260]

This is very inspirational to me. I am a man without fancy education working in a field where most have four and even 8 year degrees and seeing what this guy accomplished off the street is very cool.

[@SANTO971]

Truly amazing story, thank you for making this documentary

[@MrSmithwjosh]

It actually wasn’t the first time they had seen the 1202 alarm. According to Gene Kranz’s autobiography, mission control did in fact know exactly what those codes meant. What’s amazing is how they knew them. During their last practice simulation of the lunar landing, the simulation supervisor intentionally overloaded the computers to trigger the 1202 alarm. No one in MC had ever encountered it before or even knew what it meant and couldn’t figure it out in time before landing. The result? They aborted the mission. So when the 1202 alarm went off during the real mission, they had done their homework. It paid off. Listen to the MC audio during the Apollo 11 landing when the alarm goes off and you’ll hear one of the flight controllers say “its the same one as before.”

[@orbitalair2103]

Yes, the Mission Control Test guys were thorough and devious. They once ran a rope under the floor to a breaker. Controllers were supposed to shift right if the console died.....that was how they killed the console ! a rope.

[@ohger1]

When I got a 1202 code in my truck, it was a cylinder two misfire!

[@mfree80286]

I get code 0420 for catalytic converter inefficiency... potentially, exhausting smoke. And I'm dead serious, you can look up the OBD-II error code base yourself. 420 = smoke. Someone had a little fun with that I'm sure....

[@demef758]

Here's hoping your truck simply rebooted itself and you did not have to abort your trip to the dumps.

[@SandBoxJohn]

AGC 1202 alarm, equivalent to the dreaded Blue Screen Of Death minus the death part.

[@almightyantichrist]

Just dump some Seafoam in there, she'll be fine...

[@hankbridges5055]

Get a Actron CP9680 code tester. It checks live, record, emissions readiness test, oxygen sensor test, transmission codes, ABS, SRS, and MORE! It comes in a black pouch and has a cigarette-lighter cable. It can be updated with a USB cable from EBAY. It is well-lit! Get 4 aaa batteries for under the cover in the rear. It works to 2018 and is updatable.

[@stepheng7586]

Where is Jack Garman in this story? He was the only guy during the mission who knew straight away what those codes were. It was him that saved the mission.

[@jackpatteeuw9244]

In the late 70s/early 80s I worked on some of the very first digital electronic fuel injection systems for automotive engines. Our joke was "Do you have blood pressure ? (Or, "Can you fog this mirror ?") You're hired !" Our first EFI system for a 4 cylinder engine that actually went into production vehicles and meet emission requirements of the day, had 8K bytes of "masked" ROM (the zeros and one were set permanently in memory on the "masked" used to make the silivon die) code and about 300 bytes of RAM !! 6 months later we were at 16K bytes of "masked" ROM code and about 400 bytes of RAM. 2 years later, we were at 32K bytes of EPROM and 2K bytes of RAM.

[@user-po6hn9id1t]

And now the ECU holds 3-4 maps for whatever driving style...

[@gregparrott]

Very nice explanation and perspective - Thanks for posting!

[@525Lines]

I've been hearing how the apollo flight computer code is unreadable, unusable, it's lost anyway, and nothing runs it. Here's the programmer with the green bar printouts and the memory modules. And one of the flight computers was recently restored by the guys at curious marc.

[@milanhorvat6494]

525Lines I saw the series too! They should all meet up!

[@BigDaddy_MRI]

525Lines Curious Mark and the team just used the restored AGC to “Land on the Moon”. What an engineering marvel, not only the restoration, but the fact that they could recover the code and actually simulate a landing on the moon!! An AGC actually running code, 50 years later is amazing.

[@525Lines]

@Tony Wilson Probably the quote of someone who didn't want to be bothered messing with digging up the program or finding working hardware.

[@525Lines]

@Tony Wilson He has a little stack of those memory modules, for crying out loud. That's gold wire. How'd he get away with that?

[@525Lines]

@Tony Wilson Happens all the time. Office dumpsters are ridiculous and awesome.

[@lorenrickey5481]

I found this really interesting. Thanks for posting.

[@andante005]

Who are....these amazing people? No words for it.

[@duncanmckenzie2815]

Fascinating documentary about a fascinating subject. Thank you for this.

[@luciusvorenus9445]

Truly the Wild West of computing, a programmer with no computer training and then working with rope core memory. Amazing.

[@randysmith4331]

@Michael Johnston I love that phrase. “The wild west of computing”. How true.

[@johnpossum556]

@@randysmith4331 When we played "Tank" instead of Pong.

[@badguy1481]

@@randysmith4331 Me too!

[@badguy1481]

@@johnpossum556 It was about 5 years BEFORE Pong!

[@oahuhawaii2141]

This guy is a math major, when few universities had a computer department, and the ones that did would be run by the math department. So, it is only sensible to put these math majors to the task of programming.

[@jackswezy9841]

From what I remember, I thought someone had memorized all the program alarms, and knew that the 1201 and 1202 alarms were just because the computer was overloaded. That they actually were okay with the alarms, not that they were just proceeding without knowing the problem. Pretty sure they knew what it was, and then Houston took over monitoring the Delta H so the computer wouldn’t be overloaded.

[@joevignolor4u949]

Actually, they had a list of all the program alarms written down at mission control. Then when the alarm number came down from the crew the people on the ground quickly went through the list numerically until they found the correct numbered alarm and its associated description. It was a very rudimentary fault detection system in keeping with the times. Modern computer systems do basically the same thing except they automatically look up the text associated to the particular fault and then they just display the fault description on an alpha-numeric display for the user to read it.

[@tangolima4148]

Simpler than that: Mission Control knew the flight guidance was up and running all the time and the ‘go’ was based on that. A shame this clip makes you believe Armstrong took over manually because of that while it was normal ops to do so regardless the alarms.

[@SuperIwatch]

In an interview, Buzz Aldrin said he had accidentally left that radar on. The radar was the acquisition radar to guide them to the capsule after they took off from the surface of the Moon. I always took it from what Buzz said they had used that radar when separating from the capsule and had simply forgotten to turn it off for the landing. The acquisition radar plus the ground radar were simply feeding the computer system too much information.

[@TheJer1963]

How many more times is this going to be said?

[@SuperIwatch]

@@TheJer1963 I don't know. As for me, I recall saying it only once.

[@FunkyMonk6]

@@SuperIwatch yeah well it’s BS. Activating the acquisition radar was standard practice, it was on the checklist. It’s a complete myth that Aldrin made an error.

[@randalltufts3321]

Curious Marc needs to get in touch with this gentleman. Seeing those modules sitting there was amazing. The printout is nice as well. Now that Marc's team has the only working AGC and dsky in existence it would be great if they could collaborate and recover the data from those modules or get a perfect working memory module to use while it's on tour. Even tho the original is repaired it could fail again with no backup. Everyone that has piched in on Marc's project is being credited. This man is responsible for helping in a huge way of putting a man on the moon

[@puncheex2]

In the Mars lander project Viking, I can remember The Book of the lander code - all 32 Kbytes of it. It was about four inches thick, and was produced in about 1974 (for the landings in 1976). By the time of the launch The Book had become so marked up with changes and such that there was fear that something would be accidentally overwritten. It was a major evolution to convert the listing back into source code, re-assemble it and distribute the binary, test it to death and make sure that all old copies were destroyed. In the end, one of the landers actually was ended by just such an overwriting of critical antenna pointing data, fortunately only after three years of totally productive work.

[@randalltufts3321]

@@puncheex2 something so small but done over and over sure can make the original look unrecognizable and unworkable in the end just like that. The printout he has is the last one that went in 11 apparently. That would be interesting to see. Who knows what's in his memory but I think all memory should be dumped and saved for history. If possible.

[@puncheex2]

@@randalltufts3321: At the end of the aforementioned Viking project an entire floor of what was known as the Space Support Building (a 200' x 200' office building at Martin's site in Waterton, CO) was dedicated to the saving of all sorts of support data from the project, mainly on 1/2" data tapes. Every test performed was kept. I can't say what may have happened to it all; last time I was in there was perhaps 5-6 months after the landings in 1976.

[@randalltufts3321]

@@puncheex2 that's amazing. Hearing NASA say that a lot of the tech or software used to go to the moon is "lost" missing or had been discarded like trash was unconscionable. Such an important piece of history when all Americans were galvanized as one was mistreated to say the least. Seeing these gentlemen re-engineering and bringing this back to life was a pure joy to behold.

[@belllarosa]

Love this!👏👏😍 Geeking out on all things Apollo Program...such good stuff!

[@ginghamt.c.5973]

Wonderful to highlight Some of the Very Best Unsung Heroes in the Apollo Pyramid

[@jurajpetrovic5809]

What I am missimg in this video is the fact, that Steve Bales and the backroom guys at MOCR have it figured out even before the mission started. In the simulations before the mission they were given the same type of alarm. When Bales called an abort, the simulation supervisors told him, that he shouldn't have done that. In reaction, Bales and his team, went over all the computer alarms and made a list of those, which called for an abort and those, which didn't. If you hear the audio from mission control during this alarm, You can hear Bales talking "Same type we've had" This refers to the alarms in the sim. So the guys in Mission control were pretty much prepared for this and did a perfect job in preparation and execution of the mission. "Tough and competent" as was the line from Gene Kranz after the Apollo 1 fire.

[@JustinY.]

It's insane to think that the computing power they used was less than the power of a smartphone.

[@Giankpetrov]

Insane is that you believe they land on the moon with 36Kb

[@victornpb]

smartphone?! a gameboy is a power house compared to what they had. They were building individual bits using tiny ferrite cores and wires, the program is literally hard wired using a half mile of wire. They didn't even had leds to make the 7 segment displays.

[@ct92404]

@@Giankpetrov So you're one of those schizoid conspiracy theorists? Well guess what? You don't need that much memory and processing power for a navigation system. It's not like the AGC had to display fancy graphics - all it needed to do is take in data and perform calculations.

[@override7486]

​@@Giankpetrov I bet you have you have no idea how much is 36KB used the way it was implemented in Lunar Lander. Just because you ignore and some facts, disagree with them, and don't even bother understand it, doesn't mean it's not true....

[@coachhannah2403]

Early Atari game systems, WITH GRAPHICS, used 2 kB cards for the ENTIRE freaking GAME. 36 kB is Huge! My Atari 800 maxxed out at 48K.

[@garymazeffa]

Love the interview with the programmer to round out and provide background information for the story. BUT, it is well known and commented on by Aldrin himself that he left the rendezvous switch on because of concerns for a quick exit (so to speak) if the landing needed to abort. Once again, I just find it incredible that a major news outlet either does not do its homework or just out and out lies.

[@michaelclark9762]

Buzz said that, but the flight checklist also said to switch it on.

[@garymazeffa]

@@michaelclark9762 Then a double disservice by the news media; ergo, no mystery...as it was presented.

[@johnsutherland168]

Some decades ago (in 1969) I worked at MIT/IL on the Apollo missions. I started out as a programmer and then ran a small group that assisted other programmers. One of the programmers that I worked with was Don Eyles, a man chartered to develop the lunar landing software. Here is Don's explanation of what went wrong during Apollo 11's lunar landing. The 1201 and 1202 computer alarms had everyone concerned, and Mission Control made the proper decision to continue landing the LEM. Apollo 11 was successful as a mission.

[@johnsutherland168]

BTW, MIT/IL was responsible for the guidance and navigation of the Apollo flights. The DSKY we used as operator input was a first, and it probably helped set design for the numeric keypads used on telephones and computer input devices ever since. The onboard guidance computer (AGC) was quite small, and because no one knew what the space radiation would do to computer memory, all memory was hard wired magnetic core memory. It turns out that the solar radiation and the Van Allen belt radiation problems were not huge, and the human astronauts and the spacecraft hardware seemed to survive quite unmolested by those tiny and worrisome radiation particles.

[@maxsmith695]

Nope

[@johnsutherland168]

@@maxsmith695 - Nope what? You were there? I don't think so.

[@doxtops]

dude learned how to code on the job with no experience and wrote some of the most advanced code to date. incredible

[@albertbrooklyn]

Human ingenuity a true marvel; respect.

[@cowboybob7093]

6:53 Haise, Fullerton, Engle and Truly - Well done Mr. Eyles!

[@litespeed65]

Don came to MIT with a Mathematics degree, so not just some guy off the street. Read about the Apollo 14 abort malfunction where Eyles wrote code while Sheppard and Mitchell were separated in the LM about to enter the PDI phase of the descent. Mitchell manually entered the changes (that would bypass the abort switch) relayed by radio as they appeared out of the Dark side of the Moon (amounting to over 80 keystrokes on the LM computer pad) just in time.

[@bradleycross5987]

Have written assembler code with restrictions but nothing like their restrictions. The validation of the software must have been crazy extensive. The mind boggles how they handled change control.

[@jimbeaux4988]

As a programmer myself, this story is as scary as any horror film. Makes my blood run cold.

[@fidziek]

because it's simply nothing more than that... as someone mentioned above - stack overflow or IRQ overflow... thats it... and users munst have known this error long before they ... well, yeah - what did they really do?

[@planck10-43]

is that because you suspect the missions never happened in the first place?

[@PerfectDanceVideos]

Mr. Eyles is also to be remembered as the programmer who literally saved the Apollo 14 lunar landing mission by crafting manual-entry software workarounds to accommodate an intermittently misfiring ABORT switch.

[@PacoOtis]

Wow! Thanks for the video! The world owes that guy a great many beers!

[@nonelost1]

It’s amazing that Don Eyles, who is responsible for having written most of the computer code for the Apollo 11 LEM landing phase, is not only still alive, but agreed to this interview, to explain what almost caused a disaster for Apollo 11. It was good to hear him say that the code itself was sound, but apparently did not take into account “what if somebody flipped a certain switch that would overload the computer and cause it to reboot at its most critical hour?” It was good for him to have stayed on at MIT to debug the LEM Landing, phase code so that he could write a version 2.0 to that code that would know how to react if that (somebody flips a certain switch that ain’t supposed to be flipped) were to happen again. Whereas had he been fired or quit, a new landing phase code writing committee would have to start from scratch, that would likely increase problems with subsequent Apollo moon landing missions.

[@tvre0]

It actually WAS taken into account. The backup crew did a simulation of it a few days before launch, and that's why it was a surprise to the primary crew; they hadn't simulated it, only the backup crew had.

[@waynelast1685]

Wow that’s the kind of stuff I like to watch. So informative.

[@robertschlesinger1342]

Interesting interview. Amazing that the Apollo flights got to the moon with equipment that only a generation later seems antiquated and almost primitive technology.

[@olasek7972]

Robert Schlesinger electronic part of it may seem antiquated but the bulk, I mean like 98% of the content was pure rocketry - not antiquated by any means even today.

[@robertschlesinger1342]

@@olasek7972 Good point. That's perhaps why people say "It's not rocket science," if a task is not too difficult.

[@olasek7972]

Robert Schlesinger there has only been an incremental advance in “rocket science” in the last 40 years, no huge advances like in computer field.

[@robertschlesinger1342]

@@olasek7972 Thanks for your insight. What about advanced materials or propellants? Any comments on such advances? Surely trivial compared to the advances in computer science. If I may share a true story. Dozens of years ago, there was a brilliant and kind professor (Dr. W. P.) that I knew who had a Ph.D. from MIT in Ceramic Engineering. Some students (not science majors) foolishly ridiculed him behind his back, stating that he got his Ph.D. in ceramics! A sad but true story.

[@olasek7972]

Robert Schlesinger we got new solid rocket motors, some segments, engine rockets can be reused (SpaceX is innovating here), other propellants remain the same, more importantly very little changed in terms of costs to build equivalent rockets.

[@Aramis7]

Great video. I recommend the podcast "13 minutes to the moon" by the BBC, which is a gem. This issue (and the AGC / Apollo Guidance Computer, as well as many personal stories of those involved) are told in detail

[@BrianJuntunen]

And what they omitted is something I learned from another video, the radar was turned on when it wasn't needed but in addition, Buzz was asking the computer to update him on the progress of the lunar landing and that put the computer over the edge so it restarted everything except his inquiry and he figured out after it happened twice that it was he who was causing the code.

[@KOZMOuvBORG]

3:35 more like DOS being loaded into an XT with floppies, runs off the storage, Macs with CDs usually had onboard OS

[@NxDoyle]

I'm Don Eyles, one of 400, 000 Apollo Program legends and I used to look like hippie Matt Damon.

[@howardreubenstein9134]

They had seen 1201s and 1202s in simulation. They had a cheat sheet that told them go on 1201 and go on 1202 during landing. Not that it wan't nerve racking, but they were prepared and were not debugging on the fly!

[@cossakrocker]

There is a rare NASA broadcast where they revealed that in a landing simulation an error code had come up and they had a hard time finding out what to do and they did an abort. They instructed the software team to analyze every error code and get a procedure of exactly what to do for each code if it came up. - That likely saved the mission. Amazing.

[@nzoomed]

I bet this guy could write some amazing C64 Demos!

[@TheSonicfrog]

From what I understand, the overload had nothing to do with Aldrin's setting of the Rendezvous Radar (RR) switch on per the Apollo 11 flight plan. It came from a design fault in not phase locking the Coupling Data Unit (CDU) power supply with the Attitude and Translation Control Assembly (ATCA) power supply. By design, the CDU relied on the phase of ATCA power supply to be in phase with its own to infer the position of the antenna, and they weren't in phase, thus the CDU generated spurious interrupts which overloaded the AGC when the RR was in Auto or Slew mode.

[@mahoneytechnologies657]

Can this be verified, It is always good to know the true reason for things, that is how we learn, learning with true information.

[@TheSonicfrog]

@@mahoneytechnologies657 Curious marc mentioned the phase shift overload when bringing up a PIPA accelerometer for their rejuvenated AGC. Here's another reference: github.com/chrislgarry/Apollo-11/issues/23

[@TheSonicfrog]

@@mahoneytechnologies657 on page 3-66 of the Apollo 11 flight plan it clearly states RR (Rendezvous Radar) ACT & SELF TEST at 99:32 and later on page 3-69 RR ON at 102 something. www.hq.nasa.gov/alsj/a11/a11fltpln_final_reformat.pdf

[@TheSonicfrog]

@@mahoneytechnologies657 also in the the mission report of Apollo 11, entitled "Computer Alarms During Descent, at page 16-13 you find this: "Any difference in phase or amplitude between the two 800-hertz voltages will cause the coupling data unit to recognize a change in shaft or trunnion position, and the coupling data unit will slew (digitally). The "slewing" of the data unit results in the undesirable and continuous transmission of pulses representing incremental angular changes to the computer. The maximum rate for the pulses is 6.4 kpps, and they are processes as counter interrupts. Each pulse received by the computer requires one memory cycle time (11.7 microsecond) to process. If a maximum of 12.8 kpps are received (two radar coupling data units), 15 percent of the computer time will be spent in processing the radar interrupts. The computer normally operates at approximately 90 percent of capacity during peak activity of powered descent.) When the capacity of the computer is exceeded, some repetititvely scheduled routines will not be completed prior the start of the next computation cycle. The computer then generates a software restart and displays an Executive overflow alarm." www.hq.nasa.gov/alsj/a11/A11_PAOMissionReport.html

[@TheSonicfrog]

@@mahoneytechnologies657 Curious Marc also just did a simulated landing on the moon with an FPGA version of the AGC and mentioned the faulty CDU as the cause of the overload. kzbin.info/www/bejne/qJDIc3qJmpqte7M

[@BusyBasaz]

What an amazing story and legacy. From unemployed to coding NASA computers at such a young age. Love that he kept all these old papers and items from his NASA days. Can imagine he has entertained quite a few house guests.

[@TheLarryBrown]

Define "entertainment."

[@ratheeshmy4518]

Moon mission from USA is entertainment..! Best of Hollywood...

[@marspalk7611]

He never written a code yet was a good to help land man on the moo . Just shows what human are capable of and ability to adapt and learn when pressed.

[@JohnDeCarteretElvis]

Actually Mr Eyles was only one of several people who made up the coding team and he wasn'tt the person behind the error coding that saved the Moon Landing, it was Margaret Hamilton. It was at her insistance that additional error coding was implimented and she then also wrote the first asynchronus coding which enabled the on board computer to keep going and not crash due to the overloading. Therefore ensuring that the most vital operations were still carried out and therefore enabled the Moon landing to continue. She worked her way up from a junoir tech to become the Lead and NASA's first software engineer. It was her coding that saved the moon landing and she was honoured by President Obama with the highest civiilian award.

[@drac]

Source ?

[@peppeddu]

Besides the memory constraint, the developers had also a great deal of pressure to do it right. If an error in the code could result in the astronaut dying and crushing the dream of a nation you're gonna do it right no matter what.

[@malcolmbacchus421]

The code was tested to destruction in simulation after simulation before it ever got near a real live Apollo. The first versions were extremely buggy.

[@JettRiver]

The radar wasn't accidentally left on!! Buzz Aldrin publicly admits that he left it on in case he needed to abort and rendezvous with the Command Module.. Something he had never done in the simulator.

[@robevans5222]

The compact, efficient code of the early days of computing is essentially a lost art. At University of Michigan in the very early '70s, classmates and I were writing Fortran code that we delivered to the computing center (IBM 360 mainframe era) on punchcards. In fewer than 200 instructions, we could simulate the hydraulics downstream of a hydroelectric facility's outlets, or simulate the dynamic response of an automobile suspension to specific roadway and vehicular characteristics. Computing power at the time was VERY expensive, and the wait time to have your program batched into the machine could be many hours - so you learned to write efficient code with error-free syntax, as errors cost you both dollars and wait time. I made many trips to the computing center in the middle of the night, as turnaround was usually much quicker then.

[@davefk]

I just find it amazing that there are such people in the world who think this way. They are the ones who have taken us out of the stone age....

[@fidziek]

no, it's NASA which prevents us to reach a real space age

[@profwaggstaff]

I read something written by one of the programmers that the multiple radar signals being processed would not have overloaded the computer if the multiplexer had sync-ed the signals properly. He laid the ultimate blame on the multiplexer for allowing unsynchronized signals to hit the IO processor. I believe the idea was that the IO processor was being interrupted twice as much as expected.

[@jamesedward9306]

Would have been nice if they'd mentioned he had a BS in Mathematics from Boston University when he was hired. So though he didn't have programming experience per se, he definitely had training in logical/mathematical thinking. And he was bright enough to be bored with differential equations in his senior year to drop out, though he would return for his degree. I'm not downplaying his story, it's most definitely inspirational. They were TRUE brilliant creators. No one knew how to write code for what was required. NO ONE. They had to figure it out. He's written his autobiography. You can find it on amazon books. Wound up at MIT purely by chance. It's all incredibly fascinating.

[@Embur12]

Buzz also broke the switch for the engine to lauch the ascent back up to the command module. He jammed a felt tip pen into the switch to complete the circuit and lauch the engine.

[@KevinDavis338]

Computer programmers back then were more badass than today's developers.

[@oahuhawaii2141]

I did assembly language programming. For fun, I even wrote self-modifying code; that crunched a piece of code down to about 25% of its size and run efficiently.

[@badguy1481]

What, to me, was the most DARING portion of the Apollo 11 mission: When the Lunar Module was ready to descend the last few feet to the Lunar Surface, the LEM Guidance and Navigation Computer experienced a VERY severe malfunction. The malfunction code that was displayed to the astronauts indicated the computer was being swamped by the number of inputs coming in. That meant the computer could not accomplish all the computational tasks it had to perform to continue its control of the space craft. VERY DANGEROUS situation and the malfunction occurred only MOMENTS from the final approach and landing. Given that condition the SMART thing to do would have been to abort the landing....hit the "Abort" button.... and ascend back up to the Command Module. But that's NOT what the astronauts did. Neil Armstrong took manual control of the LEM...a VERY "SKETCHY" move...because he had little to no experience flying the vehicle manually. Yet...that's what he did...and as we all know.... landed the LEM safely on the surface of the moon. What a guy! What a pilot! (He SHOULD have been reprimanded for doing what he did...But thank God he DID do...what he did!)

[@malcolmbacchus421]

It wasn't a very serious misfunction. Within 20secs of the alarm call, Jack Garman in the flight dynamic support room had determined it was the same type of alarm they had had in simulation (he even had a table of these alarm codes and what action to take). The response given to Guidance and then the crew was that the mission was still go providing the alarms didn't become continuous. The LGC continued its work but Houston took over monitoring one particular parameter rather than have the computer do it. The guidance programs continued. To do their job perfectly all the way down. Armstrong took over manual control to avoid boulders and this had nothing to do with the alarms: in fact by the time they were they low, the computer was no longer overloaded and the alarms did not, and would not have, continued. As for it being "the last few feet from the ground", the first set of alarms were at 6,500 ft and the second set at 3,000 ft. What it shows, more than anything more was that Mission Control, together with the hundreds of people supporting them, were, through training and planning, on top of that problem and every other one thrown at them.

[@michaelclark9762]

Armstrong had more experience flying the (computerless) LEM simulator than anyone in the Apollo program at the time.

[@badguy1481]

@@michaelclark9762 Well...Flying a simulator is NOT like flying the real thing. And it's still not clear to me whether he was flying the LEM completely "manually" or "manually with computer assist". As I remember he was able to increase or decrease the descent rate, the last few feet, using the button on his hand controller while the computer maintained the attitude of the LEM. I may be wrong..but I thought that's what I heard from the transcript. As I remember there were 3 modes for landing: 1. Complete Computer control. 2. Manual with Computer control. 3. Complete Manual. I believe he was using option 2?

[@michaelclark9762]

@@badguy1481 While it is true that flying a simulator is not the same, in this case the sim was harder, as it was flying in Earth's gravity without the aid of a navigational computer.

[@Laminar-Flow]

Great piece of journalism. Great to hear from that dev himself

[@ChrisBrengel]

Great video! What totally blew my mind was 1) He got his job at M.I.T. having never written any code before! 2) Had he been asked, he would have called for an abort!