Apollo Guidance Computer Part 27: Recovering the Lost Apollo 10 LM Software

Mike Stewart was able to recover the previously lost Apollo 10 LM software, as flown (also known as Luminary 69 Rev 2). He shows us how he did it, which, fair warning, is a pretty technical hack. And contrary to (yet another) internet myth, the flown software would have been perfectly capable of landing Apollo 10 on the Moon.
T-Shirt, Hoodie, Sticker and Mug with the "It Lands We Checked" logo:
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The scan of the Luminary 69 listing available here:
archive.org/details/luminary6...
The recovered source code is here:
github.com/virtualagc/virtual...
Video of Niklas landing Apollo 10 with the recovered code in NASSP:
• Project Apollo NASSP 8...
Full list of recovered Apollo software and compilers:
github.com/virtualagc/virtualagc
Summary of all revisions of Luminary from Ron Buckley's Virtual AGC Website:
www.ibiblio.org/apollo/Lumina...
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Contact info: kzbin.infoa...

[@gwyllymsuter4551]

Mike is the nerdiest nerd in the Nerdom of Nerdistan. Yes, that is a compliment!

[@thiesenf]

All nerd the nerdism!!!

[@gwyllymsuter4551]

Watching this gave me a giant nerdgasm. Couldn't stop nerdurbating over the nedography

[@broderhjalmar]

The official high-nerd-priest.

[@gwyllymsuter4551]

@@broderhjalmar can't disagree. This boy is enormously clever. Such comnerdment to the agc

[@alm3333]

And I thought I was a nerd. I tip my pocket protector in his general direction.

[@Hans-gb4mv]

- Did you read any good books lately? - Yeah, I picked up a copy of Luminary 69, some easy midnight reading

[@Tedd755]

I'm blown away by the incredible feats of digital archaeology by Mike, aided immensly - no doubt - by excellent documentation produced and kept by NASA. Congratulations Mike, fantastic story. And thanks Marc, for documenting this! PS: It almost sounds like it would've been easier to go get Snoopy. Almost. :)

[@donmoore7785]

It is good to know that NASA saved *something*.

[@MNMtm]

I am actually shocked by the terrible archiving of NASA. Luckily there stille are modern geniuses who are able tot reconstruct the original software with the fragments of code NASA didn't throw in /dev/null.

[@manw3bttcks]

The problem isn't necessarily NASA, they give a contract to subcontractor X but don't stipulate a requirement that these types of records are kept. So contractor X might generate a binary dump of their code and load it to the lunar module and it flies and you have a successful mission. Does their lack of a source dump of the code now mean they failed their contract? Well, id say that the government should have required saving the code as an explicit requirement but I'd also suggest saving these kinds of historical records should be an assumed requirement. This is landing on the moon for God's sake.

[@KallePihlajasaari]

@@manw3bttcks You have a valid point there, it turns out going to the moon IS hard.

[@kargaroc386]

Imagine going to get Snoopy. I'm pretty sure that would be the most complex deep space robotic mission ever conceived, just because it would need to do *so many things* with lots of unknowns, and if anything is impossible then that ends the mission. It would need to be launched (this is the easy part lmao) it would need the fuel and capability (this is where the orbital mechanics wizards come in) to launch itself on an intercept course with Snoopy, which I'm not even sure we know where it is with that amount of precision it would need to wait in deep space it would need to actually intercept snoopy it would need to match any rotation that it has it would need to capture it (the apollo docking ring was disabled at the end of the mission so it would probably need to grapple it), it would need to somehow get into the cabin, probably using a cutting tool it would need to extract the AGC (super complicated robotics) it would need to *open up the AGC and extract the rope memory module* it would need to then plug the cartridge into its own computer with an adapter it would then finally need to transmit the data it reads back to earth. Provided the data is correct, its mission would then be over. SO yeah thats a lot of time and effort to extract a program that we already have the vast majority of.

[@chemicaldexter]

I just hope that Mike´s work is one time recognized by NASA and/or Universities/Museums/Public

[@JohnDoe-yj5ng]

Are you going to tell Thomas Stafford? He's still alive, i'm sure he would like to hear this!

[@joeltyler3427]

He's still around..

[@tiny11231]

Can you make a documentary on Mike Stewart, I need to go down this rabbit hole of his education and knowledge of vintage NASA hardware and software!

[@swebigmac100]

Agree. A true genius

[@UpcycleElectronics]

Just a straight loosely edited or even raw unedited: "Here's your elixir of choice, have a seat around the fire, and tell us your story. (pay no mind to this fluffy mic, tripods and a couple of action cameras.)" I'd watch that upload for everyone in Marc's circle of friends, including Marc. There must be a wealth of stories from Bell Labs and elsewhere. I would love to hear some of the less formal accounts and industry observations too. -Jake

[@RobSchofield]

A brilliant idea. Come on Mike, pull up a chair with a cold beer, and tell all...

[@z_polarcat]

Well mike is actually over 100 years old

[@wizard-pirate]

@@z_polarcat He's actually a space vampire

[@rbergen]

A well-functioning human brain and unforgiving mathematical checksums: a golden combination. Truly enjoyable to watch them in action!

[@John_L]

Excellent detective work Mike, very well done. And thanks Marc for documenting the methodology and not dumbing it down. There are enough of us around that can really appreciate what is going on. It is very unusual these days to come across someone like Mike who is both an accomplished software engineer AND a top notch hardware engineer but we have seen both facets in this fascinating series. Not many young guys that can make sense of assembler code either, come to that. These skill sets were a lot more common back in the 1960s!

[@AndrewDeme]

John L yeah I was going to type something similar and then saw your comment, yep am sure there are a bunch of people that are happily following this. Very talented and fun to watch...

[@nobytes2]

Software Engineer here in the modern era lol no assembly, I'm just blown away by Mike hardware and software knowledge. Also his resilience to find lost important history is just astonishing.

[@drCox12]

Somehow a subscription to this channel feels like a privilege.

[@TheRealColBosch]

I'm still half-convinced Mike is some sort of wizard.

[@jlwilliams]

That's why the in-program comment (see previous video) says “OFF TO SEE THE WIZARD...”. Don Eyles just KNEW Mike would come along sooner or later! (Maybe they are both time travelers from the same future...?)

[@phuzz00]

I'm pretty sure he works for SpaceX as his day job, so he's definitely a rocket scientist.

[@TheRealColBosch]

@@phuzz00 He does, so he's a rocket wizard.

[@Gerard1971]

Mike is a genius who is undoubtedly also doing amazing work at SpaceX. I would like to point out one thing.. that the difference in checksum value is small does not necessarily mean that there is little difference in the binary code, as shown by the first modification of a value, that actually made the difference larger, and then after the second change the checksum matched.

[@joachim2464]

The talent on display here is on a different level.

[@JuneNafziger]

Wow, This is amazing work. Always impressed by Mike's knowledge and skill.

[@Ojisan642]

Paper memos are the 1960s version of github.

[@Vaslovag]

Ojisan642 I wonder if our github repos survive the next 50 years.

[@benjaminsmith3625]

Git is based on checksums too, so it's very close!

[@daviddouard9294]

@@Vaslovag We, at Software Heritage, are working so they do (softwareheritage.org)

[@windowsxseven]

@@daviddouard9294 Maybe you shouldn't.

[@clonkex]

@@windowsxseven What a strange thing to say.

[@AdrianChallinor]

Mike Stewart is a god amongst mortal programmers. As a programmer from the 70's - I kneel in awe.

[@konsul2006]

An honor to be allowed to see this. Thank you so much!

[@MikeCochrane]

That's impressive reverse/forward engineering :-)

[@tsobf242]

I was thinking through the beginning of the video that it'd be nice if he had a checksum to verify it. Made me happy when he showed the whole areay of checksums! great work

[@antoninbesse795]

One of the best CuriousMarc episodes ever. Just made my day. What spark of genius has touched these guys?

[@roberthayes6329]

Also makes me think how thoughtless NASA was or still is in "loosing" important things. For without NASA's huge mistakes in knowing what's an important document and what's dumpster material we would not have this Awesome example of what a brilliant mind can achieve.

[@darrinpearce9780]

This whole project is freaking awesome. I would love to spend a day chatting to these guys!!

[@danvincent2600]

I ain’t gotta clue what they all talking about. If I did and could relate hardware to software I’m sure I could make a good video

[@lwilton]

Well I gotta admit I'm impressed. That is some darn good sleuthing and diagnosis on Mike's part. Probably also a small bit of luck in getting it to compile that easily, but even if the two pad words had ended up somewhere else I'm betting Mike would have figured that out in a day or so. Good work!

[@Sharklops]

This is beyond incredible. It's a special thing to witness the intersection of such intelligence and passion.

[@gfilion]

Brilliant detective work by Mike!

[@bennock1017]

Abso fab. what can one say, A real joy to watch and as one who watched the 11 landing live as a 17 year old these videos have been fascinating. Thank you all from the bottom of my heart.

[@CuriousMarc]

Nice collection of military radios you have!

[@tristshapez]

Thank you Marc for leaving this relatively unedited, that was fascinating to watch. Mike's skills never fail to impress.

[@PaulTomblin]

How many other old timers watching Mike work are reminded of the Story of Mel? Good to see him using vim and make.

[@johnjohnstone2870]

This is just awesome. I grew up in the 60s with Mercury / Gemini / Apollo and was in IT for all my working life. This channel brings it all together, thanks guys.

[@ben94cobra]

just when I thought I couldn't be more impressed by Mike Stewart. What a legend.

[@ifitsrusteditsmine]

We need to create create a new word for the nerdiness level of Mike. This guy is a gem

[@JBFromOZ]

Out of this world...

[@zyeborm]

The new measurement of nerditry is in Mikes. Myself I'm about 50 millimikes give or take. Strangely enough Mike is a 1.2 on the Mike scale

[@cdl0]

"Retrobright" instead of "Retrobrite" (c.f. The 8-Bit Guy). ;-)

[@JBFromOZ]

zyeborm logarithmic scale too?

[@Digital-Dan]

Mike is entitled to the Platinum version of the Peach-Pit-Carving Merit Badge. I may have earned a tin one a time or two . . .

[@SilverHaze5X]

When Yt's recommendations works beyond expectations, you end up in here and witness some digital magic.

[@timcurran7841]

Thanks again Marc and Mike. This is the best channel on KZbin for me! And yes I would buy the Luminary 69 Lands T Shirt.

[@CStuartHardwick]

This was fabulous. One small point though. I wondered while watching whether there was something about the checksums in this code that was fundamentally different from my understanding. Hugh Blair-Smith told me no, saying he found the logic employed here baseless: "Since the calculation of those checksums was done by adding whole words and discarding carries. the 46xxx difference in bank 11 does not imply that a greater number of words was changed than in bank 13 where the difference was 00066. What the 00066 does imply is that the differences in bank 13 are probably restricted to address fields (in the low-order bits), and most likely to the 9 bits used to select data from the selected erasable bank. So he got to the right place by not quite the right reasoning path and deserves credit for that. But a change in any single word of the program could produce any difference in the checksum." hugh Blair-Smith. Regardless, a fantastic bit of forensic computer science.

[@mikestewart8928]

Thanks! :) With all due respect, I understand how the checksum calculation works and disagree that my reasoning was "baseless". I'm fully aware that any single word can change the checksum by any amount -- that's literally what the bugger word does. However, the starting point here was that there was a very large change, probably in a single bank, with possibly changed constants in other banks to support it. Moreover, one of the banks (with difference 00066) doesn't have enough free space in it to contain any of the new code. So when faced with differences 46xxx and 00066, which one is *more likely* to have the big change, and which is *more likely* to have the small change? Reconstruction is entirely guesswork, so you have to make assumptions at every step, then test to see if they were correct. So far, in the ten I've done, small differences in banksum have consistently turned out to be small changes in bank contents, even though it's theoretically possible that a bunch of large changes add up to a near zero difference.

[@Sharklops]

This is genius on another level and absolutely fascinating to witness. Thanks so much for sharing with us!

[@jagardina]

I watched the entire thing and wow. The mastery, the skill, and maybe the luck. But mostly skill I think. Great deductions. I understood more than I'd be willing to admit.

[@edgeeffect]

I've just been reading about archaeologists efforts to read and classify the Etruscan language.... then came here to find Mike poring over archaic ancient scrolls.........

[@mnoxman]

After watching the previous edition about the comments in the code I don't feel bad about my comments in code. One of the things I do is I put in the lines # No user serviceable parts below this line # Refer to your Dumont Service Engineer # Verily there be sea monsters. Just after any configurable assumptions and defaults. A (at one place I worked) manager saw that and I was called on the carpet for "Very unprofessional attitude and approach" and was forced to remove it. Thing is... I do it to almost every script I write from scratch. Kind of nice to know that this isn't even 'stand out' in the programming world.

[@soulrobotics]

Man! You have to see mines! Yes! Calling names, bad words, ... since i know the management i did a macro to search and replace them to its hexa representation. For 8 years nobody bother me anymore...

[@TheRealColBosch]

Anyone who doesn't hide some kind of Easter eggs, jokes, and/or rants in their code is a heartless monster.

[@mnoxman]

@@TheRealColBosch while (hell != frozen); do ...

[@mymessylab]

Watching your channel get me the stimulus to go deeper in the earliest computer since a while, but this is absolutely amazing. You have repaired the AGC and now you get in the brain of its programmer(s). Simply genius are all of you. ❤️

[@RobSchofield]

What a brilliant video, and a superb piece of deductive reasoning from an experienced programmer! Another Steely Eyed Missile Man! Honestly, these videos are outstanding. What on earth does Mike do for a day job???

[@kirkmattoon2594]

As he says in an answer above, he works at Capella Space, which builds synthetic aperture radar satellites (and not at SpaceX, as many believe).

[@robertfallows1054]

Unbelievable. Maually transcribing to recreating code. Great work is an understatement. On top of all this you’d think that anything to do with going to the moon would be protected vs reengineering and saving hardware from recycling

[@pipsqueak2009]

You guys are doing a wonderful wonderful thing. Congratulations and Thank you. Please keep going and help preserve as much as possible from Apollo history for future generations. Just fantastic!!

[@PixelSchnitzel]

I've never said this about anybody before, but Mike is a prodigy.

[@dreamtimescape]

wowza. What an amazing journey. From the hand-transcribed code by a team of amazing passionate people, to the memo detective work, and the detailed notes that did survive, enabling a checksum 'proof' of the changes matching what actually was recorded at the time. Very kewl! Thanks for creating all this to capture the quest!

[@Consequator]

This is a great display of detective work, logical thinking, reverse engineering and old school trouble shooting. This whole space series has been a very interesting and entertaining watch.

[@seamusandpat]

Outstanding work Mike. Congratulations.

[@LtData2000]

Kudos to Mike. It's incredible interesting to see his work and get insights into this old software. Keep it up!

[@MVVblog]

The checksum is right, the program is there, no error! Mike did it! But the incredible thing is that I have understood everything!!! This really leave me so impressed! Mike deserve a Nobel Prize for the recovered Apollo 10 LM software! And you deserve a Nobel Prize for all of your video!

[@robertborchert932]

Absolutely brilliant work!

[@neur303]

Thanks for sharing this feat! It is so inspiring to me how persistence and ingenuity can actually pay off! ❤️

[@queuerious]

Wonderful channel! The details and nuances of the Apollo program are never explored in mainstream documentaries or tv shows, etc. They show the herculean engineering to make the rockets and landers, but the software is overlooked. I'd never heard of 'lost' code of Apollo 10, nor the complexities and attention to detail needed in the flown software. This is a wonderful new chapter for me to explore. Thanks for sharing.

[@joelalain]

Mike Stewart is a relentless genius. The hacking / deep understanding this required & reverse engineering of the code is just breathtaking, congrats!

[@epgallinj222]

Incredible work Mike! Thank you for doing this.

[@muddywaters8706]

What an incredible feat, Mike (and his army of scribes). THANK YOU! Now we need vids on all that other lost software!

[@skfalpink123]

When I look at some of the people our society now holds up as heroes, and then I see the work of brilliant engineers like Don Eyles, it almost breaks my heart.

[@donmoore7785]

Frigging awesome! Mike is quite a detective. Love the way the documentation provided the bread crumbs to allow for the recreation.

[@38911bytefree]

Super crazy stuff ... UI didnt understand. But sure Mike did it perfectly, glad this big piece of history is secured, preserved and documented.

[@ForViewingOnly]

This is really pretty amazing. Great video. It makes me want to learn a whole lot more about the AGC.

[@tomgeorge3726]

Well done Mike, logical process but to understand the code and the version changes makes you an Apollo software guru... We all bow before you. Great video series Marc...👍👍👍👍👍👍👍👍

[@Ender.wigginn]

This is really cool! I hated my asm course so much I went on to study physics and pure maths instead 😂 dude is a wizard, I love how quickly he navigates the program structure too, he obviously knows how it all fits together quite intuitively. Thanks for sharing, and thank you Mike for your diligent work and ingenious reconstruction of the snoopy LM code! Your mastery of the historical, computational, archeological, forensic, and linguistic aspects of this project are mind blowing. I wouldn't even know where to start in uncovering 60+ year old internal memos and code samples, let alone how to even begin attempting to revise such that the check sums changed. I'd probably have given up after my first attempts produced more difference than I had to begin with. Great work! Amazing bit of history you've saved

[@daveb4446]

This is absolutely brilliant. Excellent work gentlemen!

[@kudlok1]

That left me speechless. Chapeau bas, Mike! And many thanks to Marc for his fascinating films. Love you, guys!

[@dosgos]

My grandfather did OCR work with that green bar paper at a bank in the 80s. They had pretty good hit rates with very rudimentary equipment and software. I can't remember the details but he said it was somewhat useless as general purpose OCR solution. You might want to look at 80s OCR approaches for future projects.

[@gryff8400]

Worked with cheque scanning equipment in the 80s. The light colour was important, to make for example handwriting pop off the page and background designs disappear. Very very low fail rate.

[@TheFleetz]

Mike is on another planet! What an amazingly talented and intelligent young man......this is fascinating stuff, thanks for sharing.

[@Scrapy-ih7ob]

NASA Needs Send this MAN A JOB INVITE... Very nice commitment to preserving HISTORY and setting the record Straight..

[@rrl4245]

Fascinating. Great work Mike! Great detective work and nice coding... Thanks for all of the excellent work!

[@Toshiro7777]

Just astonishing. Done on a laptop on a wobbly table while standing up. Amazing skills!

[@Culturedropout]

That's really quite amazing work. Having spent my share of time writing and debugging assembly code on the 8080 and Z-80, I'm really enjoying watching your process.

[@mannhansen9337]

I started with machine code on a KIM-1 with 6502.Still in working order.

[@davelister796]

Great video! Thanks for posting it. Amazing work. It was a joy to watch.

[@MrJay8ee]

Anyone who can move around cygwin and vim that quickly is an absolute g unit in my books.

[@edgeeffect]

When I was a lad, vi was the only editor we had.

[@Tedd755]

Cygwin? That's real Linux.

[@cowboyfrankspersonalvideos8869]

Mike would have fit right in with the early genus programmers. He was just born too late. Thanks for your dedication.

[@MrENT18]

Any chance we can get a run of Luminary 69. It Lands, We checked. Merch?

[@bend1483]

Yes!

[@CuriousMarc]

Of course, right here: teespring.com/it-lands-we-checked Not sure why it is not showing in my merch shelf :-(

[@VincentGroenewold]

Man, this is so underrated. The amount of research here is beyond amazing and the skills Mike has are just out of this world. No wonder SpaceX wanted him. ;)

[@mikus4242]

Preserving the technical history of Apollo turns into a code forensic journey of epic proportions!

[@simontay4851]

I don't understand most of what mike is saying. im lost. To say that mike is a genius, would be a huge understatement. i have no words. Im in awe of him.

[@hoofie2002]

Well done Mike - that's an impressive piece of work.

[@Hiphopasaurus]

Mike, your parents need to write a book about exactly what they did. We need more Mike Stewarts in the world.

[@mitchbayersdorfer9381]

This is amazing work. Please warn Mike that the foam in those Pelican cases is not archival: over many years, it not only outgases, but it tends to turn into a sticky petroleum product. I would suggest storing his listings in an acid free archival box.

[@mikestewart8928]

Yep, I know. Those are for safety when travelling.

[@electrofan7180]

A lot of lucky finds here. The puzzle completes. Fantastic work! Mike is a wizard!☻

[@dgretlein]

Hey, it can’t be that tough to get if it’s orbiting the .... turns out, we orbit the Sun! I absolutely what you all have done. One of my cousins, now looking down on us, was the chief meteorologist for NASA on the Gemini and Apollo missions. His son has a DSKY shirt I gave him from your merchandise (as do I). Thank you thank you thank you.

[@Dountman]

I can’t even fathom the wave-lengths this guys brain runs on. It’s incredible.

[@patjackmanesq]

Wow. Wow. Wow. What a lovely way to start a day, watching this. Thanks M&M!

[@JBFromOZ]

This is supremely excellent Mike... well done mate!

[@lasersimonjohnson]

Absolutely amazing work. Well done 😎

[@vidasvv]

Great job guys, what a great video ! TNX 4 the up load !!!

[@djmips]

I spontaneously applauded @20:00

[@CuriousMarc]

I did too. Internally of course, because I had to film ;-)

[@soulrobotics]

In deed, that was the climax..... I am speechless, inspired, extremely happy

[@ewetoo]

What a great service to history this is as well as being prime nerdfood, bravo!

[@nickstubbings]

incredible work as always!

[@terry6131]

It's great to see history being recovered for the future

[@guyh3403]

Wow, I am very impressed by the skills of Mike.

[@rpavlik1]

So impressive. Great work, great sleuthing

[@jonnychooch6624]

outstanding understanding of lm software. true dedication.

[@thisman1906]

Another excellent episode Marc! Bien joué !

[@PeterCut62]

Awesome ! it is a master piece in digital archaeology. Well done

[@ml.2770]

Luminary 69 It lands. I would purchase that shirt if you made it available.

[@CuriousMarc]

Done! teespring.com/stores/curiousmarcs-store

[@gsuberland]

@@CuriousMarc Niiiiccccceeeee.

[@alansmithee183]

I'm sure glad Mike is on our side!

[@77leelg]

Brilliant analysis and problem solving!

[@steve1978ger]

I loled when he said "checksum". Hats off to you Sir.

[@usermacBrian]

This is most impressive! Really. I'm shaking my head.

[@stephanc7192]

Absolutely astonishing! Wow! Genius!

[@alexanderross2786]

amazing work!