Apollo Guidance Computer Part 9: Unboxing my Apollo IRIG Gyroscope

I just scored a genuine Apollo IRIG II gyroscope at the latest RR auction! Let's unbox it, after taking a quick look at more "mundane" military gyros from Ed's collection. In this session we step away from the guidance computer proper and look at its main input sensor, the Inertial Measurement Unit (IMU). I had resigned myself to use a lesser gyro with the Apollo servo electronics Jimmie had donated to the project. Well, no more, now we can use the real thing.
Extra footage credits:
IMU period footage borrowed from the newly released Draper Labs site Hack the Moon: wehackthemoon.com/
Beryllium sphere scenes borrowed from the great Galaxy Quest movie (pray for me to avoid the copyright strike!)
Music by Eon "Ambient Sci Fi Music"
kzbin.info/www/bejne/jofFp3hmha-sqdU
Some relevant links:
Playlist of the restoration series: kzbin.info/aero/PL-_93BVApb59FWrLZfdlisi_x7-Ut_-w7
Block I AGC period documentary: kzbin.info/www/bejne/pJXZnnminJaKo6c
Inertial navigation system documentary: kzbin.info/www/bejne/rXWcaIWJpc6Nm5I
Schematics: www.ibiblio.org/apollo/links.html#AGC_electrical_schematics
and: archive.org/details/agc_handbook_jp2
Mike's AGC backplane viewer: apolloguidance.computer/2003100_071/pins
AGC software repo: github.com/virtualagc/virtualagc
The Ultimate Apollo Guidance Computer Talk: kzbin.info/www/bejne/rqmafZmearh-i7M

[@michaellitscher9456]

My mother was employed as a mathematician at AC Spark Plug (as it was known then) in Oak Creek, Wisconsin back in the 50s-60s and worked on an inertial guidance system for NASA. Her job was to verify the math of the computer's guidance algorithms. She made sure my sister and I never missed a launch, and occasionally kept us home from school so we could watch live NASA broadcasts.

[@trekaddict]

Props for quoting the most under-appreciated and underrated SciFi movie of my childhood.

[@Raptorman0909]

Love the 'Galaxy Quest' reference -- one of those little gems of a movie that simultaneously made fun of and revered the Star Trek series.

[@ethanpoole3443]

I love many of the parody sci-fi shows for much the same reason. There is just something fun and oddly refreshing about the odd movie that does not take itself too seriously and strives to have a good time.

[@ReneSchickbauer]

Couple of years of restoring to go, and then Marc can go to the moon in his new Apollo spacecraft made from spare parts ;-)

[@jeromeprater183]

The main difference between the Block I and Block II Apollo IRIG 25 was the method of electromagnetic suspension. The Block I only suspended the gyro float in the radial direction while the Block II had a dual axial and radial suspension system (Ducosyn) for full non-contact suspension. These instruments were originally developed by MIT labs under Charles Stark Draper in the 1960's for the Polaris Submarine Launched Nuclear Ballistic Missile. MIT modified the design of the gyroscope and the Sperry PIPA Accelerometer for Manned Space Rated Service. This instrument must be must be heated to the exact rated temperature to have any reasonable accuracy. It would need to be gimbaled in two 90 degree axes to be completely isolated from external rotation. Gyro gimbal rotational misalignment was generally kept under one second of arc in the servo loop.

[@electronash]

This is great. :) Not only did I never imagine seeing a full restoration of an original AGC, but I never thought somebody would show a gyro as well. This channel is the geeky gift that keeps giving. lol

[@kevinszabo7035]

In case some folks didn't know why aircraft instruments are powered by air (or vacuum) the reason is for redundancy. In the cockpit, if you lose electrical power your air-powered instruments will still give you enough information to fly the plane. If you lose air power the electrically powered instruments will still function. This was explained to me by a friend who was just getting his ILS certification on his small aircraft.

[@johnopalko5223]

Absolutely correct, Kevin. I'd just like to expand on it a bit. This is in the context of a light general-aviation airplane that uses "steam gauges" instead of a glass panel. Your typical airplane has three gyro instruments: the heading indicator (still called the directional gyro by us old farts), the attitude indicator (nobody calls it an artificial horizon any more), and the turn indicator. Typically, the attitude and heading indicators are vacuum-driven and the turn indicator is electrical. The inclinometer (the little ball at the bottom of the turn indicator) is, basically, a level and isn't powered by anything. Losing the turn indicator, by itself, is usually no big deal; it's considered a secondary instrument and is used mostly to establish and maintain standard-rate (3 degrees per second) turns. Losing your other two gyros, by themselves, can cause things to get interesting. You are now flying what is called "partial panel," also known as "needle, ball, and airspeed." It's perfectly doable but it makes very high demands on the pilot. Declare an emergency and get no-gyro vectors to visual meteorological conditions ASAP! If you lose all three gyros while you're in the soup, well, rest in peace... NB: Before anyone says that you can just use the inclinometer to keep your wings level, no you can't. Gravity is actually the least of the forces acting on that ball. You can't use a glass of water, either, certain KZbin videos notwithstanding.

[@Moraren]

Apollo AGC part 36: Picknick at the Sea of Tranquility

[@rkan2]

Gotta add a couple zeros hehe

[@mikaras]

It so amazing to watch this series. The amount of engineering and attention to detail put into these components show what a big task they accomplished. Everybody working on this project where true heroes and pioneers.

[@kneecaps2000]

Astonishing. Since I started my journey of discovery in 2003 on the AGC the IMU and IRIGs have fascinated me. It was a struggle back then to even find detailed IMU drawings. Here you now share a real IRIG II. Scintillating stuff!! Thank you.

[@TheEPROM9]

It is amazing just how advanced this tech was. The sheer engineering skill that went into developing this stuff.

[@sheep1ewe]

Interesting how similar it (still) is to the V2 gyro. Massive respect to the guys who made those pieces! Thank You for sharing.

[@sheep1ewe]

@@jameshay2076 No, just the basic construction, but i think it first came to practical use in this basic form in the A4 (V2) project if i am not wrong here. At least the core and the cylinder mount of the gyro device look pretty similar, but this one is of course a lot more modern and constructed from more accurate materials and methods they did not had acess to in the early 40s, and V2 did not had that sphere and it also did not had all those devices for stabilising, only for basic axis stabilisation as i remember. The V2 system was connected to a mecanical DC rotorconverter system instead of modern silica chips. (Sorry for my terrible English, it's not my native language...)

[@dr.strangelove5622]

This channel is really *AWESOME!!!* It is the best channel for geeks who are into such things. Just the pure energy you show in your videos makes my day!!

[@FesixGermany]

Gyros are really fascinating, even the pure mechanical ones, hard to believe they are absolutely independent of gravity and would stay in position no matter where you are in the universe.

[@tripwaveofficial]

this is mindblowing to think that my 3-axis camera stabilizer is generations built off this technology!!!

[@ethanpoole3443]

Only in a very vague sense as the gyros and accelerometers in our modern cameras, smartphones, drones, etc. operate on very different principles even they they sense the same events and have no motors or spinning parts whatsoever as their sensing elements - in fact, aside from a possible flexing strain gauge to detect physical deflection, they have no moving parts at all and are amazingly minuscule and power efficient - not to mention silent - compared to traditional mechanical gyros and accelerometers. Our moderns MEMS-based counterparts instead utilize thermal conduction and/or strain gauges with a small cantilevered mass to detect acceleration and/or rotation about an axis.

[@tripwaveofficial]

@@ethanpoole3443 stop it with your logic! :D

[@zerobyte802]

This gyro is an amazing amalgamation of high tech and arcane all at once. Modern instruments of this precision are much smaller and lighter, yet here is a device over 50 years old but sensitive enough to show the Earth’s rotation. It’s easy to forget that humans have been just as intelligent for thousands of years - today we just have the benefit of lots of technology to expand upon.

[@greendryerlint]

And the amazing thing too is that we do it with about an 80-year lifespan. Just imagine the things we could do if we lived a couple of hundred years... oh, and stopped killing each other..

[@justin.campbell]

Nice job finding a REAL Apollo gyroscope! love your vids just subscribed! Thank you for all of this hard work and its because of awesome people like you that these machines still operate. Keep up the good work :)

[@melancholicwaffle]

Upvoted for the use of 'cutie-pie' in reference to a gyroscope

[@PORP65]

Thank you so much for your video series. It is highly interesting to see the beginnings of our highly technical age and how it was done with simple means in a highly complex way. It also explains the function of many of the used parts and answers many of the questions I had. Please continue this work. I will look forward to your next exploit.

[@TheRealColBosch]

I continue to be stunned speechless by this series. Amazing work, gentlemen!

[@macguyver209]

One of the best arguements against the conspiracy that we did not go to the moon is this equipment... Why build such high precision pieces, unless your really going to use them to get from to there and back...

[@ddegn]

Many conspiracy people seem to think their ignorance is some how evidence against the moon landings. They ask how difficult challenges were possibly overcome without really wanting to know the answer.

[@togowack]

@@ddegn The problem is intelligent engineers like in this comment section write off all conspiracy theorists when the truth is the true nature of the missions was hidden and still is although bits and pieces of their explorations are beginning to come out.

[@jackflash6377]

Great videos. Every new video just raises my respect for the people who engineered these devices.

[@adamp9553]

Nothing short of amazing. They really put the best, most reliable tech up there.

[@bobl78]

absolutely fascinating.. even more in context of the 60´s technology...

[@Patrick_B687-3]

The amount of engineering and the short time it was done in, are nothing short of staggering. Great channel btw. Caught it on the algo for some reason but have enjoyed it a lot, even knowing nothing about electronics.

[@michaelcherry8952]

Can't wait for the next episode. I love the detail you go into. These things are so fascinating. It must have been exciting to be a design engineer in those days.

[@Songbirdstress]

Talk about an unboxing vid.....this whole thing is amazing. Goosebumps.

[@riccardoz2953]

Amazing piece of hi technology of that time. so much wonderful devices !!! Great hit guys !

[@LittleWhoreRecords]

Enjoying your Apollo series, amazing stuff.

[@edgeeffect]

Nice "cosmic" music. ............ I'm going to have to watch Galaxy Quest again now!

[@Sharklops]

I had forgotten about that movie until recently. There's a great documentary about it on Amazon Prime I saw not too long ago and I definitely need to watch it again soon myself.

[@alpcns]

Jawdropping stuff - absolutely wonderful. Thank you so much!

[@danielson9579]

Amazing I thought that hardware like this was lost along time ago can't wait until the next video 👍🙂

[@001snapshot]

I find myself very much enjoying your videos. For the last 2 and a half years i have been a Break/Fix laptop desktop and tv field engineer. Much of what i have seen of your content is WAY over my current sphere of knowlege. I do have experience dating back to the timex sinclar 1000. I still have a timex sinclar 1100. Again my knowledge is but a drop in the bucket compared to you and that you various teams. Much enjoyed the entire series on the Alto...Please more on the Apollo AGC. Regards ME

[@evhvariac2]

A great video for understanding gyros. Thanks for this!

[@fragdude]

There is an interesting little ‘documentary’ about Autonetics (I believe the company that made the Apollo IMU hardware - they made the hardware for the early ballistic missiles up to Minuteman III, & were a subsidiary of North American Aviation/Rockwell) & their work on the IMU & gyros/electronics involved. You can find it on KZbin. Interesting tidbit from the video: they were one of the main driving forces for the IC evolution & for a while were consuming *half* of all IC built in the USA.

[@DrTWG]

This is one of the most interesting videos I've seen in a long time - that's a nod to the content and delivery - I watch a lot of factual stuff.

[@P61guy61]

Awesome. Thank you for posting.

[@lowmipsdotcom7383]

great video series!

[@ih8tusernam3s]

Wow, that's really neat, thanks for showing it to us. Still blows my mind they can put gyros and accelerometers into IC's.

[@VegasCyclingFreak]

Fascinating topic today. Very interesting design.

[@barjan82]

Would be nice to 'see' or even hear this unit running! Even if this has hardly any noise during running :)

[@gmcjetpilot]

1960's technology... awesome. Now these gyro platforms are all solid state with laser ring gyros. These are still amazing...

[@dheibeljr]

This is super cool. Love it!

[@Kalumbatsch]

If you carry on like this, soon you guys will have a complete Moon program together.

[@nicholaswade6289]

Keep up the great work!

[@jamesdougall]

Awesome Vid, thanks for sharing! Some very impressive ideas and tech from the 60s. Have you considered doing a video on how this compares to more modern Gyros and any features of the IRIG that are still used in Gyros today?

[@mariodistefano2973]

Hi CuriousMarc, you are doing a thing that *DESERVED TO BE DONE* long time ago.... It impresses me your knowledge of the various items needed... still waiting what would be the further developements of the (unfortunately faulty) Core Memory Bank... your are facing *REALLY THOUGH* problems, related to a Mission that meant alot in my childhood. And I appreciate it alot your efforts! A question: Is the IRIG Gyroscope needed for the Apollo AGC restoring? If so, Are you thinking to make a suitable inertial platform (stationary, of course) to put them on to?

[@williambello4089]

Holy cripes! I'm wondering how you're going to get a reaction control system! I am stunned and amazed that you were able to acquire an actual Apollo gyro!!!!

[@OriginalJetForMe]

I would love to see the 1-axis gyro you describe at 15:17!!

[@sanchesxxx1245]

amazing! thanks! I adore gyros

[@youreale]

Amazing stuff! thanks

[@OptimusSubPr1me]

That potting looks amazing.

[@RickeySmithEric]

This is a very interesting channel. I just subscribed.

[@bryanpotts5594]

God I love my fellow nerds. This is by far the coolest thing I've seen in quite a long time!

[@douro20]

Some air-powered rate gyros can run over 20,000 rpm. Modern LIDAR choppers have motors in them that can run at 500,000 rpm or more.

[@tombloom99]

Nice video. Gyros are fascinating. The air driven one would operate from either an engine vacuum pump or a venturi on the side of the plane, rather than carburetor vac. Thanks!

[@JohnSmith-mk8hz]

He probably meant manifold vacuum.

[@tombloom99]

@@JohnSmith-mk8hz Hi John, I'm sure he did, and I thought of that. But manifold vac would be too variable for a gyro. I've owned antique cars with vac windshield wipers that went from fast to nothing with any touch of the accelerator pedal. Also, one back fire would send a bunch of nasty stuff into it. Also, I have owned 13 airplanes in my life and none of them used manifold vac. It would mess with the fuel mixture and the FAA would never allow it.

[@tombloom99]

BTW, the guy just misspoke. He obviously knows about these instruments. Sorry I mentioned it.

[@JohnSmith-mk8hz]

@@tombloom99 Yeah the guy is very smart, he just mispoke I"m sure. I don't know much about airplane vacuum systems. I know you r'e in trouble if you fly into bad weather and lose vacuum for your instruments.

[@tombloom99]

@@JohnSmith-mk8hz Hi John, That is why all airplanes have a mix of gyro instruments that run on electricity and vac. So failure of one doesn't completely destroy your spacial orientation.

[@tipsonts]

Precision engineering.😍

[@s90210h]

The unexpected spacey Ambient was the best part

[@allenschmitz9644]

Great gift Idea for a V-2 rocket.

[@adrianvalbuena8158]

WoW masterpieces!!!

[@brentsrx7]

So cool!

[@1944GPW]

What a beautiful piece of engineering. Is there an external helium fill port on it? The very small atoms of Helium are a notoriously hard gas to confine inside machinery plumbing, according to a cryogenics engineer friend of mine who works with helium-filled equipment in radio telescopes. Every thread, every fitting, every pipe, every seal, everything has to be perfect - just like your gyro.

[@Keldor314]

Yeah, I can't imagine that much of the helium is still in there after 50 years. If you were to run something like this without the helium, would it damage it, or would it just perform poorly?

[@nejiniisan1265]

@@Keldor314, it would perform ok. But it would spend more power.

[@volo870]

Wow! I thought you'd just admire the thing, without intention to start it up, but I underestimated your insanity! Keep it up! Also, do you think it will start? Helium should have escaped, and liquid may have reacted with something.

[@koppadasao]

I'm curious, Marc. When are you going to go to the moon?

[@the_expidition427]

He may be one of the suppliers for the moon base.

[@zariski]

Come on Marc... i need a job :) let me be part of this amazing task! ps: ty for sharing this in video with us :)

[@Some_Beach]

That helicopter gyro is some iron man tier stuff

[@slippery396]

Sad reminder for me. When was a just a little boy, my father gave me a small gyro ... probably from a small missle. It had a wind up feature, so it could be wound up using a pair of needle nose pliers ... well, you know ... I wound it up too tight and broke the spring .... can't remember what happened to it after that. :(

[@chrismofer]

I have many vintage RC heli rate gyros that are mechanical hall effect rate gyros, I have 3 identical units and am very much considering making a 3 axis rate gyro and this has me thinking about a stable table approach with gimbal rings/spheres and servos so it can slew faster

[@arfink]

What company manufactured this gyro? I work for a place that makes ring-laser gyros that have long-since replaced these mechanical ones in the vast majority of applications, but the mechanical ones are still made today in very small numbers for extremely niche applications where the highest humanly achievable accuracy and long-term stability is needed. The vast majority of commercial aerospace and even deep-space missions do not need billionth-of-a-degree ARW accuracy though.

[@deviljelly3]

We're coming very close to the 50th anniversary... I would really like to see a video about Margret Hamilton... she has been forgotten

[@CuriousMarc]

Rest assured she has not. She is a Computer History Museum Fellow by the way, inducted in 2017 I think. I think they will have quite a few events with her and the MIT gang for the 50th anniversary of the Apollo landing.

[@deviljelly3]

@@CuriousMarc Good! I wish more people today knew about her.

[@ptonpc]

@@deviljelly3 That is more to do with today's society and its obsession on fame instead of rewarding the people who make this world better.

[@doc_sav]

Glad Ed stopped by.

[@LavenderSystem69]

I mean... the existence of the concept of gimbal lock implies that you can't spin it *all* you want, because that means that there's such a position which is terminal to the normal function of the gimbals. Therefore, you have to keep the spinning your heart desires within the confines of the normal range of operations, and try to stay away from the deadband that precedes gimbal lock

[@aserta]

3:42 mercury switches, awesome.

[@TheJimbodean67]

Do you have the continuum transfunctioner? Oh sorry, wrong movie. Great find, thanks for sharing. Never retreat, never surrender!

[@SimonSozzi7258]

Impressive

[@thcoura]

At this pace, when do you guys will start the reassemble of Saturn V? I would like to see the thrusters (joking)

[@ehamster]

When are you going to show us the Apollo 14 simulator DSKY that you bought at the same auction. ;-)

[@GeorgeGeorge-xj2bc]

The most interesting part of the missions to the moon is the digital logic cpus,the radio communications with earth and the energy from batteries.In that era these major facts were in that high technological level?

[@randomunavailable]

If you guys don't wind up on Nova some day, something is wrong with PBS.

[@phraggers]

Haha Beryllium Sphere "Never give up, never surrender!"

[@colderwar]

Wow it's Ed Thelen !!!! hope he's well. I have been visiting his Nike missile site for literally years

[@CuriousMarc]

That’s him alright!

[@mglmouser]

Ah! The beryllium sphere! Too funny.

[@tombloom99]

Beryllium is a dangerous element. Be careful!

[@greendryerlint]

@@tombloom99 Yeah, don't lick it too much..

[@PixelSchnitzel]

I just figured it out -- you're building your own Saturn V and you have Teletypes to keep collaboration with your cohorts authentic! amirite?

[@rkan2]

I wonder who will donate the RP-1 and LOX :D

[@theharbinger2573]

How much power did the IMU consume? Helium atoms are very tiny and incredibly difficult to keep contained, are you certain there is any He left in the gyro? As a design the gyros didn't need a long life, I don't think anyone would have wasted mass making the seals last 50 years.

[@jeromeprater183]

Most likely the some of the Helium has escaped. It would have formed tiny gas bubbles in the Chlorofluorocarbon suspension fluid. Calculations would need to be done to get a general idea of the rate of leakage with time.

[@thomasneal4775]

Great Video and congrats on snagging an Apollo IRIG. I'd like to construct an Apollo IMU stable platform without using genuine Apollo parts. The diagram you are coloring on apparently depicts a wire coil surrounding the Gyro Wheel. Both are located inside the beryllium sphere. Per an Apollo doc: "2 phase 800hz 28VAC" power spins the Gyro Wheel at "24k rpm." The gyro wheel itself is "constructed of beryllium with a steel rim." I would like to manufacture a gyro wheel powered in the same manner as in this IRIG. Can you provide any details on this AC-powered coil? Are there any unmentioned mods to a typical gyro wheel required to make it rotate? Thanks for any thoughts!

[@deviljelly3]

Wow!!!!

[@soulrobotics]

first of all, THANK YOU MARC for your curiosity, which is also mine!. 1.- Is great to have the actual gyro,..(pricey).. once you can get the gyro working, i would prepare a similar scenario in which it was used and let "Magic Mike" suck all the data. 2.- build 3 similar circuits to simulate those signals as an input to the AGC with the accelerometers. to see if the corrections are correlated... 3.- isn't be good to know also how much force/s a throttle can generate ? ;-) I feel guilty for not collaborating in this project, seriously!,... ill try to solve that. ps: that movie is hilarious! beryllium sphere, LOL! (Galaxy Quest!)

[@soulrobotics]

you guys did it! incredible!

[@reasonablebeing5392]

Imagine if you could find everyone who has bits and pieces of Apollo rockets - I wonder if you could almost build a complete one.

[@CuriousMarc]

We just discreetely whisk away the one in Huntsville. Make sure we deflate it before so we can put it in the back of the truck...

[@160rpm]

Watch out for gimbal lock!

[@digitalblasphemy1100]

I WANT TO SEE THE EARTH ROTATION TIMELAPSE WITH A STOP WATCH!!!!

[@joachim2464]

It might have been explained in this video, but it is way over my head, hehe. What was the method used to transfer the signals from the instruments inside the main gimbal assembly? Sounds like a unique challenge since everything is spinning around it?

[@CuriousMarc]

They used slip rings. You are right. It was indeed a big challenge to keep the friction low yet make them reliable. They were custom designed and integrated with the gimbal position sensors and motors.

[@chuckbown]

Once this project is done, will you be able to use it as an input to the AGC?

[@ChrisMower]

“Piece of cake” 😂😂😂😂

[@incargeek]

On a nominal mission were the BMAGs in the CM running all the time, ready, if they were backup gyros?

[@g2g591]

The bmags were turned off (left on warm-up power) during sleep periods..Actually, they even powered off the imu during many rest periods, they realigned using the stars and the sextant shortly after wake up.

[@RB9522]

Designed after a beer.

[@TheRealMalvaX]

So these gyros and the inertial platform were also designed by MIT instrumentation lab? And who manufactured them?

[@TreyVaswal]

So what temp does the gyro need to be at when it runs?

[@lwilton]

It's interesting they acronymed it the IRIG, since that had another meaning that probably slightly predated Apollo, and was used on the Apollo project: Inter-Range Instrumentation Group.

[@CuriousMarc]

IRIG stands for Inertial Reference Integrating Gyroscope. The Block I was called an IRIG 25 (for 2.5” diameter I presume?), the Block II was the IRIG II.

[@AllElectronicsGr]

If they already had this very pricise gyro, why they were mounted on the gymbal with feedback?

[@jeromeprater183]

For complete rotational isolation or decoupling. The inertial platform gimbals do all the mechanical "work" while the gyroscope only does the sensing.

[@AllElectronicsGr]

@@jeromeprater183 Thanks! So the resolver of each gyro reads its output torque? Or angular displacement. Well, I think that both would work with the right amount of gain on the closed loop

[@jeromeprater183]

@@AllElectronicsGr Yes, the electrical signal output microsyn or angular position sensor of the gyro float is amplified and sent to the corresponding direct current gimbal motors of the IMU to continuously null or re-center the gyro float position. The trick is to tune the gain to the correct resonance frequencies or I should say to avoid resonant frequencies in the servo loop and still have sufficient dynamic range.

[@AllElectronicsGr]

@@jeromeprater183 This you be a really nice project! I will try to do something like that in my channel. With digital and micros the control part should be a lot easier today. But, this old machining.. A lot of thecnics died with the guys that manufactured this stuff. Sad

[@CuriousMarc]

As @Jerome Prater said, so the gyro would do zero mechanical work, be free floating and keep its ultimate precision. And it’s too small to actuate the platform on its own anyway. So it’s used purely as a sensor instead: tilts up or down when it rotates around the sense axis as I demonstrate with the rate gyro. Except there is no spring to bring it back. Instead the servoed gimbal motor turns the platform back in the other direction around the sensed axis, which will bring the gyro back in its original “nulled” orientation. It’s amazing how well it works.

[@Christian-zv2em]

I have a question: To my understanding this is a gyro from the ST 124 inertial platform which was a part of the Instrument Unit (the ring above the third stage of the Saturn V). The IU had its own navigation computer. So this gyro had no direct connection to the AGC, or did I understand something wrong? What so ever, it is an engineering marvel.

[@CuriousMarc]

The gyros and computer used in the Saturn V IU were completely different animals. The computer was made by IBM and the gyros by a completely different company, I can't remember which.

[@Christian-zv2em]

@@CuriousMarc Ok, Thank you for the answer. Maybe I was confused by reading about the ST 124 in a book. On the first view the Saturn and the Apollo inertial platforms look very similar. The ST 124 was made by the Bendix cooperation: en.wikipedia.org/wiki/ST-124-M3_inertial_platform . (thanks google:-)) I also found this: kzbin.info/www/bejne/aZaqcpVnbZdoe6s

[@Dountman]

How does the gyro work in zero gravity? Doesn’t it need that force to “level” itself constantly through flight to keep the platform in alignment?

[@CuriousMarc]

It was aligned with a laser reference on the ground, then with stars sightings once in space. It also was vastly lower drift than anything else that had been done before. Still, they did a fine align with stars before any critical maneuver.