F8 Fly-By-Wire System (Apollo Guidance Computer Part 31)

14 were cancelled? Yes, she would have flown like Apollo 18 or 19, or something like that. Ah OK. Because the number LM 14 does not mean Apollo 14. Right, right. However, speaking of Apollo 14, the strings we are going to read are the 8 from Aurora 88, which is the final test string of the lunar module

system

. And set 8, at least in 1969, was the test string set assigned to LM 8, which is what flew on Apollo 14. I don't know why they're in this. I don't know why this doesn't have the F8 strings. Because the strings are behind this box, you actually have to go out of your way to change the string modules.

You have to remove this box. Yeah, why would they put any Apollo software back on that thing? I don't know! I have no idea. It's very interesting. Or did they want to protect the F8? Yes, it could have been secret. Secret or something and deleted it? For a moment I thought maybe they were feeding... The rope flying on the F8 was called DIGFLY. Well. Oh, digital fly? Yes. They had an eight character limit for their name, but they could also set the string's author, so the string's full name was DIGFLY for "Wire" as the author, so they spelled everything DIGFLY BY WIRE.

Anyway, I thought for a minute that maybe they introduced the DIGLFY string into the test connector like we did when we were on our restored AGC, you know, like running a core string simulator. But this AGC has a reset monitor connected there, which simply adds channel 77. So this means that they most likely didn't do that. So yeah, I don't have any good theories. Well, you have more theories than anyone! And while we're at it, we were drooling - we're in Steve Jurvetson's cave - and we were drooling over this, which we didn't see last time. Which is the engine of the Apollo SPS service module.

The one that brings you back from the Moon, back to Earth. Or it allows you to enter orbit around the Moon. It's pretty impressive. Yes it is. And they told me it was, so I didn't know, it was redundant. These are two rocket engines in one. Everything is dual. So if you have one set of injectors that doesn't work, you use the other set and can still go home. It's an impressive beast next to the RL10. It's actually quite big compared to the RL10, right? Once you have the bell on, it will probably be much bigger.

Oh yeah! So it's much bigger. Pressure fed motor, for greater reliability. And we discovered that these were not the oil filters, they were the gimbal actuators. So there is one that is connected to the motor, from the ring to the motor. And one that is connected to the spaceship itself. And then... So, it actually mounts from this ring from below, not from above. Too many things to look at! Alright. So you're here for the string and you have your core string reader, let's do it. The pin spacing looks like they are probably Malco pins. Is it another logic box, perhaps?

Yes. Or I guess they had different sensors, right? Because they need to find out what the pilot's contribution is. And down there is our nice radioactive AGC. Oh man, six strings! Three. Three of them are bridge modules. Ah OK. It's the most strings I've ever seen in my life, so I get really excited. Although these two seem suspicious to me. Are they like a darker gray around the letters? It's almost like they're done... ...re-labeled it? So I'm going to take them out and make sure there's nothing in them. Oh, that's appropriate. So those are... they're full of hydraulics, because they have cooling plates.

Yes. So if I were to run that, we would have to connect it to a cooler. Which is fine, to be expected, right? Here you have. Here's number one! Mr. Ken has just arrived. And how's it going? Well, we're already looking at other things like... ...I noticed that another engine has appeared! And Mike is being very expeditious, he's already... It's interesting. Oh, is there some reworking? Tape? No, that's epoxy or something. Redo? Yeah, so they went in there. Then you can also repair the core modules, huh? I think this will be on one of the diodes.

And what is this engine? This is the SPS. This is the motor on the back of the command module. It is empty? Is it a jumper? Or is it not a sweater? It's a... I don't know. I would expect some sort of resistance set to be up there, but this is pretty evenly weighted. Then I do not know. I'm going to put it in the string reader and see if I see anything. You can read jumpers! So this whole platform is supposed to be accelerated? Yeah, there's one here, a little accelerometer that they put there. Oh, there are two!

Yes, this entire palette went into the F8 as is. X and Y, but those are additional. Maybe these are replacing the BMAGs (body-mounted accelerometer gyroscope)? I mean, the PNGS didn't use BMAGs at all. Oh, it's just for... ...the SCS (Stability Control System). Well. So I don't know, they added things to it. Oh, it's going to... No, it's independent, it's going to its own wiring

system

. So continue on from here and it's actually a yellow

wire

addition. Is here. They are all heavy, so there is something structural there or they are just completely encapsulated. They just like to fill them completely with potting material.

No, at least I won't be able to read this one! I just realized... It doesn't have pins? The drive pins are missing. Okay, so he's definitely a jumper? Are you missing the drive pins? I thought the pins were the root. Are they all like that? One of them is not like that. This one is not, and it is the one without the suspicious letters. Strange. That box is the cooling system. I did not noticed it. Coolant purge valve. Sight glass coolant. Two-way valve manual. Refrigerant pressure gauge. I like this valve, it looks like a garden hose!

Liquid nitrogen. No? LN2? There is a nitrogen gas vent here, so it's probably liquid nitrogen. Do you cool it with liquid nitrogen? Oh yes, it could be! Yes, they simply cooled it with liquid nitrogen, which made the system completely independent from the rest of the plane, but I think it limited the flight time to about an hour and a half. LN2 filling inlet accessory. Yes, liquid nitrogen! LN, is liquid nitrogen. Tada, tada, tada! Recovered! Well. Next! I think your box needs a little more drama. It gave us a bit of drama, because I had my direction a little wrong the first time I read something.

But there has to be, you know, a big panel meter that you watch charge and it should make a whining sound... So, have you gotten the block ones back yet? Yeah! Did that work well? If it works well. There was a string (I think I already told you about this) that had a dead diode, but also a broken core. Oh yeah. I lost eight memory locations from that. Turns out I found someone who has the same modules. So the chances of it having the same broken core are incredibly small, so I'll read it next month. So you could recover the lost data from parity?

No, not with a broken core. Because you lose all the eight-word fragments. You basically get nothing for those eight words. So, I think I reverse engineered them back. Okay, but you want to be sure. Yes. One more! Yes. Aurora 88, Module B2. This is the one that had the rework. Do you suspect a diode? Have you seen some faulty diodes? Not this type of diode, which is why it's a bit strange. We can take a look at the model and see where that rework is. I think the reworking ended here. So either hit one of these, which is a resistor, or...

Oh, so you have access to the firewood components on the side, I get it. Actually, I think it's just a resistance. Resistance, yes, so there are only resistances in that. How can a resistor go bad? I don't know. That's assuming you remember correctly which side you're on. So let's take it out and take a look. This block here is... Yeah, 203052. So... Yeah, it would have just been one of these resistors, about halfway down the line. Latest! Well, here we go! Aurora 88, module B3. Tada! Oh, are you running them? Here you have! Alright! We are simply running the ropes that we just recovered.

Yeah! So is this similar to what you ran when we tested the

computer

, when we first turned it back on? Can you do the RAM test? That's what I'm running right now. But how similar this is is a really interesting question. Because what we ran was called Aurora, and this is Aurora. But I don't think they are the same Aurora. Oh, do you think they are significantly different? I think so. So you don't have a listing for that one? We don't have a listing for this. Oh, then this is a totally new software for you! Yes.

So this is revision 88 of Aurora, which was released in March of '96. Aurora 12 is from November of '96... ...66. Yes, 66. Yes, so Aurora 12 came out much later than Aurora 88! That? Aurora program from the DAP group, the Digital Auto Pilot group. Aurora should have been owned by the LM group or the system test group. I'm pretty sure what happened is that they checked Aurora through 85 and then branched off into Sunburst, which was Apollo 5 (Apollo 5 is LM's first flight). And then the DAP group, which was created in

part

by contractors outside MIT, spun off from Sunburst and called it Aurora, possibly unaware that that name was already in use.

So the Aurora we got from Don (Eyles) has a lot of DAP code. What we were running as our Aurora was much closer to the early Sunburst reviews. Like around Sunburst 10 or so, and not Aurora 85 or 88. So Aurora is just a test. The real Aurora is just a test, yes. It was the first LM rope they made. And then to create the Apollo 5 software, they broke away from Aurora and started developing... Oh, so is there any code that made it into the flight software from that? Oh yeah! Ah OK. Yes, Sunburst, I remember that, that's the title of Don Eyles' book.

Yes, Sunburst and Luminary. He skipped Sundance. But this is before. Therefore, you may have less flight software. This one doesn't have any. Well. So it's the pure, unadulterated original AGC test. Good. It will be very interesting to take this a

part

and see. You just had a job on your hands! Yes, there is a lot of work to do! Well, congratulations on getting some more strings back. Yes, thanks. So, this adds to the growing pool of strings recovered by Mike. They weren't exactly the strings we expected to find, but they were still the important Aurora 88, the first LM string ever produced, representing the complete LM AGC test set.

And this is just the beginning for Mike, as he then works on disassembling the recovered code to reconstitute the source code, something at which he has been quite successful. The result of his work is accessible on AGC's virtual github. Congratulations Mike, you're doing more Apollo software recovery on your own than all the museums in the world combined. See you in the next episode!