- The Saturn V rocket took humans to the moon
for the first time, but the humans didn't steer the rocket.
It steered itself using a computer.
- [Man] Tower, clear.
- [Man] Gotta roll program.
- A lot of the Saturn V rocket was built here
in Huntsville, Alabama, otherwise known as Rocket City.
And one of the really cool things about living here
is it's filled with aerospace and computer engineers
who love this stuff, so a thing you can actually do here
is pick up the phone and call one of your friends
and have them call their friend, and before you know it,
you're in a parking lot, receiving a Saturn V
memory module from a guy you just met,
and he just trusts that you're gonna give it back to him.
This is 14 kilobytes of data, which is really interesting
because the same day I got this,
I had Linus Sebastian from Linus Tech Tips here.
We were installing a server that was over 100 terabytes.
Now, millions of people look to Linus
to understand more about modern computing hardware,
so I thought a really cool thing to do
would be stop what we were doing with the server
and take a closer look at this memory module
and how it works.
Let's sit back and watch a modern computer nerd
learn about the cutting edge technology from the 1960s.
I'm Destin, let's go get smarter every day.
- [Destin] Have you ever seen a Saturn V rocket?
- [Linus] No.
- [Destin] Okay, do you know what the Saturn V is?
- [Linus] Yes.
- [Destin] My daily life literally revolves
around the Saturn V.
Like, that's the Saturn V peeking out
over the trees right there.
- [Linus] Oh, there it is.
Hello.
- [Destin] In the 60s, they had just started building
digital computers, and I'm gonna show you the computer
that they used to steer that thing.
- [Linus] I mean, it's gotta be a bit
of a terrifying experience having, like,
the equivalent of a very large bomb
strapped to your butt.
- So this is the brain for the Saturn V rocket.
If you look up right here, this is the instrumentation ring,
and so they had computers on here that were digital.
This right here is the launch vehicle digital computer.
That is it.
This right here is a memory module, okay?
And if you look really, really, really close,
really close, you see those little bitty rings?
- Yeah.
- [Destin] OK, look right here.
Look at that.
Do you see that?
- [Linus] Holy smokes, so they're,
it looks like zip ties on chicken wire.
- [Destin] Okay, those are bits.
Those are physical bits.
So you see that screen?
- [Linus] Yeah.
- [Destin] These are wires that go down
to these boards right here, right?
- [Linus] Yeah.
- [Destin] On each node, you have an iron ring,
and depending on how the iron ring is magnetized,
that's a one or a zero.
That's how they programmed this computer.
Seriously.
So look at this right here.
- So by hand.
- [Destin] By hand, yes.
- They threaded these wires through the,
I mean, who has a steady, I don't even think
you can build one of these today if you wanted to.
That's incredible.
- [Destin] So there's a guy that worked on this
in the 60s here.
His name is Luke.
- Yeah.
- [Destin] And, you get ask him all of these questions.
- Fantastic.
- I'm Luke Talley, and at this time in 1969
I was a senior associate engineer at IBM in Huntsville.
- [Destin] So your computer pointed the rocket?
- That's right.
- [Destin] Awesome.
- We steered the rocket.
So that's a memory module.
- [Destin] That's a whole memory module, yeah.
- You musta shot somebody to get that.
- [Destin] So how valuable would you say that is?
- Well, now this, ah, I don't, I'd have no idea.
You have to go to Antique Roadshow.
This computer controls all the timing.
Start engine, stop engine, fire separation rockets,
fire retro rockets, all this kinda stuff.
It does navigation and guidance.
You have stored in the memory a profile,
at this point in time I need to be here,
going this fast, going this direction.
Now realize that this is core memory,
so you have these magnetic cores,
you have the wires feeding through the cores,
you push a current down through a wire,
if you've got a wire, current's going in that direction,
the magnetic field is going to be in this direction.
If it's going this way, it'll be that way.
Make that a one, make that a zero.
There's 8192 of those on this plane, all right?
- [Linus] Yeah.
- Then there's 14 of those planes stack up
to make this module.
This module is what you're holding.
All this stuff now, the drivers to drive this thing.
- That's just to program it as a one or a zero.
- Because this is basically an analog process.
- Right.
- I'm not writing ones and zeros into a logic gate
and storing them that way.
- You're just sending a current --
- I'm actually having to make, magnetize a core
one way or the other.
And then I've gotta read it, and when I read it,
I destroy the magnetization, so I have to turn
right back around and --
- Write it again.
- Write it back in there, so that it's not missing.
- Oh, no!
- So there's one of these in this,
and then there's one of these now
in each one of these blocks on this wall over here.
- [Linus] Got it.
- So we have four, 8, 12, 16 thousand words of memory,
another four, 8, 12, 16 thousand words of memory.
Now when the Saturn's flying, both of these memories
are executing the same flight program.
- [Linus] Completely in parallel?
- That's right, and they're comparing the outputs
to make sure they're getting the same answer.
If they were to not get the same answer,
go into the sub-routine and say,
"I'm at this point in the flight,
I got these two numbers, what makes the most sense
to keep using," use that number and keep going.
So your critical parts are triple-redundant
in the logic, dual redundant in the memory.
As I recall, during all the Saturn flights,
we had like, less than 10 miscompares,
something like that.
It was a very small number.
- When you're building a rocket,
you have some important parameters
that you have to monitor.
Power, data bandwidth, mass, volume,
you have to manage these so they don't get out of control.
So you want a reliable system, but at some point,
you have to make a decision.
How redundant is redundant enough?
- Unreliability, that's the key,
because the more of these things,
the more core's you add, the more of this stuff you need,
the more unreliability you add to your system,
because sheer numbers of parts.
- Right.
- Luke is about to explain what it was like
to receive data from the Saturn V via telemetry
and then analyze it, and I'm gonna let this play out,
because I want you to understand how repetitive
and difficult this task was.
Today we could do this with just a few minutes
and some spreadsheet software, but back in the day,
they were the computers.
Like, the people were the computers.
So I want you to see it through his eyes,
through this historical lens so you understand
what it was like to analyze the Saturn V data.
- So did you pull the data down while it was flying?
- Things happen too quick in flight to.
- [Destin] How do you know you had --
- We get the data back and then we ana,
that was my job at IBM, was we were analyzing
the flight data to determine what worked,
what didn't work, if it didn't work on this flight,
how do we fix it on the next flight?
- Got it.
- And then when you get the NASA requirements
for the next flight, make sure we got everything
in place to do what we were supposed to do,
so the data tapes come from all around the world
through Goddard Space Flight Center's responsible
for that, so they get us the data and then we analyze it
and determine what happened.
Something would go wrong in the computer,
and it always goes wrong when something else
is messing up the telemetry system, so we would
actually get what they call an octal dump.
We have this 11 by 17 sheet of paper, 10-bit octal numbers,
so you'd have, there were four characters.
Zero to seven's as high as you go with octal arithmetic.
So you got all these things, I think it was like,
maybe 40 columns and 30 rows or something like that,
so we would get this thing printed out,
and all it's just numbers, well, the piece we're looking for
is in a particular place down here.
Well, the drop out is where we, you know,
telemetry dropout, we would actually get this printed out
11 by 7 fanfold paper, spread it down this hallway,
get down on your hands and knees,
make a template, cut out the, you'll have a number
of measurements that'll always be the same, you know,
like a bolt, it never changes, so we know what
those number's oughta be.
So we cut the holes out and slide it down
page by page, "Oh, hey, these all look good!
"Okay, this frame's probably good."
So we go find so many columns, so many rows,
find the number we want, write it down.
- So you're looking for one -- - Go to the next one.
- If it bungs up something that you know is a fixed value
then it probably bunged up something else.
- That's right, and if the fixed value's okay,
then somewhere in there our number's probably okay.
- And then once you've got the problematic one,
I mean, is that just the world's nastiest sudoku puzzle?
How do you solve that?
- Well, no, you may have, you may have to do this
for many, many, many frames.
Then you take it to your desk and take those octal numbers,
convert 'em to decimal numbers,
go to a calibration chart and say,
"Okay, I got this number."
Go up my chart and say that means
it's five degrees Centigrade.
So you write down five degrees,
then you figure out what frame you are,
and that's about what time it is,
so you're, "At this time, I had five degrees."
Then you go to the next one.
Now you do this for about two weeks,
and finally you got enough to plot a graph by hand.
So you put all these numbers in
and you plot it by hand, and then you say,
"Hm, that wasn't the problem after all.
"Oh, well, here we go again."
(laughs)
- [Linus] Oh, boy.
- [Destin] This is Ed.
Ed is the head curator.
- Hi, Linus, how are you?
This is kind of an in-the-hand example of the memory cores
that you can see woven into the spread here
and then kinda under the magnification over here,
and there's about eight or nine of them in there.
So like Luke was saying, when you run the current
through there, it starts to spin that doughnut
in a particular direction, and that tells you
whether it's the one or the zero.
And you were saying they were woven on by hand,
and it was primarily women that did the work,
that had basically a bench top.
- So they would have like textile industry experience,
I guess.
- Um, I am actually not certain
what their qualifications were,
but they would sit with a bench top
with this thing mounted in a holder
with copper wire lengths and tweezers and their fingers
and a lot more patience than I have,
to weave these things through there,
to make sure they went through appropriately,
no kinks, no bends that were out of the spec,
and to actually make sure that the little doughnuts
go into across the way they should
and that it was all uniform
so everything would be predictable behavior.
- [Linus] Incredible.
- [Destin] I just wanted you to hold the physical bit,
now you know what that's like.
- I mean, this is, this is more than 8 bits,
so I'm holding at least a byte.
(laughs)
You can look at it that way.
- [Destin] So when you look at this,
what kind of emotion do you feel,
when you look at this, Luke?
Do you, do you, are you proud?
- Is it fondness, or is it more just,
"Thank goodness I don't have to work
on that bloody thing any more"?
- No, I'm gonna talk to one of my buddies
when you go out the building,
see if he'd hit you in the head.
(laughs)
- [Destin] To get this thing?
- Yeah.
No, that's a real piece of work,
and it looks, to people that come in here,
they say this just looks so much like an antique.
But again, we only had a few failures
during the whole flight that were intermittent.
We never had a catastrophic failure.
- People might say antique,
but I would say hand-crafted.
- Yes, it was a lot of hand work went into these.
- [Linus] Oh, you can tell, I mean, even just,
even these are clearly hand-baked.
- Well, they got the goop on 'em
because the big problem with this thing is vibration.
The memory that we were looking at over there --
- Yeah, you got physical rings on there.
- They test and test and test on that thing
to make sure that you hadn't got a kink in a wire
or a twist, 'cause if you do, the vibration's
gonna cause it to break.
Those things were made by hand.
The ladies actually wove these things
like you're weaving a piece of cloth.
Pretty amazing.
- [Linus] Oh, this is fascinating.
Thank you very much, by the way.
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That supports "Smarter Every Day."
When you support "Smarter Every Day,"
it lets me do more videos about the stuff I love.
If you want to see more of this interaction
between Linus and Luke, it's incredible.
Like on the second channel, there's a 30 minute video
of Luke going all the way down the rabbit hole.
This guy knows his stuff.
Like, I feel like I know rockets pretty well,
Linus certainly knows computers,
but when we're sitting there, it's almost like
Luke could just run around both of us.
Go check that out on the second channel.
Also go check out Linus's channel.
Actually, I'll just let Linus do an outro himself.
Go check out Linus's channel, Linus Tech Tips.
He's talking about, what's it called again?
- The instrument unit, basically we talk a little bit
about the computer but Destin's got a little more
information on that, but I really love
the cooling system on this thing,
it's gonna blow your guys's mind.
Unreal.
- It's awesome, it's at the top of the rocket
because as you got all three stages of the Saturn V,
you need your instrument unit way up here
so you can guide the Saturn V
before the Apollo computer takes over,
but Linus talks about details
of power and how that stuff works.
It's pretty cool.
- Yeah.
- [Destin] Thanks, dude, appreciate it.
- See you guys.
Thank you.
- [Kids] You're welcome!
- Thanks, guys!
- [Destin] It's called space camp.
- Space camp.
- [Destin] Yeah, so all those kids are here to learn
how to be astronauts and fighter pilots.
That's Luke.
- [Linus] No!
- [Destin] That's Luke.
- No way!
On the left there, apparently.
- [Destin] That's pretty cool, huh?
- [Linus] Luke Talley, there it is, far left.
That's nice.
- [Destin] That's pretty neat, isn't it?