Hello and welcome back. If you follow
the channel, you know that we recently opened a Soyuz Navigation Computer better known as the
Globus. Inside, we found an amazing analog computer powered by lots of gears and a
very little bit of electronics. This oddly anachronistic, yet magnificent instrument
was used until 2002 in the Soyuz T and Soyuz TM capsule. Unfortunately, it was badly banged up,
probably from a drop, the globe was stuck and the mechanical front controls did not work.
We quickly traced that to the globe supporting shaft, which had been dislodged by the fall.
We carefully removed the globe to see if we could repair it. From the globe markings,
which included NASA tracking stations, we are pretty certain that this Globus was assigned
to the Apollo - Soyuz rendezvous flight in 1975. Which jives well with the shown location of the
Vanguard tracking ship and the 1973 date codes on its components. We don’t know if we have the one
that flew, or a backup one, or one that was meant for the flight but was set aside after a big fall.
Fortunately, we were able to reinsert the shaft after deburring its slightly damaged
bearing. That freed up the controls, and we were able to move the globe manually.
In the last episode, we explained what the controls and indicators do:
the orbit position and longitude adjustments, the orbit time adjustment, the orbit indicator,
the landing angle adjustment, the latitude and longitude indicators,
the light/shadow indicator, and the landing position light.
But you know us, we don’t tear things down, quite the contrary,
we reverse engineer them, repair them, and make them work as they were intended to.
However, an obstacle stood in our way. Most of the electrical wires
had been cut-off. Which is quite puzzling, since the unit had a tamper proof seal on
one of its screws. So the cutting of the wires was both intentional and official,
maybe to prevent the further use of the device after its big fall.
But a whole bunch of cut wires is nothing that Master Ken cannot reverse engineer,
when he has his Google lab coat on. Heck, he can reverse engineer an Intel 8086 chip
by just looking at its transistors, so a few cut wires was just a little extra challenge.
[Marc] So, Ken, we're ready to attempt a power up?
[Ken] So I've traced the wiring through, and I figured the two solenoids are wired to these pins,
and so when we put pulses in here, it should make the globe rotate.
[Marc] And I went all out, and put my HP equipment in good service. We have one
second pulses driving a little pulser, and then being amplified to 28 volts.
[Ken] 27!
[Marc] 27. If I just press the button, that should be it.
Oh!
[Ken] It's clicking!
[Marc] I hear clicking!
[Ken] I don't see any motion, but I guess motion is very slow.
[Marc] You have to wait...
[Ken] ... you have to wait a day!
One clicky is for the earth rotation, one clicky is for the spacecraft's rotation.
[Marc] Okay.
[Ken] So, the other clicky is underneath there.
[Marc] I can see it clicking.
[Ken] Yeah, yeah, it's clicking.
[Marc]
I think we should turn it around, and I should make a...
[Ken] A time lapse!
[Marc] ...a time lapse of it. All right! But we're flying apparently.
[Ken] Yeah!
[Marc] Do you see it moving, Master Ken?
[Ken] Yes, we see it moving. And we launched from Baikonur, the number seven here. And now you can
see we are a few millimeters past the seven. And we set it to exactly 90 minute period,
so it should complete a full orbit in 90 minutes. Of course, by that time,
the Earth will have rotated, so it won't go back over Baikonur, it will be over a different point.
[Marc] Oh yeah, it's moving!
We started at the seven, right?
[Ken] Yeah.
So our spacecraft is really cruising along.
[Marc] All right, the Globus is working! This is what it looks like, sped up by a factor of 8.
[Ken] Should we try over-clocking it?
[Marc]
Yeah, so, it's moving so slow, the idea is: can we overclock the thing? I can do 5 Hertz.
There you go! Now it's moving!
Okay, and then if I make the pulses a little smaller...
...I can get it to
go faster.
Should I go 10 Hertz?
[Ken] Make it sound like a woodpecker.
[Marc] Overclock!
No, that's too fast.
Yeah, here we go.
[Ken] Yeah, now it's visibly moving.
[Marc]
Here, you can watch the orbit fine time correction reset as we explained in the previous episode. The
arm will jump back to zero, without disturbing the mechanism, thanks to the friction clutch.
Boing. It just snapped back.
Now, if we speed it up by a factor of (8), this is a total speed up of 80.
However, as we were admiring the spinning globe, we realized that something was not quite right.
Can you spot what is wrong?
Let me show you. Let’s first freeze-frame as we fly over the equator. The latitude on
the left shows zero, as it should, and the longitude indication on the top says 180,
closely matching the location on the globe.
Let’s keep on going for a little more.
Alright. Now we are at 240 degrees East on the globe, but the longitude indicator scale says 247.
It’s a little off, but not too bad, so let’s fly a bit more.
Now we are really off. We are at 315 degree longitude on the globe,
but the indication is 282 on the scale. Meanwhile, latitude is still correct.
It eventually gets much better here,
though we are still a few degrees off. Have you guessed what's causing this?
While we were rotating the globe, we discovered that the indication in longitude is not
properly timed. At some height in the globe it's okay, at some other height
during the orbit it's not okay. And the reason is that there is a correction
for it, that has to be timed with the correct latitude.
When you are flying at 51 degrees - I should put the equator, so here's your equator -
so, the Earth spins this way, but you spin around here.
Right, you go woo-hoo.
If you were flying along the equator, the longitude indicated on the globe would be the same
as the longitude you are flying. But since you are flying at an angle, the longitude indicator
has to be corrected. And you have to subtract a correction, and then add it back on, so that when
you are here, you have zero correction, and when you're over there, you have subtracted something.
And to do that, they do use this specially calculated cam,
plus a differential mechanism that adds the 0 to 360 to it.
So, that's the adjustment cam for the reading here. So, it takes the rotation of the earth,
then through this differential - there is a differential somewhere,
that adds this correction. So you get the correct longitudinal reading
while you are moving up and down the Earth, which will push you ahead and behind.
But previously, what I had just done, is move this thing so it was correct
into one position. But that's not enough, because then it's not in sync with this one.
So I should ignore this, and make sure the correction is done properly, and then adjust it.
There we go. There's a cam adjustment here, but the indication is read directly from the cam. So,
as long as this is timed to this, I should be good on latitude.
So now, this is the one that's wrong. Can I turn it around? Yes, I can.
That's the equator, roughly. So, now,
I am on the max of the timing cam, and on the equator. Is there a way that I can test?
Okay. So I have to do that again.
So, we finally got it right. And this is Antoine's diagrams. These are mine. We got confused so many
times. First, we saw marks. There's clearly a mark over here. And then we said: okay,
fine, we have to align the mark over here, and when that timing mark is aligned, then we have
another timing mark over here. There you go.
And when this other timing mark is here, they should be in time, and everything will
be fine. And then, we tried that, and the longitude indication was completely wrong!
It turns out, that the way you have to tune the cam, is to have it
at zero when it's at 45 degree angle. And that, it took us a whole afternoon to figure that one out!
And it is because we forgot that there was a differential, and you have to add this constant
thing to it. Which means that, basically, you want the indicator to almost stop when
you are the maximum elongation over here, at point B. And what happens, that happens when
the linear part is being subtracted to the cam at exactly the same speed. And then it's zero.
And it's a differential thing. So, anyhow, you actually have to have this kind of alignment,
where at the equator, you want to be over here. And at 45 degrees, that's where you have to
align it, you want the maximum or the minimum correction, depending on how you count it.
Am I at 0? Yes. So if I go at 45 over here,
then on my cam down there, I am at the minimum of the cam.
And once you do that, well, everything falls into place. You turn your globe, and
we were on 135, (it reads) 135. And we're back onto 180, (it reads) 180. And now
the whole thing works. And it only works if you fly along that 51 degree dot something.
Alright, we should be all repaired and ready
for a time lapse of 7 orbits around the planet. Here we go.
You can clearly see how the longitude indication is speeding up and slowing down in a complex way,
due to the cam correction. The black and white scale at the bottom is the
daylight/shadow indicator. Then on the left, the latitude, also calculated by a cam. To the right,
the digital counter is the orbit counter. What a beautiful representation of space flight.
Here is another view from a different angle.
The globe now works beautifully, but we have one more thing to repair:
the landing point indication, which makes use of the electronic relay board.
Hopefully we’ll get that going in the next episode. See you then!