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Reverse-engineering the electronics within the Globus analog navigational laptop

Reverse-engineering the electronics within the Globus analog navigational laptop

2023-03-06 02:24:10

Within the Soyuz house missions, cosmonauts tracked their place above the Earth with a exceptional electromechanical
system with a rotating globe.
This navigation instrument was an analog laptop that used an elaborate system of gears, cams, and differentials
to compute the spacecraft’s place.
Formally, the unit was referred to as a “house navigation indicator” with the Russian acronym ИНК (INK),1
however I am going to use the nickname “Globus”.

The INK-2S "Globus" space navigation indicator.

The INK-2S “Globus” house navigation indicator.

We lately obtained a Globus from a collector and opened it up for restore and reverse engineering.
Though the Globus does all its calculations mechanically, it has some electronics to manage the motors.
Inconveniently, all of the wires within the wiring harness to the exterior connector had been lower so
I needed to do some reverse engineering earlier than we may energy it up.
On this weblog put up, I clarify how the electronics function.
(For an summary of the mechanical elements contained in the Globus, see my previous article.)

A closeup of the gears inside the Globus. It performed calculations with gears, cams, and differentials.

A closeup of the gears contained in the Globus. It carried out calculations with gears, cams, and differentials.


The first function of the Globus is to point the spacecraft’s place. The globe rotated whereas fastened crosshairs on the
plastic dome
indicated the spacecraft’s place.
Thus, the globe matched the cosmonauts’ view of the Earth, permitting them to substantiate their location.
Latitude and longitude dials subsequent to the globe supplied a numerical indication of location.
The sunshine/shadow dial on the backside confirmed when the spacecraft can be illuminated by the solar or in shadow.

The mode of the Globus is managed by a three-position rotary change close to the highest of the Globus.
The center place “З” (Земля, Earth) reveals the place of the spacecraft over the Earth.
The left place, “МП” (место посадки, touchdown website) selects the touchdown place mode.
The third place “Откл” (off) turns off many of the Globus.
This rotary change is surprisingly sophisticated with three wafers, every with two poles. A lot of the electronics
undergo this change, so this change will seem typically within the schematics beneath.

The rotary switch to select the landing angle mode.

The rotary change to pick out the touchdown angle mode.

Within the touchdown place mode, the Globus rotates to point out the place the spacecraft would land for those who fired the retrorockets now.
This allowed the cosmonauts to judge the suitability of this touchdown website.
This place is computed just by quickly rotating the globe by means of a fraction of an orbit, for the reason that touchdown place
shall be on the present orbital observe. A lot of the electronics within the Globus management the motor that performs this rotation.

Overview of the electronics

The Globus is primarily mechanical, nevertheless it has extra electrical and digital elements than you may anticipate.
The mechanical movement is powered by two solenoids with ratchets to show gears.
The touchdown website mode is applied with a motor to rotate to the touchdown place, managed by two restrict switches.
An electroluminescent mild signifies the touchdown place mode.
A potentiometer gives place suggestions to exterior gadgets.

To regulate these elements, the Globus has an electronics board
with 4 relays, together with a germanium energy transistor and a few resistors and diodes.2
Bundles of skinny white wires with cautious lacing join the electronics board to the opposite elements.

The electronics circuit board.

The electronics circuit board.

The again of the circuit board has a couple of extra diodes. The wiring is all point-to-point; it isn’t a printed-circuit board.
I’ll clarify the circuitry in additional element beneath.

The back of the circuit board.

The again of the circuit board.

The drive solenoids

The green cylinder at the front is the upper solenoid, driving the orbital motion. The digit wheels to indicate orbital time are at the left.

The inexperienced cylinder on the entrance is the higher solenoid, driving the orbital movement. The digit wheels to point orbital time are on the left.

The Globus accommodates two ratchet solenoids: one for the orbital rotation and one for the Earth’s rotation.
The complicated gear trains and the movement of the globe are pushed by these solenoids.
These solenoids take 1-hertz pules of 27 volts and 100ms period.
Every pulse causes the solenoid to advance the gear by one tooth; a pawl retains the gear from slipping again.
These small rotations drive the gears all through the Globus and lead to a tiny motion of the globe.

The lower driving solenoid powers the Earth rotation.

The decrease driving solenoid powers the Earth rotation.

Because the schematic reveals, the solenoids are managed by two switches which can be closed within the МП (touchdown place) and З (Earth orbit) modes.
The solenoids are powered by means of three pins.
The wiring would not completely make sense to me. If powered by means of pins 2A and 7A, the Earth motor is switched whereas
the orbit motor is at all times powered. But when powered by means of pins 2A and 5B, each motors are switched.
Perhaps pin 7A screens the on/off standing of the Globus.

Schematic diagram of the solenoid wiring.

Schematic diagram of the solenoid wiring.

By powering the solenoids with 1 hertz pulses, we precipitated the Globus to rotate. The movement could be very sluggish (90 minutes for an orbit and sooner or later for the Earth’s rotation), so we tried overclocking it at 10 hertz. This made the movement barely seen; Marc used a time-lapse to hurry it up within the video beneath.

The touchdown location mechanism

The Globus can show the place the spacecraft would land for those who began a re-entry burn now, with an accuracy
of 150 km.
That is computed by projecting the present orbit ahead for a specific distance, specified as an angle.
The cosmonaut specifies this worth with the touchdown angle knob (details).
Rotating the globe to this new place is tougher than you may anticipate, utilizing a motor, restrict switches, and the
majority of the electronics within the Globus.

The landing angle control.

The touchdown angle management.

The touchdown angle knob pivots the angle restrict change, proven beneath.
The swing arm strikes because the globe rotates to the touchdown place and
hits the angle restrict change when the touchdown place is reached.
When returning to Earth orbit mode, the swing arm swings again till it hits the fastened restrict change.
Thus, the globe is rotated by the chosen quantity when displaying the touchdown place.

The landing angle function uses a complex mechanism.

The touchdown angle operate makes use of a fancy mechanism.

To regulate the motor, the rotary change reverses the DC motor primarily based on the mode, whereas the restrict switches and energy transistor flip the motor on and off.
In touchdown place mode (МП), the motor spins the globe ahead.
The mode change controls the route of present move: from higher proper, by means of the motor, by means of the angle
restrict change, by means of the transistor, and to floor on the backside.
The motor will rotate the globe and the arm till it hits the “touchdown place” restrict change, chopping energy to the motor and
activating the trail to the sunshine circuit,
which I’ll talk about beneath. The diode prevents present flowing backward by means of the motor to the relay.
The facility transistor apparently acts as a present sink, regulating the present by means of the motor.

Schematic diagram of the landing location mechanism.

Schematic diagram of the touchdown location mechanism.

In Earth orbit mode (З), the motor spins the globe again to its common place.
The mode change reverses the present move by means of the motor: from the upper-left,
by means of the diode and the motor, and out the lower-right to the transistor.
On the backside, the relay completes the circuit till the shifting arm hits the fastened orbit restrict change.
This opens the normally-closed contact, chopping energy to the relay, opening the relay contact, and stopping the motor.

The touchdown place mild

The upper-left nook of the Globus has an electroluminescent mild labeled “Место посадки” (Touchdown place).
This mild illuminates when the globe signifies the touchdown place reasonably than the orbital place.
The sunshine is powered by AC supplied on two exterior pins and is managed by two relays.
One relay is activated by the touchdown circuit described above, when the restrict change closes. The second relay is pushed
by an exterior pin.
I do not know if that is for a “lamp take a look at” or management from an exterior system.

Schematic diagram of the circuitry that controls the electroluminescent light.

Schematic diagram of the circuitry that controls the electroluminescent mild.

See Also

We powered the sunshine with an EL inverter from Adafruit, which produces 100 VAC at 2KHz, maybe.
The spacecraft used a “Static Inverter” to energy the sunshine, however I haven’t got any particulars on it.
The show gives a pleasant blue glow.

The landing position indicator, illuminated.

The touchdown place indicator, illuminated.

The potentiometer

A 360° potentiometer (beneath) converts the spacecraft’s orbital place right into a resistance. Sources point out that
the Globus gives this sign to different items on the spacecraft, however I do not know particularly what
these gadgets are.
The potentiometer seems to linearly observe the spacecraft’s place by means of the orbital cycle.
Observe that this isn’t the identical because the latitude, which oscillates, or the longitude, which is non-linear.

The potentiometer converts the orbital position into a voltage.
To the right is the cam that produces the longitude display. Antarctica is visible on the globe.

The potentiometer converts the orbital place right into a voltage.
To the correct is the cam that produces the longitude show. Antarctica is seen on the globe.

Because the schematic beneath reveals, the potentiometer has a resistor on one leg for some cause.

Schematic diagram of the orbital-position potentiometer.

Schematic diagram of the orbital-position potentiometer.

The exterior connector

To attach the Globus to the remainder of the spacecraft, the again of the Globus has a 32-pin connector, a regular RS32TV Soviet army design.

The back of the Globus, with the connector at the upper left.

The again of the Globus, with the connector on the higher left.

The connector was wired to close by 5-pin and 7-pin terminal strips. Within the schematics, I label these connectors as
“B” and “A” respectively.
Inconveniently, all of the wires to the field’s exterior connector had been lower (the black wires), maybe to decommission the
The pinout of the exterior connector is unknown so we won’t simply reconnect the wires.

A closeup of the back of the connector showing the cut black wires.

A closeup of the again of the connector exhibiting the lower black wires.


By tracing out the wiring of the Globus, I made up my mind its circuitry.
This was tougher than anticipated, for the reason that wiring consists of bundles of equivalent white wires.
Furthermore, many issues undergo the mode change, and its terminals had been inaccessible.
Between the mode change and the restrict switches, there have been many instances to examine.

As soon as I made up my mind the circuitry, we may energy up the Globus. Thus far, we now have powered the solenoids to show
the Globus. We additionally illuminated the touchdown place mild. Lastly, we ran the touchdown place motor.

Observe me on Twitter @kenshirriff or RSS for updates.
I’ve additionally began experimenting with Mastodon lately as @[email protected].
Many due to Marcel for offering the Globus.

Notes and references

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