Ken ShirriffAug 3, 2024
The Space Shuttle had a 59-pound printer on board, known as the Interim Teleprinter. Putting this heavy printer in orbit cost $1.5 million per flight, but it was a key piece of flight hardware,
providing the astronauts with mission plans, weather reports, and other documents from Mission Control. Let's take a look inside... 1/12
Show threadKen ShirriffAug 3, 2024
The Shuttle printer uses a spinning metal drum with raised characters. 80 hammers, one for each column, fire at the exact moments to hit the ribbon and paper against a character on the drum as it spins by. 2/12
Show threadKen ShirriffAug 3, 2024

Here's a closeup of the hammers in action as the Shuttle teleprinter prints a line. 3/12

https://youtu.be/1SjtmePBZjo

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Show threadKen ShirriffAug 3, 2024

The teleprinter design thrown together in just 7 months after a delay in the TDRS satellites meant that the fancier digital printer wouldn't work for the first few flights.

Although the Interim Teleprinter was expected to be used for a short time, it remained in operation for over 50 flights, acting as a backup printer. 4/12

Show threadKen ShirriffAug 3, 2024

The teleprinter was based on a military communications terminal, with many modifications. The keyboard was removed and boards were added to interface with the Shuttle's audio system.

The system still contained a word processor, unusable without the keyboard. 5/12

Show threadKen ShirriffAug 3, 2024
This view inside the teleprinter shows the three custom Shuttle boards (left), the power supply (blue), and the four logic boards (right).
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Show threadKen Shirriff
I reverse-engineered the three custom Shuttle boards to determine the signal format (FSK with 3600 Hz and 7200 Hz).
A digital circuit demodulates the signal using auto-correlation. 7/12
Aug 3, 2024 at 3:09pmWeb
Show threadKen ShirriffAug 3, 2024
The Shuttle teleprinter kept the four logic boards from the military teleprinter: the CPU board, print control board, communication board, and memory board. These implemented a 6800-based microprocessor. 8/12
Show threadKen ShirriffAug 3, 2024
The teleprinter was mounted in a storage locker in the Shuttle middeck, one level below the flight deck. 9/12
Show threadKen ShirriffAug 3, 2024

We managed to get the printer operational. This wasn't easy because the rubber rollers had turned to liquid, gumming up the mechanism. CuriousMarc carefully disassembled the printer, cleaned all the parts, and realigned the hammers. 10/12

https://www.youtube.com/watch?v=EDeL15amsus

Space Shuttle teleprinter printing lines of text

YouTube
Show threadKen ShirriffAug 3, 2024
For details (including schematics), see my blog post https://www.righto.com/2024/08/space-shuttle-interim-teleprinter.html
11/12
Reverse engineering the 59-pound printer onboard the Space Shuttle

The Space Shuttle contained a bulky printer so the astronauts could receive procedures, mission plans, weather reports, crew activity plans,...

Show threadKen ShirriffAug 3, 2024
Credits: printer restoration done with CuriousMarc, @tubetime, and Mike Stewart. Printer provided by Marcel. Shuttle photos from catalog.archives.gov. Locker photo from DMolybdenum, drawing from the military teleprinter manual.
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Show threadValtteri KoskivuoriAug 15, 2024
@kenshirriff @tubetime Wonderful restoration! Tangentially related, I read that the optional copier for the DEC VT52 used electrolysis to print onto damp paper using a helical electrode on a spinning drum. I found drawings and docs, but as far as I can tell, there are no working units that have been demonstrated on video anywhere. Would be really cool to see that in action! Very few terminals seem to have ’add water’ as a regular maintenance item 😄
Show threadWikinautAug 3, 2024

@kenshirriff

I love these boards!

Show threadyou're all idiotsAug 3, 2024

@kenshirriff these old designs are amazing, real time data processing with a hundred hardware actuators all on a ~1 MHz 8-bit CPU, 4K ROM and 4K RAM.

These days you can buy watches with several GHz class CPUs and a couple of gigabytes of RAM.

Show threadWikinautAug 3, 2024

@kenshirriff

I love auto-correlation functions / functionality and used that for certain tasks in the past, too.

Show threadHenning Paul DC4HPAug 3, 2024
@kenshirriff Interesting that they deliberately went for the delay-line approach with harmonic FSK tones. All other contemporary systems (e.g. Bell 202 and V.23) used non-harmonic tones (in order to avoid bit errors due to nonlinear distortion on the line).