Reverse engineering the 59-pound printer onboard the Space Shuttle

often printing thousands of lines per flight

with a Shuttle flight costing $27,000 per pound, putting the 59-pound teleprinter in space cost over $1.5 million per flight.

That budget calculation is just the weight of the printer itself. I am curious how much blank paper was flown to feed it, and how this was decided? From the font size shown in photo we can assume it was at least several more pounds of paper for "thousands of lines" to be true.

Was this printer radiation-hardened? As others have pointed out, a commercial dot-matrix printer would have saved many valuable kilos of weight. There must have been other priorities besides weight.

How does a hammer strike cause only one character to be printed? For example, striking the leftmost hammer not also causing the neighboring character to also be printed.

Is the drum rotating smoothly at constant RPM, or is it stopping briefly (using gears [1] similar to those found in analog movie projector) when hammers hit the paper to prevent them from tearing it?

[1] https://en.wikipedia.org/wiki/Geneva_drive

This is really cool. How did you discover all this information?

How much does the paper move when the hammer hits it? even with the padding of the ribbon (and having seen the video clips of it in action - ps. would love to see high-speed closeups if you get a chance) I'm not sure why the paper doesn't tear when the hammer hits it - or if it's a very short distance, does it instead smudge?

Why do you make it impossible to highlight text on the website?

EDIT: Apparently not the whole text cannot be highlighted, but only the initial lines of text.

and a ROM that holds its program code

Did you manage to dump the ROMs? (I understand from your article that article there are 3, a 4KB ROM on the CPU card, and two 8KB ROMs on the word processor card)

Greetings Ken. Thanks to you and Marc for another great dive into obscure NASA hardware.

They must have considered that the spinning drum had a gyroscopic effect on the shuttle. One of the reasons why the shuttle computers used tape drives and not hard drives was because they would have affected it's attitude in microgravity. Perhaps there wasn't enough mass there to be a problem, and also that it wasn't spinning 100% of the time like hard drives would have been?

I'm also surprised they didn't consider the Teletype Model 40. It was lighter, didn't have a spinning drum, came in a receive-only configuration (no need to hack off the keyboard), was ASCII-based, and was already flight qualified on military aircraft. Maybe my timing is off - I first saw one in 1984 and it was considered "new" then, so it might not have been available in 1981.

The Model 40 used a rotating belt with individual character pallets in it. It also used 80 hammers that would fire at the correct time to produce a printed character. You can see the pulleys for the belt spinning (one is behind the red plastic part on the left) in the video. It would also power down after a period of inactivity. One of the jokes you could play was to swap pallets around. They weren't tracked individually, but the belt had a flag that would indicate the start of the pallet sequence. So any monkey-business afterwards would result in M's for N's etc. being printed.

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

Weren't they primarily Japan-made at the time? (I imagine that could present a political problem.)

But would it have worked after the intense vibrations and acceleration of launch and in zero gravity?

In 1981, maybe, but there's a long time lag between design and flight for spacecraft. Cheap/light/sturdy dot matrix printers weren't yet available in the 1970s when the Shuttle was being designed. Nor had the idea of using commercial/off-the-shelf (COTS) components yet taken root. That would come years after the STS was already built and in service.

And imagine how cool that matrix printer sound would be ringing out against the walls of the shuttle in space. Cyberpunk as hell. I miss dot matrix printers so much.

https://youtube.com/watch?v=A_vXA058EDY

https://news.ycombinator.com/item?id=39769157

And when shuttle was developed, printers barely existed. Both inkjet and laser desktop printers were introduced commercially 1-3 years before the shuttles first flight in 1981, and weren’t very reliable yet. Desktop printers still aren’t as reliable as a teletype or dot matrix printer. There’s a reason airlines use dot matrix for printing flight manifests at the gate.

Ink plotters, teleprinters, and fax machines ruled the world. But plotters are dreadfully slow at writing text. Radio fax machines may have been viable if they were rugged enough. But they probably weighed as much as the teletype and were much slower - only real advantage is printing diagrams and photos.

Author font family: normal normal 14px Arial, Tahoma, Helvetica, FreeSans, sans-serif;

News YC font-family: Verdana, Geneva, sans-serif;

Per https://unicode.scarfboy.com/ these are the characters (formatting issues are expected):

U+03B8 θ GREEK SMALL LETTER THETA

U+2713 CHECK MARK

U+203E ‾ OVERLINE

U+2191 ↑ UPWARDS ARROW

U+2193 ↓ DOWNWARDS ARROW

U+007E ~ TILDE

U+03B1 α GREEK SMALL LETTER ALPHA

U+03B2 β GREEK SMALL LETTER BETA

U+0394 Δ GREEK CAPITAL LETTER DELTA

U+03D5 ϕ GREEK PHI SYMBOL

Specific characters that aren't showing up:

U+2713 CHECK MARK, U+203E ‾ OVERLINE, U+2191 ↑ UPWARDS ARROW, U+2193 ↓ DOWNWARDS ARROW, U+03D5 ϕ GREEK PHI SYMBOL

Arial contains most of these, Verdana does not. That's the limit of my knowledge of webified things.

Somewhere between when this was originally written and when it was delivered to your browser the text here was destroyed.

I don't see how that's the fault of Chrome or Android.

It looks like the <code> tag is the problem. I guess the Android Chrome code font doesn't include those special characters. I took out the <code> tag and now the characters render on Android (at least for me).

Oddly enough, Chrome on my Samsung S24 Ultra renders them OK here on HN, but not on Ken's page. Chrome on Windows and Ubuntu and Safari on iOS are the opposite: OK on the page, not here.

Character encoding is such fun!

Update: Ken, if you see this, it's specifically the characters encoded with numeric entities that have the problem on my devices. I used the Chrome dev tools to replace these with the actual characters on my Windows and Ubuntu devices and they rendered OK.

There's a short video of the printer printing towards the bottom of the article. You can see the printing in that.

On the other hand, a Snoopy calendar printed on that would be cool :)

NASA had toxicity and flammability constraints that limited what they could use.

It’s in the article.

Mechanical parts likely still work

Towards the end of this article, Ken says that the mechanical parts did not work:

"The printer had many mechanical problems, mainly because the rubber rollers had turned to liquid and gummed up the mechanism."

We had to get printouts from the mainframe for my freshman CS class and they came out of a chain printer. It was in the next room separated by a set of cubbyholes for the printouts and it sounded terrifying when it was printing, even 20 feet away.