Reverse engineering the 59-pound printer onboard the Space Shuttle
righto.com
righto.com
Specifically, the characters ;@[\]^!"#$ are replaced by θ~αβΔ.
Sigh... This ancient printer could render them, but apparently the Chrome browser on my modern Android cannot.
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.
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.
I don't see how that's the fault of Chrome or Android.
>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.
Some quick searching indicates that yellow is easier on the eyes than pure white (that is given as the reason legal pads are yellow). Or that different wire services would use different color paper. E.g. news wires used white paper, weather services used yellow. So news editors would know the source by the color of the paper.
I think what OP was asking is - given shuttle already had a mission with some spare payload capacity, how much did it cost to bring one more pound into space? I think this question has a relevancy to the fact the printer was surprisingly heavy and came with a lot of paper. I'm not sure if there's a good way to calculate this though.
Thus even if there is capacity limits there may be reasons for loading less mass to reduce cost of a mission.
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.
the drum or similarly the chains used on the hammer printers were in constant motion.
I am just old enough that I had to repair both types at the beginning of my career. Although typically rebranded Data Products and other OEMs, which I am probably wrong but vaguely remember being a supplier for the DEC L20?(maybe). But different than this printer.
To these hammer action printer, the ribbon and the paper weren't even a consideration.
If you have a Newton's cradle, put a piece of paper between the inner balls and it will still mostly work if you release a single ball.
The high speed drum printers they typically had to rotate twice for each line (at minimum) so a 600lpm printer would have the drum rotating at about 1200rpm.
If you look at the video posted in another comment, you can see the ragged vertical alignment of the chars. IIRC that is why IBM preferred chains in their hammer printers, because the human eye was more forgiving of vertical misalignment compared to the vertical misalignment that was a natural result of the mechanical differences.
Edited to add link to video from page:
> the human eye was more forgiving of vertical misalignment
>Because the drum carrying the letterforms (characters) remains in constant motion, the strike-and-retreat action of the hammers has to be very fast. https://en.wikipedia.org/wiki/Line_printer
edit: I see now you were asking about the drum, rather than the paper
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)
One thought occurs: I assume these are mask ROMs, and so likely unchanged from the AN/UGC-74 original. So, if someone somehow managed to get their hands on an AN/UGC-74, you'd feel less bad about engaging in this kind of "sacrificial" action, given it would lack the unique historical association with Space Shuttle.
Another thought: maybe there is some way to monitor the signals on the ROM pins non-destructively, by picking up the electromagnetic radiation? I'm guessing the answer is "no", at least not in practice.
P.S. You have a typo on the page, at one point you have "AN/UCG-74" instead of the correct "AN/UGC-74". The other three times you mention it, you have it written correctly.
My initial thought was also that this was for radiation hardening.
But if not, I still don't understand at all why they didn't buy something lighter and cheaper off the shelf. Do you know specifically what component(s) didn't meet the toxicity and flammability requirements? And why any specific components like that couldn't just be swapped out, rather than redesigning the entire thing?
Considering it probably also had to meet a MIL-STD environmental spec, stripping a commercial printer and putting it in some kind of aftermarket metal chassis seems like a much more expensive/higher risk route than using something that was already made to those standards.
Environmental specs, in this context, usually mean min and max operating temperatures and acceptance of vibration and shock, within certain G-force and frequency measurements, with "without malfunction" and "without damage" thresholds. Aviation and military equipment have to go to environmental testing laboratories to be certified to these requirements, which can be a considerable expense on its own, and another reason it's smart to use an existing design.
Besides, the military already made use of teleprinters in aircraft and so there was operating experience to build confidence. The space shuttle model is based on the family made by MITE, which included airborne variants used on bombers for example.
Never thought of this before, but rocket launches are quite the event.
Doing a quick search, see perhaps ISO 10816:
* https://acoem.us/blog/other-topics/understanding-the-iso-108...
Amongst others:
* https://vibrationresearch.com/blog/understanding-nasa-std-70...
* https://vibrationresearch.com/testing-standards/
* https://www.avmc.army.mil/Portals/51/Documents/TechData%20PD...
It’s not a binary but spectrum. For example military has a long list of standards for wires. The ships/tanks/planes use different wiring than your house does. That doesn’t mean our wires are toxic and flammable but they are probably more toxic/flammable than the application calls for.
And here is the problem: there was no off the shelf printer that met their exact requirements on paper. It’s possible some of the printers were similar quality but they were not certified to same standard.
So NASA would call a printer company and ask “does your printer self extinguish? What about in 100% oxygen? What about inrush current? Does the motor stall and what are the protections?”.
The printer company would not want to spend the time/energy on that vs what nasa would be willing to pay for 5-10 printers.
Epson did a bit more than a decade later.
This became an issue on STS-27 where they were unable to inspect tile damage with high resolution imaging because of these limitations. The astronauts on this mission were not at all pleased with the situation, and they had good reason not to be, as an entire tile had become dislodged by foam during the ascent.
This would be not too dissimilar to how a typewriter would have worked, I think?
Imagine if you want to hammer a single nail, but with a steel beam in between:
Hammer strikes here
v
============= Steel beam
| | | | | | |
~~~~~~~~~~~~~~ wood
Intuitively I thought the hammer was striking the back of the drum.. but now I see how that Won't Work.
The print ribbon is simply drier than you are imagining.
EDIT: Apparently not the whole text cannot be highlighted, but only the initial lines of text.
The reason why they probably didn't choose a chain printer for the shuttle is likely because they had a failure mode where if the chain broke it would tend to fly out one side of the printer and through the wall - our operators were cautioned not to stand beside it ....
This was especially 'funny' on Sunday nights, when printed programs for courses were due before class on Mondays.
> 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.
Not sure what part of a dot-matrix required gravity to work; the tractor feeds for the paper (if they used that sort), and nothing in the print mechanism requires a "down" other than possibly paper "exhaust" collection?
While the sound of a dot matrix printer can be kind of therapeutic - I remember debugging by printing, where the sound of printing and the time waiting could be used to mentally debug the problem, so you almost knew where the bug was without even looking at the print out, a line printer is the complete opposite as it's so loud it's distracting and the output gets spat out so quickly you don't have much, if any thinking time!
Brother's relationship with Centronics fell apart pretty much one model later, and now Brother is the printer company and Centronics is long gone.
An Wang was one of the inventors of core memory (it's complicated). He sold his core memory patent to IBM and used the money to create Wang Laboratories, eventually becoming a billionaire.
Or even a thermal printer. Fax machines were ubiquitous at that time.
On the other hand, a Snoopy calendar printed on that would be cool :)
!: "We obtained access to a Shuttle teleprinter (probably a development system that remained on the ground)"
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."