[HN Gopher] Reverse engineering the 59-pound printer onboard the...
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Reverse engineering the 59-pound printer onboard the Space Shuttle
Author : chmaynard
Score : 154 points
Date : 2024-08-03 16:43 UTC (6 hours ago)
(HTM) web link (www.righto.com)
(TXT) w3m dump (www.righto.com)
| kens wrote:
| Author here if anyone has questions...
| hobo_in_library wrote:
| This is really cool. How did you discover all this information?
| kens wrote:
| I had to go to the Library of Congress to get some of the
| information...
| urda wrote:
| Where else did you get info from that might be,
| unconventional, to readers here?
| ASalazarMX wrote:
| 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.
| kens wrote:
| No radiation hardening. Their main priority was building a
| system in 7 months that meet their toxicity and flammability
| standards. The original military teleprinter weighed 100
| pounds. They cut it down to 59 pounds, so that's a win, I
| guess.
| crazygringo wrote:
| Were commercially available dot-matrix or daisy-wheel
| printers toxic or flammable?
|
| 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?
| colechristensen wrote:
| Vibration is a big deal in space. Launches aren't gentle.
| Think "repeatedly thrown down a flight of stairs"
| toughness is required. And it's a closed atmosphere so
| any amount of outgassing is paid close attention.
| jcrawfordor wrote:
| Most plastics of the era would not meet requirements for
| aviation fire safety, they produce toxic smoke when
| burning (still a significant problem today). There's an
| obvious tension between "reduced weight" and "not using
| plastics," but that was kind of the deal in aviation
| technology at the time. Aviation equipment is still
| pretty chunky today, because of the materials needed for
| low/no smoke evolution and vibration tolerance.
|
| 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.
| shadowpho wrote:
| >Were commercially available dot-matrix or daisy-wheel
| printers toxic or flammable?
|
| 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.
| magnat wrote:
| 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
| jmole wrote:
| it's stopping, like all printers of the era, e.g.
| https://youtu.be/A_vXA058EDY?&t=41
|
| edit: I see now you were asking about the drum, rather than
| the paper
| tim333 wrote:
| It looks like a regular line printer where the drum keeps
| spinning. See wikipedia:
|
| >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
| nyrikki wrote:
| The platen and paper feed stops line for line.
|
| 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:
|
| https://www.youtube.com/watch?v=EDeL15amsus
| zelphirkalt wrote:
| 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.
| slater wrote:
| Works for me? macOS, Firefox
| zelphirkalt wrote:
| The div with class cap-top is defined with a height of
| 400px and seems to overlap with the text. That seems to be
| the issue. I don't know what that div is actually for or
| why it needs to be 400px high, or why its position must be
| absolute or why it is 100% wide.
| eichin wrote:
| 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?
| cbhl wrote:
| I think the paper gets sandwiched between the hammer on one
| side and the drum on the other side.
|
| This would be not too dissimilar to how a typewriter would
| have worked, I think?
| dTal wrote:
| >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.
| metadat wrote:
| 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.
| jdlshore wrote:
| There's 80 hammers, one for each character. They're small.
| metadat wrote:
| But only 1 drum, which is a cylinder with a flat printing
| profile.
|
| Imagine if you want to hammer a single nail, but with a
| steel beam in between: Hammer strikes here
| v ============= Steel beam | | | | | | |
| ~~~~~~~~~~~~~~ wood
|
| How does the second nail not get pushed in a little, too?
| Pinus wrote:
| Now I want to see a print sample! =)
| johnklos wrote:
| 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 :)
| ASalazarMX wrote:
| Wonder if it's as incredibly noisy as a regular dot-matrix
| printer. In the video it sounds almost pleasant.
| kens wrote:
| It's loud enough that NASA put acoustic down in the locker
| for the printer. But it's not screeching like dot matrix.
| beardyw wrote:
| I worked with line printers for many years and they were as
| noisy as hell. Pretty fast though.
| SoftTalker wrote:
| I'm pretty sure we had commercial/consumer dot-matrix printers in
| 1981. Something like that would have been much lighter and lower-
| power than a drum line printer.
| treyd wrote:
| But would it have worked after the intense vibrations and
| acceleration of launch and in zero gravity?
| cyberax wrote:
| Why wouldn't it? Matrix printers are extremely robust.
| lysace wrote:
| Weren't they primarily Japan-made at the time? (I imagine that
| could present a political problem.)
| darreninthenet wrote:
| Centronics (American...) built the first "true" dot matrix in
| 1970 although IBM built a line printer that was similar in
| the late 50s
| lysace wrote:
| Ah. That's where the name of that giant connector came
| from.
| jcrawfordor wrote:
| Probably not a concern in federal acquisition, but it's an
| interesting point that Centronics pretty much only built
| the print head and control electronics. The rest was built
| by Brother in Japan, as a modification of their electronic
| typewriter mechanism. Printing really was a very Japan-
| dominated industry at the 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.
| metabagel wrote:
| 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.
| Mistletoe wrote:
| 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
| jonathaneunice wrote:
| 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.
| cyberax wrote:
| I wonder why they didn't use a matrix printer.
|
| Or even a thermal printer. Fax machines were ubiquitous at that
| time.
| kens wrote:
| NASA had toxicity and flammability constraints that limited
| what they could use.
| annoyingnoob wrote:
| Mechanical parts likely still work, does not need an ink
| subscription.
| gexla wrote:
| Office-space.
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