[generj]

I am fascinated they used 60 pounds and a large amount of space for this teleprinter. At 30K per pound of payload that is $1.8 million per flight. Really shows how important reliable printed updates were considered.

And all the flaws of the printer that were managed around - turning it off to save power and prevent it overheating with specific tones.

[beerandt]

The thing that immediately jumped into my head is coded military use. Especially since they mention the printer being based on a military design.

It's still rather obscure, if not still secret, just to what extent we were actually using the shuttles in their intended military capacity.

But when designed, the military use was expected to be much much higher than what panned out.

This printer would be high on the list of the weight budget, to the point that I wonder if it wasn't critical protocol to some still secret military use, similar to the teletype nuke codes / orders on a sub.

Running over the audio system also makes me curious if it was strictly unencrypted comms, or if it could plug in to a decrypted steam. Were they clear broadcasting coded messages, or encrypted-broadcast clear messages (or both or neither).

IIRC, NASA used to have at least some 'private' comms with astronauts that were in the clear, but they basically just didn't rebroadcast to the public or publicize those currently used frequencies, and just sort of trusted those in the know not to listen in.

[kens]

As far as cryptography, the military AN-UGC/74 teleprinter worked with cryptographic equipment such as TSEC/KG-30, KG-84, KW-7, and KY-57 [1]. You'd send the data stream into the crypto equipment and then to the teleprinter. However, the modifications for the Space Shuttle would have prevented this. Specifically, the FSK demodulation boards for the Shuttle were wired directly to the communication UART board, so there was no place to plug in the crypto box.

[1] https://radionerds.com/images/e/e0/TM_11-5815-602-24.pdf#pag...

[mandevil]

STS definitely encrypted all comms- voice, data, telemetry, and printer for the classified portions of all missions (that would be STS-51C, STS-51J, STS-27, STS-28, STS-33, STS-36, and STS-38 along with parts of STS-39 and STS-53).

My assumption is that the decryption happened upstream of the teleprinter- the teleprinter was definitely chosen because they thought it would be useful to print things for all missions, not because it provided special encryption for military purposes. When they did classified stuff everything was encrypted.

Basically, printers are really useful. They are heavy and they can break, but are tremendously useful.

[walrus01]

> The thing that immediately jumped into my head is coded military use. Especially since they mention the printer being based on a military design.

a significant portion of the funding for the shuttle came from the USAF, and one of its capabilities (to capture and return a large satellite) was a USAF requirement. They even went as far as building an entire launch pad for it at Vandenberg, which came very close to being used.

[tyingq]

Here's my guess. Government bureaucracy is probably very high for anything space related. So "based on the military's AN/UGC-74" could have helped get it through approvals. It would have ticked a lot of boxes for ruggedized parts, use in harsh environments, and so on.

[beerandt]

I don't doubt that for a second- but I'm more curious about the requirement for some kind of printout in the first place.

Especially since it ultimately ended up weighing what it did.

Military/ Ruggedized is a smart choice for a printer that needs to go through that environment, no matter the why.

I'm more interested in what it tells us about the underlying purpose (or what it might rule out, like the part about wired directly into unencrypted comms).

[jcrawfordor]

I don't think the requirement for printed output requires any appeal to military applications. They would have been exchanging navigation information with mission control over the radio. That's all mission critical and needs to be read back. Anything they got via voice they would have to write down. Getting it by text in the first place would increase reliability and reduce cockpit workload.

You also get in-flight information like weather that you'll want to write down for later reference. Teleprinter writes it for you so you can review it at your leisure.

Airliners and ships at sea have both historically used teleprinters for the same reasons, although the modern navigation computers have mostly eliminated the need.

[tyingq]

Oh, I didn't consider that, since I was a young person then. Sticking notes, directives, etc, everywhere was just really common. So if they get a note about extra daily checks on equipment X, they print/affix the note to the equipment. Or other similar needs. There would probably be limited screens, so anything you wanted to be known to everyone, becomes a note.

[KineticLensman]

> I am fascinated they used 60 pounds and a large amount of space for this teleprinter.

IIRC the Zion space habitat in Neuromancer had a state-of-the-art line printer which at one point spews continuous-fold paper into the weightless environment.

They had however got rid of the slide-rules that were essential in early-era Arthur C Clarke spaceships

[throwanem]

That was Haniwa, not Zion. The printer was spewing paper because someone had put a laser through its faceplate while Corto was taking the ship.

Also, Haniwa is described explicitly and implicitly as an exoatmospheric luxury yacht, and thus likely wasn't designed for high acceleration. Also, I'm pretty sure it was a thermal printer, not a line printer as here. Also, Neuromancer is period-piece literary sf. So I'm not necessarily sure how relevant it is here.

[KineticLensman]

In terms of relevance, I was amused that real and contemporary fictional spacecraft both had paper printers

[lsllc]

The question is, would the craft now need help from reaction wheels to offset the inertia from the moving print head / paper feed? Or would there need to be a special version of the printer firmware that kept track of its movement so it could always impart equal but opposite inertia?

[throwanem]

Since a thermal printer only needs as much pressure on the platen roller as required to keep the paper registered, the roller itself could be hollow and thus carry negligible inertia. The print head could be net neutral by operating boustrophedonically, which many printers already do - both of my inkjets, for example! - and that might actually count for more, considering the possible need for some thermal mass to dissipate waste heat from the printing elements. (I don't think modern thermal printers need that, but I suppose in the 80s they might have.) Worst case, the firmware might need to ensure the number of head passes is even, I think most simply by counting print passes and if needed performing a final "return" pass with a cold head - again a common behavior, and one also displayed by both my inkjets since that avoids the need for a parking station on either side of the paper path.

The line printer with its heavy drum would probably be more of a concern for the Shuttle, although I doubt a significant one. Reaction wheels function by change in angular momentum, and a line printer drum spins at a fixed rate in operation; as long as spinup and spindown take about the same time, which is easy enough to achieve, the net effect on attitude should be negligible, especially considering the entire printer constitutes only about 1/3000 of the orbiter's dry mass.

You might not want to run the thing during an OMS burn, but even if you did I doubt it'd matter; assuming constant thrust from spinup through spindown, your course would be displaced proportionally to the length of the print job, but given the minimal relative inertia and that line printers typically output in the tens of hundreds of lines per second I think it'd need quite a long job to make a noticeable difference, and you'd almost certainly run out of paper long before.

(Don't take any of this too seriously; I'm the wrong kind of engineer to give authoritative answers here, but the question is fun to think about anyway.)

[lsllc]

"boustrophedonically": now there's a word you don't get to use very often (possibly unless you're Indiana Jones). That's got to be worth something in Scrabble!

[throwanem]

Tens to hundreds of lines per minute, not second. Good grief, line printers are scary enough as is, without also feeding paper fast enough to start friction fires...

[eddieroger]

I was pretty stuck by that, too, and it made me wonder if maybe I don't understand or underestimate the value of paper transmission. I suppose if radio communication is good but flaky, or for persistence of instruction, like procedures, then it would be good for them to be able to print. But at such a cost!

[shagie]

Remember that this was also before easily portable electronics.

Today you'd get a PDF and store it on your iPad. Secure it for landing and you're good. All the documents you want.

In the 80s consider the "Mission Control has new landing procedures that you need to follow. Here is a 42 item check list that you'll need to do before initiating task 357 from the mission specification."

How do you get that 42 item check list? Do you write it down? What that transcribed properly? Was that a P or a B that the person heard over the radio? (Yes, I know Bravo Papa).

Here's a secret objective for the mission ( https://ntrs.nasa.gov/api/citations/20110023479/downloads/20... ) to preform while in orbit that has now been approved and was not part of the initial mission profile. The instructions will be printed out and are for the captain and pilots eyes only.

There are a number of reasons that one may need a secure printer to handle new documents while on the Space Shuttle. With 70s and 80s tech, the approach taken is reasonable.

[dylan604]

Maybe they remember the situation with Apollo 13 where they had no way to right down the procedures other than by hand and using space pages from the existing printed documents. You then had the issue where the guys were so fatigued and CO2 levels getting to a point of making vision blurry. I could see where that might have factored into the decision of wanting to avoid all of that with the ability of printing new/modified procedures.

[dylan604]

too late to edit, but right != write <hangsHeadInShame>

[krisoft]

I guess with modern googles one would just pack an "ipad" equivalent tablet. If one worries about accidents and freak space particles disabling it give them 3. If one still worries one can develop a "space rated" tablet. But probably at those radiation levels one should also start worrying about the crew's health.

But of course that is projecting our current capabilities back in time. I looked it up and the "Osborne 1" portable computer[1] was just released 9 days before the shuttle's first flight. It weighed 24.5 lb (11.1 kg) and could display 52 x 24 characters on a small CRT. So yeah, that would not be nice to read manuals with :D

1: https://en.wikipedia.org/wiki/Osborne_1

[generj]

Right it clearly was the best choice for the time the shuttle was developed but just shows how removed from the 1960s and 70s we are today.

My earlier point about payload weight was probably the wrong focus. Mission success and maximizing what the crew can accomplish in orbit are greatly facilitated by one way text from ground control, and doubtlessly paid for the 60 pounds

Astronauts were already used to Telex weather reports as pilots so existing UX. And the crew specialists all had PhDs and thus were experts at reading typed paper. So no training on yet another shuttle subsystem.

The teletype could be effectively shared between crew - just tear off the paper. A portable computer could only be used by one or two people, AND would need to be radiation hardened and aerospace qualified.

[amelius]

iPads are more hazardous than you think:

https://appleinsider.com/articles/23/07/14/fatal-helicopter-...

[kayodelycaon]

Not really an iPad-specific issue. A clipboard or checklist could have done the same thing.

[amelius]

> At 30K per pound of payload that is $1.8 million per flight.

Yeah, but they could save by using white-label ink cartridges.