[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.