Ken Shirriff does another dig. And it's really heavy..
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The motivation for the teleprinter goes back to the Apollo program. During Apollo missions, the only way to send information to the astronauts was by talking to them over the radio and having the astronauts write down the data. NASA decided that the Space Shuttle should include a mechanism to send text and images to the astronauts, a 78-pound, high-tech fax machine called the Uplink Text & Graphics System (TAGS). A high-resolution grayscale image was sent to the Shuttle as a digital data stream. Onboard the Shuttle, a squat CRT displayed the image one line at a time and a fiber-optic faceplate transferred each line to light-sensitive silver emulsion paper. The paper was developed by passing it over a hot roller at 260ºF for 25 seconds, creating a permanent image.
The one flaw in this plan was that sending the digital image to the Shuttle required the Tracking and Data Relay Satellite System (TDRS), which due to delays wouldn't be ready until the sixth Shuttle flight. (The TDRS was a space-based replacement for the worldwide network of ground stations that was used during Apollo.) As a result, NASA decided just seven months before the first Shuttle launch that they needed an interim system "for transmission of real-time, flight-plan changes and other operational data to the crew."2
The Shuttle teleprinter is the result of this rushed effort to create a printer that could work over the existing audio channel rather than the digital TDRS satellite. Due to the time pressure, the Shuttle teleprinter needed to be based on an off-the-shelf printer. Thermal and electrostatic printers were rejected due to toxicity and flammability problems. (The Shuttle teleprinter used a roll of yellowish paper, which required a NASA waiver due to its flammability, a concern ever since the Apollo-1 disaster).
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