
Diskee: Apollo's Most Important Crewmember - empressplay
https://paleotronic.com/2019/01/22/the-diskee-apollos-most-important-crewmember/
======
joezydeco
The DSKY was a _demo_.

“The DSKY and PINBALL (something flashy with buttons) was a demo. And that
demo got us to the moon. "Apparently, nobody had yet arrived at any kind of
software requirements for the AGC's user interface when the desire arose
within the Instrumentation Laboratory to set up a demo guidance-computer unit
with which to impress visitors to the lab. Of course, this demo would have to
do something, if it was going to be at all impressive, and to do something it
would need some software. In short order, some of the coders threw together a
demo program, inventing and using the verb/noun user-interface concept, but
without any idea that the verb/noun concept would somehow survive into the
flight software. As time passed, and more and more people became familiar with
the demo, nobody got around to inventing an improvement for the user
interface, so the coders simply built it into the flight software without any
specific requirements to do so."

[http://www.ibiblio.org/apollo/ForDummies.html](http://www.ibiblio.org/apollo/ForDummies.html)

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btown
It's funny that the personified user interface is used as the title, because
the star of the show is something much more hidden - one of the first
multitasking "operating systems" correctly handling, and limiting the impact
of, an unforeseen CPU-hungry process in the midst of the first moon landing!
The OP's a fascinating read and more technical than the title might imply.

For anyone interested in the process of compiling and loading the code for
these systems (available at
[https://github.com/chrislgarry/Apollo-11/](https://github.com/chrislgarry/Apollo-11/)
) into the "core rope memory" used for program storage in the capsules, here's
one of the original spec documents, as well as an image from that document
showing what I'd call a "compilation-bureaucracy-pipeline" that's a
fascinating glimpse into software deployment practices.

[https://www.ibiblio.org/apollo/Documents/HSI-208496.pdf](https://www.ibiblio.org/apollo/Documents/HSI-208496.pdf)

[https://imgur.com/a/wBYt1o6](https://imgur.com/a/wBYt1o6)

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Someone
_”the DSKY (which they pronounced Diskee), a simple LED and button-based
interface”_

Wikipedia says there were visible-light LEDs in 1962
([https://en.wikipedia.org/wiki/Light-
emitting_diode#Discoveri...](https://en.wikipedia.org/wiki/Light-
emitting_diode#Discoveries_and_early_devices)), but even ignoring they emitted
red light, which the photos do not show, I think it’s unlikely they used them
in this device.

[https://en.wikipedia.org/wiki/Apollo_Guidance_Computer#DSKY_...](https://en.wikipedia.org/wiki/Apollo_Guidance_Computer#DSKY_interface)
claims it used _”green high-voltage electroluminescent seven-segment
displays”_. That seems more likely to me.

~~~
joezydeco
They were indeed EL displays.

Fran Blanche attempted a GoFundMe project to recreate these displays.
Unfortunately the project stalled.

[https://www.gofundme.com/apollo-dsky-display-
project](https://www.gofundme.com/apollo-dsky-display-project)

[https://hackaday.com/2017/05/29/re-creating-the-apollo-
dskys...](https://hackaday.com/2017/05/29/re-creating-the-apollo-dskys-
display/)

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lcuff
This article makes it seem more dramatic and spur-of-the-moment than other
writings on the same topic I've read. The Wikipedia article on Jack Garman
asserts (unsourced) that they'd generated a 1202 alarm in simulations and
Bales had (incorrectly) called for an abort there. So it was actually a
rehearsed scenario, with an analyzed "should go anyway" decision.

~~~
ekimekim
I read the same thing in Gene Kranz's book Failure Is Not An Option - it
should probably be added there as a reference.

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troutwine
If you're interested in the Apollo Guidance Computer there's some really
excellent material out there in the world to learn more. My two favorite books
are:

* The Apollo Guidance Computer: Architecture and Operation - Frank O'Brien

* Digital Apollo: Human and Machine in Spaceflight - David A. Mindell

Fascinating machine.

~~~
kens
I recommend Journey to the Moon by Eldon Hall, designer of the AGC. The
O'Brien book has a lot of good information but also a lot of problems.
Sunburst and Luminary is also interesting, written by Don Eyles who wrote much
of the lunar landing code. He goes into a detailed explanation of the 1202
program alarms.

~~~
1201alarm
Eyles came to the Vintage Computer Festival-East in Wall, NJ last year, and
was introduced by Frank O'Brien who's a regular there. He actually did a code
walkthrough of the Apollo 14 flaky-switch hack - coolest talk I've ever
attended. Scott Manley did a pretty good Youtube episode on the Apollo 14 hack
last year also; the two of them complement each other nicely.

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foofoo55
Excellent 1960's video demonstrating the AGC, which gives an indication of the
thought processes and design rigor that were going on:

[https://www.youtube.com/watch?v=F6S-mmunKuo](https://www.youtube.com/watch?v=F6S-mmunKuo)

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ForHackernews
The AGC source code is up on Github these days
[https://github.com/chrislgarry/Apollo-11/](https://github.com/chrislgarry/Apollo-11/)

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andoma
Ongoing effort of restoring an AGC

First episode:
[https://www.youtube.com/watch?v=2KSahAoOLdU](https://www.youtube.com/watch?v=2KSahAoOLdU)

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garaetjjte
More technically accurate description:
[https://www.doneyles.com/LM/Tales.html](https://www.doneyles.com/LM/Tales.html)

It describes that not just DELTAH was killed due to overload, but that whole
system restarted (and reloaded critical landing tasks that were restart-
protected)

------
jgalt212
The DSKY gets a fair amount of air time in Nova's recent episode on Apollo 8.
Well worth a watch.

[https://www.pbs.org/wgbh/nova/video/apollos-daring-
mission/](https://www.pbs.org/wgbh/nova/video/apollos-daring-mission/)

