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Tip revision: a8fa8f03b50a72034009439908f1339f4ce94518 authored by Ron Burkey on 06 June 2021, 12:28:21 UTC
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<h2>This Project</h2>
<a href="AGC%20Software%20Landscape.png"><img
src="AGC%20Software%20Landscape-small.png" title="Click to
enlarge" alt="" width="211" height="326" border="2"
align="right"></a>The purpose of this project is to provide
computer simulations of the onboard guidance computers used in the
Apollo Program's lunar missions — but <i>primarily</i> the Apollo
Guidance Computer (AGC) used in the Command Module and the Lunar
Module —, and to generally allow you to learn about these guidance
computers. Since the resources available in this project have
ballooned so much over the years, exploring it for the first time
can be quite intimidating. We invite you to look at our <a
href="ForDummies.html">"kinder and gentler" introductory page</a>
before immersing yourself in the full, gory detail presented by the
bulk of the website. <br>
<br>
Also, if you have some specific interests and don't want to wade
through a bunch of stuff unrelated to them, the search bar at the
top of this page might help. This quick cheat sheet might help
too:<br>
<ul>
<li>If you're interested in the Apollo Guidance Computer (AGC) ...</li>
<ul>
<li>We have the original AGC software, in lots of different
versions, including Apollo 8, 11, and 17, transcribed into
source code, both <a href="Colossus.html">for the Command
Module</a> and <a href="Luminary.html">for the Lunar Module</a>.
The goal is to eventually have these at least for every
mission. The image to the right (click to enlarge) is
our roadmap for getting there.<a href="Luminary.html"><br>
</a></li>
<li><a href="yaAGC.html">We have simulation software that can
run that original AGC software on your computer in real time</a>
(and <a href="yaDSKY.html">can simulate its display/keyboard
unit</a>)<a href="yaAGC.html"><br>
</a></li>
<li><a href="ElectroMechanical.html">We have electrical
schematics and mechanical drawings for the AGC, and for
other components of the Guidance and Navigation (G&N)
system, often transcribed into CAD<br>
</a></li>
<li><a href="Verilog.html">We can run Verilog digital
simulations of the AGC electronics, for detailed inspection
of how all its signals behave</a></li>
<li><a href="links.html">And we have lots and lots of Apollo-era
documentation about the AGC from MIT's Instrumentation Lab,
NASA, and others</a><br>
</li>
</ul>
<li>If you're interested other flight computers used in the Apollo
Program ...</li>
<ul>
<li><a href="yaAGS.html">For the Lunar Module's Abort Guidance
System (AGS) computer, we have its original software, and
simulation software for running that AGS software on your
computer<br>
</a></li>
<li><a href="LVDC.html">We have lots of documentation about the
Saturn rocket's guidance computer (LVDC) ... but none of its
original software<br>
</a></li>
</ul>
<li><a href="https://sourceforge.net/projects/nassp/">We can fly
realistic simulated Apollo missions using real AGC/AGS
software</a></li>
<li><a href="Pultorak.html">We can build our own physical AGC/DSKY</a><br>
</li>
<li><a href="Gemini.html">We have documentation about the Gemini
flight computer (OBC) ... but none of its original software</a></li>
<li><a href="ElectroMechanical.html#LEM_Engineering_Drawings">We
are beginning to have lots of Grumman's Lunar Module
engineering drawings (not just the computer-related ones), and
hopefully will eventually have essentially all of them</a><br>
</li>
<li>We do <i>not</i> have anything at all about Mercury or the
Shuttle.<br>
</li>
</ul>
<br>
<br>
<div align="center"> <iframe
src="https://www.youtube.com/embed/hyhI85Rd1kI"
allowfullscreen="" width="854" height="480" frameborder="0"></iframe></div>
<br>
The video clip above (courtesy of user Dean Koska and YouTube)
illustrates some of the cute things you can do with Virtual AGC if
you're of a mind to do so. Dean compiled our <a
href="yaAGC.html">simulated AGC CPU</a> to run on a Palm
Centro—explaining that a regular Palm was too slow. He created
his own simulated display/keypad ( <a href="yaDSKY.html">DSKY</a>),
presumably aided by the <a href="developer.html">developer info</a>
we provide for just such a desire. (And sorry, Dean's Palm
port isn't provided from our <a href="download.html">downloads page</a>.)<br>
<br>
Here are some other video clips (courtesy of Niklas Beug and
YouTube) which take a little longer to watch (20 minutes), but are
perhaps even more instructive. <a href="yaAGC.html">Our
simulated AGC software</a> has been integrated into <a
href="https://github.com/dseagrav/NASSP/tree/master">the NASSP
add-on</a> for <a href="http://orbit.medphys.ucl.ac.uk/">the
Orbiter space-flight simulator</a>, and is used there to fly
simulated Apollo or Apollo-like missions. And you can fly such
simulated missions too, using that software, as if you were
Neil Armstrong yourself ... assuming you're up the challenge!
The videos below show simulated Apollo 11 and 15 lunar landings,
using our AGC and the actual original Apollo 11 and Apollo 15
guidance-computer software running on it. Of course, all the
fancy graphics is NASSP/Orbiter's and not ours, but the AGC is
behind the scenes, helping to run the spacecraft, and the
accompanying text describes how the AGC is being used! The
Apollo 15 video is quite exciting, as the LM swoops in over the
Lunar Apennine Mountains to the landing site in Hadley Rille.
(I suppose I should also mention that Nik provided these videos in
full HD Quality, though you'll only see a much-reduced quality in
the tiny boxes below, so you might want to head over to YouTube
itself to watch them, if you want to get the full glory of the
things.)<br>
<br>
<table width="100%" cellspacing="2" cellpadding="2">
<tbody>
<tr>
<td valign="top">
<center> <iframe
src="https://www.youtube.com/embed/sHaS6sYJsMg?feature=player_detailpage"
allowfullscreen="" width="640" height="360"
frameborder="0"></iframe> </center>
<br>
</td>
<td valign="top">
<center><iframe
src="https://www.youtube.com/embed/E301HplyA7A"
allowfullscreen="" width="640" height="360"
frameborder="0">&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;br&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;
</iframe></center>
</td>
</tr>
</tbody>
</table>
<br>
<h2>Contents</h2>
<ul>
<li><a href="index.html#What_Is_An_AGC_">What are the "AGC",
"AGS", and "LVDC"?</a></li>
<li><a href="index.html#What_Virtual_AGC_Is">What "Virtual AGC" is</a></li>
<li><a href="index.html#What_Virtual_AGC_Is_Not">What Virtual AGC
is not</a></li>
<li><a href="index.html#Principal_Elements_of_Virtual_AGC_">Existing
Elements
of the Virtual AGC Project<br>
</a></li>
<li><a href="index.html#Licensing">Licensing</a></li>
<li><a href="index.html#What_If_You_Want_To_Help">What if You Want
to Help?</a></li>
<li><a href="index.html#Running_the_Emulator">Running the Emulator
... or, A Brief Introduction to the GUI</a><br>
</li>
<li><a href="index.html#Quick_Start">Quick Start</a></li>
<ul>
<li><a href="index.html#Running_the_Validation_Suite_">Running
the Validation Suite</a></li>
<li><a href="index.html#Playing_with_Colossus_">Playing with
Colossus</a></li>
<li><a href="index.html#Playing_with_Luminary_">Playing with
Luminary</a></li>
<li><a href="index.html#Much_more_intensive_playing_with_the_LM">Much
more
intensive playing with the LM</a></li>
<li><a href="#Canned_pre-recorded_mission_segments">Canned,
pre-recorded mission segments</a><br>
</li>
<li><a href="index.html#Playing_with_the_Abort_Guidance_System_">Playing
with
the Abort Guidance System</a><br>
</li>
<li><a href="index.html#Playing_with_AGC_assembly_language_">Playing
with
AGC assembly language</a></li>
<li><a href="index.html#Modifying_the_LM">Modifying the LM
software (for the truly brave)</a></li>
<li><a href="index.html#Final_exam_for_the_advanced_student_">Final
exam
(for the advanced student)</a></li>
<li><a href="index.html#..._Or_for_the_silly_mood_">... Or, for
the silly mood</a></li>
<li><a href="index.html#..._Or_for_the_even_sillier_mood_">...
Or, for the even sillier mood</a><br>
</li>
</ul>
<li><a href="index.html#Acknowledgements">Acknowledgements</a></li>
</ul>
<h2><a name="What_Is_An_AGC_"></a><small><big>What are "Block I",
"Block II", the "AGC", "AGS", "LVDC", and "OBC"?</big><br>
</small></h2>
"AGC" stands for <span style="font-weight: bold;">A</span>pollo <span
style="font-weight: bold;">G</span>uidance <span
style="font-weight: bold;">C</span>omputer. The AGC was the
principal onboard computer for NASA's Apollo missions, including all
of the lunar landings. Both the Command Module (CM) and the
Lunar Module (LM) had AGCs, so two AGCs were used on most of the
Apollo missions, but with differing software. The
computer and its software were developed at MIT's Instrumentation
Laboratory, now known as Draper Labs.<br>
<br>
The "block II" AGC, employing the AGC4 instruction set, is the
particular computer model in which we're interested, most of the
time. The block II AGC was used not only on Apollo 7 through Apollo
17 (including all actual lunar landings), but also on three Skylab
missions, on the Apollo-Soyuz test mission, and on a <a
href="http://www.klabs.org/history/history_docs/reports/dfbw_tomayko.pdf">fly-by-wire
research project using F-8 aircraft</a>. Nevertheless, only 57
AGCs were constructed—and 138 display-keyboard units (DSKYs) for
them—and all of the ones installed in the Lunar Modules were not
returned to the Earth—so they are definitely collector's items. <br>
<br>
There was also the "block I" model of the AGC, which predated the
block II model. The block I model was supposed to fly in
Apollo 1 and 2. But since Apollo 1 was tragically destroyed by
fire, and Apollo 2 never flew, the block I model was never used in
any manned mission. It was, nevertheless, used in the unmanned
Apollo 3, 4, and 6 missions.<br>
<br>
And of course, don't forget the "block III" model of the AGC, which
... wait just one second there, buddy! Anyone who has done any
reading at all about Apollo, knows there's no such thing as the
block III AGC. Okay, that's true, but one of the original AGC
developers, Hugh Blair-Smith, developed some thoughts in his spare
time about what a block III AGC might look like, and has been kind
enough to send them to us. If you're an advanced student of
the AGC who has already absorbed everything there is to know about
the block II system, <a href="BlockIII.html">you might be
interested in reading what Hugh has to say about it</a>.<br>
<br>
"AGS" stands for <span style="font-weight: bold;">A</span>bort <span
style="font-weight: bold;">G</span>uidance <span
style="font-weight: bold;">S</span>ystem, of which the computer
portion was known as the Abort Electronics Assembly (AEA). The
AGS/AEA was a completely separate computer system from the AGC, with
a different architecture, different instruction-set, different
runtime software, and designed/manufactured by different groups than
the AGC. It was in the LM as a kind of backup for the AGC, but
was only supposed to be used (as the name implies) in case of an
aborted landing. It's sole purpose was to get the LM from
wherever it was back into lunar orbit, so that the CM could
rendezvous with the LM.<br>
<br>
The "LVDC" ( <span style="font-weight: bold;">L</span>aunch <span
style="font-weight: bold;">V</span>ehicle <span
style="font-weight: bold;">D</span>igital <span
style="font-weight: bold;">C</span>omputer) had yet a different
architecture, instruction set, software, and manufacturer. It
was a computer mounted in the Saturn rocket itself, and its
responsibility was to control the firing of the rocket engines to
give the rocket the proper trajectory. It was discarded when
the CSM discarded the rocket, and consequently was used during only
a very short time interval relative to the total length of the
mission.<br>
<br>
The Gemini spacecraft also had an <b>O</b>n <b>B</b>oard <b>C</b>omputer
(OBC), having a similar functionality to the Apollo AGC, though with
greatly reduced capabilities and sophistication, but with a computer
architecture very similar to the Apollo LVDC.<br>
<br>
Because we have much more information about the AGC than we do about
the AGS, LVDC, and OBC, the bulk of this website and of the
Virtual AGC project in general concentrates on the AGC.
Coverage of the other computers is mostly confined to the <a
href="yaAGS.html">AGS page</a>, <a href="LVDC.html">LVDC page</a>,
and the <a href="Gemini.html">Gemini</a> <a href="Gemini.html">page</a>
of this website. And similarly, there is much more discussion
of the block II AGC than of the block I AGC.<br>
<h2><a name="What_Virtual_AGC_Is"></a>What "Virtual AGC" Is</h2>
<i>Virtual AGC</i> is a computer model of the AGC. It does not
try to mimic the <span style="font-style: italic;">superficial</span>
behavioral characteristics of the AGC, but rather to model the AGC's
<i>inner workings</i>. The result is a computer model of the
AGC which is itself capable of executing the original Apollo
software on (for example) a desktop PC. In computer terms,
Virtual AGC is an <span style="font-style: italic;">emulator</span>.
Virtual
AGC also provides an emulated AGS and (in the planning stages) an
emulated LVDC and OBC. "Virtual AGC" is a catch-all term that
comprises all of these.<br>
<br>
The current version of the Virtual AGC software has been designed to
work in Linux (including Raspberry Pi), in Microsoft Windows, and in
Mac OS X. It also works in at least some versions of
FreeBSD. <br>
<h2><a name="What_Virtual_AGC_Is_Not"></a>What Virtual AGC Is Not</h2>
In and of itself, Virtual AGC is not a full-fledged flight
simulator, nor a lunar-lander simulator, nor even a behavioral
simulation of the Apollo Lunar Module (LM) or Command-Module (CM)
control panels. (In other words, if download and run our
software and expect a realistic LM control panel to suddenly appear
on your computer screen, you'll be disappointed.) Virtual AGC
can be used, however, as a <span style="font-style: italic;">component</span>
of such a simulated spacecraft, and developers of such software are
encouraged to do so. Indeed, some developers already have, and
you may have seen a sample video near the top of this page of such a
simulation in operation! In particular, there is full support
for our AGC and AGS emulations in <a
href="http://orbit.medphys.ucl.ac.uk/">the Orbiter space-flight
simulator</a> with <a
href="https://github.com/dseagrav/NASSP/tree/master">the NASSP
add-on</a>. <br>
<h2><a name="Principal_Elements_of_Virtual_AGC_"></a><small><big>Existing
Elements
of the Virtual AGC Project</big></small></h2>
<p>This isn't exactly an exclusive list, but some of the important
things we provide in the Virtual AGC project proper are listed
below.<br>
</p>
<h3>AGC Elements<br>
</h3>
<ul>
<li><b>yaAGC</b> is an emulation of the AGC CPU. To
function, it requires a LM or CM "core rope" binary (see below).<br>
</li>
<li><b>yaDSKY</b> is a simulation of the Display/Keyboard used in
Apollo. It supplies input to <b>yaAGC</b>, or receives
output from it. The design of the emulator is modular, so
the DSKY simulation may be easily replaced if you don't care for
mine, or if you want to replace it with a complete control-panel
simulation.</li>
<li><span style="font-weight: bold;">LM_Simulator</span> is a
simulation of various other Guidance & Navigation (G&N)
system components, such as the Inertial Measurement Unit (IMU),
an FDAI ball, an alternative simulated DSKY, and a monitor for
the AGC's i/o-channel activity. <br>
</li>
<li><span style="font-weight: bold;">yaTelemetry</span> is a dumb
terminal on which telemetry downlinks from <span
style="font-weight: bold;">yaAGC</span> may be viewed, similar
to the way such telemetry from the AGC was originally viewed by
Mission Control.</li>
<li><span style="font-weight: bold;">yaACA</span> is a program
that emulates the LM's hand-controller (possibly with a
joystick), and to communicate the desired pitch/roll/yaw changes
to <span style="font-weight: bold;">yaAGC</span>.</li>
<li><b>yaYUL</b> is an assembler, capable of converting AGC4
assembly language programs like <b>Luminary</b> or <b>Colossus</b>
(see below) into the binary executable format (a "core rope")
needed by the AGC.</li>
<li><b>Luminary</b> is the name of the original 1960's and 1970's
software used for the Apollo Lunar Modules in the actual
missions. Both binary executable (needed by <span
style="font-weight: bold;">yaAGC</span>) and source code
(needed by <span style="font-weight: bold;">yaYUL</span>) are
provided. We have many, many versions of this software,
for different missions.<br>
</li>
<li><b>Colossus</b> is the name of the original 1960's and 1970's
software used for many (but not all) of the Apollo Command
Modules. As with <span style="font-weight: bold;">Luminary</span>,
both binary and source are provided, and we have many versions
of the software.</li>
<li><span style="font-weight: bold;">Validation</span> is the name
of a newly-created AGC assembly-language program that provides a
validation suite for helping to assure that the implementation
of the virtual CPU is correct.<br>
</li>
<li>We have 1000+ scans of many, many of the original Project
Apollo documents in our document library.</li>
<li>We're making an ongoing effort to provide hardware support
(both electrical and mechanical) for the original AGC and DSKY
designs, and for the Guidance & Navigation (G&N) system
in general:</li>
<ul>
<li>Tens of thousands of scans of the original G&N
electrical and mechanical drawings. <br>
</li>
<li>Many electrically-accurate transcriptions of AGC/DSKY
electrical drawings in a modern CAD (Computer Aided Design)
system.</li>
<li>Translations of into AGC electrical design into the Verilog
for simulation of the AGC electrical circuitry.</li>
<li>(Coming real soon now.) 3D-models created from
AGC/DSKY mechanical design files, for 3D printing.<br>
</li>
</ul>
</ul>
<h3>AGS Elements</h3>
<ul>
<li><span style="font-weight: bold;">yaAGS</span> is an emulation
of the AGS CPU. To function, it requires a binary of one
of the flight programs (see below).</li>
<li><span style="font-weight: bold;">yaDEDA</span> is a simulation
of the AGS user interface.</li>
<li><span style="font-weight: bold;">yaLEMAP</span> is an
assembler for AGS assembly language.</li>
<li>The source code for the AGS flight program, in a couple of
different versions.</li>
<li>AGS scanned documentation, including specification,
programmer's manuals, and so on.</li>
</ul>
<h3>LVDC and Gemini OBC Elements</h3>
<ul>
<li>(Planning only.) <span style="font-weight: bold;">yaLVDC</span>,
an emulation of the LVDC and Gemini OBC CPUs, and various
programs emulating Gemini-spacecraft peripherals.</li>
<li><span style="font-weight: bold;">yaASM</span>, an assembler
for the Apollo LVDC and Gemini OBC assembly language.</li>
<li>Scans of all known existing LVDC and Gemini OBC documentation.</li>
<li>Of course, the missing element here is that we have no
significant access to any true LVDC or Gemini OBC source code,
so having an assembler or simulator for it is of questionable
utility. We hope this situation will change, but that hope
fades with each passing year.<br>
</li>
</ul>
<h3>And to Tie It All together ...</h3>
<ul>
<li><span style="font-weight: bold;">VirtualAGC</span> is a GUI
front-end that ties all of the stuff listed above together into
an "easily" used bundle. (It should be obvious why
"easily" is in quotes here.)</li>
</ul>
<h2><a name="Licensing"></a>Licensing</h2>
In general, software not original to Project Apollo is copyrighted
by the original author, usually Ron Burkey (me!), but is provided to
you as "free software" under the GNU <a href="http://www.fsf.org">General
Public License</a> (GPL), though a few programs have been
explicitly put into the public domain. Software originally
from Project Apollo (such as <b>Luminary</b> and <b>Colossus</b>)
is in the public domain, to the best of my non-lawyer
understanding. Newly-written or revised documentation is being
placed in the public domain.<br>
<br>
Note that if you want to use <b>yaAGC</b> or <b>yaDSKY</b> as
components of a more-complete Apollo simulation, the modularity of
the design allows them to be run as stand-alone programs (whilst
communicating with your own software), and doing so does not force
any particular licensing requirements upon your own code.
However, if you choose instead to <span style="font-style:
italic;">incorporate</span> the code directly into your program or
to link to it, your program will itself need to be licensed under
the GPL unless you feel like negotiating an alternate license with
me.<br>
<br>
By "negotiate", I don't mean I'll charge you any money, but merely
that I want to make sure it would be appropriate to give you an
alternate license. By way of illustrating what I mean, the <span
style="font-weight: bold;">yaAGC</span> source code license
includes a "special exception" as allowed/required by the GPL,
allowing linking to the non-free <span style="font-weight: bold;">Orbiter</span>
spacecraft-simulator SDK libraries, which are free of charge but <i>not</i>
under a GPL-compatible license. And as long as you are making
your program freely available in the same way as <b>Orbiter</b>
does, I would be very inclined to offer you such a special exception
as well ... but you have to talk to me about it, and won't get it
just by imagining it's okay. Refer to the <a
href="developer.html">Developer info</a> page for more detail.<br>
<br>
Of course, you could develop your own AGC simulator if you don't
feel like asking me for a non-GPL license for mine. It's not
as if it's rocket science ... oh, but wait .... <img alt=""
src="smiley.png" width="16" height="16"><br>
<h2><a name="What_If_You_Want_To_Help"></a>What If You Want To Help?</h2>
Check out the <a href="volunteer.html">volunteering page</a>.<br>
<br>
<h2><a name="Running_the_Emulator"></a>Running the Emulator ... or,
A Brief Introduction to the GUI<br>
</h2>
What I'll discuss here is merely how to run the pure Virtual AGC
software as provided directly by this project. If you want to
run a full-up spacecraft simulation like <a
href="http://orbit.medphys.ucl.ac.uk/">Orbiter</a> with <a
href="https://github.com/dseagrav/NASSP/tree/master">the NASSP
add-on</a>, you'll have to look at the NASSP documentation
instead.<br>
<br>
The first step, of course, is to download the Virtual AGC software
and install it or build it for the computer platform you're using,
by following the instructions on the <a href="download.html">download
page</a>. While the Virtual AGC project provides many
different programs that implement bits and pieces of the full
emulation, and which can be run separately if you need to craft the
various options for your own purposes, the only program you normally
need to worry about running is the one that's actually <span
style="font-style: italic;">called</span> <span
style="font-weight: bold;">VirtualAGC</span>. <span
style="font-weight: bold;">VirtualAGC</span> is a GUI front-end
which allows you to choose almost any reasonable set of options
related to the emulation, and then to run all of the emulation
programs needed, in a way that allows those programs to
intercommunicate properly. <br>
<br>
Hopefully, <span style="font-weight: bold;">VirtualAGC</span> is
itself simple enough that it really requires very little explanation
to use, and your troubles will really begin only after the emulation
is actually running! But I'll provide a very brief overview
here. There's also <a href="yaTelemetry.html#VirtualAGC">a
more detailed explanation of <span style="font-weight: bold;">VirtualAGC</span></a>
available for your enjoyment.<br>
<br>
<div style="text-align: center;"> <img alt="Screenshot of
VirtualAGC program." src="Screenshot-VirtualAGC.jpg"
style="border: 2px solid;" width="1147" height="966"><br>
</div>
<br>
The screenshot above (or a reduced-size variation, depending on your
screen size or the command-line options you use) depicts the one and
only window of the <span style="font-weight: bold;">VirtualAGC</span>
program. There are no menus, toolbars, hot-buttons, or other
controls. While a large number of options are presented, you
don't necessarily need to change any of the selected options.
The defaults are as shown, and if you simply click the "Run!" button
at the bottom of the window, the simulation will run, as which point
various simulation windows will pop up. If you change any of
the settings, the program will remember those changes and the
settings you've selected will be the ones that appear the next time
you run <span style="font-weight: bold;">VirtualAGC</span>.
Or,
you could click the "Defaults" button at the bottom of the window to
restore all of the settings to their defaults. There's really
very little reason for a complete newcomer to change any of the
settings, but you will note that you can choose from among the
several available sets of AGC software for different Apollo missions
in the pane labeled "Simulation Type."<br>
<br>
When the simulation runs, <span style="font-weight: bold;">VirtualAGC</span>'s
rather
large window will courteously disappear to conserve space on your
screen, to be replaced by a other popups such as the simulated DSKY
or a telemetry window, and will only return when the simulation
ends. <br>
<br>
To end the simulation, simply exit from any of the visible elements
of the simulation—though there's a bit of platform to platform
variation as to which components are easily terminated, so I'd
recommend closing the DSKY. Within a few seconds all of the
other elements of the simulation will automatically terminate.
Note, however, that the automatic closing of all the simulation
windows isn't active until several seconds (5 in most versions, 30
in some) have passed from the time the simulation started up, so if
you start a simulation and then immediately decide to shut it down,
you'll still have to wait a little while for the process to
complete. Also, on Mac OS X, there are various windows that
simply may not close automatically, and these will simply have
to be closed manually from their main menus.<br>
<h2><a name="Quick_Start"></a>Quick Start</h2>
I expect that anyone who would <span style="font-style: italic;">really</span>
use Virtual AGC would likely want to adapt it quite a bit, and so
any simple instructions I might give wouldn't help much. Not
to mention the burden of training yourself on the technical
nitty-gritty of Apollo systems before you can actually <span
style="font-style: italic;">use</span> the AGC for anything!
:-) But here are a few scenarios where you can quickly get to
the point of seeing <span style="font-style: italic;">something</span>
happen, if not necessarily anything meaningful to our sad little
earthbound minds. But there are still a few things you can try
that are amusing in a geekish sense.
<h3><a name="Running_the_Validation_Suite_"></a>Running the
Validation Suite<br>
</h3>
There is a "validation suite", which has been written from scratch
in AGC assembly language, that attempts to check that each CPU
instruction is implemented correctly in the AGC simulator. You
won't get the "Apollo experience" by running it, but at least you'll
be executing real AGC assembly-language code:<br>
<ol>
<li>Run <span style="font-weight: bold;">VirtualAGC</span> as
described above, select the "Validation Suite" choice in the
"Simulation Type" area, and hit the "Run!" button. </li>
<li>On the DSKY, you'll see 00 appear in the PROG and NOUN fields,
and you'll see the OPR ERR annunciator will light.
This means that the validation program is ready to start.
Press the DSKY's PRO key to start the program. The OPR ERR
annunciater will turn off to indicate that the command was
accepted.</li>
<li>After several tens of seconds, 77 will appear in the PROG
field and the OPR ERR annunciator will light. If anything
other than 77 appears in the PROG field, then the numbers in the
PROG and NOUN fields will indicate which area of the test
failed. (You can press PRO again to proceed with the
remaining tests.)<br>
</li>
</ol>
<h3><a name="Playing_with_Colossus_"></a><span
style="text-decoration: underline;"><a name="PlayColossus"></a></span>Playing
with
Colossus<br>
</h3>
(Actually, all of the things under " <a href="#PlayLuminary">Playing
with
Luminary</a>" work with Colossus also.)<br>
<br>
Run the VirtualAGC program as described earlier, select any of the
Command Module choices in the "Simulation Type" area, and then try
the following stuff: <a name="Screenshots"></a><br>
<ul style="color: rgb(0, 0, 0);">
</ul>
<table summary="" style="width: 100%; text-align: left;"
cellspacing="2" cellpadding="2" border="1">
<tbody>
<tr>
<td style="vertical-align: top;"><a href="V05N09E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="V05N09E-thm.png" width="147" height="167"></a><br>
</td>
<td style="vertical-align: top;">View the alarm codes<br>
</td>
<td style="vertical-align: top;">Because of some current bugs
(07/19/04) in the way I initialize Colossus, there will be
some program alarms at startup, and the PROG indicator will
light to inform you of this. You can view the alarms
by keying in V05N09E at the DSKY. (In normal AGC
shorthand, 'V' is short for "VERB", 'N' is short for "NOUN",
and 'E' is short for "ENTR". So "V05N09E" means to hit
the keys VERB 0 5 NOUN 0 9 ENTR.)<br>
<br>
Program alarms 1105 and 1106 happen to be "downlink too
fast" and "uplink too fast". Uplinks or downlinks
refer to exchange of telemetry information with ground
equipment.<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;"><a href="V35E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to Enlarge."
src="V35E-thm.png" width="147" height="167"></a></td>
<td style="vertical-align: top;">DSKY lamp test</td>
<td style="vertical-align: top;">At the DSKY, key in
V35E. This will light up all of the DSKY annunciators,
flash the VERB/NOUN labels, and display 88 or +88888 in all
of the numerical registers. After about 5 seconds, the
test stops—you can tell, because the flashing stops, though
the numbers remain—and you can continue.<br>
<br>
When the accompanying screenshot was taken, I didn't yet
know how the AGC controls the DSKY's STBY and RESTART
indicators, so those weren't turned on by the test.
Because of a bug in the simulator (as of 07/19/04), the PROG
indicator doesn't re-light after the lamp-test
completes. Therefore, you may or may not see the PROG
indicator lit if you try the sample operations below.<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;"><a href="V91E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="V91E-thm.png" width="147" height="167"></a><br>
</td>
<td style="vertical-align: top;">Display memory-bank checksums</td>
<td style="vertical-align: top;">The core-rope (read-only)
memory is divided into 36 banks, numbered 00-43
(octal). A so-called "bugger word" has been stuck at
the end of each bank—no comments on this terminology,
please, since I didn't invent it; when I asked Don Eyles
some question that involved them, he somewhat-laconically
stated "we called them check sums"—which causes the checksum
of the bank to come out to a known value. This known
value is the same as the bank number when possible, and is
the logical complement of the bank number otherwise.
(For example, the checksum of <span style="font-weight:
bold;">Colossus</span> bank 00007 is 00007, but the
checksum of bank 00006 is 77771. Both are
correct.) <span style="font-weight: bold;">Colossus</span>'s
"show-banksum"
program can be used to display the bank numbers, one by
one. You can execute the show-banksum program by
keying in V91E on the DSKY. After a few seconds, the
statistics for bank 00 will be shown: R1 (the topmost
5-digit display) will contain the computed checksum; R2 will
contain the bank number; and R3 will contain the bugger
word. Each of the displays will be in octal, as
indicated by the fact that the +/- sign is blank. To
advance to the next bank, key in V33E. (Hitting the
PRO key does the same thing.) If you have the patience
to advance through each of the banks, the next V33E (or PRO)
after bank 43 will wrap-around to bank 00 again. To
terminate the show-banksum program, you can key in V34E.<br>
<br>
By the way, the bank-6 bugger word shown (05143) is
for Colossus 249. If you ran the Artemis 072 program,
it would have been 04275, while if you ran the Luminary 131
program, it would have been 63402.<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;"><a href="V16N36E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to Enlarge."
src="V16N36E-thm.png" width="147" height="167"></a><br>
</td>
<td style="vertical-align: top;"><a name="MonitorTime"></a>Monitor
the
current time</td>
<td style="vertical-align: top;">If you key in V16N36E or
V16N65E, it will cause the current time to be
displayed. (Since we haven't set the time in any way,
this will be the time since AGC power-up). R1 (the
topmost 5-digit display) will be in hours, R2 will be in
minutes, and R3 will be in 100ths of a second. This
display is updated once per second.<br>
<br>
In the accompanying screenshot, the time is 06:58:33.86.<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;"><a href="V25N36E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="V25N36E-thm.png" width="147" height="167"></a><br>
</td>
<td style="vertical-align: top;">Setting the current time</td>
<td style="vertical-align: top;">If it annoys you to see the
time since power-up, you can change the time (for example,
to mission time) by keying in V25N36E. R1 will go
blank, enabling you to key in the current hour. Make
sure you start with a + sign (this is how the AGC knows
you're using decimal rather than octal), and make sure you
enter all five digits (including the leading zeroes).
In case you make a mistake, you can clear R1 any time before
pressing ENTR by using the CLR key. After you hit the
ENTR key, R2 will clear and you can enter the current
minutes. Finally, you can key in the number of seconds
in R3. Don't forget that the number of seconds is
actually in 100ths of seconds, so that if (for example) you
want 30 seconds you'd key in +03000E.<br>
<br>
In the accompanying screenshot, it just happened to be
06:55:25 am., so that's how I set the clock.<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;"><a href="V27N02E4000E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="V27N02E4000E-thm.png" width="147" height="167"></a><br>
</td>
<td style="vertical-align: top;">Examining the contents of the
core-rope</td>
<td style="vertical-align: top;">Key in V27N02E. This
allows you to enter the address of a word in the core-rope
into R3. This address will generally be in octal, and
therefore should not be preceded by a + sign. Also,
unlike entry of decimal data, in octal you can enter just as
many digits as you need, and don't need to enter a full five
digits. The addresses will be 00000-01777 for memory
bank 00, 02000-03777 for memory bank 01, and so forth, up to
76000-77777 for memory bank 37. (I'm not sure how to
examine banks 40-43.) The binary listing of the core
rope is at the very back of the Colossus 249 assembly
listing, which can be downloaded from MIT if you have some
spare time and disk space. (See my <a
href="links.html">links page</a>.)<br>
<br>
In the accompanying screenshot, we see that address 4000
(octal) of Luminary's core-rope contains the value
00004. This just happens to be the first instruction
executed after power-up. It is an <span
style="font-family: monospace;">INHINT</span> instruction,
and disables interrupts. The contents of R2 (the
middle 5-digit register) are not cleared, and thus are just
whatever lingers from before.<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;"><a href="V01N02E25E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="V01N02E25E-thm.png" width="147" height="167"></a><br>
</td>
<td style="vertical-align: top;">Examining the contents of
erasable memory</td>
<td style="vertical-align: top;">Key in V01N02E. This
allows you to enter the address of a word in erasable memory
into R3. The addresses will be 00000-00377 for
erasable bank E0, 00400-00777 for memory bank E1, and so
forth, up to 03400-03777 for memory bank E7.
Alternately, you can "monitor" a memory location (i.e., get
updates for it once per second) by using VERB 11 rather than
VERB 01. For example, V11N02E25E will monitor register
25, the "TIME1" register, which is an internal counter that
increments every 10 ms. In general, of course, the
numbers won't mean much unless you reference them to the
Colossus 249 assembly listing.<br>
<br>
In the accompanying screenshot, we actually do look at the
TIME1 register, and discover that at that instant it
contained the value 20245 (octal). Of course, you'll
see something different. Display R2 is not changed, so
it just contains whatever it contained before.<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;"><a href="V21N02E25E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="V21N02E25E-thm.png" width="147" height="167"></a><br>
</td>
<td style="vertical-align: top;">Altering the contents of
erasable memory</td>
<td style="vertical-align: top;">Key in V21N02E, and enter an
octal address as above, and then enter a new value to be
stored at that address. It goes without saying that
you need to know what you're doing when you do this!<br>
<br>
In the accompanying screenshot, I've chosen to reload the
TIME1 register with the value 12345 (octal), which probably
won't cause too many adverse effects. Display R2 is
not changed, so it just contains whatever it contained
before.</td>
</tr>
<tr>
<td style="vertical-align: top;"><a href="V36E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="V36E-thm.png" width="147" height="167"></a><br>
</td>
<td style="vertical-align: top;">Fresh start</td>
<td style="vertical-align: top;">Key in V36E. This
apparently restarts the "pinball" program—i.e., the program
that is responsible for accepting verbs and nouns and
displaying stuff on the DSKY—and it's useful for clearing
garbage from the DSKY's display, as the accompanying
screenshot demonstrates.<br>
<br>
In the accompanying screenshot, a side-effect of the fresh
start is the thoughtful re-display of the PROG (program
alarm) which the earlier DSKY lamp-test had wiped out.<br>
</td>
</tr>
<tr>
<td style="text-align: center; vertical-align: middle;"> (Your
picture here.)<br>
</td>
<td style="vertical-align: top;">Do-it-yourself research</td>
<td style="vertical-align: top;">The file
yaAGC/Colossus249/ASSEMBLY_AND_OPERATION_INFORMATION.s lists
the verb and noun tables, so perhaps you can figure out some
neat stuff yourself. If you do, <a
href="mailto:info@sandroid.org">let me know</a> and I'll
add it to this list.<br>
</td>
</tr>
</tbody>
</table>
<table summary="" style="width: 80%; text-align: left; margin-left:
40px; margin-right: auto;" cellspacing="2" cellpadding="2"
border="1">
</table>
<ul style="color: rgb(0, 0, 0);">
</ul>
<h3><a name="Playing_with_Luminary_"></a><span
style="text-decoration: underline;"><a name="PlayLuminary"></a></span>Playing
with
<span style="font-weight: bold;">Luminary</span><br>
</h3>
You can do the same things as for <span style="font-weight: bold;">Colossus</span>
above . Or rather than trying stuff at random, you can try
stepping through a more realistic startup checklist. (Thanks
to Julian Webb.)
<ul style="color: rgb(0, 0, 0);">
</ul>
<table summary="" style="width: 100%; text-align: left;"
cellspacing="2" cellpadding="2" border="1">
<tbody>
<tr>
<td style="vertical-align: top;">Step 0<br>
</td>
<td style="vertical-align: top;">Run the simulator<br>
</td>
<td style="vertical-align: top;">Run <span
style="font-weight: bold;">VirtualAGC</span> as described
above, select "Apollo 13 Lunar Module" in the "Simulation
Type" area, and hit "Run!"</td>
<td style="vertical-align: top;"><a href="LMV36E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="LMV36E-thm.png" width="147" height="167"></a><br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">Step 1<br>
</td>
<td style="vertical-align: top;">V35E<br>
</td>
<td style="vertical-align: top;">Starts the DSKY lamp
test. All of the indicator lamps are lit, the
numerical displays show 88 or +888888 as appropriate, and
things which are supposed to flash, flash. After about
5 seconds, the lamp test automatically terminates.<br>
</td>
<td style="vertical-align: top;"><a href="LMV35E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="LMV35E-thm.png" width="147" height="167"></a><br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">Step 2<br>
</td>
<td style="vertical-align: top;">V37E 00E<br>
</td>
<td style="vertical-align: top;">"Goto Pooh" — i.e., start
program P00, the idling program. The numeric area
under the PROG label will show 00.<br>
</td>
<td style="vertical-align: top;"><a href="V37E00E.png"><img
style="border: 0px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="V37E00E-thm.png" width="147" height="167"></a><br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">Step 3<br>
</td>
<td style="vertical-align: top;">V25E N01E 01365E 0E 0E 0E<br>
</td>
<td style="vertical-align: top;">Set the count of total failed
self-tests, total started self-tests, and
successfully-completed division tests to 0.<br>
</td>
<td style="vertical-align: top;"><a
href="V25N01E1365E0E0E0E.png"><img style="border: 2px
solid; width: 147px; height: 167px;" alt="Screenshot of
yaDSKY. Click to enlarge."
src="V25N01E1365E0E0E0E-thm.png" width="147"
height="167"></a><br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">Step 4<br>
</td>
<td style="vertical-align: top;">V15 N01E 01365E<br>
</td>
<td style="vertical-align: top;">Begin monitoring the
self-test counts. R1 (the top 5-digit display) shows
the number of failed tests, R2 shows the number of started
tests, and R3 the number of completed division tests.
Each should be +00000 ("all balls").<br>
</td>
<td style="vertical-align: top;"><a href="V15N01E1365E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="V15N01E1365E-thm.png" width="147" height="167"></a><br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">Step 5<br>
</td>
<td style="vertical-align: top;">V21 N27E 10E<br>
</td>
<td style="vertical-align: top;">Begin background
self-tests. These tests will continue until the
astronaut (you!) terminates them. Continue at least
until the number of started tests (R2) reaches 3.<br>
</td>
<td style="vertical-align: top;"><a href="V21N27E10E.png"><img
style="border: 2px solid; width: 147px; height: 167px;"
alt="Screenshot of yaDSKY. Click to enlarge."
src="V21N27E10E-thm.png" width="147" height="167"></a><br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">Step 6<br>
</td>
<td style="vertical-align: top;">V21 N27E 0E<br>
</td>
<td style="vertical-align: top;">Terminate the background
self-tests.<br>
</td>
<td style="text-align: center; vertical-align: middle;">
(Looks the same,<br>
of course.)<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;">...<br>
</td>
<td style="vertical-align: top;"><br>
</td>
<td style="vertical-align: top;">(more later)<br>
</td>
<td style="vertical-align: top;"><br>
</td>
</tr>
</tbody>
</table>
<br>
<h3><a name="Much_more_intensive_playing_with_the_LM"></a>Much more
intensive playing with the LM</h3>
Stephan Hotto has provided a helpful tutorial that will let you do
much more than the simple computer-maintenance activities described
above. Following his tutorial you'll be able to control the LM
using the hand-controller (joystick), see the orientation of the
spacecraft change on the 8-Ball, fire the thrusters, etc. The
instructions for his tutorial are actually build into the program
itself, so I'll just tell you enough to read his tutorial rather
than duplicating the tutorial's information here:<br>
<ol>
<li>Since you will be using the ACA simulation (joystick) for
this, <a href="yaTelemetry.html#Usage_of_yaACA3">you may need
to do a little configuration of the joystick first</a>, or
risk finding out that (say) you have no yaw control.<br>
</li>
<li>Run <span style="font-weight: bold;">VirtualAGC</span>,<br>
</li>
<li>Select the Apollo 13 Lunar Module AGC simulation in the
Simulation Type pane.</li>
<li>In the Interfaces pane, click the "Expert" button. (You
can unclick the AEA simulation if you like. The Telemetry
monitor won't be directly used either, but I like it so much I'd
never advise you to deselect it.)</li>
<li>Run!</li>
<li>In the window titled "LM Simulator v<span style="font-style:
italic;">N.N</span> by Stephan Hotto", select Info/Tutorial
from the menu bar.</li>
<li>In the window titled "Tutorial for LM System Simulator" that
pops up, follow <span style="font-style: italic;">either</span>
the instructions in Section 0.0 <span style="font-style:
italic;">or</span> else the instructions in Sections
0.1-1.4,2.0-2.3.<br>
</li>
</ol>
<h3><a name="Canned_pre-recorded_mission_segments"></a> Canned,
pre-recorded mission segments</h3>
<p><img src="V21N27E10E-PROG.png" alt="" width="196" height="223"
align="right">One nice thing about open-source software (which
our Virtual AGC Project is!) is that other people are free to
incorporate the software within their own projects, and thus it
can see a more-rapid diffusion into a wider sphere of usage than
would have been possible if (say) it was just me developing it by
myself. In the case of Virtual AGC, one thing that has been
done with it is that it has been incorporated into <a
href="http://orbit.medphys.ucl.ac.uk/">the Orbiter Space Flight
Simulator system</a>, via the <a
href="http://nassp.sourceforge.net/wiki/Main_Page">Project
Apollo NASSP add-on</a>, which people then use to fly very
realistic or imagined Apollo missions. The NASSP folks have
been kind enough to incorporate the capability of logging
interactions between the simulated AGC and simulated DSKY, with
the result that we can "play back" (though not interact with) such
realistic logged activity on the simulated DSKY.<br>
</p>
<p>This capability is only available in Virtual AGC software
versions 2017-12-11 and later, and it works as follows: if
you left-click on the PROG lamp indicator with the mouse, a
file-dialog will open up. Of course, in the <i>real</i>
DSKY, PROG was not a button; it was merely a lamp. But we've
assigned it this additional function in our simulated DSKY.
In the file-dialog, select the pre-recorded script<br>
</p>
<blockquote>
<p><tt>Apollo8-launch.canned</tt><br>
</p>
</blockquote>
<p>As you may imagine, this is a recorded Apollo 8 launch sequence,
which takes about 15 minutes to play back. You'll see
various things in watching it:<br>
</p>
<ul>
<li>PROG 02, VERB 75. The script begin at T-40, i.e., 40
seconds prior to launch, and in this state the AGC simply waits
to receive an ignition signal from the Saturn rocket ... or
technically, what it will eventually receive is the "liftoff
discrete" from the S-IVB stage. Program 02 is the Gyro
Compassing Program, and its purpose is "to provide the stable
member orientation for launch". The "stable member" is a
part of the inertial measuring unit (IMU) which holds the
gyroscope (for determining the spacecraft orientation) and the
accelerometers. The astronaut doesn't actually have to
select Program 02, because it is automatically selected by
Program 01 (the initialization program), which was run prior to
T-40, and hence you won't see it in the playback.<br>
</li>
<li>PROG 11, VERB 06, NOUN 62. At ignition, the AGC
automatically transitions from Program 02 to Program 11, the
Earth Orbit Insertion Monitor Program. Realize that the
AGC itself was not able to control the Saturn rocket itself,
other than the Saturn IVB stage, and the Saturn was controlled
instead by its own internal computer, <a href="LVDC.html">the
LVDC</a>. The AGC's real work began later! Nor did the AGC
receive any information from the LVDC as to the quantities it is
monitoring and displaying on the DSKY. The LVDC and AGC
separately each had access to their own inertial measurement
units (IMUs) that measured the acceleration and orientation of
the spacecraft, and by mathematically integrating this data from
the IMU, the LVDC and AGC could independently figure out
everything they needed to know about the current state of motion
of the rocket ... and hopefully the LVDC and AGC would come up
with very similar results. So this monitoring activity is
much less trivial that it may sound to you at first. As
for what's actually being monitored in this program, the AGC is
driving the FDAI (i.e., the "eight ball" or "attitude
indicator") is being driven to show the astronaut the
orientation of the rocket in a nice graphical way, though the
FDAI is not a part of the DSKY. But the AGC is also
computing trajectory parameters and displaying them on the
DSKY. Those parameters, from top to bottom, are "VI" (the
inertial velocity magnitude, in feet per second), "H DOT" (the
rate of change of altitude above the launch pad, also in feet
per second), and "H" (the height above the launch pad, in tenths
of a nautical mile).<br>
</li>
<li>PROG 11, VERB 16, NOUN 50. After a few minutes, the
astronaut has initiated this monitoring command. You'll
notice that the KEY REL lamp is flashing, because the previous
monitoring (VERB 16, NOUN 62) wasn't actually terminated but
merely temporarily interrupted, and the astronaut is being
warned that when he terminates the VERB 16 NOUN 50 monitoring
he'll automatically return to the other monitoring. As for
what's being monitored here, from top to bottom, it's the
"splash error" (in tenths of a nautical mile), and a couple of
other items about which the documentation is inconsistent.
The "splash error" part sounds a bit confusing, but apparently
in Program 11 it has nothing to do with splash-down, but is
rather the negative of the range to target.<br>
</li>
<li>... and so on. Eventually, after this phase of the
mission is completed, the astronaut keys in VERB 37 ENTR 00 ENTR
to return to program 00, and then keys in VERB 66. I'm not
sure why the latter was done. It was for transferring
state vectors (i.e. the position, velocity, and orientation)
from the LM's AGC to the CM's, or vice-versa. But of
course, for Apollo 8 there was no LM. Oh well, I'm
inexcusably ignorant, so it's probably the correct thing to do!<br>
</li>
</ul>
<p>If you get tired in the middle of all this and don't want to
watch it all the way to the end, just click PROG again to
terminate the script.<br>
</p>
<h3> </h3>
<h3><a name="Playing_with_the_Abort_Guidance_System_"></a><span
style="text-decoration: underline;"><a name="QuickStartAGS"></a></span>Playing
with
the Abort Guidance System</h3>
Now admittedly, I don't understand much you can do with the Abort
Guidance System myself, nor do I claim that the program is complete,
but there are <span style="font-style: italic;">some</span> things
you can try:<br>
<br>
<table summary="" style="width: 100%; text-align: left;"
cellspacing="2" cellpadding="2" border="1">
<tbody>
<tr>
<td style="vertical-align: top;"><a href="AgsSelfTestFail.png"><img
style="border: 2px solid; width: 144px; height: 178px;"
alt="DEDA displaying results of self-test" title="Click
to enlarge" src="thumb-AgsSelfTestFail.png" width="144"
height="178"></a><br>
</td>
<td style="vertical-align: top;">CLR 4 1 2 READOUT<br>
</td>
<td style="vertical-align: top;"> View the results of the
self-test, which are stored in the AGS CPU at (octal)
location 412. A code of +10000 means the test has
passed. <br>
<br>
Oops! the test has failed. That's because the
self-test is pretty thorough; it tests not only memory
checksums, but also the operation of various CPU
instructions. The possible error codes here are:<br>
<div style="margin-left: 40px;"> +000000 Test still
in progress<br>
+100000 Test passed<br>
+300000 Logic test failure<br>
+400000 Memory test failure<br>
+700000 Logic <span style="font-style:
italic;">and</span> memory test failure<br>
</div>
<br>
I was having a little problem with the instruction set when
this screenshot was taken, thus the self-test failed.
Fortunately, the AGS flight programs have been written to
continue operating in the case of self-test failure, even
though it is "not recommended". The current version of
<span style="font-weight: bold;">yaAGS</span> actually does
pass the self-test, and so you'll see a code of +100000
here.<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;"><a href="AgsSetClock.png"><img
style="border: 2px solid; width: 144px; height: 178px;"
alt="Resetting the clock." title="Click to enlarge"
src="thumb-AgsSetClock.png" width="144" height="178"></a><br>
</td>
<td style="vertical-align: top;">CLR 3 7 7 + 0 0 0 0 0 ENTR<br>
</td>
<td style="vertical-align: top;">Set the clock to 0. The
CPU uses address 377 (octal) as a counter that increments at
6-second intervals. Before using it, though, we want
to set it to a known value. <br>
<br>
In real life, the AGS time would be initialized by
synchronizing with the AGC electronically. However,
I'm not quite yet ready with that particular feature.<br>
</td>
</tr>
<tr>
<td style="vertical-align: top;"><a href="AgsViewClock.png"><img
style="border: 2px solid; width: 144px; height: 178px;"
alt="DEDA display of incrementing time." title="Click to
enlarge" src="thumb-AgsViewClock.png" width="144"
height="178"></a><br>
</td>
<td style="vertical-align: top;">CLR 3 7 7 READOUT<br>
</td>
<td style="vertical-align: top;">Watch the clock
incrementing. Although the counter changes at 6-second
intervals, and counts in units of 6 seconds, the CPU
actually updates the DEDA display every 1/2 second.<br>
</td>
</tr>
<tr>
<td colspan="3" rowspan="1" style="vertical-align: top;"> The
operations listed above are very representative from the
user-interface perspective of all the other kinds of
operations you can perform on the DEDA. There are
basically two classes of DEDA-based operations:<br>
<ol>
<li>Get a running display of the contents of a memory
location. The command sequence for this is <span
style="font-family: monospace;">CLR <span
style="font-style: italic;">OctalDigit1 OctalDigit2
OctalDigit3</span> READOUT</span> . Upon
receiving this command, the AGS CPU will monitor the
selected memory location and display it on the DEDA
every 1/2 second. You can pause the readout by
hitting <span style="font-family: monospace;">HOLD</span>,
or resume it by hitting <span style="font-family:
monospace;">READOUT</span> again. The flight
software will automatically scale the data or otherwise
modify it (by changing units of measurement) in a way
appropriate to the particular memory location before
displaying the data. If you make a mistake in the
key sequence, the OPR ERR lamp will light, and you'll
have to hit <span style="font-family: monospace;">CLR</span>
to clear the error condition.</li>
<li>You can change the value of a location of
memory. In doing so, the flight software may
choose to interpret your action as a command to perform
some further action, but I'm not up to speed on what
those other actions might be. The command sequence
is <span style="font-family: monospace;">CLR <span
style="font-style: italic;">OctalDigit1 OctalDigit2
OctalDigit3</span> +/- <span style="font-style:
italic;">Digit1 Digit2 Digit3 Digit4 Digit5</span>
ENTR</span> . The 5-digit data may be
octal or decimal, but that is dependent on the
particular memory location chosen, and isn't a choice
that the astronaut/user makes. Again, a mistake in
the sequence will cause the OPR ERR lamp to light.</li>
</ol>
Of course, there are operations the astronaut/user can
perform that are outside of this framework, such as hitting
the ABORT button or downloading the spacecraft state vector
from the AGC. However the abort button is a separate
switch rather than being a part of the DEDA, and I've not
perfected AGC-to-AGS communication yet.<br>
</td>
</tr>
</tbody>
</table>
<br>
<h3><a name="Playing_with_AGC_assembly_language_"></a>Playing with
AGC assembly language<br>
</h3>
You can modify the validation-suite AGC assembly-language software
I've provided, and then run the modified software on <span
style="font-weight: bold;">yaAGC</span>, as follows.<br>
<ol>
<li style="color: rgb(0, 0, 0);">Copy the folder containing the
Validation Suite software to a new folder. (In the
developer snapshot, these are the files yaAGC/Validation/*.s; in
the binary installation, they'll still be the files *.s, but the
easiest way to find the name of the directory they're in is to
"Browse Source Code" from within the <span style="font-weight:
bold;">VirtualAGC</span> program and to simply note down what
directory is being referenced by the browser.)<br>
</li>
<li style="color: rgb(0, 0, 0);">Edit some of the validation-suite
source-code files. The assembly-language programmer's
manual is <a href="assembly_language_manual.html">here</a>.<br>
</li>
<li>Run the VirtualAGC program, select "Custom" in the "Simulation
Type" area, choose Validation.s from the folder in which you've
been working. After <span style="font-weight: bold;">VirtualAGC</span>
automatically runs this through the assembler to create a binary
executable, just hit "Run!".<br>
</li>
<li>You should now see the DSKY doing whatever you've programmed
it to do. <br>
</li>
<li>On the chance that your program may not do what you expected
it to do, there is primitive debugging capability built into <span
style="font-weight: bold;">yaAGC</span> which may be helpful
in tracking down the problems. Just select "Run with debug
monitor" under "AGC Debug" in the "Options" area of <span
style="font-weight: bold;">VirtualAGC</span>.
Instructions for how to use the debugger are <a
href="yaAGC.html#Debugging">here</a>. <br>
</li>
</ol>
<br>
<h3><a name="Modifying_the_LM"></a>Modifying the LM software (for
the truly brave)</h3>
Same as "Playing with AGC assembly language", but start from the
Luminary131 source code instead of the Validation Suite software,
and note that the "custom" file you have to select is MAIN.s rather
than Validation.s.<br>
<br>
<h3><a name="Final_exam_for_the_advanced_student_"></a>Final exam
(for the advanced student)</h3>
Prior to the descent of Apollo 14's LM to the lunar surface, a short
in the LM control panel caused the abort switch to be triggered
intermittently. If this actually happened during the landing,
an abort would have automatically occurred (meaning that the lower
stage of the LM would have been jettisoned and the upper stage would
have blasted back into space). No landing would have been
possible, and the astronauts would have faced the grave situation of
needing rescue by the command module. It was therefore
necessary, in the orbit or two before descent, for the some of the
software designers to work out a fix for this problem that allowed a
software lockout of the abort switch during the initial phase of the
descent, but also allowed reenabling the abort switch later in the
descent, in case the astronauts needed to use it. They did, in
fact, work out such a fix. Your mission, should you choose to
accept it, is this: Work out such a fix and send it to
me. Remember, your fix can only involve erasable memory, since
the core-rope containing the program cannot be altered. The
fix needs to be keyed in at the DSKY by the astronauts. You
have about 90 minutes to figure it out. Go!<br>
<br>
<a href="#Solution_to_the_Apollo_14_Final_Exam">Click here for the
solution.</a><br>
<br>
<h3><a name="..._Or_for_the_silly_mood_"></a>... Or, for the silly
mood</h3>
Use Virtual AGC as a clock for your PC desktop. (My word, this
software is versatile!) I'd suggest using the "DSKY Type" of
"Half-size" for this. Use the <a href="#MonitorTime">instructions
given
above</a> for setting and monitoring the time. You'll have
to reset the time very morning, because the "hours" will not wrap
around to 0 after 24. (And besides, the timers will overflow
after 2<sup>28</sup>/100 seconds, or just over 31 days.)<br>
<br>
<span style="font-weight: bold;">Hint:</span> Once you get
this working well, you'll want to be able to start this up
automatically, and not have to run <span style="font-weight: bold;">VirtualAGC</span>
every time. Well, when <span style="font-weight: bold;">VirtualAGC</span>
runs the simulation, it does so by creating batch files (in Windows)
or a shell script (in Linux or Mac OS X), then simply running those
batch files or shell scripts. When you run a custom program in
<span style="font-weight: bold;">VirtualAGC</span>, you use the
"More" button in the simulation window to show you the contents of
those batch files or shell scripts. So you can reuse or adapt
those files for starting up your own simulation.<br>
<br>
Actually, we now have <a href="DIY.html">a "do it yourself" page</a>
that gives a lot of helpful information on the topic of creating
your own custom AGC code. In fact, it provides sample AGC code
that actually implements the clock app, without requiring you to
manually enter the time at power-up or every morning. Check it
out!<br>
<br>
<h3><a name="..._Or_for_the_even_sillier_mood_"></a>... Or, for the
even sillier mood</h3>
Write your own AGC or AEA assembly language program for a
calculator, or a game (like tic-tac-toe), or some other frivolous
purpose. It's not very respectful, but it will hone your
skills for that next AGC or AEA programmer opening you hear
about. :-)<br>
<br>
Again, check out <a href="DIY.html">the do-it-yourself page</a> for
more info.<br>
<br>
<h2><a name="Acknowledgements"></a>Acknowledgements</h2>
(When I first added this section to the document, I thought it would
be easy to keep up-to-date. It isn't. As it happens, <i>so</i>
many people have stepped forward at one point or another that my
mind simply isn't big enough to hold all of their names. So
it's entirely possible that even very significant contributors may
have been inadvertently omitted from the list below. Have no
hesitation about reminding me if I've slighted you by forgetting to
mention you!)<br>
<h3>AGC Software Developers<br>
</h3>
Of course, it goes without saying that the greatest thanks go to the
original software developers of the Apollo project, even if I've
never personally had any contact with most of them. Hugh
Blair-Smith needs to be specially mentioned, since his activities
had a special relevance to my own project, and since he has
patiently allowed me to pepper him with many questions. Don
Eyles as well has made himself especially available, and has
provided huge amount of software and documentation to us. But
we are told that as many as 300-400 programmers contributed to the <span
style="font-weight: bold;">Colossus</span> and <span
style="font-weight: bold;">Luminary</span> source code.
Though not specifically a <span style="font-style: italic;">software</span>
developer, Eldon C. Hall also has been very specifically helpful to
me; Fred Martin, and Jim Kernan have also turned out be particular
heroes in terms of the operation of this project. <br>
<br>
I've not yet uncovered a "full" list of the AGC software
developers. But we're not totally helpless in figuring out at
least a partial list. <a
href="Documents/Memo-Lickly681007_text.pdf">A memo by Dan Lickly
(a developer himself) about software testing</a> gives us a list
developers who were responsible for specific "programs", "routines",
and "areas" within LUMINARY, as of October 1968, and another,
more-abbreviated <a href="Documents/LUM6_text.pdf">memo by George
Cherry</a> gives a similar list as of January 1968. Some of
the folks in those memos are known <i>not</i> to have been AGC
software developers, though, and I've factored them out where I knew
to do so. At any rate, here's the list:<br>
<ul>
<li>Program P12: Larry Berman</li>
<li>Program P06: Dana DeWolf</li>
<li>Programs P10-P11: Phil Shakir<br>
</li>
<li>Program P12: Larry Berman<br>
</li>
<li>Program P20: Peter Volante, Virginia Dunbar<br>
</li>
<li>Program P21: Ted Crocker<br>
</li>
<li>Program P22: Peter Volante, Virginia Dunbar<br>
</li>
<li>Program P25: Peter Volante, Jack Connor<br>
</li>
<li>Program P27: Paul Fagin<br>
</li>
<li>Program P30: Peter Adler</li>
<li>Programs P31-P35: Pat White<br>
</li>
<li>Programs P38-P39: Jane Goode<br>
</li>
<li>Programs P40-P42: Peter Adler<br>
</li>
<li>Progam P47: Bob Covelli, Ken Vincent<br>
</li>
<li>Programs P51-P52: Don Millard<br>
</li>
<li>Programs P57: Don Millard<br>
</li>
<li>Programs P63-P67: Don Eyles</li>
<li>Programs P66-P67: Don Eyles, Craig Schulenberg</li>
<li>Programs P70-P71: Walter Bernikowich, Larry Berman<br>
</li>
<li>Programs P72-P75: Pat White<br>
</li>
<li>Program P76: Ted Crocker</li>
<li>Programs P78-P79: Jane Goode<br>
</li>
<li>Routines R00: Dana DeWolf<br>
</li>
<li>Routines R02: Dana DeWolf<br>
</li>
<li>Routine R03: Peter Weissman<br>
</li>
<li>Routine R04: Jim Kernan<br>
</li>
<li>Routine R05: Peter Volante<br>
</li>
<li>Routine R10: Walter Bernikowich<br>
</li>
<li>Routine R11: Don Eyles, Walter Bernikowich<br>
</li>
<li>Routine R12: Bob Covelli<br>
</li>
<li>Routine R13: Don Eyles</li>
<li>Routine R21-R25, R29: Peter Volante<br>
</li>
<li>Routine R30: Frank Gauntt<br>
</li>
<li>Routine R31: Ted Crocker</li>
<li>Routine R33: George Cox<br>
</li>
<li>Routine R36: Ted Crocker</li>
<li>Routine R47: Jim Kernan, Phyllis Rye<br>
</li>
<li>Routines R50-R55, R59: Don Millard<br>
</li>
<li>Routine R60: Frank Gauntt<br>
</li>
<li>Routine R61: Virginia Dunbar, Jack Connor<br>
</li>
<li>Routines R62-R63: Frank Gauntt<br>
</li>
<li>Routine R65: Virginia Dunbar, Jack Connor<br>
</li>
<li>Routine R77: Jim Kernan<br>
</li>
<li>Pinball: John Vella, Marjorie Besas</li>
<li>Display interface: Margaret Hamilton, Phyllis Rye<br>
</li>
<li>Restarts, fresh start, and other service areas: Phyllis Rye,
Dana DeWolf</li>
<li>Integration: Bill Ostanek</li>
</ul>
Of course, we can't assume from this snapshot in time of one
specific program (LUMINARY, but not COLOSSUS) that these were the
only folks involved, nor even necessarily the most-significant
ones. We know that some of the original developers of these
software items had already moved on, and so it wouldn't be
surprising if some of these "responsible" folks on the list were
basically trainees who maintained software that was already mature
and never needed any changes. Or perhaps not! We can't
tell from just the list by itself. <br>
<br>
Indeed, you can get a very different outlook if you look at the
program comments within the software itself. For example, in
the list above, John Vella and Marjorie Besas are responsible for
PINBALL (the display/keyboard program); what does the source code
for PINBALL itself tell us? Well, the software neglects to
tell us who wrote PINBALL originally, but it does show a
modification by "FILENE" in 1967, and another by "BARNERT" in 1969,
but neither Filene nor Barnert is on the list above.<br>
<br>
If we do poke around in the AGC software source code, we can come up
with a competing list of the programmers who originally wrote or
modified the code. But many in the seemingly faceless mob who
wrote the software never thought to tell you who they were at
all. Here's the list of the ones that did choose to identify
themselves, along with a sprinkling of names that I got through
personal correspondence with developers. There's some overlap
with the list above, but not much!<br>
<br>
<table summary="" style="text-align: left; width: 100%;"
cellspacing="2" cellpadding="2" border="1">
<tbody>
<tr>
<td style="vertical-align: top;">Jonathan D. Addelston, <a
href="http://www.fishneave.com/people/bio.aspx?employee_id=320916505&txtLastName=A&type=lastname">A.
Peter Adler</a>, Rama M. Aiyawar, <a
href="http://klabs.org/mapld04/invited/alonso_bio.htm">Ramón
Alonso</a>, R. R. Bairnsfather, Ruth Birtwell, <a
href="http://klabs.org/mapld04/invited/blair_smith_bio.htm">Hugh
Blair-Smith</a>, Norm Brodeur, George W. Cherry, Edgar M.
Oshika, Ed Copps, Steve Copps, Bob Covelli, J. D. Coyne,
Danforth, Dana Densmore, DeWitt, Bart DeWolf, Stan Eliassen,
Al Engle, Don Eyles, Fagin, Filene, Naomi Fisher, Jim
Flanders, Follett, Gauntt, Richard D. Goss, John Green, <a
href="http://klabs.org/home_page/hamilton.htm">Margaret
Hamilton</a> (see also <a href="http://www.htius.com">Hamilton
Technologies,
Inc.</a>), R. Hirschkop, Mike Houston, Eileen T. Hughes,
Lowell G. Hull, T. James, G. Kalan, Don Keene, James E.
Kernan, Kilroy, Allan Klumpp, Tom Knatt, Alex Kosmala,
Krause, Dan Lickly, Lonske, Lu, Fred W. Martin, R. "Mel"
Melanson, Jim Miller, John Miller, Ray Morth, N. M. Neville,
Henry J. Noble, North, Olsson, Rhode, Robertson, S.
Rudnicki, Phyllis Rye, Jay A. Sampson, Joe Saponaro, Robert
Schlundt, George Schmidt, Schulenberg, P. Shakir, Smith, <a
href="http://www.princeton.edu/%7Estengel/">Robert F.
Stengel</a>, Gilbert Stubbs, Sturlaugson, Richard Talayco,
W. H. Vandever, Ken Vincent, Peter Volante, P. S. Weissman,
P. White, Bill Widnall, Ron Wiggins, Willman, Craig Work,
Saydean Zeldin.<br>
</td>
</tr>
</tbody>
</table>
<br>
It should go without saying that by singling out coders, I don't
mean to imply that hardware design, system architecture, or even
program management is not important. The AGC hardware was
certainly pretty revolutionary for its time, in terms of
miniaturization and reliability. And indeed, the electrical
schematics we have are littered with signatures, initials, and dates
of the responsible folks ... tiny, illegible smudges of names in our
scans of them. So in the end, we only know a tiny (but
important) subset of those involved.<br>
<br>
A <span style="font-style: italic;">complete</span> AGC honor roll
would need to include names like Charles Stark Draper and many
others. But the Virtual AGC project certainly emphasizes the
software aspects of the AGC over the hardware aspects, so the
software developers are the ones particularly being honored here. As
it happens, developer Peter Volante has sent me a bunch of org
charts showing a little bit about how the MIT Instrumentation Lab's
internal Apollo organization evolved over time, and many of the
names listed above appear in those org charts, though in a
more-structured way:<br>
<br>
<table cellspacing="2" cellpadding="2" align="center">
<tbody>
<tr>
<td valign="top"><a href="Documents/ApolloOrg-1962-05.jpg"><img
alt="" title="Click to expand"
src="thm-ApolloOrg-1962-05.jpg" width="211" height="160"
border="2"></a><br>
<div align="center"><small><i>May 1962</i></small><br>
</div>
</td>
<td valign="top"><a
href="Documents/ApolloOrg-Group-23B-only-1968-09.jpg"><img
alt="" title="Click to enlarge"
src="thm-ApolloOrg-Group-23B-only-1968-09.jpg"
width="243" height="160" border="2"></a><br>
<div align="center"><i><small>September 1968, Group 23B only</small></i><br>
</div>
</td>
<td valign="top"><a href="Documents/ApolloOrg-1969-02.pdf"><img
alt="" title="Click to enlarge"
src="thm-ApolloOrg-1969-02.jpg" width="207" height="160"
border="2"></a><br>
<div align="center"><small><i>February 1969 (18 pages)</i></small><br>
</div>
</td>
<td valign="bottom" align="center">
<div align="center"><a
href="Documents/ApolloOrg-1972-02.pdf"><img alt=""
title="Click to enlarge"
src="thm-ApolloOrg-1972-02.jpg" width="207"
height="160" border="0"></a><br>
</div>
<div align="center"><i><small>February 1972 (18 pages)</small></i><br>
</div>
</td>
</tr>
</tbody>
</table>
<h3>Others<br>
</h3>
<ul>
<li>I don't want to forget the original developers of the AGS
software either, but I don't yet know any of your names!</li>
<li>Gemini software developers Gene Mertz, Charlie Leist, Alden
Minnick, and Don O'Neill have been of assistance to me, and
other references to the original developers appear on the <a
href="Gemini.html">Gemini page</a>.<br>
</li>
<li>I'm grateful to the folks at MIT's Dibner Institute's
now-discontinued History of Recent Science and Technology
website for making the scans of <span style="font-weight:
bold;">Luminary</span> 131 and <span style="font-weight:
bold;">Colossus</span> 249, along with scans of other related
documents, available online. I'm not sure who is
responsible for providing the online version of <span
style="font-weight: bold;">Colossus</span> 249 (at MIT's
site), but a special thanks goes to you. Thanks to
David Mindell for helping me to move in the right direction with
my inquiries, and to Sandy Brown for giving me extremely
valuable information about the available AGC-related material at
MIT.<br>
</li>
<li>Gary Neff deserves a big vote of gratitude for having the
foresight (and presumably fortitude) to create the page scans of
<span style="font-weight: bold;">Luminary</span> 131 software
source code. Without those I wouldn't even have attempted
this project. Mr. Neff has also been extremely
helpful in supplying me with quite a lot of replacement scans
for garbled pages (52 of them so far) in the currently-available
online versions of <span style="font-weight: bold;">Colossus</span>
249. (Thanks also to Mr. Eric Jones, of the <a
href="http://www.hq.nasa.gov/alsj/">Apollo Lunar Surface
Journal</a>, for putting me into contact with Mr. Neff.)</li>
<li>Thanks also to the many helpful people at <a
href="http://www.archives.gov/facilities/tx/fort_worth.html">NARA
Southwest
Region</a>. Special thanks to Rodney Krajca and Meg
Hacker.</li>
<li>Thanks to Julian Webb for some very fruitful interactions, in
comparing his AGC simulator to mine, for explaining some
interactions between the AGC and DSKY, and for some helpful
introductions.</li>
<li>Acquisition of the Apollo 15-17 CM AGC software was a team
effort:<br>
<table summary="" style="text-align: left; width: 100%;
margin-left: auto; margin-right: auto;" cellspacing="2"
cellpadding="2" border="1">
<tbody>
<tr>
<td style="vertical-align: top;">
<div style="text-align: center;"> <span
style="font-weight: bold;"><span
style="text-decoration: underline;">Apollo 15-17
CM Honor Roll</span></span> </div>
<ul>
<li>The anonymous donor of the Artemis 72 program
listing, who I have oh-so-amusingly previously
referred to as "D. Thrust". (It's a
Nixon/Watergate joke, folks!)<br>
</li>
<li>(In alphabetical order) Steve Case, Hartmuth
Gutshe, Onno Hommes, Jim Lawton, and Sergio Navarro,
for converting the page images to source code.</li>
<li>Jim Lawton for debugging the source code.
This is an enormous amount of effort, and since it
is the first time I didn't have to do it myself, I'm
very appreciative. Jim also did a lot of extra
editing and behind-the-scenes management.<br>
</li>
</ul>
</td>
</tr>
</tbody>
</table>
</li>
<li>Acquisition of the Apollo 11 LM & CM AGC software was a
team effort:<br>
<table summary="" style="text-align: left; width: 100%;
margin-left: auto; margin-right: auto;" cellspacing="2"
cellpadding="2" border="1">
<tbody>
<tr>
<td style="vertical-align: top;">
<div style="text-align: center;"> <span
style="font-weight: bold;"><span
style="text-decoration: underline;">Apollo 11
Honor Roll</span><br>
</span>
<div style="text-align: left;"> <span
style="font-style: italic;"><br>
<span style="text-decoration: underline;">Organizational
honors</span></span><br>
</div>
</div>
<table summary="" style="text-align: left; width: 100%;"
cellspacing="2" cellpadding="2" border="0">
<tbody>
<tr>
<td style="vertical-align: middle;"> <big><span
style="font-family: sans-serif;">Massachusetts
Institute
of Technology / MIT Museum</span><br
style="font-family: sans-serif;">
<span style="font-family: sans-serif;">Building
N51,
265 Massachusetts Avenue</span><br
style="font-family: sans-serif;">
<span style="font-family: sans-serif;">Cambridge,
MA
02139<br>
<a href="http://web.mit.edu/museum/"><small>web.mit.edu/museum/</small></a><br>
</span></big></td>
<td style="text-align: center; vertical-align:
middle;"> <a href="http://web.mit.edu/museum/"><img
alt="" title="Click to visit the MIT Museum
website" src="MITMuseumLogo_red.gif"
style="border: 0px solid; width: 107px;
height: 101px;" width="107" height="101"></a><br>
</td>
</tr>
</tbody>
</table>
<br>
<span style="font-style: italic; text-decoration:
underline;">Individual honors</span><br>
<ul>
<li>Deborah Douglas, the Museum's Curator of Science
and Technology, who conceived the idea of making
this material available to us, and without whom we
had literally no chance of obtaining it.</li>
<li>Paul Fjeld, for digitizing the hardcopy.</li>
<li>(In alphabetical order) Fabrizio Bernardini,
Hartmuth Gutshe, Onno Hommes, Jim Lawton, and Sergio
Navarro, for converting the page images to source
code.</li>
<li>Steve Case and Dawn Masuoka for helping to proof
the LM binary.<br>
</li>
<li>... and those whose names I do not know at the
Charles Stark Draper Laboratory and NASA who allowed
us to do this.<br>
</li>
</ul>
</td>
</tr>
</tbody>
</table>
</li>
<li>Thanks to Paul Fjeld, who has fed me extraordinary information
on locating versions of <span style="font-weight: bold;">Luminary</span>
and <span style="font-weight: bold;">Colossus</span> source
code not otherwise known to me, and on various other related
topics.</li>
<li>Thanks to Fabrizio Bernardini for providing some unique
documentation.</li>
<li>Acquisition of the Apollo 6 CM AGC software was a team effort:</li>
</ul>
<div style="margin-left: 40px;">
<table summary="" style="text-align: left; margin-left: auto;
margin-right: auto;" cellspacing="2" cellpadding="2" border="1">
<tbody>
<tr>
<td style="vertical-align: top;">
<div style="text-align: center;"> <span
style="font-weight: bold;"><span
style="text-decoration: underline;">Apollo 6 Honor
Roll</span><br>
</span>
<div style="text-align: left;"> <span
style="font-style: italic;"><br>
<span style="text-decoration: underline;">Organizational
honors</span></span><br>
</div>
</div>
<table summary="" style="text-align: left; width: 100%;"
cellspacing="2" cellpadding="2" border="0">
<tbody>
<tr>
<td style="vertical-align: middle; white-space:
nowrap;"> <big><span style="font-family:
sans-serif;">American Computer Museum</span><br
style="font-family: sans-serif;">
<span style="font-family: sans-serif;">Bozeman,
Montana</span><span style="font-family:
sans-serif;"><br>
<a href="http://www.compustory.com/"><small>www.compustory.com</small></a><br>
</span></big></td>
<td style="text-align: center; vertical-align:
middle;"> <span style="text-decoration:
underline;"><a href="http://www.compustory.com/"><img
alt="" src="AmericanComputerMuseumLogo.jpg"
style="border: 0px solid; width: 171px;
height: 59px;" width="342" height="117"></a></span><br>
</td>
</tr>
</tbody>
</table>
<br>
<span style="font-style: italic; text-decoration:
underline;">Individual honors</span><br>
<ul>
<li>Eldon C. Hall, for his foresight in preservation,
the leads he provided, and for his overall approval.<br>
</li>
<li>George Keremedjiev, Curator of the American Computer
Museum, for making the listing available.<br>
</li>
<li>Kim Scott, Archivist of Special Collections, Renne
Library, Montana State University, and other MSU
individuals whose names I do not know, for helpful and
responsible supervision of the digitization effor.<br>
</li>
<li>Marilyn Chang, Librarian, Wings Over the Rockies Air
& Space Museum, for the necessary research and
contacts.<br>
</li>
<li>Fabrizio Bernardini, for bringing Marilyn into the
loop.</li>
<li>Henry Wesso, for constructing the special copy stand
used for the digitization.</li>
<li>Gil Guerrero, for providing advice and camera
equipment.</li>
<li>Jim Lawton, who seems to have single-handedly
converted the scanned pages both to source-code and
binary form.<br>
</li>
</ul>
</td>
</tr>
</tbody>
</table>
</div>
<ul>
<li>Acquisition of the AURORA 12 and SUNBURST 120 (Apollo 5) LM
AGC software was a team effort:</li>
</ul>
<div style="margin-left: 40px;">
<table summary="" style="text-align: left; margin-left: auto;
margin-right: auto;" cellspacing="2" cellpadding="2" border="1">
<tbody>
<tr>
<td style="vertical-align: top;">
<div style="text-align: center;"> <span
style="font-weight: bold;"><span
style="text-decoration: underline;">AURORA and
Apollo 5 Honor Roll</span><br>
</span>
<div style="text-align: left;"> <span
style="font-style: italic;"><br>
<span style="text-decoration: underline;">Organizational
honors</span></span><br>
</div>
</div>
<table summary="" style="text-align: left; width: 100%;"
cellspacing="2" cellpadding="2" border="0">
<tbody>
<tr>
<td style="vertical-align: middle; white-space:
nowrap;"> <big><span style="font-family:
sans-serif;">The Internet Archive</span><span
style="font-family: sans-serif;"><br>
<a href="http://archive.org"><small>www.archive.org</small></a><br>
</span></big></td>
<td style="text-align: center; vertical-align:
middle;"> <span style="text-decoration:
underline;"><a href="http://www.archive.org/"> <img
alt="" src="InternetArchive.jpg"
style="border: 0px solid;" width="97"
height="100" border="0"></a></span><br>
</td>
</tr>
</tbody>
</table>
<br>
<span style="font-style: italic; text-decoration:
underline;">Individual honors</span><br>
<ul>
<li>Don Eyles for preserving the AURORA 12 and SUNBURST
120 program listings, making them available to us, and
going to the effort of physically transporting them
for us.<br>
</li>
<li>Mike Stewart for financially sponsoring the scanning
of these programs, as well as doing all of the
background work needed to find them and figure out the
best way to get them scanned.</li>
<li>Our volunteer team, for transcribing the scanned
program listings into source code.<br>
</li>
</ul>
</td>
</tr>
</tbody>
</table>
</div>
<ul>
<li>Acquisition of RETREAD 50 (unflown) LM AGC software was a team
effort.</li>
</ul>
<div style="margin-left: 40px;">
<table summary="" style="text-align: left; margin-left: auto;
margin-right: auto;" cellspacing="2" cellpadding="2" border="1">
<tbody>
<tr>
<td style="vertical-align: top;">
<div style="text-align: center;"> <span
style="font-weight: bold;"><span
style="text-decoration: underline;">RETREAD 50 Honor
Roll</span><br>
</span>
<div style="text-align: left;"> <span
style="font-style: italic;"><br>
<span style="text-decoration: underline;">Organizational
honors</span></span><br>
</div>
</div>
<table summary="" style="text-align: left; width: 100%;"
cellspacing="2" cellpadding="2" border="0">
<tbody>
<tr>
<td style="vertical-align: middle; white-space:
nowrap;"> <big><span style="font-family:
sans-serif;">The Computer History Museum<br>
Mountain View, California<br>
</span><span style="font-family: sans-serif;"> <a
href="https://www.computerhistory.org/"><small>www.computerhistory.org</small></a><br>
</span></big></td>
<td style="text-align: center; vertical-align:
middle;"> <span style="text-decoration:
underline;"><a
href="https://www.computerhistory.org/"> </a><a
href="https://www.computerhistory.org/"><img
alt="" src="chm-logo.png" style="border: 0px
solid;" width="153" height="55" border="0"></a></span><br>
</td>
</tr>
</tbody>
</table>
<br>
<span style="font-style: italic; text-decoration:
underline;">Individual honors</span><br>
<ul>
<li>Jimmie Loocke, owner of AGC s/n RAY 14<br>
</li>
<li>AGC Restoration Core Team:</li>
<ul>
<li>Carl Claunch</li>
<li>Ken Shirriff</li>
<li>Mike Stewart</li>
<li>Marc Verdiell</li>
</ul>
<li>Auxiliary AGC Restoration Team Members:</li>
<ul>
<li>John Carlsen</li>
<li>Rob Lion<br>
</li>
</ul>
</ul>
</td>
</tr>
</tbody>
</table>
</div>
<ul>
<li>Thanks to Matteo Giani for figuring out how to get this beast
to compile in Mac OS X Panther.<br>
</li>
<li>Thanks to <a href="http://www.ibiblio.org">ibiblio.org</a>,
which began hosting the Virtual AGC project when my own meager
resources were exhausted. In latter days, The services of
<a href="http://archive.org">The Internet Archive</a> and <a
href="https://github.com">GitHub</a> have also become crucial.<br>
</li>
<li>Thanks to John Pultorak of <a href="Pultorak.html">Block I
AGC</a> fame. John has provided not only documentation
for his project that doesn't appear on the websites hosting his
other materials, but also has digitized many AGS-related
documents available nowhere else online (or not online, as far
as I can tell).</li>
<li>Thanks to Davis Peticolas, the donor for all of the scanned
AGS documents.</li>
<li>Thanks to Mark Grant and Markus Joachim for their work in
integrating Virtual AGC into the <span style="font-weight:
bold;">Orbiter</span> spacecraft simulator.</li>
<li>Thanks to Stephan Hotto for the enormous amount of code he has
contributed, and for finding various bugs in the simulation.</li>
<li>Thanks to my core developer team:</li>
<ul>
<li>Onno Hommes for stepping in to add many features to the
project, such as syntax highlighting, GUI debugging
interfaces, subversion repository, wiki, etc.</li>
<li>Jim Lawton especially but not exclusively for great
infrastructural improvements such as tying the project's
website to our GitHub repository and setting up
continuous-integration for the latter, along with many other
things.</li>
<li>Mike Stewart for using his hardware-based AGC simulator to
track down and fix many subtle, lingering bugs in our software
AGC simulator (and vice-versa), as well as a number of other
innovations.<br>
</li>
</ul>
<li>Thanks to Shelly Kelly, archivist at the University of Houston
at Clear Lake, for efforts (and patience) above and beyond the
call of duty, and particularly for some GSOP scans appearing on
our <a href="links.html">links page</a>.</li>
<li>Thanks to Jordan Slott, for implementing symbol tables into
the debugging mode of the AGC simulator.<br>
</li>
<li>And finally, thanks to my other correspondants who have
contributed in ways that don't necessarily fall into any of the
neat pigeonholes listed above. There are too many of you
to note adequately here, but I've tried to acknowledge you
throughout the website where your contributions are
relevant. If I've unfairly overlooked you, attribute it to
a 1201 alarm in my brain; let me know and I'll fix it.</li>
</ul>
<h2><a name="Solution_to_the_Apollo_14_Final_Exam"></a>Solution to
the Apollo 14 "Final Exam" Problem</h2>
Above, we semi-jokingly proposed as a <a
href="#Final_exam_for_the_advanced_student_">"final exam" problem</a>
a situation which actually occurred during Alan Shepard and Edgar
Mitchell's attempt to land the LM during the Apollo 14
mission. <a
href="http://www.hq.nasa.gov/alsj/a14/a14AbortDiscrete.html">Paul
Fjeld has provided a lot of detail about this at the Apollo Lunar
Surface Journal</a>, by consulting mission transcripts. Our
Onno Hommes has also gotten an explanation directly from Don Eyles,
the AGC developer who solved the final exam problem in real time
during the mission and, as far as I know, the only AGC coder ever to
be dramatized (in the Apollo 14 episode of <span style="font-style:
italic;">From the Earth to the Moon</span>). And <a
href="http://www.doneyles.com/LM/Tales.html">Don has written about
it himself</a> (among many other stories) pretty interestingly, in
a fairly popularized way. But here's the detailed solution,
in as nearly Don's words as we can make it:<br>
<br>
<table summary="" style="text-align: left; width: 75%; margin-left:
auto; margin-right: auto;" cellspacing="2" cellpadding="2"
border="1">
<tbody>
<tr>
<td style="vertical-align: top; background-color: rgb(204,
204, 204);"> The procedure developed to work around the
erroneous abort signal on Apollo 14 was as follows:<br>
<br>
(1) After the NOUN 62 countdown starts (an automatic display
of the countdown toward engine ignition), but before
ignition, key in<br>
<br>
<div style="margin-left: 40px;"> VERB 21 NOUN 1 ENTER 1010
ENTER<br>
107 ENTER<br>
</div>
<br>
to set the mode register to 71 to indicate that an abort had
already occurred. Note that the numbers are in
"octal" (i.e. based on the root of 8 not 10) so that the
number "107" actually means "71".<br>
<br>
(2) Exactly 26 seconds after ignition, manually advance the
descent engine throttle to 100%.<br>
<br>
(3) Key in<br>
<br>
<div style="margin-left: 40px;"> VERB 25 NOUN 7 ENTER 101
ENTER<br>
200 ENTER 1 ENTER<br>
</div>
<br>
to enable the landing guidance equations. The
equations were prevented from starting automatically because
the mode register is set to the phony value of 71.<br>
<br>
(4) Key in<br>
<br>
<div style="margin-left: 40px;"> VERB 25 NOUN 7 ENTER 105
ENTER<br>
400 ENTER 0 ENTER<br>
</div>
<br>
to explicitly disable the abort monitor. This clears the <span
class="e">FLAGWORD</span> bit that controls the abort
monitor.<br>
<br>
(5) Key in<br>
<br>
<div style="margin-left: 40px;"> VERB 21 NOUN 1 ENTER 1010
ENTER<br>
77 ENTER<br>
</div>
<br>
to set the mode register to its proper value of 63.<br>
<br>
(6) Return the manual throttle to its minimum
setting. The throttle stays at 100% because it is
now being commanded by the guidance
equations. But if this step were omitted the
throttle would be forced to stay at 100% when the guidance
equations later request partial thrust, with bad effects. </td>
</tr>
</tbody>
</table>
<br>
Of course, I bet it seems pretty obvious <span style="font-style:
italic;">now</span>, right? ... right?<br>
<br>
Nik Beug has made a YouTube video illustrating actual use of this
fix, using our AGC simulation built into the Orbiter spacecraft
simulator as part of <a
href="https://sourceforge.net/projects/nassp/">the NASSP project</a>.
The
video actually illustrates two scenarios:<br>
<ol>
<li>For the first couple of minutes, shows what would the actual
spurious abort have looked like. (Answer: It
separates the ascent and descent stages of the LM, and takes the
ascent stage back into orbit. You don't die, but you don't
land!)</li>
<li>The remainder of the video shows how to enter the fix, prevent
the spurious abort, and proceed to the surface.<br>
</li>
</ol>
Enjoy!<br>
<br>
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</iframe></center>
<br>
<br>
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<i><font size="-1">Last modified by <a
href="mailto:info@sandroid.org">Ronald Burkey</a> on
2021-05-26.<br>
<br>
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