MIT's Role In Project Apollo Volume III

296 Pages·2002·10.55 MB·English

GWDANCE, NAVIGATION
AND CONTROL
Dat2T
Approved
Q& '4 U -$
Approved ) a . Date2 7 'c
R. R. RAGAN, DEPUTY DlRECTW
THE CHARLES STARK DRAPER LABORATORY
-
R 700
MIT's ROLE IN PROJECT APOLLO
FINAL REPORT ON CONTRACTS
NAS 9-16 3 AND NAS 94065
VOLUME 111
COMPUTER SUBSYSTEM
by
ELOON C. HALL
AUGUST 1972
M m W
CHARLES STARK DRAPER
LABORATORY
CAMBRIDGE, MASSACHUSETTS, 02139
ACKNOWLEDGNIENTS
This report was prepared under DSR Project 55-23890, sponsored by the Manned
Spacecraft Center of the National Aeronautics and Space Administration through
Contract NAS9-4065.
The author expresses appreciation to many individuals within Draper Laboratory
who contributed to the following sections of the report. In particular:
A. Hopkins Section 1, 2
A. Green, R. Filene Section 4
A. Harano Section 5
D. Bowler' Section 6
D. Hanley, J. Partridge Section 7.
The publication of this document does not constitute approval by the National
Aeronautics and Space Administration of the findings or conclusions contained
herein. It is published for the exchange and stimulation of ideas.
Q Copyright by the Massachusetts Institute of Technology
Published by the Charles Stark Draper Laboratory of the
Massachusetts Institute of Technology .,
Printed in;C ambridge, Massachusetts, U .S .A 1972
ii
FOREWORD
The title of these volumes, "MIT's Role in Project Apollo", provides but a
modest hint of the enormous range of accomplishments by the staff of this Laboratory
on behalf of the Apollo program. Man's rush into spaceflight during the 1960s
demanded fertile imagination, bold pragmatism, and creative extensions of existing
technologies in a myriad of fields, The achievements in guidance and control for
space navigation, however, are second to none for their critical importance in the
success of this nation's manned lunar-landing program, for while powerful space
vehicles and rockets provide the environment and thrust necessary for space flight,
they are intrinsically incapable of controlling or guiding themselves on a mission
as complicated and sophisticated as Apollo. The great achievement of this Laboratory
was to supply the design for the primary hardware and software necessary to solve
the Apollo guidance, navigation and control problem. It is to the credit of the entire
team that this hardware and software have performed so dependably throughout the
. .
Apollo program.
The quantum leap in technology nurtured by the Apollo program has been and
should continue to be of immensely significant benefit to this country-socially,
economically and in terms of its national esteem. It is the responsibility of all
those who contributed to the proud achievements of Apqllo to convince their
countrymenof the directions thisnation ought to follow in implementing these newly
gained-and hard fought for-advances.
C. Stark Draper, President
Charles Stark Draper Laboratory

R-700
P POL LO
MITIS ROLE IN PROJECT
Final Report on Contracts
NAS9-153 and NAS9-4065
VOLUME 111
COMPUTER SUBSYSTEM
ABSTRACT
The Apollo guidance computer (AGC) is a real-time digital-control computer whose
conception and development took place in the early part of 1960. The computer
may be classified as a parallel, general-purpose or whole number binary computer.
This class of computer is representative of most of the ground-based digital
computers in existence in the late 1950s, when the precursers of the AGC were
being designed. However, at that time few computers of this class had been designed
for the aerospace environment, and those few embodied substantial compromises
in performance for the sake of conserving space, weight, and power. The design of
the AGC capitalized on advancements in digital computer technology in order to
provide significant improvements in computational performance and still conserve
space, weight and power,
The AGC is the control and processing center of the Apollo Guidance, Navigation
and Control system. It processes data and issues discrete output and control pulses
to the guidance system and other spacecraft systems, An operational Apollo
spacecraft contains two guidance computers and three DSKYs (keyboard and display
unit for operator interface), with one computer and two DSKYs in the command
module, and one of each in the lunar module. The computers are electrically identical,
but differ in the use of computer software and interface control functions. As a
control computer, some of the major functions are: alignment of the inertial
measurement unit, processing of radar data, management of astronaut display and
controls and generation of commands for spacecraft engine control, As a general
purpose computer, the AGC solves the guidance and navigation equations required
for the lunar mission.
*
The operational experience in the Apollo guidance systems includes 20 computers
which flew missions and another 25 flight type computers which are still in various
phases of prelaunch activity including storage, system checkout, prelaunch spacecraft
checkout, etc. These computers were manufactured and maintained under very strict
quality control procedures with requirements for reporting and analyzing all
indications of failure. Probably no other computer or electronic equipment with
equivalent complexity has been as well monitored and documented. Since it has
demonstrated a unique reliability history, it is important to record the technique
and methods which have contributed to this history.
by Eldon C. Hall
August 1972
.I_ The operational experience includes missions through Apollo 15 which flew in
'
August of 1971. Three B1 I and one B1 I1 computers flew in unmanned missions.
Sixteen B1 I1 computers flew manned missions.
vi
CONTENTS
Section P.age
. . . . . . . . . . . . . . . . . . . . . . . . . .
Acknowledgments ii
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Foreword iii
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Abstract v
. . . . . . . . . . . . . . . . . . . . . . . . . .
List of Illustrations xv
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Preface 1
. . . . . . . . . . . . . . . . .
1.0 SUBSYSTEM DEVELOPMENT 3
. . . . . . . . . . .
1.1 Evolution of the Computer Subsystem 3
. . . . . . . . . . . . . . . . . . . .
1.2 Initial Decisions 15
. . . . . . . . . . . . . . . .
1.3 Expanding Requirements 19
. . . . . . . . . . .
1.3.1 Memory Size (1962 to 1969) 19
- . . . . . . . . .
1.3.2 Implementation Meetings 1964 20
. . . . . . . . . .
1.3.3 Weight Savings (1962 to 1965) 20
- .
1.3.4 Electromagnetic Interference Specifications 1963 21
- . . . . . . . . . . . . . .
1.3.5 Fire Proofing 1967 21
. . . . . . . . . . . . . .
2.0 COMPUTER SYSTEM DESCRIPTION 23
. . . . . . . . . . . . . . . . . . . . . .
2.1 Introduction 23
. . . . . . . . . . . . .
2.2 General Functional Description 29
. . . . . . . . . . . . . . . . . . .
2.2.1 Computer 29
. . . . . . . . . . . . . .
2.2.2 Display and Keyboard 29
. . . . . . . . . . . . . . . .
2.3 Subsystem Characteristic 32
. . . . . . . . . . . . . . . . . .
2.3.1 WordLength 32
. . . . . . . . . . . . .
2.3.2 Number Representation 35
- . . . . . . . . .
2.3.3 Multiple Precision Arithmetic 37
. . . . . . . . . . . . . . . . .
2.3.4 Instruction Set . 38
. . . . . . . . . . . .
2.3.5 Timing and Priority Control 46
. . . . . . . . . . . . . . . . . . . .
2.3.6 Memory 46
~
vii
CONTENTS (Cont)
Section Page
. . . . . . . . . . . . . . . . . .
2.3.7 Input/Output 47
. . . . . . . . . . . . . . . .
2.3.8 Standby Operation 48
. . . . . . . . . . . . . .
2.3.9 DSKY Characteristics 48
. . . . . . . . . . . . .
2.4 Computer Mechanical Description 51 .
. . . . . . . . . . . . . .
2.5 DSKY Mechanical Description 53
. . . . . . . . . . . . . . .
3.0 COMPUTER DESIGN DESCRIPTION 55
. . . . . . . . . . . . . . . . . . . . . . .
3.1 Introduction 55
. . . . . . . . . . . . . . . . . . . . . .
3.2 Logic Design 61
. . . . . . . . . . . . . .
3.2.1 Logic Circuit Element 61
. . . . . . . . . . .
3.2.2 Logic Timing and Sequencing 63
. . . . . . . . . . . . . . . .
3.2.3 Central Processor 67
. . . . . . . . .
3.2.4 Address and Instruction Decoding 71
. . . . . . . . . . . . . . .
3.2.5 Interrupt Structure 71
. . . . . . . . . . .
3.2.5.1 Counter Interrupts 77
. . . . . . . . . .
3.2.5.2 Program Interrupts 80
. . . . . . . . . . . . . . . . . . . .
3.3 Oscillator Circuit 82
. . . . . . . . . . . . . . . . . . . . .
3.4 Power Supplies 83
. . . . . . . . . . . . . . . . . . . .
3.5 Memory Circuits 85
. . . . . . . . . . . . . . . .
3.5.1 Erasable Memory 87
. . . . . . . . . . . . . . . . .
3.5.2 Fixed Memory 91
. . . . . . . . . . . . . . .
3.6 Alarms and Fault Detection 93
. . . . . . . . . . . . . . . . . . . .
3.7 Interface Methods 97
. . . . . . . . . . . . . . . . . . . .
3.7.1 Circuits 101
. . . . . . . . . . . . .
3.7.2 Data Format Conversion 101
. . . . . . . . . . . . . . . .
3.7.3 Interface Example 103
. . . . . . . . . . . . . . . . . . . .
3.8 DSKY Description 107
. . . . . . . . . . . . .
3.9 Computer Mechanical Description 115
. . . . . . . . . . . . . . .
3.9.1 Detailed Description 117
. . . . . . . .
3.9.1.1 Tray A Wired Assembly 117
. . . . . . . .
3.9.1.2 Tray B Wired Assembly 121
. . . .
3.9.1.3 Interconnection Header Assembly 123
. . . . . .
3.9.1.4 Mid-Spacer and Tray Covers 123 .
. . . . . .
3.9.1.5 Module Construction Features 123
. . . . . . . . . . .
3.9.1.6 Assembly Features 125
. . . . . . . . . . . .
3.9.1.7 Thermal Design 130 .w
.
viii
CONTENTS (Cont)
Page
Section
. .
3.10 Display and Keyboard Unit (DSKY) Mechanical Description 131
. . . . . . . . . . . . . . .
3.10.1 Detailed Description 133
. . . . . . . .
3.10.1.1 Front Housing Assembly 133
. . . . . . . . .
3.10.1.2 Main Housing Assembly 136
. .
3.10.1.3 Alarm Indicator and Cover Assembly 140
. .
3.10.1.4 Digital Indicator and Cover Assembly 145
. . . . . . . . . . .
3.10.1.5 Pushbutton Switch 149
. . . . . . . . . . . . . . . . . . . .
4.0 COMPUTER SOFTWARE 151
. . . . . . . . . . . . . . . . . . . . . . .
4.1 Introduction 151
. . . . . . . . . . . . . . . . . . . . .
4.2 Utility Programs 155
. . . . . . . . . . . . . . . . . . .
4.2.1 Interpreter 155
. . . . . . . . . . . . . . . . . . . .
4.2.2 Executive 157
. . . . . . . . . . . . . . . . . . . .
4.2.3 Waitlist 157
. . . . . . . . . . . . . . . . . .
4.3 Display and Keyboard 158
. . . . . . .
4.4 Development of Computer Self-check Program 159
. . . . . . . . . . . . . . . .
4.4.1 Block I Versions 159
. . . . . . . . . . . . . . . . .
4.4.1.1 Eclipse 159
. . . . . . . . . . . . . . . .
4.4.1.2 Sunrise 159
. . . . . . . . .
4.4.1.3 Final Block I Version 162
. . . . . . . . . . . . . .
4.4.2 SELFCHK in Block I1 163
. . . . . . . . . . . . . . . . . . .
4.5 Factory Test Ropes 163
. . . . . . . . . . . . . . . .
4.6 Fixed Memory Fabrication 165
. . . . . . . . . . . . . . . .
4.6.1 Program Release 165
. . . . . . . . . . . . .
4.6.2 Module Data Verification 165
. . . . . . . . . . . . . . . .
5.0 GROUND SUPPORT EQUIPMEiQT 169
. . . . . . . . . . . . . . . . . . . . . . .
5.1 Introduction 169
. . . . . . . . . . . . . . . . . . .
5.2 Development of GSE 169
. . . . . . . . . . . . . . . . . . . .
5.2.1 Monitor 171
. . . . . . . . . . . . . .
5.2.2 Interface Test Console 171
. . . . . . . . . . . .
5.2.3 Portable Monitor (Block I) 172'
. . . . . . . . . . . . . .
5.2.4 "Blue Box" (Block 11) 172
. . . . . . . . . . . . . . . . .
5.2.5 Restart Monitor 173
. . . . . . . . . .
5.3 Development of Software Checkout Aids 173
. . . . . . . . . . . . . .
5.3.1 Core Rope Simulators 173
. . . . . . . . . . . . .
5.3.1.1 AGC Monitor 174
ix
CONTENTS (Cont)
Section Page
. . . . . . . . . . . . . . .
5.3.1.2 Portafam 175
. . . . . . . . . . . . . . .
5.3.2 Interface Simulators 176
. . . . . .
5.3.2.1 Interface Test Console (ITC) 176
. . . . . . .
5.3.2.2 Uplink-Downlink Exercisers 177
. . . . . . . . . . . . . . . . . .
5.3.3 Trace System 177
. . . . . . . .
5.3.3.1 Coroner Characteristics 177
. . . . . . . .
5.3.3.2 Trace Analytical Software 179
. . . . . . . . . . . . . . . . . . . .
6.0 SYSTEMS INTEGRATION 181
. . . . . . . . . . . . . . . . . . . . . . .
6.1 Introduction 181
. . . . . . . . .
6.2 Development and Specification of Interface 182
. . . . . . . . . . . . . . . . . .
6.2.1 Circuit Types 185
-
.
6.2.1.1 Transformer Coupled Interface Circuits 187
6.2.1.1.3 Transformer . Coupled
. .
Output Circuit (X Circuit) 187
6.2.1.1.2 Transformer . Coupled
. .
Input Circuit (Y Circuit) 189 .
. . . .
6.2.1.2 Direct Coupled Interface Circuits 189
6.2.1.2.1 DC Output Circuit (C Circuit) 189
.
6.2.1.2.2 DC Input Circuit (D Circuit) 191
. . . . . . . . . . . .
6.2.1.3 Special Circuits 193
. .
6.2.1.3.1 Hand Controller Interface 193
. . . .
6.2.1.3.2 DC Power Interface 195
. . . . . . . .
6.2.2 Interface Control Documents (ICD's) 196
. . . . . . . . . . . . . . . . . . . .
6.2.3 Summary 196
. . . . . . . . . . . . . . .
6.3 Electromagnetic Interference 197
. . . . . . . . . . . . . . . . .
6.3.1 EM1 Philosophy 197
. . . . . . . . . . . . . . . . . . .
6.3.2 Milestones 198
. . . . . . . . . . . . . .
6.3.3 Specification Problem 200
. . . . . . . . . .
6.3.3.1 Susceptibility Testing 200
6.3.3.1.1 Power Line Transient
. . . . . . .
Susceptibility 200
6.3.3.1.2 Conducted Audio Suscepti-
. . . . . . . . . . .
bility 201 .
.
6.3.3.1.3 Radiated Susceptibility 201
91
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