Space shuttle avionics system

82 Pages·1989·4.769 MB·English

by  John F Hanaway, Robert W Moorehead

Space Shuttle
Avionics System
ORIGINALCONTAINS
COLORILLUSTRATIONS
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NASA SP-504
Space Shuttle
Avionics System
John F. Hanaway
Intermetrics, Inc.
Robert W. Moorehead
NASA Headquarters
National Aeronautics and Space Administration
Office of Management
Scientific and Technical Information Division
Washington, DC 1989
Library of Congress Cataloging-in-Publication Data
Hanaway, John F.
Space shuttle avionics system / John F. Hanaway, Robert W.
Moorehead.
p. cm. -- (NASA SP ;504)
Supt. of Docs. no. :NAS 1.21:504
1. Space shuttles--Electronic equipment. I. Moorehead, Robert
W. II. Title. III. Series.
TL3025.H36 1989
629.47--dc20 89-600316
CIP
For sale by the Superintendent of Documents,
U.S Government Printing Office, Washington, DC 20402
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Preface
HE SPACE SHUTTLE avionics system represents a functions was considered to be radical and of high risk.
significant advance in avionics system technology. The Prior to the Space Shuttle, aerospace systems were made
system was conceived in the early 1970's, developed up of an essentially independent collection of subsystems,
throughout that decade, and became operational in the organized along disciplinary lines such as flight control,
1980's. Yet even todayin _]988, it remains the most guidance and navigation, communications, and instrumen-
sophisticated, most advanced, most integrated avionics tation. Each subsystem typically had its own dedicated
system in operational use in the aerospace arena. Some controls, displays, and command and signal paths. The
of the more significant "firsts" achieved by the system Space Shuttle avionics system not only integrated the
include the following. computational requirements of all subsystems in one central
computer complex, but introduced the concept of
• It represents the frst successful attempt to incorporate
multifunction controls, displays, and command/data paths.
a comprehensive fail operational/fail safe concept in
The overall system design was driven by mission
an avionics system.
requirements and vehicle constraints never before encoun-
• It pioneered the development of complex redundancy tered in a space program. Significant among these were
management techniques, some of which rival the the following.
expert system approaches emerging today.
• The requirement for multiple reuse over a 20-year
• It isthe first operational aerospace system to use digital period -- The economic and safety-related impacts
data bus technology to perform flight-critical of aborting after one failure required that the system
functions. have a two-fault-tolerant fail operational/fail safe
configuration.
• It is the first operational system to utilize a high-order
language to develop and produce onboard software. • The requirement that comparison of data or
• It is the first operational aerospace program to make performance from independent systems or components
extensive use of flight software program overlays from operating in parallel be the primary means of detecting
and isolating failures and assessing system operational
a tape memory to expand the effective size of computer
status
memory.
-- To detect the second failure in a system, four parallel
• It is the first system to integrate the flight control
function with the rest of the avionics functions. strings were required and baselined.
--The use of built-in test was excluded wherever
• It included the first use of digital fly-by-wire technology
in an operational atmospheric flight application. possible as a less reliable fault isolation technique.
• It is the first avionics system to use a multifunction • The requirement for an unpowered landing on a
cathode-ray-tube display and crew interface approach. runway -- The stringent performance required
prohibited the use of degraded backup systems.
• It is the first avionics system to provide extensive
operational services to onboard nonavionics systems. • The autonomy requirement -- Large quantities of
instrumentation data, transmitted to the ground on
Such pioneering innovations and concepts are remark-
previous programs for spacecraft functional assess-
able in that they emerged in a design environment which
ment and subsystem management, had to be processed
would be considered archaic by today's standards. For
onboard and made available to the crew in usable
instance, the data processing state of the art has turned
forms.
over at least four times since the Space Shuttle design was
conceived. In 1974, there were no off-the-shelf microcom- • The Space Shuttle vehicle which evolved was an
puters, large-scale integrated-circuit technology was unstable airframe requiring sufficient control authority
emerging but immature, and the use of data buses for critical to cause structural failure if an erroneously applied
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SPACE SHUTTLE AVIONICS SYSTEM
hardover control actuator command was allowed to The Space Shuttle avionics system which evolved features
remain in effect for as little as 10 to 400 milliseconds. afive-computer central processing complex, which provides
software services to allvehicle subsystems that require them.
--Full-time stability augmentation was baselined,
Each computer isconnected to a network of 28 serial digital
direct control modes were excluded, and digital
data buses, which distribute input/output commands and
autopilots were designated to accommodate the
data to/from bus terminal units located throughout the
wide spectrum of control.
vehicle. Dedicated hardware components, unique to the
-- Manual intervention or switching of active/standby various subsystems, interface as necessary with bus terminal
strings proved inadequate to overcome the effects unit signal conditioning devices. During critical mission
of erroneous hardover commands; therefore, a phases such as ascent and entry, the system is configured
system approach was baselined in which hardovers in four redundant, independent but synchronized strings,
were prevented through the use of multiple, parallel- each controlling one-fourth of the redundant sensors and
operating, synchronized processors and command control effectors required for the operation in progress.
paths to drive force-summing control actuators. A backup, simplex software package is installed in the fifth
computer to be used if a generic error causes failure of
• The large size of the Space Shuttle vehicle resulted
the total redundant set. During more benign mission phases
in the weight of wire, both signal and power, being
such as on-orbit, the computer complex can be configured,
a significant proportion of the avionics system weight.
by loading the appropriate software programs, to perform
-- Multiplexed serial digital data buses were used for a wide variety of mission and payload support functions.
command and data transmission throughout the The system includes more than 270 components,
vehicle. depending on the mission, and uses approximately 500 000
lines of software code. Although very complex and difficult
-- Solid-state remote power control devices were used
to describe or understand, the system has proven to be
to reduce the quantity of power cable needed.
reliable, durable, extremely versatile, and a tribute to the
A myriad of other mission, vehicle, and system require- multitudes who contributed to its design, development, and
ments influenced or dictated various aspects of the design; verification.
however, the basic system concepts were derived from those
described.
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Contents
Section
Page
I INTRODUCTION
Purpose of Document ..................................................................... i
Organization ............................................................................. 1
Use ....... .............................................................................. I
THE DESIGN ENVIRONMENT
Introduction ............................................................................. 3
Avionics Hardware/Software ............................................................... 3
Flight Control ............................................................................ 3
Guidance and Navigation .................................................................. 4
Displays and Controls ..................................................................... 4
Communications and Tracking ............................................................. 4
Redundancy Management .................................................................. 4
3 SYSTEM DESIGN EVOLUTION
Introduction ............................................................................. 5
Top-Level Design Drivers/Requirements ..................................................... 5
Data Processing .......................................................................... 9
Flight Control ............................................................................ l0
Backup System ........................................................................... 12
Redundancy Management .................................................................. 12
Onboard System Management .............................................................. 13
Navigation ............................................................................... 15
Display and Control ....................................................................... 17
Communications .......................................................................... 17
USAF Requirements ...................................................................... 19
Payload Support .......................................................................... 19
Remote Manipulator ...................................................................... 20
Power Distribution ........................................................................ 20
SYSTEM MECHANIZATION/OPERATION
Overview ................................................................................ 21
Avionics System Functions ................................................................. 22
Data Processing .......................................................................... 25
Display and Control ....................................................................... 35
Guidance, Navigation, and Control .......................................................... 38
Sequencing .............................................................................. 45
System Management/Instrumentation ....................................................... 47
Communications and Tracking ............................................................. 49
Payload Support Operations ............................................................... 54
Electrical Power Distribution and Control .................................................... 56
Ground Checkout ......................................................................... 59
APPENDIX -- ACRONYMS/ABBREVIATIONS ..................................................... 61
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SPACE SHUTTLE AVIONICS SYSTEM
Tables
Table Page
4-1 Data Bus Utilization ...................................................................... 30
39
4-II Guidance, Navigation, and Control Elements .................................................
Figures
Page
Figure
3-1 Elevon failure effects ...................................................................... 6
3-2 Four-port actuator ........................................................................ 7
3-3 Baseline system approach .................................................................. 7
3-4 Active/standby approach .................................................................. 8
3-5 Parallel string approach ................................................................... 9
3-6 System management approaches ............................................................ 14
3-7 Skewed IMU approach .................................................................... 15
4-1 Avionics equipment locations ............................................................... 21
4-2 Avionics functional categories .............................................................. 22
4-3 Ascent control effectors .................................................................... 23
4-4 Ascent trajectory ......................................................................... 23
24
4-5 Entry trajectory ..........................................................................
4-6 Terminal area energy management .......................................................... 25
4-7 Final approach ........................................................................... 25
26
4-8 Listen mode .............................................................................
4-9 Memory configurations .................................................................... 27
4-10 OPS substructure ......................................................................... 27
4-11 Software architecture ...................................................................... 28
4-12 GPC memory configuration ................................................................ 28
29
4-13 Data bus characteristics ...................................................................
29
4-14 Data bus message formats .................................................................
4-15 Data bus architecture ..................................................................... 30
4-16 Multiplexer/demultiplexer block diagram .................................................... 31
4-17 Master events controller ................................................................... 32
4-18 Engine interface unit ...................................................................... 33
34
4-19 Annunciator display unit ..................................................................
35
4-20 Data bus control .........................................................................
4-21 Forward flight deck ....................................................................... 36
4-22 Aft flight deck ............................................................................ 37
4-23 Display and control block diagram .......................................................... 38
4-24 GN&C RM configuration .................................................................. 40
4-25 Air data system ........................................................................... 41
4-26 GN&C actuator configuration .............................................................. 42
43
4-27 Typical hydraulic actuator drive ............................................................
4-28 Main engine throttle control ................................................................ 44
4-29 RCS configuration ........................................................................ 45
4-30 OMS configuration ....................................................................... 46
4-31 Sequencing configuration .................................................................. 46
4-32 Instrumentation system .................................................................... 47
4-33 System management configuration .......................................................... 48
4-34 Orbital communication links ............................................................... 49
4-35 Atmospheric flight links ................................................................... 49
4-36 Hardware groupings ...................................................................... 50
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CONTENTS
Page
Figure
4-37 Antenna locations ............................................................ 50
4-38 S-band network equipment ...................................................... 51
4-39 S-band network services ........................................................ 52
4-40 S-band payload communications .................................................. 52
4-41 Ku-band radar/communication subsystem ........................................... 53
4-42 Audio distribution system ....................................................... 54
4-43 Navigation aids .............................................................. 54
4-44 Payload interfaces ............................................................ 55
4-45 Electrical power system (single string) .............................................. 57
4-46 Essential bus distribution (one of three) ............................................. 58
4-47 Control buses ............................................................... 59
4-48 Checkout configuration ........................................................ 59
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