Space Shuttle Data Processing System. Digital Processing System - General The Orbiter functions and...

Space Shuttle Data Processing

System

Digital Processing System - GeneralDigital Processing System - General

The Orbiter functions and operations are managed by a The Orbiter functions and operations are managed by a computerized data management and processing system computerized data management and processing system called the Data Processing System (DPS)called the Data Processing System (DPS)

Primary data management is provided by five identical Primary data management is provided by five identical digital computers running in parallel for redundancydigital computers running in parallel for redundancy

Secondary data management is furnished by a network of Secondary data management is furnished by a network of 24 computerized digital system management units called 24 computerized digital system management units called Multiplexers/Demultiplexers (MDMs)Multiplexers/Demultiplexers (MDMs)

Two dedicated critical event control units supply signal Two dedicated critical event control units supply signal and data management for launch, orbit, deorbit, and and data management for launch, orbit, deorbit, and landing phases of the STS and Orbiterlanding phases of the STS and Orbiter

Two command and data storage tape units are also Two command and data storage tape units are also provided for multiple-redundant operational informationprovided for multiple-redundant operational information

DPS

Key DPS equipment on the Orbiter

5 General Purpose Computers (GPCs)

24 (20 Orbiter, 4 SRB) Multiplexers/Demultiplexers (MDMs)

2 master events controllers

2 Mass Memory Units (MMUs)

24 Serial digital data buses

3 SSME interface units

4 multifunction CRT display systems (MCDS)

2 data bus isolation amplifiers

1 Master timing unit (MTU)

DPS functional block diagram

General Purpose Computers (GPCs)

DPS - General Purpose Computers

IBM was awarded the development contract for the STS data processing and integration and for the KSC launch processing system, and for the JSC mission control center data processing

IBM was chosen for its integrated software capability for data management on the STS Vehicle processing Prelaunch and launch Orbital flight Landing

Software modifications and changes required for each mission were simplified by developing the digital data systems through the same primary contractor


Off-the-shelf components were emphasized for reliability and rapid integration into the STS

An existing model of IBM's AP-101 32-bit computer was adopted

GPC processor was a modified IBM System/4 Pi Initially used as central processor in earlier B-52

digital systems and later in the B-1 bomber

Included an assembly language-based software called High-order Assembly Language/Shuttle (HAL/S)


GPC is divided into two major components

Central Processor Unit (CPU) CPU provides control logic and computational capabilities

Input/Output Processor (IOP) IOP provides control and interface links between the CPU

and the hardware that interfaces with the GPCs

Both the CPU and the IOP contain software and memory for data storage

GPC Schematic


Basic functions

CPU Instruction execution Data storage Data manipulation

Input/Output Processor Formats and transmits commands to vehicle systems Receives and validates data from the vehicle systems Maintains interface status with the associated CPU and with

the other GPCs Interfaces the DPS 24 data buses with its 24 processors


Weight 30.8 kg (68 lb)

Power consumption ~ 560 W

Power source Any Main Bus

Any Essential Bus

Software Four GPCs contain PASS software (GPC 1-4)

Output polling used to determine if any of the GPCs or their computations are in error

GPC #5 runs BFS software Does not participate in the polling/voting process Used for backup control of the vehicle if the PASS

software fails or malfunctions


External mass memory is employed to overcome the inherently small main memory available to the CPU and IOP

128 k of main memory severely restricts the vehicle operations Requires a segmented approach to the GPC's control of the

mission operations

Mission sequences are loaded into the GPC's main memory from the redundant mass memory storage units

This technique allows the entire mission execution but only in sequential bundles


GPC main memory

Originally a ferrite core construction like Apollo guidance computers Small, individual wire-wound

iron ring for each bit

Total of 128 k capacity (half) words was later increased to 256 K by bit manipulation

Original limitation was due to the memory's large mass, high power requirement, and GPC heat load


Timer/oscillator

GPC's timer/oscillator is used to generate signal timing for pacing the data processing cycles

Also used to determine absolute time reference

Two time references are maintained for the GPC's operations. GMT - Greenwich Mean Time MET - Mission Elapsed Time A watchdog timer is also used in the GPCs to

check on the timing register for the BFS software operations

DPS - GPC

GPC panel switchesCrew operation of the GPCs is controlled with panel switches on the GPC panel

POWER (ON/OFF)

OUTPUT (BACKUP / NORMAL / TERMINATE)

INITIAL PROGRAM LOAD

MODE (RUN / STBY / HALT)

Mass Memory Units

DPS – Mass Memory Units

MMUs

Two mass memory units (MMUs) are aboard each Orbiter

Coaxially mounted, reel-to-reel read/write digital magnetic tape storage device for GPC software and Orbiter systems data

Each of the tape systems has a capacity of 34 Mb and stores three copies of the flight software

DPS – Mass Memory Units

The principal function of the MMU is to store the basic flight software

Secondary function is to store background formats and code for certain CRT displays and the checkpoints that are written periodically to save selected data in case the systems management GPC fails

Each mass memory data bus is connected to all five computers But each MMU is connected to only one mass memory

data bus

All MMU operations are on an on-demand basis only

Data Bus Network

DPS – Data Bus Network

Data flow in the Orbiter’s DPS systems is supported 24 data buses categorized in 7 groups

1. Flight-critical (FC) data buses (8)

2. Payload data buses (2)

3. Launch data buses (2)

4. Mass memory data buses (2)

5. Display/keyboard data buses (4)

6. Instrumentation/Pulse Code Modulation Master Unit (PCMMU) data buses (5)

7. Intercomputer communication data buses (5)


1. Flight-critical (FC) data buses (8)

FC buses tie the GPCs to: Flight-critical multiplexer/demultiplexers (MDMs) Display driver units Heads-up displays Engine interface units Master events controllers

Eight flight critical data buses combined into groups of two (FC strings) for redundancy

Each of the four FC strings can be commanded by a different GPC Group 1 FC1, FC2, FC3, FC4 Group 2 FC5, FC6, FC7, FC8


2. Payload data buses (2)

These buses tie the GPCs to the payload MDMs and the payload data interleaver (PDI)

In some configurations these are mission-dependent flex MDMs or sequence control assemblies

Two buses interface 5 GPCs and 2 payload MDMs


3. Launch data buses (2)

These buses tie the GPCs to ground support equipment, launch forward MDMs, launch aft MDMs, launch mid MDMs, SRB MDMs, and the manipulator controller interface unit (MCIU) used by the remote manipulator system

Two launch data buses are used to interconnect the following: 5 GPCs Ground support equipment Launch processing system 3 Launch MDMs 2 (left & right) SRB MDMs


4. Mass memory data buses (2)

The mass memory data buses are used for GPC - Mass Memory Unit transactions

Both mass memory data buses are interconnected with each GPC


5. Display/keyboard data buses (4)

Used for GPC/display electronics data transactions

Each of the four display electronics units are interconnected to each of the GPCs through the Display/keyboard data buses


6. Instrumentation/Pulse Code Modulation Master Unit (PCMMU) data buses (5)

Each of the GPCs is interconnected to two of the I/PCMMUs


7. Intercomputer communication data buses (5)

Five intercomputer communication (IC) data buses exchange information that includes:

Input/output errors Fault messages GPC status matrix data Display electronics unit major function switch settings GPC CRT keyboard entries Resident GPC memory configuration Memory configuration tables Operational sequences Master timing unit data Time Internal GPC time System-level display information Uplink data State vectors


With the exception of the Instrumentation/PCMMU, each data bus is connected to each GPC, but only one GPC transmits over a bus at any one time

Multiplexers/Demultiplexers (MDMs)

DPS – MDMs

MDMs act as system management units that convert and format serial digital GPC commands into separate and parallel (demultiplexed) digital, and analog commands for various vehicle hardware systems

MDMs also convert and format the multiple digital, and analog data from vehicle systems into serial (multiplexed) digital data for transmission to the GPCs

Each MDM has two redundant multiplexer interface adapters which are connected to a separate data bus on the GPC side

MDM's interface with vehicle system hardware is by hard-wired lines

DPS – MDMs

Each Orbiter carries 23 multiplexers/demultiplexers onboard

Sixteen MDMs are an integral part of the DPS, connected directly to the GPCs and named according to their location in the vehicle and hardware interface

Remaining seven MDMs are part of the vehicle instrumentation system

Send vehicle instrumentation data to the pulse code modulation master unit

DPS – MDMs

The data processing system MDMs consist of: Flight-critical forward MDMs 1 through 4 Flight-critical aft MDMs 1 through 4 Payload MDMs 1 and 2 SRB launch left MDMs 1 and 2 SRB launch right MDMs 1 and 2 GSE/LPS launch forward 1 and launch aft 1

Software

DPS – Software

Data Processing System software is divided into two functional groups

1. System software

2. Applications software

Both are further subdivided into operations functions

Primary Orbiter flight software Called the Primary Avionics Software System (PASS) software Used to control the vehicle, vehicle systems, and

communications during its mission

Second flight software program runs on a separate GPC as a backup for critical operations Called the Backup Flight System (BFS)

DPS – Software

System software consists of three program sets

1. Flight Computer Operating System (FCOS) This is the executive software that controls the

processors, monitors key system parameters, allocates computer resources, manages program interrupts, and updates computer memory

2. User interface programs These provide instructions for processing flight crew

commands or requests

3. System control program These initialize each GPC and arrange for multi-GPC

operation during flight-critical phases

DPS – Software

Applications software performs the functions required to operate the vehicle and its systems

To conserve main memory, the applications soft-ware is divided into three major functions

1. Guidance, navigation, and control (GNC)

2. Systems management (SM)

3. Payload (PL)

DPS – Software

Applications software

1. Guidance, navigation, and control (GNC)

Specific software required for launch, ascent to orbit, maneuvering in orbit, entry, and landing

Only major function where redundant set synchronization occurs

Polling circuitry used to evaluate GPC output/calculations in synchronization

DPS – Software


2. Systems management (SM)

This software executes tasks that monitor various orbiter systems, such as life support, thermal control, communications, and payload operations

SM is a simplex function The DPS simplex operations use a watchdog

timer to evaluate self-consistent results

DPS – Software


3. Payload (PL)

The payload major function runs mass memory utility software

Because the PL major function is usually unsupported in flight, none of the GPCs are loaded with PL software

Only used in vehicle preprocessing at KSC, and is a simplex major function

DPS – Software

Applications softwareApplications software

Applications software major functions are Applications software major functions are divided into mission segments called divided into mission segments called OPerational Sequences, or OPerational Sequences, or OPSOPS

Each Each OPS Major ModeOPS Major Mode is associated with a is associated with a specific memory configuration loaded into the specific memory configuration loaded into the GPCs from the MMUs GPCs from the MMUs

DPS – Software


All of the software residing in a GPC at any given time consists of system software and one OPS major mode software

Except for OPS 1, each memory configuration contains a single OPS major mode Memory configuration OPS 1 which is

loaded for countdown and launch contains both OPS 1 (ascent) and OPS 6 (RTLS) major modes

Too little time to load in new software for a critical RTLS abort

DPS – Software

DPS – Software OPS-1 Major Modes

DPS – Software

Backup Flight System (BFS)Backup Flight System (BFS)

Backup Flight System software is an entirely Backup Flight System software is an entirely separate DPS software package maintained on separate DPS software package maintained on the Orbiter's fifth GPCthe Orbiter's fifth GPC GPC selection for BFS operation can be GPC selection for BFS operation can be

changed manually with panel switcheschanged manually with panel switches

BFS flight software mimics the PASS software BFS flight software mimics the PASS software for the mission-critical operations (OPS 1, OPS for the mission-critical operations (OPS 1, OPS 3 and OPS 6)3 and OPS 6) Contains notable differencesContains notable differences

DPS – Software

Backup Flight System (BFS)

BFS software is written by a different vendor Also in the HAL/S language

BFS software is simpler than the PASS software since it is used for contingencies in the mission; the critical phases of flight Smaller size of the BFS software allows it to be

loaded completely into one GPC for the entire mission and does not require sequential loading

Copies of the BFS are contained on both of the MMUs

DPS – Software


BFS software is programmed to monitor the state of the GPC and PASS operations so that it would be possible to take control of the vehicle if the PASS software to malfunction

Like PASS, the BFS includes both applications software and system software

Unlike PASS software, BFS is small enough to run both applications and systems application simultaneously

DPS – Software


System functions on the BFS include Time-keeping PASS/BFS interface Multifunction CRT display system operations GPC I/O Communications uplink and downlink

DPS – Software


BFS software can be selected with the engage and disengage control switch on the hand conroller BFS can take over control of the vehicle by

pressing the engage button on the top of the flight crew's rotational hand controllers

BFS also executes system management software (SM) in simplex during ascent and entry since the other four GPCs running PASS software are operating in GNC in redundant set synchronization

BFS provides only limited support for on-orbit operations via MM 106 or MM 301

References

Shuttle Crew Operations Manual - Digital Processing System (DPS), NASA

National Space Transportation System Press Kit, NASA, 1998

Space Shuttle Data Processing System. Digital Processing System - General The Orbiter functions and...

Documents

Transcript of Space Shuttle Data Processing System. Digital Processing System - General The Orbiter functions and...