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Avionics

Overview
Controls, or assists in controlling, most of the shuttle systems.
Data Processing System
The vehicle relies on computerized control and monitoring for successful performance.
Software
DPS software is divided into two major groups: system software and applications software.
General-Purpose Computers
Five identical computers aboard the orbiter control vehicle systems.
Mass Memory Units
Computing functions for all mission phases requires about 400,000 words of computer memory.
Multifunction CRT Display System
Displays on the flight deck allow onboard monitoring of systems, software processing and manual control for crew data and software manipulation.
Master Timing Unit
The GPC complex requires an accurate time source because its software uses GMT to schedule processing.
Computer Data Bus Network
Network is divided into specific groups that perform specific functions.
Multiplexers/Demultiplexers
DPS MDMs convert and format serial digital GPC commands into separate commands for various vehicle system hardware.
Master Events Controllers
Send signalls to arm and safe pyrotechnics during SRB/ET separation.
Data Bus Isolation Amplifiers
Interfacing devices for the GSE/LPS and SRB MDMs.
Backup Flight Control
The fifth GPC, loaded with different software, provides backup in case primary GPCs fail.
Guidance, Navigation and Control
GNC software commands effect vehicle control and provide sensor data needed to compute these commands.
Flight Control System Hardware
Hard-wired to one of eight flight-critical MDMs.
Navigational Aids
Include IMUS, tacan units, air data probe assemblies, and more.
Inertial Measurement Units
Consist of an all-attitude, four-gimbal, inertially stabilized platform.
Star Trackers
Two star tracker units are part of the navigation system.
Crewman Optical Alignment Sight
Used if IMU alignment is in error more than 1.4 degrees.
TACAN
Determine slant range and magnetic bearing to ground station.
Air Data System
Provides information on the movement of the orbiter in the air mass.
Microwave Scan Beam Landing System
Used during landing phase to determine slant range, azimuth and elevation to landing runway.
Radar Altimeter
Measure absolute altitude from the orbiter to nearest terrain within beamwidth of orbiter's antennas.
Accelerometer Assemblies
Sense vehicle acceleration along lateral and vertical axes.
Orbiter Rate Gyro Assemblies
Used by flight control system to sense roll, pitch and yaw rates during ascent and entry.
Solid Rocket Booster Rate Gyro Assemblies
Used as feedback to find rate errors from liftoff to SRB separation.
Rotational Hand Controller
Used by flight crew to gimbal engines and OMS/RCS systems.
Translational Hand Controller
Used for manual control of translation along the longitudinal, lateral, and vertical axes to control RCS.
Control Stick Steering Push Button Light Indicators
Indicate control stick mode.
Rudder Pedals
Command orbiter rotation about the yaw axis by positioning the rudder during atmospheric flight.
Speed Brake/Thrust Controller
Used during ascent to vary thrust level of main engines; used during entry to control aerodynamic drag.
Body Flap Switches
Provide manual control for positioning body flap during entry.
RHC/Panel Enable/Inhibit
Provide signals to GPCs, prohibiting execution of related software commands while RHC is active.
Trim Switches
Used to move the aerosurfaces in roll, pitch and yaw.
Aerosurface Servoamplifiers
Receive commands during atmospheric flight, causing aerosurface deflections.
Digital Autopilot
Composed of several software modules that interpret maneuver commands and generate commands for the appropriate effectors.
Rendezvous Thrusting Maneuvers
OMS/RCS thrusting periods can be used to correct or modify the orbit as required.
Component Locations
Black boxes are situated in several locations around the orbiter.
Dedicated Display Systems
Provide the flight crew with data required to fly the vehicle manually or to monitor automatic FCS performance.
Attitude Director Indicator
Provide attitude data, including attitude rates and errors.
Horizontal Situation Indicator
Displays a pictorial view of the vehicle's position.
Alpha Mach Indicator
Display vehicle angle of attack.
Altitude/Vertical Velocity Indicator
Display vertical acceleration, vertical velocity, barometric altitude and radar altitude.
Surface Position Indicator
Displays actual and commanded positions of elevons, body flap, rudder, aileron and speed brake.
Flight Control System Push Button Indicators
Transmit moding requests to digital autopilot.
RCS Command Lights
Indicate RCS jet comands by axis and direction.
G-Meter
Senses linear acceleration along the Z axis of the vehicle.
Head-up Display
Optical miniprocessor that cues the commander during final landing approach.


Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 04/07/2002
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