Shuttle
Reference Manual
Space Shuttle
Orbiter Systems
Main Propulsion System
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Overview
The main propulsion system includes three
main engines, controllers and supporting equipment.
Orbiter
Main Propulsion System Helium Subsystem
Helium is used to purge tanks and actuate
valves.
Main
Propulsion System Propellant Management Subsystem
Liquid hydrogen and liquid oxygen are
fuels used by the system.
External
Tank
The external tank feeds fuel to the main propulsion
system.
Space
Shuttle Main Engines
The main engines are reusable, high-performance,
liquid-propellant rocket engines with variable thrust.
Pogo
Suppression System
A pogo suppression system prevents engine
thrust oscillation.
Space
Shuttle Main Engine Controllers
Each controller operates in conjunction with
other components to provide a self-contained system for engine control,
checkout and monitoring.
Malfunction
Detection
There are three separate means of detecting
malfunctions within the main propulsion system.
Orbiter
Hydraulic Systems
Three hydraulic systems supply pressure to
the main propulsion system, providing thrust vector control and
actuating engine valves on each SSME.
Thrust
Vector Control
Ascent thrust vector control directs thrust
of the main engines and SRBs to control attitude and trajectory
from liftoff through second-stage ascent.
Helium,
Oxidizer and Fuel Flow Sequence
The complete sequence begins several hours
before launch and ends after main engine cutoff.
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