Sequencing
A number of non-GNC functions included in the redundant-set software perform critical sequencing and other services for nonavionics subsystems. These functions, conducted using either the master events controller or the flight-critical MDM's as the command transmission media, use the system components shown in figure 4-31. The sequencing functions can be classified as (1) mission events that are nonrepeating but predictable and that require software to initiate and/or to control hardware functions or (2) special computations made to reduce crew workload. Examples of the current set of such functions include
- Redundant-set launch sequence which controls the final count and lift-off operations
- Main propulsion system data and display sequence
- SRB MDM data acquisition
- Main engine operations sequence
- SRB separation sequence
- Main propulsion system propellant-dump sequence
- Abort control sequence
- Abort OMS/RCS interconnect
- Orbiter vent door control
- Landing gear isolation valve control
- RCS/RCS crossfeed and reconfiguration
- RCS quantity monitor
- Orbit OMS/RCS interconnect
- OMS firing sequence
- OMS to RCS propellant gauging
- Master events controller subsystem operating program
- Main engine subsystem operating program
Figure 4-31. - Sequencing configuration.
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