Abstract
As the human body cannot live and function without the pumping action of the heart, the data processing system (DPS) formed the active heart of the Space Shuttle, for without it the Orbiter simply could not fly. Events such as external tank separation, jet firings, main engine cutoff, communications, and miscellaneous other functions, were so complex and time-critical that only by using computers were they feasible.
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Notes
- 1.
The reason for allocating eight data buses for flight-critical data was a combination of the requirement for fault tolerance and the need to spread the traffic load.
- 2.
Ground support equipment/launch processing sequencer.
- 3.
The state vector is a vectorial representation of the position and velocity of a spacecraft along its orbit. See Chapter 10 for details.
- 4.
Generally speaking, a string comprises a GPC and all the units it directly commands over the flight-critical data buses.
- 5.
Typically, after the first detection of an input error, the transaction was tried again in the next data cycle.
- 6.
A computer that was loaded with the application software of a particular memory configuration was said to be "frozen" or "freeze-dried" if it did not process the software. The procedure was to place a computer in sleep mode after having been frozen, meaning it was in a condition where it drew only the power necessary to maintain the contents of its volatile memory. Flight procedures called for freeze-drying one computer (usually GPC 3) soon after reaching orbit and storing in its memory the re-entry software in order to have an additional source along with the memory units.
- 7.
The reaction control system consisted of a complex arrangement of small jet thrusters located in the forward and aft fuselage sections of the Orbiter, and they were used for small maneuvers and attitude changes. When a given maneuver had to be performed, the fact that more than one jet could be used meant the flight software looked up tables of priority rankings that specified which jet would be used first in order to execute a given maneuver. See Chapter 6 for details of the reaction control system.
- 8.
This key was used for calling both SPEC and DISP pages.
- 9.
This was simply done by pressing the ACK button on the DPS keyboard.
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Sivolella, D. (2014). A brain and mind for the Orbiter: the avionics system. In: To Orbit and Back Again. Springer Praxis Books. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-0983-0_1
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