A high-speed observer (HSO) system comprising a high-frame-rate digital video camera and a high-speed computer that processes the camera output has been developed for use in monitoring the exhaust plume of the space shuttle main engine (SSME) during tests. The HSO system is designed to analyze the digital video data to detect transient streaks and other anomalies in the appearance of the plume that are indicative of engine malfunctions. The basic HSO concept is also applicable to monitoring of transient phenomena in other settings.
In the original SSME application, combustion of hydrogen and oxygen yields nearly transparent plumes when the engine is functioning as intended. Bright streaks in the plumes, typically generated during combustion of contaminants in the hydrogen and/or oxygen, are potential indicators of abnormal events. Streaks can also be caused by combustion of debris generated by erosion of engine parts.
During an engine test, the computer in the HSO system processes the image data in real time to detect and differentiate anomalous plume events that occur during time intervals of the order of 5 ms. Such processing speed makes information on the state of the engine available nearly instantaneously; this information can be monitored by the test conductor and/or by a computer to determine whether the test should be terminated to prevent a catastrophic failure.
More specifically, image data are acquired, validated, saved, and analyzed to detect streaks, and the detected streaks are counted. The processed streak data are examined by expert-system software to determine whether the streaks violate criteria for acceptable engine operation during a sufficiently long time interval that they should be considered indicative of actual or potential trouble.
The hardware and software subsystems of the HSO system are easily reconfigurable, and off-the-shelf hardware and software can be used. The HSO system can be used for posttest analysis of all plume events as well as for monitoring during tests. Small, short-duration streaks can be evaluated against hardware inspection results and streaks correlated with hardware failures.
The HSO system can also be used to detect and analyze transient events (other than changes in image intensity) in settings other than testing of the SSME. Any event that can be recorded by an imaging device and recognized by software can be monitored. Examples include motions of objects, fluid leaks with visible manifestations, and fires.
This work was done by Tom Rieckhoff of Marshall Space Flight Center and Michael O’Farrell and Mark Covan of United Space Alliance. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Electronic Components & Systems category.