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For Release: August 13, 2002

Sally V. Harrington
Media Relations Office

Virtual Propulsion System Meets Real-Time Diagnostic System

NASA researchers recently demonstrated successful real-time fault detection and isolation of a virtual main propulsion system at NASA's Glenn Research Center, Cleveland. The goal of this research was to mature and demonstrate key Integrated Vehicle Health Management (IVHM) technologies--one of several technologies that are involved in NASA's Space Launch Initiative (SLI), an Agencywide effort to significantly increase crew safety while reducing payload launch costs.

Using a detailed simulation of a vehicle propulsion system to produce synthesized sensor readings, the team of researchers demonstrated that advanced diagnostic algorithms, running on actual flight class computers, can, in real time, successfully diagnose the presence and cause of faults.

This demonstration was conducted as part of the NASA Propulsion IVHM Technology Experiment, or PITEX. It was a joint effort including Glenn, Ames Research Center, Moffett Field, Calif. and Kennedy Space Center, Fla. The experiment supports work for the SLI IVHM project contracted to Northrop Grumman of El Segundo, Calif.

Glenn researchers developed a detailed simulation of a main propulsion feed system, which they ran under both nominal and fault conditions in order to generate time histories of propulsion system parameters. Noise was superimposed on the simulation output to provide realistic sensor signals. Typical propulsion system failures such as valves sticking open or closed, regulator problems, and sensor and microswitch failures were injected at various points in a simulated mission.

The simulated data were fed, in real time, to IVHM software running on a computer that is a commercial grade version of actual flight hardware. The computer hardware was designed and assembled by Kennedy Space Center.

"In all cases, the PITEX diagnostic software detected and isolated the injected fault correctly," said Claudia Meyer, research and technology lead at Glenn.

In addition, resource utilization tests were performed to measure the real-time performance of the diagnostic software on the flightlike hardware. Data revealed that resources were largely underutilized, indicating that the diagnostic system could be expanded to cover additional components.

The PITEX diagnostic solution features monitor software, which processes the raw sensor data and an Ames-developed, model-based diagnostic software - Livingstone - that detects and isolates anomalies. Livingstone uses a qualitative model of the system to predict the expected state; system-level reasoning is performed to resolve differences between the observed and expected states.

"These efforts are the culmination of many years of research," said Harry Cikanek, manager of the Space Transportation Project Office at Glenn. "PITEX application of these advances represents an essential step on the path to meet Program goals for safety and cost."

In continuing work, the PITEX diagnostic solution is being migrated to Northrop Grumman's IVHM Virtual Test Bed (IVTB). In the IVTB, a broad range of vehicle subsystem health managers, in addition to propulsion, will be considered, and the benefits of coordinating the subsystem health managers through area and system-level health managers will be demonstrated.

The Space Launch Initiative is NASA's technology research and development program aimed at dramatically increasing safety and reliability and reducing the cost of a 2nd generation reusable launch vehicle. All NASA's field centers and the Air Force Research Laboratory are actively participating in the Space Launch Initiative and are vital to its success. NASA's Marshall Space Flight Center in Huntsville, Ala., leads the Space Launch Initiative for NASA's Office of Aerospace Technology.

Further information on the Space Launch Initiative can be found at the following web sites:

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