The Propulsion Integrated Vehicle Health Management (IVHM) Technology Experiment (PITEX) is a continuing NASA effort being conducted cooperativelyby the NASA Glenn Research Center, the NASA Ames Research Center, and the NASA Kennedy Space Center. It was a key element of a Space Launch Initiative risk-reduction task performed by the Northrop Grumman Corporation in El Segundo, California. PITEX's main objectives are the continued maturation of diagnostic technologies that are relevant to second-generation reusable launch vehicle (RLV) subsystems and the assessment of the real-time performance of the PITEX diagnostic solution.
The PITEX effort has considerable legacy in the NASA IVHM Technology Experiment for X-vehicles (NITEX) that was selected to fly on the X-34 subscale RLV that was being developed by Orbital Sciences Cor-poration. NITEX, funded through the Future-X Program Office, was to advance the technology-readiness level of selected IVHM technologies within a flight environment and to begin the transition of these technologies from experimental status into RLV baseline designs. The experiment was to perform real-time fault detection and isolation and suggest potential recovery actions for the X-34 main propulsion system (MPS) during all mission phases by using a combination of system-level analysis and detailed diagnostic algorithms.
PITEX demonstration architecture.
Long description.
The overall PITEX demonstration system architecture is shown in the top figure. The demonstration system was designed to test a subset of software components from the NITEX flight experiment architecture. The software package consists of the telemetry input system, the monitors, the real-time interface, Livingstone and the results output system (which are all contained on a real-time flightlike box called the RxU), and the ground processing unit. The virtual propulsion system simulated the sensor data associated with a particular mission phase and nominal or failure scenario. These data would be input to the monitors, where pertinent features of the propulsion system would be extracted and the quantitative information of the system transformed into qualitative information. This information would then be passed through the real-time interface to Livingstone, where the system-level diagnostics would be performed using a high-level qualitative model of the system. From there, the output would be collected by the results output system and displayed on the ground processing unit.
The selected design reference mission for the X-34 MPS was the captive carry mission phase. This phase was selected because of crew safety considerations of the piloted L-1011. During this phase of operation, the X-34 would be carried to the required launch altitude of 38,000 ft while it was attached to the underside of an L-1011 aircraft. The engine would not be running, and most of the other subsystems of the MPS would be in a quasi-static state, except for the liquid oxidizer (liquid oxygen) and RP-1 (jet fuel) subsystems. The bottom figure on the preceding page captures both the scope of the X-34 mission and the components in the MPS that were used in demonstrations of PITEX.
Design reference mission and MPS schematic tested by PITEX. RP-1, jet fuel;
LO2, liquid oxygen.
Long description.
As part of the second-generation RLV risk-reduction effort, PITEX successfully demonstrated real-time model-based fault detection of a virtual MPS. Realistic propulsion system failures involving valves, regulators, and sensors were simulated and correctly diagnosed by PITEX. Simulated scenarios focused on providing the diagnostic system with realistic data signals, which included random sensor noise, resolution and bias, and build-to-build data variations. During testing of the software on flightlike hardware, system resources--CPU and memory--were found to be largely underutilized. This indicated that more complex applications could be handled by the PITEX diagnostic solution. The current results are summarized in reference 1. The PITEX project continues to address challenges aimed at improving the speed, efficiency, and timeliness of the diagnoses and is exploring other potential applications.
Find out more about this research: http://www.grc.nasa.gov/WWW/cdtb/
Analex Corporation contacts: William A. Maul, 216-977-7496,
William.A.Maul@grc.nasa.gov; and
Amy K. Chicatelli, 216-433-3613, Amy.K.Chicatelli@grc.nasa.gov
Authors: William A. Maul, Amy K. Chicatelli, and Christopher E. Fulton
Headquarters program office: OAT
Programs/Projects: NGLT, OSP, SLEP, SLI
Last updated: January 20, 2005
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