Jose Perotti

Functional Fault Modeling Conventions and Practices for Real-Time Fault Isolation

The purpose of this paper is to present the conventions, best practices, and processes that were established based on the prototype development of a Functional Fault Model (FFM) for a Cryogenic System that would be used for real-time Fault Isolation in a Fault Detection, Isolation, and Recovery (FDIR) system. The FDIR system is envisioned to perform health management functions for both a launch vehicle and the ground systems that support the vehicle during checkout and launch countdown by using a suite of complimentary software tools that alert operators to anomalies and failures in real -time. The FFMs were created offline but would eventually be used by a real -time reasoner to isolate faults in a Cryogenic System. Through their development and review, a set of modeling conventions and best practices were established. The prototype FFM development also provided a pathfinder for future FFM development processes. This paper documents the rationale and considerations for robust FFMs that can easily be transitioned to a real -time operating environment.

Latest development in advanced sensors at Kennedy Space Center (KSC)

An inexpensive space transportation system must be developed in order to make spaceflight more affordable. To achieve this goal, there is a need to develop inexpensive smart sensors to allow autonomous checking of the health of the vehicle and associated ground support equipment, warn technicians or operators of an impending problem and facilitate rapid vehicle pre-launch operations. The Transducers and Data Acquisition group at Kennedy Space Center has initiated an effort to study, research, develop and prototype inexpensive smart sensors to accomplish these goals. Several technological challenges are being investigated and integrated in this project multi-discipline sensors; self-calibration, health self-diagnosis capabilities embedded in sensors; advanced data acquisition systems with failure prediction algorithms and failure correction (self-healing) capabilities.

Lessons learned on implementing Fault Detection, Isolation, and Recovery (FDIR) in a Ground Launch Environment

This paper’s main purpose is to detail issues and lessons learned regarding designing, integrating, and implementing Fault Detection Isolation and Recovery (FDIR) for Constellation Exploration Program (CxP) Ground Operations at Kennedy Space Center (KSC). I. Introduction art of the overall implementation of National Aeronautics and Space Administration’s (NASA’s) Constellation Exploration Program (CxP), Fault Detection Isolation and Recovery (FDIR) is being implemented in three main components of the program (Ares, Orion, and Ground Operations/Processing). While not initially part of the design baseline for the CxP Ground Operations, NASA felt that FDIR is important enough to develop, that NASA’s Exploration Systems Mission Directorate’s (ESMD’s) Exploration Technology Development Program (ETDP) initiated a task for it under their Integrated System Health Management (ISHM) research area. This task, referred to as the FDIR project, is a multi-year multi-center effort. The primary purpose of the FDIR project is to develop a prototype and pathway upon which Fault Detection and Isolation (FDI) may be transitioned into the Ground Operations baseline. While not discussed in this paper, additional details of how this FDIR project fits into the overall NASA structure is available in Ref. 1.

Hierarchy of two-phase flow models for autonomous control of cryogenic loading operation

We report on the development of a hierarchy of models of cryogenic two-phase flow motivated by NASA plans to develop and maturate technology of cryogenic propellant loading on the ground and in space. The solution of this problem requires models that are fast and accurate enough to identify flow conditions, detect faults, and to propose optimal recovery strategy. The hierarchy of models described in this presentation is ranging from homogeneous moving- front approximation to separated non-equilibrium two-phase cryogenic flow. We compare model predictions with experimental data and discuss possible application of these models to on-line integrated health management and control of cryogenic loading operation.

Optimization of cryogenic chilldown and loading operation using SINDA/FLUINT

A cryogenic advanced propellant loading system is currently being developed at NASA. A wide range of applications and variety of loading regimes call for the development of computer assisted design and optimization methods that will reduce time and cost and improve the reliability of the APL performance. A key aspect of development of such methods is modeling and optimization of non-equilibrium two-phase cryogenic flow in the transfer line. Here we report on the development of such optimization methods using commercial SINDA/FLUINT software. The model is based on the solution of two-phase flow conservation equations in one dimension and a full set of correlations for flow patterns, losses, and heat transfer in the pipes, valves, and other system components. We validate this model using experimental data obtained from chilldown and loading of a cryogenic testbed at NASA Kennedy Space Center. We analyze sensitivity of this model with respect to the variation of the key control parameters including pressure in the tanks, openings of the control and dump valves, and insulation. We discuss the formulation of multi-objective optimization problem and provide an example of the solution of such problem.

Functional Fault Modeling of a Cryogenic System for Real- Time Fault Detection and Isolation

The purpose of this paper is to present the model development process used to create a Functional Fault Model (FFM) of a liquid hydrogen (LH2) system that will be used for realtime fault isolation in a Fault Detection, Isolation and Recover (FDIR) system. The paper explains the steps in the model development process and the data products required at each step, including examples of how the steps were performed for the LH2 system. It also shows the relationship between the FDIR requirements and steps in the model development process. The paper concludes with a description of a demonstration of the LH2 model developed using the process and future steps for integrating the model in a live operational environment.

Towards physics based autonomous control of the cryogenic propellant loading system

We report on progress in development of model-based optimization methods for the autonomous control of the propellant loading system. We briefly discuss properties of the models and demonstrate examples of their validation using the experimental data obtained at NIST and at Kennedy Space Center. We consider application of the modelbased optimization methods to the analysis of chilldown and identification and evaluation of the faults in the cryogenic transfer line. It is shown that model-based optimization provides an efficient tool for the development of autonomous control of cryogenic loading operations.

Two-phase flow modelling of the cryogenic propellant loading system

We report on a progress in development of a hierarchy of two-phase flow models that can accurately predict cryogenic fluid dynamics in real time. We provide details of the separated two-phase cryogenic flow model, which is one of the key components of the hierarchy. We discuss the stability and speed of the algorithm and demonstrate a good agreement of the model predictions with experimental data. We discuss progress in developing of a set of tools for parametric studies and optimization of the two-phase flow in cryogenic transfer lines. We provide examples of the sensitivity study and optimization of parameters for the model of a chilldown experiment.

Sensor applications at Kennedy Space Center (KSC)

Transducers used at KSC, in support of processing and launch of flight vehicles and payloads, are designed and tested to meet specific program requirements. Any equipment, transducer or support instrumentation in direct contact or in support to flight vehicle operations is considered ground support equipment (GSE) and required to meet strict program requirements (i.e. Space Shuttle Program, Space Station Program, Evolved Expendable Launch Vehicles, etc.) Transducers used in KSC applications are based on commercial-off-the-shelf transducers and sensor. In order to fully meet KSC requirements, these transducers evolve from standard COTS to modified COTS. The Transducer and Data Acquisition Group of the Instrumentation Branch at Kennedy Space Center is responsible for providing the technical expertise as well as qualification-testing capability to transform these COTS transducers in modified COTS suitable for use around flight hardware.

Ethernet-based smart networked elements (sensors and actuators)

This paper outlines the present design approach for the Ethernet-Based Smart Networked Elements (SNE) being developed by NASAs Instrumentation Branch and the Advanced Electronics and Technology Development Laboratory of ASRC Aerospace Corporation at Kennedy Space Center (KSC). The SNEs are being developed as part of the Integrated Intelligent Health Management System (IIHMS), jointly developed by Stennis Space Center (SSC), KSC, and Marshall Space Flight Center (MSFC). SNEs are sensors/actuators with embedded intelligence, capable of networking among themselves and with higher-level systems (external processors and controllers) to provide not only instrumentation data but also associated data validity qualifiers. NASA KSC has successfully developed and preliminarily demonstrated this new generation of SNEs. SNEs that collect pressure, strain, and temperature measurements (including cryogenic temperature ranges) have been developed and tested in the laboratory and are ready for demonstration in the field.