Tech Briefs

Wald Sequential Probability Ratio Test for Space Object Conjunction Assessment

The decision procedure is based on targets for false alarm and missed detection rates, along with a prior assessment of the risk of collision, which is independent of the orbit determination. Goddard Space Flight Center, Greenbelt, Maryland When a maneuverable spacecraft confronts a potentially unsafe conjunction with another space object, its operators must decide whether to maneuver to mitigate the risk of a collision. Such decisions may not be straightforward, since the operators must balance their confidence in the predictions that detected the conjunction, the actual likelihood of a collision, any risk inherent in performing the maneuver, interruptions to the mission’s ongoing operations, and long-term consequences such as depletion of consumable propellant. The most common metric for assessing the risk associated with a conjunction is the collision probability.

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Next Generation of 3DGRAPE: Flexible Framework for Hypersonic Navier-Stokes Shuttle Orbiter Meshes

High-fidelity grids were generated rapidly using an assembly line approach with teamwork among NASA centers. Langley Research Center, Hampton, Virginia The class of 3DGRAPE codes is designed to generate volume grids using iterative methods to solve the non-linear, nonhomogeneous, elliptic partial differential heat equation with heat sources. The solution to the heat equation develops three-dimensional discrete points within a domain outside or inside a vehicle where fluid flow is simulated with Computational Fluid Dynamics (CFD). The latest version in this class of software is the 3DGRAPE/AL:V3, version 3 of the Three-Dimensional Grids about Anything by Poisson’s Equation with Upgrades from NASA Ames and Langley computer programs. The previous version, 3DGRAPE/AL:V2 [“Further Improvement in 3DGRAPE,” (LAR-16415-1) NASA Tech Briefs, Vol. 28, No. 9 (September 2004), p. 50], was advanced through the development of a new block-to-block boundary condition that guarantees C-I continuity between adjacent blocks sharing a common block face. Until this condition was developed, matching block faces were only created by projecting a straight line from one cell into each block from the matching face, thereby changing the initial grid that defines a structured multiple block system.

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Delay Tolerant Link State Routing MACHETE Model

NASA’s Jet Propulsion Laboratory, Pasadena, California This software models the Delay Tolerant Link State Routing protocol. It runs inside the QualNet network simulator, and allows injecting of external bundles when running in emulation mode. It leverages QualNet’s library of networking protocols and JPL’s CCSDS models.

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Extendable Uniform Remote Operations Planning Architecture (EUROPA) 2.1

Ames Research Center, Moffett Field, California The EUROPA planning system is a general-purpose, reusable, artificial intelligence software system for automatically generating plans for performing complex activities in parallel, in accordance with constraints on activities and their interactions. One part of the system input is a domain model, which describes the subsystems in question, their possible activities, and the associated constraints. The other part is a plan request, consisting of a set of activities and constraints among them. Given these two inputs, the system will try to find a complete plan that allows all aspects of the plan request to be done, while satisfying the constraints specified in the domain model. This functionality includes the capability of verifying that a plan satisfies all constraints. The system is designed to allow different techniques to be used to complete or verify plans.

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Acoustic Emission Analysis Applet (AEAA) Software

This program has application for any pressure vessel acoustic emission data where advanced analysis is needed. John H. Glenn Research Center, Cleveland, Ohio Vendor software supplied with commercial acoustic emission equipment is incapable of performing the analysis required to characterize damage and make decisions on remaining life for NASA composite overwrapped pressure vessels (COPVs). The Acoustic Emission Analysis Applet (AEAA) software, currently a post-processing capability, will, in the second phase of the program, be modified to work in-situ in order to allow near-real-time decision-making on COPV damage and remaining life. Ultimately, this software will be utilized in-situ in pseudo-real time to monitor COPVs on space vehicles.

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Software-Defined Beacon Receiver Implementation Using Frequency Estimation Algorithms

This algorithm yields a more accurate measurement of frequency and signal power than conventional approaches. John H. Glenn Research Center, Cleveland, Ohio The objective of this work was to develop a robust, cost-effective receiver with maximum dynamic range to track the frequency and power variation of a beacon signal. The result was the development of a frequency estimation algorithm that yields a more accurate measurement of frequency and signal power than conventional approaches like a simple FFT (fast Fourier transform) peak search with bin summing, or a phase locked loop (PLL).

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CT-CURS: Computed Tomography Cylinder Data Unwrapping-Reslicing & Analysis, v2

John H. Glenn Research Center, Cleveland, Ohio The software for NASA’s Northstar Systems computed tomography (CT) and Picometrix Terahertz CT systems do not have the ability to unwrap and reslice cylindrical CT data to allow top-to-bottom, 2D sheet views of the data. Therefore, it is difficult to size flaws laterally (although viewing slices in the slice view plane allows sizing flaws in the depth [exterior-to-interior] direction). The unwrapped and resliced view would greatly facilitate inspection assessments.

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