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Experimental Methods in Materials for Structural Impact Dynamics
Get PDFOver the past two decades significant technological advances have completely changed the way in which experimental testing is conducted in Structural Impact Dynamics applications. Probably the two most significant advances have been the advent of high speed digital video cameras and the use of Digital Image Correlation techniques to measure deformations and strains at high rates. These advances have led to significantly more accurate measurements of material and structural response under high rate loading, which has also led to advances in computational modeling techniques for Impact Dynamics. In this address we will review the past, present and what the future may hold for experimental methods in the field of Structural Impact Dynamics
Computational Non-Destructive Evaluation Improving Ultrasonic Interrogation of Complex Geometry Composite Parts
Get PDFFinite element simulation was employed in modeling the ultrasound (UT) pressure pulse propagation through a coupled liquid-composite medium to reproduce experimental data. From the simulation point of view, the proposed approach is challenging when there is a large simulation domain. For example, it is shown that a sub-micron wavelength of an ultrasonic wave requires a mesh size of several microns and this in turn requires significant computational resources, as well as special care in modeling. Some of the simulation results are presented considering that such modeling should reproduce experimental data for a healthy and faulty composite structure with complex geometry. Many possible experimental setups are simulated to demonstrate the non-destructive testing technique. This setup includes the generation of pressure pulse propagating through the tested composite plate and possible scattering by discontinuities (area of different impedance) that may be present in the panel. This scattered pulse together with the baseline pressure pulse generates a signature on the probe element which can be used to locate the position of defects in the structures
Summary of the NASA Large Constellations Parametric Study
Get PDFIn recent years, several commercial companies have proposed telecommunications constellations consisting of hundreds to thousands of 100-to-300-kg class spacecraft in low Earth orbit (LEO, the region below 2000-km altitude). If deployed, such large constellations (LCs) will dramatically change the landscape of satellite operations in LEO. From the large number of spacecraft and large amount of mass involved, it is clear that the deployment, operations, and frequent de-orbit and replenishment of the proposed LCs could significantly contribute to the existing orbital debris problem. To better understand the nature of the problem, the NASA Orbital Debris Program Office (ODPO) recently completed a parametric study on LCs. The objective was to quantify the potential negative debris-generation effects from LCs to the LEO environment and provide recommendations for mitigation measures. The tool used for the LC study was the ODPOs LEO-to-GEO Environment Debris (LEGEND) numerical simulation model, which has been used for various mitigation and remediation studies in the past. For the LC study, more than 300 scenarios based on different user-specified assumptions and parameters were defined. Selected results from key scenarios are summarized in this paper
Transfer-Function Determination for Infinite-Tube-Probe Pressure Transducers with Application to Turbofan Core/Combuster Noise
Get PDFTurbofan hot-section unsteady pressure measurements are complicated by environmental limitations of current-generation sensors. Accurate direct measurements are normally not possible and engine-external measurement techniques, using sufficiently long sense lines, are utilized instead. Remote measurement comes at a cost, however, as it introduces a magnitude reduction within the line as well as a phase lag relative to the desired engine-internal measurement location. Determination, or validation, of a transfer function relating the engine internal pressure to the observed remote value is necessary. Transfer functions are examined for various configurations of the so-called infinite-tube-probe arrangement in order to optimize measurement performance. The experimental setup uses a normal-incidence tube that ordinarily is utilized for impedance eduction. Here, its downstream end instead is made up of a hard-wall termination instrumented with a flush-mounted microphone and a Kulite pressure transducer as well as a sense line connection. This allows the remote and direct measurements to be related under controlled conditions. Transfer-function measurements are presented and compared to predictions for several parametric variations
Advanced Colloids Experiment (Temperature Controlled) - (ACE-T11)
Get PDFIncrement 59-60 Science Symposium presentation of Advanced Colloids Experiment (ACE-T11, Khusid - NJIT (New Jersey Inst. of Technology)) to RPO (Research Program Office). The purpose of this event is for Principal Investigators to present their science objectives, testing approach, and measurement methods to agency scientists, managers, and other investigators. It is often assumed that time-average weightlessness simulated in a clinostat can reduce the effect of gravity on samples. Why not use it for colloids? Low-gravity parabolic flight tests on a non-buoyancy matched suspension demonstrated that time-average weightlessness in a clinostat does not eliminate gravity effect on patterns in colloids formed by an electric field. The long-term microgravity ISS (International Space Station) experiment provides a unique opportunity to reveal the relationship between external forces on the scale of individual particles and the colloid dynamics on the macroscopic scale
Graphical Primer of NASA Glenn SiC JFET Integrated Circuit (IC) Version 12 Layout
Get PDFThis presentation illustratively communicates integrated circuit (IC) mask design and layout rules for NASA GRC's upcoming prototype fabrication of SiC JFET IC Version 12
Exploring Beyond Earth's Atmosphere with Human-Machine Teams
Get PDFNASA's highly successful Kepler Mission has revolutionized our understanding of the Galaxy. We now know that planets, even Earth-size planets in the habitable zone, are common. With the end of the Kepler Mission we now look to the future with the Transiting Exoplanet Survey Satellite (TESS) which will discover thousands of exoplanets in orbit around the brightest stars in the sky. In a two-year survey, TESS will perform an all-sky search of more than 200,000 stars for temporary drops in brightness caused by planetary transits. With Kepler and TESS, humanity is finally at the verge of studying the masses, sizes, densities, orbits, and atmospheres of a large cohort of small planets, including a sample of rocky worlds in the habitable zones of their host stars which may prove to host life. The massive data sets generated by Kepler and TESS must be meticulously combed for the weakest planetary signals every month. While a daunting and error-prone task for humans, this is an exciting opportunity for the breakthroughs recently seen in machine learning. Specifically, traditional methods for identifying planet transits require extensive data processing pipelines followed by extensive human vetting. This manual process risks loss of information due to the data processing and to inconsistency and biases due to individual human vetters. The latest advancements in machine learning will allow an objective classifier to minimize the losses of information and greatly lessen the burden on the human vetters, in addition to providing assessment of quality and score to each planet candidate, freeing the humans to concentrate on border cases and other more interesting investigations
International Space Station Multilateral Medical Policy Board Transitions in Space Medicine: 25 Years in Photos
No full textThis collection of photographic highlights covers the past 25 years of international collaboration in human space flight. Beginning in 1993, the international community came together to develop the medical systems for an international space station. Initially, this collaboration was bilateral in support of the Shuttle / Mir Space Station (Phase 1). However, the framework that was established to serve as the medical authority structure provided a foundation for the multilateral boards and panel, which were codified in the memoranda of understanding. The Multilateral Medical Policy Board, the Multilateral Space Medicine Board, and the Multilateral Medical Operations Panel were developed in a collegial and mutually beneficial environment by the men and women of the space agencies of Canada, Europe, Japan, Russia, and the United States. This collection of photographs from official and personal collections captures the spirit and collegiality to which we have grown accustomed. They are also presented to commemorate the integrity, professionalism, tenacity, and dedication to human space exploration consistently demonstrated by individuals involved in this amazing effort