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At least 253 records · Page 14

All sources NASA NTRS DOE OSTI

NASA NTRSDate not supplied

Analysis of Darkened Fragments Resulting from Laboratory Hypervelocity Experiments

NASA’s Orbital Debris Program Office (ODPO) relies on measurements from optical, radar, and in situ measurements to facilitate the development of data-driven orbital debris environmental engineering models such as the NASA Orbital Debris Engineering Model (ORDEM). For optical measurements, the ODPO relies on ground-based optical telescopes to statistically assess objects in geosynchronous orbit (GEO) and, in the future, low Earth orbit (LEO). The data collected include the detected object’s orbital parameters, time of observation, and optical magnitude. The latter parameter can be converted to a size using NASA’s optical Size Estimation Model (oSEM). It is well known that the observed magnitude of orbital debris can vary based on an object's material constituents, observational geometry, and the effects of space weathering.

Heather Cowardin↗

DOE OSTI2021

Background measurement methods for opacity experiments conducted at the Z facility

Laboratory experiments typically test opacity models by measuring spectrally resolved transmission of a sample using bright backlight radiation. A potential problem is that any unaccounted background signal contaminating the spectrum will artificially reduce the inferred opacity. Methods developed to measure background signals in opacity experiments at the Sandia Z facility are discussed. Preliminary measurements indicate that backgrounds are 9%–11% of the backlight signal at wavelengths less than 10 Å. Background is thus a relatively modest correction for all Z opacity data published to date. Future work will determine how important background is at longer wavelengths.

47 OTHER INSTRUMENTATION↗

NASA NTRS1991

Earth's core-mantle boundary - Results of experiments at high pressures and temperatures

Laboratory experiments document that liquid iron reacts chemically with silicates at high pressures (above 2.4 x 10 to the 10th Pa) and temperatures. In particular, (Mg,Fe)SiO3 perovskite, the most abundant mineral of earth's lower mantle, is expected to react with liquid iron to produce metallic alloys (FeO and FeSi) and nonmetallic silicates (SiO2 stishovite and MgSiO3 perovskite) at the pressures of the core-mantle boundary, 14 x 10 to the 10th Pa. The experimental observations, in conjunction with seismological data, suggest that the lowermost 200 to 300 km of earth's mantle, the D-double-prime layer, may be an extremely heterogeneous region as a result of chemical reactions between the silicate mantle and the liquid iron alloy of earth's core. The combined thermal-chemical-electrical boundary layer resulting from such reactions offers a plausible explanation for the complex behavior of seismic waves near the core-mantle boundary and could influence earth's magnetic field observed at the surface.

Knittle, Elise↗

NASA NTRSDate not supplied

Testing Destruction of Clay Minerals By Silica-Poor Brines in Gale Crater, Mars Using Laboratory and Field Experiments

The Mars Science Laboratory (MSL) Curiosity rover landed in Gale crater to investigate the cause for mineralogical changes seen from orbit, including the clay-sulfate mineral transition observed on its central mound, Aeolis Mons. The lower strata show spectral signatures of clay minerals, hematite, and hydrated Mg sulfates, and the upper strata are dominated by hydrated Mg sulfate signatures. This significant transition has been observed in other locations on Mars, and therefore processes related to the clay mineral-sulfate transition are likely important broadly across Mars. The bulk mineralogy of ~3.7 Ga sedimentary rocks in Gale crater is a product of variations in sediment sources and depositional processes, with overprinting by episodes of early and late diagenetic alteration. Sedimentary analyses of the smectite clay minerals observed in the Glen Torridon (GT) region of Mount Sharp suggest formation in a lacustrine aqueous environment. Examination of the Vera Rubin ridge (VRR) strata indicate that it was formed at the same time as GT and later altered by extensive diagenesis. Recent work suggests that the observed mineral transition from smectites and talc-serpentinites in GT to iron oxides and oxyhydroxides and VRR may have resulted from extensive diagenetic alteration by density driven, silica-poor brines sourced from the overlying sulfur-bearing unit on Mount Sharp. This process of alteration by silica-poor brines is observed in limited locations on Earth. We are therefore working to demonstrate the impacts of silica poor brines on clay mineral alteration in laboratory column and terrestrial analog burial experiments. Column experiments allow the investigation of dissolution and precipitation under conditions that represent a closer analog to natural environments, while burial experiments allow examination of weathering reactions of a known starting material after a specific period of time in a natural field environment. Both methods are valuable for interpreting the water-rock interactions between clay minerals and brines. In preparation for these longer-term column and burial experiments, we are performing preliminary batch dissolution experiments on materials relevant to Glen Torridon: nontronite and serpentinite. We are using magnesium sulfate brine solutions relevant to those proposed on Mars. The results of this study can provide constraints on the characteristics of the diagenetic fluids that formed the altered minerals in Gale crater. They can also provide insights into the role of brine density-driven diagenesis in past aqueous environments on Mars, which have been proposed to be widespread.

J E Valdueza↗

NASA NTRS1994

Assessment of velocity/trajectory measurement technologies during a particle capture event

Since the early 1960s, the means to measure the time of flight (TOF) of dust grain within a mechanical detection array has existed, first in the laboratory and then in space experiments. Laboratory hypervelocity dust particle accelerators have used electrostatic detection of charge on accelerated particles for TOF and particle mass detections. These laboratory studies have led to the development of ultra-thin-film sensors that have been used for TOF measurements in dust particle space experiments. The prototypes for such devices were ultra-thin-film capacitors that were used in the OGO series of satellites. The main goal of the experimental work to be described is the development of the capability to determine the velocity vector or trajectory of a dust grain traversing an integrated dust detection array. The results of these studies have shown that the capability of detecting the charge liberated by hypervelocity dust grains with diameters in the micrometer range can be detected. Based on these results, detection systems have been designed to provide a precise analysis of the physical and dynamic properties of micrometer and submicrometer dust grains, namely the design verification unit (DVU). Through unique combinations of in situ detection systems, direct measurements of particle surface charge, velocity, momentum, kinetic energy, and trajectory have been achieved. From these measurements, the remaining physical parameters of mass, size, and density can be determined.

Tanner, William G.↗

NASA NTRS2004

Chondrule Crystallization Experiments

Given the great diversity of chondrules, laboratory experiments are invaluable in yielding information on chondrule formation process(es) and for deciphering their initial conditions of formation together with their thermal history. In addition, they provide some critical parameters for astrophysical models of the solar system and of nebular disk evolution in particular (partial pressures, temperature, time, opacity, etc). Most of the experiments simulating chondrules have assumed formation from an aggregate of solid grains, with total pressure of no importance and with virtually no gain or loss of elements from or to the ambient environment. They used pressed pellets attached to wires and suffered from some losses of alkalis and Fe.

Hweins, R. H.↗

NASA NTRS1981

Analytical and experimental investigation of liquid double drop dynamics: Preliminary design for space shuttle experiments

The preliminary grant assessed the use of laboratory experiments for simulating low g liquid drop experiments in the space shuttle environment. Investigations were begun of appropriate immiscible liquid systems, design of experimental apparatus and analyses. The current grant continued these topics, completed construction and preliminary testing of the experimental apparatus, and performed experiments on single and compound liquid drops. A continuing assessment of laboratory capabilities, and the interests of project personnel and available collaborators, led to, after consultations with NASA personnel, a research emphasis specializing on compound drops consisting of hollow plastic or elastic spheroids filled with liquids.

Source record↗

NASA NTRS2001

Ground Based Experiments in Support of Microgravity Research Results-Vapor Growth of Organic Nonlinear Optical Thin Film

This work is specifically focused on explaining previous results obtained for the crystal growth of an organic material in a reduced gravity environment. On STS-59, in April 1994, two experiments were conducted with N,N-dimethyl-p-(2,2-dicyanovinyl) aniline (DCVA), a promising nonlinear optical (NLO) material. The space experiments were set to reproduce laboratory experiments that yielded small, bulk crystals of DCVA. The results of the flight experiment, however, were surprising. Rather than producing a bulk single crystal, the result was the production of two high quality, single crystalline thin films. This result was even more intriguing when it is considered that thin films are more desirable for NLO applications than are bulk single crystals. Repeated attempts on the ground to reproduce these results were fruitless. A second set of flight experiments was conducted on STS-69 in September 1995. This time eight DCVA experiments were flown, with each of seven experiments containing a slight change from the first reference experiment. The reference experiment was programmed with growth conditions identical to those of the STS-59 mission. The slight variations in each of the other seven were an attempt to understand what particular parameter was responsible for the preference of thin film growth over bulk crystal growth in microgravity. Once again the results were surprising. In all eight cases thin films were grown again, albeit with varying quality. So now we were faced with a phenomenon that not only takes place in microgravity, but also is very robust, resisting all attempts to force the growth of bulk single crystals.

Zugrav, M. Ittu↗

DOE OSTI2022

Experimental results of conductive inserts to reduce nuclear fuel temperature during nuclear volumetric heating

Advanced fuel designs that incorporate thinner fuel UO2 pellets interspaced by high thermal conductivity inserts have been proposed, with the primary goals of reducing peak centerline temperatures and temperature gradients across fuel pellets and enhancing heat transfer from the fuel to the coolant. An initial series of experiments has been performed on this design, including laboratory experiments and a series of experiments using the Idaho National Laboratory (INL) Transient Reactor Test (TREAT) Facility, the latter of which compared thermal gradient driven fracture of standard pellet designs with that in the proposed advanced fuel design. Although reducing fracture is not the primary objective of the new fuel design, the lower thermal gradients are expected to reduce fracture, so it can serve as an indicator of the thermal behavior of this fuel in the reactor. The in-reactor tests were conducted at multiple linear heat generation rates and confirm the expected result that fracture in both the standard and advanced fuel pellets occurs during the first ramp to power in standard light-water reactor conditions. Post-irradiation examination of the experiment material was performed and included quantification of the extent of fracture in the fuel pellets. It was found that the advanced-design pellets reduce the extent of fracture in a statistically significant way. This confirms the expected behavior predicted by two-dimensional axisymmetric models of this experiment. Here in this study is an important first experimental confirmation of the efficacy of the proposed inserts for achieving their desired effect on the thermal behavior of the fuel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2022

Cracking in first ramp to power of standard versus high thermal conductivity UO2 pellets via internal nuclear heating

Advanced fuel designs that incorporate thinner fuel UO2 pellets interspaced by high thermal conductivity inserts have been proposed, with the primary goals of reducing peak centerline temperatures and temperature gradients across fuel pellets and enhancing heat transfer from the fuel to the coolant. An initial series of experiments has been performed on this design, including laboratory experiments and a series of experiments using the Idaho National Laboratory (INL) Transient Reactor Test (TREAT) Facility, the latter of which compared thermal gradient driven fracture of standard pellet designs with that in the proposed advanced fuel design. Although reducing fracture is not the primary objective of the new fuel design, the lower thermal gradients are expected to reduce fracture, so it can serve as an indicator of the thermal behavior of this fuel in the reactor. The in-reactor tests were conducted at multiple linear heat generation rates and confirm the expected result that fracture in both the standard and advanced fuel pellets occurs during the first ramp to power in standard light-water reactor conditions. Post-irradiation examination of the experiment material was performed and included quantification of the extent of fracture in the fuel pellets. It was found that the advanced-design pellets reduce the extent of fracture in a statistically significant way. This confirms the expected behavior predicted by two-dimensional axisymmetric models of this experiment. This study is an important first experimental confirmation of the efficacy of the proposed inserts for achieving their desired effect on the thermal behavior of the fuel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

NASA NTRS2020

A New Method to Correct the Electrochemical Concentration Cell (ECC) Ozonesonde Time Response and its Implications for "Background Current" and Pump Efficiency

The electrochemical concentration cell (ECC) ozonesonde has been the main instrument for in situ profiling of ozone worldwide; yet, some details of its operation, which contribute to the ozone uncertainty budget, are not well understood. Here, we investigate the time response of the chemical reactions inside the ECC and how corrections can be used to remove some systematic biases. The analysis is based on the understanding that two reaction pathways involving ozone occur inside the ECC that generate electrical currents on two very different timescales. The main fast-reaction pathway with a time constant of about 20 s is due the conversion of iodide to molecular iodine and the generation of two free electrons per ozone molecule. A secondary slow-reaction pathway involving the buffer generates an excess current of about 2 %–10 % with a time constant of about 25 min. This excess current can be interpreted as what has conventionally been considered the “background current”. This contribution can be calculated and removed from the measured current instead of the background current. Here we provide an algorithm to calculate and remove the contribution of the slow-reaction pathway and to correct for the time lag of the fast-reaction pathway. This processing algorithm has been applied to ozonesonde profiles at Costa Rica and during the Central Equatorial Pacific Experiment (CEPEX) as well as to laboratory experiments evaluating the performance of ECC ozonesondes. At Costa Rica, where a 1 % KI, 1/10th buffer solution is used, there is no change in the derived total ozone column; however, in the upper troposphere and lower stratosphere, average reported ozone concentrations increase by up to 7 % and above 30 km decrease by up to 7 %. During CEPEX, where a 1 % KI, full-buffer solution was used, ozone concentrations are increased mostly in the upper troposphere, with no change near the top of the profile. In the laboratory measurements, the processing algorithms have been applied to measurements using the majority of current sensing solutions and using only the stronger pump efficiency correction reported by Johnson et al. (2002). This improves the accuracy of the ECC sonde ozone profiles, especially for low ozone concentrations or large ozone gradients and removes systematic biases relative to the reference instruments. In the surface layer, operational procedures prior to launch, in particular the use of filters, influence how typical gradients above the surface are detected. The correction algorithm may report gradients that are steeper than originally reported, but their uncertainty is strongly influenced by the prelaunch procedures.

electrochemical concentration cell (ECC) ozonesond↗

DOE OSTI2024

Effects of salinity and nutrients on metabolism and growth of Ulva lactuca: implications for bioremediation in San Diego Bay and Coastal Watershed

Our project sought to explore the ability of seaweed (Ulva lactuca) farms to clean polluted waterways of excess nitrogen and phosphorus through bioremediation. We addressed this goal in three primary ways. First, we worked with an undergraduate student from the Environmental Sciences Department at SDSU (Emily Bews) to examine how Ulva would perform under elevated nutrients and decreased salinity conditions, such as would be expected on the seaweed farms during periods of high rainwater runoff. This would show whether Ulva could indeed be grown on farms during these periods. We conducted laboratory experiments at SDSU’s CMIL (marine laboratory) using orthogonal combinations of two salinities and three nutrient loadings, and measured several aspects of Ulva physiology, namely growth, photosynthetic rates, chlorophyll fluorescence, and stable isotope analyses of Ulva’s tissues, and tissue uptake of phosphorus and nitrogen. Our results clearly show Ulva is an ideal candidate for using on farms during periods of heavy rains and takes up excess nutrients. The results of this were published in Marine Pollution Bulletin, with undergraduate Bews as lead author (Bews, E., L. Booher, T. Polizzi, C. Long, J-H Kim, MS Edwards. 2021. Effects of salinity and nutrients on metabolism and growth of Ulva lactuca: implications for bioremediation of coastal watersheds. Marine Pollution Bulletin 166: 121299.).

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1987

Chemistry Research

Philip Morris research center scientists use a computer program called CECTRP, for Chemical Equilibrium Composition and Transport Properties, to gain insight into the behavior of atoms as they progress along the reaction pathway. Use of the program lets the scientist accurately predict the behavior of a given molecule or group of molecules. Computer generated data must be checked by laboratory experiment, but the use of CECTRP saves the researchers hundreds of hours of laboratory time since experiments must run only to validate the computer's prediction. Philip Morris estimates that had CECTRP not been available, at least two man years would have been required to develop a program to perform similar free energy calculations.

Source record↗

NASA NTRS1993

Multiorder etalon sounder (MOES) development and test for balloon experiment

The Fabry-Perot interferometer (FPI), with its high throughput and high spectral resolution has been used in the remote-sensing measurements of the earth's atmospheric composition, winds, and temperatures. The most recent satellite instruments include the Fabry-Perot interferometer flown on the Dynamics Explorer-2 (DE-2), the High Resolution Doppler Imager (HRDI), and the Cryogenic Limb Array Etalon Spectrometer (CLAES) flown on the Upper Atmosphere Research Satellite (UARS). These instruments measure the Doppler line profiles of the emission and absorption of certain atmospheric species (such as atomic oxygen) in the visible and infrared spectral region. The successful space flight of DE-FPI, HRDI, and CLAES on UARS demonstrated the extremely high spectral resolution and ruggedness of the etalon system for the remote sensing of earth and planetary atmospheres. Recently, an innovative FPI focal plane detection technique called the Circle-to-Line Interferometer Optical (CLIO) system was invented at the Space Physics Research Laboratory. The CLIO simplifies the FPI focal plane detection process by converting the circular rings or fringes into a linear pattern similar to that produced by a conventional spectrometer, while retaining the throughput advantage of the etalon interferometer. The combination of FPI and CLIO allows the development of more sensitive Fabry-Perot interferometers in the infrared for the remote sensing of the lower atmospheres of Earth and possibly other planets. The Multiorder Etalon Sounder (MOES), a combination of the rugged etalon and the CLIO, compares very favorably to other space-borne optical instruments in terms of performance versus complexity. The new instrument is expected to be rugged, compact, and very suitable for an operational temperature and moisture sounder. With this technique, the contamination of radiance measurements by emissions of other gases is also minimized. At the Space Physics Research Laboratory (SPRL), the MOES concept and laboratory experiments were worked on for the past several years. Both theoretical studies and laboratory prototype experiments showed that MOES is very competitive compared with other high resolution sounders in terms of complexity and performance and has great potential as a compact and rugged high resolution atmospheric temperature and trace species sounder from the polar platform or the geostationary platform. The logical next step is to convert our laboratory prototype to a balloon instrument, so that field test of MOES can be carried out to prove the feasibility and capability of this new technology. Some of the activities related to the development of MOES for a possible balloon flight demonstration are described. Those research activities include the imaging quality study on the CLIO, the design and construction of a MOES laboratory prototype, the test and calibration of the MOES prototype, and the design of the balloon flight gondola.

Hays, Paul B.↗

NASA NTRS1984

Space Environment Effects on Spacecraft Materials (M0003)

The immediate objectives of this experiment are to understand changes in the properties and structure of materials after exposure to the space environment and to compare these changes with predictions based on laboratory experiments. The experiment consists of 19 subexperiments involving a number of DOD laboratories and contractor organizations. In general, the experimental approach with each of the subexperiments will involve comparison of preflight and postflight analyses. Typical analyses will include the measurement of optical properties (reflectance, transmittance, and refractive index), and macrophysical properties. In addition to measuring changes in the macroscopic properties of the returned specimens, microstructural properties will also be examined. Thus, it may be possible to increase our understanding of the changes induced by the environment. This increased understanding can then be used to predict the performance of materials based on knowledge of the space environment and the results of laboratory tests. This experiment will be a coopperative effort and will provide an opportunity for DOD space programs and laboratories to evaluate materials and components after long exposures to the space environment.

Paul Schall↗

NASA NTRS1962

Aerodynamic Evidence Pertaining to the Entry of Tektites into the Earth's Atmosphere

Evidence is presented which shows that the Australian and Java tektites entered the earth's atmosphere and experienced ablation by severe aerodynamic heating in hypervelocity flight. The laboratory experiments on hypervelocity ablation have reproduced ring-wave flow ridges and coiled circumferential flanges like those found on certain of these tektites. Systematic striae distortions exhibited in a thin layer beneath the front surface of australites also are reproduced in the laboratory ablation experiments, and are shown to correspond to the calculated distortions for aerodynamic ablation of a glass. About 98 percent of Australian tektites represent aerodynamically stable configurations during the ablative portion of an entry trajectory. Certain meteorites exhibit surface features similar to those on tektites.

AERODYNAMIC HEATING↗

DOE OSTI2022

Hybrid particle-in-cell simulations of electromagnetic coupling and waves from streaming burst debris

Various systems can be modeled as a point-like explosion of ionized debris into a magnetized, collisionless background plasma-including astrophysical examples, active experiments in space, and laser-driven laboratory experiments. Debris streaming from the explosion parallel to the magnetic field may drive multiple resonant and non-resonant ion-ion beam instabilities, some of which can efficiently couple the debris energy to the background and may even support the formation of shocks. We present a large-scale hybrid (kinetic ions + fluid electrons) particle-in-cell simulation, extending hundreds of ion inertial lengths from a 3D explosion, that resolves these instabilities. We show that the character of these instabilities differs notably from the 1D equivalent by the presence of unique transverse structure. Additional 2D simulations explore how the debris beam length, width, density, and speed affect debris-background coupling, with implications for the generation of quasi-parallel shocks.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1991

Acquisition and production of skilled behavior in dynamic decision-making tasks: Modeling strategic behavior in human-automation interaction: Why and aid can (and should) go unused

Advances in computer and control technology offer the opportunity for task-offload aiding in human-machine systems. A task-offload aid (e.g., an autopilot, an intelligent assistant) can be selectively engaged by the human operator to dynamically delegate tasks to an automated system. Successful design and performance prediction in such systems requires knowledge of the factors influencing the strategy the operator develops and uses for managing interaction with the task-offload aid. A model is presented that shows how such strategies can be predicted as a function of three task context properties (frequency and duration of secondary tasks and costs of delaying secondary tasks) and three aid design properties (aid engagement and disengagement times, aid performance relative to human performance). Sensitivity analysis indicates how each of these contextual and design factors affect the optimal aid aid usage strategy and attainable system performance. The model is applied to understanding human-automation interaction in laboratory experiments on human supervisory control behavior. The laboratory task allowed subjects freedom to determine strategies for using an autopilot in a dynamic, multi-task environment. Modeling results suggested that many subjects may indeed have been acting appropriately by not using the autopilot in the way its designers intended. Although autopilot function was technically sound, this aid was not designed with due regard to the overall task context in which it was placed. These results demonstrate the need for additional research on how people may strategically manage their own resources, as well as those provided by automation, in an effort to keep workload and performance at acceptable levels.

Kirlik, Alex↗