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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

The Pore Formation and Mobility Investigation: A Case Study for Conducting Research on the International Space Station in Support of Exploration

The Pore Formation and Mobility Investigation (PFMI) is being conducted in the Microgravity Science Glovebox (MSG) aboard the International Space Station (ISS) with the goal of understanding bubble generation and interactions during controlled directional solidification processing. Through the course of the experiments, beginning in September 2002, a number of key factors pertinent to solidification processing of materials in a microgravity environment have been directly observed, measured, and modeled. Though most experiments ran uninterrupted, on four separate occasions malfunctions to the PFMI hardware and software were experienced that required crew intervention, including in-space repair. Fortunately, each repair attempt was successful and restored the PFMI apparatus to a fully functional condition. Based on PFMI results and lessons learned, the intent of this presentation is to draw attention to the role ISS experiments/hardware can play in providing insight to potential fabrication processing techniques and repair scenarios that might arise during long duration space transport and/or on the lunar/Mars surface.

Grugel, R. N.↗
NASA NTRS2002

Pore Formation and Mobility (PFMI): An International Space Station Glovebox Investigation

Porosity in the form of "bubbles and pipes" can occur during controlled directional solidification processing of metal alloys. It is detrimental to material properties and precludes obtaining meaningful scientific results. On Earth, density differences allow an initiated bubble can rise through the liquid and "pop" at the surface resulting in a sound casting. This is not likely to occur in a microgravity environment and, unfortunately, a number of experiments conducted in microgravity have suffered from porosity effects. The current investigation is a systematic effort towards understanding porosity formation and mobility during controlled directional solidification in a microgravity environment. This will be investigated by utilizing a transparent material, succinonitrile (SCN), in conjunction with a translating temperature gradient stage so that direct observation and recording of pore generation and mobility can be made. The talk will cover the porosity problem, the details of the proposed experiments and the experimental hardware, and the expectations from the microgravity experiments.

Grugel, R. N.↗
NASA NTRS1987

Mechanical properties of high gradient and hot isostatically pressed PWA 1480

This program has been designed to evaluate the potential benefits to alloy 1480 material properties due to high thermal gradient casting, hot isostatic pressing, and alternative heat treatment. Alloy 1480 castings have been obtained from vendors representing the extremes of commercial casting thermal gradients. Quantitative characterization of the dendrite arm spacing (DAS) and pore distributions has been conducted. A hot isostatic pressing (HIP) schedule, which avoids the many pitfalls of single crystal HIP has been devised for alloy 1480. In addition, an alternate heat treatment for alloy 1480 has been devised which provides benefits in mechanical properties. The standard gradient cast test material is being evaluated in the standard heat treat condition as a baseline and in the HIP plus alternate heat treated condition. The fhigh gradient cast material is being evaluated in alternate heat treat and HIP plus alternate heat treated conditions. Evaluations focus on demonstration of the benefits due to the applied processes, especially in the area of cyclic life.

Fritzemeier, L. G.↗
NASA NTRS2005

Discontinuous pore fluid distribution under microgravity--KC-135 flight investigations

Designing a reliable plant growth system for crop production in space requires the understanding of pore fluid distribution in porous media under microgravity. The objective of this experimental investigation, which was conducted aboard NASA KC-135 reduced gravity flight, is to study possible particle separation and the distribution of discontinuous wetting fluid in porous media under microgravity. KC-135 aircraft provided gravity conditions of 1, 1.8, and 10(-2) g. Glass beads of a known size distribution were used as porous media; and Hexadecane, a petroleum compound immiscible with and lighter than water, was used as wetting fluid at residual saturation. Nitrogen freezer was used to solidify the discontinuous Hexadecane ganglia in glass beads to preserve the ganglia size changes during different gravity conditions, so that the blob-size distributions (BSDs) could be measured after flight. It was concluded from this study that microgravity has little effect on the size distribution of pore fluid blobs corresponding to residual saturation of wetting fluids in porous media. The blobs showed no noticeable breakup or coalescence during microgravity. However, based on the increase in bulk volume of samples due to particle separation under microgravity, groups of particles, within which pore fluid blobs were encapsulated, appeared to have rearranged themselves under microgravity.

manned↗
NASA NTRS1994

Porous silicon carbide (SiC) semiconductor device

A semiconductor device employs at least one layer of semiconducting porous silicon carbide (SiC). The porous SiC layer has a monocrystalline structure wherein the pore sizes, shapes, and spacing are determined by the processing conditions. In one embodiment, the semiconductor device is a p-n junction diode in which a layer of n-type SiC is positioned on a p-type layer of SiC, with the p-type layer positioned on a layer of silicon dioxide. Because of the UV luminescent properties of the semiconducting porous SiC layer, it may also be utilized for other devices such as LEDs and optoelectronic devices.

Shor, Joseph S.↗
NASA NTRS2003

Pore Formation and Mobility Investigation (PPMI): Description and Initial Analysis of Experiments Conducted aboard the International Space Station

Flow visualization experiments during the controlled directional melt back and re-solidification of succinonitrile (SCN) and SCN-water mixtures were conducted using the Pore Formation and Mobility Investigation (PFMI) apparatus in the glovebox facility (GBX) aboard the International Space Station. The study samples were initially 'cast' on earth under 450 millibar of nitrogen into 1 cm ID glass sample tubes approximately 30 cm in length, containing 6 in situ thermocouples. During the Space experiments, the processing parameters and flow visualization settings are remotely monitored and manipulated from the ground Telescience Center (TSC). The ground solidified sample is first subjected to a unidirectional melt back, generally at 10 microns per second, with a constant temperature gradient ahead of the melting interface. Bubbles of different sizes are seen to initiate at the melt interface and, upon release from the melting solid, translate at different speeds in the temperature field ahead of them before coming to rest. Over a period of time these bubbles dissolve into the melt. The gas-laden liquid is then directionally solidified in a controlled manner, generally starting at a rate of 1 micron /sec. Observation and preliminary analysis of bubble formation and mobility in pure SCN samples during melt back and the subsequent structure resulting during gas generation upon re-solidification are presented and discussed.

Grugel, R. N.↗
NASA NTRS2002

Pore Formation and Mobility Investigation (PFMI): Description and Initial Analysis of Experiments Conducted aboard the International Space Station

Flow visualization experiments during the controlled directional melt back and re-solidification of succinonitrile (SCN) and SCN-water mixtures were conducted using the Pore Formation and Mobility Investigation (PFMI) apparatus in the glovebox facility (GBX) aboard the International Space Station. The study samples were initially "cast" on earth under 450 millibar of nitrogen into 1 cm ID glass sample tubes approximately 30 cm in length, containing 6 in situ thermocouples. During the Space experiments, the processing parameters and flow visualization settings are remotely monitored and manipulated from the ground Telescience Center (TSC). The ground solidified sample is first subjected to a unidirectional melt back, generally at 10 microns per second, with a constant temperature gradient ahead of the melting interface. Bubbles of different sizes are seen to initiate at the melt interface and, upon release from the melting solid, translate at different speeds in the temperature field ahead of them before coming to rest. Over a period of time these bubbles dissolve into the melt. The gas-laden liquid is then directionally solidified in a controlled manner, generally starting at a rate of 1 micron /sec. Observation and preliminary analysis of bubble formation and mobility in pure SCN samples during melt back and the subsequent structure resulting during gas generation upon re-solidification are presented and discussed.

Grugel, R. N.↗
NASA NTRS2005

Morphological Evolution of Directional Solidification Interfaces in Microgravity: An Analysis of Model Experiments Performed on the International Space Station

A series of experiments performed using the Pore Formation and Mobility Investigation (PFMI) apparatus within the glovebox facility (GBX) on board the International Space Station (ISS) has provided video images of the morphological evolution of a three-dimensional interface in a diffusion controlled regime. The experimental samples were prepared on ground by filling glass tubes, 1 cm ID and approximately 30 cm in length, with "alloys" of succinonitrile (SCN) and water in an atmosphere of nitrogen at 450 millibar pressure. The compositions of the samples processed and analyzed are 0.25,0.5 and 1.0 wt% water. Experimental processing parameters of temperature gradient and translation speed, as well as camera settings, were remotely monitored and manipulated from the ground Telescience Center (TSC) at the Marshall !3pace Flight Center. During the experiments, the sample was first subjected to a unidirectional melt back, generally at 10 microns per second, with a constant temperature gradient ahead of the melting interface. Following the melt back, the interface was allowed to stabilize before translation is initiated. The temperatures in the sample were monitored by six in situ thermocouples and the position is monitored by an optical linear encoder. For the experiments performed and analyzed, the gradients ranged from 2.5 - 3.3 K/mm and the initial pulling velocities ranged from 0.7 micron per second to 1 micron per second with subsequent transition velocities of up to 100 microns per second. The data provided by the PFMI for analysis includes near-real-time (NRT) video captured on the ground during the experiment runs, ISS Video Tape Recorder (VTR) data dumped from the VTR at the end of the experiment run and recorded on the ground, telemetry data including temperature and position measurements, and limited flight HI-8 tapes in 2 camera views of experiment runs for which tapes have been returned to the investigators from ISS. Because of limited down mass from the ISS, the majority of the initial analysis has been performed using the NRT and VTR video data but will be supplemented with the HI-8 video as it becomes available. hardware and procedures required to prepare samples for correlation to flight samples is described. Using this ground-based system, a series of experiments have been performed for direct comparison with the flight data. The results of these comparisons as well as implications to future microgravity experiments are presented and discussed. A ground-based thin-sample directional solidification system as well as all associated

Strutzenberg, Louise L.↗
NASA NTRS1994

Towards a Modern Theory of Multiphase Filtration Flow

An alternative theoretical model of joint filtration flow of immiscible incompressible fluids is presented. The model takes into account relaxation processes due to the interchange of the fluids between pores of difference sizes which is driven by capillary forces. The fluids occupy connected regions in a four-dimensional space formed by three coordinates and the pore length scale. When the fluid exchange between pores of given sizes is effected by way of successive flow through pores of all the intermediate sizes, the pressure within each region is governed by a hyperbolic equation, the role of time being played by the pore linear scale. Pressure jumps across hypersurfaces separating the regions equal corresponding values of the capillary pressure. A supplementary condition at any such hypersurface requires the speed of its displacement in the four-dimensional space to coincide with the normal velocity components of both the adjoining fluids. As a result, a principally new statement of multiphase filtration flow problems is gained with allowance for capillary relaxation in the porous space.

Buyevich, Yu A.↗
NASA NTRS2004

Direct Observation of Pore Formation and Bubble Mobility during Controlled Melting and Resolidification in Microgravity

Detailed studies on the controlled melting and subsequent re-solidification of succinonitrile were conducted in the microgravity environment aboard the International Space Station (ISS) using the PFMI apparatus (Pore Formation and Mobility Investigation) located in the ISS glovebox facility (GBX). Samples were initially prepared on ground by filling glass tubes, 1 cm ID and approximately 30 cm in length, with pure succinonitrile (SCN) under 450 millibar of nitrogen. During Space processing, experimental parameters like temperature gradient and translation speed, for melting and solidification, were remotely monitored and controlled from the ground Telescience Center (TSC) at the Marshall Space Flight Center. Real time visualization during controlled melting revealed bubbles of different sizes initiating at the solid/liquid interface, and traveling up the temperature gradient ahead of them. Subsequent controlled re-solidification of the SCN revealed the details of porosity formation and evolution. A preliminary analysis of the melt back and re- solidification and its implications to future microgravity materials processing is presented and discussed.

Grugel, Richard N.↗
NASA NTRS2003

Pore Formation and Mobility Investigation (PFMI): Description and Initial Analysis of Experiments Conducted Aboard the International Space Station

Flow Visualization experiments on the controlled melting and solidification of succinonitrile were conducted in the glovebox facility of the International Space Station (ISS). The experimental samples were prepared on ground by filling glass tubes, 1 cm 1D and approximately 30 cm in length, with pure succinonitrile (SCN) under 450 millibar of nitrogen. Porosity in the samples arose from natural shrinkage, and in some cases by direct insertion of nitrogen bubbles, during solidification of the liquid SCN. The samples were processed in the Pore Formation and Mobility Investigation (PFMI) apparatus that is placed in the glovebox facility (GBX) aboard the ISS. Experimental processing parameters of temperature gradient and translation speed, as well as camera settings, were remotely monitored and manipulated from the ground Telescience Center (TSC) at the Marshall Space Flight Center. During the experiments, the sample is first subjected to a unidirectional melt back, generally at 10 microns per second, with a constant temperature gradient ahead of the melting interface. The temperatures in the sample are monitored by six in situ thermocouples. Real time visualization of the controlled directional melt back shows bubbles of different sizes initiating at the melt interface and, upon dislodging from the melting solid, migrating at different speeds into the temperature field ahead of them, before coming to rest. The thermocapillary flow field set up in the melt, ahead of the interface, is dramatic in the context of the large bubbles, and plays a major role in dislodging the bubble. A preliminary analysis of the observed bubble formation and mobility during melt back and its implication to future microgravity experiments is presented and discussed.

Grugel, R. N.↗
NASA NTRS1995

Investigation of Advanced Processed Single-Crystal Turbine Blade Alloys

This investigation studied the influence of thermal processing and microstructure on the mechanical properties of the single-crystal, nickel-based superalloys PWA 1482 and PWA 1484. The objective of the program was to develop an improved single-crystal turbine blade alloy that is specifically tailored for use in hydrogen fueled rocket engine turbopumps. High-gradient casting, hot isostatic pressing (HIP), and alternate heat treatment (HT) processing parameters were developed to produce pore-free, eutectic-free microstructures with different (gamma)' precipitate morphologies. Test materials were cast in high thermal gradient solidification (greater than 30 C/cm (137 F/in.)) casting furnaces for reduced dendrite arm spacing, improved chemical homogeneity, and reduced interdendritic pore size. The HIP processing was conducted in 40 cm (15.7 in.) diameter production furnaces using a set of parameters selected from a trial matrix study. Metallography was conducted on test samples taken from each respective trial run to characterize the as-HIP microstructure. Post-HIP alternate HT processes were developed for each of the two alloys. The goal of the alternate HT processing was to fully solution the eutectic gamma/(gamma)' phase islands and to develop a series of modified (gamma)' morphologies for subsequent characterization testing. This was accomplished by slow cooling through the (gamma)' solvus at controlled rates to precipitate volume fractions of large (gamma)'. Post-solution alternate HT parameters were established for each alloy providing additional volume fractions of finer precipitates. Screening tests included tensile, high-cycle fatigue (HCF), smooth and notched low-cycle fatigue (LCF), creep, and fatigue crack growth evaluations performed in air and high pressure (34.5 MPa (5 ksi)) hydrogen at room and elevated temperature. Under the most severe embrittling conditions (HCF and smooth and notched LCF in 34.5 MPa (5 ksi) hydrogen at 20 C (68 F), screening test results showed increases in fatigue life typically on the order of 1OX, when compared to the current Space Shuttle Main Engine (SSME) Alternate Turbopump (AT) blade alloy (PWA 1480).

Peters, B. J.↗
NASA NTRS2003

SUBSA and PFMI Transparent Furnace Systems Currently in use in the International Space Station Microgravity Science Glovebox

The Solidification Using a Baffle in Sealed Ampoules (SUBSA) and Pore Formation and Mobility Investigation (PFMI) furnaces were developed for operation in the International Space Station (ISS) Microgravity Science Glovebox (MSG). Both furnaces were launched to the ISS on STS-111, June 4, 2002, and are currently in use on orbit. The SUBSA furnace provides a maximum temperature of 850 C and can accommodate a metal sample as large as 30 cm long and 12mm in diameter. SUBSA utilizes a gradient freeze process with a minimum cooldown rate of 0.5C per min, and a stability of +/- 0.15C. An 8 cm long transparent gradient zone coupled with a Cohu 3812 camera and quartz ampoule allows for observation and video recording of the solidification process. PFMI is a Bridgman type furnace that operates at a maximum temperature of 130C and can accommodate a sample 23cm long and 10mm in diameter. Two Cohu 3812 cameras mounted 90 deg apart move on a separate translation system which allows for viewing of the sample in the transparent hot zone and gradient zone independent of the furnace translation rate and direction. Translation rates for both the cameras and furnace can be specified from 0.5micrometers/sec to 100 micrometers/sec with a stability of +/-5%. The two furnaces share a Process Control Module (PCM) which controls the furnace hardware, a Data Acquisition Pad (DaqPad) which provides signal condition of thermal couple data, and two Cohu 3812 cameras. The hardware and software allow for real time monitoring and commanding of critical process control parameters. This paper will provide a detailed explanation of the SUBSA and PFMI systems along with performance data and some preliminary results from completed on-orbit processing runs.

Spivey, Reggie A.↗
NASA NTRS2006

Materials Research Conducted Aboard the International Space Station: Facilities Overview, Operational Procedures, and Experimental Outcomes

The Microgravity Science Glovebox (MSG) and Maintenance Work Area (MWA) are facilities aboard the International Space Station (ISS) that were used to successfully conduct experiments in support of, respectively, the Pore Formation and Mobility Investigation (PFMI) and the In-Space Soldering Investigation (ISSI). The capabilities of these facilities are briefly discussed and then demonstrated by presenting real-time and subsequently down-linked video-taped examples from the abovementioned experiments. Data interpretation, ISS telescience, some lessons learned, and the need of such facilities for conducting work in support of understanding materials behavior, particularly fluid processing and transport scenarios, in low-gravity environments is discussed.

Grugel, R. N.↗
NASA NTRS2007

Materials Research Conducted Aboard the International Space Station: Facilities Overview, Operational Procedures, and Experimental Outcomes

The Microgravity Science Glovebox (MSG) and Maintenance Work Area (MWA) are facilities aboard the International Space Station (ISS) that were used to successfully conduct experiments in support of, respectively, the Pore Formation and Mobility Investigation (PFMI) and the In-Space Soldering Investigation (ISSI). The capabilities of these facilities are briefly discussed and then demonstrated by presenting "real-time" and subsequently down-linked video-taped examples from the abovementioned experiments. Data interpretation, ISS telescience, some lessons learned, and the need of such facilities for conducting work in support of understanding materials behavior, particularly fluid processing and transport scenarios, in low-gravity environments is discussed.

Grugel, Richard N.↗
NASA NTRS2013

Bulk Moisture and Salinity Sensor

Measurement and feedback control of nutrient solutions in plant root zones is critical to the development of healthy plants in both terrestrial and reduced-gravity environments. In addition to the water content, the amount of fertilizer in the nutrient solution is important to plant health. This typically requires a separate set of sensors to accomplish. A combination bulk moisture and salinity sensor has been designed, built, and tested with different nutrient solutions in several substrates. The substrates include glass beads, a clay-like substrate, and a nutrient-enriched substrate with the presence of plant roots. By measuring two key parameters, the sensor is able to monitor both the volumetric water content and salinity of the nutrient solution in bulk media. Many commercially available moisture sensors are point sensors, making localized measurements over a small volume at the point of insertion. Consequently, they are more prone to suffer from interferences with air bubbles, contact area of media, and root growth. This makes it difficult to get an accurate representation of true moisture content and distribution in the bulk media. Additionally, a network of point sensors is required, increasing the cabling, data acquisition, and calibration requirements. measure the dielectric properties of a material in the annular space of the vessel. Because the pore water in the media often has high salinity, a method to measure the media moisture content and salinity simultaneously was devised. Characterization of the frequency response for capacitance and conductance across the electrodes was completed for 2-mm glass bead media, 1- to 2-mm Turface (a clay like media), and 1- to 2-mm fertilized Turface with the presence of root mass. These measurements were then used to find empirical relationships among capacitance (C), the dissipation factor (D), the volumetric water content, and the pore water salinity.

Nurge, Mark↗
NASA NTRS2003

Pore Formation and Mobility Investigation (PFMI): Concept, Hardware Development, and Initial Analysis of Experiments Conducted Aboard the International Space Station

Porosity in the form of "bubbles and pipes" can occur during controlled directional solidification processing of metal alloys. This is a consequence that 1) precludes obtaining any meaningful scientific results and 2) is detrimental to desired material properties. Unfortunately, several Microgravity experiments have been compromised by porosity. The intent of the PFMl investigation is to conduct a systematic effort directed towards understanding porosity formation and mobility during controlled directional solidification (DS) in a microgravity environment. PFMl uses a pure transparent material, succinonitrile (SCN), as well as SCN "alloyed" with water, in conjunction with a translating temperature gradient stage so that direct observation and recording of pore generation and mobility can be made. PFMl is investigating the role of thermocapillary forces and temperature gradients in affecting bubble dynamics as well as other solidification processes in a microgravity environment. This presentation will cover the concept, hardware development, operations, and the initial results from experiments conducted aboard the International Space Station.

Grugel, Richard N.↗
NASA NTRS1980

Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy

Hot isostatically pressed powder metallurgy Astroloy was obtained which contained 1.4 percent fine porosity at the grain boundaries produced by argon entering the powder container during pressing. This material was tested at 650 C in fatigue, creep fatigue, tension, and stress-rupture and the results compared with previous data on sound Astroloy. The pores averaged about 2 micrometers diameter and 20 micrometers spacing. They did influence fatigue crack initiation and produced a more intergranular mode of propagation. However, fatigue life was not drastically reduced. A large 25 micrometers pore in one specimen resulting from a hollow particle did not reduce life by 60 percent. Fatigue behavior of the porous material showed typical correlation with tensile behavior. The plastic strain range life relation was reduced proportionately with the reduction in tensile ductility, but the elastic strain range-life relation was little changed reflecting the small reduction in sigma sub u/E for the porous material.

Miner, R. V., Jr.↗