Search NASA⌕ Search

SEARCH · Search NASA

Results for “INCONEL”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Best Practices for Shielding Analyses of Activated Metals and Spent Resins from Reactor Operation

This report investigated best practices for performing shielding evaluations of Type B waste packages, as defined in 10 CFR Part 71 regulations on packaging and transportation of radioactive material, or packages for which the contents are not defined before loading and may include a broad range of nuclides, geometries, and non-fuel materials. The following non-fuel waste streams were analyzed: Activated metals from decommissioned commercial power reactors, including Type 304 stainless steel, reactor vessel steel, and Inconel, Control blades from boiling water reactors, Neutron-activated corrosion products on surfaces of activated metals, and Spent resins from power plant operations. Measured elemental compositions, including major constituents and impurities, for steel and Inconel samples from commercial power reactors were used in activation calculations to determine radionuclide inventories in activated metals. For a simplified cask model, 60 Co contribution to the total external package dose rate at 30 days after shutdown varied from approximately 60% to 95%, depending on the activated metal, initial cobalt impurity concentration in the metal, and the thickness of the overpack gamma shield. Its maximum contribution to the total external package dose rate of approximately 100% was reached within the time interval of 2 to 5 years after shutdown and was maintained for up to 45 to 60 years after shutdown, depending on material, initial cobalt impurity concentration, and shield thickness. Thereafter, the 60 Co contribution to external package dose rate decreased with increasing decay time. Cobalt-60 is primarily produced by neutron reactions with the cobalt impurity in steel and Inconel. Other important radionuclides in activated metals contributing to package external dose rate are radionuclides with relatively short decay times, including 51 Cr, 59 Fe, 58 Co, and 54 Mn. These radionuclides may be represented as an equivalent 60 Co activity/source because 60 Co gamma ray emissions are bounding in terms of source strength and energy to other important radionuclides identified in the analyzed activated metals. Approaches for modeling the neutron-activated corrosion products that may be attached to activated reactor components were analyzed in this report. It was demonstrated that a surface source is more conservative than a uniform volumetric source for the treatment of neutron-activated corrosion products with respect to external package dose rates. An analysis of the maximum radionuclide loadings reported on spent resins identified the radionuclides 137 Cs, 60 Co, 134 Cs, 65 Zn, and 58 Co as the primary contributors to external package dose rate. For a resin cooled for 3.08 years, the external package dose rate was entirely produced by the reported 137 Cs and 60 Co inventory. The neutron sources from actinides found on spent resins or activated metals produced negligible dose rates and may be ignored in dose rate analyses. Effects of idealized waste material, source geometry, and spatial material/source distributions on external package dose rates were determined based on dose rate results for a simplified cask model under normal conditions of transport. Type 304 stainless steel, zirconium, and aluminum with adjusted mass densities based on a maximum content weight were analyzed for material modeling effects on external package dose rate. These materials produced identical external package dose rates within the statistical uncertainties of the dose rate estimates. Among four different source geometry configurations with homogeneous material of different mass densities, uniform volumetric source distribution, and the same source strength, the geometry configuration with lowest mass density (i.e., minimum self-shielding effect among the four cases) was most conservative. Spatial source distributions that better represent localized peak 60 Co activity values were more conservative than a uniform volumetric source distribution, assuming the same weight and total source strength per package. The increase in external dose rate caused by localized source peaks can be as much as the ratio between source peak activity density to average activity density, depending on the location of the activated metal with peak activity density. Therefore, the shielding analysis may be simplified if localized peak activities and the average activity per package can be measured/determined and documented at the time of cask loading. For simplicity, external package dose rates may be determined based on average source activity and a uniform volumetric source distribution. The dose rate results from that calculation model multiplied by the ratio of peak activity density to average activity density will produce maximum dose rate values for conservative estimates.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Application of Refractory High-Entropy Alloys for Higher-Reliability and Higher-Efficiency Brayton Cycles and Advanced Nuclear Reactors

An exceptional set of newly-discovered advanced superalloys known as refractory high-entropy alloys (RHEAs) can provide near-term solutions for wear, erosion, corrosion, high-temperature strength, creep, and radiation issues associated with supercritical carbon dioxide (sCO2) Brayton Cycles and advanced nuclear reactors. In particular, these superalloys can significantly extend their durability, reliability, and thermal efficiency, thereby making them more cost-competitive, safer, and reliable. For this project, it was endeavored to manufacture and test certain RHEAs, to solve technical issues impacting the Brayton Cycle and advanced nuclear reactors. This was achieved by leveraging Sandia’s patents, technical advances, and previous experience working with RHEAs. Herein, three RHEA manufacturing methods were applied: laser engineered net shaping, spark plasma sintering, and spray coating. Two promising RHEAs were selected, HfNbTaZr and MoNbTaVW. To demonstrate their performance, erosion, structural, radiation, and hightemperature experiments were conducted on the RHEAs, stainless steel (SS) 316 L, SS 1020, and Inconel 718 test coupons, as well as bench-top components. The experimental data is presented, analyzed, and confirms the superior performance of the HfNbTaZr and MoNbTaVW RHEAs vs. SS 316 L, SS 1020, and Inconel 718. In addition, to gain more insights for larger-scale RHEA applications, the erosion and structural capabilities for the two RHEAs were simulated and compared with the experimental data. The experimental data confirm the superior performance of the HfNbTaZr and MoNbTaVW RHEAs vs. SS and Inconel. Most importantly, the erosion and the coating material experimental data show that erosion in sCO2 Brayton Cycles can be eliminated completely if RHEAs are used. The experimental suite and validations confirm that HfNbTaZr is suitable for harsh environments that do not include nuclear radiation, while MoNbTaVW is suitable for harsh environments that include radiation.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2023

Conjugate Heat Transfer Analysis in Pressurized Helium Gas Cooling Channels

Los Alamos National Laboratory (LANL) is working with NorthStar Medical Radioisotopes (NMR) on their efforts to produce Mo-99 from the irradiation of Mo-100 targets. The NMR target consists of an Inconel window that allows the electron beam to penetrate and irradiate a stack of Mo-100 disks. The irradiation process generates large amounts of heat and is cooled using pressurized helium gas flowing at 400 g/s. LANL provides both numerical analysis support and experimental support. Computational fluid dynamics (CFD) and conjugate heat transfer (CHT) analysis are performed on the NMR target to analyze the helium flow and volumetric heating through the NMR system. In this iteration of numerical analysis, we update the Mo-100 disk thickness to 0.74 mm and the gap between the Inconel window and the first disk to 0.69 mm. Estimates of the heat flux from the electron beams from Monte Carlo N-Particle code (MCNP) analysis were combined with CFD to perform the CHT analysis. The pressure drop through the targets, force applied on the first disk, beam window and target disk temperatures are some of the quantities estimated using the simulations. The pressure drop through the target was estimated as 0.198 MPa, while the force due to venturi effects across the first disk was estimated to be 100 N. The results show maximum window temperatures over 600 °C and peak disk temperatures over 1600 °C. Past work has shown that beyond 650-700 °C, the Inconel window becomes susceptible to yield and rupture. The increased temperature in these results reduces the margin of error possible on beam spot size. The disk temperatures showed a sinusoidal distribution with the 6 th – 8 th disk from each window exhibiting highest disk temperatures. The peak temperature of the stainless steel housing was close to 316 °C and that of the laminations and spacers was approximately 582 °C.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Flow Induced Vibration Studies in Pressurized Helium Gas Cooling Channels

Production of metastable Technetium-99 (Tc-99m), a radioactive tracer that emits gamma rays, is vital to the medical imaging community. Tc-99m is extracted from the decay of Molybdenum-99 (Mo-99) which has a half-life of about 2-3 days. The work presented in this report is part of the NNSA’s mission to produce Mo-99 commercially, within the US, without the use of highly enriched uranium (HEU) in support of nonproliferation and global security. Los Alamos National Laboratory (LANL) is working with NorthStar Medical Radioisotopes (NMR) on their efforts to produce Mo-99 through the irradiation of Mo-100 targets using an electron beam. The NMR target comprises a stack of approximately 60-70 Mo-100 disks with diameter 24 mm and thickness 0.74 mm held in stainless steel laminations, each separated using 0.25 mm thick stainless steel spacers. The symmetric target stack is housed in an Inconel vessel with two Inconel windows on either side. Two electron accelerators are used to produce 40 MeV, 3.16 µA electron beams each that penetrate the Inconel windows and irradiate the Mo-100 disks. Approximately 90% of the total 250 kW beam power is deposited in the NMR target during the irradiation process. During irradiation, pressurized helium gas flows through 0.25 mm thin gaps between the disks cooling the beam window, target disks, disk laminations and spacers. Both NMR and LANL have found during cold testing of the target system (no heat deposition) that the Mo-100 disks undergo significant mass loss and disk breakage due to vibrations induced by the flowing helium gas. The mass loss is not only undesirable due to monetary loss from reduced final quantities of Mo-99, but also due to the hazards associated with radioactive material trapped in the cooling lines and particle filters. The effect of flow rate and target geometry on the flow induced vibrations need to be quantified, and recommendations provided to minimize this mass loss. This work describes LANL’s experimental characterization of the flow induced vibrations and disk mass loss in a reduced scale set-up containing 10 Mo-100 disks. We use high speed imaging, displacement measurements and microphone measurements combined with signal processing to estimate the vibration frequency of each disk. The effect of disk thickness, target fit and duration of testing on the mass loss is described. We find that in the current configuration of NMR targets, the vibrations and mass loss on the first disk are minimized, while those in the adjacent disks are highest. The microphone and high-speed image data show that increased flow rates and increased duration of testing increases vibration frequency and mass loss. The mass loss is due to both disk rotation and back and forth motion. There are visible wear marks on the disks with the highest mass loss. We also note that the current NMR window gap reduces flow induced vibrations compared to the previous smaller gaps. Longer duration testing will provide more data and verification for the findings presented in this report. The work will be continued in FY 24.

43 PARTICLE ACCELERATORS↗
NASA NTRS1962

LUBRICATING PROPERTIES OF CERAMIC-BONDED CALCIUM FLUORIDE COATINGS ON NICKEL-BASE ALLOYS FROM 75 DEG TO 1900 DEG F

The endurance life and the friction coefficient of ceramic-bonded calcium fluoride (CaF2) coatings on nickel-base alloys were determined at temperatures from 75° to 1900° F. The specimen configuration consisted of a hemispherical rider (3/16-in. rad.) sliding against the flat surface of a rotating disk. Increasing the ambient temperature (up to 1500° F) or the sliding velocity generally reduced the friction coefficient and improved coating life. Base-metal selection was critical above 1500° F. For instance, cast Inconel sliding against coated Inconel X was lubricated effectively to 1500° F, but at 1600° F severe blistering of the coatings occurred. However, good lubrication and adherence were obtained for René 41 sliding against coated René 41 at temperatures up to 1900° F; no blisters developed, coating wear life was fairly good, and the rider wear rate was significantly lower than for the unlubricated metals . Friction coefficients were 0.12 at 1500° F, 0.15 at 1700° F, and 0.17 at 1800° and 1900° F. Because of its ready availability, Inconel X appears to be the preferred substrate alloy for applications in which the temperature does not exceed 1500° F. René 41 would have to be used in applications involving higher temperatures. Improved coating life was derived by either preoxidizing the substrate metals prior to the coating application or by applying a very thin (<0.0002 in.) burnished and sintered overlay to the surface of the coating. Preoxidation did not affect the friction coefficient. The overlay generally resulted i n a higher friction coefficient than that obtained without the overlay. The combination of both modifications resulted in longer coating life and in friction coefficients intermediate between those obtained with either modification alone.

Nickel alloy↗
NASA NTRS1978

Electron emission from nickel-alloy surfaces in cesium vapor

An experimental apparatus and measurement techniques are described for measuring the thermionic emission from cesium-activated materials having adequate high-temperature properties such as creep strength and corrosion resistance, which might ultimately reduce the cost of thermionic converters. The electron emission characteristics are measured for nickel, Inconel 600, and Hastelloy X probes with a 412 K cesium reservoir. It is found that the nickel alloys exhibit a peak electron emission 1.4 to 2.1 times greater than pure nickel. Both the Inconel and the Hastelloy samples have work functions of 1.64 eV at peak emission. The minimum cesiated work functions are estimated to be 1.37 eV for Inconel at a probe temperature of 750 K and 1.4 eV for Hastelloy at a probe temperature of 665 K. The bare work functions for both alloys is estimated to be about the same as for pure nickel, 4.8 eV.

Manda, M.↗
NASA NTRS1978

Electron emission from nickel-alloy surfaces in cesium vapor

The cesiated electron emission was measured for three candidate electrodes for use as collectors in thermionic converters. Nickel, Inconel 600 and Hastelloy were tested with a 412 K cesium reservoir. Peak emission from the alloys was found to be comparable to that from pure nickel. Both the Inconel and the Hastelloy samples had work functions of 1.64 eV at peak emission. The minimum work functions were estimated to be 1.37 eV at a probe temperature of 750 K for Inconel and 1.40 eV for Hastelloy at 665 K. The bare work function for both alloys is estimated to be approximately the same as for pure nickel, 4.8 eV.

Manda, M.↗
NASA NTRS1984

Ceramic-to-metal bonding for pressure transducers

A solid-state diffusion technique involving the placement of a gold foil between INCONEL X-750 and a machinable glass-ceramic "MACOR" was shown to be successful in bonding these two materials. This technique was selected after an exhaustive literature search on ceramic-metal bonding methods. Small expansion mismatch between the Inconel and the MACOR resulted in fracture of the MACOR when the bonded body was subjected to tensile stress of 535 psi. The bonded parts were submitted to a cyclic loading test in an air atmosphere at 1 Hz from 0 to 60 KPa. Failure was observed after 700,000 cycles at 650 C. Ceramic-Inconel bonding was not achieved with this method for boron nitride and silica glass.

Mackenzie, J. D.↗
NASA NTRS1988

Spray automated balancing of rotors: Methods and materials

The work described consists of two parts. In the first part, a survey is performed to assess the state of the art in rotor balancing technology as it applies to Army gas turbine engines and associated power transmission hardware. The second part evaluates thermal spray processes for balancing weight addition in an automated balancing procedure. The industry survey reveals that: (1) computerized balancing equipment is valuable to reduce errors, improve balance quality, and provide documentation; (2) slow-speed balancing is used exclusively, with no forseeable need for production high-speed balancing; (3) automated procedures are desired; and (4) thermal spray balancing is viewed with cautious optimism whereas laser balancing is viewed with concern for flight propulsion hardware. The FARE method (Fuel/Air Repetitive Explosion) was selected for experimental evaluation of bond strength and fatigue strength. Material combinations tested were tungsten carbide on stainless steel (17-4), Inconel 718 on Inconel 718, and Triballoy 800 on Inconel 718. Bond strengths were entirely adequate for use in balancing. Material combinations have been identified for use in hot and cold sections of an engine, with fatigue strengths equivalent to those for hand-ground materials.

Smalley, Anthony J.↗
NASA NTRS1989

Study of metal corrosion using ac impedance techniques in the STS launch environment

AC impedance measurements were performed to investigate the corrosion resistance of 19 alloys under conditions similar to the STS launch environment. The alloys were: Zirconium 702, Hastelloy C-22, Inconel 625, Hastelloy C-276, Hastelloy C-4, Inconel 600, 7Mo + N, Ferralium 255, Inco Alloy G-3, 20Cb-3, SS 904L, Inconel 825, SS 304LN, SS 316L, SS 317L, ES 2205, SS 304L, Hastelloy B-2, and Monel 400. AC impedance data were gathered for each alloy after one hour immersion time in each of the following three electrolyte solutions: 3.55 percent NaCl, 3.55 percent NaCl-0.1N HCl, and 3.55 percent NaCl-1.0N HCl. The data were analyzed qualitatively using the Nyquist plot and quantitatively using the Bode plot. Polarization resistance, Rp, values were obtained using the Bode plot. Zirconium 702 was the most corrosion resistant alloy in the three electrolytes. The ordering of the other alloys according the their resistance to corrosion varied as the concentration of hydrochloric acid in the electrolyte increased. The corrosion resistance of Zirconium 702 and Ferralium 255 increased as the concentration of hydrochloric acid in the electrolyte increased. The corrosion resistance of the other 17 alloys decreased as the concentration of the hyrdochloric acid in the electrolyte increased.

Calle, Luz M.↗
NASA NTRS1992

Properties data for opening the Galileo's partially unfurled main antenna

An investigation was conducted into the friction and wear behavior of both unlubricated and dry-film-lubricated (Tiolube 460) titanium alloy (Ti-6Al-4V) in contact with an uncoated high-nickel-content superalloy (Inconel 718) both in vacuum and in air. The acquisition of friction and wear data for this sliding couple was motivated by the need for input data for the 'antenna stuck ribs model' effort to free Galileo's High Gain Antenna. The results of the investigation indicate that galling occurred in the unlubricated system in vacuum and that the coefficient of friction increased to 1.2. The abnormally high friction (1.45) was observed when relatively large wear debris clogged at the sliding interface. The coefficient of friction for the dry-film-lubricated system in vacuum is 0.04, while the value in air is 0.13. The endurance life of the dry-film lubricant is about three orders of magnitude greater in vacuum than in air. The worn surfaces of the dry-film-lubricated Ti-6Al-4V pin and Inconel 718 disk first run in humid air and then rerun in vacuum was completely different from that of the pin and disk run only in vacuum. When galling occurred in the humid-air and vacuum contact, coefficient of friction rose to 0.32 when sliding in humid air and to 1.4 when sliding in vacuum. The galling was accompanied by severe surface damage and extensive transfer of the Ti-6Al-4V to the Inconel 718, or vice versa. When spalling occurred in the dry-film-lubricated Ti-6Al-4V pin run only in vacuum, the coefficient of friction rose to 0.36 or greater. The wear damage caused by spalling can self-heal when rerun in vacuum - the coefficient of friction decreased to 0.05. The friction and wear data obtained can be used for the 'antenna stuck ribs model' effort to free Galileo's high gain antenna.

Miyoshi, Kazuhisa↗
NASA NTRS1957

Rupture Strength of Several Nickel-base Alloys in Sheet Form

The 100-hour rupture strengths of Inconel X, Inconel 700, Incoloy 901, Refractaloy 26, and R-235 at 1200 and 1350 F. in both the annealed and heat-treated conditions were determined. Inconel 700 had the highest rupture strength at both temperatures; Incoloy 901 was second strongest at 1200 F, and R-235 second strongest at 1350 F. With the exception of Incoloy 901, ductility was low. Photomicrographs show that fractures are through the grain boundaries. Results are compared with published data for other sheet alloys and bar stock.

ALLOYS, HEAT-RESISTING↗
NASA NTRS1962

Lubricating Properties of Ceramic-Bonded Calcium Fluoride Coatings on Nickel-Base Alloys from 75 to 1900 deg F

The endurance life and the friction coefficient of ceramic-bonded calcium fluoride (CaF2) coatings on nickel-base alloys were determined at temperatures from 75 F to 1900 F. The specimen configuration consisted of a hemispherical rider (3/16-in. rad.) sliding against the flat surface of a rotating disk. Increasing the ambient temperature (up to 1500 F) or the sliding velocity generally reduced the friction coefficient and improved coating life. Base-metal selection was critical above 1500 F. For instance, cast Inconel sliding against coated Inconel X was lubricated effectively to 1500 F, but at 1600 F severe blistering of the coatings occurred. However, good lubrication and adherence were obtained for Rene 41 sliding against coated Rene 41 at temperatures up to 1900 F; no blisters developed, coating wear life was fairly good, and the rider wear rate was significantly lower than for the unlubricated metals. Friction coefficients were 0.12 at 1500 F, 0.15 at 1700 F, and 0.17 at 1800 F and 1900 F. Because of its ready availability, Inconel X appears to be the preferred substrate alloy for applications in which the temperature does not exceed 1500 F. Rene 41 would have to be used in applications involving higher temperatures. Improved coating life was derived by either preoxidizing the substrate metals prior to the coating application or by applying a very thin (less than 0.0002 in.) burnished and sintered overlay to the surface of the coating. Preoxidation did not affect the friction coefficient. The overlay generally resulted in a higher friction coefficient than that obtained without the overlay. The combination of both modifications resulted in longer coating life and in friction coefficients intermediate between those obtained with either modification alone.

Sliney, Harold E.↗
NASA NTRS1961

Optimum Design of Insulated Compression Plates Subjected to Aerodynamic Heating

A method to determine the optimum thicknesses of insulation and load-carrying structure has been applied to insulated compression plates subjected to aerodynamic heating. The optimum design results in the lowest combined weight of insulation and load-carrying plate. Load parameters which included the imposed load, insulation conductivity and density, and flight time were found for design strength criteria of compressive yield, compressive buckling, and postbuckling failure. Charts of optimum total weight were prepared for 2024-T3 aluminum alloy, HK3lA magnesium alloy, 17-7 PH stainless steel, and Inconel X for each design criterion. The results show that 17-7 PH stainless steel and Inconel X are most efficient for compressive yield stress and that HK3lA magnesium is most efficient for buckling. HK31A magnesium is also most efficient for the postbuckling failure criterion except under conditions of light loading and long flight periods; under such conditions uninsulated Inconel X may be superior for environmental temperature less than 1,200 F. Insulated magnesium is more efficient than insulated aluminum because the lower density of magnesium permits the use of thick plates with large heat capacity. When more than one failure mode was applied to a design, it was found that the minimum weight structure was one in which all modes of failure occurred at the design load.

Davidson, John R.↗
NASA NTRS2005

Permeability of Candidate Stirling Heater Head Materials Measured

Researchers at the NASA Glenn Research Center are evaluating high-temperature materials for Stirling heater heads for second- and third-generation Stirling radioisotope power systems that would help to increase the system efficiency to 30 to 35 percent and the system specific power to 8 to 10+ W/kg. Ceramic materials could make it possible for the convertor hot-end temperature to be increased to 1050 to 1200 C, in comparison to the current 650 C with an Inconel 718 heater head. A hermetically sealed Stirling heater head must retain a constant internal pressure of nearly 400-psi helium (He) throughout its useful life (120,000 hr) at the design operating temperature. Therefore, He permeability was measured for eight potential materials and compared with the permeability of the current heater head material, Inconel 718. The eight materials included silicon nitride (Si3N4), silicon dioxide (SiO2), both sintered and chemical vapor deposited (CVD) silicon carbide (SiC), alumina (Al2O3), two types of melt-infiltrated (MI) SiC/SiC composites, and a carbon/SiC composite (C/SiC). Glenn submitted samples of each material to Porous Materials, Inc., Ithaca, New York, for permeability analysis. At room temperature and 30-psi He, four materials--Si3N4, Al2O3, SiO2, and sintered SiC--demonstrated lower permeability than Inconel 718. The CVD SiC and all the composite materials were significantly more permeable to He than the baseline material.

Freedman, Marc R.↗
NASA NTRS2015

Development of Long-Lifetime Pulsed Gas Valves for Pulsed Electric Thrusters

It is advantageous for gas-fed pulsed electric thrusters to employ pulsed valves so propellant is only flowing to the device during operation. The propellant utilization of the thruster will be maximized when all the gas injected into the thruster is acted upon by the fields produced by the electrical pulse. Gas that is injected too early will diffuse away from the thruster before the electrical pulse can act to accelerate the propellant. Gas that is injected too late will miss being accelerated by the already-completed electrical pulse. As a consequence, the valve must open quickly and close equally quickly, only remaining open for a short duration. In addition, the valve must have only a small amount of volume between the sealing body and the thruster so the front and back ends of the pulse are as coincident as possible with the valve cycling, with very little latent propellant remaining in the feed lines after the valve is closed. For a real mission of interest, a pulsed thruster can be expected to pulse at least 10(exp 10) - 10(exp 11) times, setting the range for the number of times a valve must open and close. The valves described in this paper have been fabricated and tested for operation in an inductive pulsed plasma thruster (IPPT) for in-space propulsion. In general, an IPPT is an electrodeless space propulsion device where a capacitor is charged to an initial voltage and then discharged, producing a high-current pulse through a coil. The field produced by this pulse ionizes propellant, inductively driving current in a plasma located near the face of the coil. Once the plasma is formed, it can be accelerated and expelled at a high exhaust velocity by the electromagnetic Lorentz body force arising from the interaction of the induced plasma current and the magnetic field produced by the current in the coil. The valve characteristics needed for the IPPT application require a fast-acting valve capable of a minimum of 10(exp 10) valve actuation cycles. Since even 10(exp 9) cycles is well above anything demonstrated, this lower value was selected as the design point for the present work. The valve seal must remain leak-tight throughout operation, and the body must maintain a low internal leakage at relatively high operating temperatures. The full set of design requirements used for this program are summarized in Table 1. In this work, we describe two pulsed gas valves that have been fabricated to have long lifetime and demonstrate the characteristics listed above. The first is a miniaturized, conventional electromagnet-based valve while the second is a piezoelectric-based valve design. The conventional valve, shown in Fig. 1, is opened by use of a solenoid electromagnetic actuator. When current is applied to the solenoid coil, magnetic forces pull the plunger away from the valve seat, allowing fluid to flow through the valve. Removal of electrical current permits the spring and fluid pressure to seat the plunger, halting the flow of fluid. The valve body is fabricated from 304L corrosion resistant steel (CRES) and while the parts that form the magnetic circuit are fabricated from 430 CRES. This material does not have optimum magnetic properties, but its corrosion resistance permits incorporation into a design without requiring an additional plating process. A viton O-ring compound (Parker V0884-75), selected for its mechanical strength at elevated temperatures, was used for the valve seat seal. The design was based solely on the use of analytical sizing calculations, as opposed to a more rigorous finite element analysis. While this valve is small and relatively lightweight, it does not represent a design that is optimized for mass and/or a given volume envelope. The piezoelectric valve is a "puller" valve design. Applying a voltage to the piezo crystal causes it to elongate and pull a pintle off the seat, opening the valve. The valve seal consists of the pintle with an external, spherically-formed tip fabricated from Inconel 625 and the seat fabricated from Inconel 718 and possessing a spherical surface that permits the pintle to align with the valve body centerline after each cycle, maintaining the circumferential metal-on-metal seal. The contact stress on the valve pintle is expected in the worst case to be 96.5 MPa (14 ksi), which is well below the work hardening value of 413.7 MPa (60 ksi) for Inconel 615. Results presented in this work will compare the performance of each valve, both to each other and to the valve design requirements given in Table 1. In general, both valves meet all the performance envelope requirements, but the piezoelectric valve consumes considerably less power and has a faster response time over the conventional solenoid-driven valves.

Burkhardt, Wendel M.↗
NASA NTRS2019

A Simple Transient Thermal Test Assembly for Insulation Materials

A simple transient thermal test was developed for evaluating the thermal performance of high-temperature flexible insulation materials in atmospheric pressure air. The test setup was inspired by the test assembly used for evaluating the performance of fire shelters and fire protective clothing. The heating source used was a burner supplied with propane gas that can generate relatively uniform heating over a wide area. The ratio of the in-plane width to thickness of the insulation test sample in the test assembly was selected to be greater than ten so that the heat transfer in the center of the test assembly was nearly one-dimensional. A rigid, thin Inconel plate was used as the septum plate directly exposed to the flame to provide a relatively uniform, known-temperature boundary condition for the test assembly, and to prevent convective heat transfer through the test insulation from the burner. The test sample, flexible alumina paper insulation, was placed between the Inconel plate and a thin titanium witness plate. The overall assembly was further insulated using a combination of rigid and flexible ceramic insulations to minimize heat losses from the periphery of the test assembly. Thermocouples installed on the septum and witness plates and inside the insulation test sample provided temperature measurements at various locations. For the evaluation tests, the Inconel septum plate reached temperatures between 780°C and 850°C for tests with flame exposure durations of 120 sec to 300 sec. The measured temperatures for various tests with similar flame exposure times were repeatable. A one-dimensional numerical heat transfer model of the test assembly was developed. The close agreement between measured and predicted temperatures on the titanium witness plate and inside the insulation test sample indicated that this test may provide a one-dimensional thermal testing capability for evaluation of thermal performance of similar insulations.

Daryabeigi, Kamran↗
NASA NTRS2020

Chemistry of Ionic Silver and Implications for Design of Potable Water Systems

Ionic silver (Ag+) at approximately 400 µg/L is proposed as an ingestible biocide for potable water systems in future human spacecraft. This paper investigates the underlying chemistry of the silver ion at potable concentrations and its interactions with other solutes and surfaces. This chemistry evaluation will elucidate ionic silver behavior in potable water systems and enable design optimization to minimize ionic silver depletion during long duration crewed and uncrewed segments of missions. Ionic silver can be lost from the water phase to the water-solid interface via adsorption as the cation and oxidation-reduction reactions with passivation defects. The adsorption and oxidation-reduction reactions of heritage piping materials used on spacecraft – stainless steel 316L, titanium, Inconel 718, and Teflon flex hoses – are considered. Conceptual models of adsorption isotherms and pH adsorption edges are applied to understand the role of pH and the surface-to-volume ratio of pipes and tanks on the partitioning of ionic silver between the aqueous and the solid phase during aging. The effect of repeated exposure-aging to an Ag+ containing solution of two passivated alloys (316L and Inconel 718) is evaluated to determine if an equilibrium concentration of ionic silver in the potable range is attainable for a given alloy and surface-to-volume ratio. Aging unpassivated and passivated 316L reduced the ionic silver depletion rate relative to first time exposures, but the same beneficial effect was not observed for Inconel 718.

Water↗