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At least 217 records · Page 12

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NASA NTRS2006

The Validation of Vapor Phase Hydrogen Peroxide Microbial Reduction for Planetary Protection and a Proposed Vacuum Process Specification

The Jet Propulsion Laboratory, in conjunction with the NASA Planetary Protection Officer, has selected the vapor phase hydrogen peroxide sterilization process for continued development as a NASA approved sterilization technique for spacecraft subsystems and systems. The goal is to include this technique, with an appropriate specification, in NPR 8020.12C as a low temperature complementary technique to the dry heat sterilization process.To meet microbial reduction requirements for all Mars in-situ life detection and sample return missions, various planetary spacecraft subsystems will have to be exposed to a qualified sterilization process. This process could be the elevated temperature dry heat sterilization process (~115 C for 40 hours) which was used to sterilize the Viking lander spacecraft. However, with utilization of such elements as highly sophisticated electronics and sensors in modern spacecraft, this process presents significant materials challenges and is thus an undesirable bioburden reduction method to design engineers. The objective of this work is to introduce vapor hydrogen peroxide (VHP) as an alternative to dry heat microbial reduction to meet planetary protection requirements.The VHP process is widely used by the medical industry to sterilize surgical instruments and biomedical devices, but high doses of VHP may degrade the performance of flight hardware, or compromise material properties. Our goal for this study was to determine the minimum VHP process conditions to achieve microbial reduction levels acceptable for planetary protection.

planetary protection↗

NASA NTRS2019

Redeployable Sensor Probe for In-Situ Lunar Resource Mapping from Small Landers

The use of in-situ resources in lunar regolith for production of propellant, life support, and construction (e.g. polar water ice, hydrogen, helium-3, and regolith minerals) will enable sustainable robotic and human space exploration and pave the way for commercialization of lunar exploration. Currently, the search for and characterization of resources on the Moon uses orbital datasets and local geological and geophysical surveys to map and characterize potential deposits. To develop efficient ISRU systems, it is essential to find, characterize, and map lunar resources in-situ, at local scales, using deployable, analytical payloads. We have developed a 3 kg, TRL4 scientific payload, MoonSHOT (Moon Subsurface Hydrogen Optical Tool), to characterize and map lunar resources from a small lander or rover.

Sobron, P.↗

NASA NTRS1979

Solid polymer electrolyte water electrolysis preprototype subsystem

Hardware and controls developed for an electrolysis demonstration unit for use with the life sciences payload program and in NASA's regenerative life support evaluation program are described. Components discussed include: the electrolysis module; power conditioner; phase separator-pump and hydrogen differential regulator; pressure regulation of O2, He, and N2; air-cooled heat exchanger; water accumulator; fluid flow sight gage assembly; catalytic O2/H2 sensor; gas flow sensors; low voltage power supply; 100 Amp DC contactor assembly; and the water purifier design.

Source record↗

NASA NTRS1992

Propellant production and useful materials: Hardware data from components and the systems

Research activities at the University of Arizona/NASA Space Engineering Research Center are described; the primary emphasis is on hardware development and operation. The research activities are all aimed toward introducing significant cost reductions through the utilization of resources locally available at extraterrestrial sites. The four logical aspects include lunar, Martian, support, and common technologies. These are described in turn. The hardware realizations are based upon sound scientific principles which are used to screen a host of interesting and novel concepts. Small scale feasibility studies are used as the screen to allow only the most promising concepts to proceed. Specific examples include: kg/day-class oxygen plant that uses CO2 as the feed stock, spent stream utilization to produce methane and 'higher' compounds (using hydrogen from a water electrolysis plant), separation of CO from the CO2, reduction of any iron bearing silicate (lunar soils), production of structural components, smart sensors and autonomous controls, and quantitative computer simulation of extraterrestrial plants. The most important feature of all this research continues to be the training of high-quality students for our future in space.

Ramohalli, Kumar↗

NASA NTRS1999

Advances in Thin Film Thermocouple Durability Under High Temperature and Pressure Testing Conditions

Thin film thermocouples for measuring material surface temperature have been previously demonstrated on several material systems and in various hostile test environments. A well-developed thin film fabrication procedure utilizing shadow masking for patterning the sensors elements had produced thin films with sufficient durability for applications in high temperature and pressure environments that exist in air-breathing and hydrogen-fueled burner rig and engine test facilities. However, while shadow masking had been a reliable method for specimens with flat and gently curved surfaces, it had not been consistently reliable for use on test components with sharp contours. This work reports on the feasibility of utilizing photolithography processing for patterning thin film thermocouples. Because this patterning process required changes in the thin film deposition process from that developed for shadow masking, the effect of these changes on thin film adherence during burner rig testing was evaluated. In addition to the results of changing the patterning method, the effects on thin film adherence of other processes used in the thin film fabrication procedure is also presented.

Martin, Lisa C.↗

NASA NTRS2007

CFD Modeling of Helium Pressurant Effects on Cryogenic Tank Pressure Rise Rates in Normal Gravity

A recently developed computational fluid dynamics modeling capability for cryogenic tanks is used to simulate both self-pressurization from external heating and also depressurization from thermodynamic vent operation. Axisymmetric models using a modified version of the commercially available FLOW-3D software are used to simulate actual physical tests. The models assume an incompressible liquid phase with density that is a function of temperature only. A fully compressible formulation is used for the ullage gas mixture that contains both condensable vapor and a noncondensable gas component. The tests, conducted at the NASA Marshall Space Flight Center, include both liquid hydrogen and nitrogen in tanks with ullage gas mixtures of each liquid's vapor and helium. Pressure and temperature predictions from the model are compared to sensor measurements from the tests and a good agreement is achieved. This further establishes the accuracy of the developed FLOW-3D based modeling approach for cryogenic systems.

Grayson, Gary↗

NASA NTRS1971

Study to develop improved methods to detect leakage in fluid systems, phase 2

An ultrasonic contact sensor engineering prototype leak detection system was developed and its capabilities under cryogenic operations demonstrated. The results from tests indicate that the transducer performed well on liquid hydrogen plumbing, that flow and valve actuation could be monitored, and that the phase change from gaseous to liquid hydrogen could be detected by the externally mounted transducers. Tests also demonstrate the ability of the system to detect internal leaks past valve seats and to function as a flow meter. Such a system demonstrates that it is not necessary to break into welded systems to locate internal leaks.

Janus, J. C.↗

NASA NTRS2003

Capacitive Sensors for Measuring Masses of Cryogenic Fluids

An effort is under way to develop capacitive sensors for measuring the masses of cryogenic fluids in tanks. These sensors are intended to function in both microgravitational and normal gravitational settings, and should not be confused with level sensors, including capacitive ones. A sensor of this type is conceptually simple in the sense that (1) it includes only one capacitor and (2) if properly designed, its single capacitance reading should be readily convertible to a close approximation of the mass of the cryogenic fluid in the tank. Consider a pair of electrically insulated electrodes used as a simple capacitive sensor. In general, the capacitance is proportional to the permittivity of the dielectric medium (in this case, a cryogenic fluid) between the electrodes. The success of design and operation of a sensor of the present type depends on the accuracy of the assumption that to a close approximation, the permittivity of the cryogenic fluid varies linearly with the density of the fluid. Data on liquid nitrogen, liquid oxygen, and liquid hydrogen, reported by the National Institute of Standards and Technology, indicate that the permittivities and densities of these fluids are, indeed, linearly related to within a few tenths of a percent over the pressure and temperature regions of interest. Hence, ignoring geometric effects for the moment, the capacitance between two electrodes immersed in the fluid should vary linearly with the density, and, hence, with the mass of the fluid. Of course, it is necessary to take account of the tank geometry. Because most cryogenic tanks do not have uniform cross sections, the readings of level sensors, including capacitive ones, are not linearly correlated with the masses of fluids in the tanks. In a sensor of the present type, the capacitor electrodes are shaped so that at a given height, the capacitance per unit height is approximately proportional to the cross-sectional area of the tank in the horizontal plane at that height (see figure).

Nurge, Mark↗

NASA NTRS2015

Evidence for the Sequestration of Hydrogen-Bearing Volatiles Towards the Moons Southern Pole-Facing Slopes

The Lunar Exploration Neutron Detector (LEND) onboard the Lunar Reconnaissance Orbiter (LRO) detects a widespread suppression of the epithermal neutron leakage flux that is coincident with the pole-facing slopes (PFS) of the Moon's southern hemisphere. Suppression of the epithermal neutron flux is consistent with an interpretation of enhanced concentrations of hydrogen-bearing volatiles within the upper meter of the regolith. Localized flux suppression in PFS suggests that the reduced solar irradiation and lowered temperature on PFS constrains volatility to a greater extent than in surrounding regions. Epithermal neutron flux mapped with LEND's Collimated Sensor for Epithermal Neutrons (CSETN) was analyzed as a function of slope geomorphology derived from the Lunar Orbiting Laser Altimeter (LOLA) and the results compared to co-registered maps of diurnally averaged temperature from the Diviner Lunar Radiometer Experiment and an averaged illumination map derived from LOLA. The suppression in the average south polar epithermal neutron flux on equator-facing slopes (EFS) and PFS (85-90 deg S) is 3.3 +/- 0.04% and 4.3 +/- 0.05% respectively (one-sigma-uncertainties), relative to the average count-rate in the latitude band 45-90 deg S. The discrepancy of 1.0 +/- 0.06% between EFS and PFS neutron flux corresponds to an average of approximately 23 parts-per-million-by-weight (ppmw) more hydrogen on PFS than on EFS. Results show that the detection of hydrogen concentrations on PFS is dependent on their spatial scale. Epithermal flux suppression on large scale PFS was found to be enhanced to 5.2 +/- 0.13%, a discrepancy of approximately 45 ppmw hydrogen relative to equivalent EFS. Enhanced poleward hydration of PFS begins between 50 deg S and 60 deg S latitude. Polar regolith temperature contrasts do not explain the suppression of epithermal neutrons on pole-facing slopes. The Supplemental on-line materials include supporting results derived from the uncollimated Lunar Prospector Neutron Spectrometer and the LEND Sensor for Epithermal Neutrons.

Ices↗

NASA NTRS1978

Biological water quality monitoring using chemiluminescent and bioluminescent techniques

Automated chemiluminescence and bioluminescence sensors were developed for the continuous monitoring of microbial levels in water supplies. The optimal chemical procedures were determined for the chemiluminescence system to achieve maximum sensitivity. By using hydrogen peroxide, reaction rate differentiation, ethylene diamine tetraacetic acid (EDTA), and carbon monoxide pretreatments, factors which cause interference were eliminated and specificity of the reaction for living and dead bacteria was greatly increased. By employing existing technology with some modifications, a sensitive and specific bioluminescent system was developed.

Thomas, R. R.↗

NASA NTRS1997

Potential New Sensor for Use With Conventional Gas Carburizing

Diagnostics developed for in-situ monitoring of rocket combustion environments have been adapted for use in heat treating furnaces. Simultaneous, in-situ monitoring of the carbon monoxide, carbon dioxide, methane, water, nitrogen and hydrogen concentrations in the endothermic gas of a heat treating furnace has been demonstrated under a Space Act Agreement between NASA Lewis, the Heat Treating Network, and Akron Steel Treating Company. Equipment installed at the Akron Steel Treating Company showed the feasibility of the method. Clear and well-defined spectra of carbon monoxide, nitrogen and hydrogen were obtained by means of an optical probe mounted on the endothermic gas line of a gas generator inside the plant, with the data reduction hardware located in the basement laboratory. Signals to and from the probe were transmitted via optical fibers.

deGroot, W. A.↗

NASA NTRS2003

Molecular modeling of polymer composite-analyte interactions in electronic nose sensors

We report a molecular modeling study to investigate the polymer-carbon black (CB) composite-analyte interactions in resistive sensors. These sensors comprise the JPL electronic nose (ENose) sensing array developed for monitoring breathing air in human habitats. The polymer in the composite is modeled based on its stereoisomerism and sequence isomerism, while the CB is modeled as uncharged naphthalene rings with no hydrogens. The Dreiding 2.21 force field is used for the polymer, solvent molecules and graphite parameters are assigned to the carbon black atoms. A combination of molecular mechanics (MM) and molecular dynamics (NPT-MD and NVT-MD) techniques are used to obtain the equilibrium composite structure by inserting naphthalene rings in the polymer matrix. Polymers considered for this work include poly(4-vinylphenol), polyethylene oxide, and ethyl cellulose. Analytes studied are representative of both inorganic and organic compounds. The results are analyzed for the composite microstructure by calculating the radial distribution profiles as well as for the sensor response by predicting the interaction energies of the analytes with the composites. c2003 Elsevier Science B.V. All rights reserved.

NASA Center JPL↗

NASA NTRS2002

Molecular modeling of polymer composite interactions with analytes in electronic nose sensors for environmental monitoring in International Space Station

We report a molecular modeling study to investigate the polymer-carbon black (CB) composite-analyte interactions in resistive sensors. These sensors comprise the JPL Electronic Nose (ENose) sensing array developed for monitoring breathing air in human habitats. The polymer in the composite is modeled based on its stereisomerism and sequence isomerism, while the CB is modeled as uncharged naphthalene rings (with no hydrogens). The Dreiding 2.21 force field is used for the polymer and solvent molecules and graphite parameters are assigned to the carbon black atoms. A combination of molecular mechanics (MM) and molecular dynamics (NPT-MD and NVT-MD) techniques are used to obtain the equilibrium composite structure by inserting naphthalene rings in the polymer matrix. Polymers considered for this work include poly(4- vinylphenol), polyethylene oxide, and ethyl cellulose. Analytes studied are representative of both inorganic (ammonia) and organic (methanol, toluene, hydrazine) compounds. The results are analyzed for the composite microstructure by calculating the radial distribution profiles as well as for the sensor response by predicting the interaction energies of the analytes with the composites.

electronic noise environmental monitoring polymer ↗

NASA NTRS1981

Composition of nonthermal ions in the Jovian magnetosphere

Observations are presented from Voyager 1 and 2 of nonthermal ions from H through Fe in the Jovian magnetosphere using the low-energy particle telescope (LEPT), one of the two sensors of the low-energy charged particle (LECP) experiment. At approximately 1 MeV/nucleon, the principal constituents of the ion population were H, He, C, O, Na, S, and the hydrogen molecules H2 and H3. In relation to He, the abundance of H and H3 at equal energy/nucleon was highest in the outer magnetosphere, the abundance of O, Na, and S was highest in the inner magnetosphere, and the abundance of C was constant throughout the magnetosphere.

Hamilton, D. C.↗

NASA NTRS1993

Noncontact Measurement Of Shaft Speed, Torque, And Power

Noncontact fiber-optic sensor and associated electronic equipment measure twist and speed of rotation of shaft. Measurements determine torque and power. Response of sensor remains linear even at cryogenic temperatures. Reflective strips on rotating shaft reflect two series of light pulses back into optical system. Bidirectional coupler in each of two optical fiber paths separates reflected light from incident light, sending it to photodiode for output to analog-to-digital converter and computer. Sensor requires no slip rings or telemetry to transfer signals from shaft. Well suited for providing data on performances of turbopumps for such cryogenic fluids as liquid oxygen and liquid hydrogen.

Madzsar, George C.↗

NASA NTRS2008

The Summer of Hydrogen

Ground crew veterans at Kennedy Space Center still talk about what they call "the summer of hydrogen"-the long, frustrating months in 1990 when the shuttle fleet was grounded by an elusive hydrogen leak that foiled our efforts to fill the orbiter's external fuel tank. Columbia (STS-35) was on Launch Pad A for a scheduled May 30 launch when we discovered the hydrogen leak during - tanking. The external fuel tank is loaded through the orbiter. Liquid hydrogen flows through a 17-inch umbilical between the orbiter and the tank. During fueling, we purge the aft fuselage with gaseous nitrogen to reduce the risk of fire, and we have a leak-detection system in the mobile launch platform, which samples (via tygon tubing) the atmosphere in and around the vehicle, drawing it down to a mass spectrometer that analyzes its composition. When we progressed to the stage of tanking where liquid hydrogen flows through the vehicle, the concentration of hydrogen approached four percent-the limit above which it would be dangerously flammable. We had a leak. We did everything we could think of to find it, and the contractor who supplied the flight hardware was there every day, working alongside us. We did tanking tests, which involved instrumenting the suspected leak sources, and cryo-loaded the external tank to try to isolate precisely where the leak originated. We switched out umbilicals; we replaced the seals between the umbilical and the orbiter. We inspected the seals microscopically and found no flaws. We replaced the recirculation pumps, and we found and replaced a damaged teflon seal in a main propulsion system detent cover, which holds the prevalve-the main valve supplying hydrogen to Space Shuttle Main Engine 3 -in the open position. The seal passed leak tests at ambient temperature but leaked when cryogenic temperatures were applied. We added new leak sensors-up to twenty at a time and tried to be methodical in our placements to narrow down the possible sources of the problem. We even switched orbiters, sending Columbia back to the Vehicle Assembly Building and bringing out Atlantis, scheduled to fly as STS-38. Two shuttles on their mobile launchers passing in the night was a majestic sight, but not one you want to see if you're trying to get an orbiter launched. None of this told us where the leak was, or if we were dealing with more than one leak source.

Weber, Philip↗

NASA NTRS2015

Physics Simulation Software for Autonomous Propellant Loading and Gas House Autonomous System Monitoring

1. Kennedy Space Center (KSC) is developing a mobile launching system with autonomous propellant loading capabilities for liquid-fueled rockets. An autonomous system will be responsible for monitoring and controlling the storage, loading and transferring of cryogenic propellants. The Physics Simulation Software will reproduce the sensor data seen during the delivery of cryogenic fluids including valve positions, pressures, temperatures and flow rates. The simulator will provide insight into the functionality of the propellant systems and demonstrate the effects of potential faults. This will provide verification of the communications protocols and the autonomous system control. 2. The High Pressure Gas Facility (HPGF) stores and distributes hydrogen, nitrogen, helium and high pressure air. The hydrogen and nitrogen are stored in cryogenic liquid state. The cryogenic fluids pose several hazards to operators and the storage and transfer equipment. Constant monitoring of pressures, temperatures and flow rates are required in order to maintain the safety of personnel and equipment during the handling and storage of these commodities. The Gas House Autonomous System Monitoring software will be responsible for constantly observing and recording sensor data, identifying and predicting faults and relaying hazard and operational information to the operators.

Regalado Reyes, Bjorn Constant↗

NASA NTRS1994

Dynamic Simulation of a Periodic 10 K Sorption Cryocooler

A transient thermal simulation model has been developed to simulate the dynamic performance of a multiple-stage 10 K sorption cryocooler for spacecraft sensor cooling applications that require periodic quick-cooldown (under 2 minutes) , negligible vibration, low power consumption, and long life (5 to 10 years). The model was specifically designed to represent the Brilliant Eyes Ten-Kelvin Sorption Cryocooler Experiment (BETSCE), but it can be adapted to represent other sorption cryocooler systems as well. The model simulates the heat transfer, mass transfer, and thermodynamic processes in the cryostat and the sorbent beds for the entire refrigeration cycle, and includes the transient effects of variable hydrogen supply pressures due to expansion and overflow of hydrogen during the cooldown operation. The paper describes model limitations and simplifying assumptions, with estimates of errors induced by them, and presents comparisons of performance predictions with ground experiments. An important benefit of the model is its ability to predict performance sensitivities to variations of key design and operational parameters. The insights thus obtained are expected to lead to higher efficiencies and lower weights for future designs.

cryocooler design performance sorption simulation ↗