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NASA NTRS2008

Cold Start of a Radiator Equipped with Titanium-Water Heat Pipes

Radiator panels utilizing titanium-water heat pipes are being considered for lunar applications. A traditional sandwich structure is envisioned where heat pipes are embedded between two high thermal conductivity face sheets. The heat pipe evaporators are to be thermally connected to the heat source through one or more manifolds containing coolant. Initial radiator operation on the lunar surface would likely follow a cold soak where the water in the heat pipes is purposely frozen. To achieve heat pipe operation, it will be necessary to thaw the heat pipes. One option is to allow the sunlight impinging on the surface at sunrise to achieve this goal. Testing was conducted in a thermal vacuum chamber to simulate the lunar sunrise and additional modeling was conducted to identify steady-state and transient response. It was found that sunlight impinging on the radiator surface at sunrise was insufficient to solely achieve the goal of thawing the water in the heat pipes. However, starting from a frozen condition was accomplished successfully by applying power to the evaporators. Start up in this fashion was demonstrated without evaporator dryout. Concern is raised over thawing thermosyphons, vertical heat pipes operating in a gravity field, with no wick in the condenser section. This paper presents the results of the simulated cold start study and identifies future work to support radiator panels equipped with titanium-water heat pipes.

Jaworske, Donald A.↗

DOE OSTI2022

General Employee Radiological Training: 24 Month Refresher (Course #47968)

GERT is required by the 10 CFR 835, the Federal Regulation on Radiation Protection that we follow here at LANL. It’s the training for non Rad Workers who may enter Radiological Controlled Areas (RCAs) and Radioactive Material Areas (RMAs) in an unescorted manner. If your work assignment requires access to areas posted for higher radiological hazards like Radiological Buffer Areas (RBAs), Radiation Areas, Contamination Areas, and others you are required to have Rad Worker training. Once you complete this training you will be qualified to access RCAs and RMAs at LANL without an escort. However, you are not qualified to operate radiation producing devices, work with radioactive material, or do work where you may receive greater than 100 mrem of exposure in a year.

61 RADIATION PROTECTION AND DOSIMETRY↗

NASA NTRS1974

Flame detector operable in presence of proton radiation

A detector of ultraviolet radiation for operation in a space vehicle which orbits through high intensity radiation areas is described. Two identical ultraviolet sensor tubes are mounted within a shield which limits to acceptable levels the amount of proton radiation reaching the sensor tubes. The shield has an opening which permits ultraviolet radiation to reach one of the sensing tubes. The shield keeps ultraviolet radiation from reaching the other sensor tube, designated the reference tube. The circuitry of the detector subtracts the output of the reference tube from the output of the sensing tube, and any portion of the output of the sensing tube which is due to proton radiation is offset by the output of the reference tube. A delay circuit in the detector prevents false alarms by keeping statistical variations in the proton radiation sensed by the two sensor tubes from developing an output signal.

Walker, D. J.↗

NASA NTRS1973

Matrix operator theory of radiative transfer. II - Scattering from maritime haze.

Matrix operator theory is used to calculate the reflected and transmitted radiance of photons that have interacted with plane-parallel maritime haze layers. The results are presented for three solar zenith angles, three values of the surface albedo, and a range of optical thicknesses from very thin to very thick. The diffuse flux at the lower boundary and the cloud albedo are tabulated. The forward peak and other features in the single-scattered phase function cause the radiance in many cases to be very different from that for Rayleigh scattering. In particular, the variation of the radiance with both the zenith or nadir angle and the azimuthal angle is more marked and the relative limb darkening under very thick layers is greater for haze M than for Rayleigh scattering. The downward diffuse flux at the lower boundary for A = 0 is always greater and the cloud albedo is always less for haze M than for Rayleigh layers.

Kattawar, G. W.↗

NASA NTRS2014

CloudSat-Constrained Cloud Ice Water Path and Cloud Top Height Retrievals from MHS 157 and 183.3 GHz Radiances

Ice water path (IWP) and cloud top height (ht) are two of the key variables in determining cloud radiative and thermodynamical properties in climate models. Large uncertainty remains among IWP measurements from satellite sensors, in large part due to the assumptions made for cloud microphysics in these retrievals. In this study, we develop a fast algorithm to retrieve IWP from the 157, 183.3+/-3 and 190.3 GHz radiances of the Microwave Humidity Sounder (MHS) such that the MHS cloud ice retrieval is consistent with CloudSat IWP measurements. This retrieval is obtained by constraining the empirical forward models between collocated and coincident measurements of CloudSat IWP and MHS cloud-induced radiance depression (Tcir) at these channels. The empirical forward model is represented by a lookup table (LUT) of Tcir-IWP relationships as a function of ht and the frequency channel.With ht simultaneously retrieved, the IWP is found to be more accurate. The useful range of the MHS IWP retrieval is between 0.5 and 10 kg/sq m, and agrees well with CloudSat in terms of the normalized probability density function (PDF). Compared to the empirical model, current operational radiative transfer models (RTMs) still have significant uncertainties in characterizing the observed Tcir-IWP relationships. Therefore, the empirical LUT method developed here remains an effective approach to retrieving ice cloud properties from the MHS-like microwave channels.

cloud top height↗

DOE OSTI2021

A Parameterization of the Cloud Scattering Polarization Signal Derived From GPM Observations for Microwave Fast Radative Transfer Models

Microwave cloud polarized observations have shown the potential to improve precipitation retrievals since they are linked to the orientation and shape of ice habits. Stratiform clouds show larger brightness temperature (TB) polarization differences (PDs), defined as the vertically polarized TB (TBV) minus the horizontally polarized TB (TBH), with ~10 K PD values at 89 GHz due to the presence of horizontally aligned snowflakes, while convective regions show smaller PD signals, as graupel and/or hail in the updraft tend to become randomly oriented. The launch of the global precipitation measurement (GPM) microwave imager (GMI) has extended the availability of microwave polarized observations to higher frequencies (166 GHz) in the tropics and midlatitudes, previously only available up to 89 GHz. This study analyzes one year of GMI observations to explore further the previously reported stable relationship between the PD and the observed TBs at 89 and 166 GHz, respectively. The latitudinal and seasonal variability is analyzed to propose a cloud scattering polarization parameterization of the PD-TB relationship, capable of reconstructing the PD signal from simulated TBs. Given that operational radiative transfer (RT) models do not currently simulate the cloud polarized signals, this is an alternative and simple solution to exploit the large number of cloud polarized observations available. Finally, the atmospheric radiative transfer simulator (ARTS) is coupled with the weather research and forecasting (WRF) model, in order to apply the proposed parameterization to the RT simulated TBs and hence infer the corresponding PD values, which show to reproduce the observed GMI PDs well.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2022

Helium Degassing Filter for Mercury Process Gas Liquid Separator

Testing was conducted to find a suitable filter to help separate helium gas from the Spallation Neutron Source’s mercury process loop. This filter is proposed for installation on the gas-liquid separator (GLS) vent line to prevent a column of liquid mercury from flowing outside of the process loop shielding in the service bay. The filter’s desired properties are to prevent the passage of liquid mercury, provide minimal resistance to helium flow, resist radiation, operate for the lifetime of the target, be replaceable, and have a reliable construction. Testing concluded that the Mott Corporation POU-10-S series of filters provided the best performance available. The filters could stop most liquid mercury passage while allowing helium passage at nominal pressures above the GLS in standard conditions. This result has several implications for the design of the GLS vent system.

Weinmeister, Justin↗

NASA NTRS1973

Matrix operator theory of radiative transfer. I - Rayleigh scattering.

An entirely rigorous method for the solution of the equations for radiative transfer based on the matrix operator theory is reviewed. The advantages of the present method are: (1) all orders of the reflection and transmission matrices are calculated at once; (2) layers of any thickness may be combined, so that a realistic model of the atmosphere can be developed from any arbitrary number of layers, each with different properties and thicknesses; (3) calculations can readily be made for large optical depths and with highly anisotropic phase functions; (4) results are obtained for any desired value of the surface albedo including the value unity and for a large number of polar and azimuthal angles; (5) all fundamental equations can be interpreted immediately in terms of the physical interactions appropriate to the problem; and (6) both upward and downward radiance can be calculated at interior points from relatively simple expressions.

Plass, G. N.↗

NASA NTRS1975

Detection of the isotopes of heavy cosmic ray nuclei

A counter telescope designed to detect and resolve the isotopic composition of cosmic ray nuclei heavier than neon is being prepared. The telescope consists of a rather conventional charge measuring array using two scintillator elements and two solid Cerenkov radiators of differing refractive index. The mass measurement is obtained by combining the velocity information from one or both of the Cerenkov radiators operating near their threshold with residual range measured in a block of nuclear emulsion. Path length corrections and particle location in the emulsions is provided by a spark chamber fired in coincidence with potentially suitable particles. The telescope has a geometry factor of 530 sq cm sr roughly. It should be able to resolve the isotopes of iron over the energy range of 300 to 720 Mev/n and those of neon over 300 to 400 MeV/n. The expected response and characteristics of the telescope are described in detail and the sensitivity to rare isotopes discussed.

Gilman, C. M.↗

NASA NTRS1977

Splines under tension in integral transfer problems

Splines under tension are used to develop an interpolatory representation of integral radiation operators. A quantitative measure of the stability of this representation is derived and approximated in terms of local grid lengths and the tension parameter. Cubic splines (zero tension parameter) are shown to be approximately stable when the ratio of successive grid lengths lies within a specific range. Scaling procedures for determining the tension constant from the structure of the grids and the characteristics of the problem are discussed, and the utility of these procedures is illustrated by application to the formation of resonance lines in two-dimensional media with exponential height variation of opacity.

Jones, H. P.↗

NASA NTRS1984

Natural interference phenomena affecting spaceborne receivers

Earth orbiting microwave receivers which are vulnerable to the interference from natural sources, mainly, the Sun and the Moon, are discussed. The irradiance from the Sun affects microwave receivers in two ways: (1) the infrared component of the irradiance causes nonuniform heating in metal structures and produces distortions that affect electrical performance; and (2) the graybody radiation component of the solar irradiance enters the collecting aperture of the antenna and the feed ports of the calibration circuits. The graybody radiation operates to degrade the signal to noise ratios and vitiate the internal calibration accuracy. The magnitudes of interference from the Sun and the Moon are analyzed and mathematical expressions are derived which serve to quantify the expected interference levels.

Stacey, J. M.↗

NASA NTRS1992

High efficiency thermal to electric energy conversion using selective emitters and spectrally tuned solar cells

Chubb, Donald L.↗

NASA NTRS1992

Evolution of the Space Station Freedom module pattern

A reanalysis of the evolution configuration module pattern for Space Station Freedom is presented. The module pattern is to consist of one habitation module, one airlock, one cupola, two Space Shuttle Orbiter pressurized docking adapters, one assured crew return vehicle, and one pressurized logistics module. Three laboratory modules are also included. A phased plan has been developed on the basis of utilization analysis being performed and derived through actual and projected user mission requirements for the growth of pressurized elements. The evolution requirement impacts to the module pattern are outlined. Application of the growth philosophy and the physical limitations resulted in a number of core element ground rules for module pattern growth. Nodes and modules are to be grown symmetrically in order to optimize poor flight control characteristics and maximize the capability for crew dual egress between elements. Core module pattern elements are not to be grown along Y-Y axis from nodes 1 or 2 due to physical clearance problems with the thermal control system radiators operational envelope.

Gould, Marston↗

NASA NTRS1993

High efficiency direct thermal to electric energy conversion from radioisotope decay using selective emitters and spectrally tuned solar cells

Thermophotovoltaic (TPV) systems are attractive possibilities for direct thermal-to-electric energy conversion, but have typically required the use of black body radiators operating at high temperatures. Recent advances in both the understanding and performance of solid rare-earth oxide selective emitters make possible the use of TPV at temperatures as low as 1200K. Both selective emitter and filter system TPV systems are feasible. However, requirements on the filter system are severe in order to attain high efficiency. A thin-film of a rare-earth oxide is one method for producing an efficient, rugged selective emitter. An efficiency of 0.14 and power density of 9.2 W/KG at 1200K is calculated for a hypothetical thin-film neodymia (Nd2O3) selective emitter TPV system that uses radioisotope decay as the thermal energy source.

Chubb, Donald L.↗

NASA NTRS2004

Robotic Subsurface Analyzer and Sample Handler for Resource Reconnaissance and Preliminary Site Assessment for ISRU Activities at the Lunar Cold Traps

Since the 1960s, claims have been made that water ice deposits should exist in permanently shadowed craters near both lunar poles. Recent interpretations of data from the Lunar Prospector-Neutron Spectrometer (LP- NS) confirm that significant concentrations of hydrogen exist, probably in the form of water ice, in the permanently shadowed polar cold traps. Yet, due to the large spatial resolution (45-60 Ian) of the LP-NS measurements relative to these shadowed craters (approx.5-25 km), these data offer little certainty regarding the precise location, form or distribution of these deposits. Even less is known about how such deposits of water ice might effect lunar regolith physical properties relevant to mining, excavation, water extraction and construction. These uncertainties will need to be addressed in order to validate fundamental lunar In Situ Resource Utilization (ISRU) precepts by 2011. Given the importance of the in situ utilization of water and other resources to the future of space exploration a need arises for the advanced deployment of a robotic and reconfigurable system for physical properties and resource reconnaissance. Based on a collection of high-TRL. designs, the Subsurface Analyzer and Sample Handler (SASH) addresses these needs, particularly determining the location and form of water ice and the physical properties of regolith. SASH would be capable of: (1) subsurface access via drilling, on the order of 3-10 meters into both competent targets (ice, rock) and regolith, (2) down-hole analysis through drill string embedded instrumentation and sensors (Neutron Spectrometer and Microscopic Imager), enabling water ice identification and physical properties measurements; (3) core and unconsolidated sample acquisition from rock and regolith; (4) sample handling and processing, with minimized contamination, sample containerization and delivery to a modular instrument payload. This system would be designed with three mission enabling goals, including: (1) a self-contained, low power, low mass, "black box'' configuration for operations from a lander, various classes of rovers or a surface-based platform with human assistance or robotic anchoring mechanisms; (2) reconfigurable and scalable sample handling for delivery to various types of instrumentation, depending on mission requirements; and (3) the use of advanced automation control and diagnostic techniques that will afford local human deployed, remote teleoperation and fully autonomous intelligent operations. Though a great deal of technology has been advanced toward these objectives, the SASH system faces significant design challenges, including the low gravity environment, various levels of autonomy in operations, radiation exposure, dust contamination, and temperature extremes and deltas. Significant input from the scientific and engineering communities, as well as a significant environmental testing program, will be required to guide the design process.

Gorevan, S. P.↗

NASA NTRS2008

Synchrotron X-Ray Diffraction Studies of Olivine from Comet Wild 2

We have analyzed a collection of the Comet Wild 2 coma grains returned by the NASA Stardust Mission, using micro-area Laue diffraction equipment. The purpose of the diffraction experiment is to permit the structure refinement of olivine including site occupancies. In addition to the intrinsic importance of the olivine structures for revealing the thermal history of Wild 2 materials, we wish to test reports that olivine recovered after hypervelocity capture in silica aerogel has undergone a basic structural change due to capture heating [1]. The diffraction equipment placed at beam line BL- 4B1 of PF, KEK was developed with a micropinhole and an imaging plate (Fuji Co. Ltd.) using the Laue method combined with polychromatic X-ray of synchrotron radiation operated at energy of 2.5 GeV. The incident beam is limited to 1.6 m in diameter by a micropinhole set just upstream of the sample [2, 3]. It is essential to apply a microbeam to obtain diffracted intensities with high signal to noise ratios. This equipment has been successfully applied to various extraterrestrial materials, including meteorites and interplanetary dust particles [4]. The Laue pattern of the sample C2067,1,111,4 (Fig. 1) was successfully taken on an imaging plate after a 120 minute exposure (Fig. 2).

Source record↗

NASA NTRSDate not supplied

Precision in Assembled Discrete Lattice Space Structures for Next-Generation ISAM Applications

Robust autonomous robotic assembly of large-scale space structures has been a long-term and challenging goal to enable higher quality in-space communication and science instrumentation. For optical observatory support structures and antenna structures, the challenge is the strict dimensional precision requirements (generally RMS surface error) driven by the operational radiation wavelength. Early theoretical work in the area linked RMS surface error of a reflector support truss plate to the natural passive dynamic mode frequencies of the structure, as well as to the error distribution in dimensions of constituent structural elements. Prior robotic truss assembly demonstrations focused on designing ultra-high precision structural elements, joints, and robotic actuators. Recently, an alternative space structure assembly strategy based on a programmable matter approach (NASA ARMADAS) was demonstrated. This approach uses lattice building blocks (voxels) that are reversibly, mechanically joined into a bulk lattice structure by robots that locomote in and on the structure itself. Such a system can achieve high-level autonomy with low computation, robustly assemble utilizing inexpensive and imprecise robots, and efficiently build structures several orders of magnitude larger than the assembly robots. However, for instrumentation support structure applications, the resulting precision of these building block-based lattice structures is not well studied. Since they are demonstrated with many more assembly units than prior art trusses, it is unclear whether the same precision design approaches apply. In this work, we study in simulation the effects of voxel geometry, error in distribution, assembly resolution (module size), and assembly geometry on the error of both beam and plate lattice structures. While average RMS error of a plate increases with plate size, increasing plate thickness quickly collapses RMS error towards a limit that is on the order of the error of the constituent parts. We validate our models against previously published precision measurements of built systems. Results from this study will guide manufacturing precision requirements, as well as designs, for future robotically assembled structural applications and establish feasibility for different applications.

Christine E Gregg↗

NASA NTRSDate not supplied

A Multi-Year Effort to Forward the Validation of Solar Energetic Particle Prediction Models

To enable a consistent and quantitative understanding of solar energetic particle (SEP) model performance, a generalized, automated validation infrastructure, called SPHINX, is being developed by the NASA Space Radiation Analysis Group (SRAG) in close collaboration with the NASA Community Coordinated Modeling Center (CCMC), NASA Moon to Mars Space Weather Analysis Office (M2M), NOAA Space Weather Prediction Center (SWPC), and the Royal Belgian Institute for Space Aeronomy (BIRA-IASB). SPHINX is being developed to evaluate the SEP Scoreboards (https://ccmc.gsfc.nasa.gov/scoreboards/sep/), which are being used by SRAG to support space radiation operations for Mission Control. SPHINX is also being developed through a series of community challenges, which have defined a list of challenge events and a prescribed set of rules of participation. The participation of the research community has enabled the generalization of the infrastructure to validate all the types of outputs being produced by SEP models and fully exercised the framework. The most recent challenge includes 30 SEP events and 33 non-event (quiet) periods and was supported by two dedicated SEPVAL working meetings, one in the US and one in Europe (https://ccmc.gsfc.nasa.gov/community-workshops/ccmc-sepval-2023/). Here, we describe SPHINX and its interactive user interface, SPHINX-VIVID, which will eventually be made available for public use. We present selected results, outcomes, and lessons learned from the SEPVAL working meetings and validation results of the SEP Scoreboards from 2019 to present. These efforts aim to define a set of community standards for SEP model validation and describe the current state-of-the-art of SEP model performance.

Kathryn Whitman↗