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NASA NTRSDate not supplied

Advancing xEMU Lunar Dust Mitigation Devices

Fine, electrically charged, glass like dust particles caused significant damage to the Apollo EMU9 during lunar EVAs, identified as one of the greatest challenges to future exploration. Passive Lunar Dust Mitigation Devices (LDMD) were developed, within a SBIR Phase II, to prohibit this dust from interrupting venting space suit component operation. A Computational Fluid-Dynamics and Discrete Element Method (CFD-DEM) Simulation Tool was developed at the University of Colorado, Boulder to predict venting gas flow ability to self-clean adhered dust particles from LDMD surfaces. Lunar dust properties (i.e., adhesion and cohesion strengths) required to complete Simulation Tool analysis are relatively unknown due to considerable differences between the Earth and the Moon (i.e., gravity, humidity) and due to an absence of dust particles in their native state. Analytically determining gas flow velocity, density and direction within the fluid Boundary Layer, microns from LDMD surfaces presented a second challenge. Dusty Plasma Chamber testing is being performed at Auburn University, Auburn to observe electrostatically charged dust behavior as it adheres to LDMD prototypes and specific geometry and is then blown away by metered gas flow. Test articles were developed to offer insight into the impact of different flow geometries, surface roughness and dust removal within the gas Boundary-Layer. Observed dust behavior is currently being developed to support the CFD-DEM analysis. Many Simulation Tool analytical cases have been processed to support the intention of completing sensitivity studies to assess how different dust adherence values and Boundary Layer fluid properties impact LDMD self-cleaning effectivity.

Thomas J Stapleton↗
NASA NTRS2014

Facial Soft Tissue Measurement in Microgravity-induces Fluid Shifts

Fluid shifts are a well‐known phenomenon in microgravity, and one result is facial edema. Objective measurement of tissue thickness in a standardized location could provide a correlate with the severity of the fluid shift. Previous studies of forehead tissue thickness (TTf) suggest that when exposed to environments that cause fluid shifts, including hypergravity, head‐down tilt, and high‐altitude/lowpressure, TTf changes in a consistent and measurable fashion. However, the technique in past studies is not well described or standardized. The International Space Station (ISS) houses an ultrasound (US) system capable of accurate sub‐millimeter measurements of TTf. We undertook to measure TTf during long‐duration space flight using a new accurate, repeatable and transferable technique. Methods: In‐flight and post‐flight B‐mode ultrasound images of a single astronaut's facial soft tissues were obtained using a Vivid‐q US system with a 12L‐RS high‐frequency linear array probe (General Electric, USA). Strictly mid‐sagittal images were obtained involving the lower frontal bone, the nasofrontal angle, and the osseo‐cartilaginous junction below. Single images were chosen for comparison that contained identical views of the bony landmarks and identical acoustical interface between the probe and skin. Using Gingko CADx DICOM viewing software, soft tissue thickness was measured at a right angle to the most prominent point of the inferior frontal bone to the epidermis. Four independent thickness measurements were made. Conclusions: Forehead tissue thickness measurement by ultrasound in microgravity is feasible, and our data suggest a decrease in tissue thickness upon return from microgravity environment, which is likely related to the cessation of fluid shifts. Further study is warranted to standardize the technique with regard to the individual variability of the local anatomy in this area.

Marshburn, Thomas↗
NASA NTRS1998

MEMS Applications in Aerodynamic Measurement Technology

Microelectromechanical systems (MEMS) embodies the integration of sensors, actuators, and electronics on a single substrate using integrated circuit fabrication techniques and compatible bulk and surface micromachining processes. Silicon and its derivatives form the material base for the MEMS technology. MEMS devices, including microsensors and microactuators, are attractive because they can be made small (characteristic dimension about 100 microns), be produced in large numbers with uniform performance, include electronics for high performance and sophisticated functionality, and be inexpensive. For aerodynamic measurements, it is preferred that sensors be small so as to approximate measurement at a point, and in fact, MEMS pressure sensors, wall shear-stress sensors, heat flux sensors and micromachined hot wires are nearing application. For the envisioned application to wind tunnel models, MEMS sensors can be placed on the surface or in very shallow grooves. MEMS devices have often been fabricated on stiff, flat silicon substrates, about 0.5 mm thick, and therefore were not easily mounted on curved surfaces. However, flexible substrates are now available and heat-flux sensor arrays have been wrapped around a curved turbine blade. Electrical leads can also be built into the flexible substrate. Thus MEMS instrumented wind tunnel models do not require deep spanwise grooves for tubes and leads that compromise the strength of conventionally instrumented models. With MEMS, even the electrical leads can potentially be eliminated if telemetry of the signals to an appropriate receiver can be implemented. While semiconductor silicon is well known for its electronic properties, it is also an excellent mechanical material for MEMS applications. However, silicon electronics are limited to operations below about 200 C, and silicon's mechanical properties start to diminish above 400 C. In recent years, silicon carbide (SiC) has emerged as the leading material candidate for applications in high temperature environments and can be used for high-temperature MEMS applications. With SiC, diodes and more complex electronics have been shown to operate to about 600 C, while the mechanical properties of SiC are maintained to much higher temperatures. Even when MEMS devices show benefits in the laboratory, there are many packaging challenges for any aeronautics application. Incorporating MEMS into these applications requires new approaches to packaging that goes beyond traditional integrated circuit (IC) packaging technologies. MEMS must interact mechanically, as well as electrically with their environment, making most traditional chip packaging and mounting techniques inadequate. Wind tunnels operate over wide temperature ranges in an environment that is far from being a 'clean-room.' In flight, aircraft are exposed to natural elements (e.g. rain, sun, ice, insects and dirt) and operational interferences(e.g. cleaning and deicing fluids, and maintenance crews). In propulsion systems applications, MEMS devices will have to operate in environments containing gases with very high temperatures, abrasive particles and combustion products. Hence deployment and packaging that maintains the integrity of the MEMS system is crucial. This paper presents an overview of MEMS fabrication and materials, descriptions of available sensors with more details on those being developed in our laboratories, and a discussion of sensor deployment options for wind tunnel and flight applications.

Reshotko, E.↗
NASA NTRS2008

SansEC: A New Dimension to Sensing Electrical Sensors with No Electrical Connections

This DVD contains an introduction to SansEC, a new electrical sensor technology without electrical connections. This new class of sensors represents a stand-alone 2-dimensional geometric pattern of electrically open circuits without electrical connections. The sensor is powered with an external, harmonic magnetic field and as the property being sensed changes, responds to frequency, amplitude or bandwidth changes. This response is interrogated using an external antenna, a single electrical component having no electrical connections. The sensor can be encased in any nonconductive material to provide protection from its environment. If the container is nonconductive, the sensor can be placed external to the container without contacting it, making installation very simple. An encased sensor can also be placed inside a container for measuring the level of any fluid or material, including acids. Any readout device can be used with the sensor, including standard or digital gauges. SansEC sensors can be used to measure real-time fluid slosh to determine if a fuel tank's internal structural isogrid can be used to replace some of the baffles surface, thus reducing the overall baffle weight and giving a better understanding of the effect that isogrids have on fluid motion. Any SansEC sensor can also be used for damage or tamper detection. When damaged, torn or tampered with, the measured response shift in frequency is commensurate to the detected damage, with the response frequency increasing with rising damage. The unique sensor design allows it to function even if damaged, because unlike other circuits, there is no single point on the sensor that, if damaged, renders it non-functional. The broad metallic coverage of the array allows the array to be one of many thermal insulation layers. Two such arrays were tested to understand the effects of high velocity damage. Each test article was targeted with metal projectiles emulating micrometeorite or orbital debris impact. Even with the damage that the sensors received every sensor was still functional with the new response baseline, and remained capable of detecting even more damage.

Source record↗
NASA NTRS2010

NASA Tech Briefs, November 2010

Topics covered include: Portable Handheld Optical Window Inspection Device; Salience Assignment for Multiple-Instance Data and Its Application to Crop Yield Prediction; Speech Acquisition and Automatic Speech Recognition for Integrated Spacesuit Audio Systems ; Predicting Long-Range Traversability from Short-Range Stereo-Derived Geometry; Browser-Based Application for Telemetry Monitoring of Robotic Assets; Miniature Low-Noise G-Band I-Q Receiver; Methods of Using a Magnetic Field Response Sensor Within Closed, Electrically Conductive Containers; Differential Resonant Ring YIG Tuned Oscillator; Microfabricated Segmented-Involute-Foil Regenerator for Stirling Engines; Reducing Seal Adhesion in Low Impact Docking Systems; Optimal Flow Control Design; Corrosion-Resistant Container for Molten-Material Processing; Reusable Hot-Wire Cable Cutter; Deployment of a Curved Truss; High-Volume Airborne Fluids Handling Technologies to Fight Wildfires; Modeling of Alkane Oxidation Using Constituents and Species; Fabrication of Lanthanum Telluride 14-1-11 Zintl High-Temperature Thermoelectric Couple; A Computer Model for Analyzing Volatile Removal Assembly; Analysis of Nozzle Jet Plume Effects on Sonic Boom Signature; Optical Sidebands Multiplier; Single Spatial-Mode Room-Temperature-Operated 3.0 to 3.4 micrometer Diode Lasers; Self-Nulling Beam Combiner Using No External Phase Inverter; Portable Dew Point Mass Spectrometry System for Real-Time Gas and Moisture Analysis; Maximum Likelihood Time-of-Arrival Estimation of Optical Pulses via Photon-Counting Photodetectors; Handheld White Light Interferometer for Measuring Defect Depth in Windows; Decomposition Algorithm for Global Reachability on a Time-Varying Graph; Autonomous GN and C for Spacecraft Exploration of Comets and Asteroids; Efficient Web Services Policy Combination; Using CTX Image Features to Predict HiRISE-Equivalent Rock Density; Isolation of the Paenibacillus phoenicis, a Spore-Forming Bacterium; Monolithically Integrated, Mechanically Resilient Carbon-Based Probes for Scanning Probe Microscopy; Cell Radiation Experiment System; Process to Produce Iron Nanoparticle Lunar Dust Simulant Composite; Inversion Method for Early Detection of ARES-1 Case Breach Failure; Use of ILTV Control Laws for LaNCETS Flight Research;and Evaluating Descent and Ascent Trajectories Near Non-Spherical Bodies.

Source record↗
NASA NTRS2014

On-Command Force and Torque Impeding Devices (OC-FTID) Using ERF

Various machines have been developed to address the need for countermeasures of bone and muscle deterioration when humans operate over extended time in space. Even though these machines are in use, each of them has many limitations that need to be addressed in an effort to prepare for human missions to distant bodies in the solar system. An exercise exoskeleton was conceived that performs on-demand resistivity by inducing force and torque impedance via ElectroRheological Fluid (ERF). The resistive elements consist of pistons that are moving inside ERF-filled cylinders or a donut-shaped cavity, and the fluid flows through the piston when the piston is moved. Tests of the operation of ERF against load showed the feasibility of this approach. ERF properties of high yield stress, low current density, and fast response (less than one millisecond) offer essential characteristics for the construction of the exoskeleton. ERFs can apply very high electrically controlled resistive forces or torque while their size (weight and geometric parameters) can be very small. Their long life and ability to function in a wide temperature range (from -40 to 200 C) allows for their use in extreme environments. ERFs are also nonabrasive, non-toxic, and nonpolluting (meet health and safety regulations). The technology is applicable as a compact exercise machine for astronauts' countermeasure of microgravity, an exercise machine for sport, or as a device for rehabilitation of patients with limb issues.

Bar-Cohen, Yoseph↗
NASA NTRS2010

Design and Preliminary Thermal Performance of the Mars Science Laboratory Rover Heat Exchangers

The challenging range of proposed landing sites for the Mars Science Laboratory Rover requires a rover thermal management system that is capable of keeping temperatures controlled across a wide variety of environmental conditions. On the Martian surface where temperatures can be as cold as -123 degrees Centigrade and as warm as 38 degrees Centigrade, the Rover relies upon a Mechanically Pumped Fluid Loop (MPFL) and external radiators to maintain the temperature of sensitive electronics and science instruments within a -40 degrees Centigrade to 50 degrees Centigrade range. The MPFL also manages significant waste heat generated from the Rover power source, known as the Multi Mission Radioisotope Thermoelectric Generator (MMRTG). The MMRTG produces 110 Watts of electrical power while generating waste heat equivalent to approximately 2000 Watts. Two similar Heat Exchanger (HX) assemblies were designed to both acquire the heat from the MMRTG and radiate waste heat from the onboard electronics to the surrounding Martian environment. Heat acquisition is accomplished on the interior surface of each HX while heat rejection is accomplished on the exterior surface of each HX. Since these two surfaces need to be at very different temperatures in order for the MPFL to perform efficiently, they need to be thermally isolated from one another. The HXs were therefore designed for high in-plane thermal conductivity and extremely low through-thickness thermal conductivity by using aerogel as an insulator inside composite honeycomb sandwich panels. A complex assembly of hand welded and uniquely bent aluminum tubes are bonded onto the HX panels and were specifically designed to be easily mated and demated to the rest of the Rover Heat Recovery and Rejection System (RHRS) in order to ease the integration effort. During the cruise phase to Mars, the HX assemblies serve the additional function of transferring heat from the Rover MPFL to the separate Cruise Stage MPFL so that heat generated deep inside the Rover can be dissipated via the Cruise Stage radiators. Significant fabrication challenges had to be overcome in order to make the HX design a reality. The cruise phase thermal performance of the Rover HXs was verified in the cruise phase system level thermal vacuum test that was performed at JPL in January of 2009. The Rover HXs were modeled in I-DEAS TMG and predictions are compared to actual data from the test.

Heat Rejection System↗
DOE OSTI2021

Electric-Drive Vehicle Power Electronics Thermal Management: Current Status, Challenges, and Future Directions

Effective thermal management of traction-drive power electronics is critical to the advancement of electric-drive vehicles and is necessary for increasing power density and improving reliability. Replacing traditional silicon devices with more efficient, higher temperature, higher voltage, and higher frequency wide-bandgap (WBG) devices will enable increased power density but will result in higher device heat fluxes. Compact packaging of high-temperature WBG devices near low-temperature-rated components creates thermal management challenges that need to be addressed for future power-dense systems. This paper summarizes the thermal performance of on-road automotive power electronics thermal management systems and provides thermal performance and pumping-power metrics for select vehicles. Thermal analyses reveal that the package/conduction resistance dominates the total thermal resistance (for existing automotive systems). We model advanced packaging concepts and compare the results with existing packaging designs to quantify their thermal performance enhancements. Double-side-cooled configurations that do not use thermal interface materials are package concepts predicted to provide a low junction-to-fluid thermal resistance (compared to current packages). Dielectric-fluid-cooled concepts enable a redesign of the package to reduce the package resistance, can be implemented in single- and two-phase cooling approaches, and allow for cooling of passive components (e.g., capacitors) and bus bars.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2022

Real-time dispatch optimization for concentrating solar power with thermal energy storage

Concentrating solar power (CSP) plants present a promising path towards utility-scale renewable energy. The power tower, or central receiver, configuration can achieve higher operating temperatures than other forms of CSP, and, like all forms of CSP, naturally pairs with comparatively inexpensive thermal energy storage, which allows CSP plants to dispatch electricity according to market price incentives and outside the hours of solar resource availability. Currently, CSP plants commonly include a steam Rankine power cycle and several heat exchange components to generate high-pressure steam using stored thermal energy. The efficiency of the steam Rankine cycle depends on the temperature of the plant's operating fluid, and so is a main concern of plant operators. However, the variable nature of the solar resource and the conservatism with which the receiver is operated prevent perfect control over the receiver outlet temperature. Therefore, during periods of solar variability, collection occurs at lower-than-design temperature. To support operator decisions in a real-time setting, we develop a revenue-maximizing non-convex mixed-integer, quadradically-constrained program which determines a dispatch schedule with sub-hourly time fidelity and considers temperature-dependent power cycle efficiency. The exact nonlinear formulation proves intractable for real-time decision support. Here we present exact and inexact techniques to improve problem tractability that include a hybrid nonlinear and linear formulation. Our approach admits solutions within approximately 3% of optimality, on average, within a five-minute time limit, demonstrating its usability for decision support in a real-time setting.

14 SOLAR ENERGY↗
DOE OSTI2024

Sensing Modalities Deployed - Acoustic

Acoustic approaches to OLM are based on analyzing changes in various forms of pressure waves propagating in solids, fluids or gases. These pressure waves can vary in frequency content from infrasound (seismic events) to the megahertz region (acoustic emissions). A wide variety of commercially available pressure or stain sensing devices are used to make acoustic measurements. These sensors differ in the transduction mechanism used to convert the pressure or strain signal to an electrical output, the sensitivity, dynamic range, bandwidth, directional characteristics, and physical size. All acoustic sensors must be integrated with signal conditioning electronics to convert the sensors’ analog output to discrete digital signals that can then be further analyzed for OLM. Ultimately, the sensing properties listed above will be a function of the sensor transduction mechanism, the sensor design and the conditioning electronics.

47 OTHER INSTRUMENTATION↗
NASA NTRS2005

CFD Multiphysics Tool

The recent bold initiatives to expand the human presence in space require innovative approaches to the design of propulsion systems whose underlying technology is not yet mature. The space propulsion community has identified a number of candidate concepts. A short list includes solar sails, high-energy-density chemical propellants, electric and electromagnetic accelerators, solar-thermal and nuclear-thermal expanders. For each of these, the underlying physics are relatively well understood. One could easily cite authoritative texts, addressing both the governing equations, and practical solution methods for, e.g. electromagnetic fields, heat transfer, radiation, thermophysics, structural dynamics, particulate kinematics, nuclear energy, power conversion, and fluid dynamics. One could also easily cite scholarly works in which complete equation sets for any one of these physical processes have been accurately solved relative to complex engineered systems. The Advanced Concepts and Analysis Office (ACAO), Space Transportation Directorate, NASA Marshall Space Flight Center, has recently released the first alpha version of a set of computer utilities for performing the applicable physical analyses relative to candidate deep-space propulsion systems such as those listed above. PARSEC, Preliminary Analysis of Revolutionary in-Space Engineering Concepts, enables rapid iterative calculations using several physics tools developed in-house. A complete cycle of the entire tool set takes about twenty minutes. PARSEC is a level-zero/level-one design tool. For PARSEC s proof-of-concept, and preliminary design decision-making, assumptions that significantly simplify the governing equation sets are necessary. To proceed to level-two, one wishes to retain modeling of the underlying physics as close as practical to known applicable first principles. This report describes results of collaboration between ACAO, and Embry-Riddle Aeronautical University (ERAU), to begin building a set of level-two design tools for PARSEC. The "CFD Multiphysics Tool" will be the propulsive element of the tool set. The name acknowledges that space propulsion performance assessment is primarily a fluid mechanics problem. At the core of the CFD Multiphysics Tool is an open-source CFD code, HYP, under development at ERAU. ERAU is renowned for its undergraduate degree program in Aerospace Engineering the largest in the nation. The strength of the program is its applications-oriented curriculum, which culminates in one of three two-course Engineering Design sequences: Aerospace Propulsion, Spacecraft, or Aircraft. This same philosophy applies to the HYP Project, albeit with fluid physics modeling commensurate with graduate research. HYP s purpose, like the Multiphysics Tool s, is to enable calculations of real (three-dimensional; geometrically complex; intended for hardware development) applications of high speed and propulsive fluid flows.

Perrell, Eric R.↗
DOE OSTI2022

Application of a Novel Heat Pump Model for Estimating Economic Viability and Barriers of Heat Pumps in Dairy Applications in the United States

Heat pumps represent an important opportunity for energy savings and decarbonization. This work investigates the techno-economic performance of high-temperature heat pumps (HTHPs) for use in the U.S. dairy industry. The studied heat pump performs a 50 °C temperature lift on a waste heat stream of cleaning water and applies the upgraded heat stream to a fluid milk pasteurization process. This work involved the creation of a HTHP model that estimated the coefficient of performance (COP), internal rate of return (IRR), net present value (NPV), and payback period (PBP), and emissions saved for a heat pump replacing a natural gas boiler. Capital costs, operations, and maintenance (O&M) cost, heat pump lifetime, electricity prices, natural gas prices, and a cost of carbon were varied to perform a parametric study on the factors affecting the break-even price of HTHPs. The results show that HTHP economics are highly sensitive to COP and energy price environment, and less sensitive to capital and O&M cost variance, leading to a large scatter of positive and negative NPVs based on U.S. location. PBPs demonstrate a defined threshold, based on energy price environment, below which favorable two-to-three-year PBPs predominate. This work is focused on the U.S. dairy industry, but international application in relation to fossil vs. electricity price regimes. Heat pumps have seen wider adoption in regions with a high ratio of fossil energy to electricity prices ($/MMBTU vs. $/kWh). The U.S. has plentiful natural gas resulting in lower fossil energy prices which has reduced heat pump adoption. This paper identifies potential first mover industries for HTHP adoption and their associated price regimes even in regions with lower ratios of fossil energy to electricity prices that exist many places globally.

ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION,↗
DOE OSTI2020

Integration of a Microturbine Power Conversion Unit in MAGNET

The Microreactor Agile Non-nuclear Experimental Testbed (MAGNET) facility is being constructed at Idaho National Laboratory’s (INL’s) Energy Systems Laboratory to assist with the development, demonstration, and validation of microreactor components and systems. MAGNET will accommodate various types of test articles representative of different microreactor designs. A power conversion unit (PCU) simulator loop was proposed to use the rejected heat from the test article and mimic the thermal hydraulic conditions (e.g., temperature, pressure and flow rate) that would be experienced if an actual Brayton cycle PCU was attached. However, due to the high-estimated cost of the PCU simulator and the availability of a turbogenerator used for previous testing at Sandia National Laboratories, the PCU simulator design was abandoned in favor of integrating an actual PCU into MAGNET. A commercial Capstone C30 was modified by Sandia to use external electrical heating, rather than combustion heating, to provide a power output from 1 to ~30 kWe. The C30 has a single-stage centrifugal combustor, a static radial heat exchanger, and a radial inflow turbine arranged on a single shaft with a high-speed alternator. Since the operating temperature and energy transfer per unit working fluid mass are comparable, the MAGNET PCU will provide researchers with the ability to evaluate the test article heat transfer under representative operating conditions with the transient system behavior associated with a closed Brayton cycle PCU. This report examines the integration of a modified commercial Capstone C30 turbogenerator into MAGNET, outlines a proposed set of tests, and describes future work.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1988

Continuous flow electrophoresis system experiments on shuttle flights STS-6 and STS-7

The development of a space continuous flow electrophoresis system (CFES) is discussed. The objectives of the experiment were: (1) to use a model sample material at a high concentration to evaluate the continuous flow electrophoresis process in the McDonnell Douglass CFES instrument and compare its separation resolution and sample throughput with related devices on Earth, and (2) to expand the basic knowledge of the limitations imposed by fluid flows and particle concentration effects on the electrophoresis process by careful design and evaluation of the space experiment. Hemoglobin and polysaccharide were selected as samples of concentration effects. The results from space show a large band spread of the high concentration of the single species of hemoglobin that was principally due to the mismatch of electrical conductivity between the sample and buffer.

Snyder, Robert S.↗
NASA NTRS1988

Solar water heater for NASA's Space Station

The feasibility of using a solar water heater for NASA's Space Station is investigated using computer codes developed to model the Space Station configuration, orbit, and heating systems. Numerous orbit variations, system options, and geometries for the collector were analyzed. Results show that a solar water heater, which would provide 100 percent of the design heating load and would not impose a significant impact on the Space Station overall design is feasible. A heat pipe or pumped fluid radial plate collector of about 10-sq m, placed on top of the habitat module was found to be well suited for satisfying water demand of the Space Station. Due to the relatively small area required by a radial plate, a concentrator is unnecessary. The system would use only 7 to 10 percent as much electricity as an electric water-heating system.

Somers, Richard E.↗
NASA NTRS2022

Recent Concept Study for Cryogenic Fluid Management to Support Opposition Class Crewed Missions to Mars

NASA recently completed a mission concept study to evaluate the feasibility and propulsion technology development requirements for reduced travel duration crewed missions to Mars. A high-level goal of the study was to minimize the health impact on the crew caused by the space environment. This was implemented in the study by limiting the crew to a total of approximately-two years of in-space operations and travel time. For the initial mission, the crew would stay about 30 days on the Martian surface. The propulsive demands of such a mission are immense, and the study identified two advanced propulsion options with the potential to meet the mission requirements—both options rely on nuclear fission to provide efficient propulsive energy. One propulsion option was a nuclear electric propulsion (NEP)/Chem Hybrid, with a reactor and energy conversion system powering xenon propellant ion thrusters to provide an efficient, but lower-thrust, push for most of the mission duration. This concept also relied on a liquid oxygen/liquid methane (LO2/LCH4) chemical propulsion stage to provide high thrust for maneuvers while near the Earth and Mars. The second propulsion option was nuclear thermal propulsion (NTP), in which the reactor heats liquid hydrogen (LH2) propellant to expand through a nozzle for thrust at about twice the efficiency of the best chemical propulsion systems. Both vehicle concepts rely on storing large amounts of cryogenic propellant (either LO2/LCH4 or LH2) for multiple years in space without loss, far exceeding state-of-the-art capability. To enable this new capability, the team assumed the use of several advanced cryogenic fluid management (CFM) technologies and analyzed the integrated system performance. This included considering the vehicle-level effects of the size, mass, and power requirements of these CFM elements. Further, the team evaluated the development required to enable such a mission in the mid-2030 s and determined that it was feasible. The paper elaborates on the assumed CFM technologies, provides key analysis results, and illustrates the feasibility of technology development for the proposed solutions to the CFM challenges for each propulsion concept.

cryogenic propellant↗
DOE OSTI2021

An adaptable technique for comparative image assessment: Application to crosswell electromagnetic survey design for fluid monitoring

Reservoir integrity stewardship accompanying carbon capture and sequestration considers fluid extraction and reinjection as a risk-mitigating method against overpressuring that could lead to caprock damage and ensuing [Formula: see text] leakage. Crosswell electromagnetics offers a technically viable monitoring method with the spatial volume coverage necessary for reservoir-encompassing pressure management. However, a certain logistic dilemma for deep gas sequestration into saline and thus electrically conductive aquifers is that crosswell magnetic-field measurements underperform in the imaging of more resistive plume bodies, further exacerbated when vertical arrays intersect, as opposed to surround, plumes. Furthermore, comparative synthetic-data plume imaging of such scenarios rates the information content of magnetic-field versus electric-field 3D crosswell layouts for reservoir and infrastructure conditions of a representative pilot site in a coastal area in Florida. The image quality of the resulting plume replications can be ranked numerically through a newly proposed semblance qualifier, appraising the model goodness of fit to a given reference. In contrast to common least-squares measures for goodness of fit, the semblance formulation uses classifying logistic function types, thus enabling a better distinction of predefined anomaly features.

58 GEOSCIENCES↗
DOE OSTI2022

Relativistic Alfvén Waves Entering Charge-starvation in the Magnetospheres of Neutron Stars

Instabilities in a neutron star can generate Alfvén waves in its magnetosphere. Propagation along the curved magnetic field lines strongly shears the wave, boosting its electric current j A . We derive an analytic expression for the evolution of the wavevector k and the growth of j A . In the strongly sheared regime, j A may exceed the maximum current j0 that can be supported by the background e ± plasma. We investigate these charge-starved waves, first using a simplified two-fluid analytic model, then with first-principles kinetic simulations. We find that the Alfvén wave is able to propagate successfully even when κ ≡ j A /j 0 $\ll$ 1. It sustains j A by compressing and advecting the plasma along the magnetic field lines with an increasing Lorentz factor, γ ≳ κ 1/2 . The simulations show how plasma instabilities lead to gradual dissipation of the wave energy. Our results suggest that an extremely high charge-starvation parameter κ ≳ 10 4 may be required in order for this mechanism to power the observed fast radio bursts (FRBs) from SGR 1935+2154. However, cosmological FRBs with much higher luminosities are unlikely to be a result of charge-starvation.

79 ASTRONOMY AND ASTROPHYSICS↗