Factors affecting the sensitivity of gamma- level ring-core magnetometers.
Gamma-level ring-core magnetometer sensitivity parameters, noting frequency, dynamic differential permeability, number of pickup turns, etc
HARMONIC GENERATION↗
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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.
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Preliminary testing of a SNAP-19 TAGS RTG in support of the Pioneer F and G missions.
This paper presents the results of a preliminary performance evaluation of the SNAP-19 TAGS thermoelectric generator which was selected as the power source for the Pioneer Space Flight Mission. The performance of the SNAP-19 generator was evaluated at various input powers and fin-root temperatures. Results of this evaluation are analyzed and discussed. Tests were also performed to provide the Pioneer Flight Project Management with applicable data such as generator thermal dynamic behavior during launch and prior to deployment. These special tests measure generator performance as a function of fin-root temperature and the dynamic frequency response of the generator.
Stapfer, G.↗
Electronic high pass filter
Ultra accurate filter is used with static type pressure transducers where it is desirable to extract low frequency dynamic signals from combined static and dynamic signal. System can be calibrated at any time with dc voltages.
Peterson, V. S.↗
POGO Instabilities Suppression Evaluation
A dynamic (frequency response) analysis was made of a liquid oxygen feed system consisting of a low-speed inducer, a high-speed main pump and a positive displacement pulser utilized for simulating pogo induced pressure oscillations. Based on the results of the analysis, an active control system for suppression of pulser generated pressure oscillations was designed, fabricated and tested. The test results verified that the suppressor was effective in attenuating the generated pressure oscillations over the frequency range from 10 to 30 Hz.
Farrel, E. C.↗
Influence of thermal distortion on the anomalous behavior of a gravity gradient satellite
Consideration of the problem of determining the influence of solar heating on the low-frequency dynamic stability of a gravity-gradient satellite. The scope of the effort includes the development of a computer program that uses a quasi-static approach for describing a satellite's unsteady orbital motion. The essential feature of the quasi-static approach is that the satellite's long, slender booms reach their thermal equilibrium position solely as a result of thermal bending without consideration of the dynamic effects of boom vibration. A nonlinear analytical model and a corresponding computer program have been developed to study the effect of absorptivity, sun angle, and hinge stiffness on the stability of a satellite's motion.
Goldman, R. L.↗
Communication satellite ground station receiver performance at low data rates
Performance of satellite ground station receivers at low data rates is analyzed for power-limited satellites, when various amounts of frequency dynamics are present. Specifically, the lowest data rates for which the receiver can successfully demodulate suppressed-carrier BPSK data under a wide variety of conditions are determined. Minimum data rates on the order of 100 to 1400 bits per second are achievable with a bit error probability less than 0.00001 and with a mean time to cycle slip on the order of 1/2 hour or more, when Costas loops are employed for carrier extraction.
Riddle, L. P.↗
The phase reversal phenomenon at flow separation and reattachment
Tests were conducted on two different airfoils, one of them in a low-turbulence tunnel, to detect laminar separation and turbulent reattachment locations. A 'nonintrusive' multielement sensor consisting of a large number of closely spaced individual nickel films was vacuum deposited on a thin substrate and bonded to the airfoil model surface. Each sensor element was a part of an independent constant temperature anemometer system. Time history as well as spectral analysis of signals from surface film gauges were used to determine the surface shear flow characteristics. A major breakthrough was achieved with the discovery of phase reversal in low-frequency dynamic shear stress signals across regions of flow separation and reattachment.
Stack, J. Pete↗
Simultaneous detection of separation and transition in surface shear layers
Flush-mounted hot-film gages have proved effective in detecting boundary-layer transition and in measuring skin friction but with limited success in detecting laminar separation and reattachment. The development of multielement micro hot-film sensors, and the recent discovery of the phase reversal phenomena associated with low-frequency dynamic shear stress signals across regions of laminar separation and turbulent reattachment, have made it possible to simultaneously and unambiguously detect these surface shear layer characteristics. Experiments were conducted on different airfoils at speeds ranging from low subsonic to transonic speeds to establish the technique for incompressible and compressible flow applications. The multielement dynamic shear stress sensor technique was successfully used to detect laminar separation, turbulent reattachment, as well as, shock induced laminar and turbulent separation.
Mangalam, Siva M.↗
Finite element structural redesign by large admissible perturbations
In structural redesign, two structural states are involved; the baseline (known) State S1 with unacceptable performance, and the objective (unknown) State S2 with given performance specifications. The difference between the two states in performance and design variables may be as high as 100 percent or more depending on the scale of the structure. A Perturbation Approach to Redesign (PAR) is presented to relate any two structural states S1 and S2 that are modeled by the same finite element model and represented by different values of the design variables. General perturbation equations are derived expressing implicitly the natural frequencies, dynamic modes, static deflections, static stresses, Euler buckling loads, and buckling modes of the objective S2 in terms of its performance specifications, and S1 data and Finite Element Analysis (FEA) results. Large Admissible Perturbation (LEAP) algorithms are implemented in code RESTRUCT to define the objective S2 incrementally without trial and error by postprocessing FEA results of S1 with no additional FEAs. Systematic numerical applications in redesign of a 10 element 48 degree of freedom (dof) beam, a 104 element 192 dof offshore tower, a 64 element 216 dof plate, and a 144 element 896 dof cylindrical shell show the accuracy, efficiency, and potential of PAR to find an objective state that may differ 100 percent from the baseline design.
Bernitsas, Michael M.↗
EnviroNET
EnviroNET is a service/facility that provides users with on-line, dial-up technical information concerning environmental conditions likely to be encountered by instruments and experimental arrangements carried aboard spacecraft. EnviroNET incorporates at present a combination of expository text and numerical tables amounting to about two million characters (bytes), plus FORTRAN programs that model the space environment. The topics covered are presented in viewgraph form and include the following: advantages of EnviroNET; thermal and humidity; vibration and acoustics; electromagnetic interference; loads and low frequency dynamics; microbial and toxic contaminants; molecular contamination; natural environment; orbiter motion; particulate environment; surface interactions; spacecraft anomalies; and interactive graphics facility.
Vansant, Tim↗
Investigation on the use of optimization techniques for helicopter airframe vibrations design studies
Results of the investigation of formal nonlinear programming-based numerical optimization techniques of helicopter airframe vibration reduction are summarized. The objective and constraint function and the sensitivity expressions used in the formulation of airframe vibration optimization problems are presented and discussed. Implementation of a new computational procedure based on MSC/NASTRAN and CONMIN in a computer program system called DYNOPT for optimizing airframes subject to strength, frequency, dynamic response, and dynamic stress constraints is described. An optimization methodology is proposed which is thought to provide a new way of applying formal optimization techniques during the various phases of the airframe design process. Numerical results obtained from the application of the DYNOPT optimization code to a helicopter airframe are discussed.
Sreekanta Murthy, T.↗
A dynamic response model for pressure sensors in continuum and high Knudsen number flows with large temperature gradients
This paper develops a dynamic model for pressure sensors in continuum and rarefied flows with longitudinal temperature gradients. The model was developed from the unsteady Navier-Stokes momentum, energy, and continuity equations and was linearized using small perturbations. The energy equation was decoupled from momentum and continuity assuming a polytropic flow process. Rarefied flow conditions were accounted for using a slip flow boundary condition at the tubing wall. The equations were radially averaged and solved assuming gas properties remain constant along a small tubing element. This fundamental solution was used as a building block for arbitrary geometries where fluid properties may also vary longitudinally in the tube. The problem was solved recursively starting at the transducer and working upstream in the tube. Dynamic frequency response tests were performed for continuum flow conditions in the presence of temperature gradients. These tests validated the recursive formulation of the model. Model steady-state behavior was analyzed using the final value theorem. Tests were performed for rarefied flow conditions and compared to the model steady-state response to evaluate the regime of applicability. Model comparisons were excellent for Knudsen numbers up to 0.6. Beyond this point, molecular affects caused model analyses to become inaccurate.
Whitmore, Stephen A.↗
A Two-Timescale Discretization Scheme for Collocation
The development of a two-timescale discretization scheme for collocation is presented. This scheme allows a larger discretization to be utilized for smoothly varying state variables and a second finer discretization to be utilized for state variables having higher frequency dynamics. As such. the discretization scheme can be tailored to the dynamics of the particular state variables. In so doing. the size of the overall Nonlinear Programming (NLP) problem can be reduced significantly. Two two-timescale discretization architecture schemes are described. Comparison of results between the two-timescale method and conventional collocation show very good agreement. Differences of less than 0.5 percent are observed. Consequently. a significant reduction (by two-thirds) in the number of NLP parameters and iterations required for convergence can be achieved without sacrificing solution accuracy.
Desai, Prasun↗
Dynamic Analysis of a Building Under Rocket Engine Plume Acoustic Load
Studies have been performed to develop finite-element modeling and simulation techniques to predict the dynamic structural response of Building 4010 to the acoustic load from the plume of high-thrust rocket motors. The building is the Test Control Center and general office space for the E-complex at Stennis Space Center. It is a large single span; light-structured building located approximately 1,000 feet from the E-1 test stand. A three-dimensional shell/beam combined model of the building was built using Pro/Engineer platform and imported into Pro/Mechanica for analysis. An Equivalent Shell technique was developed to simplify the highly complex building structure so that the calculation is more efficient and accurate. A deterministic approach was used for the dynamic analysis. A pre-stressed modal analysis was performed to simulate the weight stiffening of the structure, through which about 200 modes ranging from 0 to 35 Hz were identified. In an initial dynamic frequency analysis, the maximum response over the model was found. Then the complete 3-D distributions of the displacement, as well as the stresses, were calculated through a final frequency analysis. The results were compared to a strain gage and accelerometer recordings from rocket engine tests and showed reasonable agreement.
Qian, Z.↗
Communications During Critical Mission Operations: Preparing for InSight's Landing on Mars
Radio communications with deep space missions are often taken for granted due to the impressively successful records since, for decades, the technology and infrastructure have been developed for ground and flight systems to optimize telemetry and commanding. During mission-critical events such as the entry, descent, and landing of a spacecraft on the surface of Mars, the signal's level and frequency dynamics vary significantly and typically exceed the threshold of the budgeted links. The challenge is increased when spacecraft shed antennas with heat shields and other hardware during those risky few minutes. We have in the past successfully received signals on Earth during critical events even ones not intended for ground reception. These included the UHF signal transmitted by Curiosity to Marsorbiting assets. Since NASA's Deep Space Network does not operate in the UHF band, large radio telescopes around the world are utilized. The Australian CSIRO Parkes Radio Telescope supported the Curiosity UHF signal reception and DSN receivers, tools, and expertise were used in the process. In preparation for the InSight mission's landing on Mars in 2016, preparations are underway to support the UHF communications. This paper presents communication scenarios with radio telescopes, and the DSN receiver and tools. It also discusses the usefulness of the real-time information content for better response time by the mission team towards successful mission operations.
Radio Science↗
Aeroservoelastic Modeling of Body Freedom Flutter for Control System Design
The communication of this method is being used by NASA in the ongoing collaborations with groups interested in the X-56A flight test program. Model generation for body freedom flutter Addressing issues in: State Consistency, Low frequency dynamics, Unsteady aerodynamics. Applied approach to X-56A MUTT: Comparing to flight test data.
Degree of Freedom↗
Situational Awareness of Grid Anomalies (SAGA)
The modern power industry becomes more vulnerable to cyber events due to the growing interconnectivity, interdependence, and complexity of the electric power grid. High-fidelity modeling and simulation tools that support the preventative risk analysis on potential cyber-relevant events is essential for ensuring the situational awareness of the system operator as it provides an inexpensive and risk-free environment to test the system responses under various cyber-relevant events and hereby can support research on cyber anomaly detection, optimal protective resource allocation, and mitigation measures. In this webinar, we will share NREL's cybersecurity research capabilities by highlighting the development of a scalable cyber-physical event test bed and demonstration with real hardware in the loop. The developed cyber-physical event test bed is backboned by an integrated transmission, distribution, and communication dynamic co-simulation framework and a plug-and-play cyber event generation module. It is designed to be modular and compatible with parallel computing, and thereby supports large-scale system simulations at an affordable computation cost. The test bed can capture millisecond-to-minutes dynamic frequency and voltage responses under cyber events from the bulk transmission system to the active distribution systems and distributed energy resources at the grid edge.
co-simulation↗
Development and benchmarking of transient nodal code SIMULATE5-K neutron kinetics solver
SIMULATE5-K is Studsvik's next generation best estimate transient code. The time dependent diffusion equation is solved with a nodal method consistent with that implemented in the licensed core design code SIMULATE5. Arbitrary number of neutron and delayed neutron precursor groups can be used. For the solution of the spatial problem, the coupling coefficients used to relate the node leakages are found by first converting the time dependent diffusion equation to a static diffusion equation with the use of flux and delayed neutron precursor dynamic frequencies. Once the static-like equations are obtained, the multi-group analytical nodal model is used to obtain the coupling coefficients, expressing the node leakage in terms of adjacent node average fluxes. The coupling coefficients are then inserted into the time dependent nodal balance equation. For the time integration, the time dependent neutron balance equation is solved with the frequency transformation method. The treatment of the temporal dependence yields a fixed source problem which can be solved utilizing the existing fixed-source methodology. The primary purpose of this paper is to describe the neutron kinetics methodology implemented in SIMULATE5-K. The accuracy of the method is demonstrated for a series of well-known, neutronic-only benchmark problems. (author)
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗