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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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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Determination of travelling ionospheric disturbances

A total of 35 days of Faraday rotation data was obtained from the ATS-6 radio beacon experiment operating with the closely spaced network of Elbert, Table Mountain, and Fort Morgan. The 140-MHz Faraday bandpass data are uncorrelated in the transmission range from 8 to 45 minutes. There are distinct, well correlated, and time-displaced maxima and minima that allow the calculation of the speed and direction of horizontal motions of plane fronts of disturbances in the ionosphere. For some selected events, velocities between 88 and 278 m/sec were obtained.

Degenhardt, W.↗
NASA NTRS1980

The 1980 summer research fellowship program

The problem of incorporating visual input into robot systems is described. The photochemistry of the stratosphere, particularly possible permutations of the ozone layer, is discussed. Photoelectrochemical properties of metal thio-hypodiphosphates are investigated. Extreme eigenvalues are computed by the Lancqos approach. The rotational Raman spectra of the molecular atmosphere is studied. A computer operated mathematical symbolic manipulation system is described. Preparation of polycrystalline semiconductor electrodes of tungsten and molybdenum dichalcogenides is received.

Darden, G. C.↗
NASA NTRS1982

Multiprism collimator

A special purpose optical collimator system which generates multiple collimated light beams with precisely related angular separation of the beams, is comprised of a stack of relatively flat plate-like refracted prisms in the form of wedges. Each prism has a specified angular deviation, mounted on top of one another in a fixture which holds the wedges so that they are adapted to operate at minimum angular deviation and thus are relatively insensitive to rotational and angular charges. A collimated sources of monochromatic light, generated for example by a helium-neon laser and a collimated beam expander, provides a common incident beam to the wedges whereupon a number equally spaced emergent beams are provided.

Minott, P. O.↗
NASA NTRS1985

Deposition of Na2SO4 from salt-seeded combustion gases of a high velocity burner rig

With a view to developing simulation criteria for the laboratory testing of high-temperature materials for gas turbine engines, the deposition rates of sodium sulfate from sodium salt-seeded combustion gases were determined experimentally using a well instrumented high-velocity burner. In the experiments, Na2SO4, NaCl, NaNO3, and simulated sea salt solutions were injected into the combustor of the Mach 0.3 burner rig operating at constant fuel/air ratios. The deposits formed on an inert rotating collector were then weighed and analyzed. The experimental results are compared to Rosner's vapor diffusion theory. Some additional test results, including droplet size distribution of an atomized salt spray, are used in interpreting the deposition rate data.

Santoro, G. J.↗
NASA NTRS1990

Monitoring Small Deformations In An Instrument

Relatively simple source/detector pairs measure changes affecting optical alignment. System for monitoring small thermal, gravitational, and dynamical deformations in x-ray telescope includes two sources of infrared light, each associated with dual-axis, position-sensing photodiode. Principle of operation straightforward and applicable to monitoring of small lateral translations and/or rotations between different parts in machinery, buildings, bridges, ships, and other large structures.

Hagopian, John G.↗
NASA NTRS1991

Rotating pressure measurement system using an on board calibration standard

A computer-controlled multichannel pressure measurement system was developed to acquire detailed flow field measurements on board the Large Low Speed Centrifugal Compressor Research Facility at the NASA Lewis Research Center. A pneumatic slip ring seal assembly is used to transfer calibration pressures to a reference standard transducer on board the compressor rotor in order to measure very low differential pressures with the high accuracy required. A unique data acquisition system was designed and built to convert the analog signal from the reference transducer to the variable frequency required by the multichannel pressure measurement system and also to provide an output for temperature control of the reference transducer. The system also monitors changes in test cell barometric pressure and rotating seal leakage and provides an on screen warning to the operator if limits are exceeded. The methods used for the selection and testing of the the reference transducer are discussed, and the data acquisition system hardware and software design are described. The calculated and experimental data for the system measurement accuracy are also presented.

Senyitko, Richard G.↗
NASA NTRS1992

Study of high pressure and high current arcs in the cathode region of an arc heater

This paper investigates the behavior of high pressure, high current arcs in the downstream electrode region (cathode) of an arc heater. Computations are done for operating pressures in the range 50 atm to 200 atm and load currents in the range 6000 amp to 18,000 amp. At high pressures, due to the high current carrying capability of the dense gas, spot size remains reasonably small even for high load currents. Its value is 1.1 mm for a 50 atm arc with a load current of 18,000 amp. By increasing pressure it can be reduced further. Smaller spot size may allow us to design thinner electrode rings. Spot temperatures are high enough to cause ablation of the electrode material. In order to reduce material ablation at very high currents, the operating pressure must also be high and the arc should be rotated.

Durgapal, Prabha↗
NASA NTRS1995

High performance stepper motors for space mechanisms

Hybrid stepper motors are very well adapted to high performance space mechanisms. They are very simple to operate and are often used for accurate positioning and for smooth rotations. In order to fulfill these requirements, the motor torque, its harmonic content, and the magnetic parasitic torque have to be properly designed. Only finite element computations can provide enough accuracy to determine the toothed structures' magnetic permeance, whose derivative function leads to the torque. It is then possible to design motors with a maximum torque capability or with the most reduced torque harmonic content (less than 3 percent of fundamental). These later motors are dedicated to applications where a microstep or a synchronous mode is selected for minimal dynamic disturbances. In every case, the capability to convert electrical power into torque is much higher than on DC brushless motors.

Sega, Patrick↗
NASA NTRS1996

Pulse Detonation Engine Air Induction System Analysis

A preliminary mixed-compression inlet design concept for potential pulse-detonation engine (PDE) powered supersonic aircraft was defined and analyzed. The objectives of this research were to conceptually design and integrate an inlet/PDE propulsion system into a supersonic aircraft, perform time-dependent CFD analysis of the inlet flowfield, and to estimate the installed PDE cycle performance. The study was baselined to a NASA Mach 5 Waverider study vehicle in which the baseline over/under turboramjet engines were replaced with a single flowpath PDE propulsion system. As much commonality as possible was maintained with the baseline configuration, including the engine location and forebody lines. Modifications were made to the inlet system's external ramp angles and a rotating cowl lip was incorporated to improve off-design inlet operability and performance. Engines were sized to match the baseline vehicle study's ascent trajectory thrust requirement at Mach 1.2. The majority of this study was focused on a flight Mach number of 3.0. The time-dependent Navier Stokes CFD analyses of a two-dimensional approximation of the inlet was conducted for the Mach 3.0 condition. The Lockheed Martin Tactical Aircraft Systems-developed FALCON CFD code with a two equation 'k-1' turbulence model was used. The downstream PDE was simulated by an array of four sonic nozzles in which the flow areas were rapidly varied in various opening/closing combinations. Results of the CFD study indicated that the inlet design concept operated successfully at the Mach 3.0 condition, satisfying mass capture, total pressure recovery, and operability requirements. Time-dependent analysis indicated that pressure and expansion waves from the simulated valve perturbations did not effect the inlet's operability or performance.

Pegg, R. J.↗
NASA NTRS1999

Efficient IR Transmission Diffraction Grating for Circularly Polarized Light

Numerical methods, using rigorous coupled wave theory, are used to design rectangular relief diffraction gratings for an infrared application which requires comparable first order efficiencies in the TE and TM polarization states. The depth, period, and fill factor of the grating are varied to identify optimal two level binary lamellar grating profiles which predict efficiencies for individual TM and TE polarizations above 75 percent, while keeping the difference between the two efficiencies within 10 percent. The application at hand is a rotating, transmissive diffractive scanner for space-based coherent lidar. The operating wavelength is 2.0 microns. A collimated, circularly polarized beam is incident on the diffractive scanner at the Bragg angle; 30 and 45 degree beam deflection angles being studied. Fused silica is the substrate material of choice. Selected designs are fabricated on 3 inch fused silica substrates using lithographic methods. The performance of the test pieces is measured and compared to theoretical predictions.

Cole, Helen↗
NASA NTRS2001

Predictive Compensator Optimization for Head Tracking Lag in Virtual Environments

We examined the perceptual impact of plant noise parameterization for Kalman Filter predictive compensation of time delays intrinsic to head tracked virtual environments (VEs). Subjects were tested in their ability to discriminate between the VE system's minimum latency and conditions in which artificially added latency was then predictively compensated back to the system minimum. Two head tracking predictors were parameterized off-line according to cost functions that minimized prediction errors in (1) rotation, and (2) rotation projected into translational displacement with emphasis on higher frequency human operator noise. These predictors were compared with a parameterization obtained from the VE literature for cost function (1). Results from 12 subjects showed that both parameterization type and amount of compensated latency affected discrimination. Analysis of the head motion used in the parameterizations and the subsequent discriminability results suggest that higher frequency predictor artifacts are contributory cues for discriminating the presence of predictive compensation.

Adelstein, Barnard D.↗
NASA NTRS2002

Further Examination of the Vibratory Loads Reduction Results from the NASA/ARMY/MIT Active Twist Rotor Test

The vibration reduction capabilities of a model rotor system utilizing controlled, strain-induced blade twisting are examined. The model rotor blades, which utilize piezoelectric active fiber composite actuators, were tested in the NASA Langley Transonic Dynamics Tunnel using open-loop control to determine the effect of active-twist on rotor vibratory loads. The results of this testing have been encouraging, and have demonstrated that active-twist rotor designs offer the potential for significant load reductions in future helicopter rotor systems. Active twist control was found to use less than 1% of the power necessary to operate the rotor system and had a pronounced effect on both rotating- and fixed-system loads, offering reductions in individual harmonic loads of up to 100%. A review of the vibration reduction results obtained is presented, which includes a limited set of comparisons with results generated using the second-generation version of the Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics (CAMRAD II) rotorcraft comprehensive analysis.

Wilbur, Matthew L.↗
NASA NTRS2004

Absorption Reveals and Hydrogen Addition Explains New Interstellar Aldehydes: Propenal and Propanal

New interstellar molecules propenal (CH2CHCHO) and propanal (CH3CH2CHO) have been detected largely in absorption toward the star-forming region Sagittarius B2(N) by means of rotational transitions observed with the 100-m Green Bank Telescope (GBT) operating in the range of 18 GHz (lambda approximately 1.7 cm) to 26 GHz (lambda approximately 1.2 cm). The GBT was also used to observe the previously reported interstellar aldehyde propynal (HC2CHO) in Sagittarius B2(N) which is known for large molecules believed to form on interstellar grains. The presence of these three interstellar aldehydes toward Sagittarius B2(N) strongly suggests that simple hydrogen addition on interstellar grains accounts for successively larger molecular species: from propynal to propenal and from propenal to propanal. Energy sources within Sagittarius B2(N) likely permit the hydrogen addition reactions on grain surfaces to proceed. This work demonstrates that successive hydrogen addition is probably an important chemistry route in the formation of a number of complex interstellar molecules. We also searched for but did not detect the three-carbon sugar glyceraldehyde (CH2OHCHOHCHO).

Hollis, J. M.↗
NASA NTRS2012

Cassini Thruster Calibration Algorithm Using Reaction Wheel Biasing Data

Thrust force estimates for the reaction control thrusters on-board Cassini spacecraft are presented in this paper. Cassini consists of two thruster branches (A and B) each with eight thrusters. The four Z-thrusters control the X and Y-axes, while the four Y-thrusters control the Z-axis. It is important to track the thrust force estimates in order to detect any thruster degradation and for supporting various activities in spacecraft operations (Titan flyby, spacecraft maneuvers). The Euler equation, which describes the rotational motion of the spacecraft during a reaction wheel bias event, is used to develop the algorithm. The thrust estimates are obtained from the pseudo inverse solution using flight telemetry during the bias. Results show that the A-branch Z3A and Z4A thrusters exhibited degraded thrust in November 2008. Due to the degraded thrust performance of Z3A and Z4A, A-branch usage was discontinued and prime branch was swapped to B-branch in March 2009. The thrust estimates from the B-branch do not show any degradation to date. The algorithm is used to trend the B-branch thrust force estimates as the mission continues.

attitude control↗
NASA NTRS2018

An Evolutionary Computation System Design Concept for Developing Controlled Closed Ecosystems: An Intelligent Systems Approach to Foster Gravitational Ecosystem Research for Developing Sustainable Communities in Space and on Earth

An adjustably-autonomous intelligent systems approach for developing Closed Ecosystems (CESs) is presented, which includes a design concept and preliminary design details for the Controlled Closed-Ecosystem Development System (CCEDS) and the Orbiting Modular Artificial-Gravity Spacecraft (OMAGS). The paper is divided into three sections: CESs, the CCEDS Design Concept, and Orbiting Fractional-Gravity Closed Ecosystems OMAGS design concept. The first section briefly describes Closed EcoSystems (CESs), complex adaptive systems, biomes, microbial microbiomes, and their relevance for the study of astrobiology. This section also discusses initial efforts in the development of Closed Environment Life Support Systems (CELSSs) for sustainable communities in space and on Earth. This section concludes with a discussion of the bioregenerative life support system challenge of and the corresponding consequences due to the inverse relationship of the very small human biomass/non-human biomass ratio overall on the Earth with respect to the extremely large human biomass/non-human-biomass ratio found in cities and the International Space Station. The second section describes the CCEDS design concept, which consists of a population of controlled colonies of CES Modules (CESMs), each an integrated CES, continually generating data for an intelligent system that operates the CESs and their CESMs. A variety of CESM types and their use are briefly described. The CCEDS intelligent system uses an evolutionary computation algorithm described in this section to develop and optimize these CESs to increase their viability duration and the size of the animals they support with the ultimate goal to support populations of humans, both on Earth and in space. The CCEDS architecture, its five control subsystems, and its five evolutionary computation levels are also discussed. The section concludes with a discussion of several CCEDS design strategies. The third section summarizes the OMAGS design concept for a spacecraft with a payload consisting of CESs in an orbiting spacecraft centrifuge that operates for at least 5 years. The spacecraft concept is described including its 150cm-radius centrifuge with a 2 ton & 3,000 liter bioscience payload capacity for 24 CESMs. The centrifuge design has four physical levels for its CESMs, each level subject to a different fractional gravity level. This section presents the spacecraft benefits of being designed and operated such that the spacecraft and payload centrifuge wheel counter-rotate resulting in net zero angular momentum and zero gyroscopic forces. Artificial-gravity generation by centripetal acceleration is also discussed. This section concludes by showing the external specifications of the CESMs and their layout in the centrifuge, followed by discussing the multi-payload module rationale. In tandem, the CCEDS and OMAGS systems can be used to foster gravitational ecosystem research for developing sustainable communities in space and on Earth.

Dorais, Gregory A.↗
DOE OSTI2025

Vibroacoustic Process Monitoring of 5-Stage Centrifugal Contactors

Vibroacoustic monitoring was investigated to aid in informing process operators with parameters regarding aqueous separation techniques. These techniques have a wide range of applications including nuclear fuel reprocessing. A small-scale solvent extraction system was set up with five magnetic drive contactors and two piston pumps to collect realistic operation. Vibration sensors were placed on three of the contactors and both pumps, and a microphone was placed near the system. Contactor rotational speed and pump flow rate were varied with known values to compare against measured vibroacoustic signatures. Spectral analysis allowed for the determination of contactor rotational speed and the ratio of organic to aqueous flow rate, an important parameter for ensuring optimal extraction. Vibration metrics such as kurtosis and crest factor provided additional details regarding individual rotational speeds and have potential in examination of faults for predictive maintenance. Overall, results indicate the capability of vibroacoustic monitoring to improve operator awareness and process outcomes.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1989

Spray automated balancing of rotors - How process parameters influence performance

This paper addresses the application of spray-automated balancing of rotors, and the influence that various operating parameters will have on balancing performance. Spray-automated balancing uses the fuel-air repetitive explosion process to imbed short, discrete bursts of high velocity, high temperature powder into a rotating part at an angle selected to reduce unbalance of the part. The shortness of the burst, the delay in firing of the gun, the speed of the disk and the variability in speed all influence the accuracy and effectiveness of the automated balancing process. The paper evaluates this influence by developing an analytical framework and supplementing the analysis with empirical data obtained while firing the gun at a rotating disk. Encouraging results are obtained, and it is shown that the process should perform satisfactorily over a wide range of operating parameters. Further experimental results demonstrate the ability of the method to reduce vibration levels induced by mass unbalance in a rotating disk.

Smalley, A. J.↗
NASA NTRS2000

Trajectories in Close Proximity to Asteroids

Spacecraft motion in close proximity to irregularly shaped, rotating bodies such as asteroids presents a unique dynamical environment as compared to most space missions. There are several fundamental novelties in this environment that spacecraft must deal with. These include the possibility of orbital instabilities that can act over very short time spans (on the order of hours for some systems), possible non-uniform rotation of the central gravity field, divergence of traditional gravity field representations when close to the asteroid surface, dominance of perturbing forces, an extremely large asteroid model parameter space that must be prepared for in the absence of reliable information, and the possibility of employing new and novel trajectory control techniques such as hovering and repeated landings on the asteroid surface. An overview of how these novelties impact the space of feasible close proximity operations and how different asteroid model properties will affect their implementation is given. In so doing, four fundamental types of close proximity operations will be defined. Listed in order of increasing technical difficulty these are: (1) close, stable orbits; (2) low-altitude flyovers; (3) landing trajectories; and (4) hovering trajectories. The feasibility and difficulty of implementing these operations will vary as a function of the asteroid shape, size, density, and rotation properties, and as a function of the spacecraft navigation capability. Additional information is contained in the original extended abstract.

Scheeres, D. J.↗