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Brushless dc spin motor is designed to use Hall effect probes as means of revolving rotor position and controlling motor winding currents. This results in 3 to 1 reduction in watt-hours required for wheel acceleration, a 2 to 1 reduction in power to run wheel, and a 10 to 1 reduction in the electronics size and weight.
Photometers at 3914 A and 5577 A and an optical imager were part of an experimental package launched on a sounding rocket in the 1987 Wave Induced Particle Precipitation campaign at Wallops Island, Virginia. The objective was to measure lightning-induced electron precipitation (LEP) by means of its optical signature. This was the first attempt to measure LEP using rocket-borne optical instrumentation. Launch criteria included nearby thunderstorm activity and ground-based observations of Trimpi events. Lightning flashes are clearly discernible in the data. The photometer data was also characterized by large spin and precession modulations in the photon count rate, consistent with elevated steady particle fluxes in the northern portion of the instrument field of view. No evidence of LEP was observed by the photometers or onboard particle detectors (Arnoldy and Kintner, 1989). Analysis of the data has made it possible to place an upper limit of 0.0008 ergs/sq cm per sec on any burst precipitation energy flux that may have occurred during the rocket flight in the regions explored by the photometers.
Research is being done at the Glenn Research Center (GRC) developing new kinds of batteries that do not depend on a solution. Currently, batteries use liquid electrolytes containing lithium. Problems with the liquid electrolyte are (1) solvents used can leak out of the battery, so larger, more restrictive, packages have to be made, inhibiting the diversity of application and decreasing the power density; (2) the liquid is incompatible with the lithium metal anode, so alternative, less efficient, anodes are required. The Materials Department at GRC has been working to synthesize polymer electrolytes that can replace the liquid electrolytes. The advantages are that polymer electrolytes do not have the potential to leak so they can be used for a variety of tasks, small or large, including in the space rover or in space suits. The polymers generated by Dr. Mary Ann Meador's group are in the form of rod -coil structures. The rod aspect gives the polymer structural integrity, while the coil makes it flexible. Lithium ions are used in these polymers because of their high mobility. The coils have repeating units of oxygen which stabilize the positive lithium by donating electron density. This aids in the movement of the lithium within the polymer, which contributes to higher conductivity. In addition to conductivity testing, these polymers are characterized using DSC, TGA, FTIR, and solid state NMR. Solid state NMR is used in classifying materials that are not soluble in solvents, such as polymers. The NMR spins the sample at a magic angle (54.7') allowing the significant peaks to emerge. Although solid state NMR is a helpful technique in determining bonding, the process of preparing the sample and tuning it properly are intricate jobs that require patience; especially since each run takes about six hours. The NMR allows for the advancement of polymer synthesis by showing if the expected results were achieved. Using the NMR, in addition to looking at polymers, allows for participation on a variety of other projects, including aero-gels and carbon graphite mat en als. The goals of the polymer electrolyte research are to improve the physical properties of the polymers. This includes improving conductivity, durability, and expanding the temperature range over which it is effective. Currently, good conductivity is only present at high temperatures. My goals are to experiment with different arrangements of rods and coils to achieve these desirable properties. Some of my experiments include changing the number of repeat units in the polymer, the size of the diamines, and the types of coil. Analysis of these new polymers indicates improvement in some properties, such as lower glass transition temperature; however, they are not as flexible as desired. With further research we hope to produce polymers that encompass all of these properties to a high degree.
In order to improve manufacturing efficiency and reduce structural mass and costs in the production of launch vehicle structures, NASA is pursuing a wide-range of innovative, near-net shape manufacturing technologies. A technology that combines friction stir welding (FSW) and spin-forming has been applied to manufacture a single-piece crew module using Aluminum-Lithium (AL-Li) Alloy 2195. Plate size limitations for Al-Li alloy 2195 require that two plates be FSW together to produce a spin-forming blank of sufficient size to form the crew module. Subsequent forming of the FSW results in abnormal grain growth (AGG) within the weld region upon solution heat treatment (SHT), which detrimentally impacts strength, ductility, and fracture toughness. The current study seeks to identify microstructural factors that contribute to the development of AGG. Electron backscatter diffraction (EBSD) was used to correlate driving forces for AGG, such as stored energy, texture, and grain size distributions, with the propensity for AGG. Additionally, developmental annealing treatments prior to SHT are examined to reduce or eliminate the occurrence of AGG by promoting continuous, or uniform, grain growth
A new mechanism for primordial melting of chondrules based upon heating by relativistic electrons accelerated by reconnecting magnetic field lines is discussed. This mechanism is free of the creation-annihilation problem of collisions used for heating. The basic requirements for reconnection are an interplanetary magnetic field with regions of reversals. An early magnetic field is inferred from the paleomagnetism of meteorites and the requirements of solar spin-down, while the field reversals upon which the reconnection is based are a common property of the present epoch solar wind.
Vibration in turbomachinery can cause blade failures and leads to the use of heavier, thicker blades that result in lower aerodynamic efficiency and increased noise. Metal and/or composite fatigue in the blades of jet engines has resulted in blade destruction and loss of lives. Techniques for suppressing low-frequency blade vibration, such as gtuned circuit resistive dissipation of vibratory energy, h or simply "passive damping," can require electronics incorporating coils of unwieldy dimensions and adding unwanted weight to the rotor. Other approaches, using vibration-dampening devices or damping material, could add undesirable weight to the blades or hub, making them less efficient. A wireless inductive power device (WIPD) was designed, fabricated, and developed for use in the NASA Glenn's "Dynamic Spin Rig" (DSR) facility. The DSR is used to simulate the functionality of turbomachinery. The relatively small and lightweight device [10 lb (approx.=4.5 kg)] replaces the existing venerable and bulky slip-ring. The goal is the eventual integration of this technology into actual turbomachinery such as jet engines or electric power generators, wherein the device will facilitate the suppression of potentially destructive vibrations in fan blades. This technology obviates slip rings, which require cooling and can prove unreliable or be problematic over time. The WIPD consists of two parts: a remote element, which is positioned on the rotor and provides up to 100 W of electrical power to thin, lightweight piezoelectric patches strategically placed on/in fan blades; and a stationary base unit that wirelessly communicates with the remote unit. The base unit supplies inductive power, and also acts as an input and output corridor for wireless measurement, and active control command to the remote unit. Efficient engine operation necessitates minimal disturbance to the gas flow across the turbine blades in any effort to moderate blade vibration. This innovation makes it possible to moderate vibration on or in turbomachinery blades by providing 100 W of wireless electrical power and actuation control to thin, lightweight vibration-suppressing piezoelectric patches (eight actuation and eight sensor patches in this prototype, for a total of 16 channels) positioned strategically on the surface of, or within, titanium fan blades, or embedded in composite fan blades. This approach moves significantly closer to the ultimate integration of "active" vibration suppression technology into jet engines and other turbomachinery devices such as turbine electrical generators used in the power industry. The novel feature of this device is in its utilization of wireless technology to simultaneously sense and actively control vibration in rotating or stationary turbomachinery blades using piezoelectric patches. In the past, wireless technology was used solely for sensing and diagnostics. This technology, however, will accomplish much more, in terms of simultaneously sensing, suppressing blade vibration, and making it possible for detailed study of vibration impact in turbomachinery blades.
The components of the one- and two-particle density matrices resulting from spin projection of a single-determinant wave function are rederived by the method of expansion in terms of the natural orbitals of charge density, and the results are found to diverge from those given by Harriman and Sando for the two-particle case. The theory is generalized to include molecules with unequal numbers of electrons and basis orbitals and is applied to a number of organic molecules and ions. The correctness and internal consistency of the results argue in favor of the modification described.
Four related tasks are discussed for data transmission from a probe prior to entering the atmosphere of Jupiter to an orbiting spacecraft in a trajectory past the planet: (1) link analysis and design; (2) system conceptual design; (3) Doppler measurement analysis; and (4) an electronically despun antenna. For tasks 1, 3, and 4, an analytical approach was developed and combined with computational capability available to produce quantitative results corresponding to requirements and constraints given by NASA, ARC. One constraint having a major impact on the numerical results of the link analysis was the assumption of a nonsteerable antenna on a spinning orbiter. Other constraints included the interplanetary trajectory and the approach trajectory. Because the Jupiter Orbiter Probe (JOP) program is currently in a state of evolution, all requirements and constraints applied during this study are subject to change. However, the relationships of parameters as developed will remain valid and will aid in planning Jupiter missions.
The evolution of guidance and control systems for United States planetary and unmanned lunar spacecraft over the last 20 years is traced. The characteristics of the guidance and control systems used on spacecraft from the Range lunar impactor to the planned Galileo Jupiter orbiter and entry probe are surveyed, with attention given to the uses of three-axis stabilized, spin-stabilized and dual-spin designs. System performance trends that have evolved to meet the increasing science and mission requirements of the spacecraft are considered in the areas of attitude references, control consumables, dynamics and system modeling, thrust vector control, optical navigation, manuever turns, maneuver velocity control, instrument pointing, and antenna pointing. Hardware trends in optical sensors, inertial sensors, processing electronics, electromechanical devices, and system testing and reliability are also reviewed. The achievements represented by these advances are emphasized, and it is predicted that future developments will be in the areas of increased control system autonomy and performance requirements.
The rotational spectrum of the aluminum monoxide radical in the ground electronic state X 2Sigma(+) was observed in the millimeter- and submillimeter-wave region. Aluminum monoxide radicals were generated directly in a flow reactor absorption cell by the reaction of N2O with aluminum vaporized from a high-temperature crucible. The observed spectrum was analyzed to yield molecular constants including the rotational constant, centrifugal distortion constant, spin-rotation interaction constant, magnetic hyperfine interaction constants, and nuclear quadrupole coupling constant.
Flexible circuits with superconducting wiring atop polyimide thin films are being studied to connect large numbers of wires between stages in cryogenic apparatus with low heat load. The feasibility of a full microstrip process, consisting of two layers of superconducting material separated by a thin dielectric layer on 5 mil (approximately 0.13 mm) Kapton sheets, where manageable residual stress remains in the polyimide film after processing, has been demonstrated. The goal is a 2-mil (approximately 0.051-mm) process using spin-on polyimide to take advantage of the smoother polyimide surface for achieving highquality metal films. Integration of microstrip wiring with this polyimide film may require high-temperature bakes to relax the stress in the polyimide film between metallization steps.
Numerical sequences of rotating axisymmetric nonmagnetic equilibrium models are constructed which represent the evolution of a barytropic star as it accretes material from a rotating medium. Two accretion geometries are considered - one approximating accretion from a rotating cloud and the other, accretion from a Keplerian disk. It is assumed that some process, such as Ekman spin-up or nonequilibrium oscillations, maintains nearly constant angular velocity along cylinders about the rotation axis. Transport of angular momentum in the cylindrically radial direction by viscosity is included. Fluid instabilities and other physical processes leading to enhancement of this transport are discussed. Particular application is made to zero-temperature white-dwarf models, using the degenerate electron equation of state. An initially nonrotating 0.566-solar-mass white dwarf is followed during the accretion of more than one solar mass of material. Applications to degenerate stellar cores, to mass-transfer binary systems containing white dwarfs, such as novae and dwarf novae, to Type I supernovae, and to galactic X-ray sources are considered.
The companion in the eclipsing millisecond PSR 1957 + 20 appears to be strongly heated by the pulsar and may also be rapidly losing mass due to that heating. A new mechanism is presented by which the heating may be accomplished: diffusion of mildly relativistic electron-positron pairs from the pulsar's relativistic wind through a thermal wind issuing from the companion. Wave-particle scattering regulates the depth at which the pairs deposit their energy; requirements of self-consistency place bounds on the wave spectrum and pair distribution function. If the pairs carry over about 10 percent of the pulsar spin-down luminosity, and the companion's heavy element abundance is subsolar, the heating rate can be adequate to drive a wind with sufficient momentum flux to explain the eclipse geometry. Annihilation photons then heat the companion beneath its photosphere and supply a significant part of the power for the optical luminosity. This model also suggests that the eclipse duration decreases sharply above a critical photon frequency.
Although the PSR 1957+20 binary system displays a large orbital period derivative, radio observations of the ablated wind from the companion reveal a low free electron density. If the orbital period derivative provides a true indication of the mass loss rate, then the ablated material must be overwhelmingly neutral or largely confined to a narrow region about the orbital plane. However, the companion's high orbital velocity, the observed turbulence in the eclipsing wind, and the energy density of the pulsar's spin-down radiation conspire to make a neutral evaporate unlikely. Radio, optical and infrared observations are shown to suggest that the companion to PSR 1957+20 is bloated, perhaps approaching the size of its Roche lobe. The wind off the companion is most probably a low velocity flow which does not travel far from the orbital plane.
At about 14,800 km from the Comet Halley nucleus, on the inbound leg, at least six of the sensors onboard the Giotto spacecraft observed an unusual, brief (about 30 to 500 ms) event: the ion-mass spectrometer data show a brief flow of energetic (up to several hundred electron volts) plasma consisting of protons, water group, and heavier ions. The Johnstone plasma analyzer data show a short burst of plasma, while the dust impact detector system data show an impact event in four of its detectors. The magnetometer signature of the event shows two brief dips in the field. The sudden change in the spacecraft attitude and spin rate observed by the camera at that same time has been interpreted as the result of a large (5 mg or more) dust-particle impact on the front bumper shield of the spacecraft. In addition, at about the same time the spacecraft star-tracker suffered damage. The report combines direct measurements of the composition and dynamics of a dust-impact plasma cloud, the dust particle mass, and the location of the impact on the spacecraft. Analysis of the data indicate that the impacting particle was water or ice-bearing, possibly loosely compared, and was composed of one or more of: carbon, nitrogen, and silicon.
Three dimensional 'snapshots' of the large scale solar magnetic field topology as well as the solar wind electron density distribution from about 0.1 to 1 AU are obtained by tracking traveling solar radio bursts at the hectometer and kilometer wavelengths with instruments aboard the ISEE-3 satellite and the HELIOS-2 solar probe. Both instruments observe in the frequency range from 30 kHz to a 1 MHz and both are equipped with dipole antennas located in the vehicle spin plane. ISEE-3 also has a dipole along the spin axis and the signals from the two ISEE-3 antennas are combined to give the aximuth and elevation angles of the radio source. Triangulation between HELIOS-2 and ISEE-3 provides the additional observation necessary to determine uniquely the position of the radio source in space at each observing frequency.
Neutron star magnetic fields may have polar caps (PC) that are offset from the dipole axis, through field-line sweepback near the light cylinder or non-symmetric currents within the star. The effects of such offsets on electron-positron pair cascades are investigated, using simple models of dipole magnetic fields with small distortions that shift the PCs by different amounts or directions. Using a Monte Carlo pair cascade simulation, we explore the changes in the pair spectrum, multiplicity and energy flux across the PC, as well as the trends in pair flux and pair energy flux with spin-down luminosity, L(sub sd). We also give an estimate of the distribution of heating flux from returning positrons on the PC for different offsets. We find that even modest offsets can produce significant increases in pair multiplicity, especially for pulsars that are near or beyond the pair death lines for centered PCs, primarily because of higher accelerating fields. Pair spectra cover several decades in energy, with the spectral range of millisecond pulsars (MSPs) two orders of magnitude higher than for normal pulsars, and PC offsets allow significant extension of all spectra to lower pair energies. We find that the total PC pair luminosity L(sub pair) is proportional to L(sub sd), with L(sub pair) approximates 10(exp -3) L(sub sd) for normal pulsars and L(sub pair) approximates 10(exp -2) L(sub sd) for MSPs. Remarkably, the total PC heating luminosity for even large offsets increases by less than a factor of two, even though the PC area increases by much larger factors, because most of the heating occurs near the magnetic axis.
The Liquid Motion in Rotating Tank Experiment (LME) will investigate and quantify liquid motions occurring in spin-stabilized spacecraft; acquire representative data to validate ground-test scaling procedures; and obtain scientific understanding to formulate better analytical models. LME eliminates the limitations of ground testing. LME design is nearing the end of phase B: the breadboard hardware model has been completed; the load cells have been fabricated and tested; the experiment computer has been flight qualified; and other electronics have been breadboarded. Various aspects of this experiment are presented in viewgraph form.