Engineering topics

Elleman, D. D.

Publications and source records attributed to Elleman, D. D..

At least 19 records

NASA NTRS1990

Feedback controlled electrostatic and electromagnetic sample positioners

Four different sample positioners are discussed. The four systems share a common operating principle in that the sample positioning is achieved by feedback controlled forces which can be electrostatic, dielectrophoretic, or electromagnetic. The first system is the electrostatic liquid drop positioner which operates at the near ambient position. The second system is the tetrahedral electrostatic positioner which is being developed for the high temperature materials processing in vacuum. The third system is essentially the the same tetrahedral system above except that the position control is achieved by dielectrophoretic forces in the pressurized gas environment. Finally, the feasibility of a feedback controlled electromagnetic positioner is discussed.

Rhim, Won-Kyu↗

NASA NTRS1988

Acoustic containerless experiment system: A non-contact surface tension measurement

The Acoustic Containerless Experiment System (ACES) was flown on STS 41-B in February 1984 and was scheduled to be reflown in 1986. The primary experiment that was to be conducted with the ACES module was the containerless melting and processing of a fluoride glass sample. A second experiment that was to be conducted was the verification of a non-contact surface tension measurement technique using the molten glass sample. The ACES module consisted of a three-axis acoustic positioning module that was inside an electric furnace capable of heating the system above the melting temperature of the sample. The acoustic module is able to hold the sample with acoustic forces in the center of the chamber and, in addition, has the capability of applying a modulating force on the sample along one axis of the chamber so that the molten sample or liquid drop could be driven into one of its normal oscillation modes. The acoustic module could also be adjusted so that it could place a torque on the molten drop and cause the drop to rotate. In the ACES, a modulating frequency was applied to the drop and swept through a range of frequencies that would include the n = 2 mode. A maximum amplitude of the drop oscillation would indicate when resonance was reached and from that data the surface tension could be calculated. For large viscosity samples, a second technique for measuring surface tension was developed. The results of the ACES experiment and some of the problems encountered during the actual flight of the experiment will be discussed.

Elleman, D. D.↗

NASA NTRS1988

The dynamics of free liquid drops

The behavior of rotating and oscillating free liquid drops was studied by many investigators theoretically for many years. More recent numerical treatments have yielded predictions which are yet to be verified experimentally. The purpose is to report the results of laboratory work as well as that of the experiments carried out in space during the flight of Spacelab 3, and to compare it with the existing theoretical studies. Ground-based experiments were attempted as a first approximation to the ideal boundary conditions used by the theoretical treatments by neutralizing the overwhelming effects of the Earth's gravitational field with an outside supporting liquid and with the use of levitation technology. The viscous and inertial loading of such a suspending fluid was found to profoundly effect the results, but the information thus gathered has emphasized the uniqueness of the experimental data obtained in the low-gravity environment of space.

Wang, T. G.↗

NASA NTRS1988

Laser Pyrometer For Spot Temperature Measurements

Laser pyrometer makes temperature map by scanning measuring spot across target. Scanning laser pyrometer passively measures radiation emitted by scanned spot on target and calibrated by similar passive measurement on blackbody of known temperature. Laser beam turned on for active measurements of reflectances of target spot and reflectance standard. From measurements, temperature of target spot inferred. Pyrometer useful for non-contact measurement of temperature distributions in processing of materials.

Elleman, D. D.↗

NASA NTRS1987

Noncontact temperature pattern measuring device

This invention relates to a noncontact imagine pyrometer system for obtaining the true temperature image of a given substance in a contactless fashion without making assumptions about localized emissivity of the substance or the uniformity of the temperature distribution. Such a contactless temperature imaging system has particular application in the study and production of many materials where the physical contact required to make a conventional temperature measurement drastically effects or contaminates the physical process being observed. Two examples where accurate temperature profiles are of critical interest are: (1) the solid-liquid phase change interface in the production of electronic materials and (2) metastable materials in the undercooling region. The apparent novelty resides in the recognition that an active pyrometer system may be advantageously adapted to perform contactless temperature imaging so that an accurate temperature profile can be obtained.

Elleman, D. D.↗

NASA NTRS1987

Dynamics of rotating and oscillating drops

The dynamics of rotation and oscillation is investigated of a freely suspended liquid drop under the influence of surface tension and positioned inside an experimental apparatus by acoustic forces in the low acceleration environment of Spacelab 3. After a drop was observed to be spherical and stably located at the center of the chamber, it was set into rotation or oscillation by acoustic torque or modulated radiation pressure force.

Wang, T. G.↗

NASA NTRS1987

Charged drop levitators and their applications

An account is given of the charged drop levitation characteristics of two different devices: (1) a feedback-controlled electrostatic levitator able to lift a several mm-diameter drop in 1g conditions, which is applicable to drop dynamics, crystal growth, and supercooling/solidification experiments; and (2) a linear quadrupole levitator, whose advantages are demonstrated in light of the results obtained for the charged drop instability experiment. The cause of the premature drop burstings observed is suggested to be an electron avalanche in the surrounding gaseous medium rather than the Rayleigh limit.

Rhim, W. K.↗

NASA NTRS1987

Charged drop dynamics experiment using an electrostatic-acoustic hybrid system

The design and the performance of an electrostatic-acoustic hybrid system and its application to a charge drop rotation experiment are presented. This system can levitate a charged drop electrostatically and induce drop rotation or oscillation by imposing an acoustic torque or an oscillating acoustic pressure. Using this system, the equilibrium shapes and stability of a rotating charged drop were experimentally investigated. A 3 mm size water drop was rotated as a rigid body and its gyrostatic equilibrium shapes were observed. Families of axisymmetric shapes, two-lobed shapes, and eventual fissioning have been observed. With the assumption of 'effective surface tension' in which the surface charge simply modified the surface tension of neutral liquid, the results agree exceptionally well with the Brown and Scriven's (1980) prediction for uncharged drops.

Rhim, W. K.↗

NASA NTRS1986

Storing Chemicals in Packed Spheres

Reactants released by crushing or puncturing. Agglomerated gas-filled spheres hexagonally close packed and sintered or glued together into rods strung together at ends. Rods fed into crushing machine to release material in spheres as needed.

Wang, T. G.↗

NASA NTRS1986

Filter Bed of Packed Spheres

Spheres sized and treated for desired sieve properties. Filter constructed from densely packed spheres restrained by screens. Hollow gas-filled plastic or metal spheres normally used. Manufactured within one percent or better diameter tolerance. Normally, all spheres in filter of same nominal diameter. Filter used as sieve to pass only particles smaller than given size or to retain particles larger than that size. Options available under filter concept make it easy to design for specific applications.

Elleman, D. D.↗

NASA NTRS1986

Pulsed-Corona Electrostatic Charger

Experimental charge-generating apparatus supplies nanocoulomb charges to small objects. Purpose of experiment to develop contactless charger for solid or liquid spheroids in contactless (levitation) processing. Circuit generates high-voltage RF Pulses, applied between two electrodes in each set. Also applies 60 Hz high accelerating voltage between two sets of electrodes. Two sets of electrodes made of conductive paint on acrylic sheets, placed diametrically opposite each other in supporting cylinder.

Rhim, W. K.↗

NASA NTRS1986

Shapes of rotating free drops - Spacelab experimental results

The experimental observation of the behavior of acoustically rotated free drops in the microgravity environment of low earth orbit has yielded the first data which meet the restrictions of existing theoretical treatments. Rotating drops displayed both 'axisymmetric' and 'two-lobed' shapes in the presence and absence of applied torques. Their dimensions and general development confirm the existence of the distinct shape families and the bifurcation point between them. The data also indicate that the secular instability in the axisymmetric family occurs at a lower rotation velocity than predicted

Wang, T. G.↗

NASA NTRS1986

Spacelab 3 drop dynamics experiments

Positioning techniques using the effects of acoustic-radiation pressure were used during the Spacelab 3 flight to carry out classical fluid dynamics experiments on liquid drops freely suspended in microgravity. Quantitative results dealing with the equilibrium shapes of acoustically rotated drops, with the response to the radiation pressure forces, and finally with the experimental measurement of surface tension have been obtained.

Trinh, E. H.↗

NASA NTRS1986

Containerless processing technology

Ground- and space-based containerless processing levitation devices are described. Experiments performed in the MSFC drop tube, the JPL drag-free drop facilities, a single-axis tuned cavity acoustic levitator furnace on TEXUS-I, and a three-axis acoustic levitator and furnace on the STS-11 mission are discussed. Neither acoustic interference nor aerodynamic levitation trials have yielded promising results in sounding rocket and STS based experiments. An electrostatic levitator has furnished a high degree of positioning control with multiple objects in a terrestrial laboratory.

Naumann, R. J.↗

NASA NTRS1986

The Spacelab 2 superfluid helium experiment

An experiment to investigate the properties of superfluid helium in a microgravity environment flew on the Shuttle on the Spacelab 2 mission in July and August of 1985. This paper summarizes the flight experiment and describes the preliminary results. The experiment comprised an investigation of long-wavelength third-sound waves in micron-thick films, a study of the motions of superfluid helium under milli-g and micro-g accelerations, and measurements of the fluctuations in temperature associated with the small motions of the bulk helium. An additional accomplishment was to qualify and characterize a reflyable, space compatible cryostat.

Mason, P. V.↗

NASA NTRS1986

Preliminary results of the Spacelab 2 superfluid helium experiment

An experiment to investigate the properties of superfluid helium in a microgravity environment flew on the Shuttle on the Spacelab 2 mission in July and August of 1985. This paper summarizes the flight experiment and describes some preliminary results. The experiment comprised an investigation of long-wavelength third-sound waves in micron-thick films, a study of the motions of superfluid helium under milli-g and micro-g accelerations, and measurements of the fluctuations in temperature associated with the small motions of the bulk helium. An additional objective was to qualify and characterize a reflyable, space-compatible cryostat.

Mason, P. V.↗

NASA NTRS1985

Closed loop electrostatic levitation system

An electrostatic levitation system is described, which can closely control the position of objects of appreciable size. A plurality of electrodes surround the desired position of an electrostatically charged object, the position of the objects is monitored, and the voltages applied to the electrodes are varied to hold the object at a desired position. In one system, the object is suspended above a plate-like electrode which has a concave upper face to urge the object toward the vertical axis of the curved plate. An upper electrode that is also curved can be positioned above the object, to assure curvature of the field at any height above the lower plate. In another system, four spherical electrodes are positioned at the points of a tetrahedron, and the voltages applied to the electrodes are varied in accordance with the object position as detected by two sensors.

Rhim, W. K.↗

NASA NTRS1985

Electric Field Containerless Processing Technology

The objective of this task is to develop the science and technology base required to design and construct a high temperature electric field positioning module that could be used by materials scientists to conduct containerless science experiments in a low gravity environment. Containerless science modules that employ electric fields to position and manipulate samples offer several advantages over acoustic or electromagnetic systems. The electric field system will operate not only at atmospheric pressures but also in a vacuum, in contrast to the acoustic modules which can only operate in atmosphere where the acoustic forces are sufficient. The electric field technique puts minimum energy into the sample, whereas the electromagnetic system can deposit energy into the sample through eddy current heat as well as physical mixing in the sample. Two types of electric field modules have been constructed and tested to date. One employs a charged sample and uses electrostatic forces to position and control the sample. The second type of module induces electrical polarization of the sample and electric field gradients to position and control the sample.

Elleman, D. D.↗