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  • 1
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    Large-gap magnetic positioning system having advantageous configuration (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: A magnetic configuration was devised in which the positioned object is maintained in a stable orientation and position on one side of an opaque plane surface entirely by means of magnetic components on the other side of the plane. The system is effective with or without gravity, and can operate in any orientation. In this system, the positioned object need only contain a simple dipole magnet. The positioning components consist of a group of permanent magnets creating a magnetic field configuration which stabilizes the levitated dipole in all but one degree of freedom, and a magnetic position sensing and force feedback system to actively stabilize the object in the one unstable direction. The system utilizes very low power at equilibrium and can maintain gaps of 50 mm.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Langley Research Center, International Symposium on Magnetic Suspension Technology, Part 2; p 941-953
    Format: text
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  • 2
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    Coarse-fine residual gravity cancellation system with magnetic levitation (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Aircraft flight along parabolic trajectories have been proposed and executed in order to achieve low cost, near free fall conditions of moderate duration. This paper describes a six degree of freedom experiment isolation system designed to cancel out residual accelerations due to mechanical vibrations and errors in aircraft trajectory. The isolation system consists of a fine motion magnetic levitator whose stator is transported by a conventional coarse motion stage. The levitator uses wide gap voice coil actuators and has the dual purpose of isolating the experiment platform from aircraft vibrations and actively cancelling residual accelerations through feedback control. The course motion stage tracks the levitated platform in order to keep the levitator's coils centered within their matching magnetic gaps. Aspects of system design, an analysis of the proposed control strategy and simulation results are presented. Feasibility experiments are also discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Langley Research Center, International Symposium on Magnetic Suspension Technology, Part 1; p 473-492
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  • 3
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    Extraterrestrial surface propulsion systems (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Lunar traction systems, Mars oxygen production, and Mars methane engine operation were the three topics studied during 1992. An elastic loop track system for lunar construction operations was redesigned and is being tested. A great deal of work on simulating the lunar environment to facilitate traction testing has been reported. Operation of an oxygen processor under vacuum conditions has been the focus of another design team. They have redesigned the processor facility. This included improved seals and heat shields. Assuming methane and oxygen can be produced from surface resources on Mars, a third design team has addressed the problem of using Mars atmospheric carbon dioxide to control combustion temperatures in an internal combustion engine. That team has identified appropriate tests and instrumentation. They have reported on the test rig that they designed and the computer-based system for acquiring data.
    Keywords: MECHANICAL ENGINEERING
    Type: USRA, Proceedings of the 8th Annual Summer Conference: NASA(USRA Advanced Design Program; p 209-215
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  • 4
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    Linear mass actuator (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A linear mass actuator includes an upper housing and a lower housing connectable to each other and having a central passageway passing axially through a mass that is linearly movable in the central passageway. Rollers mounted in the upper and lower housings in frictional engagement with the mass translate the mass linearly in the central passageway and drive motors operatively coupled to the roller means, for rotating the rollers and driving the mass axially in the central passageway.
    Keywords: MECHANICAL ENGINEERING
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  • 5
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    Bulk YBa2Cu3O(x) superconductors through pressurized partial melt growth processing (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A novel pressurized partial melt growth process has been developed for producing large pieces of bulk Y-Ba-Cu-O superconductors. During long-time partial melt growth stage, an additional driving force for solidification is obtained by using pressurized oxygen gas. The microstructure and superconducting properties of the resulting samples were investigated. It was found that this new technique can eliminate porosity and inhomogeneity, promote large-scale grain-texturing, and improve interdomain coupling as well.
    Keywords: MECHANICAL ENGINEERING
    Type: Journal of Materials Research (ISSN 0884-2914); 7; 808-812
    Format: text
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  • 6
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    The application of linear actuators for telescope pointing control (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A study team at MSFC has conceptually designed two lunar-based telescopes, a 16 m aperture Large Lunar Telescope (LLT) and a 4 m Cluster Telescope Experiment (CTE). The CTE serves as a technology tested for the LLT. The CTE utilizes a hexapod telescope mount to obtain a small gimbal angle that significantly extends the viewing space and observation time from that of a stationary transit telescope. This paper addresses the applicability of six linear actuators to provide limited gimbal rotation of the CTE telescope assembly. Kinematic constraint equations for the hexapod mount have been applied to a six degree-of-freedom rigid body model. Static equilibrium equations have been solved to address configuration design issues, and a feedback tracking control system has been designed and simulated.
    Keywords: MECHANICAL ENGINEERING
    Type: AAS PAPER 91-536 , AAS/AIAA Astrodynamics Conference; Aug 19, 1991 - Aug 22, 1991; Durango, CO; United States
    Format: text
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  • 7
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    Design of a D-Strut and its application results in the JPL, MIT, and LaRC test beds (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: High damping at very low magnitudes of vibration is provided by an 'Arched Flexure' D-Strut. Five of these devices have been incorporated in JPL's CSI truss structure, and five more in MIT's interferometer test bed. Two were also temporarily installed in the LaRC CSI test structure. Damping factors in the 50 percent category are being provided at vibration motions as small as 50 nm. The 'Arched Flexure' used in the D-Strut maximizes the volumetric stiffness parameter relative to its axial stiffness. In turn, this enables high damping factors, even in a very rigid truss structure. This paper includes a presentation and discussion of both element and system test data taken at JPL, LaRC, and MIT. Also provided is a detailed description of the D-Strut, the dynamic model, and several graphs showing design parameter variations that will make it possible to evaluate the D-Strut for other applications.
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA PAPER 92-2274 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 13, 1992 - Apr 15, 1992; Dallas, TX; United States
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  • 8
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    An experimental technique for performing 3-D LDA measurements inside whirling annular seals (1992)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: During the last several years, the Fluid Mechanics Division of the Turbomachinery Laboratory at Texas A&M University has developed a rather unique facility with the experimental capability for measuring the flow field inside journal bearings, labyrinth seals, and annular seals. The facility consists of a specially designed 3-D LDA system which is capable of measuring the instantaneous velocity vector within 0.2 mm of a wall while the laser beams are aligned almost perpendicular to the wall. This capability was required to measure the flow field inside journal bearings, labyrinth seals, and annular seals. A detailed description of this facility along with some representative results obtained for a whirling annular seal are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: International Symposium on Application of Laser Techniques to Fluid Mechanics; Jul 20, 1992 - Jul 23, 1992; Lisbon; Portugal|Compressible and Incompressible Fluid Seals: Influence on Rotordynamic Response and Stability; 7 p
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  • 9
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    Turbulence measurements of high shear flow fields in a turbomachine seal configuration (1992)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The mean velocity and Reynolds stress tensor throughout a whirling annular seal are presented. The data was collected with a three dimensional laser Doppler velocimeter using phase averaging. Two axial flow conditions (Re = 12,000 and 24,000) were studied at one shaft speed (Ta = 6,600). The eccentricity and whirl ratios were 50 and 100 percent, respectively. There is a region of high axial momentum in this region is higher in the low Reynolds number case due to an axial recirculation zone that occurs on the suction side of the rotor at the inlet. The recirculation zone does not occur in the high Reynolds number case. At both Reynolds numbers, there is a recirculation zone on the rotor surface in the pressure side of the inlet. This recirculation zone extends from 20 to 200 degrees rotor zenith in the tangential direction, and is one third of a clearance wide radially. The high Reynolds number recirculation zone is 1.5 mean clearances long, while the low Reynolds number zone extends 2 mean clearances downstream. When compared to previous studies, it is apparent that the tangential momentum is no greater for a seal with whirl than for one without if other parameters are constant. Areas of high tangential momentum occur in the clearance where the axial momentum is low. Average exit plane tangential velocities in the high Reynolds number case are 1.5 times greater than those in the other flow case. These results are in general agreement with predictions made by other investigators.
    Keywords: MECHANICAL ENGINEERING
    Type: 1992 Conference on Advanced Earth-To-Orbit Propulsion Technology; May 19, 1992 - May 21, 1992; Huntsville, AL; United States|Compressible and Incompressible Fluid Seals: Influence on Rotordynamic Response and Stability; 12 p
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  • 10
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    Experimental study of the flow field inside a whirling annular seal (1992)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The flow field inside a whirling annular seal was measured using a 3-D Laser Doppler Anemometer (LDA) system. The seal investigated has a clearance of 1.27 mm, a length of 37.3 mm, and is mounted on a drive shaft with a 50 percent eccentricity ratio. This results in the rotor whirling at the same speed as the shaft rotation (whirl ratio = 1.0). The seal is operated at Reynolds number of 12,000 and a Taylor number of 6,300 (3,600 rpm). The 3-D LDA system is equipped with a rotary encoding system which is used to produce phase averaged measurements of the entire mean velocity vector field and Reynolds stress tensor field from 0.13 mm upstream to 0.13 mm downstream of the seal. The mean velocity field reveals a highly three dimensional flow field with large radial velocities near the inlet of the seal as well as a recirculation zone on the rotor surface. The location of maximum mean axial velocity migrates from the pressure side of the rotor at the inlet to the suction side at turbulence kinetic energy. However, turbulence production and dissipation attain equilibrium fairly quickly with remaining relatively constant over the last half of the seal.
    Keywords: MECHANICAL ENGINEERING
    Type: International Symposium on Transport Phenomena and Dynamics in Rotating Machinery; Apr 05, 1992 - Apr 08, 1992; Honolulu, HI; United States|Compressible and Incompressible Fluid Seals: Influence on Rotordynamic Response and Stability; 11 p
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