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Postflight analysis including six degree of freedom trajectory digital simulation of Aerobee 350 sounding rocket behavior under large thrust misalignment
Expressions have been derived and calculations have been made which show that combined effects lead to asymmetric interferograms and reduction in power at zero path difference. Criteria are given for estimating maximum allowable mirror misalignment.
A combination dual-spin gyroscopically stabilized device is described having a spinning rotor and a non-spinning platform. Two substantially lossless mechanical resonators, resonant at the spin frequency, are orthogonally positioned on the platform for compensation for the disturbing torque acting on the platform due to rotor misalignment.
Coupling from the EH(11) fundamental mode of a square, hollow bore waveguide laser to a square electrooptic modulator is treated. The misalignment loss that results from coupling of the laser fundamental mode into higher order modulator modes is calculated. Results are presented for loss from transverse displacement, angular tilt, and axial separation of the two elements. From these results, the alignment tolerances required to minimize loss for an intracavity modulator are found.
The article addresses the problem of assessing the sensitivity of the heat transfer rate of a Space Orbiter windward surface and boundary-layer transition data to surface features, or 'roughness elements', characteristic of randomly misaligned heat shield tiles. Selected heat shield tiles were precision-formed on the surface of a 0.0175-scale Orbiter model. Selective electroless plating and selective electrochemical etching techniques were employed. Effects of roughness on the location of boundary-layer transition were markedly influenced by the wall-to-total temperature ratios, according to wind-tunnel test results.
The magnitude of the lateral force induced by a roller, misaligned in its direction of travel is considered. Consequences of the induced lateral forces and examples of wheel suspension designs are given.
Application of the endochronic theory of viscoplasticity to creep, creep recovery, and stress relaxation at the small strain and short time range produced the following results: (1) The governing constitutive equations for constant-strain-rate stress-strain behavior, creep, creep recovery, and stress relaxation were derived by imposing appropriate constraints on the general constitutive equation of the endochronic theory. (2) A set of material constants was found which correlate strain-hardening, creep, creep recovery, and stress relaxation. (3) The theory predicts with reasonable accuracy the creep and creep recovery behaviors at short time. (4) The initial strain history prior to the creep stage affects the subsequent creep significantly. (5) A critical stress was established for creep recovery. A computer program, written for the misalignment problem is reported.
Sheet type rectangular 1100-0 aluminum specimens were tested. The creep strain at the geometric centerline of the specimen is different than that at the neutral axis, and decreases with time. The effect of misalignment, which decreases with creep time, is minimized when creep tests are conducted with long pullrods and large initial strain level (high creep stress).
The effect of coning on radial forces in face seals having angular misalignment is analyzed. Both the hydrostatic and hydrodynamic components of the resultant radial force are presented. It is shown that the displacement of the primary seal ring due to the action of radial forces is always in a direction which may cause inward pumping. However, in most cases the radial force is very small.
Annular pressure seals act as powerful hydrostatic bearings and influence the dynamic characteristics of rotating machinery. This work, using the existing concentric seal theories, provides a simple approximate method for calculation of both seal leakage and the dynamic coefficients for short seals with large eccentricity and/or misalignment of the shaft. Rotation and surface roughness effects are included for leakage and dynamic force calculation. The leakage calculations for both laminar and turbulent flow are compared with experimental results. The dynamic coefficients are compared with analytical results. Excellent agreement between the present work and published results have been observed up to the eccentricitiy ratio of 0.8.
High-pressure annular seal leakage and dynamic coefficients vary with eccentricity and misalignment. Recent seal leakage data with both concentric and fully eccentric alignments support the seal leakage model with surface roughness and eccentricity effects included. In this paper, the seal dynamic coefficient calculation has been generalized and allows direct calculation of the seal dynamic coefficients at any circumferential location. The generalized solution agrees with the results obtained by using the calculated values of an earlier paper and performing a coordinate transformation. The analysis results coincide with the measured data in showing that the stiffness and damping matrices of seal coefficients are not skew symmetric, and the main diagonal seal coefficients are not equal. The measured direct stiffnesses were found higher than predicted by the concentric seal theory, but this may be explained by the presence of eccentricity in the test operating mode.
Effects of lidar telescope overlap function modeling on the accuracy of aerosol backscatter measurements are discussed. The treatment pertains primarily to a lidar arrangement which combines high sensitivity and a large degree of geometrical signal compression but places stringent requirements on the accuracy of the overlap function modeling - coherent IR lidar with noncoaxial (side-by-side) transmit and receive telescopes. A model is presented which includes an unstable resonator transmitter and accommodates both coaxial and noncoaxial arrangements, and comparison is made to experimental results including effects of misalignment.
Optoelectronic shaft-angle encoder measures angle of rotation of shaft with high precision while minimizing effects of eccentricity and other misalignments. Grooves on disk serve as reference marks to locate reading heads and measure increments of rotation of disk. Shaft-angle encoder, resembling optical compact-disk drive, includes two tracking heads illuminating grooves on disk and measures reflections from them.
Conceptual docking system absorbs kinetic energy along each of three orthogonal directions. Accommodates large misalignments between docking objects. Lightweight system consists of probe on one of two docking objects and drogue on other object. Probe contains latching mechanism; pitch, roll, and yaw dampers; and centering and rigidizing mechanisms. Three eddy-current dampers absorb energy of motion along orthogonal directions, bringing docking objects to smooth stop. Conceived for docking Space Shuttle in Space Station, system useful in other applications in which large moving object must be aligned with and joined to another - such as, cranes, robots, and fuel or material-loading lines.
Observations indicate that the rotation and minor axes in elliptical galaxies are usually well aligned. However, computer models of dissipationless mergers of pairs of disk galaxies have failed to establish such a correlation, implying that most ellipticals probably did not originate in this manner. Here we consider remnants produced from repeated merging in small groups of a half-dozen or so disk galaxies and find that the internal kinematics of such objects are more representative of actual elliptical galaxies. Although our coverage of parameter space is not complete, the remnants produced in our simulations invariably possess small kinematic misalignments. These results suggest that the majority of elliptical galaxies have had evolutionary histories more complex than those envisaged by simple merger hypotheses.
Misalignment accommodating connector assembly for removably connecting first and second objects which may comprise: a first connector subassembly having an arm member extending therefrom transversely through which is provided a tubular member; a second connector subassembly having a pair of spaced apart arm members each of which is provided with a transversely disposed coaxially aligned semi-cylindrical recess for receiving opposite ends of the first connector tubular member upon lateral insertion of the first connector arm member into the space between the second connector pair of arm members. An axially extendable and contractible fastener subassembly carried by the first connector tubular member is extendable to allow insertion or removal of the first connector arm member into or from the space between the second connector pair of arm members and contractible when the opposite ends of the tubular member are substantially received by the semi-cylindrical recesses of the pair of spaced apart arm members to lock the first and second connector subassemblies together.
The effects of misalignment and unbalance on gas foil bearings are presented. The future of U.S. space exploration includes plans to conduct science missions aboard space vehicles, return humans to the Moon, and place humans on Mars. All of these endeavors are of long duration, and require high amounts of electrical power for propulsion, life support, mission operations, etc. One potential source of electrical power of sufficient magnitude and duration is a nuclear-fission-based system. The system architecture would consist of a nuclear reactor heat source with the resulting thermal energy converted to electrical energy through a dynamic power conversion and heat rejection system. Various types of power conversion systems can be utilized, but the Closed Brayton Cycle (CBC) turboalternator is one of the leading candidates. In the CBC, an inert gas heated by the reactor drives a turboalternator, rejects excess heat to space through a heat exchanger, and returns to the reactor in a closed loop configuration. The use of the CBC for space power and propulsion is described in more detail in the literature (Mason, 2003). In the CBC system just described, the process fluid is a high pressure inert gas such as argon, krypton, or a helium-xenon mixture. Due to the closed loop nature of the system and the associated potential for damage to components in the system, contamination of the working fluid is intolerable. Since a potential source of contamination is the lubricant used in conventional turbomachinery bearings, Gas Foil Bearings (GFB) have high potential for the rotor support system. GFBs are compliant, hydrodynamic journal and thrust bearings that use a gas, such as the CBC working fluid, as their lubricant. Thus, GFBs eliminate the possibility of contamination due to lubricant leaks into the closed loop system. Gas foil bearings are currently used in many commercial applications, both terrestrial and aerospace. Aircraft Air Cycle Machines (ACMs) and ground-based microturbines have demonstrated histories of successful long-term operation using GFBs (Heshmat et al., 2000). Small aircraft propulsion engines, helicopter gas turbines, and high-speed electric motors are potential future applications.
We presented photometric and spectroscopic observations of the 2009 February 2 transit of the exoplanet XO-3b. The new data showed that the planetary orbital axis and stellar rotation axis are misaligned, as reported earlier by Hebrard and coworkers. XO-3b was the first exoplanet known to have a highly inclined orbit relative to the equatorial plane of its parent star, and as such it may fulfill the predictions of some scenarios for the migration of massive planets into close-in orbits.