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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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Bit-slippage errors due to onboard tape recording of PCM/FM telemetry data for Apollo Telescope Mount, noting roles of S/N ratio, data characteristics, etc
System prevents wire saw slippage by providing sufficient friction to turn idler spools even when turns of wire on spools do not provide sufficient friction. Low cost system is easily applied to existing equipment.
PCM telemetry bit synchronizer/signal conditioner, discussing bit acquisition, error and slippage rates
Development of mechanical device to reduce possibility of damage to motor driven needle valve is discussed. Mechanical clutch is employed to allow slippage when needle valve reaches limit of travel. Operation of system for various conditions is described.
Load attenuators for the Apollo spacecraft crew couch and its potential applications are described. Energy absorption is achieved through friction and cyclic deformation of material. In one concept, energy absorption is accomplished by rolling a compressed ring of metal between two surfaces. In another concept, energy is absorbed by forcing a plastically deformed washer along a rod. Among the design problems that had to be solved were material selection, fatigue life, ring slippage, lubrication, and friction loading.
A review of user requirements and updated instrumentation plans are presented for the aircraft tracking and guidance facility at NASA Wallops Station. User demand has increased as a result of new flight research programs; however, basic requirements remain the same as originally reported. Instrumentation plans remain essentially the same but with plans for up- and down-link telemetry more firm. With slippages in the laser acquisition schedule, added importance is placed on the FPS-16 radar as the primary tracking device until the laser is available. Limited simulation studies of a particular Kalman-type filter are also presented. These studies simulated the use of the filter in a helicopter guidance loop in a real-time mode. Disadvantages and limitations of this mode of operation are pointed out. Laser eyesafety calculations show that laser tracking of aircraft is readily feasible from the eyesafety viewpoint.
An investigation was conducted to determine the fore-and-aft elastic response characteristics of aircraft tires of bias ply, bias-belted, and radial-belted design. The investigation consisted of: (1)static and rolling tests, (2)a statistical analysis which related the measured tire elastic characteristics to variations in the vertical load, inflation pressure, braking force and/or tire vertical deflection, and (3) a semi-empirical analysis which related the tire elastic behavior to measured wheel slippage during a steady-state braking. The results of this investigation indicate that the bias-belted tire has the largest spring constant value for most loading conditions and the radial-belted tire has the smallest spring constant value.
The mechanical properties of elastomers, including rupture and its time dependence, can be semiquantitatively predicted from nine molecular parameters which are characteristic for a given species, from the initial molecular weight of a sample before cross-linking and from the effective chain concentration (which must still be determined for each vulcanizate). Only two empirical quantities are involved - the Plazek retardation function for entanglement slippage and a related constant which serves to locate this function on the time scale. The theory leads to a new method of estimating fatigue lifetimes from short-time data.
An investigation was conducted to determine the fore-and-aft elastic response characteristics of 34 x 9.9, type VII, 14 ply-rating aircraft tires of bias-ply, bias-belted, and radial-belted design. The investigation consisted of static and rolling tests on dry concrete pavements at the Langley aircraft landing loads and traction facility; statistical techniques which related the measured tire elastic characteristics to variations in the vertical load, inflation pressure, braking force and/or tire vertical deflection; and a semiempirical analysis which related the tire elastic behavior to measured wheel slippage during steady-state braking. The bias-belted tire developed the largest spring constant value for most loading conditions; the radial-belted tire, the smallest. The elastic response of the tire free periphery to static braking included both tread stretch and carcass torsional wind-up about the axle for the bias-ply and bias-belted tires and carcass wind-up alone for the radial-belted tire.
The maximum count rates of energetic particles are observed earlier on the inbound pass and later on the outbound pass than one would expect if the Jovian magnetodisk moved rigidly with the planet. This lead and lag cannot be explained by the observed azimuthal distortion of the Jovian magnetic field alone. A possible explanation is that the foot of a magnetic field line in the ionosphere slips with respect to Jupiter's surface. The rate of slippage and the electric field necessary for this is estimated. The electric field may be as large as 2 V/m in the Jovian polar ionosphere.
The theory of VLF timing from phase measurements is briefly reviewed with attention to both frequency and epoch. Propagational aspects are noted without specific attention to predictional details. Cycle slippage is described. Application of propagation corrections to VLF timing is described, with particular attention to the use of available skywave corrections published for the OMEGA Navigation System.
It is shown that the requirement that a magnetohydrodynamic wave propagate over a distance equal to a large number of wavelengths without substantial attenuation is equivalent to the requirement that the lateral velocity of displacement of the field lines far exceed a characteristic velocity. This latter velocity is the velocity of slippage of the field lines with respect to the medium.
A discrete phase state bit-synchronization loop is proposed for synchronization and detection of a binary nonreturn-to-zero (NRZ) process. The general loop model is developed for 11 and 17 phase states with optional sequential loop filter. Loop performance is considered in terms of the phase error density function, rms phase error, and mean time to bit slippage. It is shown that satisfactory loop performance can be achieved at -3 dB SNR through use of sequential loop filters.
Modified NRZ (non-return-to-zero) code immunizes record and playback systems against dc drift and bit slippage. In order to maximize bit packing density improved code called J-NRZ gives 100 percent NRZ efficiently and solves DC drift problem by adding check bits in specified format when long string is encountered. Remainder of data stream is encoded in NRZ format.
The problem of displaying information generated by sensors attached to the terminal device of a remotely controlled manipulator is considered. The sensors under consideration are proximity, force-torque, tactile and slip-page sensors. The paper describes and evaluates several examples that have been implemented in the JPL teleoperator project using audio and graphic displays of information generated by four proximity sensors attached to a manipulator end effector. Design schemes are also discussed related to the display of information generated by a six-dimensional force-torque sensor, a multipoint proportional tactile sensor, and a directional slippage sensor. The paper concludes with a discussion of future integrated displays of visual (TV) and handbased sensor information.
Proximity, force-torque, touch and slippage sensors developed or applied by the JPL Teleoperator Project for remote manipulator control are described, including sensor data handling by computers for display and control. Examples are quoted showing the significance of these sensors for manual or computer control of manipulators. An interesting example is a proximity sensor system implemented for a four-claw JSC end effector and tested at the Shuttle Manipulator Training Facility of JSC. New sensing concepts aimed at simplifying the implementation of 'Smart Sensors for Smart Hands' in the space environment are discussed.
Two novel analysis techniques have been used to study focal mechanisms of A1 moonquakes, which occur at the most active of the 80 deep-moonquake source regions identified to date. The first is the cross-spectral analysis of matching signal waveforms. Cross phase spectra clearly show relative polarity of signals and give precise time relationships between signals, thus enabling accurate detemination of relative source locations within the source region. The second is the analysis of amplitude ratios, which reveal the patterns of P- and S-wave radiations around the source region. A1 moonquake foci are found to be concentrated in a nearly horizontal planar region less than 1 km in diameter. Their focal mechanism may be described by slippages along a horizontal plane with the slip direction rotating with and predominantly controlled by the shifting tidal stress field. Thus, A1 moonquakes represent a process of simple storage and release of tidal energy with no evidence for a release of accumulated tectonic stress.
Tasks of scaling up the tandem junction cell (TJC) from 2 cm x 2 cm to 6.2 cm and the assembly of several modules using these large area TJC's are described. The scale-up of the TJC was based on using the existing process and doing the necessary design activities to increase the cell area to an acceptably large area. The design was carried out using available device models. The design was verified and sample large area TJCs were fabricated. Mechanical and process problems occurred causing a schedule slippage that resulted in contract expiration before enough large-area TJCs were fabricated to populate the sample tandem junction modules (TJM). A TJM design was carried out in which the module interconnects served to augment the current collecting buses on the cell. No sample TJMs were assembled due to a shortage of large-area TJCs.