Self-steering arrays for satellite applications.
Electronic self-steering techniques applied to satellite communications system with high gain antennas, noting transdirective array and self- phasing array
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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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Systems of self-gravitating particles in general relativity and the concept of an equation of state
Equilibrium configurations of self-gravitating particles systems by self consistent fields method
Bonazzola, S.↗
Self-organizing and learning control systems.
Self organizing and learning control systems, adaptive systems theory and defining self organizing control systems
Barron, R. L.↗
A method for approximating the eigenvalues of non self-adjoint ordinary differential operators
Eigenvalue approximation method for non-self-adjoint operators using Galerkin method for estimating eigenvalue perturbations of self-adjoint operators
Osborn, J. E.↗
Design study of shaft face seal with self-acting lift augmentation. 5: Performance in simulated gas turbine engine operation
The feasibility and the noncontact operation of the self-acting seal was demonstrated over a range of simulated gas turbine engine conditions from 200 to 500 ft/sec sliding speed. Sealed pressure differentials were 50 to 300 psi and sealed temperatures were 150 to 1200 F. Low leakage (about 1/10 that of conventional labyrinth seals) was exhibited in two endurance runs (200 and 338 hr) at 400 ft/sec, 200 psi and 1000 F (gas temperature). For these endurance runs, the self-acting pad wear was less than 3.8 micrometers (0.00015 in.); this low wear was attributed to the noncontact operation of the primary seal. Operating problems identified were fretting wear of the secondary seal and erosion of the primary seal by hard particles.
Ludwig, L. P.↗
Predicting spacecraft self-contamination in space and in a test chamber
The self-contamination of a spacecraft, defined as the return and deposition of outgassed molecules on its critical surfaces, was investigaed. Theoretical relations for the flux, density, and pressure of the emitted gas as a function of altitude, radius, and distance from the spacecraft surface were developed. The flux of these outgassed molecules which return to the emitting surface was also obtained and shown to be dependent on altitude, dimensions, and on the magnitude of outgassing. The rate of condensation and the time for the formation of a monolayer of the returning molecules can be calculated. The self-contamination of a spacecraft undergoing vacuum chamber test was also analyzed and compared to the equivalent parameters for the orbital conditions.
Scialdone, J. J.↗
Fast-acting self-healing metallic fuse.
Description of a fast-acting nonmechanical self-healing mercury fuse capable of protecting a high current circuit or device from overcurrent fault damages. Basically the self-healing fuse consists of two enclosed mercury reservoirs connected by a fine capillary tube filled with mercury that serves as the fusing element. It is pointed out that a better understanding of the energy conversion process involved in the operation of the device could help explore other device configurations (such as a tapering geometry and use of magnetic field to drive the arc into the fuse wall on inductive loads, etc.) and thus extend the range of capabilities for this type of protective device.
Schwartz, F. C.↗
Motivation in vigilance - Effects of self-evaluation and experimenter-controlled feedback.
Vigilance experiments have been performed to study the relative efficiency of feedback operations in enhancing vigilance performance. Two feedback operations were compared - i.e., experimenter-controlled feedback in the form of knowledge of results (KR) regarding response times to signal detections, and subject-controlled feedback in the form of self-evaluation (SE) of response times to signal detections. The subjects responded to the aperiodic offset of a visual signal during a 1-hr vigil. Both feedback operations were found to enhance performance efficiency: subjects in the KR and SE conditions had faster response times than controls receiving no evaluative feedback. Moreover, the data of the KR and SE groups did not differ significantly from each other. The results are discussed in terms of the hypothesis that self-evaluation is a critical factor underlying the incentive value of KR in vigilance tasks.
Warm, J. S.↗
Diffusion in the system K2O-SrO-SiO2. II - Cation self-diffusion coefficients.
The self-diffusion coefficients were measured by introducing a slab of glass previously irradiated in a reactor between two slabs of unirradiated glass. By heating the specimens, etching them sequentially and determining the radioactivity, self-diffusion coefficients for K and Sr were measured. It is pointed out that the results obtained in the investigations appear to support the proposal that the network of the base glass predominantly controls the activation energy for the diffusion of ions.
Varshneya, A. K.↗
A self-supporting strain transducer
Self-contained mechanical measuring system is handmounted by simply compressing installation spring and inserting device into hole of matching size. It is self-aligning as each contact pin maintains constant contact with surface being measured. Strain level is controlled by design to provide for measurements over almost unlimited number of load cycles.
Hoffman, I. S.↗
Self-tuning bandpass filter
An electronic filter is described which simultaneously maintains a constant bandwidth and a constant center frequency gain as the input signal frequency varies, and remains self-tuning to that center frequency over a decade range. The filter utilizes a field effect transistor (FET) as a voltage variable resistance in the bandpass frequency determining circuit. The FET is responsive to a phase detector to achieve self-tuning.
Deboo, G. J.↗
Experimental investigation of resonance self-shielding and the Doppler effect in uranium and tantalum
A series of average transmission and average self-indication ratio measurements were performed in order to investigate the temperature dependence of the resonance self-shielding effect in the unresolved resonance region of depleted uranium and tantalum. The measurements were carried out at 77 K, 295 K and approximately 1000 K with sample thicknesses varying from approximately 0.1 to 1.0 mean free path. The average resonance parameters as well as the temperature dependence were determined by using an analytical model which directly integrates over the resonance parameter distribution functions.
Byoun, T. Y.↗
On self-similar blast waves headed by the Chapman-Jouguet detonation.
Consideration of the whole class of self-similar solutions for blast waves bounded by Chapman-Jouguet detonations that propagate into a uniform, quiescent, zero counterpressure atmosphere of a perfect gas with constant specific heats. Since such conditions can be approached quite closely by some actual chemical systems at NTP, this raises the interesting possibility of the existence of Chapman-Jouguet detonations of variable velocity. The principal virtue of the results presented is, however, more of theoretical significance. They represent the limiting case for all the self-similar blast waves headed by gasdynamic discontinuities associated with a deposition of finite amounts of energy, and they exhibit some unique features owing to the singular nature of the Chapman-Jouguet condition.
Oppenheim, A. K.↗
Temperature-dependent transmission and self-indication measurements upon depleted U in the unresolved region
Neutron transmission and self-indication ratio measurements have been carried out at the RPI LINAC on depleted U up to 100 KeV in order to investigate the temperature dependence of resonance self-shielding. These measurements were performed at three sample temperatures (77 deg k, 295 deg k, and 973 deg k) and with sample thicknesses ranging from 0.0076 to 0.0621 atom/barn. Both stochastic sampling and analytical methods have been used to interpret these data. Average resonance parameters have been obtained and temperature dependence as well as sample thickness dependence of the data have been extensively studied.
Byoun, T. Y.↗
Self-complementarity of messenger RNA's of periodic proteins
It is shown that the mRNA's of three periodic proteins, collagen, keratin and freezing point depressing glycoproteins show a marked degree of self-complementarity. The possible origin of this self-complementarity is discussed.
Ycas, M.↗
A self-reorganizing digital flight control system for aircraft
This paper presents a design method for digital self-reorganizing control systems which is optimally tolerant of failures in aircraft sensors. The functions of this system are accomplished with software instead of the popular and costly technique of hardware duplication. The theoretical development, based on M-ary hypothesis testing, results in a bank of M Kalman filters operating in parallel in the failure detection logic. A moving window of the innovations of each Kalman filter drives the detection logic to decide the failure state of the system. The detection logic also selects the optimal state estimate (for control logic) from the bank of Kalman filters. The design process is applied to the design of a self-reorganizing control system for a current configuration of the space shuttle orbiter at Mach 5 and 120,000 feet. The failure detection capabilities of the system are demonstrated using a real-time simulation of the system with noisy sensors.
Montgomery, R. C.↗
Homogeneity requirements for minimizing self-focusing damage by strong electromagnetic waves
The Rytov approximation for wave propagation in random media is generalized to include the effects of self-focusing. Solutions are obtained which show how the intensity fluctuations, which are either initially present in the wave or which are induced by the random inhomogeneities in the media, grow catastrophically. These solutions may be used to obtain conditions on the homogeneity of the medium, or of the incident beam, for reduction or elimination of catastrophic self-focusing in the medium.
Jokipii, J. R.↗
Development of a six-man, self-contained carbon dioxide collection subsystem for spacecraft application
Life Systems, working with NASA, has developed an electrochemical, six-man, self-contained carbon dioxide concentrator subsystem (CX-6) designed to normally remove 13.2 lb/day of CO2 while maintaining the CO2 partial pressure (pCO2) of the cabin atmosphere at 3 mm Hg or less. The CX-6 was subjected to extensive parametric and endurance testing. The effects of operating conditions on CO2 removal and electrical efficiencies were determined, including effects of hydrogen (H2) flow rate, process airflow rate, pCO2, operating temperature and current density. A total of 209 days of operation was accumulated. The subsystem was designed with self-contained electronic control and monitoring instrumentation. The CX-6 was redesigned and repackaged into the CO2 collection subsystem for the air revitalization group of the space station prototype.
Schubert, F. H.↗