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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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In-line, quarter-wave thermal short cools the center conductor of the signal-input coaxial transmission line to a cryogenically cooled traveling wave maser. It reduces both the thermal noise contribution of the coaxial line and the heat leak through the center conductor to the maser at 4.4 degrees K.
Radio frequency techniques, microwave thermal noise standards, radio frequency breakdown in coaxial transmission lines, and coaxial cavity radiator development
The design and development of the front-end for a multi-carrier system that allows multiplex signal transmission from satellite-borne transponders is described. Detailed systems analyses provided down-converter specifications. The 12 GHz carrier down-converter uses waveguide, coaxial, and microstrip transmission line elements in its implementation. Mixing is accomplished in a single-ended coaxial mixer employing a field-replacable cartridge style diode.
A mathematical expression was derived describing multipacting and corona effects in a coaxial cavity. Both mechanical and electrical design techniques were investigated to minimize the susceptibility of coaxial cavity to corona and multipacting-type breakdown. To assist in the design of a multicoupler free from corona and multipactor breakdown, a flow chart obtained from the derived mathematical expression is included.
The design and construction of a coaxial transmitter-receiver combination was investigated. Major emphasis was placed on simple permanent optical alignment, transmitter-receiver field of view matching, use of a pulsed gas laser as a transmitter maximum optical efficiency, complete digital control of data acquisition, and optical mount pointing and tracking. Also a means of expanding the coaxial transmitter-receiver concept to allow phased-array lidar, par-lidar was described.
Free field pure jet noise data were taken for a large range of coaxial nozzle configurations. The core nozzles were circular (1 to 4 in. diameter) and plug types. The fan to core area ratio varied from 0.7 to 43.5, while the velocity ratio typically varied from 0 to 1. For most cases the two nozzles were coplanar but large axial extensions of either nozzle were also tested. Correlation of the data resulted in a simple procedure for estimating ambient temperature subsonic coaxial jet noise spectra over a wide range of geometric and flow parameters.
A flow control valve for high temperature fluids is disclosed. The valve is characterized by an all-metal flow control unit including a tubular conduit, terminating in a valve seat, a throttling cone having an internal, truncated conical surface coaxially related to the valve seat and supported for axial motion relative to the seat, and an axially reciprocable, flow-control plug supported in coaxial relation with the cone. The plug is provided with a truncated conical surface configured to be mated with the surface of the throttling cone for regulating a flow of fluid established through the unit and a curved shut-off surface.
A model is formulated for estimating the performance and chamber heat transfer in rocket injectors/chambers operating with gaseous H2-O2 propellants. The model quantifies the combustion performance and chamber heat flux for variables such as chamber length, element type, element area ratio, impingement angle, thrust/element, mixture ratio, moment ratio, element spacing, and physical size. Design equations are given and curves are plotted for evaluation of combustion performance in injectors comprised of F-O-F triplet, premix, coaxial and swirl coaxial element types. Curve plots and equations are also included for estimation of the chamber wall heat fluxes generated by these element types.
A magnetic bearing is described which includes a pair of coaxial, toroidal, and permanent magnets having axially directed poles. Like poles of the permanent magnets are adjacent to each other, whereby the permanent magnets have a tendency to be urged apart along the common axis. An electromagnet is wound coaxially with the permanent magnets in such a manner that the poles are axially directed. Between the poles of each permanent magnet there is a low magnetic reluctance circuit including two series air gaps. Between the poles of the electromagnet a low reluctance path including only one air gap of each of the low magnetic reluctance circuits is provided. The low reluctance path for the electromagnet includes a ring axially translatable relative to the permanent magnets. The ring forms opposite faces of the air gaps in the magnetic circuits for each permanent magnet.
Broadband magnetic antenna systems suitable for recording submicrosecond field changes are described, and typical data from distant lightning are presented. Two types of systems are described, one with a high-impedance antenna loop connected to the integrator by a twisted pair of coaxial cables and another with the antenna loop and twisted signal loops formed from a single piece of coaxial cable. Data for correlated magnetic and electric field waveforms from lightning at a distance of 50 to 100 km are presented and are shown to be almost identical.
A coaxial cylinder configuration is used to investigate the effect of corona impulses on the deterioration of electrical insulation. The corona currents flowing through the resistance develop a voltage which is fed to the measuring set-up. The value of this resistance is made equal to the surge impedance of the coaxial cylinder set up to prevent reflections. This instrumentation includes a phase shifter and Schmidt trigger and is designed to sample, measure, and display corona impulses occurring during any predetermined sampling period of a randomly selectable half cycle of the 60 Hz high voltage wave.
A coaxial focused CW scanning laser Doppler velocimeter (SLDV) radar equipment applying heterodyne detection at 10.6 microns can measure intensity fluctuations under field conditions. The set includes a 20 W CO2 laser, a coaxial Cassegrainian telescope, standard heterodyne equipment, and a SAW spectrum analyzer with 100 kHz signal resolution. Operation of the equipment and techniques for taking remote measurements are described briefly. Applications to remote measurements of transverse component of wind speed, as a complement to the traditional Doppler method of determining axial velocity, are under study. SLDV equipment has been used in detection, tracking, and measurements of atmospheric turbulence associated with aircraft wing-tip vortices or with dust devils, and in measurement of general atmospheric wind profiles.
New fabrication method uses annealed-nickel ribbon loop to interface coaxial input (or output) connector to printed-wiring board. Inexpensive ribbon interface cuts vibration-induced failure between coaxial cable and printed-wiring board.
A critique is given of the JANNAF sub-critical propellant injection/combustion process analysis computer models and application of the models to correlation of well documented hot fire engine data bases. These programs are the distributed energy release (DER) model for conventional liquid propellants injectors and the coaxial injection combustion model (CICM) for gaseous annulus/liquid core coaxial injectors. The critique identifies model inconsistencies while the computer analyses provide quantitative data on predictive accuracy. The program is comprised of three tasks: (1) computer program review and operations; (2) analysis and data correlations; and (3) documentation.
Energetic particles can produce interstitial-vacancy pairs in a crystal by knocking the atoms from their normal positions. Detectors are unique among semiconductor devices in depending on very low concentrations of electrically active impurities, and also on efficient transport of holes and electrons over relatively large distances. Because the dense regions of damage produced by energetic particles may result in donors and/or acceptors, and also provide trapping sites for holes and electrons, detectors are very sensitive to radiation damage. In addition to these effects occurring within the detector, radiation may also change the characteristics of the exposed surfaces causing unpredictable effects on the detector leakage current. Radiation-induced surface degradation has rarely, if ever, been observed for germanium detectors. The possibility of minimizing hole trapping in charge collection by the use of a high-purity germanium coaxial detector configured with the p (+) contact on the coaxial periphery is discussed.
The results presented represent the first successful attempt at the measurement of the driving capabilities of coaxial gaseous propellant rocket injectors. The required data have been obtained by employing the modified impedance tube technique with compressed air as the oxidizer and acetylene gas as the fuel. The data describe the frequency dependence of the injector admittances, from which the frequency dependence of the injection response factors can be calculated. The measured injector admittances have been compared with the predictions of the Feiler and Heidmann (1967) analytical model assuming different values for the characteristic combustion time. The values of combustion time which result in a best fit between the measured and predicted data are indicated for different equivalence ratios. It is shown that for the coaxial injector system investigated in this study the characteristic combustion times vary between .7 and 1.2 msec for equivalence ratios in the range of .57 to 1.31. The experimental data clearly show that the tested injector system could indeed drive combustion instabilities over a frequency range that is in qualitative agreement with the predictions of the Feiler and Heidmann model.
It is known that the noise generated by inverted-velocity-profile coaxial (without center plug) and coannular (with center plug) nozzles should be modeled as the combined contributions of various source regions and noise generation mechanisms. In this paper, an empirical noise-prediction model is described which considers the noise generated by two jet-mixing regions and two potential regions of shock/turbulence interaction. Results calculated from the empirical model are compared with model-scale experimental data for static and simulated flight conditions. These comparisons are made for cases where both streams are subsonic, where the outer stream is supersonic with the inner stream subsonic, and where both streams are supersonic. The cases considered cover a range of inner-to-outer-stream area ratios and include both coaxial and coannular nozzles. It is shown that the model gives reasonable predictions of absolute noise spectra and even better predictions of incremental changes.
The paper reviews the techniques of laser and acoustic Doppler measurement of fluid velocities in confined and free flows. The main mathematical relations are presented, and some systems are studied. Resolution properties of coaxial, bistatic, and pulsed CO2 laser Doppler velocimeter systems are compared. Schematics for pulsed and continuous wave acoustic Doppler systems are discussed. Both of these types of systems benefit from using a bistatic configuration instead of a coaxial system. The pulsed systems avoid contamination of source noise by not sampling until after the source noise has passed the receiver. Comparison of wind velocity measured with a pulsed acoustic Doppler and with a boundary layer profile is made.