A precision dc potentiometer microwave insertion loss test set.
Precision DC potentiometer microwave test set for coaxial or waveguide insertion loss measurement
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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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Dielectric properties of reactively sputtered films of aluminum nitride.
Resistivity, capacitance and dielectric loss measurements for diode reactive sputtering grown AlN films and film sandwich structures of Ta, Au and Al films
Francombe, M. H.↗
Microwave cryogenic thermal-noise standards
Field operational waveguide noise standard with nominal noise temperature of 78.09 plus/minus 0.12 deg K is calibrated more precisely than before. Calibration technique applies to various disciplines such as microwave radiometry, antenna temperature and loss measurement, and low-noise amplifier performance evaluation.
Stelzried, C. T.↗
Measurement of the effective electron loss rates in the D region during polar cap absorption events
Day and nighttime effective electron loss rate measurement in D region during polar cap absorption events, using rocket-borne spectrometers and Faraday rotation
Adams, G. W.↗
Experimental load capacity and power loss of herringbone grooved gas lubricated journal bearings
Herringbone grooved gas lubricated journal bearing load capacity, attitude angle and power loss measurements
Anderson, W. J.↗
Error analysis for Mariner Venus/Mercury 1973 conducted at the JPL Mesa west antenna range
Theoretical analysis and experimental data are combined to yield the errors to be used with antenna gain, antenna patterns, and RF cable insertion loss measurements for the Mariner Venus-Mercury 1973 Flight Project. These errors apply to measurements conducted at the JPL Mesa, West Antenna Range, on the high gain antenna, low gain antenna, and RF coaxial cables.
Vincent, N. L.↗
Artificial thickening of transonic boundary layers
A wind-tunnel experiment was performed to examine the effect of turbulence enhancers on the growth of a flat-plate turbulent boundary layer. The free-stream Mach number was varied from 0.6 to 0.9 with unit Reynolds numbers of 6.56 million/m and 13.12 million/m. Several configurations of high-drag objects were mounted near the leading edge of a long flat plate to introduce momentum losses. Measurements of both mean and time-variable flow parameters were made at downstream locations to quantify the influence of the turbulence enhancers. A configuration consisting of two rows of alternately spaced, vertical, 0.317-cm-diameter cylinders of 16 and 12 diameters length produced 1/9to 1/7-power velocity profiles. Unsteady total-temperature and static-pressure profiles were found to be similar to natural turbulent boundary-layer profiles. The techniques presented can be useful whenever thick turbulent boundary layers are required, but the natural growth of the layer is limited by the test facility.
Otten, L. J.↗
Global enclosure fire modeling with applications
A brief review of LERC (Limiting Energy Release Criteria) is presented. Application of LERC to JSC/Boeing ignition source full-scale tests and to JSC/Dacfir math-model validation tests is outlined. It is concluded that: (1) a complete LERC application to the JSC/Boeing tests verifies the fuel load criterion as the limiting constraint; (2) the variability of magnitude and form of the results of repeated tests with and without small variations in parameters emphasizes the significance of the local flow, species concentration, and heat transfer distribution; and (3) weight loss measurements of recent JSC tests show consistent results with prior methods, fuel load constrained.
Stuart, J. W.↗
Silicone modified resins for graphite fiber laminates
The development of silicon modified resins for graphite fiber laminates which will prevent the dispersal of graphite fibers when the composites are burned is discussed. Eighty-five silicone modified resins were synthesized and evaluated including unsaturated polyesters, thermosetting methacrylates, epoxies, polyimides, and phenolics. Neat resins were judged in terms of Si content, homogeneity, hardness, Char formation, and thermal stability. Char formation was estimated by thermogravimetry to 1,000 C in air and in N2. Thermal stability was evaluated by isothermal weight loss measurements for 200 hrs in air at three temperatures. Four silicone modified epoxies were selected for evaluation in unidirectional filament wound graphite laminates. Neat samples of these resins had 1,000 C char residues of 25 to 50%. The highest flexural values measured for the laminates were a strength of 140 kpsi and a modulus of 10 Mpsi. The highest interlaminar shear strength was 5.3 kpsi.
Frost, L. W.↗
Comparison of several inflow control devices for flight simulation of fan tone noise using a JT15D-1 engine
To enable accurate simulation of in-flight fan tone noise during ground static tests, four devices intended to reduce inflow disturbances and turbulence were tested with a JT15D-1 turbofan engine. These inflow control devices (ICD's) consisted of honeycomb/screen structures mounted over the engine inlet. The ICD's ranged from 1.6 to 4 fan diameters in size, and differed in shape and fabrication method. All the ICD's significantly reduced the BPF tone in the far-field directivity patterns, but the smallest ICD's apparently introduced propagating modes which could be recognized by additional lobes in the speeds; at supersonic fan tip speed the smallest ICD's had some measurable loss, but the largest had no loss. Data from a typical transducer show that the unsteady inflow distortion modes (turbulence) were eliminated or significantly reduced when either of the ICD's was installed. However, some steady inflow distortion modes remained.
Mcardle, J. G.↗
A contribution to the knowledge of HMX decomposition and application of results
The decomposition of cyclotramethylenetetranitramine (HMX) in the solid and liquid phase was studied by isothermal and nonisothermal heating at atmospheric pressure. Decomposition rates of solid HMX changed with sample size and gaseous environment. Kinetic parameters were obtained from weight loss measurements in the temperature range 229 C - 269 C. These tests also yielded highly porous solid residues. Qualitative aspects of solid and liquid phase decomposition of HMX with additives were also investigated in isothermal and nonisothermal tests.
Kraeutle, K. J.↗
An optical model for the microwave properties of sea ice
The complex refractive index of sea ice is modeled and used to predict the microwave signatures of various sea ice types. Results are shown to correspond well with the observed values of the complex index inferred from dielectic constant and dielectric loss measurements performed in the field, and with observed microwave signatures of sea ice. The success of this modeling procedure vis a vis modeling of the dielectric properties of sea ice constituents used earlier by several others is explained. Multiple layer radiative transfer calculations are used to predict the microwave properties of first-year sea ice with and without snow, and multiyear sea ice.
Gloersen, P.↗
Evaluation of candidate stirling engine heater tube alloys at 820 deg and 860 deg C
Seven commercial alloys were evaluated in Stirling simulator materials rigs. Five iron base alloys (N-155, A-286, Incoloy 800, 19-9DL, and 316 stainless steel), one nickel base alloy (Inconel 718), and one cobalt base alloy (HS-188) were tested in the form of thin wall tubing in a diesel fuel fired test rig. Tubes filled with hydrogen or helium at gas pressure of 21.6 MPa and temperatures of 820 and 860 C were endurance tested for 1000 and 535 hours, respectively. Results showed that under these conditions hydrogen permeated rapidly through the tube walls, thus requiring refilling during each five hour cycle. Helium was readily contained, exhibiting no measurable loss by permeation. Helium filled tubes tested at 860 C all exhibited creep-rupture failures within the 535 hour endurance test. Subsequent tensile test evaluation after removal from the rig indicated reduced room temperature ductility for some hydrogen-filled tubes compared to helium-filled tubes, suggesting possible hydrogen embrittlement in these alloys.
Misencik, J. A.↗
Design and performance of resonant-cavity parallel baffles for duct silencing
Resonant-cavity parallel baffles, either empty or with a thin absorbent lining, have been investigated as an alternative to fiberglass-filled baffles commonly used to control noise emission from large ducts. A method for predicting silencer attenuation is described, and it is shown that the new type of baffle is characterized by an acoustic performance similar to that of fibrous baffles, while being virtually immune to such problems as clogging, erosion, or settling. The emphasis of the study is on insertion loss measurements in a 7 by 10 ft wind tunnel.
Soderman, P. T.↗
Losses in chopper-controlled DC series motors
Motors for electric vehicle (EV) applications must have different features than dc motors designed for industrial applications. The EV motor application is characterized by the following requirements: (1) the need for highest possible efficiency from light load to overload, for maximum EV range, (2) large short time overload capability (The ratio of peak to average power varies from 5/1 in heavy city traffic to 3/1 in suburban driving situations) and (3) operation from power supply voltage levels of 84 to 144 volts (probably 120 volts maximum). A test facility utilizing a dc generator as a substitute for a battery pack was designed and utilized. Criteria for the design of such a facility are presented. Two motors, differing in design detail, commercially available for EV use were tested. Losses measured are discussed, as are waves forms and their harmonic content, the measurements of resistance and inductance, EV motor/chopper application criteria, and motor design considerations.
Hamilton, H. B.↗
Development of the design concepts for a medium-scale wind tunnel magnetic suspension system
The magnitude of AC losses from a superconducting coil strongly indicates that the predicted scaling lawa are valid. The stainless steel bands around the test coil were the source of additional helium boiloff due to a transformer action and, hence, caused erroneously high AC loss measurements in the first run. However, removal of these bands for the second run produced data which are consistent with previous results on small scale multifilamentary superconducting coils.
Humphris, R. R.↗
Solid particle impingement erosion characteristics of cylindrical surfaces, pre-existing holes and slits
The erosion characteristics of aluminum cylinders sand-blasted with both spherical and angular erodent particles were studied and compared with results from previously studied flat surfaces. The cylindrical results are discussed with respect to impact conditions. The relationship between erosion rate and pit morphology (width, depth, and width to depth ratio) is established. The aspects of (1) erosion rate versus time curves on cylindrical surfaces; (2) long-term exposures; and (3) erosion rate versus time curves with spherical and angular particles are presented. The erosion morphology and characteristics of aluminum surfaces with pre-existing circular cylindrical and conical holes of different sizes were examined using weight loss measurements, scanning electron microscopy, a profilometer, and a depth gage. The morphological features (radial and concentric rings) are discussed with reference to flat surfaces, and the erosion features with spherical microglass beads. The similarities and differences of erosion and morphological features are highlighted. The erosion versus time curves of various shapes of holes are discussed and are compared with those of a flat surface. The erosion process at slits is considered.
Rao, P. V.↗
Superconducting niobium thin film slow-wave structures
A superconducting comb structure as a slow-wave element in a traveling-wave maser will significantly improve maser noise temperature and gain by reducing the insertion loss. The results of the insertion loss measurements of superconducting niobium slow-wave structures subjected to maser operating conditions at X-Band frequencies are presented.
Bautista, J. J.↗