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At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Internal upconversion and doubling of an optical parametric oscillator to extend the tuning range.

Efficient extension of the tuning range of a 1.09-1.95-micron parametric oscillator to 0.435-0.975 microns by upconversion and doubling internally to the oscillator cavity is reported. Unlike previously studied external mixing, internal upconversion and doubling yielded uniform powers of 30 and 60 kW, respectively, over the entire extended tuning range with an unfocused 2-mm ruby laser pump beam of 750 kW.-

Campillo, A. J.↗
NASA NTRS1972

Critical configurations of fundamental range networks.

A range network is defined to consist of ground stations and targets where only distances between the two sets of points are observed. Such a network is said to be fundamental when only those six constraints are used that are needed to define the coordinate system for an adjustment. When ground stations or targets have certain configurations, a unique adjustment in terms of coordinates may be impossible, even when the number of observations is sufficient and the coordinate system is uniquely defined. Such configurations, resulting in the singular solutions, are said to be critical. Attention is therefore focused on singular solutions rather than on numerical problems in some ill-conditioned systems of fundamental range networks. The critical configurations are presented in two separate groups. The first deals with ground stations lying all in a plane and the second deals with ground stations generally distributed. The two kinds of problems require different mathematical treatments and lead to quite different conclusions.

Blaha, G.↗
NASA NTRS1973

Orbit determination by range-only data.

The determination of satellite orbits for use in geodesy using range-only data has been examined. A recently developed recursive algorithm for rectification of the nominal orbit after processing each observation has been tested. It is shown that when a synchronous satellite is tracked simultaneously with a subsynchronous geodetic target satellite, the orbits of each may be readily determined by processing the range information. Random data errors and satellite perturbations are included in the examples presented.

Duong, N.↗
NASA NTRS1972

Isotope Brayton electric power system for the 500 to 2500 watt range.

An extensive study was conducted at the Lewis Research Center to evaluate an isotope Brayton electric power system for use in the 500 to 2500 W power range. The study emphasized overall system simplicity in order to reduce parasitic power losses and improve system reliability. The study included detailed parametric cycle analysis, conceptual component designs, and evaluation of system packaging. The study has resulted in the selection of a single-loop system (gas) with six major components including one rotating unit. Calculated net system efficiency varies from 23 to 28% over the power range. The use of the Pu-238 heat source being developed for the Multi-Hundred-Watt Radioisotope Thermoelectric Generator program was assumed.

Macosko, R. P.↗
NASA NTRS1973

The corrugated horn as an antenna range standard.

The corrugated horn is discussed as is a valuable tool for use in microwave pattern ranges. It has the properties of concentrated energy in the main beam, low backlobes, high efficiency, almost monotonic amplitude, and phase radiation patterns which make the corrugated horn useful for a source antenna in a pattern range and also as a possible standard antenna for calibration purposes.

Caldecott, R.↗
NASA NTRS1973

Technique for extending the frequency range of digital dividers

A technique for extending the frequency range of a presettable digital divider is described. The conventional digital divider consists of several counter stages with the count of each stage compared to a preselected number. When the counts for all stages are equal to the preselected numbers, an output pulse is generated and all stages are reset. For high input frequencies, the least significant stage of the divider has to be reset in a very short time. This limits the frequency that can be handled by the conventional digital divider. This invention provides a technique in which the second least significant and higher stages are reset and the least significant stage is permitted to free-run. Hence, the time in which the reset operation can be performed is increased thereby extending the frequency range of the divider.

Long, W. C.↗
NASA NTRS1973

Short range laser obstacle detector

A short range obstacle detector for surface vehicles is described which utilizes an array of laser diodes. The diodes operate one at a time, with one diode for each adjacent azimuth sector. A vibrating mirror a short distance above the surface provides continuous scanning in elevation for all azimuth sectors. A diode laser is synchronized with the vibrating mirror to enable one diode laser to be fired, by pulses from a clock pulse source, a number of times during each elevation scan cycle. The time for a given pulse of light to be reflected from an obstacle and received is detected as a measure of range to the obstacle.

Kuriger, W. L.↗
NASA NTRS1974

Jet noise from co-axial nozzles over a wide range of geometric and flow parameters

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.

Olsen, W.↗
NASA NTRS1974

Proposal to evaluate the use of ERTS-1 imagery in mapping and managing soil and range resources in the Sand Hills region of Nebraska

The author has identified the following significant results. Increase in radiance values is directly related to decrease in vegetative biomass, though not in a linear manner. Should the relationship hold true over an entire growing season, this would allow an extremely rapid evaluation of range condition. Computer access by remote terminal would allow production of this type of range condition evaluation in near real time, which is essential if grazing practice decisions are to be made based on satellite imagery acquisition. Negating the manipulation of photographic products appears to be the logical way to provide satellite imagery data to the user in near real time. There appears to be a direct linear relationship between radiance values of bands 4 and 5 and increase in total inorganic ions (6 ions) of lakes in the Sand hills region. Consistent ion concentration of lakes during the year could allow their radiance values to serve as a means of equating radiance values from image to image.

Drew, J. V.↗
NASA NTRS1974

Forward slanted slot throat stability bypass to increase the stable airflow range of a Mach 2.5 inlet with 60 percent internal contraction

The results of an experimental investigation to increase the stable airflow operating range of a supersonic mixed-compression inlet are presented. Two forward-slanted slot stability-bypass entrance configurations were tested. In terms of diffuser-exit corrected airflow, a large inlet stable airflow range of 18.5 percent was obtained with the superior configuration if a constant pressure was maintained in the bypass plenum. Limited unstart angle-of-attack data are presented.

Shaw, R. J.↗
NASA NTRS1974

Development of acoustically lined ejector technology for multitube jet noise suppressor nozzles by model and engine tests over a wide range of jet pressure ratios and temperatures

An experimental program comprising model nozzle and full-scale engine tests was undertaken to acquire parametric data for acoustically lined ejectors applied to primary jet noise suppression. Ejector lining design technology and acoustical scaling of lined ejector configurations were the major objectives. Ground static tests were run with a J-75 turbojet engine fitted with a 37-tube, area ratio 3.3 suppressor nozzle and two lengths of ejector shroud (L/D = 1 and 2). Seven ejector lining configurations were tested over the engine pressure ratio range of 1.40 to 2.40 with corresponding jet velocities between 305 and 610 M/sec. One-fourth scale model nozzles were tested over a pressure ratio range of 1.40 to 4.0 with jet total temperatures between ambient and 1088 K. Scaling of multielement nozzle ejector configurations was also studied using a single element of the nozzle array with identical ejector lengths and lining materials. Acoustic far field and near field data together with nozzle thrust performance and jet aerodynamic flow profiles are presented.

Atvars, J.↗
NASA NTRS1974

Distributed porous throat stability bypass to increase the stable airflow range of a Mach 2.5 inlet with 60 percent internal contraction

The results of an experimental investigation to increase the stable airflow operating range of a supersonic, mixed-compression inlet with 60-percent internal contraction are presented. Various distributed-porous, throat stability-bypass entrance configurations were tested. In terms of diffuser-exit corrected airflow, a large inlet stable airflow range of about 25 percent was obtained with the optimum configuration if a constant pressure was maintained in the by-pass plenum. The location of the centerbody bleed region had a decided effect on the overall inlet performance. Limited unstart angle-of-attack data are presented.

Shaw, R. J.↗
NASA NTRS1974

Distributed educated throat stability bypass to increase the stable airflow range of a Mach 2.5 inlet with 60-percent internal contraction

The results of an experimental investigation to increase the stable airflow operating range of a supersonic mixed-compression inlet are presented. A distributed educated throat stability-bypass entrance configuration was tested. In terms of diffuser-exit corrected airflow, a large inlet stable airflow range of about 16.1 percent was obtained if a constant pressure was maintained in the bypass plenum. Limited unstart angle of attack data are presented.

Shaw, R. J.↗
NASA NTRS1974

Design of retrodirector arrays for laser ranging of satellites

The radar equation for laser ranging of satellites is described and the effect of the velocity aberration explained. Equations for the cross sections of cube corners and arrays of cube corners are derived. Interference effects on the distribution of the array cross section and upon range error are described. Tolerance requirements for cube corners are briefly outlined.

Minott, P. O.↗
NASA NTRS1974

Lunar laser ranging data deposited in the National Space Science Data Center: Filtered observations for January - June 1972 and unfiltered photon detections for July - December 1972

The documentation to be used in conjunction with the filtered data deposited in the National Space Science Data Center is presented. The data was obtained during laser ranging operations between the McDonald Observatory and Apollo 11, 14, and 15 reflectors for the six months ending June 30, 1972. Unfiltered photon detections for the succeeding six months are also included in the system. Nominal coordinates for the laser ranging equipment are given and the calibration code for filtered data is shown. Data format using the CDC 6600 computer is described.

Mulholland, J. D.↗
NASA NTRS1974

Dynamic techniques for studies of secular variations in position from ranging to satellites

Satellite laser range measurements were applied to the study of latitude variation arising from polar motion, and the solid-earth and ocean tidal distortion of the earth's gravity field. Experiments involving two laser tracking stations were conducted. The relative location of one station with respect to the other was determined by performing simultaneous range measurements to a satellite from two stations several hundred kilometers apart. The application of this technique to the San Andreas Fault Experiment in California is discussed. Future capabilities of spacecraft equipped with laser retroreflectors include: (1) determination of the product of the earth's mass and gravitational constant; (2) measurement of crustal and tectonic motions; (3) determination of the elastic response of the solid-earth tidal forces; (4) measurement of the amplitudes and phase of certain components of the ocean tides; and (5) self-monitoring of the latitude and height variations of the tracking station.

Smith, D. E.↗
NASA NTRS1974

Pressure activated stability-bypass-control valves to increase the stable airflow range of a Mach 2.5 inlet with 40 percent internal contraction

The throat of a Mach 2.5 inlet with a coldpipe termination was fitted with a stability-bypass system. The inlet stable airflow range provided by various stability-bypass entrance configurations in alternate combination with several stability-bypass exit controls was determined for both steady-state conditions and internal transient pulses. Transient results were also obtained for the inlet with a choke point at the diffuser exit. Instart angles of attack were determined for the various stability-bypass entrance configurations. The response of the inlet-coldpipe system to internal and external oscillating disturbances was determined. Poppet valves at the stability-bypass exit provided an inlet stable airflow range of 28 percent or greater at all static and transient conditions.

Mitchell, G. A.↗
NASA NTRS1974

Precision laser range finder system design for Advanced Technology Laboratory applications

Preliminary system design of a pulsed precision ruby laser rangefinder system is presented which has a potential range resolution of 0.4 cm when atmospheric effects are negligible. The system being proposed for flight testing on the advanced technology laboratory (ATL) consists of a modelocked ruby laser transmitter, course and vernier rangefinder receivers, optical beacon retroreflector tracking system, and a network of ATL tracking retroreflectors. Performance calculations indicate that spacecraft to ground ranging accuracies of 1 to 2 cm are possible.

Golden, K. E.↗