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At least 1,423 records · Page 79
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

The effect of centrifugal distortion on CO2-laser frequencies

Values of the coefficient H for the appropriate carbon-dioxide laser levels are estimated on the basis of theoretical considerations. The values are compared with data obtained by Petersen et al. (1973). It is found that very small perturbations become important as the accuracy of the CO2-laser frequencies increases, especially for lines far away from the band center. Careful experimental frequency measurements are mandatory in the high J region if an accuracy of the order of 10 kHz is desired.

Menzies, R. T.↗
NASA NTRS1974

Interaction of gases with ablative composites. I - Ar, CO2, and N2

The sorption of argon, carbon dioxide, and nitrogen on two heat shield composites (SLA-561 and SLA-561V) and on the SLA components was measured over the pressure range of 0.001 to 760 torr and in the temperature range of 30 to 50 C. The sorption of the gases by both the composites and the components varied directly with pressure. The sorption of CO2 by the phenolic spheres and the silicone elastomer and of Ar by the silicone elastomer varied inversely with temperature. The mechanism involved in the gas sorption was primarily absorption.

King, C. A.↗
NASA NTRS1974

Measurements of small signal absorption at high temperature for the 001-100 band of CO2

In the experiments an absorption cell was irradiated by a polarized CW CO2-N2-He laser. By changing the length of the laser cavity, it was possible to obtain stable oscillations on the five lines P12 through P20 in the 10.4-micron band. The power output was slightly under 10 W. Intensity measurements of the incident and the transmitted beam were conducted when the cell was filled with a nonabsorbing calibrating gas (nitrogen) and with the test gas (carbon dioxide). Data for the absorption coefficient in the temperature range from 300 K to about 600 K are presented in graphs.

Leonard, R. L.↗
NASA NTRS1974

Quasi-one-dimensional solution for the power of CO2 gasdynamic lasers

A theory has been developed for calculating the laser power of CO2 gasdynamic lasers. A three-mode vibrational gas model was assumed, and the coupled rate and one-dimensional conservation equations were solved by the time-dependent technique. The results were compared with experimental data, and the agreement was good.

Lee, G.↗
NASA NTRS1974

Passively cooled glass CO2 laser tubes for severe environments

The objective of this effort was to design a glass CO2 laser tube that could survive the Titan 3 C launch environment and at the same time provide adequate thermal conductivity to maintain the wall of the laser tube below approximately equal to 50 C for efficient lasing. The approach that was taken to satisfy these requirements was to pot the tube in an aluminum heat sink using a space qualified polyurethane potting material. Two configurations of the laser tube successfully passed the complete Titan 3 C qualification level sine and random vibration specification and satisfied the thermal requirements. Fabrication details and test results are presented that indicate this could be a practical solution for laser tubes used in a severe environment and where flowing coolants are impractical or undesirable.

Walker, H. E.↗
NASA NTRS1975

CO2 laser ranging systems study

The conceptual design and error performance of a CO2 laser ranging system are analyzed. Ranging signal and subsystem processing alternatives are identified, and their comprehensive evaluation yields preferred candidate solutions which are analyzed to derive range and range rate error contributions. The performance results are presented in the form of extensive tables and figures which identify the ranging accuracy compromises as a function of the key system design parameters and subsystem performance indexes. The ranging errors obtained are noted to be within the high accuracy requirements of existing NASA/GSFC missions with a proper system design.

Filippi, C. A.↗
NASA NTRS1975

Spaceborne CO2 laser communications systems

Projections of the growth of earth-sensing systems for the latter half of the 1980's show a data transmission requirement of 300 Mbps and above. Mission constraints and objectives lead to the conclusion that the most efficient technique to return the data from the sensing satellite to a ground station is through a geosynchronous data relay satellite. Of the two links that are involved (sensing satellite to relay satellite and relay satellite to ground), a laser system is most attractive for the space-to-space link. The development of CO2 laser systems for space-to-space applications is discussed with the completion of a 300 Mpbs data relay receiver and its modification into a transceiver. The technology and state-of-the-art of such systems are described in detail.

Mcelroy, J. H.↗
NASA NTRS1975

Bosch CO2 Reduction System Development

Refinements in the design of a Bosch CO2 reduction unit for spacecraft O2 production are described. Sealing of the vacuum insulation jacket was simplified so that high vacuum and high insulation performance are easily maintained. The device includes a relatively simple concentric shell recuperative heat exchanger which operates at approximately 95% temperature effectiveness and helps lower power consumption. The influence of reactor temperature, pressure, and recycle gas composition on power consumption was investigated. In general, precise control is not required since power consumption is not very sensitive to moderate variations of these parameters near their optimum values. There are two process rate control modes which match flow rate to process demand. Catalyst conditioning, support, and packing pattern developments assure consistent starts, reduced energy consumption, and extended cartridge life. Operation levels for four or five men were maintained with overall power input values of 50 to 60 watts per man.

Holmes, R. F.↗
NASA NTRS1975

The CO2 gasdynamic laser as a high-intensity radiation facility

The basic theory of CO2 gasdynamic lasers is discussed and related to the design of the Ames laser, which is described in detail. Results of the experimental calibration of the laser are reported and compared with theoretical predictions, and the agreement is excellent. Finally, several applications of the laser as a radiation source for materials testing, both with and without air flow, are described.

Lundell, J. H.↗
NASA NTRS1975

Simulation of planetary entry radiative heating with a CO2 gasdynamic laser

Heating encountered during entry into the atmospheres of Jupiter, Saturn, and Uranus is described, followed by a discussion of the use of a CO2 gasdynamic laser to simulate the radiative component of the heating. Operation and performance of the laser is briefly described. Finally, results of laser tests of some candidate heat-shield materials are presented.

Lundell, J. H.↗
NASA NTRS1975

An experimental study of ultraviolet radiation behind incident normal shock waves in CO2 at Venusian entry speeds

Radiation intensity profiles behind incident normal shock waves in pure CO2 have been measured spectroscopically in the Langley Arc-Driven Shock Tube. These profiles, which were obtained for shock velocities between 9 and 13 km/sec and ambient densities corresponding to Venus altitudes between 100 and 80 km, were measured in the vacuum ultraviolet regime. Wavelengths of 127.7, 158.0, 177.5, and 195.0 nm were monitored simultaneously using a four-channel vacuum spectrograph equipped with sodium-salicylate-coated photomultipliers, thereby including the CO(4+) band system which is the most prominent radiator. Measured nonequilibrium overshoots are modeled to provide a means of estimating the effect of nonequilibrium radiation heating to the stagnation region of proposed aero-shells for Venusian entry. These results indicate a significant increase in radiative heating due to nonequilibrium effects. The measurements are believed to represent the most accurate data available on the effect of nonequilibrium radiative heat transfer for Venus entry. This accuracy is primarily due to improved spectrographic instrumentation, which is discussed in some detail regarding its application in related studies.

Nealy, J. E.↗
NASA NTRS1976

Bosch CO2 Reduction System Development

Development of a Bosch process CO2 reduction unit was continued, and, by means of hardware modifications, the performance was substantially improved. Benefits of the hardware upgrading were demonstrated by extensive unit operation and data acquisition in the laboratory. This work was accomplished on a cold seal configuration of the Bosch unit.

Holmes, R. F.↗
NASA NTRS1975

System measurements of a CO2 laser communications link

Measurements were made under simulated operating conditions to establish the capability of a CO2 laser transmitting heterodyne receiver link to acquire weak laser transmitter beams and maintain spatial tracking during communications. For the case of a synchronous satellite-to-earth station link, analysis and laboratory measurements indicate that the infrared heterodyne receiver subsystem is capable of performing the acquisition, acquisition confirm, and spatial tracking functions at IF signal-to-noise ratio of -17 dB. For the case of a low-altitude satellite-to-earth station link, the laser transmit signal is Doppler-shifted due to the difference in relative velocity of the two stations. The resultant Doppler frequency shift varies with time and must be spectrally acquired and tracked.

Peyton, B. J.↗
NASA NTRS1976

Waveguide CO2 laser gain - Dependence on gas kinetic and discharge properties

A simple rate-equation approach is used to examine the gas-kinetic and discharge properties of waveguide CO2 lasers. The dependence of the population inversion and laser small-signal gain on gas pressure, gas mixture, pumping rate (discharge current), tube bore diameter, and wall temperature is calculated along with the dependence of laser tunability on the gas-kinetic properties and cavity losses. It is found that for low-loss cavities, the laser tunability may substantially exceed the molecular full width at half-maximum. Furthermore, the more helium-rich gas mixtures give greater tunability when cavity losses are small, and less tunability when cavity losses are large. By contrast with conventional lasers, the waveguide-laser transition is homogeneously broadened. Thus, the dependence of gain on gas pressure and other kinetic properties differs substantially from that predicted by scaling results from conventional low-pressure lasers.

Cohen, S. C.↗
NASA NTRS1976

Scattering of high-velocity Ar atoms by CO2, OCS, and CS2

Fast Ar beams have been scattered by room-temperature CO2, OCS, and CS2 to obtain average atom-molecule potentials. The results are consistent with other scattering measurements on similar systems, and are also in excellent agreement with available theoretical calculations based on an electron-gas model. Decomposition of the atom-molecule potentials into constituent atom-atom potentials shows that such a representation can be utilized with fair accuracy but that a definite discrepancy exists.

Amdur, I.↗
NASA NTRS1975

Spaceborne CO2 laser communications systems

Projections of the growth of earth-sensing systems for the latter half of the 1980's show a data transmission requirement of 300 Mbps and above. Mission constraints and objectives lead to the conclusion that the most efficient technique to return the data from the sensing satellite to a ground station is through a geosynchronous data relay satellite. Of the two links that are involved (sensing satellite to relay satellite and relay satellite to ground), a laser system is most attractive for the space-to-space link. During 1975 a major step toward the development of CO2 laser systems for space-to-space applications is being completed. This step is the completion of a 300 Mbps data relay receiver and its modification into a transceiver. The technology and state-of-the-art of such systems are described in detail in this paper.

Mcelroy, J. H.↗
NASA NTRS1975

Aircraft wake vortex velocity measurements using a scanning CO2 laser Doppler velocimeter

A CO2 laser Doppler velocimeter was employed in the study of pairs of counterrotating vortices trailing aircraft in an airport air space. A laser positioned on an extended runway centerline scans a vertical plane perpendicular to the centerline. Vortex location, measurement of vortex transport, and measurement of the properties of aircraft wake vortex flow fields are achieved via spectral analysis of the data. Highest amplitude in the spectrum, the associated maximum velocity, the highest velocity above the amplitude threshold, and the total number of frequency (velocity) cells above thresholds are studied as parameters in analysis of the vortex-associated flow field. The profile of the radial variation of tangential velocity is studied, and two special problems are examined: location of the vortex center and error introduced by crosswind.

Dimarzio, C. A.↗
NASA NTRS1977

Regenerable device for scrubbing breathable air of CO2 and moisture without special heat exchanger equipment

The device concerns the circulation of cabin air through canisters which absorb and adsorb carbon dioxide, together with excess moisture, and return the scrubbed air to the cabin for recirculation. A coating on an inert substrate in granular form absorbs and adsorbs the impurities at standard temperatures and pressures, but desorbs such impurities at low pressures (vacuum) and standard temperatures. This fact is exploited by making the device in a stack of cells consisting of layers or cells which are isolated from one another flow-wise and are connected to separate manifolds and valving systems into two separate subsets. A first subset may be connected for the flow breathable air therethrough until the polyethyleneimine of its cells is saturated with CO2 and H2O. During the same period the second subset of cells is manifolded to a vacuum source.

Tepper, E. H.↗