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The performance of laser glazed zirconia (containing 8 wt% Y2O3) TBC's was evaluated in burner rig cyclic oxidation tests at 1000 and 1050 C. It was found that the cycle duration has no effect on life of TBC's and that the increase in thickness of the glazed layer caused a slight reduction in life.
Pulsed injection laser radar for rendezvous and docking operations, giving results of test performance
We update the status of a diode-pumped, Nd:YAG oscillator that is the prototype laser for NASA's DESDynI mission. After completing TRL-6 testing, this laser has fired over 5.5 billion shots in lifetesting.
The grainy or speckle phenomenon of laser light is caused by two inherent characteristics of the laser - the coherence and monochromaticity of the radiation. Recent development have shown that this phenomenon can be used to measure minute surface displacements, surface strains, or vibrations of a body. The present paper deals with two techniques employing the speckle effect. One is called speckle beam holographic interferometry, and the other speckle photographic interferometry. A major advantage of the first technique is the elimination of the stringent vibration isolation requirement in existing holographic nondestructive test systems. The advantage of the second technique is that the resulting photographic data are sensitive only to the in-plane components of the surface variations. The basic principles and practical limitations of these techniques are discussed.
Overcoming the low signal-to-noise ratio (SNR) in laser ultrasonic testing of composite materials remains a significant challenge. Current efforts focus on enhancing SNR by inserting more energy into the material through temporal and/or spatial modulation of the laser beam. However, potential SNR improvements through wave convergence and wave energy manipulation have been overlooked. This paper addresses this gap by demonstrating the convergence of different wave types to a designated point and by showing the feasibility of directing absorbed laser energy into a specific wave type through spatial modulation of the laser beam. To achieve this, mathematical expressions for the convergent laser beams are derived. Various laser beam profiles are then introduced to the thermoelastic equations and solved using the finite element method. The sample under investigation is a transversely isotropic unidirectional carbon fiber reinforced plastic, characterized by anisotropic thermal expansion coefficients and thermal conductivities. Results reveal pronounced convergence of the intended wave type at the center due to laser beam shaping. This study showcases the ability to direct absorbed laser energy toward a specific wave type through spatial modulation of the laser beam and highlights the role of material anisotropy in energy focusing.
Two loop heat pipes (LHPs) are to be used for thermal control of the Geoscience Laser Altimeter System (GLAS), planned for flight in 2001. One LHP will be used to transport 100 W from a laser to the radiator, the other will transport 210 W from electronic boxes to the radiator. In order to verify the LHP design for the GLAS application, an LHP Development Model has been fabricated, and ambient and thermal vacuum tested. Two aluminum blocks of 15 kg and 30 kg, respectively, were attached to the LHP to simulate the thermal masses connected to the heat sources. A 20 W starter heater was installed on the evaporator to aid the loop startup. A new concept to thermally couple the vapor and liquid line was also incorporated in the LHP design. Such a thermal coupling would reduce the power requirement on the compensation chamber in order to maintain the loop set point temperature. To avoid freezing of the liquid in the condenser during cold cases, propylene was selected as the working fluid. The LHP was tested under reflux mode and with adverse elevation. Tests conducted included start-up, power cycle, steady state and transient operation during hot and cold cases, and heater power requirements for the set point temperature control of the LHP. Test results showed very successful operation of the LHP under all conditions. The 20 W starter heater proved necessary in order to start the loop when a large thermal mass was attached to the evaporator. The thermal coupling between the liquid line and the vapor line significantly reduced the heater power required for loop temperature control, which was less than 5 watts in all cases, including a cold radiator. The test also demonstrated successful operation with a propylene working fluid, with successful startups with condenser temperatures as low as 100 C. Furthermore, the test demonstrated accurate control of the loop operating temperature within +/- 0.2 C, and a successful shutdown of the loop during the survival mode of operation.
The performance of laser glazed zirconia thermal barrier coatings (TBCs) was evaluated in cyclic oxidation and cyclic corrosion tests. Plasma sprayed zirconia coatings of two thicknesses were partially melted with a CO2 laser. The power density of the focused laser beam was varied from 35 to 75 W/sq mm, while the scanning speed was about 80 cm per minute. In cyclic oxidation tests, the specimens were heated in a burner rig for 6 minutes and cooled for 3 minutes. It is indicated that the laser treated samples have the same life as the untreated ones. However, in corrosion tests, in which the burner rig flame contained 100 PPM sodium fuel equivalent, the laser treated samples exhibit nearly a fourfold life improvement over that of the reference samples vary. In both tests, the lives of the samples inversely with the thickness of the laser melted layer of zirconia.
The paper describes the use of dynamic methods of laser ranging of a low altitude satellite along with proposed experiments involving both dynamic and geodetic methods of laser ranging of the Lageos satellite. Particular attention is given to the testing of laser ranging techniques across the San Andreas Fault in California where it is hoped that plate motion will be observable after several years of measurements.
Laser velocimetry applications to wind tunnels are highlighted. The following are covered: investigation of the flow within a metalorganic chemical vapor deposition reactor; helicopter flow investigations in the 4 by 7 m low speed wind tunnel; boundary layer measurements in a supersonic flow using a laser transit anemometer; basic aerodynamic research tunnel. The future of wind tunnel testing with laser velocimetry.
The modifications of a flexible rotor system for two-plane laser balancing is described. Experimental testing of the laser material removal method for balancing through the first bending critical speed was demonstrated. The test rig, optical configuration, and a neodymium glass laser system were assembled and calibrated for static and rotating material removal rates. The laser control computer program was combined with the influence coefficient balancing process, resulting in a completely automated data acquisition, laser, and balancing system. The laser system rotor was balanced through the first bending critical speed using the laser material removal procedure to apply trial weights and correction weights without stopping the rotor.
The Demonstration Model (DM) Loop Heat Pipe (LHP) was tested at Goddard Space Flight Center (GSFC) during September and October, 1999. The LHP system was placed in the Dynavac 36 in. chamber in Building 4. The test lasted for about 6 weeks. The LHP was built, designed, and manufactured at Dynatherm Corporation, Inc. In Hunt Valley, MD according to GSFC specifications. The purpose of the test was to evaluate the performance of a propylene LHP for the Geoscience Laser Altimetry System (GLAS) instrument application.
Performance tests for ablative materials subjected to high intensity carbon dioxide laser radiation
A Laser Altimeter and Mapping Camera System was included in the Apollo Lunar Orbital Experiment Missions. The backup system, never used in the Apollo Program, is available for use in the Lidar Test Experiments on the STS Orbital Flight Tests 2 and 4. Studies were performed to assess the problem associated with installation and operation of the Mapping Camera System in the STS. They were conducted on the photographic capabilities of the Mapping Camera System, its mechanical and electrical interface with the STS, documentation, operation and survivability in the expected environments, ground support equipment, test and field support.
The design, fabrication, testing and delivery of an optical modulator which will operate with a mode-locked Nd:YAG laser at 1.06 micrometers were performed. The system transfers data at a nominal rate of 400 Mbps. This wideband laser modulator can transmit either Pulse Gated Binary Modulation (PGBM) or Pulse Polarization Binary Modulation (PPBM) formats. The laser beam enters the modulator and passes through both crystals; approximately 1% of the transmitted beam is split from the main beam and analyzed for the AEC signal; the remaining part of the beam exits the modulator. The delivered modulator when initially aligned and integrated with laser and electronics performed very well. The optical transmission was 69.5%. The static extinction ratio was 69:1. A 1000 hour life test was conducted with the delivered modulator. A 63 bit pseudorandom code signal was used as a driver input. At the conclusion of the life test the modulator optical transmission was 71.5% and the static extinction ratio 65:1.
The test results of 320 units of a laser initiated microdetonator are summarized. The commercially fabricated units used a lead styphnate/lead azide/HMX (1 mg/13.5 mg) explosive train design contained in a miniature aluminum can that was capped with a glass-metal seal window. The test parameters were the laser energy, temperature, laser pulse duration, laser wavelength and nuclear radiation (5,000,000 rad of 1 MeV gamma rays). The performance parameters were the laser energy for ignition and the actuation response time.
The volume contains recommendations for space-and ground-based programs in gravitational physics, cosmology, and cosmic-ray physics. The section on gravitation examines current and planned experimental tests of general relativity; the theory behind, and search for, gravitational waves, including sensitive laser-interferometric tests and other observations; and advances in gravitation theory (for example, incorporating quantum effects). The section on cosmology deals with the big-bang model, the standard model from elementary-particle theory, the inflationary model of the Universe. Computational needs are presented for both gravitation and cosmology. Finally, cosmic-ray physics theory (nucleosynthesis, acceleration models, high-energy physics) and experiment (ground and spaceborne detectors) are discussed.
Light-assisted microelectronic advanced laser scanner (LAMEALS) is augmented version of microelectronic advanced laser scanner (MEALS) described in article, "Laser Scanner Tests For Single-Event Upsets", (NPO-18216). Only major difference, steady illumination from helium/neon laser, argon-ion laser, and/or other source(s) combined with pulsed dye-laser illumination of MEALS into single illuminating beam.
Verification tests of the Space Shuttle Microwave Scanning Beam Landing System (MSBLS) performed with respect to the Precision Laser Tracking System are reported. MSBLS ground station measurements of the azimuth, elevation and range of a NASA Jetstar aircraft equipped with a laser retroreflector, a MSBLS antenna and commissioning instruments including a MSBLS navigation set of the type installed in the Orbiter, during the performance of radial, orbital and glideslope runs with respect to the ground station were compared with laser ground station measurements of aircraft position. Data obtained from flight testing at Shuttle landing sites reveal MSBLS distance measuring equipment performance to be very good, with elevation errors found at very low elevation angles and azimuth errors as a function of aircraft attitude. The Precision Laser Tracking System has thus proven to be a satisfactory instrument for determining MSBLS performance, and an ideal instrument for its calibration.