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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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Fiber-optic injection-locked broad-area laser diode features single-mode output via fiber-optic injection and serves as compact, rugged, high-power near-infrared source. Useful in free-space and fiber-optic communication links, as communication-receiver preamplifier, and pump source for solid-state lasers.
Report proposes development of rocket engines burning small grains of solid fuel entrained in gas streams. Main technical discussion in report divided into three parts: established fluidization technology; variety of rockets and rocket engines used by nations around the world; and rocket-engine equation. Discusses significance of specific impulse and ratio between initial and final masses of rocket. Concludes by stating three important reasons to proceed with new development: proposed engines safer; fluidized-solid-fuel injection process increases variety of solid-fuel formulations used; and development of fluidized-solid-fuel injection process provides base of engineering knowledge.
Defect behavior, observed by deep level transient spectroscopy (DLTS), is used to predict carrier removal and the effects of simultaneous electron irradiation and injection annealing of the performance of InP solar cells. For carrier removal, the number of holes trapped per defect is obtained from measurements of both carrier concentrations and defect concentrations during an isochronal anneal. In addition, from kinetic considerations, the behavior of the dominant defect during injection annealing is used to estimate the degradation expected from exposure to the ambient electron environment in geostationary orbit.
A total of 38 hydrogen no-vent fill tests were performed in this test series using various size spray nozzles and a spray bar with different hole sizes in a 5 cubic foot receiver tank. Fill levels of 90 percent by volume or greater were achieved in 26 of the tests while maintaining a receiver tank pressure below 30 psia. Spray nozzles were mounted at the top of the tank, whereas, the spray bar was centered in the tank axially. The spray nozzle no-vent fills demonstrated tank pressure and temperature responses comparable to previous test series. Receiver tank pressure responses for the spray bar configuration were similar to the spray nozzle tests with the pressure initially rising rapidly, then leveling off as vapor condenses onto the discharging liquid streams, and finally ramping up near the end of the test due to ullage compression. Both liquid injection techniques tested were capable of filling the receiver tank to 90 percent under variable test conditions. Comparisons between the spray nozzle and spray bar configurations for well matched test conditions indicate the spray nozzle injection technique is more effective in minimizing the receiving tank pressure throughout a no-vent fill compared to the spray bar under normal gravity conditions.
Because of one-engine-inoperative (OEI) requirements, together with hot-gas reingestion and hot-day, high-altitude take-off situations, power augmentation for multiengine rotorcraft has always been of critical interest. However, power augmentation by using overtemperature at the turbine inlet will shorten turbine life unless a method of limiting thermal and mechanical stress is found. A possible solution involves allowing the turbine inlet temperature to rise to augment power while injecting water into the turbine cooling air to limit hot-section metal temperatures. An experimental water injection device was installed in an engine and successfully tested. Although concern for unprotected subcomponents in the engine hot section prevented demonstration of the technique's maximum potential, it was still possible to demonstrate increases in power while maintaining nearly constant turbine rotor blade temperature.
The GSFC pressure-temperature lidar is a differential absorption lidar operating in the oxygen A band absorption region (760 to 770 nm), and utilizes two tunable pulsed alexandrite lasers. For obtaining temperature measurements with an accuracy of less than or = 1 K, it has been determined that the stability of the online laser frequency over a period of time corresponding to a set of measurements, 0.1 to 30 min, has to be better than +/- 0.002/cm. In addition, the requirements on laser spectral bandwidth and spectral purity are less than or = 0.02/cm and greater than or = 99.9 percent, respectively. Injection seeding with a stabilized AlGaAs diode laser was used to achieve the required frequency stability and spectral bandwidth. A high resolution Fizeau wavemeter was employed to determine the frequency stability of the pulsed alexandrite laser and determine its bandwidth, mode structure. We present the results of measurements of the frequency stability and the spectrum of the injection seeded alexandrite laser.
The influence of dynamics on model results is investigated via a 2D photochemical model. Three representations of atmospheric transport are tested in order to simulate total ozone and C-14 amounts after nuclear tests in the early 1960s. Three scenarios of NO(x) injections from a proposed fleet of stratospheric aircraft and their effects on ozone are simulated. The three dynamical formulations used are Dynamics A, a base dynamics used in previous work with this model; Dynamics B, a strong circulation dynamics discussed by Jackman et al. (1989); and Dynamics C, the dynamics used by Shia et al. (1989). The advective component of the stratosphere to the troposphere mass exchange rate is largest for Dynamics B (5.8 x 10 exp 17 kg/yr) and smallest for Dynamics C (1.4 x 10 exp 17 kg/yr), with the advective strat/trop exchange rate for Dynamics A (2.4 x 10 exp 17 kg/yr) being these two extremes. Ozone depletion from NO(x) injections of stratospheric aircraft showed a strong sensitivity to dynamics.
A spatially-complete data set of the important primitive flow variables is presented for the complex, nonreacting, 3D unit combustor flow field employing transverse injection into a Mach 2 flow behind a rearward-facing step. A unique wind tunnel facility providing the capability for iodine seeding was built specifically for these measurements. Two optical techniques based on laser-induced-iodine fluorescence were developed and utilized for nonintrusive, in situ flow field measurements. LDA provided both mean and fluctuating velocity component measurements. A thermographic phosphor wall temperature measurement technique was developed and employed. Data from the 2D flow over a rearward-facing step and the complex 3D mixing flow with injection are reported.
On 24 March 1991 instrumentation aboard CRRES observed the almost instantaneous injection of electrons and protons with energies above 15 MeV into the L-region in the range 2-3. The energy spectrum of the injected electrons, a power law (E exp -6) peaked at 15 MeV and continued to at least 50 MeV.
Data from ARCS rocket ion beam injection experiments are primarily discussed. There are three results from this series of active experiments that are of particular interest in space plasma physics. These are the transverse acceleration of ambient ions in the large beam volume, the scattering of beam ions near the release payload, and the possible acceleration of electrons very close to the plasma generator which produce intense high frequency waves. The ability of 100 ma ion beam injections into the upper E and F regions of the ionosphere to produce these phenomena appear to be related solely to the process by which the plasma release payload and the ion beam are neutralized. Since the electrons in the plasma release do not convect with the plasma ions, the neutralization of both the payload and beam must be accomplished by large field-aligned currents (milliamperes/square meter) which are very unstable to wave growth of various modes.
A total of 38 hydrogen no-vent fill tests were performed in this test series using various size spray nozzles and a spray bar with different hole sizes in a 5 cubic foot receiver tank. Fill levels of 90 percent by volume or greater were achieved in 26 of the tests while maintaining a receiver tank pressure below 30 psia. Spray nozzles were mounted at the top of the tank, whereas, the spray bar was centered in the tank axially. The spray nozzle no-vent fills demonstrated tank pressure and temperature responses comparable to previous test series. Receiver tank pressure responses for the spray bar configuration were similar to the spray nozzle tests with the pressure initially rising rapidly, then leveling off as vapor condenses onto the discharging liquid streams, and finally ramping up near the end of the test due to ullage compression. Both liquid injection techniques tested were capable of filling the receiver tank to 90 percent under variable test conditions. Comparisons between the spray nozzle and spray bar configurations for well matched test conditions indicate the spray nozzle injection technique is more effective in minimizing the receiving tank pressure throughout a no-vent fill compared to the spray bar under normal gravity conditions.
A numerical study is reported of the three-dimensional nonreacting supersonic flow field produced by three parallel fuel injection schemes. Such injections are being considered as a means of enhancing fuel mixing in future Scramjet engine designs. The strength of vortex structures produced by ramp injectors and by rocket/jet interactions are quantified and their relative effectiveness in enhancing the fuel mixing process is addressed. An experimental setup for validation of the above numerical results has been constructed and preliminary results are presented. For the flow field parameters chosen, the ramp generated vorticity is found to be considerably larger than that generated by the shock. The unsteady recirculating flow field in the wake of the injector appears also to give rise to important additional vorticity and mixing.
The Diagnostics Test Facility (DTF) at NASA's Stennis Space Center (SSC) was designed and built to provide a standard rocket engine exhaust plume for use in the research and development of engine health monitoring instrumentation. A 1000 lb thrust class liquid oxygen (LOX)-gaseous hydrogen (GH2) fueled rocket engine is used as the subscale plume source to simulate the SSME during experimentation and instrument development. The ability of the DTF to provide efficient, and low cost test operations makes it uniquely suited for plume diagnostic experimentation. The most unique feature of the DTF is the Multiple Dopant Injection System (MDIS) that is used to seed the exhaust plume with the desired element or metal alloy. The dopant injection takes place at the fuel injector, yielding a very uniform and homogeneous distribution of the seeding material in the exhaust plume. The MDIS allows during a single test firing of the DTF, the seeding of the exhaust plume with up to three different dopants and also provides distilled water base lines between the dopants. A number of plume diagnostic-related experiments have already utilized the unique capabilities of the DTF.
Injection Seeding of a Ti:Al2O3 unstable resonator using both a pulsed single-mode Ti:Al2O3 laser and a continuous wave laser diode has been characterized. Results are compared with a theory which calculates injection seeding as function of seed and resonator alignment, beam profiles, and power.
Experimental results are presented for several wall-injected, constant-area scramjet experiments, performed in the T4 free-piston-driven shock tunnel. Stagnation enthalpies range from 5.7 to 10.1 MJ/kg, corresponding to flight Mach numbers of Mach 9.7 to Mach 13. Hydrogen fuel is injected from the rear of a step into a supersonic air stream, with combustion-chamber Mach numbers of 3.6 and 4.4, and static pressures of 40 kPa. The experimental results are compared to numerical predictions obtained from a two-dimensional, parabolic Navier-Stokes code, which modeled turbulence with a compressibility modified k-epsilon model, and used multi-reaction, finite-rate chemistry. The numerical and experimental results show reasonable agreement and indicate that the scramjet flows studied are predominantly mixing limited.
Narrowband radiation is produced from a pulsed alexandrite laser when injection seeded with the output of a low power, tunable, continuous wave single mode diode laser. Injection seeded power oscillators are easier to frequency stabilize than etalon narrowed lasers, are more efficient and less prone to optical damage. AlGaAs diode lasers are available with wavelengths from 760 to 770 nm in the oxygen A band that can be used for differential absorption lidar remote sensing of atmospheric pressure and temperature. Diodes with room temperature output at 740 nm may be cooled sufficiently to emit in the water vapor absorption band at 720-730 nm for humidity remote sensing. The diode laser linewidth of 200 MHz is sufficient to seed 2 or 3 longitudinal modes of the multi-transverse mode alexandrite laser, giving the pulsed laser a bandwidth of 0.007 to 0.014/cm.
Important problems are discussed concerning the effects of shock geometry on the injection of thermal particles and the process of standard Fermi particle acceleration in general. In pursuit of a self-consistent model that simultaneously describes shock structure and particle acceleration in shocks of arbitrary obliquity, a Monte Carlo simulation developed for parallel shocks is generalized to address oblique geometries. Attention is given to initial results concerning the ways in which injection and acceleration efficiency varies with obliquity and Mach number.
Time-averaged measurements of pressure, temperature, velocity, and injectant mole fraction are presented using the planar laser-induced iodine fluorescence (PLIIF) techniques in the complex 3D compressible flowfield around a swept ramp fuel injector. Within the range of thermodynamic conditions present in the test case studied, the technique's accuracy is estimated to be 4 percent for pressure, 4 percent for temperature, 4 percent for velocity, and 3 percent for injectant mole fraction. Comparisons to numerical simulations using the SPARK 3D Navier-Stokes computer code with an algebraic turbulence model are made at the centerplane of the flowfield as well as on three crossflow planes downstream of the injector, and good agreement is found. A weak asymmetry in the incoming flowfield appears to be amplified by boundary layer separation occuring when the the ramp generated shock reflects off the tunnel walls. In the near field of the injector, laminar calculations show better agreement to the measurements than turbulent calculations.