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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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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Infrared vibration-rotation spectra of the ClO radical using tunable diode laser spectroscopy

Tunable diode laser spectroscopy is used to measure the infrared vibration-rotation spectra of the ClO radical. The radical is generated in a flow system where a Cl2-He mixture passes through a microwave discharge to dissociate the Cl2. An O3-O2 mixture from an ozone generator is injected into the system downstream of the microwave discharge where O3 combines with Cl to form ClO. By adjusting the gas flow rates to yield an excess of Cl atoms, all the ozone is combined. ClO concentration is measured with UV absorption at 2577 and 2772 A and a deuterium lamp as a continuous source. Total cell pressure is 5.5 torr. The diode laser spectrometer is calibrated with ammonia lines as a reference where possible. The frequency of vibration-rotation lines is expressed as a function of rotational quantum number, fundamental vibrational frequency, and the rotational constants of the upper and lower vibrational states.

Rogowski, R. S.↗
NASA NTRS2004

Hydrodynamic Modeling of Oxidizer-Rich Staged Combustion Injector Flow

The main objective of this work is to determine the unsteady hydrodynamic characteristics of coaxial swirl atomizers of interest in oxidizer-rich staged combustion (ORSC) liquid rocket engines. To this end, the pseudo-density (homogeneous flow) treatment combined with the Marker-and-Cell (MAC) numerical algorithm has been used to develop an axisymmetric with swirl, two-phase, unsteady model. The numerical model is capable of assessing the time-dependent orifice exit conditions and internal mixing for arbitrary fuel and oxidizer gas injection conditions. Parametric studies have been conducted to determine the effect of geometry, gas properties, and liquid properties on the exit massflow rate and velocity. It has been found that the frequency at which the liquid film oscillates increases as the density ratio and thickness increase, decreases as film thickness and liquid swirl velocity increase, and is unaffected by the mixing length. Additionally, it has been determined that the variation in the massflow rate increases as the liquid swirl velocity and liquid film thickness increase, and decreases as the density ratio, collar thickness, and mixing length increase.

Canino, J. V.↗
NASA NTRS2009

Production of NOx by Lightning and its Effects on Atmospheric Chemistry

Production of NO(x) by lightning remains the NO(x) source with the greatest uncertainty. Current estimates of the global source strength range over a factor of four (from 2 to 8 TgN/year). Ongoing efforts to reduce this uncertainty through field programs, cloud-resolved modeling, global modeling, and satellite data analysis will be described in this seminar. Representation of the lightning source in global or regional chemical transport models requires three types of information: the distribution of lightning flashes as a function of time and space, the production of NO(x) per flash, and the effective vertical distribution of the lightning-injected NO(x). Methods of specifying these items in a model will be discussed. For example, the current method of specifying flash rates in NASA's Global Modeling Initiative (GMI) chemical transport model will be discussed, as well as work underway in developing algorithms for use in the regional models CMAQ and WRF-Chem. A number of methods have been employed to estimate either production per lightning flash or the production per unit flash length. Such estimates derived from cloud-resolved chemistry simulations and from satellite NO2 retrievals will be presented as well as the methodologies employed. Cloud-resolved model output has also been used in developing vertical profiles of lightning NO(x) for use in global models. Effects of lightning NO(x) on O3 and HO(x) distributions will be illustrated regionally and globally.

Pickering, Kenneth E.↗
NASA NTRS2019

Frequency Control of Multi-Pulse 2-micron Laser Transmitter for Atmospheric Carbon Dioxide Measurement

Laser sources with highly stabilized emission wavelength is of paramount importance for a long term atmospheric carbon dioxide (CO2) measurement from a space platform. Integrated Path Differential Absorption (IPDA) lidar is a promising instrument for such a task. The design of a laser transmitter, with emphasis on the method used to control and select several wavelengths, is presented. This multi-pulsed, injection seeded, 2-μm transmitter uses a Ho:Tm:YLF laser crystal which has matching emission to the absorption of CO2 in the R30 spectroscopic area. The injection seeded laser produces triple single longitudinal mode transform limited line width pulses with a total of 80 mJ at a repetition rate of 50 Hz.

Petros, Mulugeta↗
NASA NTRS2014

Single Event Analysis and Fault Injection Techniques Targeting Complex Designs Implemented in Xilinx-Virtex Family Field Programmable Gate Array (FPGA) Devices

An informative session regarding SRAM FPGA basics. Presenting a framework for fault injection techniques applied to Xilinx Field Programmable Gate Arrays (FPGAs). Introduce an overlooked time component that illustrates fault injection is impractical for most real designs as a stand-alone characterization tool. Demonstrate procedures that benefit from fault injection error analysis.

Single Event Upset Testing↗
NASA NTRS2011

Can Water-Injected Turbomachines Provide Cost-Effective Emissions and Maintenance Reductions?

An investigation has been performed to evaluate the effect of water injection on the performance of the Air Force Research Laboratory (AFRL, Wright-Patterson Air Force Base (WPAFB)) experimental trapped vortex combustor (TVC) over a range of fuel-to-air and water-to-fuel ratios. Performance is characterized by combustor exit quantities: temperature and emissions measurements using rakes, and overall pressure drop, from upstream plenum to combustor exit. Combustor visualization is performed using gray-scale and color still photographs and high-frame-rate videos. A parallel investigation evaluated the performance of a computational fluid dynamics (CFD) tool for the prediction of the reacting flow in a liquid fueled combustor (e.g., TVC) that uses water injection for control of pollutant emissions and turbine inlet temperature. Generally, reasonable agreement is found between data and NO(x) computations. Based on a study assessing the feasibility and performance impact of using water injection on a Boeing 747-400 aircraft to reduce NO(x) emissions during takeoff, retrofitting does not appear to be cost effective; however, an operator of a newly designed engine and airframe might be able to save up to 1.0 percent in operating costs. Other challenges of water injection will be discussed.

Hendricks, Robert C.↗
NASA NTRS1981

Sensitivity tests of two-dimensional model predictions of corridor effects

Future aerospace-vehicle systems, such as supersonic transport fleets, the Space Shuttle (SS), and the Heavy-Lift Launch Vehicle (HLLV) system will inject substantial amounts of pollutants into the stratosphere. It is, therefore, pertinent to ask whether the operation of these systems will lead to deleterious effects in the atmosphere. The current investigation is concerned with the development of criteria to assess the likelihood of a detectable corridor effect being caused by the long-term deposition of pollutants at a single latitude. The sources are assumed to operate continuously and at a uniform rate for periods of many years. It is found that transport by meridional winds and by eddy processes acts to diminish the corridor effect by advecting the pollutants out of the region of injection and by mixing them with the ambient air. Attention is given to the altitude for which a detectable corridor effect can be expected for the hypothetical launching of 400 HLLV's per year for 10 years.

Borucki, W. J.↗
NASA NTRS1992

Ignition delays, heats of combustion, and reaction rates of aluminum alkyl derivatives used as ignition and combustion enhancers for supersonic combustors

The work was based on adapting an apparatus and procedure developed at Southwest Research Institute for rating the ignition quality of fuels for diesel engines. Aluminum alkyls and various Lewis-base adducts of these materials, both neat and mixed 50/50 with pure JP-10 hydrocarbon, were injected into the combustion bomb using a high-pressure injection system. The bomb was pre-charged with air that was set at various initial temperatures and pressures for constant oxygen density. The ignition delay times were determined for the test materials at these different initial conditions. The data are presented in absolute terms as well as comparisons with the parent alkyls. The relative heats of reaction of the various test materials were estimated based on a computation of the heat release, using the pressure data recorded during combustion in the bomb. In addition, the global reaction rates for each material were compared at a selected tmperature and pressure.

Ryan, T. W., III↗
NASA NTRS1972

Propulsion requirements for communications satellites.

The concept of characteristics thrust is introduced herein as a means of classifying propulsion system tasks related particularly to geosynchronous communications spacecraft. Approximate analytical models are developed to permit estimation of characteristic thrust for injection error corrections, orbit angle re-location, north-south station keeping, east-west station keeping, spin axis precession control, attitude rate damping, and orbit raising applications. Performance assessment factors are then outlined in terms of characteristic power, characteristic weight, and characteristic volume envelope, which are related to the characteristic thrust. Finally, selected performance curves are shown for power as a function of spacecraft weight, including the influence of duty cycle on north-south station keeping, a 90 degree orbit angle re-location in 14 days, and finally comparison of orbit raising tasks from low and intermediate orbits to a final geosynchronous station. Power requirements range from less than 75 watts for north-south station keeping on small payloads up to greater than 15 KW for a 180 day orbit raising mission including a 28.5 degree plane change.

Isley, W. C.↗
NASA NTRS1978

Experimental investigation of contamination prevention techniques for a cryogenically cooled telescope in earth-orbit

A one-tenth scale model of the Shuttle Infrared Telescope Facility (SIRTF) was constructed to experimentally investigate the feasibility of a helium purge system to reduce contamination on cryogenic surfaces. The on-orbit ambient contaminant environment was simulated with ion beams of N2(+), O(+) and H2O(+). Helium was injected into the model telescope at the simulated plane of the primary optics using two techniques: a) porous plug, b) nozzle. Helium flow rates and telescope pressures were varied to determine the purge effectiveness against potential contaminants. Based on the subscale results, a 90% reduction in O, N2, and H2O at the primary optics of the SIRTF can be obtained using 20 K helium with a pressure of .00001 torr and a flow rate of less than 0.1 g/s.

Hetrick, M. A.↗
NASA NTRS1988

Thrust-reverser flow investigation on a twin-engine transport

An investigation was conducted in the NASA Langley 14 x 22 foot Subsonic Tunnel to study the effects of engine thrust reversing on an aft-mounted twin-engine transport and to develop effective testing techniques. Testing was done over a fixed and a moving-belt ground plane and over a pressure instrumented ground board. Free-stream dynamic pressure was set at values up to 12.2 psf, which corresponded to a maximum Reynolds number based on the mean aerodynamic chord of 765,000. The thrust reversers examined included cascade, target and four-door configurations. The investigation focused on the range of free-stream velocities and engine thrust-reverser flow rates that would be typical for landing ground-roll conditions. Flow visualization techniques were investigated, and the use of water or smoke injected into the reverser flow proved effective to determine the forward progression of the reversed flow and reingestion limits. When testing over a moving-belt ground plane, as opposed to a fixed ground plane, forward penetration of the reversed flow was reduced. The use of a pressure-instrumented ground board enabled reversed flow ground velocities to be obtained, and it provided a means by which to identify the reversed flow impingement point on the ground.

Gatlin, Gregory M.↗
NASA NTRS1987

Multi-limbed locomotion systems for space construction and maintenance

A well developed technology of coordination of multi-limbed locomotory systems is now available. Results from a NASA sponsored study of several years ago are presented. This was a simulation study of a three-limbed locomotion/manipulation system. Each limb had six degrees of freedom and could be used either as a locomotory grasping hand-holds, or as a manipulator. The focus of the study was kinematic coordination algorithms. The presentation will also include very recent results from the Adaptive Suspension Vehicle Project. The Adaptive Suspension Vehicle (ASV) is a legged locomotion system designed for terrestrial use which is capable of operating in completely unstructured terrain in either a teleoperated or operator-on-board mode. Future development may include autonomous operation. The ASV features a very advanced coordination and control system which could readily be adapted to operation in space. An inertial package with a vertical gyro, and rate gyros and accelerometers on three orthogonal axes provides body position information at high bandwidth. This is compared to the operator's commands, injected via a joystick to provide a commanded force system on the vehicle's body. This system is, in turn, decomposed by a coordination algorithm into force commands to those legs which are in contact with the ground.

Waldron, K. J.↗
NASA NTRS2001

Nuclear Thermal Rocket (NTR) Propulsion and Power Systems for Outer Planetary Exploration Missions

The high specific impulse (I (sub sp)) and engine thrust generated using liquid hydrogen (LH2)-cooled Nuclear Thermal Rocket (NTR) propulsion makes them attractive for upper stage applications for difficult robotic science missions to the outer planets. Besides high (I (sub sp)) and thrust, NTR engines can also be designed for "bimodal" operation allowing substantial amounts of electrical power (10's of kWe ) to be generated for onboard spacecraft systems and high data rate communications with Earth during the course of the mission. Two possible options for using the NTR are examined here. A high performance injection stage utilizing a single 15 klbf thrust engine can inject large payloads to the outer planets using a 20 t-class launch vehicle when operated in an "expendable mode". A smaller bimodal NTR stage generating approx. 1 klbf of thrust and 20 to 40 kWe for electric propulsion can deliver approx. 100 kg using lower cost launch vehicles. Additional information is contained in the original extended abstract.

Borowski, S. K.↗
NASA NTRS1997

Mixing Enhancement in a Lobed Injector

An experimental investigation of the non-reactive mixing processes associated with a lobed fuel injector in a coflowing air stream is presented. The lobed fuel injector is a device which generates streamwise vorticity, producing high strain rates which can enhance the mixing of reactants while delaying ignition in a controlled manner. The lobed injectors examined in the present study consist of two corrugated plates between which a fuel surrogate, CO2, is injected into coflowing air. Acetone is seeded in the CO2 supply as a fuel marker. Comparison of two alternative lobed injector geometries is made with a straight fuel injector to determine net differences in mixing and strain fields due to streamwise vorticity generation. Planar laser-induced fluorescence (PLIF) of the seeded acetone yields two-dimensional images of the scalar concentration field at various downstream locations, from which local mixing and scalar dissipation rates are computed. It is found that the lobed injector geometry can enhance molecular mixing and create a highly strained flowfield, and that the strain rates generated by scalar energy dissipation can potentially delay ignition in a reacting flowfield.

Smith, L. L.↗
NASA NTRS1972

Rare-gas effects on metabolism and inert gas narcosis

The detailed examination is reported of the theory that narcosis results from expansion of the cell membrane under high partial pressures. The research is partially based on the hypothesis that, like oxygen toxicity, the mechanism of metabolic effects of rare gases may be similar at both low and high pressures and are simply more observable at high pressures. Using adult female goats, the parameters measured include oxygen consumption, CO2 production, respiration rate, heart rate, rectal and skin temperatures and the analysis of electroencephalograms and evoked response. Additionally, the specific activity is measured of plasma glucose subsequent to injection of glucose-UL-C-14, intravenous infusion, specific activity of expired CO2, unesterified fatty acid levels and whole blood lactate-to-pyruvate ratios. Also studied were the effects of acetylsalicylic acid, vitamin E and cationic detergents (which alleviate narcosis) upon metabolic changes induced by high pressure narcosis.

Source record↗
NASA NTRS1980

The influence of a voltage ramp on the measurement of I-V characteristics of a solar cell

For efficiency and convenience the voltage applied to a Si solar cell is often fairly rapidly driven from zero to the open circuit value typically at a common rate of 1 V per millisecond. During this time the values of current are determined as a function of the instantaneous voltage thus producing an I-V characteristic. The present paper shows that the customary expressions for the current as a function of cell parameters still remain valid provided that the diffusion length in the expression for the dark current is changed from its steady state value L to the effective diffusion length L1 given by L1 = L(1 + qV/kT.tau) to the -1/2, where V is the ramp rate considered constant and tau is the lifetime of minority carriers. This result is true to a very good approximation provided that low level injection prevails.

Von Roos, O.↗
NASA NTRS1987

Theoretical and Experimental Investigations of Ignition, Combustion and Expansion Processes of Hypergolic Liquid Fuel Combinations at Gas Temperatures up to 3000 K

The ignition, combustion, and expansion characteristics of hypergolic liquid propellant mixtures in small rocket engines are studied theoretically and experimentally. It is shown by using the Bray approximation procedure that the reaction H + OH + M = H2O + M (where M is the molecular mass of the gas mixture) has a strong effect on the combustion efficiency. Increases in recombination energies ranging from 30 to 65% were obtained when the rate of this reaction was increased by a factor of 10 in gas mixtures containing 90% oxygen. The effect of aluminum additions and various injection techniques on the combustion process is investigated.

Schulz, Harry↗