Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “explosive flow”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Interaction of a strong blast wave with a free surface

When a point source explosion is initiated at the ocean surface, the shock propagated into the water is reflected at the surface as a centered expansion wave. The solution in the neighborhood of the interaction point is obtained by writing the equations of motion in the appropriate similarity variables and then changing the independent variables to polar coordinates based at the interaction point. From the zero-order solution of the resulting equations the slopes of boundaries at the interaction point are obtained. A first-order perturbation of this solution provides more accurate representation of the flow variables and the curvature of the shock surface near the interaction point.

Falade, A.↗
NASA NTRS1974

An exploratory investigation of a wake disruption technique for studying wake reestablishment time

An exploratory investigation was made of a wake disruption technique for studying the hypersonic-wake reestablishment time in a blowdown wind tunnel. In this technique, a highly underexpanded jet issuing from the base of a 10 deg half-angle cone totally disrupts and displaces the conventional wake. The jet was rapidly shut off by an explosively actuated valve and the time for wake reestablishment was measured. The tests were conducted in the Mach 6 high Reynolds number tunnel at a stagnation temperature of 506 K and stagnation pressure of 2.86 MPa. The model base jet stagnation pressure was 3.55 MPa at room temperature. High-speed schlieren motion pictures indicated that disappearance of the disrupting jet and reestablishment of the wake-recompression shock were probably occurring simultaneously and that the time disruptive-jet-air shutoff to wake recompression shock reestablishment was probably between 200 and 450 microseconds (flow lengths from 1.8 to 4.2). The values of flow lengths are about one-thord to one-half the values measured in impulse facilities in a previous study. This shorter time is believed to be largely due to difference in flow conditions between the jet disruption technique and impulse facilities.

Clark, L. E.↗
NASA NTRS1997

The German/Russian MIR 1997 Mission: An Overview

Session TP4 includes short reports concerning: (1) Life Science Experiments During the German-Russian Mir '97 Mission; (2) Orthostatic Intolerance Following Microgravity: A Role for Autonomic Dysfunction; (3) Heart Rate Variability and Skin Blood Flow in Man During Orthostatic Stress in Weightlessness; (4) Effects of Microgravity and Lower Body Negative Pressure on Circulatory Drives from Excercising Calf Muscles; (5) The Mir Station in Its Second Decade: Crew Science Operation During Mir '97; (6) Metabolic WARD (Water, Sodium, Calcium, and Bone Metabolism) and Endocrinological Experiments During the Mir '97 Mission; (7) Long-term Monitoring of the Spine-geometry During the Mir '97 Mission: Introduction of a New Method; and (8) Effects of 20 days of Microgravity (German/Russian Mir '97 Mission) on the Mechanical and Electromyographic Characteristics of Explosive Efforts of the Lower Limbs and of Cycloergometric Exercises of Mild to Sprint-Like Intensity.

Source record↗
NASA NTRS1948

Simulated Altitude Performance of Combustors for the Westinghouse 24C Jet Engine I-24C-2 Combustor

A Westinghouse 24C-2 combustor was investigated at conditions simulating operation of the 24C Jet engine at zero ram over ranges of altitude and engine speed. The investigation was conducted to determine the altitude operational limits, that is, the maximum altitude for various engine speeds at which an average combustor-outlet gas temperature sufficient for operation of the jet engine could be obtained. Information was also obtained regarding the character of the flames, the combustion efficiency, the combustor-outlet gas temperature and velocity distributions, the extent of afterburning, the flow characteristics of the fuel manifolds, the combustor inlet-to-outlet total-pressure drop, and the durability of the combustor basket. The results of the investigation indicated that the altitude operational limits for zero ram decreased from 12,000 feet at an engine speed of 4000 rpm to a minimum of 9000 feet at 6000 rpm, and thence increased to 49,000 feet at 12,000 rpm.. At altitudes below the operational limits, flames were essentially steady, but, at altitudes above the operational limits, flames were often cycling and either blew out or caused violent explosions and vibrations. At conditions on the altitude operational limits the type of combustion varied from steady to cycling with increasing fuel-air ratio and the reverse occurred with decreasing fuel-air ratio. In the region of operation investigated, the combustion efficiency ranged from 75 to 95 percent at altitudes below the operational limits and dropped to 55 percent or less at some altitudes above the operational limits. The deviations in the local combustor-outlet gas temperatures were within +20 to -30 percent of the mean combustor temperature rise for inlet-air temperatures at the low end of the range investigated, but became more uneven (up to +/-100 percent) with increasing inlet-air temperatures. The distribution of the combustor-outlet gas velocity followed a similar trend. Practically no afterburning downstream of the combustor outlet occurred. At conditions of high inlet-air temperature several factors indicated that fuel vapor or air formed in the fuel manifolds and adversely affected combustion. The combustor inlet-to-outlet total-pressure drop can be correlated as a function of the ratio of the combustion-air inlet density to outlet density and of the inlet dynamic pressure. The walls of the combustor basket were warped and burned during 29 hours of operation.

Manganiello, Eugene J.↗
NASA NTRS1981

The modification stage of basin formation - Conditions of ring formation

The impact cratering process may be divided into three stages, including a short high pressure phase of initial contact between the projectile and target, a longer cratering flow phase during which material is both ejected and displaced to form the transient crater, and a still longer modification phase during which the transient crater is modified into the final observed form. The present investigation is concerned with the nature of the modification stage as constrained by the initial boundary condition which comprises the transient crater and its surroundings, and the final boundary condition which comprises the structure of observed craters and basins. A brief description is provided of an interpretation of basin ring structure based on geophysical, geological, and dimensional analysis of craters and basins on the moon, Mercury, and Mars, on structural observations of terrestrial impact and explosion craters, and on an empirical crater restoration model. A scenario of basin formation is constructed, and relations of this scenario to observed morphology are discussed.

Croft, S. K.↗
NASA NTRS2008

Fiber-Optic Determination of N2, O2, and Fuel Vapor in the Ullage of Liquid-Fuel Tanks

A fiber-optic sensor system has been developed that can remotely measure the concentration of molecular oxygen (O2), nitrogen (N2), hydrocarbon vapor, and other gases (CO2, CO, H2O, chlorofluorocarbons, etc.) in the ullage of a liquid-fuel tank. The system provides an accurate and quantitative identification of the above gases with an accuracy of better than 1 percent by volume (for O2 or N2) in real-time (5 seconds). In an effort to prevent aircraft fuel tank fires or explosions similar to the tragic TWA Flight 800 explosion in 1996, OBIGGS are currently being developed for large commercial aircraft to prevent dangerous conditions from forming inside fuel tanks by providing an inerting gas blanket that is low in oxygen, thus preventing the ignition of the fuel/air mixture in the ullage. OBIGGS have been used in military aircraft for many years and are now standard equipment on some newer large commercial aircraft (such as the Boeing 787). Currently, OBIGGS are being developed for retrofitting to existing commercial aircraft fleets in response to pending mandates from the FAA. Most OBIGGS use an air separation module (ASM) that separates O2 from N2 to make nitrogen-enriched air from compressed air flow diverted from the engine (bleed air). Current OBIGGS systems do not have a closed-loop feedback control, in part, due to the lack of suitable process sensors that can reliably measure N2 or O2 and at the same time, do not constitute an inherent source of ignition. Thus, current OBIGGS operate with a high factor-of-safety dictated by process protocol to ensure adequate fuel-tank inerting. This approach is inherently inefficient as it consumes more engine bleed air than is necessary compared to a closed-loop controlled approach. The reduction of bleed air usage is important as it reduces fuel consumption, which translates to both increased flight range and lower operational costs. Numerous approaches to developing OBIGGS feedback-control sensors have been under development by many research groups and companies. However, the direct measurement of nitrogen (N2) is a challenge to most OBIGGS ullage sensors (such as tunable diode laser absorption) as they cannot measure N2 directly but depend on the measurement of oxygen (O2). The problem with a singular measure of O2, is that as the concentration (number density) of O2 decreases due to the inerting process or due to lower pressures from high altitudes, the precision and accuracy of the O2 measurement decreases. However, measuring O2 density in combination with N2 density (which is more abundant in air and in a N2-inerted fuel tank) can provide a much more accurate and reliable determination of the OBIGGS efficacy.

Nguyen, Quang-Viet↗
NASA NTRS2011

A Magnetically Coupled Cryogenic Pump

Historically, cryogenic pumps used for propellant loading at Kennedy Space Center (KSC) and other NASA Centers have a bellows mechanical seal and oil bath ball bearings, both of which can be problematic and require high maintenance. Because of the extremely low temperatures, the mechanical seals are made of special materials and design, have wearing surfaces, are subject to improper installation, and commonly are a potential leak path. The ball bearings are non-precision bearings [ABEC-1 (Annular Bearing Engineering Council)] and are lubricated using LOX compatible oil. This oil is compatible with the propellant to prevent explosions, but does not have good lubricating properties. Due to the poor lubricity, it has been a goal of the KSC cryogenics community for the last 15 years to develop a magnetically coupled pump, which would eliminate these two potential issues. A number of projects have been attempted, but none of the pumps was a success. An off-the-shelf magnetically coupled pump (typically used with corrosive fluids) was procured that has been used for hypergolic service at KSC. The KSC Cryogenics Test Lab (CTL) operated the pump in cryogenic LN2 as received to determine a baseline for modifications required. The pump bushing, bearings, and thrust rings failed, and the pump would not flow liquid (this is a typical failure mode that was experienced in the previous attempts). Using the knowledge gained over the years designing and building cryogenic pumps, the CTL determined alternative materials that would be suitable for use under the pump design conditions. The CTL procured alternative materials for the bearings (bronze, aluminum bronze, and glass filled PTFE) and machined new bearing bushings, sleeves, and thrust rings. The designed clearances among the bushings, sleeves, thrust rings, case, and case cover were altered once again using experience gained from previous cryogenic pump rebuilds and designs. The alternative material parts were assembled into the pump, and the pump was successfully operated meeting all expected operating parameters. Unique pump sub-assembly parts were designed and manufactured by the CTL using specialized materials determined to be superior for cryogenic thermal applications under the pump design conditions. This work is a proof-of-concept/proof-of-operation of the pump only. Other known internal design modifications to the pump should be accomplished for the long-term use of the pump. An upscaled version of this pump, which is under development and testing at the CTL, can be used either for current or future vehicle loading or for vehicle replenishment. Scaling of this pump can be easily accomplished.

Hatfield, Walter↗
NASA NTRS2021

Dynamics of the Terrestrial Radiation Belts: a Review of Recent Results During the VarSITI (Variability of the Sun and Its Terrestrial Impact) Era, 2014–2018

The Earth’s magnetosphere is region that is carved out by the solar wind as it flows past and interacts with the terrestrial magnetic field. The inner magnetosphere is the region that contains the plasmasphere, ring current, and the radiation belts all co-located within about 6.6 Re, nominally taken to be bounding this region. This region is highly dynamic and is home to a variety of plasma waves and particle populations ranging in energy from a few eV to relativistic and ultra-relativistic electrons and ions. The interplanetary magnetic field (IMF) embedded in the solar wind via the process of magnetic reconnection at the sub-solar point sets up plasma convection and creates the magnetotail. Magnetic reconnection also occurs in the tail and is responsible for explosive phenomena known as substorms. Substorms inject low-energy particles into the inner magnetosphere and help generate and sustain plasma waves. Transients in the solar wind such as coronal mass ejections (CMEs), co-rotating interaction regions (CIRs), and interplanetary shocks compress the magnetosphere resulting in geomagnetic storms, energization, and loss of energetic electrons in the outer radiation belt and enhance the ring current, thereby driving the geomagnetic dynamics. The Specification and Prediction of the Coupled Inner-Magnetospheric Environment (SPeCIMEN) is one of the four elements of VarSITI (Variability of the Sun and Its Terrestrial Impact) program which seeks to quantitatively predict and specify the inner magnetospheric environment based on Sun/solar wind driving inputs. During the past 4 years, the SPeCIMEN project has brought together scientists and researchers from across the world and facilitated their efforts to achieve the project goal. This review provides an overview of some of the significant scientific advances in understanding the dynamical processes and their interconnectedness during the VarSITI era. Major space missions, with instrument suites providing in situ measurements, ground-based programs, progress in theory, and modeling are briefly discussed. Open outstanding questions and future directions of inner magnetospheric research are explored.

Shrikanth Kanekal↗
NASA NTRS1973

Experimental study of the dynamics of a spherical flame

Preliminary results of an experimental study conducted to investigate the dynamic behavior of flames in explosive gases are presented. The medium was an equimolar acetylene-oxygen mixture maintained initially at a pressure of 110 torr. and room temperature in an experimental vessel 9 cm in internal diameter. Ignition was performed by means of a neodymium laser beam focused on a 0.3 mm diameter steel wire. Experimental observations were performed by the use of a stroboscopic laser-schlieren system yielding a set of photographic records of wave phenomena at a frequency of 200,000 per second. The records reveal the existence of a number of shocks which by a thorough analysis of the blast wave generated by the ignition process, are shown to be due entirely to the flame generated flow field. The capability of a flame to form blast waves in an expanding spherical geometry is thus established, providing an experimental demonstration of the significance the dynamic effects of combustion can achieve.

Oppenheim, A. K.↗
NASA NTRS2022

Diffusion in Melts and Magmas

Diffusion results from random motion of particles and entities. Diffusion in melts and magmas is due to thermally excited random motion of atoms, ions, and clusters, and plays a critical role in magmatic and volcanic processes. In melts and magmas, diffusion is one of the two mechanisms of mass transfer; the other being bulk flow (referred to as convection or advection). When both are present, diffusion refers to the dispersive motion relative to the mean bulk flow in a given reference frame (Richter et al. 1998). Diffusion plays critical roles in controlling magma mixing (Watson 1982; Koyaguchi 1985, 1989; Lesher 1994; Huber et al. 2009; Guo and Zhang 2020), mineral growth and dissolution rates in magmas (e.g., Watson 1982; Harrison and Watson 1983; Zhang et al. 1989; Newcombe et al. 2014; Macris et al. 2018), bubble growth and dissolution rate in magmas (Sparks 1978; Proussevitch and Sahagian 1998; Liu and Zhang 2000; Zhang 2013), and elemental and isotope fractionation during mineral 2 growth and dissolution (Jambon 1980; Richter et al. 1999, 2003; Watson and Muller 2009; Chopra et al. 2012; Watkins et al. 2014, 2017; Holycross et al. 2016, 2018). As a result, diffusion also plays an essential role in explosive volcanic eruptions and magma crystallization. Furthermore, diffusion has important applications in geospeedometry (Lasaga 1983, 1998; Zhang 1994, 2008; Trail et al. 2016; Zhang and Xu 2016). Experimental investigation of diffusion in geologically relevant silicate melts began to flourish in the 1970’s when micro-analytical measurements of diffusion profiles became available. In addition to the vast number of papers published since then, numerous books and reviews are available for diffusion in silicate melts. Hofmann et al. (1974) edited a book titled “Geochemical Transport and Kinetics” published by Carnegie Institution of Washington. This was the first landmark book summarizing the field. Lasaga and Kirkpatrick (1981) edited a book “Kinetics of Geochemical Processes” as volume 8 of the Reviews in Mineralogy (later becoming Reviews in Mineralogy and Geochemistry) series. Zhang and Cherniak (2010) edited “Diffusion in Minerals and Melts” as volume 72 of Reviews of Mineralogy and Geochemistry series, in which one chapter focused on diffusion theory, five chapters on diffusion in silicate melts (Behrens 2010; Lesher 2010; Liang 2010; Zhang and Ni 2010; Zhang et al. 2010), and other chapters were on experimental, analytical, and computational methods, and diffusion in minerals. Several textbooks covered the principles and applications of diffusion theories (Kirkaldy and Young 1987; Shewmon 1989; Cussler 1997; Lasaga 1998; Zhang 2008; Vrentas and Vrentas 2016), and two classic books covered the mathematics of diffusion (Carslaw and Jaeger 1959; Crank 1975). In preparing for this review chapter, we thought carefully about what to cover for this vast field, and decided to briefly go through the fundamentals of diffusion (more complete review can be found in Chakraborty 1995; Zhang 2008, 2010) and solutions to often-encountered 3 diffusion problems, and then focus on post-2010 diffusion studies on silicate melts and magmas. Here, melts refer to (mostly natural) silicate liquid, and magmas refer to crystal-bearing and/or bubble-bearing melts in which the continuous phase is the melt. There is a large body of work on diffusion in glasses, especially in the materials science literature, which is not covered in this review.

Youxue Zhang↗
NASA NTRS2022

The Zn, S, and Cl Isotope Compositions of Mare Basalts: Implications for the Effects of Eruption Style and Pressure on Volatile Element Stable Isotope Fractionation on the Moon

We compare the stable isotope compositions of Zn, S, and Cl for Apollo mare basalts to better constrain the sources and timescales of lunar volatile loss. Mare basalts have broadly elevated yet limited ranges in δ(66)Zn, δ(34)S, and δ(37)Cl_(SBC+WSC) values of 1.27 ± 0.71, 0.55 ± 0.18, and 4.1 ± 4.0‰, respectively, compared to the silicate Earth at 0.15, –1.28, and 0‰, respectively. We find that the Zn, S, and Cl isotope compositions are similar between the low- and high-Ti mare basalts, providing evidence of a geochemical signature in the mare basalt source region that is inherited from lunar formation and magma ocean crystallization. The uniformity of these compositions implies mixing following mantle overturn, as well as minimal changes associated with subsequent mare magmatism. Degassing of mare magmas and lavas did not contribute to the large variations in Zn, S, and Cl isotope compositions found in some lunar materials (i.e., 15‰ in δ(66)Zn, 60‰ in δ(34)S, and 30‰ in δ(37)Cl). This reflects magma sources that experienced minimal volatile loss due to high confining pressures that generally exceeded their equilibrium saturation pressures. Alternatively, these data indicate effective isotopic fractionation factors were near unity. Our observations of S isotope compositions in mare basalts contrast to those for picritic glasses (Saal and Hauri 2021), which vary widely in S isotope compositions from –14.0 to 1.3‰, explained by extensive degassing of picritic magmas under high-P/P_(Sat) values (>0.9) during pyroclastic eruptions. The difference in the isotope compositions of picritic glass beads and mare basalts may result from differences in effusive (mare) and explosive (picritic) eruption styles, wherein the high-gas contents necessary for magma fragmentation would result in large effective isotopic fractionation factors during degassing of picritic magmas. Additionally, in highly vesiculated basalts, the δ(34)S and δ(37)Cl values of apatite grains are higher and more variable than the corresponding bulk-rock values. The large isotopic range in the vesiculated samples is explained by late-stage low-pressure “vacuum” degassing (P/P-(Sat) ~ 0) of mare lavas wherein vesicle formation and apatite crystallization took place post-eruption. Bulk-rock mare basalts were seemingly unaffected by vacuum degassing. Degassing of mare lavas only became important in the final stages of crystallization recorded in apatite—potentially facilitated by cracks/fractures in the crystallizing flow. We conclude that samples with wide-ranging volatile element isotope compositions are likely explained by localized processes, which do not represent the bulk Moon.

Halogens↗
NASA NTRS2012

NASA Tech Briefs, October 2012

Topics discussed include: Detection of Chemical Precursors of Explosives; Detecting Methane From Leaking Pipelines and as Greenhouse Gas in the Atmosphere; Onboard Sensor Data Qualification in Human-Rated Launch Vehicles; Rugged, Portable, Real-Time Optical Gaseous Analyzer for Hydrogen Fluoride; A Probabilistic Mass Estimation Algorithm for a Novel 7-Channel Capacitive Sample Verification Sensor; Low-Power Architecture for an Optical Life Gas Analyzer; Online Cable Tester and Rerouter; A Three-Frequency Feed for Millimeter-Wave Radiometry; Capacitance Probe Resonator for Multichannel Electrometer; Inverted Three-Junction Tandem Thermophotovoltaic Modules; Fabrication of Single Crystal MgO Capsules; Inflatable Hangar for Assembly of Large Structures in Space; Mars Aqueous Processing System; Hybrid Filter Membrane; Design for the Structure and the Mechanics of Moballs; Pressure Dome for High-Pressure Electrolyzer; Cascading Tesla Oscillating Flow Diode for Stirling Engine Gas Bearings; Compact, Low-Force, Low-Noise Linear Actuator; Ultra-Compact Motor Controller; Extreme Ionizing-Radiation-Resistant Bacterium; Wideband Single-Crystal Transducer for Bone Characterization; Fluorescence-Activated Cell Sorting of Live Versus Dead Bacterial Cells and Spores; Nonhazardous Urine Pretreatment Method; Laser-Ranging Transponders for Science Investigations of the Moon and Mars; Ka-Band Waveguide Three-Way Serial Combiner for MMIC Amplifiers; Structural Health Monitoring with Fiber Bragg Grating and Piezo Arrays; Low-Gain Circularly Polarized Antenna with Torus-Shaped Pattern; Stereo and IMU- Assisted Visual Odometry for Small Robots; Global Swath and Gridded Data Tiling; GOES-R: Satellite Insight; Aquarius iPhone Application; Monitoring of International Space Station Telemetry Using Shewhart Control Charts; Theory of a Traveling Wave Feed for a Planar Slot Array Antenna; Time Manager Software for a Flight Processor; Simulation of Oxygen Disintegration and Mixing With Hydrogen or Helium at Supercritical Pressure; A Superfluid Pulse Tube Refrigerator Without Moving Parts for Sub-Kelvin Cooling; Sapphire Viewports for a Venus Probe; The Mobile Chamber; Electric Propulsion Induced Secondary Mass Spectroscopy; and Radiation-Tolerant DC-DC Converters.

Source record↗
NASA NTRS2004

Impactites of the Yaxcopoil-1 drilling site, Chicxulub impact structure: Petrography, geochemistry, and depositional environment

The impact breccias encountered in drill hole Yaxcopoil-1 (Yax-1) in the Chicxulub impact structure have been subdivided into six units. The two uppermost units are redeposited suevite and suevite, and together are only 28 m thick. The two units below are interpreted as a ground surge deposit similar to a pyroclastic flow in a volcanic regime with a fine-grained top (unit 3; 23 m thick; nuee ardente) and a coarse breccia (unit 4; approx.15 m thick) below. As such, they consist of a melange of clastic matrix breccia and melt breccia. The pyroclastic ground surge deposit and the two units 5 and 6 below are related to the ejecta curtain. Unit 5 (approx.24 m thick) is a silicate impact melt breccia, whereas unit 6 (10 m thick) is largely a carbonate melt breccia with some clastic-matrix components. Unit 5 and 6 reflect an overturning of the target stratigraphy. The suevites of units 1 and 2 were deposited after emplacement of the ejecta curtain debris. Reaction of the super-heated breccias with seawater led to explosive activity similar to phreomagmatic steam explosion in volcanic regimes. This activity caused further brecciation of melt and melt fragments. The fallback suevite deposit of units 1 and 2 is much thinner than suevite deposits at larger distances from the center of the impact structure than the 60 km of the Yax-1 drill site. This is evidence that the fallback suevite deposit (units 1 and 2) originally was much thicker. Unit 1 exhibits sedimentological features suggestive of suevite redeposition. Erosion possibly has occurred right after the IUT impact due to seawater backsurge, but erosion processes spanning thousands of years may also have been active. Therefore, the top of the 100 m thick impactite sequence at Yaxcopoil, in our opinion, is not the K/T boundary.

Dressler, Burkhard O.↗
NASA NTRS2000

Numerical Modeling of Drying Residual RP-1 in Rocket Engines

When a Rocket Engine shuts down under a fuel rich environment, a significant amount of unburned RP-1 is trapped In the engine. It is necessary to clean the residual RP-1 prior to subsequent firing to avoid any explosion due to detonation. The conventional method is to dry RP-1 with inert gas such as Nitrogen or Helium. It is difficult to estimate the drying time unless the engine is adequately equipped with instruments to measure the trace of RP-1 during the drying process. Such instrumentation in flight hardware is often impractical and costly. On the other hand numerical modeling of the drying process can provide a good insight for a satisfactory operation of the process. A numerical model can provide answer to questions such as a) how long it takes to dry, b) which fluid is a better dryer for RP-1, c) how to reduce drying time etc. The purpose of the present paper is to describe a numerical model of drying RP-1 trapped in a cavity with flowing nitrogen or helium. The numerical model assumes one dimensional flow of drying fluid in contact with liquid pool of RP-1. An evaporative mass transfer takes place across the contact surface.

Majumdar, Alok↗
NASA NTRS1998

Injector Mixing Efficiency Experiments

Various optical diagnostic techniques such as laser induce fluorescence, Raman spectroscopy, laser Doppler velocimetry, and laser light scattering have been employed to study the flowfield downstream of a single injector element in a optically accessible rocket chamber at Penn State for a number o years. These techniques have been used with both liquid and gaseous oxygen at pressures up to 1000 psia which is the limit of the facility. The purpose of the test programs at Penn State were to develop the techniques and to study the flow field from various injector designs. To extend these studies to higher pressure and ultimately to multiple injectors require the capabilities of the Marshall Space Flight Center. These studies will extend the data base available for the various injector designs to higher pressure as well as to determine the interaction between multiple injectors. During this effort the Princeton Instruments ICCD camera was set up and checked out. The functionality of the system has been thoroughly checked and the shutter compensation time was found to be not working. The controller was returned to the manufacturer for warranty repair. The sensitivity has been measured and found to be approximately 60 counts per photon at maximum gain which agrees with the test data supplied by the manufacturer. The actual value depends on wavelength. The Princeton Instruments camera was been installed in a explosion proof tube for use with the rocket combustor. A 35 mm camera was also made ready for taking still photos inside the combustor. A fiber optic was used to transmit the laser light from an argon-ion laser to the rocket combustor for the light scattering images. This images were obtained for a LOX-hydrogen swirl coax injector. Several still photos were also obtained with the 35 mm camera for these firings.

Moser, Marlow D.↗
NASA NTRS2004

Recent Progress in Understanding the Sun's Magnetic Dynamo

100 years ago we thought that the Sun and stars shone as a result of slow gravitational contraction over a few tens of millions of years - putting astronomers at odds with geologists who claimed that the Earth was much, much older. That mystery was solved in the 1920s and 30s with the discovery of nuclear energy (proving that the geologists had it right all along). Other scientific mysteries concerning the Sun have come and gone but three major mysteries remain: 1) How does the Sun produce sunspots with an 11-year cycle? 2) What produces the huge explosions that result in solar flares, prominence eruptions, and coronal mass ejections? and 3) Why is the Sun's outer atmosphere, the corona, so darned hot? Recent progress in solar astronomy reveals a single key to understanding all three of these mysteries.The 11-year time scale for the sunspot cycle indicates the presence of a magnetic dynamo within the Sun. For decades this dynamo was though to operate within the Sun's convection zone - the outmost 30% of the Sun where convective currents transport heat and advect magnetic lines of force. The two leading theories for the dynamo had very different models for the dynamics of the convection zone. Actual measurements of the dynamics using the techniques of helioseismology showed that both of these models had to be wrong some 20 years ago. A thin layer of strongly sheared flow at the base of the convection zone (now called the tachocline) was then taken to be the seat of the dynamo. Over the last 10 years it has become apparent that a weak meridional circulation within the convection zone also plays a key role in the dynamo. This meridional circulation has plasma rising up from the tachocline in the equatorial regions, spreading out toward the poles at a top speed of about 10-20 m/s at the surface, sinking back down to the tachocline in the polar regions, and then flowing back toward the equator at a top speed of about 1-2 m/s in the tachocline itself. Recent dynamo models that include this meridional flow now appear to have some power for predicting the size of future sunspot cycles.

Hathaway, David. H.↗
NASA NTRS1981

Topography of Martian central volcanoes

Results are presented of the topographic mapping of six large central volcanoes on Mars. Stereo images of the volcanoes Olympus Mons, Elysium Mons, Albor Tholus, Ceraunius Tholus, Uranius Tholus and Uranius Patera were acquired by Viking Orbiter 1, and pairs of images were compiled into topographic maps through the use of digital image measurement techniques. Olympus Mons is found to have the general form of a terrestrial basaltic shield constructed almost entirely from lava flows, however with an altitude of 20-23 km and flank slopes averaging about 4 deg; a high nominal density indicates that anomalously dense lithosphere underlies the shield. Uranius Patera is observed to be a similar feature of present relief about 2 km, with its lower flanks buried by later lava flood deposits. Elysium Mons has about 13 km of local relief with average slopes of 4.4 deg, although its upper flank slopes are significantly steeper than those of Olympus Mons, suggesting a shield volcano modified by a terminal phase of mixed volcanic activity. Albor Tholus is found to be a partially buried 3-km shield-like construct, while Ceranius and Uranius Tholus are steeper cone-like features with reliefs of about 6 and 2 km, respectively, which may be lava shield constructs modified by a terminal stage of explosive activity.

Blasius, K. B.↗
NASA NTRS1983

The waiting point approximation in R-process calculations

The steady flow approximation to the r-process has been used to evaluate the validity of the waiting point assumption (that, for a given charge number Z, neutron captures become balanced by neutron photodisintegrations) under a variety of conditions. The criterion for the accuracy of the approximation for any set of nuclei with the same value of Z is that the ratio of the total rate of neutron photodisintegration in those nuclei to the total rate of neutron captures should be close to unity. No set of conditions involving neutron production by helium thermonuclear reactions (at temperatures up to 10 to the 9th K) could be found for which the waiting point approximation is useful for all values of Z, and it is recommended that all such r-process calculations not use this approximation. At higher temperatures, such as those characteristic of explosive carbon burning (2 x 10 to the 9th K), the waiting point approximation is much better.

Cameron, A. G. W.↗