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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Can MARSIS Measure the Low-Altitude Components of the Mars Magnetic Field?

Measuring the magnetic field anomaly of Mars at low altitudes (e.g. 100-200 km) can be an interesting application of Mars Advance Radar for Subsurface and Ionospheric Sounder (MARSIS). Due to a low HF operation frequency, the radio wave propagating in the ionosphere of Mars, over the magnetic anomaly regions, will be affected and distorted by the localized magnetic field. This distortion in the sounder signal is due to the Faraday rotation and provides information about the strength of the magnetic field. MARSIS is especially sensitive to the radial magnetic field at altitudes where the electron density in the ionosphere peaks (i.e. 100-200 km). Consequently, MARSIS is potentially capable of providing measurements for the radial component of the magnetic field at altitudes between 100 to 200 km that are normally out of reach for orbital magnetometers (with the exception of the aero-braking phase). Such low-altitude measurements would be complementary to already existing measurements at 400 km by MAG-ER on Mars Global Surveyor. This paper will explain the sensitivity of MARSIS as a magnetometer and the method envisioned to measure the radial magnetic field component. MARSIS (Picardi et al.), the first major planetary radar sounder, is the result of an international collaboration between NASA, the Italian Space Agency (ASI), and European Space Agency (ESA), and will arrive at Mars in early 2004 for a two-year mission. MARSIS has a frequency range between 0.1-5.5 MHz and is designed to penetrate the subsurface to a depth of a few kilometers. MARSIS primary objective is to map and characterize the subsurface geological structure of Mars, and search for subsurface liquid water reservoirs. The secondary objective of MARSIS is to study the ionosphere of Mars providing the most extensive amount of data on Martian ionosphere to date. In addition to MARSIS, a second radar sounder named SHARAD (SHallow RADar) with operation frequency of 15-25 MHz is under development. SHARAD is an Italian instrument (Seu et. al) that will fly on NASA s Mars Reconnaissance orbiter in 2005. SHARAD can also provide magnetic measurements, however, it is not expected to be as sensitive as MARSIS to magnetic field variations.

A Safaeinili↗
NASA NTRS1990

Incidence angle and resolution - Potential effects on interpreting Venusian impact craters in Magellan radar images

The effects of incidence angle and spatial resolution are analyzed in order to evaluate the types of information that Magellan imaging radar may provide about impact craters on Venus. Seasat synthetic-aperture radar images of small terrestrial craters at high resolution (about 25 m) and Soviet Venera images of comparatively large Venusian craters at low resolution (1000 to 2000 m) and shorter wavelength show comparable radar responses to crater morphology. At low incidence angles, it is difficult to locate the precise position of crater rims on images, while at higher incidence angles, images show less distortion of crater morphology. Magellan will obtain images through a range of incidence angles varying from about 45 deg at low latitudes to 16 deg at polar latitudes. Radially symmetrical landforms such as impact craters are expected to show outlines that vary with the incidence angle and to appear bilaterally symmetrical and increasingly compressed at higher latitude.

Ford, J. P.↗
NASA NTRS1992

Rapid oscillations in cataclysmic variables. VIII - YY Draconis (=3A 1148 + 719)

A 16th magnitude cataclysmic variable presumably a dwarf nova, was detected near one of the positions permitted for the hard (2-10 keV) X-ray source 3A 1148 + 719. The optical and UV spectra of YY Dra are fairly typical of cataclysmic variables, except that the TiO absorption bands of an M dwarf can be seen for greater than 5000 A. This shows that the accretion disk is intrinsically faint in quiescence, suggesting a very low accretion rate. Yet the fairly blue continuum slope in the vacuum UV indicates the presence of a small hot object, presumably the white dwarf. The radial velocities at H-alpha indicate a 4.0-hr orbital period, and the IR light curve appears to show the expected 'double-humped' waveform from the distorted secondary. High-speed photometry in the U band reveals a stable periodicity of about 1-percent semiamplitude at a period of 275 s, with some power also in the subharmonic at about 550 s.

Patterson, J.↗
NASA NTRS2004

Vibration-Based Data Used to Detect Cracks in Rotating Disks

Rotor health monitoring and online damage detection are increasingly gaining the interest of aircraft engine manufacturers. This is primarily due to the fact that there is a necessity for improved safety during operation as well as a need for lower maintenance costs. Applied techniques for the damage detection and health monitoring of rotors are essential for engine safety, reliability, and life prediction. Recently, the United States set the ambitious goal of reducing the fatal accident rate for commercial aviation by 80 percent within 10 years. In turn, NASA, in collaboration with the Federal Aviation Administration, other Federal agencies, universities, and the airline and aircraft industries, responded by developing the Aviation Safety Program. This program provides research and technology products needed to help the aerospace industry achieve their aviation safety goal. The Nondestructive Evaluation (NDE) Group of the Optical Instrumentation Technology Branch at the NASA Glenn Research Center is currently developing propulsion-system-specific technologies to detect damage prior to catastrophe under the propulsion health management task. Currently, the NDE group is assessing the feasibility of utilizing real-time vibration data to detect cracks in turbine disks. The data are obtained from radial blade-tip clearance and shaft-clearance measurements made using capacitive or eddy-current probes. The concept is based on the fact that disk cracks distort the strain field within the component. This, in turn, causes a small deformation in the disk's geometry as well as a possible change in the system's center of mass. The geometric change and the center of mass shift can be indirectly characterized by monitoring the amplitude and phase of the first harmonic (i.e., the 1 component) of the vibration data. Spin pit experiments and full-scale engine tests have been conducted while monitoring for crack growth with this detection methodology. Even so, published data are extremely limited, and the basic foundation of the methodology has not been fully studied. The NDE group is working on developing this foundation on the basis of theoretical modeling as well as experimental data by using the newly constructed subscale spin system shown in the preceding photograph. This, in turn, involved designing an optimal sub-scale disk that was meant to represent a full-scale turbine disk; conducting finite element analyses of undamaged and damaged disks to define the disk's deformation and the resulting shift in center of mass; and creating a rotordynamic model of the complete disk and shaft assembly to confirm operation beyond the first critical concerning the subscale experimental setup. The finite element analysis data, defining the center of mass shift due to disk damage, are shown. As an example, the change in the center of mass for a disk spinning at 8000 rpm with a 0.963-in. notch was 1.3 x 10(exp -4) in. The actual vibration response of an undamaged disk as well as the theoretical response of a cracked disk is shown. Experiments with cracked disks are continuing, and new approaches for analyzing the captured vibration data are being developed to better detect damage in a rotor. In addition, the subscale spin system is being used to test the durability and sensitivity of new NDE sensors that focus on detecting localized damage. This is designed to supplement the global response of the crack-detection methodology described here.

Gyekenyesi, Andrew L.↗
NASA NTRS2007

Finite Element Analysis of the LOLA Receiver Telescope Lens

This paper presents the finite element stress and distortion analysis completed on the Receiver Telescope lens of the Lunar Orbiter Laser Altimeter (LOLA). LOLA is one of six instruments on the Lunar Reconnaissance Orbiter (LRO), scheduled to launch in 2008. LOLA's main objective is to produce a high-resolution global lunar topographic model to aid in safe landings and enhance surface mobility in future exploration missions. The Receiver Telescope captures the laser pulses transmitted through a diffractive optical element (DOE) and reflected off the lunar surface. The largest lens of the Receiver Telescope, Lens 1, is a 150 mm diameter aspheric lens originally designed to be made of BK7 glass. The finite element model of the Receiver Telescope Lens 1 is comprised of solid elements and constrained in a manner consistent with the behavior of the mounting configuration of the Receiver Telescope tube. Twenty-one temperature load cases were mapped to the nodes based on thermal analysis completed by LOLA's lead thermal analyst, and loads were applied to simulate the preload applied from the ring flexure. The thermal environment of the baseline design (uncoated BK7 lens with no baffle) produces large radial and axial gradients in the lens. These large gradients create internal stresses that may lead to part failure, as well as significant bending that degrades optical performance. The high stresses and large distortions shown in the analysis precipitated a design change from BK7 glass to sapphire.

Matzinger, Elizabeth↗
NASA NTRS1983

Laboratory and astronomical measurement of the millimeter wave spectrum of the ethynyl radical CCH

The N = 0 yields 1 and 1 yields 2 rotational transitions of CCH at 87 and 174 GHz, respectively, have been detected in a laboratory glow discharge in a mixture of He and C2H2. The spectroscopic constants of CCH derived from measurements of the hfs of the transitions agree well with those derived from astronomical observations, confirming the astronomical detection of CCH. As the CCH lines in the Orion Nebula are narrower than the laboratory lines but less certain in rest frequency owing to uncertainty in the radial velocity, the most accurate values for the spectroscopic constants of CCH are obtained from a simultaneous fit of both the laboratory and astronomical data. For the rotation, centrifugal distortion, spin-rotation, and hyperfine constants, respectively, the values found are within 0.006 of 43674.534 MHz, within 0.0008 of 0.1071 MHz, within 0.004 of -62.606 MHz, b = within 0.019 MHz of 40.426, and c is within 0.026 of 12.254 MHz.

Gottlieb, C. A.↗
NASA NTRS1975

Lateral distortions of electromagnetic cascades in emulsion chambers

Electromagnetic cascades in a lead-emulsion chamber have been studied to determine the effect of air gaps on the upstream sides of the emulsions. Such air gaps cause a change in the form of the radial distribution of electron tracks, making cascades appear older and giving incorrect energy estimates. The number of tracks remaining within a radius r was found to vary as exp(-g/G), where g is the gap thickness. The characteristic gap thickness in mm is G = 3.04 + 1.30 ln (Err per GeV per sq mm) where E is the energy of the initiating gamma ray. Use of this relation provides a significant correction to cascade-energy estimates and allows one to calculate the effect of different gap thicknesses on the energy threshold for visual detection of cascades.

Porter, L. G.↗
NASA NTRS1989

Evidence of a nearby solar wind shock as obtained from distant Pioneer 10 ultraviolet glow data

Pioneer 10 UV photometric data are used to study the nature of the heliospheric boundary interactions between solar wind and inflowing partially ionized interstellar wind and the interstellar magnetic field. The radial intensity dependence of solar Ly-alpha photons backscattered by inflowing interstellar hydrogen atoms is observed. The data in the downstream direction at distances greater than about 37 AU show a distortion of the incoming hydrogen atom density profile. It is suggested that this is characteristic of a nearby solar wind shock probably located about 50 AU from the sun in January 1987.

Gangopadhyay, P.↗
NASA NTRSDate not supplied

Lightweight Thrust Chamber Assemblies using Multi-Alloy Additive Manufacturing and Composite Overwrap

Additive Manufacturing (AM) has brought significant design and fabrication opportunities for complex components with internal features such as liquid rocket engine thrust chambers not previously possible. This technology allows for significant cost savings and schedule reductions in addition to new performance optimization through weight reduction and increased margins. Specific to regeneratively-cooled combustion chambers and nozzles for liquid rocket engines, additive manufacturing offers the ability to form the complex internal coolant channels and the closeout of the channels to contain the high pressure liquid propellants with a single operation. Much of additive manufacturing development has focused on monolithic alloys using Laser Powder Bed Fusion (L-PBF), which do not allow for complete optimization of the structure. The National Aeronautics and Space Administration (NASA) completed feasibility of an AM bimetallic L-PBF GRCop-84 copper-alloy combustion chamber with an AM electron beam freeform Inconel 625 structural jacket under the Low Cost Upper Stage Propulsion (LCUSP) Project. A follow-on project called Rapid Analysis and Manufacturing Propulsion Technology (RAMPT) is under development to further expand large-scale multi-alloy thrust chambers while maturing composite overwrap technology for significant weight savings opportunities. The RAMPT project has three primary objectives: 1) Advancing blown powder Directed Energy Deposition (DED) to fabricate integral-channel large scale nozzles, 2) Develop composite overwrap technology to reduce weight and provide structural capability for thrust chamber assemblies, and 3) Develop bimetallic and multi-metallic additively manufactured radial and axial joints to optimize material performance. In addition to these primary manufacturing developments, analytical modeling efforts compliment the process development to simulate the AM processes to reduce build failures and distortions. The RAMPT project is also maturing the supply chain for various manufacturing processes described above in addition to L-PBF of GRCop-42. This paper will present an overview of the RAMPT project, the process development and hardware progress to date, material and hot-fire testing results, along with future developments.

Additive Manufacturing↗
NASA NTRS1999

Water Flow Performance of a Superscale Model of the Fastrac Liquid Oxygen Pump

As part of the National Aeronautics and Space Administration's ongoing effort to lower the cost of access to space, the Marshall Space Flight Center has developed a rocket engine with 60,000 pounds of thrust for use on the Reusable Launch Vehicle technology demonstrator slated for launch in 2000. This gas generator cycle engine, known as the Fastrac engine, uses liquid oxygen and RP-1 for propellants and includes single stage liquid oxygen and RP-1 pumps and a single stage supersonic turbine on a common shaft. The turbopump design effort included the first use and application of new suction capability prediction codes and three-dimensional blade generation codes in an attempt to reduce the turbomachinery design and certification costs typically associated with rocket engine development. To verify the pump's predicted cavitation performance, a water flow test of a superscale model of the Fastrac liquid oxygen pump was conducted to experimentally evaluate the liquid oxygen pump's performance at and around the design point. The water flow test article replicated the flow path of the Fastrac liquid oxygen pump in a 1.582x scale model, including scaled seal clearances for correct leakage flow at a model operating speed of 5000 revolutions per minute. Flow entered the 3-blade axial-flow inducer, transitioned to a shrouded, 6-blade radial impeller, and discharged into a vaneless radial diffuser and collection volute. The test article included approximately 50 total and static pressure measurement locations as well as flush-mounted, high frequency pressure transducers for complete mapping of the pressure environment. The primary objectives of the water flow test were to measure the steady-state and dynamic pressure environment of the liquid oxygen pump versus flow coefficient, suction specific speed, and back face leakage flow rate. Results showed excellent correlation between the predicted and experimentally measured pump head rise at low suction specific speeds. Likewise, only small circumferential variations in steady-state impeller exit and radial diffuser pressure distributions were observed from 80% to 120% of the design flow coefficient, matching the computational predictions and confirming that the integrated design approach has minimized any exit volute-induced distortions. The test article exhibited suction performance trends typically observed in inducer designs with virtually constant head rise with decreasing inlet pressure until complete pump head breakdown. Unfortunately, the net positive suction head at 3% head fall-off occurred far below that predicted at all tested flow coefficients, resulting in a negative net positive suction head margin at the design point in water. Additional testing to map the unsteady pressure environment was conducted and interesting rotating phenomena at the inducer inlet were observed. These rotating phenomena's cell numbers, direction, and speed were correlated with pump operating parameters. The impact of the unsteady phenomena and their corresponding energy losses on the unexpectedly poor pump performance is also discussed.

Skelley, Stephen↗
NASA NTRS1993

Radial Splines Would Prevent Rotation Of Bearing Race

Interlocking fine-pitch ribs and grooves formed on otherwise flat mating end faces of housing and outer race of rolling-element bearing to be mounted in housing, according to proposal. Splines bear large torque loads and impose minimal distortion on raceway.

Kaplan, Ronald M.↗
NASA NTRS2004

Kinematic Treatment of CME Evolution in the Solar Wind

We present a kinematic study of the evolution of coronal mass ejections (CMEs) in the solar wind. Specifically, we consider the effects of: (1) spherical expansion; and (2) uniform expansion due to pressure gradients between the Interplanetary CME (ICME) and the ambient solar wind. We compare these results with an MHD model, which allows us to isolate these effects from the combined kinematic and dynamical effects, which are included in MHD models. They also provide compelling evidence that the fundamental cross section of so-called "force-free" flux ropes (or magnetic clouds) is neither circular or elliptical, but rather a convex-outward, "pancake" shape. We apply a force-free fitting to the magnetic vectors from the MHD simulation to assess how the distortion of the flux rope affects the fitting. In spite of these limitations, force-free fittings, which are straightforward to apply, do provide an important description of a number of parameters, including the radial dimension, orientation and chirality of the ICME.

Riley, Pete↗
NASA NTRS2004

KINEMATIC TREATMENT OF CORONAL MASS EJECTION EVOLUTION IN THE SOLAR WIND

We present a kinematic study of the evolution of coronal mass ejections (CMEs) in the solar wind. Specifically, we consider the effects of (1) spherical expansion and (2) uniform expansion due to pressure gradients between the interplanetary CME (ICME) and the ambient solar wind. We compare these results with an MHD model that allows us to isolate these effects h m the combined kinematic and dynamical effects, which are included in MHD models. They also provide compelling evidence that the fundamental cross section of so-called "force-free" flux ropes (or magnetic clouds) is neither circular or elliptical, but rather a convex-outward, "pancake" shape. We apply a force-free fit to the magnetic vectors from the MHD simulation to assess how the distortion of the flux rope affects the fit. In spite of these limitations, force-free fits, which are straightforward to apply, do provide an important description of a number of parameters, including the radial dimension, orientation, and chirality of the ICME. Subject headings: MHD - solar wind - Sun: activity - Sun: corona - Sun: coronal mass ejections (CMEs) - On-line material color figures Sun: magnetic fields

Riley, Pete↗
NASA NTRS2019

Conceptual Design of a Counter-Rotating Fan System for Distributed Boundary Layer Ingesting Propulsion

The present paper details the design of the counter rotating fans for a Turboelectric Distributed Propulsion (TeDP) system. Sixteen propulsors installed in mail-slot-shape nacelles are embedded on an aerodynamically optimized hybrid wing-body configuration. The hybrid-wing/body (HWB) configuration which was previously designed to satisfy the conditions of trim, longitudinally static stability and specific cargo space is employed as the baseline configuration in pursuing an optimal distributed propulsion system. A set of distributed propulsors is conceptually designed and the collective performance is evaluated against the target thrust mandated by the mission requirements. The concept of the distributed propulsion allows the fan pressure ratio to be around 1.27~1.32 for the target thrust. In addition, further splitting of the fan pressure ratio by using the counter-rotating fans for each slot realizes the target pressure ratio with low tip speed. In the distributed propulsion system, the nature of the flow conditions and/or the thickness of the ingested boundary layer may differ and result in different propulsive reaction of each individual propulsor. The optimization is, thus, approached from both the propulsion system and individual propulsor perspectives. An optimal distribution of the thrust and power output is determined by how the system utilizes each passage's propulsive characteristics and its interaction with the airframe. These system level analysis and optimization are conducted using an actuator disk model to account for the propulsion-airframe integration numerically. With respect to the propulsor level, aerodynamic shape optimizations of the fan blades are performed in a sequential multi-objective optimization process for various design objectives, such as mass flow rate condition, fan pressure ratio, efficiency and the exit flow angle of the fan stage by using a genetic algorithm, NSGA-II. The radial chord distribution, and meanline distribution of the rotors are designed on the circumferentially averaged axi-symmetric inlet profiles and tested on the six inlet profiles from six divided sectors to reckon flow distortion. The performances of the counter rotating fans are, thus, evaluated accordingly for obtaining distortion tolerant fan. The performance of the distributed propulsion system is evaluated by two CFD tools, i.e., a multi-stage turbo-machinery CFD code and one propulsion-airframe integration flow solver coupled with a body-force model. The optimized boundary layer ingestion propulsion system of 16 distributed slots not only reaches the system target thrust, but also delivers a close to 20% fuel saving benefit against its counterpart 12 distributed clean inlet propulsion system.

Boundary-Layer-Ingestion Propulsion↗
NASA NTRS2018

Elliptic-Cylindrical Analytical Flux Rope Model for Magnetic Clouds

In this paper, we present the elliptic-cylindrical analytical flux rope model, which constitutes the first level of complexity above that of a circular-cylindrical geometry. The framework of this series of models was established by Nieves-Chinchilla et al. with the circular-cylindrical analytical flux rope model. The model describes the magnetic flux rope topology with distorted cross section as a possible consequence of the flux rope interaction with the solar wind. In this model, for the first time, a flux rope is completely described by a nonorthogonal geometry. The Maxwell equations can be consistently solved using tensorial analysis, and relevant physical quantities can be derived, such as magnetic fluxes, number of turns, or Lorentz force distribution. The model is generalized in termsof the radial dependence of the poloidal and axial current density components. The circular-cylindrical reconstruction technique has been adapted to the new geometry for a specific case of the model and tested againstan interplanetary coronal mass ejection observed by the Wind spacecraft on 2005 June 12. In this specific case,from the comparative analysis between the circular-cylindrical and elliptic-cylindrical models, the inclusion ofthe cross-section distortion in the 3D reconstruction results in significant changes in the derived axis orientation,size, central magnetic field, magnetic fluxes, and force-freeness. The case studied in this paper exemplifies the useof the model and reconstruction technique developed. Furthermore, the novel mathematical formulation to modelflux ropes in heliophysics paves the way to the inclusion of more complex magnetic field configurations.

CMEs↗
NASA NTRS1991

Three-dimensional analysis of the Pratt and Whitney alternate design SSME fuel turbine

The three dimensional viscous time-mean flow in the Pratt and Whitney alternate design space shuttle main engine fuel turbine is simulated using the average passage Navier-Stokes equations. The migration of secondary flows generated by upstream blade rows and their effect on the performance of downstream blade rows is studied. The present simulation confirms that the flow in this two stage turbine is highly three dimensional and dominated by the tip leakage flow. The tip leakage vortex generated by the first blade persists through the second blade and adversely affects its performance. The greatest mixing of the inlet total temperature distortion occurs in the second vane and is due to the large leakage vortex generated by the upstream rotor. It is assumed that the predominant spanwise mixing mechanism in this low aspect ratio turbine is the radial transport due to the deterministically unsteady vortical flow generated by upstream blade rows. A by-product of the analysis is accurate pressure and heat loads for all blade rows under the influence of neighboring blade rows. These aero loads are useful for advanced structural analysis of the vanes and blades.

Kirtley, K. R.↗
NASA NTRS1981

Structure and origin of cometary nuclei

There is strong evidence that a comet nucleus consists of a single object whose basic structure is Whipple's icy conglomerate. A number of cometary phenomena indicate that the nucleus is a low density, fragile object with a large degree of radial uniformity in structure and composition. Details of the ice-dust pattern are more uncertain. A working model is proposed which is based on theories of accumulation of larger objects from grains. This nucleus is a distorted spherical aggregate of a hierarchy of ice-dust cometesimals. These cometesimals retain some separate identity which lead to comet fragmentation when larger components break off. The outer layers of new comets were modified by cosmic ray irradiation in the Oort Cloud. The evidence for meteorite-comet association is steill controversial. Current dynamical studies do not seem to require a cometary source of meteorites.

Donn, B.↗
NASA NTRS2019

Hybrid Simulation of Solar-Wind-Like Turbulence

We present 2.5D hybrid simulations of the spectral and thermodynamic evolution of an initial state of magnetic field and plasma variables that in many ways represents solar wind fluctuations. In accordance with Helios near-Sun high-speed stream observations, we start with Alfvénic fluctuations along a mean magnetic field in which the fluctuations in the magnitude of the magnetic field are minimized. Since fluctuations in the radial flow speed are the dominant free energy in the observed fluctuations, we include a field-aligned v∥(k⊥) with an k(exp −1) spectrum of velocity fluctuations to drive the turbulent evolution. The flow rapidly distorts the Alfvénic fluctuations, yielding spectra (determined by spacecraft-like cuts) transverse to the field that become comparable to the k∥ fluctuations, as in spacecraft observations. The initial near constancy of the magnetic field is lost during the evolution; we show this also takes place observationally. We find some evolution in the anisotropy of the thermal fluctuations, consistent with expectations based on Helios data. We present 2D spectra of the fluctuations, showing the evolution of the power spectrum and cross-helicity. Despite simplifying assumptions, many aspects of simulations and observations agree. The greatly faster evolution in the simulations is at least in part due to the small scales being simulated, but also to the non-equilibrium initial conditions and the relatively low overall Alfvénicity of the initial fluctuations.

Roberts, D. Aaron↗