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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 163 records · Page 9
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NASA NTRS2002

Acoustic and Laser Doppler Anemometer Results for Confluent and 12-Lobed E(exp 3) Mixer Exhaust Systems for Subsonic Jet Noise Reduction

The research described in this report has been funded by NASA Glenn Research Center as part of the Advanced Subsonic Technologies (AST) initiative. The program operates under the Large Engine Technologies (LET) as Task Order #3 1. Task Order 31 is a three year research program divided into three subtasks. Subtask A develops the experimental acoustic and aerodynamic subsonic mixed flow exhaust system databases. Subtask B seeks to develop and assess CFD-based aero-acoustic methods for subsonic mixed flow exhaust systems. Subtask B relies on the data obtained from Subtask A to direct and calibrate the aero-acoustic methods development. Subtask C then seeks to utilize both the aero-acoustic data bases developed in Subtask A and the analytical methods developed in Subtask B to define improved subsonic mixed-flow exhaust systems. The mixed flow systems defined in Subtask C will be experimentally demonstrated for improved noise reduction in a scale model aero-acoustic test conducted similarly to the test performed in Subtask A. The overall object of this Task Order is to develop and demonstrate the technology to define a -3EPNdB exhaust system relative to 1992 exhaust system technology.

Salikuddin, M.↗
NASA NTRS2001

Status of the Direct Data Distribution (D(exp 3)) Experiment

NASA Glenn Research Center's Direct Data Distribution (D3) project will demonstrate an advanced, high-performance communications system that transmits information from an advanced technology payload carried by a NASA spacecraft in low Earth orbit (LEO) to a small receiving terminal on Earth. The space-based communications package will utilize a solid-state, K-band phased-array antenna that electronically steers the radiated energy beam toward a low-cost, tracking ground terminal, thereby providing agile, vibration-free, electronic steering at reduced size and weight with increased reliability. The array-based link will also demonstrate new digital processing technology that will allow the transmission of substantially increased amounts of latency-tolerant data collected from the LEO spacecraft directly to NASA field centers, principal investigators, or into the commercial terrestrial communications network. The technologies demonstrated by D3 will facilitate NASA's transition from using Government-owned communication assets to using commercial communication services. The hardware for D3 will incorporate advanced technology components developed under the High Rate Data Delivery (HRDD) Thrust Area of NASA's Office of Aerospace Technology Space Base Program at Glenn's Communications Technology Division. The flight segment components will include the electrically steerable phased-array antenna, which is being built by the Raytheon System Corporation and utilizes monolithic microwave integrated circuit (MMIC) technology operating at 19.05 GHz; and the digital encoder/modulator chipset, which uses four-channel orthogonal frequency division multiplexing (OFDM). The encoder/modulator will use a chipset developed by SICOM, Inc., which is both bandwidth and power efficient. The ground segment components will include a low-cost, open-loop tracking ground terminal incorporating a cryoreceiver to minimize terminal size without compromising receiver capability. The project is planning to hold a critical design review in the second quarter of fiscal year 2002.

Wald, Lawrence↗
NASA NTRS2009

The Dispersion Relation for the 1/sinh(exp 2) Potential in the Classical Limit

The dispersion relation for the inverse hyperbolic potential is calculated in the classical limit. This is shown for both the low amplitude phonon branch and the high amplitude soliton branch. It is shown these results qualitatively follow that previously found for the inverse squared potential where explicit analytic solutions are known.

Campbell, Joel↗
NASA NTRS2011

High Heat Flow from Enceladus' South Polar Region Measured using 10-600/cm(exp -1) Cassini/CIRS Data

Analysis of 2008 Cassini Composite Infrared Spectrometer (CIRS) 10 to 600/cm thermal emission spectra of Enceladus shows that for reasonable assumptions about the spatial distribution of the emission and the thermophysical properties of the solar-heated background surface, which are supported by CIRS observations of background temperatures at the edge of the active region, the endogenic power of Enceladus' south polar terrain is 15.8 +/- 3.1 GW. This is significantly higher than the previous estimate of 5.8 +/- 1.9 GW. The new value represents an improvement over the previous one, which was derived from higher wave number data (600 to 1100/cm-I) and was thus only sensitive to high-temperature emission. The mechanism capable of producing such a high endogenic power remains a mystery and challenges the current models of proposed heat production.

Howett, C. J. A.↗
NASA NTRS2012

Discovery of Small-Scale Spiral Structures in the Disk of SAO 206462 (HD 135344B)(exp 1): Implications for the Physical State of the Disk from Spiral Density Wave Theory

We present high-resolution, H-band, imaging observations, collected with Subaru /HiCIAO, of the scattered light from the transitional disk around SAO 206462 (HD 1353448). Although previous sub-mm imagery suggested the existence of the dust-depleted cavity at r <= 46 AU, our observations reveal the presence of scattered light components as close as O".2 (approx 28 AU) from the star. Moreover , we have discovered two small-scale spiral structures lying within 0".5 (approx 70 AU). We present models for the spiral structures using the spiral density wave theory, and derive a disk aspect ratio of h approx. 0.1, which is consistent with previous sub-mm observations. This model can potentially give estimates of the temperature and rotation profiles of the disk based on dynamical processes. independently from sub-nun observations. It also predicts the evolution of the spiral structures, which can be observable on timescales of 10-20 years, providing conclusive tests of the model. While we cannot uniquely identify the origin of these spirals, planets embedded in the disk may be capable of exciting the observed morphology. Assuming that this is the case, we can make predictions on the locations and, possibly, the masses of the unseen planets. Such planets may be detected by future multi-wavelengths observations,

Muto, T.↗
NASA NTRS2012

Preliminary Modeling of CH3D From 4000 to 4550 cm (exp-1)

A new study of 12CH3D line positions and intensities was performed for the upper portion of the Enneadecad polyad between 4000 and 4550/cm. For this, FTIR spectra were recorded with D-enriched methane samples (at 80 K with a Bruker 125 IFS at 0.005/cm resolution and at 291 K with the McMath-Pierce FTS at 0.011/cm resolution, respectively). Line positions and intensities were retrieved by least square curve-fitting procedures and analyzed using the effective Hamiltonian and the effective dipole moment expressed in terms of irreducible tensor operators adapted to symmetric top molecules. Initially, only the cold spectrum was used to identify quantum assignments and predict 12CH3D relative intensities in this region. To assign higher quanta up to J equal 14, additional line positions and intensities were obtained from two room temperature spectra. In the final stage, measured intensities from both the cold and the room temperature data were normalized to corresponding values at 296 K and then averaged. Combining the two temperature datasets confirmed the assumed quantum assignments and also demonstrated the relative accuracies to be better than 70.0002/cm for line positions and at least +/-6% for intensities so that approx.1160 features were selected. Including additional assignments from the room temperature spectra alone permitted 1362 line intensities of 11 bands (involving 23 vibrational symmetry components) to be reproduced with an RMS of 9%. Over 4085 selected positions for 12 bands were modeled to 0.008/cm. Nevertheless a number of known assignments could not be modeled to within our experimental precisions. More work is needed to obtain a complete characterization of this complex polyad.

Nikitin, A. V.↗
NASA NTRS2013

High-Accuracy Quartic Force Field Calculations for the Spectroscopic Constants and Vibrational Frequencies of 1(exp 1)A' l-C3H(-): A Possible Link to Lines Observed in the Horsehead Nebula PDR

It has been shown that rotational lines observed in the Horsehead nebula photon-dominated-region (PDR) are probably not caused by l-C3H+, as was originally suggested. In the search for viable alternative candidate carriers, quartic force fields are employed here to provide highly accurate rotational constants, as well as fundamental vibrational frequencies, for another candidate carrier: 1 (sup 1)A' C3H(−). The ab initio computed spectroscopic constants provided in this work are, compared to those necessary to define the observed lines, as accurate as the computed spectroscopic constants for many of the known interstellar anions. Additionally, the computed D-eff for C3H(−) is three times closer to the D deduced from the observed Horsehead nebula lines relative to l-C3H(+). As a result, 1 (sup 1)A' C3H(−). is a more viable candidate for these observed rotational transitions and would be the seventh confirmed interstellar anion detected within the past decade and the first C(sub n)H(−) molecular anion with an odd n.

Horsehead nebula↗
NASA NTRS2014

Calculation of State Specific Rate Coefficients for Non-Equilibrium Hypersonics Applications: from H(Psi) = E(Psi) to k(T) = A *exp(-E(sub a)/RT)

Development of High-Fidelity Physics-Based Models to describe hypersonic flight through the atmospheres of Earth and Mars is underway at NASA Ames Research Center. The goal is to construct chemistry models of the collisional and radiative processes that occur in the bow shock and boundary layers of spacecraft during atmospheric entry that are free of empiricism. In this talk I will discuss our philosophy and describe some of our progress. Topics to be covered include thermochemistry, internal energy relaxation, collisional dissociation and radiative emission and absorption. For this work we start by solving the Schrodinger equation to obtain accurate interaction potentials and radiative properties. Then we invoke classical mechanics to compute state-specific heavy particle collision cross sections and reaction rate coefficients. Finally, phenomenological rate coefficients and relaxation times are determined from master equation solutions.

aerothermodynamics↗
NASA NTRS2014

Can Eccentric Debris Disks Be Long-lived? A First Numerical Investigation and Application to Zeta(exp 2) Reticuli

Context. Imaging of debris disks has found evidence for both eccentric and offset disks. One hypothesis is that they provide evidence for massive perturbers, for example, planets or binary companions, which sculpt the observed structures. One such disk was recently observed in the far-IR by the Herschel Space Observatory around Zeta2 Reticuli. In contrast with previously reported systems, the disk is significantly eccentric, and the system is several Gyr old. Aims. We aim to investigate the long-term evolution of eccentric structures in debris disks caused by a perturber on an eccentric orbit around the star. We hypothesise that the observed eccentric disk around Zeta2 Reticuli might be evidence of such a scenario. If so, we are able to constrain the mass and orbit of a potential perturber, either a giant planet or a binary companion. Methods. Analytical techniques were used to predict the effects of a perturber on a debris disk. Numerical N-body simulations were used to verify these results and further investigate the observable structures that may be produced by eccentric perturbers. The long-term evolution of the disk geometry was examined, with particular application to the Zeta2 Reticuli system. In addition, synthetic images of the disk were produced for direct comparison with Herschel observations. Results. We show that an eccentric companion can produce both the observed offsets and eccentric disks. These effects are not immediate, and we characterise the timescale required for the disk to develop to an eccentric state (and any spirals to vanish). For Zeta2 Reticuli, we derive limits on the mass and orbit of the companion required to produce the observations. Synthetic images show that the pattern observed around Zeta2 Reticuli can be produced by an eccentric disk seen close to edge-on, and allow us to bring additional constraints on the disk parameters of our model (disk flux and extent). Conclusions. We conclude that eccentric planets or stellar companions can induce long-lived eccentric structures in debris disks. Observations of such eccentric structures thus provide potential evidence of the presence of such a companion in a planetary system. We considered the specific example of Zeta2 Reticuli, whose observed eccentric disk can be explained by a distant companion (at tens of AU) on an eccentric orbit (ep greater than approx. 0.3).

planetary systems↗
NASA NTRS1961

Friction, Wear, and Evaporation Rates of Various Materials in Vacuum to 10(exp -7) mm Hg

The requirements for bearings and seals to operate in the environment of space dictate a new area for lubrication research. The low ambient pressures encountered in space can be expected to influence the behavior of oil, grease, and solid-film lubricants. The property of these materials most significantly affected by low ambient pressures is the evaporation rate. Various investigators have therefore measured the evaporation rates of oils and greases in vacuum as one method of establishing their relative merit for space applications (1-3). The results of this work have given some indication as to the oils and greases with the greatest stability at reduced ambient pressures. Only limited experimental work, however, has been reported in the literature for inorganic solids and soft metals which have potential use as solid lubricant films or coatings for hard alloy substrates [e.g. Reference ( 4 )]. In general, the evaporation rates of these materials would be lower than those of oils and greases. These films might therefore be very attractive as lubricants for high vacuum service.

Buckley, Donald H.↗
NASA NTRS2020

TESS Science Data Products Description Document: EXP-TESS-ARC-ICD-0014 Rev F

This document discusses data product formats that are produced primarily by the TESS Science Processing Operations Center (SPOC) at NASA Ames Research Center. Data products are sent to the TESS Science Operations Center (SOC) at MIT where they are disseminated to the Mikulski Archive for Space Telescopes (MAST) and the TESS Science Office (TSO).

TESS↗
NASA NTRS2020

Thermal Analysis, Compressibility, and Decomposition of Synthetic Bastnäsite-(La) to Lanthanum Oxyfluoride

Understanding basic material properties of rare earth element (REE) bearing minerals such as their phase stability and equations of state can assist in understanding how economically viable deposits might form. Bastnäsite is the most commonly mined REE bearing mineral. We synthesized the lanthanum-fluoride end member, bastnäsite-(La) (LaCO3F), and investigated its thermal behavior and decomposition products from 298 K to 1173 K under ambient pressure conditions through thermogravimetric analysis, differential scanning calorimetry, evolved gas analysis, and high temperature powder X-ray diffraction. We also investigated the compressibility of bastnäsite-(La) via single crystal X-ray diffraction in diamond anvil cells at an ambient temperature up to 11.3 GPa and from 4.9 GPa to 7.7 GPa up to 673 K. At ambient pressure, bastnäsite-(La) was stable up to 598 K in air, where it decomposed into CO2 and tetragonal γ-LaOF. Above 948 K, cubic α-LaOF is stable. High temperature X-ray diffraction data were used to fit the Fei thermal equation of state and the thermal expansion coefficient α(sub 298) for all three materials. Bastnäsite-(La) was fit from 298 K to 723 K with V(sub 0) = 439.82 Å(exp 3), α(sub 298) = 4.32 × 10(exp -5) K(exp -1), a(sub 0) = −1.68 × 10(exp -5) K(exp -1), a(sub 1) = 8.34 × 10(exp -8) K(exp -1), and a(sub 2) = 3.126 K(exp -1). Tetragonal γ-LaOF was fit from 723 K to 948 K with V(sub 0) = 96.51 Å(exp 3), α(sub 298) = 2.95×10(exp -4) K(exp -1), a(sub 0) = −2.41×10(exp -5) K(exp -1), a(sub 1) = 2.42×10(exp -7) K(exp -1), and a(sub 2) = 41.147 K(exp -1). Cubic α-LaOF was fit from 973 K to 1123 K with V(sub 0) = 190.71 Å(exp 3), α(sub 298) = −1.12×10(exp -5) K(exp -1), a(sub 0) = 2.36×10(exp -4) K(exp -1), a(sub 1) = −1.73 × 10(exp -7) K(exp -1), and a(sub 2) = −17.362 K(exp -1). An ambient temperature third order Birch–Murnaghan equation of state was fit with V(sub 0) = 439.82 Å(exp 3), K(sub 0) = 105 GPa, and K’ = 5.58.

Bastnäsite↗
NASA NTRS1998

Midcourse Space Experiment Spectra of the Orion Nebula and the Implications for Abundances in the Interstellar Medium

Spectra of the Orion Nebula were obtained with the Midcourse Space Experiment Spirit 3 interferometer from 370 to 2000 cm(exp -1) with 2 cm(exp -1) resolution in a 6' x 9' field of view (FOV) in 1996 November. Lines were detected of [S III] 534.4 cm(exp -1), [Ne III] 642.9 cm(exp -1), [Ne II] 780.4 cm(exp -1), [S IV] 951.4 cm(exp -1), [Ar III] 1112.2 cm(exp -1), [Ar II] 1431.6 cm(exp -1), H (7-6) 808.3 cm(exp -1), H (8-6) 1332.9 cm(exp -1), H (6-5) 1340.5 cm(exp -1), H2(S1) 587.0 cm(exp -1), H2(S2) 814.4 cm(exp -1), H2(S3) 1034.7 cm(exp -1), H2(S4) 1246.1 cm(exp -1), and H2(S5) 1447.3 cm(exp -1). The following abundances were determined from these lines: Ne/H = 9.9 +/- 1.1 x 10(exp -5), S/H = 8.1 +/- 1.1 x 10(exp -6), and Ar/H = 2.5 +/- 0.2 x 10(exp -6). These abundances are all less than solar and confirm that the Sun is overabundant in heavy elements without the need for correction for the composition of interstellar dust. The low sulfur abundance compared with solar is an indication that a significant amount of the sulfur in Orion is in dust grains. The FOV-averaged molecular hydrogen column density is approximately 1.6 x 10(exp 20) cm(exp -2) for an excitation temperature of approximately 670 K and an extinction correction corresponding to an optical depth of 1.5 at 9.7 micrometers. The unidentified infrared emission features at 6.2, 7.7, 8.6, 11.3, and 12.7 micrometers, attributable to polycyclic aromatic hydrocarbons, were also detected. A prominent, broad silicate feature centered near 18 micrometer and additional weak features were detected and are discussed.

Simpson, J. P.↗