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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 1,765 records · Page 98
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NASA NTRS2017

Development of Models for Disk-Gap-Band Parachutes Deployed Supersonically in the Wake of a Slender Body

The Advanced Supersonic Parachute Inflation Research and Experiments (ASPIRE) project will investigate the supersonic deployment, inflation, and aerodynamics of Disk- Gap-Band (DGB) parachutes in the wake of a slender body. The parachutes will be full-scale versions of the DGBs used by the Mars Science Laboratory in 2012 and planned for NASA’s Mars 2020 project and will be delivered to targeted deployment conditions representative of flight at Mars by sounding rockets launched out of NASA’s Wallops Flight Facility. The parachutes will be tested in the wake of a slender payload whose diameter is approximately a sixth that of entry capsules used for Mars missions. Models of the deployment, inflation, and aerodynamic performance of the parachutes are necessary to design key aspects of the experiment, including: determining the expected loads and applicable margins on the parachute and payload; guiding sensor selection and placement; evaluating the vehicle trajectory for targeting, range safety, and recovery operations. In addition, knowledge of the differences in the behavior of the parachutes in the wake of slender and blunt bodies is required in order to interpret the results of the sounding rocket experiment and determine how they relate to expected performance behind blunt bodies at Mars. However, modeling the performance of a supersonic DGB in the wake of a slender body is challenging due to the scarcity of historical test data and modeling precedents. This paper describes the models of the aerodynamic performance of DGBs in supersonic slender-body wakes being developed for the ASPIRE sounding rocket test campaign. Development of these models is based on the four available flight tests of DGBs deployed in supersonic slender-body wakes as well as on data from past flight and wind-tunnel experiments of DGBs deployed in the wake of blunt bodies, on the reconstructed at-Mars DGB performance during past missions, and on computational fluid dynamics simulations. Simulations of the wakes of blunt and slender bodies in supersonic flow have been conducted in order to investigate the differences in the flowfields encountered by parachutes deployed in both wake types. The simulations have allowed the project to investigate the fundamental differences between the sounding rocket tests and the flight of a DGB during a Mars mission and to assess the limitations of the sounding rocket test architecture for evaluating flight performance at Mars.

Clark, Ian G.↗
NASA NTRS2020

SCExAO/CHARIS High-contrast Imaging of Spirals and Darkening Features in the HD 34700 A Protoplanetary Disk

We present Subaru/SCExAO+Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) broadband (JHK-band) integral field spectroscopy of HD 34700 A. CHARIS data recover HD 34700 A's disk ring and confirm multiple spirals discovered by Monnier et al. We set limits on substellar companions of ∼12 MJup at 0.″3 (in the ring gap) and ∼5 M(Jup) at 0."75 (outside the ring). The data reveal darkening effects on the ring and spiral, although we do not identify the origin of each feature such as shadows or physical features related to the outer spirals. Geometric albedos converted from the surface brightness suggest a greater scale height and/or prominently abundant submicron dust at position angles between ∼45° and 90°. Spiral fitting resulted in very large pitch angles (∼30°–50°); a stellar flyby of HD 34700 B or infall from a possible envelope is perhaps a reasonable scenario to explain the large pitch angles.

Taichi Uyama↗
NASA NTRS2020

Demonstration of Deployment Accuracy of the Starshade Inner Disk Subsystem

We present experimental results that demonstrate the required in-plane deployment accuracy of the starshade Inner Disk Subsystem (IDS). This effort was to address Milestone 7C of the Starshade Technology Activity S5, which requires that the in-plane deployment accuracy of the petal interfaces on the IDS be within +/-300um. A full-scale 10m-diameter IDS prototype was constructed. This prototype comprised a medium-fidelity perimeter truss, medium-fidelity spokes, and a low-fidelity optical shield (OS). The testbed also included gravity compensation systems and a laser tracker metrology system. The post-processed measurement uncertainties of the laser tracker were less than 30um at the 3 sigma level. Design, engineering and fabrication of these components was done by JPL, Tendeg, and Roccor. Testing was performed at the Tendeg facility in Louisville, Colorado. The IDS prototype was deployed 22 times and the locations of petal interfaces on the IDS were measured after each deployment. Based on this data, tolerance intervals were calculated that would contain 99.73% of future deployment accuracy errors with 90% confidence. These tolerance intervals are conservative estimates for 3 sigma bounds. The tolerance intervals for the three pertinent error components were found to be within the required allocations, with at least 19% margin.

Turse, Dana↗
NASA NTRS2021

Multiwavelength Observations of the RV Tauri Variable System U Monocerotis: Long-term Variability Phenomena That Can Be Explained by Binary Interactions with a Circumbinary Disk

We present an X-ray through submillimeter observations of the classical RV Tauri(RVb-type)variable U Mon, apost-asymptotic giant branch(AGB)binary with a circumbinary disk(CBD). Our SMA observations indicate aCBD diameter of550 au. Our XMM-Newton observations make U Mon thefirst RV Tauri variable detected inX-rays. The X-ray emission is characteristic of a hot plasma(∼10 MK), withLX=5×1030erg s−1, and weconsider its possible origin from U Mon, its companion, and/or binary system interactions. Combining DASCHand AAVSO data, we extend the time-series photometric baseline back to the late 1880s andfind evidence thatU Mon has secular changes that appear to recur on a timescale of∼60 yr, possibly caused by a feature in the CBD.From literature radial velocities wefind that the binary companion is a∼2MeA-type main-sequence star. Theorientation of the binary’s orbit lies along our line of sight(ω=95°), such that apastron corresponds to photometricRVb minima, consistent with the post-AGB star becoming obscured by the near side of the CBD. In addition, wefind the size of the inner-CBD hole(∼4.5–9au)to be comparable to the binary separation, implying that one orboth stars may interact with the CBD at apastron. The obscuration of the post-AGB star implicates the companionas the likely source of the enhanced Hαobserved at RVb minima and of the X-ray emission that may arise fromaccreted material.

Laura D Vega↗
NASA NTRSDate not supplied

Latest Results from NASA Ames’ COSmIC and Optical Constants Facility (OCF): Determining Optical Constants for Titan, Pluto and Protoplanetary Disks Applications

The NASA Ames COsmic SImulation Chamber (COSmIC) is a unique experimental facility that can be used, among many applications, to produce solid particles from gas phase molecular precursors at low temperature (150 K) using a plasma discharge to induce the chemistry in the stream of a free jet expansion. The choice of the initial gas mixture used to produce the solid sample allows the simulation of either cold planetary atmospheres like Titan or Pluto (with N2/CH4-based initial mixtures), or circumstellar environments (with Ar/CxHy-based initial mixtures). The Ames Optical Constants Facility (OCF) allows the determination of optical constants covering a broad wavelength range with high spectral resolution for solid materials, analogs of organic refractory materials formed in planetary and astrophysical environments. The core of the OCF is a Fourier transform infrared (FTIR) spectrometer that allows the continuous characterization of solid samples in the visible to far-infrared (FIR) range (0.59–200 μm, 16,950–50 cm−1). Modeling of the laboratory measurements conducted with the OCF allows the determination of accurate optical constants, n and k, over the full vis-FIR range. Here we present the latest results of two studies that combined (1) experiments performed with COSmIC to produce analogs of aerosols forming in Titan’s atmosphere and analogs of cosmic grains forming in circumstellar envelops, and (2) the characterization of these analogs with the OCF to provide the real and imaginary parts of their refractive indices, n + ik, to the community, from the visible to the FIR. These optical constants can be used as critical input parameters in radiative transfer, atmospheric and reflectance models to interpret observational data of, e.g., Titan’s atmosphere and protoplanetary disks. Providing optical constants for various materials of different compositions allows to explore a broad range of composition by simulating mixtures of materials. We also present a new project to produce analogs of Pluto’s atmospheric aerosols with COSmIC and determine their optical constants with OCF, to be used in reflectance spectra models for the interpretation of New Horizons observations of Lowell Regio, Sputnik Planitia and Cthulhu.

COsmic SImulation Chamber (COSmIC)↗
NASA NTRS2021

Effect of Broaching Machining Parameters, Residual Stresses and Cold Work on Fatigue Life of Ni-based Turbine Disk P/M Alloy at 650°C

A study was performed to examine the effect of various broaching machining parameters on high temperature fatigue lives of a nickel-based Low Solvus High Refractory (LSHR) powder metallurgy disk alloy. The work was done to gain a better understanding of the effect of various broaching variables on the integrity and the durability of these fracture critical components. The influence of tool wear and broaching speed were examined in terms of their effect on residual stresses, cold work and surface roughness. These variables were shown to have a substantial effect on fatigue lives and the failure mode. The relationships between these parameters and fatigue crack initiation mechanisms are detailed. Statistical analyses evaluating these relationships are presented.

fatigue↗
NASA NTRS2021

Modeling Magnetic Disk Wind State Transitions in Black Hole X-Ray Binaries

We analyze three prototypical black hole X-ray binaries, 4U 1630–472, GRO J1655–40, and H1743–322, in an effort to systematically understand the intrinsic state transition of the observed accretion disk winds between wind-on and wind-off states by utilizing state-of-the-art Chandra/HETGS archival data from multi-epoch observations. We apply our magnetically driven wind models in the context of magnetohydrodynamic(MHD)calculations to constrain(1)their global density slope(p),(2)their density (n17) at the foot point of the inner most launching radius, and(3)the abundances of heavier elements(AFe,S,Si). Incorporating the MHD winds into xstar photoionization calculations in a self-consistent manner, we create a library of synthetic absorption spectra given the observed X-ray continua. Our analysis clearly indicates a characteristic bimodal transition of multi-ion X-ray winds; i.e., the wind density gradient is found to steepen(fro mp∼1.2–1.4 to∼1.4–1.5)while its density normalization declines as the source transitions from the wind-onto the wind-off state. The model implies that the ionized wind remains physically present even in the wind-off state, despite its apparent absence in the observed spectra. Super solar abundances for heavier elements are also favored. Our global multi-ion wind models, taking into account soft X-ray ions as well as Fe K absorbers, show that the internal wind condition plays an important role in wind transitions besides photoionization changes. Simulated XRISM/Resolve and Athena/X-IFU spectra are presented to demonstrate a high fidelity of the multi-ion wind model for a better understanding of these powerful ionized winds in the coming decades

Keigo Fukumura↗
NASA NTRS2022

A Census of Stars and Disks in Corona Australis

We have performed a census of the young stellar populations near the Corona Australis molecular cloud using photometric and kinematic data from several sources, particularly Gaia EDR3, and spectroscopy of hundreds of candidate members. We have compiled a catalog of 393 members of Corona Australis, (39 at >M6), 293 (36) of which are spectroscopically classified for the first time in this work. We find that Corona Australis can be described in terms of two stellar populations, a younger one (a few megayears) that is partially embedded in the cloud (the Coronet Cluster) and an older one (∼15 Myr) that surrounds and extends beyond the cloud (Upper Corona Australis). These populations exhibit similar space velocities, and we find no evidence for distinct kinematic populations in Corona Australis, in contrast to a recent study based on Gaia DR2. The distribution of spectral types in Corona Australis reaches a maximum at M5 (∼0.15 M⊙), indicating that the initial mass function has a similar characteristic mass as other nearby star-forming regions. Finally, we have compiled mid-infrared photometry from the Wide-field Infrared Survey Explorer and the Spitzer Space Telescope for the members of Corona Australis, and we have used those data to identify and classify their circumstellar disks. Excesses are detected for 122 stars, one-third of which are reported for the first time in this work.

T L Esplin↗
NASA NTRS2023

Evidence for Turbulent Concentration in Particle-Laden Midplane Layers of Planet-Forming Disks: Preliminary Findings

The formation of the first planetesimals during the first million years of the solar nebula remains a vexing problem. The Streaming Instability (SI) is the leading candidate mechanism that offers a route to form 100 km objects from mm-sized grains, but it appears to not be strongly active based on recent findings [1]. The idea of turbulent concentration offers a possible alternate route to forming these bodies. Is there evidence for this process in bonafide 3D disk models of particle-gas dynamics?

O M Umurhan↗