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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Modeling and analysis of doubly curved aerobrake truss structures

An aerobrake structural concept featuring a double curved tetrahedral truss support system and hexagonal heat shield panels was modeled and analyzed. Modeling equations for a sphere, cone, and paraboloid were developed for the purpose. Design equation and computer codes were also evolved and employed to determine the total mass of the aerobrake as well as any parameters that had an adverse effect on the total aerobrake mass. These data were used in a point design for a Mars mission aerobrake. A 131-ft diameter aerobrake was found to be viable using the present structural concept (i.e., the total aerobrake mass is not greater than 450,000 lb, which is the attached spacecraft mass). It is also shown that curvature, load point placement, number of load points, number of strut designs, and number of rings all have an effect on the mass of the aerobrake.

Washington, Gregory↗
NASA NTRS2008

2007 Research and Engineering Annual Report

Selected research and technology activities at NASA Dryden Flight Research Center are summarized. These following activities exemplify the Center's varied and productive research efforts: Developing a Requirements Development Guide for an Automatic Ground Collision Avoidance System; Digital Terrain Data Compression and Rendering for Automatic Ground Collision Avoidance Systems; Nonlinear Flutter/Limit Cycle Oscillations Prediction Tool; Nonlinear System Identification Using Orthonormal Bases: Application to Aeroelastic/Aeroservoelastic Systems; Critical Aerodynamic Flow Feature Indicators: Towards Application with the Aerostructures Test Wing; Multidisciplinary Design, Analysis, and Optimization Tool Development Using a Genetic Algorithm; Structural Model Tuning Capability in an Object-Oriented Multidisciplinary Design, Analysis, and Optimization Tool; Extension of Ko Straight-Beam Displacement Theory to the Deformed Shape Predictions of Curved Structures; F-15B with Phoenix Missile and Pylon Assembly--Drag Force Estimation; Mass Property Testing of Phoenix Missile Hypersonic Testbed Hardware; ARMD Hypersonics Project Materials and Structures: Testing of Scramjet Thermal Protection System Concepts; High-Temperature Modal Survey of the Ruddervator Subcomponent Test Article; ARMD Hypersonics Project Materials and Structures: C/SiC Ruddervator Subcomponent Test and Analysis Task; Ground Vibration Testing and Model Correlation of the Phoenix Missile Hypersonic Testbed; Phoenix Missile Hypersonic Testbed: Performance Design and Analysis; Crew Exploration Vehicle Launch Abort System-Pad Abort-1 (PA-1) Flight Test; Testing the Orion (Crew Exploration Vehicle) Launch Abort System-Ascent Abort-1 (AA-1) Flight Test; SOFIA Flight-Test Flutter Prediction Methodology; SOFIA Closed-Door Aerodynamic Analyses; SOFIA Handling Qualities Evaluation for Closed-Door Operations; C-17 Support of IRAC Engine Model Development; Current Capabilities and Future Upgrade Plans of the C-17 Data Rack; Intelligent Data Mining Capabilities as Applied to Integrated Vehicle Health Management; STARS Flight Demonstration No. 2 IP Data Formatter; Space-Based Telemetry and Range Safety (STARS) Flight Demonstration No. 2 Range User Flight Test Results; Aerodynamic Effects of the Quiet Spike(tm) on an F-15B Aircraft; F-15 Intelligent Flight Controls-Increased Destabilization Failure; F-15 Integrated Resilient Aircraft Control (IRAC) Improved Adaptive Controller; Aeroelastic Analysis of the Ikhana/Fire Pod System; Ikhana: Western States Fire Missions Utilizing the Ames Research Center Fire Sensor; Ikhana: Fiber-Optic Wing Shape Sensors; Ikhana: ARTS III; SOFIA Closed-Door Flutter Envelope Flight Testing; F-15B Quiet Spike(TM) Aeroservoelastic Flight Test Data Analysis; and UAVSAR Platform Precision Autopilot Flight Results.

Stoliker, Patrick↗
DOE OSTI2020

Bendable disordered metamaterials for broadband terahertz invisibility

We experimentally demonstrate a bendable cloaking structure composed of obliquely stacked planar metallic shells that individually enclose the objects to be hidden. The ensemble of shells acts as a disordered oblique grating capable of bending along a curved structure and exhibits broadband invisibility from 0.2 to 1.0 THz. Hiding cloaked objects sized hundreds of microns could prevent the detection of certain powders that are sensitive to terahertz waves; such a cloaking structure can also be considered as a shape-changing passageway that transfers the electromagnetic waves without interfering with them. Our approach provides a unique way to achieve broadband electromagnetic invisibility.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Aerobrake construction concepts for the Mars mission

This paper describes a new aerobrake construction concept for the Mars mission, based on the NASA design, which utilizes a truss structure for supporting hexagonally shaped panels used for thermal protection system. Compared to previous designs, the aerobrake geometry in the new concept is modified to include a more accurate doubly-curved structure, and the analysis includes more realistic aerodynamic loads. The structural weight of the aerobrake is reduced by using variable truss and panel cross sections.

Klang, Eric↗
NASA NTRS1987

Large space systems requirements, deployable concepts, and technology issues

This paper summarizes some of the future civil missions requiring large space systems technologies. Antenna, collector, and reflector missions are generalized to define a similar set of system requirements and characteristics. Although many concepts exist for both deployable and space assemblable large structures, four technically mature deployable concepts are reviewed. Two of these concepts are probably applicable to only antenna/collector missions, whereas the other two employ continuous trusses which can be configured for a broad range of planar, linear, or curved structures. Finally, technology problems or needs associated with large deployable systems are reviewed to highlight additional research and development, both analytical and experimental, required to reduce mission risk.

Lovelace, U. M.↗
NASA NTRS1985

Synchronously Deployable Truss

Double-layered truss structure compactly packaged and sychronously deployed. Synchronously deployable truss constructed of two surface layers of struts, arranged in triangles, connected by "tripods" of equal-length core struts. Mechanism powered by passive spring and damped by hydraulic-damping cylinder. When released, spring drives slider linked to core and surface struts. Variety of truss geometries, including curved structures, comtemplated.

Bush, H. G.↗
NASA NTRS1993

Plasma irregularities caused by cycloid bunching of the CRRES G-2 barium release

The Combined Release and Radiation Effects Satellite (CRRES) spacecraft carried a number of barium thermite canisters for release into the upper atmosphere. The barium release labeled G-2 showed evidence of curved irregularities not aligned with the ambient magnetic field B. The newly discovered curved structures can be explained by a process called cycloid bunching. Cycloid bunching occurs when plasma is created by photoionization of a neutral cloud injected at high velocity perpendicular to B. If the injection velocity is much larger than the expansion speed of the cloud, the ion trail will form a cycloid that has irregularities spaced by the product of the perpendicular injection speed and the ion gyroperiod, Images of the solar-illuminated barium ions are compared with the results of a three-dimensional kinetic simulation. Cycloid bunching is shown to be responsible for the rapid generation of both curved and field-aligned irregularities in the CRRES G-2 experiment.

Bernhardt, P. A.↗
NASA NTRS1992

Three-dimensional structure of a curved wake

The effects of streamwise curvature on the 3D structure of a plane wake are studied. Preliminary results indicate that the wake is initially grossly 3D with large spanwise distortions in the mean velocity and Reynolds stress contours. Local extrema distributed in a quasi-periodic manner are seen. The spanwise variations are caused by the presence of relatively strong quadrupoles of mean streamwise vorticity. Further downstream the mean vorticity decays at a rate lower on the unstable side of the wake so that only the unstable side row of vortices persist to the far-field region. As a result, the spanwise distortions and local extrema seem to persist with a relatively slow decay. The effects of curvature are also apparent in the Reynolds stress results. In particular, the shear stress is significantly affected by curvature right from the start such that significantly higher magnitudes are observed on the unstable side. The curved wake clearly develops a very 3D asymmetric structure which shows no signs of reaching an equilibrium state.

Weygandt, J. H.↗
NASA NTRS1975

Compression of contour data through exploiting curve-to-curve dependence

An approach to exploiting curve-to-curve dependencies in order to achieve high data compression is presented. One of the approaches to date of along curve compression through use of cubic spline approximation is taken and extended by investigating the additional compressibility achievable through curve-to-curve structure exploitation. One of the models under investigation is reported on.

Yalabik, N.↗
NASA NTRS1982

4C 18.68 - A QSO with precessing radio jets

High-resolution VLA radio maps at 20 cm and 6 cm wavelengths of the quasar 4C 18.68 reveal an extended halo of about 20 arcsec containing complex curved structures extending east and west from the central source. The central source has a flat spectrum, while the spectrum generally steepens with distance from the center of the structure. The details of the structure and polarization of the emission suggest relativistic ejection in opposing directions by a precessing or rotating double jet with a period of about 50,000 years, consistent with the presence of two interacting massive bodies in the central source.

Gower, A. C.↗
NASA NTRS1983

Reduction of rms-error in shallow faceted large space antennas

This paper examines the potential for reducing root-mean-square surface error in shallow faceted reflectors by replacing flat facets with membrane facets. Exact solutions are obtained for the small lateral deflections of equilateral triangular and rectangular membranes subject to isotropic tension and parabolic edge deflections. These solutions are used to minimize the rms-error between a facet of a shallow paraboloidal surface and its approximating membrane facet. The resulting optimum placements and edge curvatures yield membrane facets which have significantly lower rms-errors than the corresponding best-fit flat facets. The rms-error reductions are about 55 percent for equilateral triangles and 25 percent to 93 percent for rectangles, depending on aspect ratio. The results suggest that the use of membrane facets conforming to curved structural members could yield reflectors with lower rms-error, or comparable error with larger facets and, hence, fewer structural members.

Fichter, W. B.↗
NASA NTRS1989

Measured and predicted root-mean-square errors in square and triangular antenna mesh facets

Deflection shapes of square and equilateral triangular facets of two tricot-knit, gold plated molybdenum wire mesh antenna materials were measured and compared, on the basis of root mean square (rms) differences, with deflection shapes predicted by linear membrane theory, for several cases of biaxial mesh tension. The two mesh materials contained approximately 10 and 16 holes per linear inch, measured diagonally with respect to the course and wale directions. The deflection measurement system employed a non-contact eddy current proximity probe and an electromagnetic distance sensing probe in conjunction with a precision optical level. Despite experimental uncertainties, rms differences between measured and predicted deflection shapes suggest the following conclusions: that replacing flat antenna facets with facets conforming to parabolically curved structural members yields smaller rms surface error; that potential accuracy gains are greater for equilateral triangular facets than for square facets; and that linear membrane theory can be a useful tool in the design of tricot knit wire mesh antennas.

Fichter, W. B.↗
NASA NTRS1989

Interferometric molecular line observations of W51

Observations are presented of the H II region complex in W51 made with a mm interferometer. W51 is a region of massive star formation approx. 7 kpc distant from the sun. This region has been well studied in both the IR and submillimeter, the radio, as well as the maser transitions. These previous observations have revealed three regions of interest: (1) W51MAIN, a know of bright maser emission near two compact H II regions W51e1 and W51e2 (W51MAIN is also the peak of the 400 micron emission indicating that the bulk of the mass is centered there; (2) W51IRS1 is a long curving structure seen at 20 micron and at 2 and 6 cm but not at 400 micron; (3) W51IRS2 (also known as W51NORTH) is another compact H II region slightly offset from an 8 and a 20 micron peak and a collection of masers. Some conclusions are as follows: (1) SO and H(13)CN emission are similar and coincide with outflow activity; (2) HCO+ spectra show evidence for overall collapse of the W51 cloud toward W51MAIN; (3) A previously undetected continuum peak, W51DUST, coincides with the molecular peak H(13)CN-4; and (4) Dust emission at 3.4 mm reveals that about half of the 400 micron emission comes from the ultracompact H II region e2, and the rest from W51e1 and W51DUST.

Rudolph, Alexander↗
NASA NTRS1992

The radio source and bipolar nebulosity in the Seyfert galaxy NGC 3516

Results of radio continuum and optical emission-line observations of the type 1 Seyfert galaxy NGC 3516 are presented. The radio maps reveal an elongated one-sided curved structure, which comprises a series of small-scale 'blobs' and extends up to 4 kpc from the nucleus. This radio structure is aligned and cospatial with one side of the double-sided and highly symmetric Z-shaped emission-line structure. It is argued that these morphological features are associated with a bipolar gaseous outflow from the nucleus of NGC 3516. The radio 'blobs' are elongated roughly perpendicular to the apparent local direction of the outflow, a result which is interpreted in terms of synchrotron emission from outflow-driven shock waves.

Miyaji, Takamitsu↗
NASA NTRS2007

Materials Database Development for Ballistic Impact Modeling

A set of experimental data is being generated under the Fundamental Aeronautics Program Supersonics project to help create and validate accurate computational impact models of jet engine impact events. The data generated will include material property data generated at a range of different strain rates, from 1x10(exp -4)/sec to 5x10(exp 4)/sec, over a range of temperatures. In addition, carefully instrumented ballistic impact tests will be conducted on flat plates and curved structures to provide material and structural response information to help validate the computational models. The material property data and the ballistic impact data will be generated using materials from the same lot, as far as possible. It was found in preliminary testing that the surface finish of test specimens has an effect on measured high strain rate tension response of AL2024. Both the maximum stress and maximum elongation are greater on specimens with a smoother finish. This report gives an overview of the testing that is being conducted and presents results of preliminary testing of the surface finish study.

Pereira, J. Michael↗
NASA NTRS2019

OGLE-2018-BLG-1011Lb,c: Microlensing Planetary System with Two Giant Planets Orbiting a Low-mass Star

We report a multiplanetary system found from the analysis of microlensing event OGLE-2018-BLG-1011, for which the light curve exhibits a double-bump anomaly around the peak. We find that the anomaly cannot be fully explained by the binary-lens or binary-source interpretations and its description requires the introduction of an additional lens component. The 3L1S (three lens components and a single source) modeling yields three sets of solutions, in which one set of solutions indicates that the lens is a planetary system in a binary, while the other two sets imply that the lens is a multiplanetary system. By investigating the fits of the individual models to the detailed light curve structure, we find that the multiple-planet solution with planet-to-host mass ratios ∼9.5 X 10(exp −3) and ∼15 X 10(eap −3) are favored over the other solutions. From the Bayesian analysis, we find that the lens is composed of two planets with masses 1.8 (sup +3.4, sub -1.1) M(J) and 2.8 (sup +5.8, sub -1.7) M(J) around a host with a mass 0.18 (sup +0.33,sub - 0.10) M(ʘ) and located at a distance 7.1(sup +1.1, sub -1.5) kpc. The estimated distance indicates that the lens is the farthest system among the known multiplanetary systems. The projected planet–host separations are a(⊥,2) = 1.8 (sup +2.1, sub -1.5)au (0.8 (sup +0.9,sub -0.6 au) and a(⊥,3) = 0.8 (sup +0.9, sub -0.6)au , where the values of a(⊥,2) inside and outside the parenthesis are the separations corresponding to the two degenerate solutions, indicating that both planets are located beyond the snow line of the host, as with the other four multiplanetary systems previously found by microlensing.

Cheongho Han↗
NASA NTRS1991

Structural evaluation of curved stiffened composite panels fabricated using a THERM-Xsm process

The use of composites in aircraft structures is often limited by material and manufacturing costs which, for some designs and applications, are prohibitively high. To increase the frequency of application of composites in primary airframe components alternative manufacturing processes are sought that reduce cost and/or enhance structural efficiency. One alternative process involves the use of THERM-Xsm as the pressure transfer medium during autoclave curing. THERM-Xsm, a silicon-based flow able polymer which behaves like a liquid under autoclave presssure, transmits quasi-hydrostatic pressure to all contacting surfaces of the part to be cured. Once the autoclave pressure is relieved, THERM-Xsm reverts back to the powdery solid state and can be reused many times. The THERM-Xsm process to be evaluated is depicted and consists of (1) enclosing the tool and part to be cured by a set of frames that create a box, (2) pouring THERM-Xsm powder onto the part and filling the box, and (3) placing a vacuum bag over the box assembly. In this program, a separating non-porous film (Teflon) was placed between the part to be cured and THERM-Xsm powder to avoid any contamination. The use of THERM-Xsm has two significant advantages over conventional manufacturing procedures. First, it eliminates complicated hard tooling since it guarantees uniform pressure transfer and thus, good compaction at complex structural details (such as frame-stiffener intersections and corners). Second, it greatly simplifies vacuum bagging, since once the part to be cured is covered by THERM-Xsm powder, the vacuum bag need only conform to a relatively flat shape reducing significantly the number of pleats required. A program is on-going at Sikorsky Aircraft to evaluate the structural performance of complex composite fuselage structures made with this THERM-Xsm process and to quantify the impact of THERM-Xsm on manufacturing labor hours and cost. The program involves fuselage panel optimization analysis, a building block test program where structural details representative of the full-scale article are analyzed and tested, and static and fatigue test/analysis of the full-scale test articles. The main results of this program are reported.

Kassapoglou, Christos↗
NASA NTRS2012

Effect of Particle Damping on an Acoustically Excited Curved Vehicle Panel Structure with varied Equipment Assemblies

Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from trials to determine how effective use of these dampers might be for equipment mounted to a curved orthogrid vehicle panel. Trends for damping are examined for variations in damper fill level, component mass, and excitation energy. A significant response reduction at the component level would suggest that comparatively small, thoughtfully placed, particle dampers might be advantageously used in vehicle design. The results of this test will be compared with baseline acoustic response tests and other follow-on testing involving a range of isolation and damping methods. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results.

Parsons, David↗