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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

The brightness of Jupiter's satellite Io following emergence from eclipse - Selected observations, 1981-1989

Io's brightness was monitored following emergence from eclipse by Jupiter on 14 occasions during the Jupiter apparitions from 1981 to 1989 and no instance is found of what has been called posteclipse brightening. If all the observations are averaged, a 2 percent effect cannot be ruled out; however, this effect is also the size of the rms errors of the summed data set. If condensation followed by sublimation of SO2 frost is hypothesized to be the mechanism which causes posteclipse brightening, then solar insolation alone may not be sufficient to remove an optically thick layer of SO2 frost in the time required to conform with the positive reports of posteclipse brightening in the literature. An additional source of energy is required, such as warming caused by the impact of magnetospheric particles as they dissipate the energy of their motion into Io's surface.

Nelson, Robert M.↗
NASA NTRS1991

Impact experiments. III - Catastrophic fragmentation of aggregate targets and relation to asteroids

An experimental study is conducted of collisions employing artificial aggregates as targets, in order to ascertain the fragmentation characteristics of weakly bonded bodies that consist of stronger constituent particles, such as loosely aggregated planetesimals. It is established that weakly bonded aggregate bodies may exhibit unexpectedly high impact strengths due to constituent particles' energy dissipation. The cumulative size distributions of fragments that are larger than the constituent grains form power-law segments resembling those formed by the fragmentation of homogeneous targets.

Ryan, Eileen V.↗
NASA NTRS2005

Fluctuations in Conjunction Miss Distance Projections as Time Approaches Time of Closest Approach

A responsibility of the Trajectory Operations Officer is to ensure that the International Space Station (ISS) avoids colliding with debris. United States Space Command (USSPACECOM) tracks and catalogs a portion of the debris in Earth orbit, but only objects with a perigee less than 600 km and a radar cross section (RCS) greater than 10 cm-objects that, in fact, represent only a small fraction of the objects in Earth orbit. To accommodate for this, the ISS uses shielding to protect against collisions with smaller objects. This study provides a better understanding of how quickly, and to what degree, USSPACECOM projections tend to converge to the final, true miss distance. The information included is formulated to better predict the behavior of miss distance data during real-time operations. It was determined that the driving components, in order of impact on miss distance fluctuations, are energy dissipation rate (EDR), RCS, and inclination. Data used in this analysis, calculations made, and conclusions drawn are stored in Microsoft Excel log sheets. A separate log sheet, created for each conjunction, contains information such as predicted miss distances, apogee and perigee of debris orbit, EDR, RCS, inclination, tracks and observations, statistical data, and other evaluation/orbital parameters.

Christian, John A., III↗
NASA NTRS2022

The Lower Thermospheric Winter-To-Summer Meridional Circulation: 1: Driving Mechanism

In this study, the mechanism driving the narrow lower-thermospheric winter-to-summer meridional circulation is thoroughly investigated for the first time using the Specified Dynamics configuration runs of the Whole Atmosphere Community Climate Model eXtended (SD-WACCMX) simulations and the TIMED Doppler Interferometer (TIDI) observations. The mean meridional circulation in the SD-WACCMX is qualitatively consistent with the TIDI measurements, though the magnitude in the SD-WACCMX is about 50% weaker. The lower-thermospheric winter-to-summer circulation is mainly driven by the resolved wave forcing, including the tides and internally generated inertia gravity waves (GWs). The momentum forcing from the parameterized sub-grid scale GWs is not as significant as the resolved wave forcing in driving the lower-thermospheric meridional circulation. The GW parameterization scheme in the SD-WACCMX only includes GWs with phase velocities in the range of ±45 m/s, which might result in most of the parameterized sub-grid GWs dissipating and breaking in the mesosphere and hardly impacting the lower thermosphere. Only including slow GWs in the SD-WACCMX parameterization could potentially lead to the underestimation of the meridional wind in the model. Analysis also indicates the lower-thermospheric meridional circulation is stronger in the summer hemisphere, which is attributed to the hemispheric asymmetry in the resolved wave momentum forcing. This study underlines the importance of the whole atmosphere coupling through wave propagation and dissipation. This understanding can guide the model development with an accurate representation of underlying physical processes in the mesosphere and lower thermosphere which drives the lower-thermospheric circulation as well as the overall dynamics of this region.

Jack C. Wang↗
NASA NTRS1986

Evaluation of residual strength of composite laminates damaged by low velocity impacts

This work presents the study of Low Velocity Transverse Impact damage of graphite-epoxy T300/5208 composite material. An energy dissipation model was developed to predict the residual strength from fracture mechanics concepts. The specimens, 100 mm diameter clamped plates, were impact damaged by a cantilever-type instrumented 1-inch diameter steel ball. This study was limited to impact velocity 6 m/sec. Rectangular strips, 50 mm x 125 mm, were cut from the impact-damaged specimens so that the impact damage zone was in the center of the strips. These strips were tested to obtain their residual strength. Predictions were compared with the test results.

Lal, K. M.↗
NASA NTRS2010

Use of LS-DYNA(Registered TradeMark) to Assess the Energy Absorption Performance of a Shell-Based Kevlar(TradeMark)/Epoxy Composite Honeycomb

The forward and vertical impact stability of a composite honeycomb Deployable Energy Absorber (DEA) was evaluated during a full-scale crash test of an MD-500 helicopter at NASA Langley?s Landing and Impact Research Facility. The lower skin of the helicopter was retrofitted with DEA components to protect the airframe subfloor upon impact and to mitigate loads transmitted to Anthropomorphic Test Device (ATD) occupants. To facilitate the design of the DEA for this test, an analytical study was conducted using LS-DYNA(Registered TradeMark) to evaluate the performance of a shell-based DEA incorporating different angular cell orientations as well as simultaneous vertical and forward impact conditions. By conducting this study, guidance was provided in obtaining an optimum design for the DEA that would dissipate the kinetic energy of the airframe while maintaining forward and vertical impact stability.

Polanco, Michael↗
NASA NTRS1981

Vacuum UV and soft X-ray optical emissions from electron impact on metals

Spectrograms from 2200 to 20 A of optical emissions produced by a simple lamp using fast (3-10-keV) electron impact on tungsten and tantalum targets are presented. The lamp dissipated up to 5 kW/sq cm on the target surface, simultaneously cleaning the surface and generating bremsstrahlung in the soft X-ray region with 3-keV electron impact and longer wavelength transition radiation at the higher energy. In both the bremsstrahlung and transition radiation modes, the lamp emissions were of sufficient strength and reproducibility to qualify the two mechanisms as potential processes for use in a secondary standard light source. Calculated spectral distributions of transition radiation for normally incident electrons on tungsten, tantalum, and aluminum targets, with a viewing direction 45 deg from the normal, are also shown.

Hughes, R. H.↗
NASA NTRS1988

Energetics of chondrule formation

Meteorite chondrules apparently were formed as a result of localized, transient heating events in the protoplanetary nebula. Such transient events, which seem to have heated the chondrules to temperatures in excess of 1500 C for not more than a few minutes, are not easily explicable in terms of the canonically accepted evolutionary processes of the nebular disk. Thus the occurrence of extraordinary dynamical processes may be indicated by the presence of chondrules and, consequently, the existence of chondrules poses questions fundamental to the understanding of protoplanetary and protostellar systems. This chapter briefly considers the gross energetics, as well as some related questions, of chondrule formation and the implications for several previously proposed sources of chondrule formation energy, including gravitational infall of the nebula, energy derived from solid-body impacts within the nebula, and energy liberated by dissipative evolution of the nebula itself.

Levy, E. H.↗
NASA NTRS1993

Effect of parking orbit period on aerocapture for manned Mars missions

Aerocapture has previously been identified as a critical technology for manned Mars missions. A wide range of parking orbits is available into which an aerobraking vehicle could be captured, and earlier authors have advocated different target orbits for various reasons. The choice of the parking orbit impacts the amount of energy which must be dissipated during the atmospheric trajectory. The effect of this choice on the entry corridor width, the required vehicle L/D, and the aerothermal environment are explored in this paper.

Lyne, James E.↗
NASA NTRS1989

Numerical study of a delta planform with multiple jets in ground effect

The flow past a 60-deg delta wing equipped with two thrust-reverser jets near the inboard trailing edge has been analyzed by numerical solution of the 3D thin-layer Navier-Stokes equations. An implicit, partially flux-split, approximately-factored Navier-Stokes solver coupled with a multiple grid embedding scheme has been adapted to this problem. Studies of the impact of numerical parameters (e.g., grid refinement and dissipation levels), and flow-field parameters such as the height of the delta wing above the ground plane and the jet size on the solution, were performed. Results of these numerical studies indicate some challenges in the accurate resolution of complex 3D free shear layers and jets. Nevertheless, flow features such as jet deformation and ground vortex formation observed in experimental flow visualizations are captured. Further, comparisons with experimental data confirm the ability to simulate the loss of wing-borne lift, commonly referred to 'suckdown, as the delta planform flies at slow speeds in close proximity to the ground. Detailed analysis of the numerical results has also given additional insight into the structure of the ground vortex and the mechanisms of lift loss.

Chawla, K.↗
NASA NTRS2000

Microgravity Disturbance Characterization of the Quench Module Insert (QMI) Phase Change Device (PCD)

The Materials Science Research Facility (MSRF) is a multi-user, multi-purpose facility for materials science research. One experiment within the MSRF will be the Quench Module Insert (QMI), a high-temperature furnace with unique capabilities for processing different classes of materials. The primary functions of the QMI furnace are to melt, directionally solidify, and quench metallic samples, providing data to aid in understanding the effects of the microgravity environment on the characteristics of these processed metals. The QMI houses sealed individual sample ampoules containing material to be processed. Quenching of the samples in the QMI furnace is accomplished by releasing low-melting-point metallic shoes into contact with the outside of the sample ampoule, dissipating heat and cooling the sample inside. The impact from this method of quench will induce sample vibrations which could be large enough to adversely affect sample quality. Utilizing breadboard hardware, the sample quench sequence, releasing the shoes, was conducted. Data was collected from accelerometers located on the breadboard sample cartridge, indicating the maximum acceleration achieved by the sample. The primary objective of the test described in this presentation was to determine the acceleration imparted on the sample by the shoe contact. From this information, the science community can better assess whether this method of quench will allow them to obtain the data they need.

Gattis, Christy↗
NASA NTRS2009

Origin and Evolution of Organic Matter Preserved in Stardust Cometary Aerogel Tracks

The STARDUST spacecraft captured dust samples from Comet 81P/Wild 2 at a relative velocity of 6.1 km/s in a low density silica aerogel and returned them to the Earth. One of the main of the scientific goals established for the mission was to determine whether comets contained complex organic materials and, contingently, the nature and abundance of this material. [1] Although contamination concerns due to carbonaceous impurities intrinsic to the flight aerogel remain, it is generally accepted that at least a fraction of the captured dust particles contain an indigenous organic component. [2] However, understanding the nature and abundance of this material is complicated by nature of the collection process. The rapid dissipation of particle s kinetic energy during its impact and deceleration cause both the particle and surrounding aerogel to experience an intense thermal pulse of upwards of 2000K for a period up to several hundred nanoseconds [3]. During this period thermal alteration and or destruction of organic species present in the impacting particle are likely to occur. We have used the technique of ultrafast two-step laser mass spectrometry (ultra L2MS) [4] to investigate how the nature and distribution of aromatic and conjugated organic species varies between and within aerogel cometary tracks and their associated terminal particles.

McKay, D.S.↗
NASA NTRS2012

Optimal Force Control of Vibro-Impact Systems for Autonomous Drilling Applications

The need to maintain optimal energy efficiency is critical during the drilling operations performed on future and current planetary rover missions (see figure). Specifically, this innovation seeks to solve the following problem. Given a spring-loaded percussive drill driven by a voice-coil motor, one needs to determine the optimal input voltage waveform (periodic function) and the optimal hammering period that minimizes the dissipated energy, while ensuring that the hammer-to-rock impacts are made with sufficient (user-defined) impact velocity (or impact energy). To solve this problem, it was first observed that when voice-coil-actuated percussive drills are driven at high power, it is of paramount importance to ensure that the electrical current of the device remains in phase with the velocity of the hammer. Otherwise, negative work is performed and the drill experiences a loss of performance (i.e., reduced impact energy) and an increase in Joule heating (i.e., reduction in energy efficiency). This observation has motivated many drilling products to incorporate the standard bang-bang control approach for driving their percussive drills. However, the bang-bang control approach is significantly less efficient than the optimal energy-efficient control approach solved herein. To obtain this solution, the standard tools of classical optimal control theory were applied. It is worth noting that these tools inherently require the solution of a two-point boundary value problem (TPBVP), i.e., a system of differential equations where half the equations have unknown boundary conditions. Typically, the TPBVP is impossible to solve analytically for high-dimensional dynamic systems. However, for the case of the spring-loaded vibro-impactor, this approach yields the exact optimal control solution as the sum of four analytic functions whose coefficients are determined using a simple, easy-to-implement algorithm. Once the optimal control waveform is determined, it can be used optimally in the context of both open-loop and closed-loop control modes (using standard realtime control hardware).

Aldrich, Jack B.↗
NASA NTRS2009

Numerical Analysis of Film Cooling at High Blowing Ratio

Computational Fluid Dynamics is used in the analysis of a film cooling jet in crossflow. Predictions of film effectiveness are compared with experimental results for a circular jet at blowing ratios ranging from 0.5 to 2.0. Film effectiveness is a surface quantity which alone is insufficient in understanding the source and finding a remedy for shortcomings of the numerical model. Therefore, in addition, comparisons are made to flow field measurements of temperature along the jet centerline. These comparisons show that the CFD model is accurately predicting the extent and trajectory of the film cooling jet; however, there is a lack of agreement in the near-wall region downstream of the film hole. The effects of main stream turbulence conditions, boundary layer thickness, turbulence modeling, and numerical artificial dissipation are evaluated and found to have an insufficient impact in the wake region of separated films (i.e. cannot account for the discrepancy between measured and predicted centerline fluid temperatures). Analyses of low and moderate blowing ratio cases are carried out and results are in good agreement with data.

El-Gabry, Lamyaa↗
NASA NTRS1939

Resistance of Transparent Plastics to Impact

The problem of developing a windshield for aircraft which will withstand the effect of bird impacts during flight is a difficult one, as an estimate of the striking energy will indicate. If the average speed of the airplane is considered to be about 200 miles per hour and that of the bird about 70 miles per hour, the speed of the bird relative to the airplane may be as great as 400 feet per second. If a 4-pound bird is involved, a maximum impact energy of approximately 10,000 foot-pounds must be dissipated. To obtain this energy in a drop test in the Washington Monument, it would be necessary to drop a 20-pound weight down the 500-foot shaft. For both theoretical and practical reasons, it is necessary to keep the mass and speed more nearly like those to be encountered. However, to get an impact of about 10,000 foot-pounds with a 4-pound falling body, it would be necessary to drop it from a height of approximately one-half mile, neglecting air resistance. These facts will indicate some of the experimental obstacles in the way of simulating bird impacts against aircraft windshields.

Axilrod, Benjamin M↗
NASA NTRS2000

Problem Definition and Solution Concept for En Route Constrained Airspace Problems

NASA's AATT Program is investigating potential ground-based decision support tool (DST) development for en route controllers and managers. NASA's previous work in en route DST development has focused on Transition airspace, where aircraft are impacted by constraints associated with the transition of aircraft from en route to terminal airspace. This paper investigates the problems associated with aircraft in non-transitional en route airspace, termed Constrained Airspace. A literature search was performed to catalog previously identified constrained airspace problems. The results of this search were investigated with industry representatives to validate these problems were significant in constrained airspace. Three general problem areas were identified. The first problem area involves negative impacts caused by a loss of airspace (e.g., activation of Special Use Airspace (SUA), weather cell formation, and overloaded sectors). The second problem area is the lack of identifying and taking advantage of gained airspace (e.g., SUA deactivation, weather dissipation, and sector loading reductions). The third problem area is unforeseen negative impacts caused by the acceptance of user routing requests (e.g., a route change into an area of congestion that negated the users intended benefit). Based upon the problems identified, an operational concept was developed for a DST to help handle these problems efficiently. The goal is to strategically identify constrained airspace problems and to provide functionality to support ARTCC TMUs in resolving the identified impacts. The capability lends itself well to TMU and Airline Operations Center (AOC) collaboration.

Green, Steven↗
NASA NTRS1991

Energy dissipation in structured electrodynamic environments

It is usually assumed that the profile of the ion Pedersen conductivity determines the altitude dependence of the energy dissipation rate This paper points out the strong altitude dependence of the energy dissipation rate on the spatial scale size of the imposed electric field. To illustrate the importance of such considerations, examples of the ubiquity to electric field structure in the high-latitude ionosphere are shown; this is particularly prominent when the interplanetary magnetic field has a northward component. It is then shown quantitatively how the existence of electric field structure with scale sizes of 10 km or less strongly impacts both the altitude extent over which the electromagnetic energy is dissipated and its partitioning between current systems perpendicular and parallel to the magnetic field.

Heelis, R. A.↗