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NASA NTRS2011

Analysis of Compression Algorithm in Ground Collision Avoidance Systems (Auto-GCAS)

Automatic Ground Collision Avoidance Systems (Auto-GCAS) utilizes Digital Terrain Elevation Data (DTED) stored onboard a plane to determine potential recovery maneuvers. Because of the current limitations of computer hardware on military airplanes such as the F-22 and F-35, the DTED must be compressed through a lossy technique called binary-tree tip-tilt. The purpose of this study is to determine the accuracy of the compressed data with respect to the original DTED. This study is mainly interested in the magnitude of the error between the two as well as the overall distribution of the errors throughout the DTED. By understanding how the errors of the compression technique are affected by various factors (topography, density of sampling points, sub-sampling techniques, etc.), modifications can be made to the compression technique resulting in better accuracy. This, in turn, would minimize unnecessary activation of A-GCAS during flight as well as maximizing its contribution to fighter safety.

Schmalz, Tyler↗

NASA NTRS2011

Image Segmentation, Registration, Compression, and Matching

A novel computational framework was developed of a 2D affine invariant matching exploiting a parameter space. Named as affine invariant parameter space (AIPS), the technique can be applied to many image-processing and computer-vision problems, including image registration, template matching, and object tracking from image sequence. The AIPS is formed by the parameters in an affine combination of a set of feature points in the image plane. In cases where the entire image can be assumed to have undergone a single affine transformation, the new AIPS match metric and matching framework becomes very effective (compared with the state-of-the-art methods at the time of this reporting). No knowledge about scaling or any other transformation parameters need to be known a priori to apply the AIPS framework. An automated suite of software tools has been created to provide accurate image segmentation (for data cleaning) and high-quality 2D image and 3D surface registration (for fusing multi-resolution terrain, image, and map data). These tools are capable of supporting existing GIS toolkits already in the marketplace, and will also be usable in a stand-alone fashion. The toolkit applies novel algorithmic approaches for image segmentation, feature extraction, and registration of 2D imagery and 3D surface data, which supports first-pass, batched, fully automatic feature extraction (for segmentation), and registration. A hierarchical and adaptive approach is taken for achieving automatic feature extraction, segmentation, and registration. Surface registration is the process of aligning two (or more) data sets to a common coordinate system, during which the transformation between their different coordinate systems is determined. Also developed here are a novel, volumetric surface modeling and compression technique that provide both quality-guaranteed mesh surface approximations and compaction of the model sizes by efficiently coding the geometry and connectivity/topology components of the generated models. The highly efficient triangular mesh compression compacts the connectivity information at the rate of 1.5-4 bits per vertex (on average for triangle meshes), while reducing the 3D geometry by 40-50 percent. Finally, taking into consideration the characteristics of 3D terrain data, and using the innovative, regularized binary decomposition mesh modeling, a multistage, pattern-drive modeling, and compression technique has been developed to provide an effective framework for compressing digital elevation model (DEM) surfaces, high-resolution aerial imagery, and other types of NASA data.

Yadegar, Jacob↗

NASA NTRS2012

Quasi 1D Modeling of Mixed Compression Supersonic Inlets

The AeroServoElasticity task under the NASA Supersonics Project is developing dynamic models of the propulsion system and the vehicle in order to conduct research for integrated vehicle dynamic performance. As part of this effort, a nonlinear quasi 1-dimensional model of the 2-dimensional bifurcated mixed compression supersonic inlet is being developed. The model utilizes computational fluid dynamics for both the supersonic and subsonic diffusers. The oblique shocks are modeled utilizing compressible flow equations. This model also implements variable geometry required to control the normal shock position. The model is flexible and can also be utilized to simulate other mixed compression supersonic inlet designs. The model was validated both in time and in the frequency domain against the legacy LArge Perturbation INlet code, which has been previously verified using test data. This legacy code written in FORTRAN is quite extensive and complex in terms of the amount of software and number of subroutines. Further, the legacy code is not suitable for closed loop feedback controls design, and the simulation environment is not amenable to systems integration. Therefore, a solution is to develop an innovative, more simplified, mixed compression inlet model with the same steady state and dynamic performance as the legacy code that also can be used for controls design. The new nonlinear dynamic model is implemented in MATLAB Simulink. This environment allows easier development of linear models for controls design for shock positioning. The new model is also well suited for integration with a propulsion system model to study inlet/propulsion system performance, and integration with an aero-servo-elastic system model to study integrated vehicle ride quality, vehicle stability, and efficiency.

Kopasakis, George↗

NASA NTRS2012

Quasi One-Dimensional Unsteady Modeling of External Compression Supersonic Inlets

Kopasakis, George↗

NASA NTRS2009

Sequential Principal Component Analysis -An Optimal and Hardware-Implementable Transform for Image Compression

This paper presents the JPL-developed Sequential Principal Component Analysis (SPCA) algorithm for feature extraction / image compression, based on "dominant-term selection" unsupervised learning technique that requires an order-of-magnitude lesser computation and has simpler architecture compared to the state of the art gradient-descent techniques. This algorithm is inherently amenable to a compact, low power and high speed VLSI hardware embodiment. The paper compares the lossless image compression performance of the JPL's SPCA algorithm with the state of the art JPEG2000, widely used due to its simplified hardware implementability. JPEG2000 is not an optimal data compression technique because of its fixed transform characteristics, regardless of its data structure. On the other hand, conventional Principal Component Analysis based transform (PCA-transform) is a data-dependent-structure transform. However, it is not easy to implement the PCA in compact VLSI hardware, due to its highly computational and architectural complexity. In contrast, the JPL's "dominant-term selection" SPCA algorithm allows, for the first time, a compact, low-power hardware implementation of the powerful PCA algorithm. This paper presents a direct comparison of the JPL's SPCA versus JPEG2000, incorporating the Huffman and arithmetic coding for completeness of the data compression operation. The simulation results show that JPL's SPCA algorithm is superior as an optimal data-dependent-transform over the state of the art JPEG2000. When implemented in hardware, this technique is projected to be ideally suited to future NASA missions for autonomous on-board image data processing to improve the bandwidth of communication.

Duong, Tuan A.↗

NASA NTRS2008

Onboard Data Compression of Synthetic Aperture Radar Data: Status and Prospects

Synthetic aperture radar (SAR) instruments on spacecraft are capable of producing huge quantities of data. Onboard lossy data compression is commonly used to reduce the burden on the communication link. In this paper an overview is given of various SAR data compression techniques, along with an assessment of how much improvement is possible (and practical) and how to approach the problem of obtaining it. Synthetic aperture radar (SAR) instruments on spacecraft are capable of acquiring huge quantities of data. As a result, the available downlink rate and onboard storage capacity can be limiting factors in mission design for spacecraft with SAR instruments. This is true both for Earth-orbiting missions and missions to more distant targets such as Venus, Titan, and Europa. (Of course for missions beyond Earth orbit downlink rates are much lower and thus potentially much more limiting.) Typically spacecraft with SAR instruments use some form of data compression in order to reduce the storage size and/or downlink rate necessary to accommodate the SAR data. Our aim here is to give an overview of SAR data compression strategies that have been considered, and to assess the prospects for additional improvements.

Klimesh, Matthew A.↗

NASA NTRS2014

Fractal Loop Heat Pipe Performance Comparisons of a Soda Lime Glass and Compressed Carbon Foam Wick

This study compares heat flux performance of a Loop Heat Pipe (LHP) wick structure fabricated from compressed carbon foam with that of a wick structure fabricated from sintered soda lime glass. Each wick was used in an LHP containing a fractal based evaporator. The Fractal Loop Heat Pipe (FLHP) was designed and manufactured by Mikros Manufacturing Inc. The compressed carbon foam wick structure was manufactured by ERG Aerospace Inc., and machined to specifications comparable to that of the initial soda lime glass wick structure. Machining of the compressed foam as well as performance testing was conducted at the United States Naval Academy. Performance testing with the sintered soda lime glass wick structures was conducted at NASA Goddard Space Flight Center. Heat input for both wick structures was supplied via cartridge heaters mounted in a copper block. The copper heater block was placed in contact with the FLHP evaporator which had a circular cross-sectional area of 0.88 cm(sup 2). Twice distilled, deionized water was used as the working fluid in both sets of experiments. Thermal performance data was obtained for three different Condenser/Subcooler temperatures under degassed conditions. Both wicks demonstrated comparable heat flux performance with a maximum of 75 W/cm observed for the soda lime glass wick and 70 W /cm(sup 2) for the compressed carbon foam wick.

Myre, David↗

NASA NTRS2015

COxSwAIN: Compressive Sensing for Advanced Imaging and Navigation

The COxSwAIN project focuses on building an image and video compression scheme that can be implemented in a small or low-power satellite. To do this, we used Compressive Sensing, where the compression is performed by matrix multiplications on the satellite and reconstructed on the ground. Our paper explains our methodology and demonstrates the results of the scheme, being able to achieve high quality image compression that is robust to noise and corruption.

Kurwitz, Richard↗

NASA NTRS2015

A Priori Analysis of a Compressible Flamelet Model using RANS Data for a Dual-Mode Scramjet Combustor

In an effort to make large eddy simulation of hydrocarbon-fueled scramjet combustors more computationally accessible using realistic chemical reaction mechanisms, a compressible flamelet/progress variable (FPV) model was proposed that extends current FPV model formulations to high-speed, compressible flows. Development of this model relied on observations garnered from an a priori analysis of the Reynolds-Averaged Navier-Stokes (RANS) data obtained for the Hypersonic International Flight Research and Experimentation (HI-FiRE) dual-mode scramjet combustor. The RANS data were obtained using a reduced chemical mechanism for the combustion of a JP-7 surrogate and were validated using avail- able experimental data. These RANS data were then post-processed to obtain, in an a priori fashion, the scalar fields corresponding to an FPV-based modeling approach. In the current work, in addition to the proposed compressible flamelet model, a standard incompressible FPV model was also considered. Several candidate progress variables were investigated for their ability to recover static temperature and major and minor product species. The effects of pressure and temperature on the tabulated progress variable source term were characterized, and model coupling terms embedded in the Reynolds- averaged Navier-Stokes equations were studied. Finally, results for the novel compressible flamelet/progress variable model were presented to demonstrate the improvement attained by modeling the effects of pressure and flamelet boundary conditions on the combustion.

Quinlan, Jesse R.↗

NASA NTRS2018

The New CCSDS Standard for Low-Complexity Lossless and Near-Lossless Multispectral and Hyperspectral Image Compression

This paper describes the emerging Issue 2 of the CCSDS-123.0-B standard for low-complexity compression of multispectral and hyperspectral imagery, focusing on its new features and capabilities. Most significantly, this new issue incorporates a closed-loop quantization scheme to provide near-lossless compression capability while still supporting lossless compression, and introduces a new entropy coding option that provides better compression of low-entropy data.

Kiely, Aaron B.↗

NASA NTRS2016

Progress on the CO2 Removal and Compression System

The Carbon Dioxide Removal and Compression System (CRCS) is designed to perform both the Carbon Dioxide(CO2) removal and compress CO2 for further processing. The CRCS was designed as a lower power requirement option to the one currently being used on the International Space Station (ISS). This paper describes the final design, fabrication, assembly, and testing of the integrated CRCS. Initial results indicated that the spiral heaters used did not yield uniform heating within both the adsorption and compression beds. In addition, the heaters for the compression bed were insufficient and an additional HVAC jacket was employed to provide heat to the bed.

Air Revitalization↗

NASA NTRS2022

On the Existence of Fast Modes in Compressible Magnetohydrodynamic Turbulence

We study the existence and properties of fast magnetosonic modes in 3D compressible MHD turbulence by carrying out a number of simulations with compressible and incompressible driving conditions. We use two approaches to determine the presence of fast modes: mode decomposition based on spatial variations only and spatio-temporal 4D fast Fourier transform (4D FFT) analysis of all fluctuations. The latter method enables us to quantify fluctuations that satisfy the dispersion relation of fast modes with finite frequency. Overall, we find that the fraction of fast modes identified via the spatio-temporal 4D FFT approach in total fluctuation power is either tiny with nearly incompressible driving or ∼2% with highly compressible driving. We discuss the implications of our results for understanding the compressible fluctuations in space and astrophysical plasmas.

Zhaoming Gan↗

NASA NTRS2023

Compressible Turbulence in the Near-Sun Solar Wind Parker Solar Probe's First Eight Perihelia

Many questions remain about the compressibility of solar wind turbulence with respect to its origins and properties. Low plasma beta (ratio of thermal to magnetic pressure) environments allow for the easier generation of compressible turbulence, enabling study of the relationship between density fluctuations and turbulent Mach number. Utilizing Parker Solar Probe plasma data, we examine the normalized proton density fluctuations as a function of turbulent Mach number M t conditioned on plasma beta and cross helicity. With consideration of statistical error in the parameters computed from in situ data, we find a general result consistent with both linear-wave theory and nearly incompressible turbulence in an inhomogeneous background field. We compare observational results conditioned on plasma beta and cross helicity with 3D magnetohydrodynamic simulations and observe rather significant similarities with respect to how those parameters affect the proportionality between density fluctuations and turbulent Mach number. This study further investigates the complexity of compressible turbulence as viewed by the density scaling relationship and may help better understand the compressible environment of the near-Sun solar wind.

Manuel Enrique Cuesta↗

DOE OSTI2016

Memory hierarchy using row-based compression

A system includes a first memory and a device coupleable to the first memory. The device includes a second memory to cache data from the first memory. The second memory includes a plurality of rows, each row including a corresponding set of compressed data blocks of non-uniform sizes and a corresponding set of tag blocks. Each tag block represents a corresponding compressed data block of the row. The device further includes decompression logic to decompress data blocks accessed from the second memory. The device further includes compression logic to compress data blocks to be stored in the second memory.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2018

SLED-II: A New Method of RF Pulse Compression

In the SLED 1 method of RF pulse compression, two high Q resonators store energy from an RF source for a relatively long time interval (typically 3 to 5 J.1sec). Triggered by a reversal in RF phase, this stored energy is then released during a much shorter interval equal to the filling time of the accelerating structure. A peak power gain on the order of three and a compression efficiency on the order of 60% are typically attained. The shape of the output pulse is, however, a sharply decaying expo- nential. In SLED-II the two cavities are replaced by two lengths of resonant line, forming a Resonant Line SLED (RELS) and resulting in a flat output pulse. Therefore, RELS stages can be cascaded to give a greater peak power gain. Using two stages, a peak power gain greater than ten can be achieved with a reasonable compression efficiency. Unlike the BEC,2 the RELS compression fac- tor per stage is not limited to two, albeit at the expense of intrinsic efficiency. Like the BEC, it uses long lines rather than short cavities.

Farkas, Z.↗

DOE OSTI2019

Ignition, Flame Progation, and End-Gas Autoignition Studies of Natural Gas/ EGR Blends in a Rapid Compression Machine

The development of high efficiency, spark ignited natural gas engines is currently limited by engine knock at high power density (at high compression ratio and/or elevated boost pressures) and misfire (at lean conditions and/or high exhaust gas recirculation levels). The knock and misfire limits are further confounded by the wide variety in fuel reactivity observed in “pipeline quality” natural gas. In this study, a rapid compression machine (RCM) was used to characterize the effects of variation in natural gas fuel reactivity and exhaust gas recirculation (EGR) on homogeneous ignition delay, flame propagation rate and end-gas autoignition (EGAI) propensity for stoichiometric natural gas/oxidizer/EGR blends. Pipeline quality natural gas with variable reactivity (68 < Methane Number < 95) was simulated using mixtures of methane, ethane, and propane. EGR was simulated with mixtures of Ar, CO2, CO, and NO. EGR substitution rates were varied from 0 to 30 mass percent. Ignition delay period under homogeneous autoignition conditions was measured at compressed pressures of 24.0 to 33.1 bar and compressed temperatures of 667 to 980 K. Flame propagation rate and EGAI propensity was measured at spark-ignition pressures of 29.9 to 32.9 bar and temperatures of 721 to 782 K.

Mohr, Jeffrey↗

DOE OSTI2019

Flow Characterization of Compressed Woody Biomass

Global interest for using terrestrial biomass as an energy source has been increasing recently due to potentially significant socio-economic and environmental benefits relative to fossil energy. Thermochemical biomass processes converting biomass to fuels are relatively well developed, e.g. for direct combustion, gasification, and pyrolysis. However, critical problems often arise when attempting to feed biomass into commercial-scale reactors continuously and without interruption. Biomass particles, whether derived from woody or agricultural feedstock, vary greatly in size, shape, density, and moisture content. High cohesiveness, low bulk density, and poor material flow characteristics often prevent continuous feeding due to bridging, rat-hole formation, blockage, and seal failures. Among all different types of feeders utilized to feed biomass into reactors, screw feeding has received significant attention in recent years. Screw feeders are fuel-specific and require careful design to be reliable, efficient, and economical, especially for reactors operating at elevated pressures. In order to mimic the flow properties of compressed biomass inside a compression-screw feeder, rheological properties of three types of compressed lignocellulosic biomass were investigated using a co-rotating twin screw microcompounder. Experiments were conducted to find the impact of moisture content, particle size and type, and screw speed on rheological properties of forest residual particles as well as sawdust. Increasing moisture from 10 to 50% reduced the apparent viscosity of the compressed biomass. Also, higher screw speeds (10 to 90 rpm) led to a lower relative viscosity. At elevated screw speeds, significant temperature differences were measured between the initial and final states, which should be accounted for in equipment design and operation.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2017

Predicting uniaxial compressive strength from empirical relationships between ultrasonic p-wave velocities, porosity, and core measurements in a potential geothermal reservoir, Snake River Plain, Idaho

Empirical, core-based, predictive correlations for the calculation of uniaxial compressive strength (UCS) were developed from compressive sonic velocity measurements (55 whole core samples) and porosity, density, and unconfined compressive tests (110 whole core samples). The samples were collected at 55 different depths in a 550 m (1800 ft) interval of core from the MH-2 borehole located in southern Idaho, USA. The western Snake River Plain is a known region of high heat flow and the borehole was drilled into a potential geothermal reservoir characterized by artesian flow of high-temperature (~140°C) fluids from fractured basalt. UCS was measured in unconfined compressive tests, density and porosity were measured using a He-pycnometer, and p-wave velocities were measured in a pressure vessel under variable confining pressures. We use correlations between density and p-wave velocity (R 2 = 0.91), UCS and porosity (R 2 = 0.78), and UCS and p-wave velocity (R 2 = 0.79) in a method to calculate calibrated UCS from wireline logs. Here, the impact of this predictive correlation is that UCS can be calculated from as little as a bulk density log when sonic logs and core are not available, greatly increasing the number of wells in which we can obtain a local UCS estimate.

15 GEOTHERMAL ENERGY↗