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NASA NTRS2018

Optically Inaccessible Flow Visualization using Positron Emission Tomography

Flow visualization is a powerful tool for characterizing fluid dynamics within engineering systems that utilize fluid working media. Recent advances in Positron Emission Tomography (PET) have enhanced its ability to extend beyond the medical field, and offer an alternate vantage point in visualizing optically inaccessible fluid distributions and flow fields within the aerospace field. In light of this prospect an investigation has ensued to parametrically bound the flows that can be sufficiently resolved using current PET technology. Results from an initial series of experiments and analyses performed at the Positron Imaging Centre (PIC) located at the University of Birmingham, UK, will be presented. Discussion will also cover preliminary, on-going, activities associated with assessing the utility of PET technology in zero-gravity propellant gauging, ionization efficiency characterization in electric propulsion devices, and broader industrial applications.

PET↗

NASA NTRS2021

Application of Radon Transform to Multi-Angle Measurements Made by the Research Scanning Polarimeter: A New Approach to Cloud Tomography. Part I: Theory and Tests on Simulated Data.

The Research Scanning Polarimeter (RSP) is an airborne along-track scanner measuring the polarized and total reflectances in 9 spectral channels. The RSP was a prototype for the Aerosol Polarimetry Sensor (APS) launched on-board the NASA Glory satellite. Currently the retrieval algorithms developed for the RSP are being adopted for the measurements of the space-borne polarimeters on the upcoming NASA’s Plankton, Aerosol, Cloud Ocean Ecosystem (PACE)satellite mission. The RSP’s uniquely high angular resolution coupled with the high frequency of measurements allows for characterization of liquid water cloud droplet sizes using the polarized rainbow structure. It also provides geometric constraints on the cumulus cloud’s 2D cross section yielding the cloud’s geometric shape estimates. In this study we further build on the latter technique to develop a new tomographic approach to retrieval of cloud internal structure from remote sensing measurements. While tomography in the strict definition is a technique based on active measurements yielding a tomogram (directional optical thickness as a function of angle and offset of the view ray), we developed a “semi-tomographic” approach in which tomogram of the cloud is estimated from passive observations instead of being measured directly. This tomogram is then converted into 2D spatial distribution of the extinction coefficient using inverse Radon transform (filtered back projection) which is the standard tomographic procedure used e.g., in medical CT scans. This algorithm is computationally inexpensive compared to techniques relying on highly-multi-dimensional least-square fitting; it does not require iterative 3D RT simulations. The resulting extinction distribution is defined up to an unknown constant factor, so we discuss the ways to calibrate it using additional independent measurements. In the next step we use the profile of the droplet size distribution parameters from the cloud’s side (derived by fitting the polarized rainbows) to convert the 2D extinction distribution into that of the droplet number concentration. We illustrate and validate the proposed technique using 3D-RT-simulatedRSP observations of a LES-generated Cu cloud. Quantitative comparisons between the retrieved and the original optical and microphysical parameters are presented.

clouds↗

NASA NTRSDate not supplied

Preliminary Results from Propellant Mass Gauging with Electrical Capacitance Tomography

Propellants mass gauging technologies designed to work in an accelerated environment, where the propellant remains settled at one end of the propellant tank, do not work well in a microgravity environment because the propellant is not necessarily settled. While some microgravity mass gauging technologies exist at various TRLs, most of them have major disadvantages. Improvements in microgravity propellant mass gauging will result in improvements to many areas of propellant management, which influences performance and mission assurance. Electrical Capacitance Tomography (ECT) is a sensing technology that is able to reconstruct the liquid distribution inside of a tank, which can then be integrated to obtain mass. ECT mass gauging recently achieved high accuracy in laboratory testing, <0.1% liquid volume measurement error, even during sloshing. While ECT mass gauging will theoretically work during all phases of flight, it had not yet been tested in microgravity. The NASA KSC Launch Services Program, with support from the Flight Opportunities Program, successfully flew an ECT liquid mass gauging system experiment on a Zero-G parabolic flight aircraft. Basics of ECT measurement theory, details of the experiment setup and flights, and preliminary results will be discussed. The preliminary results suggest that, even in the current prototype generation, ECT sensor systems will be useful as a propellant mass gauging technology in both an accelerated and microgravity environment.

mass gauging↗

NASA NTRSDate not supplied

Preliminary Results From Propellant Mass Gauging in Microgravity with Electrical Capacitance Tomography

This presentation is a shortened and simplified version of the original from Jed Storey intended for usage with an a.i. Solutions' "Lunch-and-learn" audience. It reviews the setup, execution, and some preliminary results from the Electrical Capacitive Tomography experiment conducted by NASA KSC Launch Services Program flown aboard a Zero-G aircraft earlier this year. The original is STRIVES submission 20220010165. Some extra images and videos have been added and some detailed content removed since the purpose of this presentation is less technical than that of it's parent.

mass gauging↗

NASA NTRS2022

Microgravity Electrical Capacitance Tomography Data Set

Propellants mass gauging technologies designed to work in an accelerated environment, where the propellant remains settled at one end of the propellant tank, do not work well in a microgravity environment because the propellant is not necessarily settled. While some microgravity mass gauging technologies exist at various TRLs, most of them have major disadvantages. Improvements in microgravity propellant mass gauging will result in improvements to many areas of propellant management, which influences performance and mission assurance. Electrical Capacitance Tomography (ECT) is a sensing technology that has been used in the oil/gas industry for decades to measure multi-phase flow rate in pipes. ECT, when installed in a tank, is able to reconstruct the liquid distribution inside of the tank, which can then be integrated to obtain mass. ECT mass gauging recently achieved high accuracy in laboratory testing on the ground, and while ECT mass gauging will theoretically work during all phases of flight, it had not yet been tested in microgravity. The NASA KSC Launch Services Program, with support from the Flight Opportunities Program, successfully flew an ECT tank liquid mass gauging system experiment on a Zero-G parabolic flight aircraft. The experiment hardware was rented from a company; NASA LSP did no technology development work for this project. This STRIVES entry is for the entire raw data set, which consists of approximately 25GB of csv files of capacitance and motion data from the ground and flight tests of the experiment. The data set will be available on the NASA LSP Electronic Slosh Data Catalog (ESDC), and the public may request the data set from the authors (POC: Jed Storey, jedediah.m.nasa.gov).

mass gauging↗

NASA NTRS2023

Propellant Mass Gauging in Microgravity with Electrical Capacitance Tomography

Advancements in microgravity propellant mass gauging will result in improvements to many areas of propellant management, which influences space vehicle performance and mission assurance. Propellant mass gauging technologies designed to work in an accelerated environment, where the propellant remains settled at one end of the propellant tank, do not always work well in a microgravity environment because the propellant is not necessarily settled. While some microgravity mass gauging technologies exist at various stages of development, most of them have major disadvantages. Electrical Capacitance Tomography (ECT) is a sensing technology that is able to reconstruct the liquid distribution inside of a tank, which can then be integrated to obtain mass. While ECT mass gauging will theoretically work during all phases of flight, it had not yet been tested in microgravity. The NASA Kennedy Space Center Launch Services Program, with support from the Flight Opportunities Program, successfully tested an ECT liquid mass gauging system experiment on a parabolic flight aircraft in May 2022. Basics of ECT measurement theory, details of the experiment setup, data processing, ground test results, and the flight test result will be discussed. The results suggest that ECT sensor systems will be useful as a propellant mass gauging technology in both accelerated and microgravity environments.

electrical capacitance tomography↗

NASA NTRS1974

Fluoroscopic tomography

A fluoroscopic tomography system capable of synthesizing body sections at a number of levels within the body has been developed. The synthesized body sections may lie either in a range of planes parallel to, tilted with respect to, skewed with respect to, or both tilted and skewed with respect to the plane of motion of the X-ray tube target. In addition, body sections can be presented which are contoured to the patient's anatomy. That is to say, they may even encompass such complex surfaces as a quadratic hyperplane. In addition, tomograms of organs in motion can be imaged.

Baily, N. A.↗

NASA NTRS1981

Application of Computer Axial Tomography (CAT) to measuring crop canopy geometry

The feasibility of using the principles of computer axial topography (CAT) to quantify the structure of crop canopies was investigated because six variables are needed to describe the position-orientation with time of a small piece of canopy foliage. Several cross sections were cut through the foliage of healthy, green corn and soybean canopies in the dent and full pod development stages, respectively. A photograph of each cross section representing the intersection of a plane with the foliage was enlarged and the air-foliage boundaries delineated by the plane were digitized. A computer program was written and used to reconstruct the cross section of the canopy. The approach used in applying optical computer axial tomography to measuring crop canopy geometry shows promise of being able to provide needed geometric information for input data to canopy reflectance models. The difficulty of using the CAT scanner to measure large canopies of crops like corn is discussed and a solution is proposed involving the measurement of plants one at a time.

Bauer, M. E.↗

NASA NTRS1982

Model studies of laser absorption computed tomography for remote air pollution measurement

Model studies of the potential of laser absorption-computed tomography are presented which demonstrate the possibility of sensitive remote atmospheric pollutant measurements, over kilometer-sized areas, with two-dimensional resolution, at modest laser source powers. An analysis of this tomographic reconstruction process as a function of measurement SNR, laser power, range, and system geometry, shows that the system is able to yield two-dimensional maps of pollutant concentrations at ranges and resolutions superior to those attainable with existing, direct-detection laser radars.

Wolfe, D. C., Jr.↗

NASA NTRS1984

Tomography by iterative convolution - Empirical study and application to interferometry

An algorithm for computer tomography has been developed that is applicable to reconstruction from data having incomplete projections because an opaque object blocks some of the probing radiation as it passes through the object field. The algorithm is based on iteration between the object domain and the projection (Radon transform) domain. Reconstructions are computed during each iteration by the well-known convolution method. Although it is demonstrated that this algorithm does not converge, an empirically justified criterion for terminating the iteration when the most accurate estimate has been computed is presented. The algorithm has been studied by using it to reconstruct several different object fields with several different opaque regions. It also has been used to reconstruct aerodynamic density fields from interferometric data recorded in wind tunnel tests.

Vest, C. M.↗

NASA NTRS1985

Computed tomography for non-destructive evaluation of composites: Applications and correlations

The state-of-the-art fabrication techniques for composite materials are such that stringent species-specific acceptance criteria must be generated to insure product reliability. Non-destructive evaluation techniques including computed tomography (CT), X-ray radiography (RT), and ultrasonic scanning (UT) are investigated and compared to determine their applicability and limitations to graphite epoxy, carbon-carbon, and carbon-phenolic materials. While the techniques appear complementary, CT is shown to provide significant, heretofore unattainable data. Finally, a correlation of NDE techniques to destructive analysis is presented.

Goldberg, B.↗

NASA NTRS1985

Three-dimensional surface reconstruction for industrial computed tomography

Modern high resolution medical computed tomography (CT) scanners can produce geometrically accurate sectional images of many types of industrial objects. Computer software has been developed to convert serial CT scans into a three-dimensional surface form, suitable for display on the scanner itself. This software, originally developed for imaging the skull, has been adapted for application to industrial CT scanning, where serial CT scans thrrough an object of interest may be reconstructed to demonstrate spatial relationships in three dimensions that cannot be easily understood using the original slices. The methods of three-dimensional reconstruction and solid modeling are reviewed, and reconstruction in three dimensions from CT scans through familiar objects is demonstrated.

Vannier, M. W.↗

NASA NTRS1988

Interferometric tomography of continuous fields with incomplete projections

Interferometric tomography in the presence of an opaque object is investigated. The developed iterative algorithm does not need to augment the missing information. It is based on the successive reconstruction of the difference field, the difference between the object field to be reconstructed and its estimate, only in the difined region. The application of the algorithm results in stable convergence.

Cha, Soyoung S.↗

NASA NTRS1989

Interferometric tomography of continuous fields with incomplete projections

Interferometric tomography in the presence of an opaque object has been investigated. In principle the developed iterative algorithm does not need to augment the missing information. It is based on the successive reconstruction of the difference field, the difference between the object field to be reconstructed and its estimate, in the defined region only. The application of the algorithm results in stable convergence.

Cha, Soyoung S.↗

NASA NTRS1990

Calibrator Blocks For Computerized Tomography (CT)

Sets of calibrator blocks developed for use with industrial computerized tomography (CT) systems. Set of blocks (or number of stacked sets of blocks) placed on object table of CT system and scanned in usual way. Blocks include holes of known size, shape, and location. Appearance of holes in output image of CT system used to verify operation of system.

Engel, H. Peter↗

NASA NTRS1990

Viewing Welds By Computer Tomography

Computer tomography system used to inspect welds for root penetration. Source illuminates rotating welded part with fan-shaped beam of x rays or gamma rays. Detectors in circular array on opposite side of part intercept beam and convert it into electrical signals. Computer processes signals into image of cross section of weld. Image displayed on video monitor. System offers only nondestructive way to check penetration from outside when inner surfaces inaccessible.

Pascua, Antonio G.↗

NASA NTRS1990

Computed tomography used in weld inspections at NASA

This paper describes an application of computed tomography (CT) for an evaluation of a series of welding-end hydraulic accumulators in use at Kennedy Space Center, which were suspected of possibly containing fatigue cracks in their welds, the failure which could result in a high-velocity or high-volume leakage of hydraulic fluid. The accumulator welds were evaluated in terms of incomplete penetration, porosity, and incomplete fusion. Out of 43 accumulators examined, six were given the ranking of 'good', i.e., having no incomplete penetration, and only slight porosity and incomplete fusion. These were selected for use in most critical locations of the hydraulic system used to load the Magellan spacecraft into the payload bay of the Space Shuttle Discovery, with the resulting successful loading and subsequent launching of the Magellan spacecraft.

Murray, S. H.↗

NASA NTRS1991

Computed Tomography For Inspection Of Thermistors

Computed tomography (CT) enables identification of cracked thermistors without disassembly of equipment containing them. CT unit used to scan equipment and locate thermistors. Further scans made in various radial orientations perpendicular to plane of devices to find cracks. Cracks invisible in conventional x-radiographs seen.

Schaefer, Lloyd A.↗