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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

An Analysis of the Selected Materials Used in Step Measurements During Pre-Fits of Thermal Protection System Tiles and the Accuracy of Measurements Made Using These Selected Materials

The goal of this research project was be to compare and contrast the selected materials used in step measurements during pre-fits of thermal protection system tiles and to compare and contrast the accuracy of measurements made using these selected materials. The reasoning for conducting this test was to obtain a clearer understanding to which of these materials may yield the highest accuracy rate of exacting measurements in comparison to the completed tile bond. These results in turn will be presented to United Space Alliance and Boeing North America for their own analysis and determination. Aerospace structures operate under extreme thermal environments. Hot external aerothermal environments in high Mach number flights lead to high structural temperatures. The differences between tile heights from one to another are very critical during these high Mach reentries. The Space Shuttle Thermal Protection System is a very delicate and highly calculated system. The thermal tiles on the ship are measured to within an accuracy of .001 of an inch. The accuracy of these tile measurements is critical to a successful reentry of an orbiter. This is why it is necessary to find the most accurate method for measuring the height of each tile in comparison to each of the other tiles. The test results indicated that there were indeed differences in the selected materials used in step measurements during prefits of Thermal Protection System Tiles and that Bees' Wax yielded a higher rate of accuracy when compared to the baseline test. In addition, testing for experience level in accuracy yielded no evidence of difference to be found. Lastly the use of the Trammel tool over the Shim Pack yielded variable difference for those tests.

Kranz, David William↗
NASA NTRS2009

Optimization of OT-MACH Filter Generation for Target Recognition

An automatic Optimum Trade-off Maximum Average Correlation Height (OT-MACH) filter generator for use in a gray-scale optical correlator (GOC) has been developed for improved target detection at JPL. While the OT-MACH filter has been shown to be an optimal filter for target detection, actually solving for the optimum is too computationally intensive for multiple targets. Instead, an adaptive step gradient descent method was tested to iteratively optimize the three OT-MACH parameters, alpha, beta, and gamma. The feedback for the gradient descent method was a composite of the performance measures, correlation peak height and peak to side lobe ratio. The automated method generated and tested multiple filters in order to approach the optimal filter quicker and more reliably than the current manual method. Initial usage and testing has shown preliminary success at finding an approximation of the optimal filter, in terms of alpha, beta, gamma values. This corresponded to a substantial improvement in detection performance where the true positive rate increased for the same average false positives per image.

false alarm reduction↗
NASA NTRS1978

An unusual lightning flash at Kennedy Space Center

A lightning flash that struck the 150-meter weather tower at Kennedy Space Center was studied by several research groups using various techniques. The flash had unusually large peak currents and a stepped leader of relatively short duration. The charged regions neutralized by the three return strokes were located within a horizontal layer between heights of about 6 and 8 kilometers, where environmental temperatures were about -10 to -20 C. The charge source for the first return stroke coincided with a vertical shaft of precipitation inferred to have been graupel or hail. Charge sources for subsequent strokes were near the edge of the detectable precipitation echo. The overall channel length was about 10 kilometers. A vertically oriented intracloud discharge occurred after the three return strokes.

Uman, M. A.↗
NASA NTRS1992

The Galileo Energetic Particles Detector

Amongst its complement of particles and fields instruments, the Galileo spacecraft carries an Energetic Particles Detector (EPD) designed to measure the characteristics of particle populations important in determining the size, shape, and dynamics of the Jovian magnetosphere. To do this the EPD provides 4pi angular coverage and spectral measurements for Z greater than or equal to 1 ions from 20 keV to 55 MeV, for electrons from 15 keV to greater than 11 MeV, and for the elemental species helium through iron from approximately 10 keV/nucl to 15 MeV/nucl. Two bidirectional telescopes, mounted on a stepping platform, employ magnetic deflection, energy loss versus energy, and time-of-flight techniques to provide 64 rate channels and pulse height analysis of priority selected events. The EPD data system provides a large number of possible operational modes from which a small number will be selected to optimize data collection during the many encounter and cruise phases of the mission. The EPD employs a number of safeing algorithms that are to be used in the event that its self-checking procedures indicate a problem. The instrument and its operation are described.

Williams, D. J.↗
NASA NTRS1986

Evolution of lightning flash density and reflectivity structure in a multicell thunderstorm

The radar reflectivity structure and the distribution of lightning in a storm cell was investigated using S-band and UHF-band radar data for six storm cells over Wallops Island. The S-band scans were vertical and continuous, while the UHF data were taken in steps of 2.5 deg elevation. The peak in lightning activity during the study corresponded to a merging of two storm cells. A minimum height of 7 km was found necessary for the appearance of a 40 dBZ core with lightning, which first appears in a multicell thunderstorm at the leading edge of the 50 dBZ core of the cell and between a cell and its decaying neighbor. The lightning moves further into the cell during cell decay and decreases in density. Finally, the lightning is offset horizontally from the precipitation core during cell growth but colocates with the precipitation core as the cell dissipates.

Mazur, V.↗
NASA NTRS1999

Advanced Techniques for Assessment of Postural and Locomotor Ataxia, Spatial Orientation, and Gaze Stability

In addition to adapting to microgravity, major neurovestibular problems of space flight include postflight difficulties with standing, walking, turning corners, and other activities that require stable upright posture and gaze stability. These difficulties inhibit astronauts' ability to stand or escape from their vehicle during emergencies. The long-ter7n goal of the NSBRI is the development of countermeasures to ameliorate the effects of long duration space flight. These countermeasures must be tested with valid and reliable tools. This project aims to develop quantitative, parametric approaches for assessing gaze stability and spatial orientation during normal gait and when gait is perturbed. Two of this year's most important findings concern head fixation distance and ideal trajectory analysis. During a normal cycle of walking the head moves up and down linearly. A simultaneous angular pitching motion of the head keeps it aligned toward an imaginary point in space at a distance of about one meter in front of a subject and along the line of march. This distance is called the head fixation distance. Head fixation distance provides the fundamental framework necessary for understanding the functional significance of the vestibular reflexes that couple head motion to eye motion. This framework facilitates the intelligent design of counter-measures for the effects of exposure to microgravity upon the vestibular ocular reflexes. Ideal trajectory analysis is a simple candidate countermeasure based upon quantifying body sway during repeated up and down stair stepping. It provides one number that estimates the body sway deviation from an ideal sinusoidal body sway trajectory normalized on the subject's height. This concept has been developed with NSBRI funding in less than one year. These findings are explained in more detail below. Compared to assessments of the vestibuo-ocular reflex, analysis of vestibular effects on locomotor function is relatively less well developed and quantified. We are improving this situation by applying methodologies such as nonlinear orbital stability to quantify responses and by using multivariate statistical approaches to link together the responses across separate tests. In this way we can exploit the information available and increase the ability to discriminate between normal and pathological responses. Measures of stability and orientation are compared to measures such as dynamic visual acuity and with balance function tests. The responses of normal human subjects and of patients having well documented pathophysiologies are being characterized. When these studies are completed, we should have a clearer idea about normal and abnormal patterns of eye, head, and body movements during locomotion and their stability in a wide range of environments. We plan eventually to use this information to validate the efficacy of candidate neurovestibular and neuromuscular rehabilitative techniques. Some representative studies made during this year are summarized.

Wall, Conrad., III↗
NASA NTRS1977

Remote sensing of vegetation and soil using microwave ellipsometry

A method is described of determining vegetation height and water content of vegetation from the intensity and state of elliptical polarization of a reflected train of microwaves. The method comprises the steps of reflecting a circularly polarized train of microwaves from vegetation at a predetermined angle of incidence and detecting the reflected train of microwaves. The ratio of the intensities of the electric field vector components is determined, the phase difference of the components is measured, and the refractive index and thickness of the layer of vegetation are computed from a formula. The refractive index is given essentially by the water content of the vegetation.

Auer, S. O.↗
NASA NTRS2013

Airborne Measurements of CO2 Column Concentration and Range Using a Pulsed Direct-Detection IPDA Lidar

We have previously demonstrated a pulsed direct detection IPDA lidar to measure range and the column concentration of atmospheric CO2. The lidar measures the atmospheric backscatter profiles and samples the shape of the 1,572.33 nm CO2 absorption line. We participated in the ASCENDS science flights on the NASA DC-8 aircraft during August 2011 and report here lidar measurements made on four flights over a variety of surface and cloud conditions near the US. These included over a stratus cloud deck over the Pacific Ocean, to a dry lake bed surrounded by mountains in Nevada, to a desert area with a coal-fired power plant, and from the Rocky Mountains to Iowa, with segments with both cumulus and cirrus clouds. Most flights were to altitudes >12 km and had 5-6 altitude steps. Analyses show the retrievals of lidar range, CO2 column absorption, and CO2 mixing ratio worked well when measuring over topography with rapidly changing height and reflectivity, through thin clouds, between cumulus clouds, and to stratus cloud tops. The retrievals shows the decrease in column CO2 due to growing vegetation when flying over Iowa cropland as well as a sudden increase in CO2 concentration near a coal-fired power plant. For regions where the CO2 concentration was relatively constant, the measured CO2 absorption lineshape (averaged for 50 s) matched the predicted shapes to better than 1% RMS error. For 10 s averaging, the scatter in the retrievals was typically 2-3 ppm and was limited by the received signal photon count. Retrievals were made using atmospheric parameters from both an atmospheric model and from in situ temperature and pressure from the aircraft. The retrievals had no free parameters and did not use empirical adjustments, and >70% of the measurements passed screening and were used in analysis. The differences between the lidar-measured retrievals and in situ measured average CO2 column concentrations were <1.4 ppm for flight measurement altitudes >6 km.

Lidar↗
NASA NTRS2012

Method for Pre-Conditioning a Measured Surface Height Map for Model Validation

This software allows one to up-sample or down-sample a measured surface map for model validation, not only without introducing any re-sampling errors, but also eliminating the existing measurement noise and measurement errors. Because the re-sampling of a surface map is accomplished based on the analytical expressions of Zernike-polynomials and a power spectral density model, such re-sampling does not introduce any aliasing and interpolation errors as is done by the conventional interpolation and FFT-based (fast-Fourier-transform-based) spatial-filtering method. Also, this new method automatically eliminates the measurement noise and other measurement errors such as artificial discontinuity. The developmental cycle of an optical system, such as a space telescope, includes, but is not limited to, the following two steps: (1) deriving requirements or specs on the optical quality of individual optics before they are fabricated through optical modeling and simulations, and (2) validating the optical model using the measured surface height maps after all optics are fabricated. There are a number of computational issues related to model validation, one of which is the "pre-conditioning" or pre-processing of the measured surface maps before using them in a model validation software tool. This software addresses the following issues: (1) up- or down-sampling a measured surface map to match it with the gridded data format of a model validation tool, and (2) eliminating the surface measurement noise or measurement errors such that the resulted surface height map is continuous or smoothly-varying. So far, the preferred method used for re-sampling a surface map is two-dimensional interpolation. The main problem of this method is that the same pixel can take different values when the method of interpolation is changed among the different methods such as the "nearest," "linear," "cubic," and "spline" fitting in Matlab. The conventional, FFT-based spatial filtering method used to eliminate the surface measurement noise or measurement errors can also suffer from aliasing effects. During re-sampling of a surface map, this software preserves the low spatial-frequency characteristic of a given surface map through the use of Zernike-polynomial fit coefficients, and maintains mid- and high-spatial-frequency characteristics of the given surface map by the use of a PSD model derived from the two-dimensional PSD data of the mid- and high-spatial-frequency components of the original surface map. Because this new method creates the new surface map in the desired sampling format from analytical expressions only, it does not encounter any aliasing effects and does not cause any discontinuity in the resultant surface map.

Sidick, Erkin↗
NASA NTRS2009

Pulsed Airborne Lidar Measurements of Atmospheric CO2 Column Absorption and Line Shapes from 3-13 km Altitudes

We have developed a lidar technique for measuring the tropospheric C02 concentrations as a candidate for NASA's planned ASCENDS mission. Our technique uses two pulsed laser transmitters allowing simultaneous measurement of a C02 absorption line in the 1570 nm band, 02 extinction in the Oxygen A-band and surface height and backscatter. The lidar measures the energy and time of flight of the laser echoes reflected from the atmosphere and surface. The lasers are stepped in wavelength across the C02 line and an 02 line region during the measurement. The receiver uses a telescope and photon counting detectors, and measures the background light and energies of the laser echoes from the surface along with scattering from any aerosols in the path. The gas extinction and column densities for the C02 and 02 gases are estimated from the ratio of the on- and off- line signals via the DIAL technique. Time gating is used to isolate the laser echo signals from the surface, and to reject laser photons scattered in the atmosphere. We have developed an airborne lidar to demonstrate the C02 measurement from the NASA Glenn Lear 25 aircraft. The airborne lidar steps the pulsed laser's wavelength across a selected C02 line with 20 steps per scan. The line scan rate is 450 Hz and laser pulse widths are I usec. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a photomultiplier and is recorded by a photon counting system. We made initial airborne measurements on flights during October and December 2008. Laser backscatter and absorption measurements were made over a variety of land and water surfaces and through thin and broken clouds. Atmospheric C02 column measurements using the 1571.4, 1572.02 and 1572.33 nm C02 lines. Two flights were made above the DOE SGP ARM site at altitudes from 3-8 km. These nights were coordinated with DOE investigators who Hew an in-situ C02 sensor on a Cessna aircraft under the path. The increasing C02 line absorptions with altitudes were evident and comparison with in-situ measurements showed agreements to 6 ppm. This spring we improved the aircraft's nadir window. During July and August 2009 we made 9 additional 2 hour long flights and measured the atmospheric C02 absorption and line shapes using the 1572.33 nm C02 line. Measurements were made at stepped altitudes from 3-13 km over a variety of surface types in Nebraska, Illinois, the SGP ARM site, and near and over the Chesapeake Bay in North Carolina and Virginia. Strong laser signals and clear line shapes were observed at all altitudes, and some measurements were made through thin clouds. The flights over the ARM site were underflown with in-situ measurements made from the DOE Cessna. The Oklahoma and east coast t1ights were coordinated with a LaRC/ITT C02 lidar on the LaRC UC-12 aircraft, a LaRC in~situ C02 sensor, and the Oklahoma flights also included a JPL C02 lidar on a Twin Otter aircraft. Ed Browell and Gary Spiers led the LaRC and JPL teams. More details of the t1ights, measurements and analysis will be described in the presentation.

Abshire, J. B.↗
NASA NTRS2019

Diurnal and Seasonal Solar Induced Chlorophyll Fluorescence and Photosynthesis in a Boreal Scots Pine Canopy

Solar induced chlorophyll fluorescence has been shown to be increasingly an useful proxy for the estimation of gross primary productivity (GPP), at a range of spatial scales. Here, we explore the seasonality in a continuous time series of canopy solar induced fluorescence (hereafter SiF) and its relation to canopy gross primary production (GPP), canopy light use efficiency (LUE), and direct estimates of leaf level photochemical efficiency in an evergreen canopy. SiF was calculated using infilling in two bands from the incoming and reflected radiance using a pair of Ocean Optics USB2000+ spectrometers operated in a dual field of view mode, sampling at a 30 min time step using custom written automated software, from early spring through until autumn in 2011. The optical system was mounted on a tower of 18 m height adjacent to an eddy covariance system, to observe a boreal forest ecosystem dominated by Scots pine. (Pinus sylvestris) A Walz MONITORING-PAM, multi fluorimeter system, was simultaneously mounted within the canopy adjacent to the footprint sampled by the optical system. Following correction of the SiF data for O2 and structural effects, SiF, SiF yield, LUE, the photochemicsl reflectance index (PRI), and the normalized difference vegetation index (NDVI) exhibited a seasonal pattern that followed GPP sampled by the eddy covariance system. Due to the complexities of solar azimuth and zenith angle (SZA) over the season on the SiF signal, correlations between SiF, SiF yield, GPP, and LUE were assessed on SZA <50° and under strictly clear sky conditions. Correlations found, even under these screened scenarios, resulted around ~r2 = 0.3. The diurnal responses of SiF, SiF yield, PAM estimates of effective quantum yield (ΔF/Fm′), and meteorological parameters demonstrated some agreement over the diurnal cycle. The challenges inherent in SiF retrievals in boreal evergreen ecosystems are discussed.

photosynthetic↗
NASA NTRS1990

Fiber-optic projected-fringe digital interferometry

A phase-stepped projected-fringe interferometer was developed which uses a closed-loop fiber-optic phase-control system to make very accurate surface profile measurements. The closed-loop phase-control system greatly reduces phase-stepping error, which is frequently the dominant source of error in digital interferometers. Two beams emitted from a fiber-optic coupler are combined to form an interference fringe pattern on a diffusely reflecting object. Reflections off of the fibers' output faces are used to create a phase-indicating signal for the closed-loop optical phase controller. The controller steps the phase difference between the two beams by pi/2 radians in order to determine the object's surface profile using a solid-state camera and a computer. The system combines the ease of alignment and automated data reduction of phase-stepping projected-fringe interferometry with the greatly improved phase-stepping accuracy of our closed-loop phase-controller. The system is demonstrated by measuring the profile of a plate containing several convex surfaces whose heights range from 15 to 25 micron high.

Mercer, Carolyn R.↗
NASA NTRS1992

Modelling and performance of Nb SIS mixers in the 1.3 mm and 0.8 mm bands

We describe the modeling and subsequent improvements of SIS waveguide mixers for the 200-270 and 330-370 GHz bands (Blundell, Carter, and Gundlach 1988, Carter et al 1991). These mixers are constructed for use in receivers on IRAM radiotelescopes on Pico Veleta (Spain, Sierra Nevada) and Plateau de Bure (French Alps), and must meet specific requirements. The standard reduced height waveguide structure with suspended stripline is first analyzed and a model is validated through comparison with scale model and working scale measurements. In the first step, the intrinsic limitations of the standard mixer structure are identified, and the parameters are optimized bearing in mind the radioastronomical applications. In the second step, inductive tuning of the junctions is introduced and optimized for minimum noise and maximum bandwidth. In the 1.3 mm band, a DSB receiver temperature of less than 110 K (minimum 80 K) is measured from 180 through 260 GHz. In the 0.8 mm band, a DSB receiver temperature of less than 250 K (minimum 175 K) is obtained between 325 and 355 GHz. All these results are obtained with room-temperature optics and a 4 GHz IF chain having a 500 MHz bandwidth and a noise temperature of 14 K.

Karpov, A.↗
NASA NTRS2003

Satellite and Surface Data Synergy for Developing a 3D Cloud Structure and Properties Characterization Over the ARM SGP. Stage 1: Cloud Amounts, Optical Depths, and Cloud Heights Reconciliation

One of the primary Atmospheric Radiation Measurement (ARM) Program objectives is to obtain measurements applicable to the development of models for better understanding of radiative processes in the atmosphere. We address this goal by building a three-dimensional (3D) characterization of the cloud structure and properties over the ARM Southern Great Plains (SGP). We take the approach of juxtaposing the cloud properties as retrieved from independent satellite and ground-based retrievals, and looking at the statistics of the cloud field properties. Once these retrievals are well understood, they will be used to populate the 3D characterization database. As a first step we determine the relationship between surface fractional sky cover and satellite viewing angle dependent cloud fraction (CF). We elaborate on the agreement intercomparing optical depth (OD) datasets from satellite and ground using available retrieval algorithms with relation to the CF, cloud height, multi-layer cloud presence, and solar zenith angle (SZA). For the SGP Central Facility, where output from the active remote sensing cloud layer (ARSCL) valueadded product (VAP) is available, we study the uncertainty of satellite estimated cloud heights and evaluate the impact of this uncertainty for radiative studies.

Genkova, I.↗
NASA NTRS1988

Particle acceleration in impulsive solar flares

A model for second-step electron acceleration in impulsive solar flares is presented. The theory of stochastic particle acceleration is extended to include Coulomb energy losses which become important at low coronal heights. This inclusion successfully explains the observed steepening of interplanetary electron spectra below about 3 MeV following impulsive solar flares taking place at low coronal heights. It also explains the observed spectral differences of relativistic electrons in long-duration and impulsive flares.

Steinacker, J.↗
NASA NTRS2000

Sensitivity of Age-of-Air Calculations to the Choice of Advection Scheme

The age of air has recently emerged as a diagnostic of atmospheric transport unaffected by chemical parameterizations, and the features in the age distributions computed in models have been interpreted in terms of the models' large-scale circulation field. This study shows, however, that in addition to the simulated large-scale circulation, three-dimensional age calculations can also be affected by the choice of advection scheme employed in solving the tracer continuity equation, Specifically, using the 3.0deg latitude X 3.6deg longitude and 40 vertical level version of the Geophysical Fluid Dynamics Laboratory SKYHI GCM and six online transport schemes ranging from Eulerian through semi-Lagrangian to fully Lagrangian, it will be demonstrated that the oldest ages are obtained using the nondiffusive centered-difference schemes while the youngest ages are computed with a semi-Lagrangian transport (SLT) scheme. The centered- difference schemes are capable of producing ages older than 10 years in the mesosphere, thus eliminating the "young bias" found in previous age-of-air calculations. At this stage, only limited intuitive explanations can be advanced for this sensitivity of age-of-air calculations to the choice of advection scheme, In particular, age distributions computed online with the National Center for Atmospheric Research Community Climate Model (MACCM3) using different varieties of the SLT scheme are substantially older than the SKYHI SLT distribution. The different varieties, including a noninterpolating-in-the-vertical version (which is essentially centered-difference in the vertical), also produce a narrower range of age distributions than the suite of advection schemes employed in the SKYHI model. While additional MACCM3 experiments with a wider range of schemes would be necessary to provide more definitive insights, the older and less variable MACCM3 age distributions can plausibly be interpreted as being due to the semi-implicit semi-Lagrangian dynamics employed in the MACCM3. This type of dynamical core (employed with a 60-min time step) is likely to reduce SLT's interpolation errors that are compounded by the short-term variability characteristic of the explicit centered-difference dynamics employed in the SKYHI model (time step of 3 min). In the extreme case of a very slowly varying circulation, the choice of advection scheme has no effect on two-dimensional (latitude-height) age-of-air calculations, owing to the smooth nature of the transport circulation in 2D models. These results suggest that nondiffusive schemes may be the preferred choice for multiyear simulations of tracers not overly sensitive to the requirement of monotonicity (this category includes many greenhouse gases). At the same time, age-of-air calculations offer a simple quantitative diagnostic of a scheme's long-term diffusive properties and may help in the evaluation of dynamical cores in multiyear integrations. On the other hand, the sensitivity of the computed ages to the model numerics calls for caution in using age of air as a diagnostic of a GCM's large-scale circulation field.

Eluszkiewicz, Janusz↗
NASA NTRS1972

Experimental physics characteristics of a heavy-metal-reflected fast-spectrum critical assembly

A zero-power critical assembly was designed, constructed, and operated for the purpose of conducting a series of benchmark experiments dealing with the physics characteristics of a UN-fueled, Li-cooled, Mo-reflected, drum-controlled compact fast reactor for use with a space-power electric conversion system. The range of the previous experimental investigations has been expanded to include the reactivity effects of:(1) surrounding the reactor with 15.24 cm (6 in.) of polyethylene, (2) reducing the heights of a portion of the upper and lower axial reflectors by factors of 2 and 4, (3) adding 45 kg of W to the core uniformly in two steps, (4) adding 9.54 kg of Ta to the core uniformly, and (5) inserting 2.3 kg of polyethylene into the core proper and determining the effect of a Ta addition on the polyethylene worth.

Heneveld, W. H.↗
NASA NTRS2001

One-step Tape Casting of Composites via Slurry on Fiber

A process by which metal matrix composites can be made was presented. The process involves putting a powder slurry on fibers to make a precursor green tape. These green tapes are cut, stacked and hot pressed to form the fully dense composite. A computer program was presented which enables complete quantification and control of the process. Once some easily obtained properties of the slurry and its behavior are determined (such as the shrinkage from the wet to green state, and the density of the green tape) modification of the fiber spacing and blade height give the maker precise control of fiber volume fraction, and fiber architecture in the composite. The process was shown to be accurate and flexible through the production of a wide variety of volume fraction fiber composites made from a wide variety of fibers and powders. The most time consuming step of the tape casting process (other than hot pressing) was winding the fiber on the drum. The tape casting techniques developed resulted in high quality metal matrix composites, with ultimate tensile strength in the range of 215 ksi (1477 MPa), a strain at failure of 1.15 percent, and in fatigue at room temperature 0 to 120 ksi, n = 0.3 Hz, a 4-ply Ti-24Al-11Nb/SCS-6, 32 vol% fiber tape cast composite lasted 202,205 cycles with a maximum strain on the 100th cycle of 0.43 percent.

deGroh, Henry C., III↗