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At least 595 records · Page 33

Space Operations for a New Era of Exploration Launch Vehicles

NASA's Constellation Program is depending on the Ares Projects to deliver the crew and cargo launch capabilities needed to send human explorers to the Moon and beyond. Ares I and V will provide the core space launch capabilities needed to continue providing crew and cargo access to the International Space Station (ISS), and to build upon the U.S. history of human space exploration. Since 2005, Ares has made substantial progress on designing, developing, and testing the Ares I crew launch vehicle and has continued its in-depth studies of the Ares V cargo launch vehicles. The combined Ares I/Ares V architecture has been designed to reduce the complexity and labor intensity of ground operations for America's next journeys beyond low-Earth orbit (LEO). A deliberate effort is being made to ensure a high level of system operability to significantly increase safety and system availability as well as reduce recurring costs for this new launch vehicle. The Ares Projects goal is to instill operability as part of the vehicles requirements development, design, and operations. This simplicity will come from using simpler, proven engine designs, as in the case of the J-2X upper stage engine and RS-68 engine; improving existing hardware, as in the case of the Shuttle-heritage 5-segment solid rocket motor; and using common propulsion and instrument unit elements between Ares I and Ares V. Furthermore, lessons learned while developing Ares I will be applied directly to Ares V operations. In 2009, the Ares Projects plan to conduct the first flight test of Ares I, designated Ares I-X. Ares I-X preparations have already prompted changes to the vehicle stacking and launch infrastructure at Kennedy Space Center (KSC), including removing Shuttle-specific fixtures from the Vehicle Assembly Building (VAB) to accommodate Ares I-style stacking operations, new firing room computers and infrastructure in the VAB Launch Control Center, and new lightning protection system towers at Launch Complex 39B to accommodate the greater height of Ares I-X. In addition to lessons learned from the stacking of Ares I-X, the flight test itself promises to yield important data and operations lessons for assembling, launching, and flying Ares I.

Cook, Stephen A.↗

Arc-Second Alignment of International X-Ray Observatory Mirror Segments in a Fixed Structure

The optics for the International X-Ray Observatory (IXO) require alignment and integration of about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arc-seconds. These mirror segments are 0.4 mm thick, and 200 to 400 mm in size, which makes it hard to meet the strict angular resolution requirement of 5 arc-seconds for the telescope. This paper outlines the precise alignment, verification testing, and permanent bonding techniques developed at NASA's Goddard Space Flight Center (GSFC). These techniques are used to overcome the challenge of transferring thin mirror segments from a temporary mount to a fixed structure with arc-second alignment and minimal figure distortion. Recent advances in technology development in addition to the automation of several processes have produced significant results. Recent advances in the mirror fixture process known as the suspension mount has allowed for a mirror to be mounted to a fixture with minimal distortion. Once on the fixture, mirror segments have been aligned to around 5 arc-seconds which is halfway to the goal of 2.5 arc-seconds per mirror segment. This paper will highlight the recent advances in alignment, testing, and permanent bonding techniques as well as the results they have produced.

Evans, Tyler, C.↗

Preliminary Solar Sail Design and Fabrication Assessment: Spinning Sail Blade, Square Sail Sheet

Blade design aspects most affecting producibility and means of measurement and control of length, scallop, fullness and straightness requirements and tolerances were extensively considered. Alternate designs of the panel seams and edge reinforcing members are believed to offer advantages of seam integrity, producibility, reliability, cost and weight. Approaches to and requirements for highly specialized metalizing methods, processes and equipment were studied and identified. Alternate methods of sail blade fabrication and related special machinery, tooling, fixtures and trade offs were examined. A preferred and recommended approach is also described. Quality control plans, inspection procedures, flow charts and special test equipment associated with the preferred manufacturing method were analyzed and are discussed.

Daniels, J. B.↗

Microelectronics Instrument Products Shock and Vibration Electro-Optics: Acceptance Data Package - Section B

The motor/encoder (henceforth referred to as the UUT) test sequence began with a baseline functional evaluation, which demonstrated that the motor satisfied the operating torque, cogging torque, winding resistance, and mechanical requirements of SOW. In addition, the encoder electrical requirements were verified, as well as the alignment of the encoder outputs relative to the motor shaft position. There were no discrepancies observed in this portion of the test. The UUT was then exposed to a number of environments, including thermal vacuum, thermal cycling, random and sine vibration, and mechanical shock. During the thermal environments, the performance of the UUT under load was verified at specified points in the cycles, as described in ATP 20049. In addition, the UUT was bench tested between the two thermal environments. No anomalies were observed during the thermal tests. The vibration and shock tests were performed by East-West Technology Corporation, West Babylon, New York. The UUT was delivered to the lab in a sealed vibration fixture in order to maintain the cleanliness levels required by the SOW. In addition, a three ounce load was attached to the motor shaft. The attachment method of this load caused damage to the shaft and bearing during random vibration of S/N 0003 on April 28, 1995, and is described further in NCR 00168.

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A TEOM (tm) particulate monitor for comet dust, near Earth space, and planetary atmospheres

Scientific missions to comets, near earth space, and planetary atmospheres require particulate and mass accumulation instrumentation for both scientific and navigation purposes. The Rupprecht & Patashnick tapered element oscillating microbalance can accurately measure both mass flux and mass distribution of particulates over a wide range of particle sizes and loadings. Individual particles of milligram size down to a few picograms can be resolved and counted, and the accumulation of smaller particles or molecular deposition can be accurately measured using the sensors perfected and toughened under this contract. No other sensor has the dynamic range or sensitivity attained by these picogram direct mass measurement sensors. The purpose of this contract was to develop and implement reliable and repeatable manufacturing methods; build and test prototype sensors; and outline a quality control program. A dust 'thrower' was to be designed and built, and used to verify performance. Characterization and improvement of the optical motion detection system and drive feedback circuitry was to be undertaken, with emphasis on reliability, low noise, and low power consumption. All the goals of the contract were met or exceeded. An automated glass puller was built and used to make repeatable tapered elements. Materials and assembly methods were standardized, and controllers and calibrated fixtures were developed and used in all phases of preparing, coating and assembling the sensors. Quality control and reliability resulted from the use of calibrated manufacturing equipment with measurable working parameters. Thermal and vibration testing of completed prototypes showed low temperature sensitivity and high vibration tolerance. An electrostatic dust thrower was used in vacuum to throw particles from 2 x 10(exp 6) g to 7 x 10(exp -12) g in size. Using long averaging times, particles as small as 0.7 to 4 x 10(exp 11) g were weighted to resolutions in the 5 to 9 x 10(exp -13) g range. The drive circuit and optics systems were developed beyond what was anticipated in the contract, and are now virtually flight prototypes. There is already commercial interest in the developed capability of measuring picogram mass losses and gains. One area is contamination and outgassing research, both measuring picogram losses from samples and collecting products of outgassing.

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A micrographic study of bending failure in five thermoplastic/carbon fiber composite laminates

The local deformation and failure sequences of five thermoplastic matrix composites were microscopically observed while bending the samples in a small fixture attached to a microscope stage. The themoplastics are polycarbonate, polysulfone, polyphenylsulfide, polyethersulfone, and polyetheretherketone. Comparison was made to an epoxy matrix composite, 5208/T-300. Laminates tested are (0/90) sub 2S, with outer ply fibers parallel to the beam axis. Four point bending was used at a typical span-to-thickness ratio of 39:1. It was found that all of the thermoplastic composites failed by abrupt longitudinal compression buckling of the outer ply. Very little precursory damage was observed. Micrographs reveal typical fiber kinking associated with longitudinal compression failure. Curved fracture surfaces on the fibers suggest they failed in bending rather than direct compression. Delamination was suppressed in the thermoplastic composites, and the delamination that did occur was found to be the result of compression buckling, rather than visa-versa. Microbuckling also caused other subsequent damage such as ply splitting, transverse ply shear failure, fiber tensile failure, and transverse ply cracking.

Yurgartis, S. W.↗

A micrographic study of bending failure in five thermoplastic-carbon fibre composite laminates

The local deformation and failure sequences of five thermoplastic matrix composites were microscopically observed while bending the samples in a small fixture attached to a microscope stage. The thermoplastics are polycarbonate, polysulfane, polyphenylsulfide, polyethersulfane, and polyetheretherketone. Comparison was made to an epoxy matrix composite, 5208/T-300. Laminates tested are (0/90) sub 2S, with outer ply fibers parallel to the beam axis. Four point bending was used at a typical span-to-thickness ratio of 39:1. It was found that all of the thermoplastic composites failed by abrupt longitudinal compression buckling of the outer ply. Very little precursory damage was observed. Micrographs reveal typical fiber kinking associated with longitudinal compression failure. Curved fracture surfaces on the fibers suggest they failed in bending rather than direct compression. Delamination was suppressed in the thermoplastic composites, and the delamination that did occur was found to be the result of compression buckling, rather than vice-versa. Microbuckling also caused other subsequent damage such as ply splitting, transverse ply shear failure, fiber tensile failure, and transverse ply cracking.

Yurgartis, S. W.↗

Design and Characterization of Thin Stainless Steel Burst Disks for Increasing Two-Stage Light Gas Launcher Efficiency

Laser etched 300 series Stainless Steel Burst Disks (SSBD) ranging between 0.178 mm (0.007-in.) and 0.508mm (0.020-in.) thick were designed for use in a 17-caliber two-stage light gas launcher. First, a disk manufacturing method was selected using a combination of wire electrical discharge machining (EDM) to form the blank disks and laser etching to define the pedaling fracture pattern. Second, a replaceable insert was designed to go between the SSDB and the barrel. This insert reduced the stress concentration between the SSBD and the barrel, providing a place for the petals of the SSDB to open, and protecting the rifling on the inside of the barrel. Thereafter, a design of experiments was implemented to test and characterize the burst characteristics of SSBDs. Extensive hydrostatic burst testing of the SSBDs was performed to complete the design of experiments study with one-hundred and seven burst tests. The experiment simultaneously tested the effects of the following: two SSBD material states (full hard, annealed); five SSBD thicknesses 0.178, 0.254, 0.305, 0.381 mm (0.007, 0.010, 0.012, 0.015, 0.020-in.); two grain directions relative); number of times the laser etch pattern was repeated (varies between 5-200 times); two heat sink configurations (with and without heat sink); and, two barrel configurations (with and without insert). These tests resulted in the quantification of the relationship between SSBD thickness, laser etch parameters, and desired burst pressure. Of the factors investigated only thickness and number of laser etches were needed to develop a mathematical relationship predicting hydrostatic burst pressure of disks using the same barrel configuration. The fracture surfaces of two representative SSBD bursts were then investigated with a scanning electron microscope, one burst hydrostatically in a fixture and another dynamically in the launcher. The fracture analysis verified that both burst conditions resulted in a ductile overload failure indicated by transgranular microvoid coalescence, non-fragmenting rupture and mixed tensile and shear failure modes, regardless of the material states tested. More testing is underway to determine the relationship between SSBD burst pressure and projectile velocity.

Tylka, Jonathan M.↗

Net shape fabrication of Alpha Silicon Carbide turbine components

Development of Alpha Silicon Carbide components by net shape fabrication techniques has continued in conjunction with several turbine engine programs. Progress in injection molding of simple parts has been extended to much larger components. Turbine rotors fabricated by a one piece molding have been successfully spin tested above design speeds. Static components weighing up to 4.5 kg and 33 cc in diameter have also been produced using this technique. Use of sintering fixtures significantly improves dimensional control. A new Si-SiC composite material has also been developed with average strengths up to 1000 MPa (150 ksi) at 1200 C.

Storm, R. S.↗

Controlled linear clamper/loader

Pneumatic fixture can be used to clamp odd-shaped parts to non-uniform surface. Device can be made from nonmagnetic materials for use in magnetic field test environments. It also applies uniform load over clamped surface.

Steudl, R. M.↗

Electronic Nose Development and Preliminary Human Breath Testing for Rapid, Non-Invasive COVID-19 Detection

We adapted an existing, spaceflight-proven, robust “electronic nose” (E-Nose) that uses an array of electrical resistivity-based nanosensors mimicking aspects of mammalian olfaction to conduct on-site, rapid screening for COVID-19 infection by measuring the pattern of sensor responses to volatile organic compounds (VOCs) in exhaled human breath. We built and tested multiple copies of a hand-held prototype E-Nose sensor system, composed of 64 chemically sensitive nanomaterial sensing elements tailored to COVID-19 VOC detection; data acquisition electronics; a smart tablet with software (App) for sensor control, data acquisition and display; and a sampling fixture to capture exhaled breath samples and deliver them to the sensor array inside the E-Nose. The sensing elements detect the combination of VOCs typical in breath at parts-per-billion (ppb) levels, with repeatability of 0.02% and reproducibility of 1.2%; the measurement electronics in the E-Nose provide measurement accuracy and signal-to-noise ratios comparable to benchtop instrumentation. Preliminary clinical testing at Stanford Medicine with 63 participants, their COVID-19-positive or COVID-19-negative status determined by concomitant RT-PCR, discriminated between these two categories of human breath with a 79% correct identification rate using “leave-one-out” training-and-analysis methods. Analyzing the E-Nose response in conjunction with body temperature and other non-invasive symptom screening using advanced machine learning methods, with a much larger database of responses from a wider swath of the population, is expected to provide more accurate on-the-spot answers. Additional clinical testing, design refinement, and a mass manufacturing approach are the main steps toward deploying this technology to rapidly screen for active infection in clinics and hospitals, public and commercial venues, or at home.

COVID-19↗

Research Capabilities for Oil-Free Turbomachinery Expanded by New Rotordynamic Simulator Facility

A new test rig has been developed for simulating high-speed turbomachinery shafting using Oil-Free foil air bearing technology. Foil air journal bearings are self-acting hydrodynamic bearings with a flexible inner sleeve surface using air as the lubricant. These bearings have been used in turbomachinery, primarily air cycle machines, for the past four decades to eliminate the need for oil lubrication. More recently, interest has been growing in applying foil bearings to aircraft gas turbine engines. They offer potential improvements in efficiency and power density, decreased maintenance costs, and other secondary benefits. The goal of applying foil air bearings to aircraft gas turbine engines prompted the fabrication of this test rig. The facility enables bearing designers to test potential bearing designs with shafts that simulate the rotating components of a target engine without the high cost of building actual flight hardware. The data collected from this rig can be used to make changes to the shaft and bearings in subsequent design iterations. The rest of this article describes the new test rig and demonstrates some of its capabilities with an initial simulated shaft system. The test rig has two support structures, each housing a foil air journal bearing. The structures are designed to accept any size foil journal bearing smaller than 63 mm (2.5 in.) in diameter. The bearing support structures are mounted to a 91- by 152-cm (3- by 5-ft) table and can be separated by as much as 122 cm (4 ft) and as little as 20 cm (8 in.) to accommodate a wide range of shaft sizes. In the initial configuration, a 9.5-cm (3.75-in.) impulse air turbine drives the test shaft. The impulse turbine, as well as virtually any number of "dummy" compressor and turbine disks, can be mounted on the shaft inboard or outboard of the bearings. This flexibility allows researchers to simulate various engine shaft configurations. The bearing support structures include a unique bearing mounting fixture that rotates to accommodate a laserbased alignment system. This can measure the misalignment of the bearing centers in each of 2 translational degrees of freedom and 2 rotational degrees of freedom. In the initial configuration, with roughly a 30.5-cm- (12-in.-) long shaft, two simulated aerocomponent disks, and two 50.8-cm (2-in.) foil journal bearings, the rig can operate at 65,000 rpm at room temperature. The test facility can measure shaft displacements in both the vertical and horizontal directions at each bearing location. Horizontal and vertical structural vibrations are monitored using accelerometers mounted on the bearing support structures. This information is used to determine system rotordynamic response, including critical speeds, mode shapes, orbit size and shape, and potentially the onset of instabilities. Bearing torque can be monitored as well to predict the power loss in the foil bearings. All of this information is fed back and forth between NASA and the foil bearing designers in an iterative fashion to converge on a final bearing and shaft design for a given engine application. In addition to its application development capabilities, the test rig offers several unique capabilities for basic bearing research. Using the laser alignment system mentioned earlier, the facility will be used to map foil air journal bearing performance. A known misalignment of increasing severity will be induced to determine the sensitivity of foil bearings to misalignment. Other future plans include oil-free integral starter generator testing and development, and dynamic load testing of foil journal bearings.

Howard, Samuel A.↗

NASA Tech Briefs, June 2011

Topics covered include: Wind and Temperature Spectrometry of the Upper Atmosphere in Low-Earth Orbit; Health Monitor for Multitasking, Safety-Critical, Real-Time Software; Stereo Imaging Miniature Endoscope; Early Oscillation Detection Technique for Hybrid DC/DC Converters; Parallel Wavefront Analysis for a 4D Interferometer; Schottky Heterodyne Receivers With Full Waveguide Bandwidth; Carbon Nanofiber-Based, High-Frequency, High-Q, Miniaturized Mechanical Resonators; Ultracapacitor-Based Uninterrupted Power Supply System; Coaxial Cables for Martian Extreme Temperature Environments; Using Spare Logic Resources To Create Dynamic Test Points; Autonomous Coordination of Science Observations Using Multiple Spacecraft; Autonomous Phase Retrieval Calibration; EOS MLS Level 1B Data Processing Software, Version 3; Cassini Tour Atlas Automated Generation; Software Development Standard Processes (SDSP); Graphite Composite Panel Polishing Fixture; Material Gradients in Oxygen System Components Improve Safety; Ridge Waveguide Structures in Magnesium-Doped Lithium Niobate; Modifying Matrix Materials to Increase Wetting and Adhesion; Lightweight Magnetic Cooler With a Reversible Circulator; The Invasive Species Forecasting System; Method for Cleanly and Precisely Breaking Off a Rock Core Using a Radial Compressive Force; Praying Mantis Bending Core Breakoff and Retention Mechanism; Scoring Dawg Core Breakoff and Retention Mechanism; Rolling-Tooth Core Breakoff and Retention Mechanism; Vibration Isolation and Stabilization System for Spacecraft Exercise Treadmill Devices; Microgravity-Enhanced Stem Cell Selection; Diagnosis and Treatment of Neurological Disorders by Millimeter-Wave Stimulation; Passive Vaporizing Heat Sink; Remote Sensing and Quantization of Analog Sensors; Phase Retrieval for Radio Telescope and Antenna Control; Helium-Cooled Black Shroud for Subscale Cryogenic Testing; Receive Mode Analysis and Design of Microstrip Reflectarrays; and Chance-Constrained Guidance With Non-Convex Constraints.

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Evaluation of the Edge Crack Torsion (ECT) Test for Mode 3 Interlaminar Fracture Toughness of Laminated Composites

An analytical and experimental investigation was carried out on G40-800/R6376 graphite epoxy laminates to evaluate the Edge Crack Torsion (ECT) test as a candidate for a standard Mode 3 interlaminar fracture toughness test for laminated composites. The ECT test consists of a (90/(+/- 45)(sub 3)/(+/- 45)(sub 3)/90))(sub s) laminate with a delamination introduced by a non-adhesive film at the mid-plane along one edge and loaded in a special fixture to create torsion along the length of the laminate. Dye penetrate enhanced X-radiograph of failed specimens revealed that the delamination initiated at the middle of the specimen length and propagated in a self similar manner along the laminate mid-plane. A three-dimensional finite element analysis was performed that indicated that a pure Mode 3 delamination exists at the middle of specimen length away from both ends. At the ends near the loading point a small Mode 2 component exists. However, the magnitude of this Mode 2 strain energy release rate at the loading point is small compared to the magnitude of Mode 3 component in the mid-section of the specimen. Hence, the ECT test yielded the desired Mode 3 delamination. The Mode 3 fracture toughness was obtained from a compliance calibration method and was in good agreement with the finite element results. Mode 2 End-Notched Flexure (ENF) tests and Mode 1 Double Cantilever Beam (DCB) tests were also performed for the same composite material. The Mode 1 fracture toughness was much smaller than both the Mode 2 and Mode 3 fracture toughness. The Mode 2 fracture toughness was found to be 75% of the Mode 3 fracture toughness.

Li, Jian↗

Wind-simulation tester for solar modules

Tester induces cyclic pressure loads across module surface, guaranteeing its mechanical integrity. Module to be tested is sandwiched between stiffened aluminum layers covered with rubber sheets. Automatic front and back pressure loading is cycled by pneumatic system on separate stand. Relief valves prevent overpressuring. Fixture operates at high speed, completing cycle in 5 seconds, and typically applies 2,400 pascals.

Griffith, J. S.↗

Measurement of transmission loss characteristics using acoustic intensity techniques at the KU-FRL Acoustic Test Facility

The transmission loss characteristics of panels using the acoustic intensity technique is presented. The theoretical formulation, installation of hardware, modifications to the test facility, and development of computer programs and test procedures are described. A listing of all the programs is also provided. The initial test results indicate that the acoustic intensity technique is easily adapted to measure transmission loss characteristics of panels. Use of this method will give average transmission loss values. The fixtures developed to position the microphones along the grid points are very useful in plotting the intensity maps of vibrating panels.

Roskam, J.↗

Wind-Tunnel and Flight Test Results for the Measurements of Flow Variables at Supersonic Speeds Using Improved Wedge and Conical Probes

The results of supersonic wind-tunnel tests on three probes at nominal Mach numbers of 1.6, 1.8 and 2.0 and flight tests on two of these probes up to a Mach number of 1.9 are described. One probe is an 8 deg. half-angle wedge with two total-pressure measurements and one static. The second, a conical probe, is a cylinder that has a 15 deg., semi-angle cone tip with one total-pressure orifice at the apex and four static-pressure orifices on the surface of the cone, 90 deg. apart, and about two-thirds of the distance from the cone apex to the base of the cone. The third is a 2 deg. semi-angle cone that has two static ports located 180 deg. apart about 1.5 inches behind the apex of the cone. The latter probe was included since it has been the "probe of choice" for wind-tunnel flow-field pressure measurements (or one similar to it) for the past half-century. The wedge and 15 deg. conical probes used in these tests were designed for flight diagnostic measurements for flight Mach numbers down to 1.35 and 1.15 respectively, and have improved capabilities over earlier probes of similar shape. The 15. conical probe also has a temperature sensor that is located inside the cylindrical part of the probe that is exposed to free-stream flow through an annulus at the apex of the cone. It enables the determination of free-stream temperature, density, speed of sound, and velocity, in addition to free-stream pressure, Mach number, angle of attack and angle of sideslip. With the time-varying velocity, acceleration can be calculated. Wind-tunnel tests of the two probes were made in NASA Langley Research Center fs Unitary Plan Wind Tunnel (UPWT) at Mach numbers of 1.6, 1.8, and 2.0. Flight tests were carried out at the NASA Dryden Flight Research Center (DFRC) on its F-15B aircraft up to Mach numbers of 1.9. The probes were attached to a fixture, referred to as the Centerline Instrumented Pylon (CLIP), under the fuselage of the aircraft. Problems controlling the velocity of the flow through the conical probe required for accurate temperature measurements are noted, as well as some calibration problems of the miniature pressure sensors that required a re-calculation of the flow variables. Data are presented for angle of attack, pressure and Mach number obtained in the wind tunnel and in flight. In the wind tunnel some transient data were obtained by translating the probes through the shock flow field created by a bump on the wind-tunnel wall.

Bobbitt, Percy J.↗

A Lifetime of Shine

Moen Incorporated identified a market need for more durable polished brass plumbing fixtures. NASA's Glenn Research Center is a leader in surface coating technology, which enhances the physical properties of a wide range of materials. The collaborative efforts of Glenn and Moen resulted in a new polished brass finish called LifeShine(R). Based on testing results generated at NASA Glenn, Moen was able to manufacture an affordable, polished brass finish that is as durable as chrome, and resists deterioration. LifeShine is guaranteed to resist normal wear and tear and is even scratch-resistant to cleaning products as abrasive as steel wool. Moen was able to incorporate other colors into the LifeShine finish technology including classic gold, nickel, Satine(TM), Black Opal(TM), stainless, and copper. The company added titanium to LifeShine, making the finish even stronger and increasing its already superior durability. Highly resistant to salt and humidity, the LifeShine finish will remain intact even when the fixture is dented.

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