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Data from the particle impact tests are presented. Results are provided for the frictional heating tests of pairs of like materials. The materials tested include: Hastelloy X, Inconel 600, Invar 36, Monel K-500, Monel 400, nickel 200, silicon carbide, stainless steel 316, and zironium copper.
Methods currently under development to design ceramic turbine components with improved impact resistance are presented. Two different modes of impact damage are identified and characterized, i.e., structural damage and local damage. The entire computation is incorporated into the EPIC computer code. Model capability is demonstrated by simulating instrumented plate impact and particle impact tests.
The presentation provides background information pertinent to the MPS GH2 Flow Control Valve Poppet failure which occurred on the Space Shuttle Endeavour during STS-126 flight. The presentation provides general MPS system operating information which is pertinent to understanding the failure causes and affects. The presentation provides additional background information on the operating environment in which the FCV functions and basic design history of the flow control valve. The presentation provides an overview of the possible flight failure modes and a brief summary of the flight rationale which was developed for this failure event. This presentation is an introductory presentation to 3 other speakers at the conference who will be speaking on M&P aspects of the investigation, non destructive inspection techniques development, and particle impact testing.
No abstract available
Various hybrid processing steps, handling procedures, and materials are examined in an attempt to identify sources of contamination and to propose methods for the control of these contaminants. It is found that package sealing, assembly, and rework are especially susceptible to contamination. Moisture and loose particles are identified as the worst contaminants. The points at which contaminants are most likely to enter the hybrid package are also identified, and both general and specific methods for their detection and control are developed. In general, the most effective controls for contaminants are: clean working areas, visual inspection at each step of the process, and effective cleaning at critical process steps. Specific methods suggested include the detection of loose particles by a precap visual inspection, by preseal and post-seal electrical testing, and by a particle impact noise test. Moisture is best controlled by sealing all packages in a clean, dry, inert atmosphere after a thorough bake-out of all parts.
The conventional understanding of particle impact ignition characteristic elements relies on the following principles: 1) flammable particulate (except in the case of titanium and aluminum target materials); 2) gas velocity greater than 100 ft/s; 3) Impact point ranging from 45° to perpendicular to the path of the particle [1]; 4) flammable target material. To test assumptions about particulate flammability being necessary for particle impact ignition of less reactive target materials, such as Inconel 718, testing was performed with inert particulate. Supersonic particle impact testing was conducted with heated gas and 1500-µm sapphire particulate on various target materials: 304 stainless steel, wrought and selective laser melted Inconel 718, and Monel 400. Posttest characterization of impact craters was performed on each type of metallic target sample, including surface characterization performed by light optical microscopy and scanning electron microscopy with energy dispersive spectroscopy. Full consumption of the stainless steel and wrought Inconel 718 targets were noted to occur with sequential impacts. The results of testing will be discussed in detail, as well as recommendations for updating the understanding of the particle impact ignition mechanism.
Technique applies water-soluble ultrasonic couplant to transducer to facilitate acoustical nondestructive test for sealed and semisealed devices.
Particle impact ignition has been the primary cause of numerous fires in oxygen systems. This ignition phenomenon is known to occur where particles are present in high-velocity gas, and where impact occurs on a flammable material. The particle impact ignition behavior of many metals has been widely studied, but the particle impact ignition behavior of polymeric materials is relatively unknown. Particle impact ignition in polymeric materials is a concern as these materials are commonly used in component seat and seal applications, where high-velocity particle impacts can occur. This study evaluates several polymeric materials and compares the minimum temperature required for ignition (threshold temperature) of these materials: Kel-F 81 (CTFE), Teflon (PTFE), PEEK, Vespel SP-21, and Nylon 6/6. The materials were configured as targets in the White Sands Test Facility high-velocity particle impact test system. Gaseous oxygen was flowed at 4000 psi and sonic velocity, and the targets were impacted with 2000-micron aluminum 2017 particles. This paper discusses the results of these tests and ranks the materials according to their threshold temperatures at these conditions.
Ground-based hypervelocity imapct testing was conducted on IM7/977-3 quasi-isotropic flat panels at normal incidence using micron-sized particles (i.e. less than or equal to 100 microns) of soda lime glass and olivine. Testing was performed at room temperature (RT) and 175 C with results from the 175 C test compared to those obtained at RT. Between 10 and 30 particles with velocities ranging from 5 to 13 km/s impacted each panel surface for each test temperature. Panels were ultrasonically scanned prior to and after impact testing to assess internal damage. Post-impact analysis included microscopic examination of the surface, determination of particle speed and location, and photomicroscopy for microcrack assessment. Internal damage was observed by ultrasonic inspection on panels impacted at 175 C, whereas damage for the RT impacted panels was confined to surface divets/craters as determined by microscopic analysis.
Determining the total amount of water contained in an icing cloud necessitates the measurement of both the liquid droplets and ice particles. One commonly accepted method for measuring cloud water content utilizes a hot wire sensing element, which is maintained at a constant temperature. In this approach, the cloud water content is equated with the power required to keep the sense element at a constant temperature. This method inherently assumes that impinging cloud particles remain on the sensing element surface long enough to be evaporated. In the case of ice particles, this assumption requires that the particles do not bounce off the surface after impact. Recent tests aimed at characterizing ice particle impact on a thermally heated wing section, have raised questions about the validity of this assumption. Ice particles were observed to bounce off the heated wing section a very high percentage of the time. This result could have implications for Total Water Content sensors which are designed to capture ice particles, and thus do not account for bouncing or breakup of ice particles. Based on these results, a test was conducted to investigate ice particle impact on the sensing elements of the following hot-wire cloud water content probes: (1) Nevzorov Total Water Content (TWC)/Liquid Water Content (LWC) probe, (2) Science Engineering Associates TWC probe, and (3) Particle Measuring Systems King probe. Close-up video imaging was used to study ice particle impact on the sensing element of each probe. The measured water content from each probe was also determined for each cloud condition. This paper will present results from this investigation and attempt to evaluate the significance of ice particle impact on hot-wire cloud water content measurements.
This paper presents the results of a study of the penetration resistance of Type I Multi-Layer Insulation (MLI) to meteoroid and orbital debris particles. Hypervelocity impact tests on MLI were performed and the collected data was compared to data and empirical equations developed for aluminum. The study results indicate that MLI can be an effective shield from meteoroids and orbital debris for short duration missions and for non-critical elements. However, long missions which require high levels of protection cannot rely on MLI without a thorough investigation of the overall system reliability.
Parts produced by additive manufacturing, particularly selective laser melting (SLM), have been shown to silt metal particulate even after undergoing stringent precision aerospace cleaning processes (Lowrey 2016). As printed parts are used in oxygen systems with increased pressures, temperatures, and gas velocity, the risk of ignition by particle impact, the most common direct ignition source of metals in oxygen, substantially increases. The White Sands Test Facility (WSTF), in collaboration with Marshall Space Flight Center (MSFC), desires to test the ignitability of SLM metals by particle impact in heated oxygen. The existing test systems rely on gas velocity calculations to infer particle velocity in both subsonic and supersonic particle impact systems. Until now, it was not possible to directly measure particle velocity. To increase the fidelity of planned SLM ignition studies, it is necessary to validate that the Photon Doppler Velocimetry(PDV) test system can accurately measure particle velocity.
This report summarizes the damage analyses performed on the tether cable used for the tethered satellite system (TSS), for the damage that could be caused by meteoroid or orbital debris impacts. The TSS consists of a tethered satellite deployer and a tethered satellite. The analytical studies were performed at Marshall Space Flight Center (MSFC) with the results from the following tests: (1) hypervelocity impact tests to determine the 'critical' meteoroid particle diameter, i.e., the maximum size of a meteoroid particle which can impact the tether cable without causing 'failure'; (2) electrical resistance tests on the damaged and undamaged tether cable to determine if degradation of current flow occurred through the damaged tether cables; and (3) tensile load tests to verify the load carrying capability of the damaged tether cables. Finally, the HULL hydrodynamic computer code was used to simulate the hypervelocity impact of the tether cable by particles at velocities higher than can be tested, to determine the extent of the expected tether damage.
The Space Shuttle system is currently one of the National Aeronautics and Space Administration's (NASA) most important and complex programs. A significant number of hybrid microcircuits are being developed and used on the Space Shuttle. Since the Shuttle is a manned vehicle, reliability of the hybrids is flight critical. Loose particle contamination is one of the major causes of failure and reduced operating life for microcircuits. Process controls, surface coatings, and the particle impact noise detection (PIND) test were assessed for control of particle contamination, and the decision was made by NASA to require PIND test for all hybrid circuits. Selected hybrids from the production line of one vendor that had failed the PIND test were analyzed. Results of this program are presented.
The development of polymer composite liquid oxygen LO2 tanks is a critical step in creating the next generation of launch vehicles. Future launch vehicles need to minimize the gross liftoff weight (GLOW), which is possible due to the 25%-40% reduction in weight that composite materials could provide over current aluminum technology. Although a composite LO2 tank makes these weight savings feasible, composite materials have not historically been viewed as "LO2 compatible." To be considered LO2 compatible, materials must be selected that will resist any type of detrimental, combustible reaction when exposed to usage environments. This is traditionally evaluated using a standard set of tests. However, materials that do not pass the standard tests can be shown to be safe for a particular application. This paper documents the approach and results of a joint NASA/Lockheed Martin program to select and verify LO2 compatible composite materials for liquid oxygen fuel tanks. The test approach developed included tests such as mechanical impact, particle impact, puncture, electrostatic discharge, friction, and pyrotechnic shock. These tests showed that composite liquid oxygen tanks are indeed feasible for future launch vehicles.
Recent study on Particle-Impact Noise-Detection (PIND) shows impact at 1,500 to 4,000 G normally imparted to hybrid microcircuits during testing knocks loose stray trapped particle that can be subsequentially removed. Process may be 80 to 90 percent effective in removal of particles depending on type of test utilized.
The principal mechanism for developing orbital debris environment models, is to make observations of larger pieces of debris in the range of several centimeters and greater using radar and optical techniques. For particles that are smaller than this threshold, breakup and migration models of particles to returned surfaces in lower orbit are relied upon to quantify the flux. This reliance on models to derive spatial densities of particles that are of critical importance to spacecraft make the unique nature of the EFT-1's return surface a valuable metric. To this end detailed post-flight inspections have been performed of the returned EFT-1 backshell, and the inspections identified six candidate impact sites that were not present during the pre-flight inspections. This paper describes the post-flight analysis efforts to characterize the EFT-1 mission craters. This effort included ground based testing to understand small particle impact craters in the thermal protection material, the pre- and post-flight inspection, the crater analysis using optical, X-ray computed tomography (CT) and scanning electron microscope (SEM) techniques, and numerical simulations.
The ignition of carbon steel and 316 and 304 stainless steels caused by the impact of low-velocity particles (a standard mixture consisting of 2 g of iron and 3 g of inert materials) in gaseous oxygen was investigated using NASA/White Sands Test Facility for the ignition test, and a subsonic particle impact chamber to accelerate the particles that were injected into flowing oxygen upstream of the target specimen. It was found that the oxygen velocities required to ignite the three alloys were the same as that required to ignite the particle mixture. Ignition occurred at oxygen velocities greater than 45 m/sec at 20 to 24 MPa and was found to be independent of pressure between 2 and 30 MPa. Comparison of the present results and the past results from Wegener (1964) with the Compressed Gas Association (CGA) oxygen velocity limits for safe operations indicates that the CGA limits may be excessively conservative at high pressures and too liberal at low pressures.