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NASA NTRS1989

The effect of impurity gasses on variable polarity plasma arc welded 2219 aluminum

Variable polarity plasma arc (VPPA) welding has been used with considerable success by NASA for the welds on the Space Shuttle External Tank as well as by others concerned with high quality welded structures. The effects of gaseous contaminants on the appearance of VPPA welds on 2219 aluminum are examined so that a welder can recognize that such contamination is present and take corrective measures. There are many possible sources of such contamination including, contaminated gas bottles, leaks in the gas plumbing, inadequate shield gas flow, condensed moisture in the gas lines or torch body, or excessive contaminants on the workpiece. The gasses chosen for study in the program were nitrogen, oxygen, methane, and hydrogen. Welds were made in a carefully controlled environment and comparisons were made between welds with various levels of these contaminants and welds made with research purity (99.9999 percent) gasses. Photographs of the weld front and backside as well as polished and etched cross sections are presented.

Mcclure, John C.↗

NASA NTRS1997

Ion Figuring of Replicated X-Ray Optics

This investigation included experiments to demonstrate ion beam figuring effects on electroless nickel with the expressed desire to figure X-ray optic mandrels. It was important to establish that ion beam figuring did not induce any adverse effects to the nickel surface. The ion beam has consistently been shown to be an excellent indicator of the quality of the subsurface. Polishing is not the only cause for failure in the ion beam final figuring process, the material composition is equally important. Only by careful consideration of both these factors can the ion beam final figuring process achieve its greatest potential. The secondary goal was to construct a model for representing the ion beam material removal rate. Representing the ion beam removal rate is only an approximation and has a number of limiting factors. The resolution of the metrology apparatus limits the modeling of the beam function as well. As the surface error corrections demand more precision in the final figuring, the model representing beam function must be equally precise. The precision to which the beam function can be represented is not only determined by the model but also by the measurements producing that model. The method developed for determining the beam function has broad application to any material destined to be ion beam figured.

Cantey, Thomas M.↗

NASA NTRS2006

Ultra-lightweight, Low Scatter, Large Mirror Technology

A technique is being developed to fabricate a prototype lightweight composite mirror one meter in diameter. The mandrel, on which the composite mirror will be laid up, is an ultra low expansion quartz glass, TSG, whose thermal expansion coefficient, 10(exp -7)/ degC or less, is similar to that for the composite material itself. The mandrel surface will be super-polished to 6-8 A rms or better, resulting in ten times less scattered light in the visible region than is found in typical astronomical mirrors. We have shown experimentally that mandrel micro-roughnesses of this order can be successfully replicated on composite faceplates. The faceplate is very tough, and does not fracture like a thin glass faceplate. It will be supported by actuators alone, not by the edge of the mirror mount, to avoid non-uniform or non-symmetric influence functions. BOR developed actuators are designed for atmospheric correction, maintenance of optical figure, and minor tip tilt. They have a throw of a centimeter, can be controlled remotely, and have a response time of 1/2 msec. The piezoelectric part of the actuator operates in the 30-70 V range and the differential screw portion has a linearity of about +/-0.1 microns.

Bennett, H. E.↗

NASA NTRS2023

Sewage Treatment Plant #1 Area, SWMU 117 Per- and Polyfluoroalkyl Substances (PFAS) Site Assessment Progress Report

This Per- and Polyfluoroalkyl Substances (PFAS) Site Assessment (SA) Progress Report (SAPR) discusses the investigation activities and findings for the Sewage Treatment Plant #1 (STP1) Area located at Kennedy Space Center (KSC), Florida (Figure 1-1). This site has been designated Solid Waste Management Unit (SWMU) 117 under KSC’s Resource Conservation and Recovery Act (RCRA) Corrective Action Program, as the sewage treatment plant and associated areas were identified as a potential source of PFAS to the environment. This PFAS SAPR was prepared by Tetra Tech, Inc., for the National Aeronautics and Space Administration (NASA) under Indefinite Delivery Indefinite Quantity Contract 80KSC019D0011-80KSC019F0070. This is the first progress report to document on-going SA activities; supplemental progress reports will be provided as additional data is collected. PFAS SA activities were conducted between April 2020 and March 2022 to collect additional data to supplement the existing datasets to better understand the extent of PFAS impacts to the environment in the STP1 Area. The SA for the STP1 Area covers an approximately 130-acre investigation area with multiple structures and buildings. The focus of the SA is the STP1 Complex and associated structures, including the former Polishing Pond, former Sludge Disposal8 Area, and former Spray Field. The STP1 Complex is located in the KSC Industrial Area, at the southwest corner of 4th Street SE and C Avenue SE. The STP1 Complex is located approximately ¼-mile south and downgradient of the Fire Station #1 site (SWMU 116), which is also currently undergoing a PFAS SA because of potential releases of PFAS-containing aqueous film-forming foam (AFFF). During the SA, a total of seven soil, 131 groundwater direct push technology (DPT), 24 groundwater monitoring well, and 11 surface water samples were collected between April 2020 and March 2022. Monitoring well samples were analyzed for 18 PFAS compounds, with all other samples analyzed for 28 PFAS compounds. The SA sample results were used along with historical results to evaluate the extent of PFAS impacts to the environment in the STP1 Area. Data generated to date and prior results were screened against the United States Environmental Protection Agency (USEPA) May 2022 Tap Water Regional Screening Levels (RSL) for groundwater and residential RSLs for soil (hazard quotient of 0.1). Surface water results were screened against the State of Florida Human Health Surface Water Screening Levels (SWSLs). Results from the SA showed exceedances of the applicable screening criteria for groundwater and surface water. Considering the current and historical dataset, PFOS is the prevalent PFAS compound. Based on these results, additional groundwater DPT and surface water sampling should be considered for PFAS analysis, focused on evaluating surface water bodies in the southeast portion of the Industrial Area, which discharge into the Banana River. Additionally, installation of monitoring wells should be considered to evaluate the interaction between the groundwater and surface water at the site. Collection of additional samples for TOC analysis should also be considered from representative groundwater (saturated soils) and surface water locations to further evaluate potential correlations between PFAS and TOC to provide a more comprehensive dataset to assist in fate and transport analyses.

Sewage Treatment Plant↗

NASA NTRSDate not supplied

Reflectance spectra measurement plan of captured samples from Ryugu: current status

Hayabusa2 spacecraft is equipped with Optical Navigation Camera (ONC) andNear-infrared Spectrometer (NIRS3), and has obtained reflectance spectra of the C-type near-Earth asteroid Ryugu over a wavelength range of 0.40–0.95 μm and 1.8–3.2 μm, respectively. It was revealed that Ryugu exhibits globally very low albedo (less than 0.02 at 0.55 and 2.0 μm), a slightly positive spectral slope, and an ubiquitous weak but sharp OH absorption band centered at 2.72 μm,showing a little regional heterogeneities. Thus, the surface material of Ryugu can be estimated as relatively similar to moderately heated carbonaceous chondrites, e.g., moderately dehydrated CI and CM, and enriched in carbon (Kitazato et al., 2019; Sugita et al., 2019; Tatsumi et al., 2020).Hayabusa2 successfully has performed twice touch down operations, and the captured sample will be brought back to the Earth in late 2020 (Morota et al., 2020; Tachibana et al., in preparation). To clarify Ryugu’s mineralogical and physicochemical properties and their varieties, effective for spectral characteristics obtained by ONC and NIRS3, several grains are planned to be distributed to several primary analysis groups. In this study, we report the current status of our spectral analysis plan in Hayabusa2 MINeralogy and PETrology of coarse grains (MIN-PET CG) team led by T. Nakamura, and the latest rehearsal analysis result using carbonaceous chondrite samples. MIN-PET CG rehearsal measurements have been performed to obtain detailed spectral properties of Ryugu grains with diverse spatial resolutions ranging from μm to mm scale or larger; using a few mm size polished CM sample with several microscopic imaging spectrometers covering various spatial range; with 200 μmor finer spatial resolution at Institut d’Astrophysique Spatiale, ~50 and 150 μm spatial resolution invisible and IR ranges at Brown University, and with 40 μm or larger spatial resolution at Tohoku University, and using mm-size CM and CI grains with a diffuse reflectance spectrometer with a few mm resolution at Tohoku University. Diffuse reflectance spectroscopy measurements undergo to use several mm-size CM or CI chondrite grains with Bruker VERTEX 70v, which covers ~0.38–15 μm in wavelength. To keep returned samples out of atmosphere avoiding any terrestrial contamination, wehave prepared an air shutoff cell to put samples and standard materials together kept in a N2 purged condition (Amano et al., 2020). Samples are Murchison CM chondrite showing typically ~5%reflectance with a strong OH absorption band at ~2.8 μm, and laboratory heated CI chondrite showing~3% reflectance, and a weak OH absorption band at ~2.7 μm. We will perform (1) fixed angle condition as laboratory standard setting at incident, emission, and phase angles of 30°, 0°, 30°, or 0°,30°, 30°, and (2) various angle conditions for photometric corrections. Future lab analyses of samples returned from Ryugu will provide direct and detailed information on the mineralogical and physicochemical properties of Ryugu, and relationship of spectral characteristics obtained by remote sensing and laboratory instruments.

M. Matsuoka↗

NASA NTRSDate not supplied

Meteorite Sample Section Repair at NASA Johnson Space Center

Introduction: Meteorite thin and thick sections are routinely shipped from NASA Johnson Space Center to fulfill sample allocation requests from principle investigators around the world. Sections are also re-turned to JSC when researchers are finished studying them since, in most cases, they can be reused for other studies. The sections are very fragile unfortunately, and sometimes return to us needing repairs. The fol-lowing should give you an idea of how we repair sections here in the very lab where they were created. NOTE: Please do not attempt to repair ANSMET meteorite sections that are in your possession. We will perform the repairs for you at NASA JSC if you send the section back to us. Section Delamination: The majority of the meteorite sections that we produce here are secured to the glass slide using a high quality, two-part epoxy. Occasionally, we are asked to use superglue if the researcher wishes to dismount the section from the slide. Both epoxy and superglue are excellent adhesives, but they both tend to embrittle with time which results in delamination from the slide. Exposure to vacuum can also degrade the adhesion between the sample section and the glass slide. Repeated handling of the slide edges can accelerate delamination and, as a preventive measure, the outer 1-2 mm of epoxy is trimmed from newly created sections at JSC. If conductive tapes (copper, carbon, etc.) are used on the section during analysis, great care must be taken in removing the tape so that the epoxy is not pulled up with it. If in doubt, the tape can be left on the section when it is returned to JSC. Before we perform any repairs to sample sections, carbon, gold, or other coatings are removed. We accomplish this using a slurry of 0.05 micron alumina and 190 proof ethyl alcohol applied to a felt polishing pad fitted to a rotating lap wheel. Coatings are re-moved in this manner from all sections that are re-turned to JSC. The extent of the delamination determines how we proceed with the section repair. If the meteorite sample area of the section is not disturbed, then we carefully remove the delaminated epoxy. This is done using a binocular microscope with a 6X zoom, cut-proof gloves, and a very sharp, single edged razor blade. We cut the delaminated epoxy with the blade angled away from the sample area and using very light pressure. The trimmed section is then cleaned in an ultrasonic bath of 200 proof ethyl alcohol for no more than 10 seconds and carefully dried using a lint-free clean room wipe. The section is then placed into a lab oven at 110o F in preparation for epoxy. We mix the resin and hardener components of the low viscosity epoxy and very small amounts are applied to the cut edges of the section using a needle probe and the binocular microscope. Warming the epoxy helps secure the existing section by filling any voids between the glass slide and the section. After the new epoxy cures, we give the section a light polish on a lap wheel fitted with cotton polishing paper that is charged with 1 micron diamond paste. If the section has delaminated to the point of sample area being lifted from the glass, then it may be irreparable. We employ the above technique along with clamping the section in a Teflon pad arrangement in order to flatten the sample while the epoxy cures. Otherwise, the sample will tend to curl. This works to some degree, but once the sample area curls, it seldom re-turns to the original flatness without cracking or bending. Canada Balsam and Crystalbond: We repair damaged sections that had originally been prepared using Canada Balsam or Crystalbond adhesives through the gradual application of heat. We take great care with these samples since these bonding materials tend to get brittle with age. The section is heated in gradual steps (40-50o F per hour) to the melting point of the adhesive. We repair the sample while the adhesive is fluid and then the section is cooled in the same gradual manner in which it was heated. Slide Cracks and Breaks: Accidents happen. Especially with something as small and fragile as a thin/thick section. We all know someone who has driven a microscope objective into a section. As bad as the damage may look, the section can be repaired in most instances. NOTE: Please do not try to tape or glue section pieces back together prior to returning the dam-aged section. This practice usually renders the section irreparable. If the glass slide is cracked but the section is still in one piece, we repair it by infilling the crack with the low viscosity epoxy mentioned earlier. If the slide is in pieces, we can reassemble it with epoxy on a new backer slide. This is a tricky task as the pieces need to be in the correct plane with respect to each other, especially if the sample area is split among several pieces.

Meteorite↗