Surface Measurement of a Large Inflatable Reflector in Cryogenic Vacuum

The metrology of membrane structures, especially inflatable, curved, optical surfaces, remains challenging. Internal pressure, mechanical membrane properties, and circumferential boundary conditions imbue highly dynamic slopes to the final optic surface. Here, we present our method and experimental results for measuring a 1 m inflatable reflector’s shape response to dynamic perturbations in a thermal vacuum chamber. Our method uses phase-measuring deflectometry to track shape change in response to pressure change, thermal gradient, and controlled puncture. We use an initial measurement as a virtual null reference, allowing us to compare 500 mm of measurable aperture of the concave f/2, 1-meter diameter inflatable optic. We built a custom deflectometer that attaches to the TVAC window to make full use of its clear aperture, with kinematic references behind the test article for calibration. Our method produces 500 × 500 pixel resolution 3D surface maps with a repeatability of 150 nm RMS within a cryogenic vacuum environment (T = 140 K, P = 0.11 Pa).

Modernization of NASA Johnson Space Center’s Chamber A to support Cryogenic Vacuum Optical Testing of the James Webb Space Telescope (JWST)

NASA is the mission lead for the James Webb Space Telescope (JWST), the next of the “Great Observatories,” scheduled for launch in 2021. NASA is directly responsible for the integration and test (I&T) program that culminated in an end-to-end cryo vacuum optical test of the flight telescope and instrument module in Chamber A at NASA Johnson Space Center. Historic Chamber A is the largest thermal vacuum chamber at Johnson Space Center and one of the largest space simulation chambers in the world. Chamber A has undergone a major modernization effort to support the deep cryogenic, vacuum and cleanliness requirements for testing the JWST. This paper describes the upgrades to the Chamber A facility: Thermal Shrouds, Helium Refrigeration, Liquid Nitrogen System, High Vacuum System, Clean Airflow System, and Utilities.

A simple glasshouse experiment to test the isotopic fractionation in olive trees

<p>Plant transpiration is a main component of the global water cycle and plays a key role in regulating ecohydrological process. Stable isotopes of oxygen and hydrogen are often used for the identification and quantification of plant water sources in ecohydrology. However, the isotopic tracing technique assumes that the isotopic signal in the water taken up by the plants remains unaltered during uptake at the soil-roots interface and transport to the distal twigs, i.e., isotopic fractionation does not occur during the water uptake and along the transport pathway. Nevertheless, recent studies showed that isotopic fractionation can occur under different environmental conditions. In this study, we performed a simple experiment with two olive (<em>Olea europaea</em>) trees utilizing labelled water to test isotopic fractionation of plant water during uptake and transport within the plants under controlled conditions. In addition, we performed the cryogenic vacuum distillation in two different laboratories to examine any possible effects of the extraction system on the isotopic composition of plant water extracts.</p><p>We set up the olive trees in pots inside a glasshouse and measured sap flow rates with Granier thermal dissipation probe, and shallow soil moisture by using a portable soil moisture probe. Air temperature, global solar radiation, and relative humidity were measured by a weather station installed inside the glasshouse nearby the olive trees. We irrigated the two plants with water of known isotopic composition and sampled the twigs, wood cores, roots, and soils at different depths (0-5, 5-15, and 15-25 cm). We extracted plant and soil waters by means of cryogenic vacuum distillation performed in two different laboratories.</p><p>Our results showed that the plant water samples reflected the isotopic signature of labelled water and mobile soil water, suggesting no isotopic fractionation during water transport. No significant differences were detected for twigs and wood cores extracted from distinct sections of the tree. However, only significant differences were obtained between plant tissue water (twigs, cores) and cryogenically-extracted deep soil water (i.e., >15 cm depths). Furthermore, we found no significant effects of the two cryogenic extraction systems on the isotopic composition of water extracts. Our results indicate that isotopic fractionation might not occur during root water uptake and transport processes in olive trees, at least under the specified experimental conditions, validating the conventional isotope-tracing approach. Further work both in the field and under controlled conditions, and on different plant species, is needed to check for this consistency, as well as testing other plant water extraction methods.</p><p> </p><p>Keywords: olive tree; stable isotope analysis; plant water; cryogenic vacuum distillation; fractionation; labelled water.</p>

Potential effects of cryogenic extraction biases on inferences drawn from xylem water deuterium isotope ratios: case studies using stable isotopes to infer plant water sources

Recent studies have demonstrated that plant and soilwater extraction techniques can introduce biases and uncertainties in stable isotope analyses. Here we show how recently documented δ2H biases resulting from cryogenic vacuum distillation of water from xylem tissues may have influenced the conclusions of five previous studies, including ours, that have used δ2H to infer plant water sources. Cryogenic extraction biases that reduce xylem water δ2H will also introduce an artifactual evaporation signal in dual-isotope (δ2H vs. δ18O) analyses. Calculations that estimate the composition of the source precipitation of xylem waters by compensating for their apparent evaporation will amplify the bias in δ2H, and also introduce new biases in the δ18O of the inferred pre-evaporation source precipitation. Cryogenic extraction biases may substantially alter plant water source attributions if the spread in δ2H among the potential end members is relatively narrow. By contrast, if the spread in δ2H among the potential end members is relatively wide, the impact of cryogenic extraction biases will be less pronounced, and thus suggestions that these biases universally invalidate inferences drawn from plant water δ2H are unwarranted. Nonetheless, until reliable correction factors for cryogenic extraction biases become available, their potential impact should be considered in studies using xylem water isotopes.

Analytical and Numerical Model of Aluminum Alloy Swaging Ring Design to Study the Effect on the Sealing for Piping Systems

In various fields of engineering, the assembly and repair of hydraulic installations are accomplished by joining the pipes. In such applications, the ring swaging method is used to connect the fittings to the pipes by means of a hydraulic hand tool. The basis to develop a swaging tool relies on the knowledge of the design parameter that influence plastic deformation of the swaging ring. In addition to build control over the design parameters, it is necessary to join pipes under severe conditions such as cryogenic vacuum and constrained space which require an intact sealing. In this study, the effect of swaging ring designs on sealing and strength has been examined and different swaging methods have been investigated by finite element modeling methods. Based on the obtained results, the analysis methodology of ring swaging and the characteristic impact of swaging ring design on the sealing of pipe connection are shown. The prime novelty of the study is to report the impact of swaging ring design and geometry on sealing efficiency of the pipe connection. The results of the study open new avenues for the development of efficient tools for designing swaging rings. Doi: 10.28991/cej-2021-03091641 Full Text: PDF