Pulsations of the R Coronae Borealis stars

The radial pulsations of very luminous, low-mass models (L/M 10⁴, solar units), which are possible representatives of the R CrB stars, have been examined. These pulsations are extremely nonadiabatic. We find that there are in some cases at least one extra (strange) mode which makes interpretation difficult. The blue instability edges are also peculiar, in that there is an abrupt excursion of the blue edge to the blue for L/M sufficiently large. The range of periods of the model encompasses observed periods of the Cepheid-like pulsations of actual R CrB stars.     

The 2.5 to 5 microns spectrum of comet Halley from the IKS instrument of Vega

Results of the 2.5–5 micron spectroscopic channel of the IKS instrument on Vega are reported and the data reduction process is described. H₂O and CO₂ molecules have been detected with production rates of 10³⁰ s⁻¹ and 1.5 10²⁸ s⁻¹ respectively. Emission features between 3.3 and 3.7 microns are tentatively attributed to CH - bearing compounds - CO is marginally detected with a mixing ratio CO/H₂O 0.2. OH emission and H₂O - ice absorption might also be present in the spectra.     

Computer modelling of a penetrator thermal sensor

The Philae lander is part of the Rosetta mission to investigate comet 67P/Churyumov-Gerasimenko. It will use a harpoon like device to anchor itself onto the surface. The anchor will perhaps reach depths of 1–2 m. In the anchor is a temperature sensor that will measure the boundary temperature as part of the MUPUS experiment. As the anchor attains thermal equilibrium with the comet ice it may be possible to extract the thermal properties of the surrounding ice, such as the thermal diffusivity, by using the temperature sensor data. The anchor is not an optimal shape for a thermal probe and application of analytical solutions to the heat equation is inappropriate. We prepare a numerical model to fit temperature sensor data and extract the thermal diffusivity. Penetrator probes mechanically compact the material immediately surrounding them as they enter the target. If the thermal properties, composition and dimensions of the penetrator are known, then the thermal properties of this pristine material may be recovered although this will be a challenging measurement. We report on investigations, using a numerical thermal model, to simulate a variety of scenarios that the anchor may encounter and how they will affect the measurement.     

Analysis of nonstationary heating and cooling of a thermomagnetic engine gadolinium working element

The paper presents the results of calculating nonstatitionary heat exchange between a heattransfer agent (water) and a gadolinium working element of the thermomagnetic engine with the use of ANSYS 13.0 certified software. Recommendations for designing the thermomagnetic engine working elements are given based on the analysis of calculation results.     

EUVITA — An extreme UV imaging telescope array with spectral capability

EUVITA is a set of 8 extreme UV normal incidence imaging telescopes, each of them sensitive in a narrow band (λ/Δλ = 15 to 80), centered at wavelengths between 50 and 175 Å. Each telescope has an effective area of a few cm²; a field of view of 1.2° and a spatial resolution of 10 arcsec.

EUVITA will be flown on the Russian mission SPECTRUM X-G. This satellite will be launched in a highly eccentric orbit with a period of 4 days, allowing long, uninterrupted observations (e.g. 10⁵ seconds). EUVITA's narrow spectral bands allow the measurement of source parameters such as temperature or power law index as well as interstellar absorption, and will resolve groups of strong lines emitted by optically thin hot plasmas.     

Force sensitivity of plant gravisensing.

Rotation at 4, 10, 50 and 100 rpm on a horizontal clinostat and in microgravity exerts limited effects on the morphogenesis of lettuce and cress root statocytes and statoliths if compared with the vertical control or 1 g spaceflight reference centrifuge. However, the average distance of statoliths from the distal wall increases. The pattern of plastid location of microgravity-grown and that of clino-rotated samples has been determined at 10, 50, and 100 rpm. Experiments on the centrifuge-clinostat and spaceflight centrifuge (acceleration forces of 0.005 to 1 g) revealed that the average statolith location depends on the amplitude of acropetally or basipetally directed mass acceleration. Decreasing the acropetally directed force from 1 g to 0.4 g dislocates statoliths towards the cell center possibly mediated by the elastic forces of the cytoskeleton. In statocytes formed on the clinostat or in microgravity, the majority of statoliths are located at the center of the cell. To force the statoliths from the center of the statocyte towards one of its poles, a threshold mass acceleration of 0.01 g is required. Statocytes with centrally-located statoliths are considerably more effective in transducing a gravistimulus than those with distally-located plastids. The latent time of the graviresponse is shorter and the response itself is enhanced in roots grown on the clinostat compared to vertically grown samples. The early phases of graviperception are independent of root growth conditions since presentation time and g-threshold are similar for roots grown stationary and those on a clinostat. We propose a sequence of events in gravitropic stimulation that considers not only the lateral displacement of statoliths, as predicted by the starch-statolith hypothesis, but also its longitudinal motion, together with differential gravisensitivity of mechanotransducing structures along the lower-most longitudinal cell wall.     

Microgravity and the organisms: results of the Spacelab mission D1.

During the Spacelab mission D1 different organisms were investigated at the unicellular and multicellular level respectively. Microgravity affects growth and development of the organisms in a different manner, some processes are enhanced, others are inhibited. On the other hand, there are a lot of parameters. e.g. circadian rhythm or cell and organ polarity, which seem to be exclusively under genetical control.     

Accessing NASA technology with the World Wide Web

NASA Langley Research Center (LaRC) began using the World Wide Web (WWW) in the summer of 1993, becoming the first NASA installation to provide a center-wide home page. This coincided with a reorganization of LaRC to provide a more concentrated focus on technology transfer to both aerospace and non-aerospace industry. Use of WWW and NCSA Mosaic not only provides automated information dissemination, but also allows for the implementation, evolution and integration of many technology transfer and technology awareness applications. This paper describes several of these innovative applications, including the on-line presentation of the entire Technology Opportunities Showcase (TOPS), an industrial partnering showcase that exists on the Web long after the actual 3-day event ended. The NASA Technical Report Server (NTRS) provides uniform access to many logically similar, yet physically distributed NASA report servers. WWW is also the foundation of the Langley Software Server (LSS), an experimental software distribution system which will distribute LaRC-developed software. In addition to the more formal technology distribution projects, WWW has been successful in connecting people with technologies and people with other people     

Corrections of Satellite Positions in Near-Real Time

The influence of sudden increases of electron content on the accurate determination of the position of a satellite is investigated based on a spherically stratified ionospheric model. Using the total electron content information from Faraday rotation measurements, a procedure is presented whereby the corrections of satellite position due to the unpredicted electron increase can be accounted for without the need to know the spatial distribution of the additional electrons.     

Autogeneration of an Instability of a Plasma Composition Equilibrium in the Plasmaspheric Transition Region during a Postsunset High-Altitude Launch of the Vertikal'-10 Rocket

A cause of the instability of equilibrium of plasma ion composition is discussed and exemplified by the data on a burst of amplitudes of small-scale plasma irregularities in the plasmaspheric transition region during an evening launch of the Vertikal'-10 rocket. This burst is accompanied by a simultaneous decrease in the average plasma density at altitudes of 700–1100 km. Specific features of the observed events are compared to postsunset incoherent scatter radar observations of the ion diffusion flux density. It is demonstrated that the instability is caused by peculiarities of the protonosphere–ionosphere interaction associated with a sharp difference between thermal conditions of the ionospheric and protonospheric air shortly after sunset. The induced nonuniformity of postsunset cooling of the protonospheric–ionospheric plasma causes density irregularities in ion diffusion fluxes and generates local bunches of heavy ions, which are usually only a minor impurity to lighter ions. As a result, conditions are created that are favorable for the nondissipative accumulation of potential energy for the mutual opposition of two or more groups of ions with different masses and for the subsequent release of this energy by a threshold excitation of impurity-driven plasma instabilities.