Pre-stressed thermal protection systems

A hexagonal protective and high temperature resistant system for the Space Shuttle Orbiter consists of a multiplicity of pockets formed by hexagonally oriented spacer bars secured on the vehicle substructure. A packing of low density insulating batt material 18 in each pocket, and a thin protective panel of laterally resilient advanced carbon-carbon material surmounting the peripherals bars and packing. Each panel has three stepped or offset lips on contiguous edges. At the center of each pocket is a fully insulated stanchion secured to and connecting the substructure and panel for flexing the panel toward the substructure and thereby prestressing the panel and forcing the panel edges firmly against the spacer bars

Ellipsoidal-mirror reflectometer accurately measures infrared reflectance of materials

Reflectometer accurately measures the reflectance of specimens in the infrared beyond 2.5 microns and under geometric conditions approximating normal irradiation and hemispherical viewing. It includes an ellipsoidal mirror, a specially coated averaging sphere associated with a detector for minimizing spatial and angular sensitivity, and an incident flux chopper

Studies of atmospheric refraction effects on laser data

The refraction effect from three perspectives was considered. An analysis of the axioms on which the accepted correction algorithms were based was the first priority. The integrity of the meteorological measurements on which the correction model is based was also considered and a large quantity of laser observations was processed in an effort to detect any serious anomalies in them. The effect of refraction errors on geodetic parameters estimated from laser data using the most recent analysis procedures was the focus of the third element of study. The results concentrate on refraction errors which were found to be critical in the eventual use of the data for measurements of crustal dynamics

Analysis of defect structure in silicon. Characterization of SEMIX material. Silicon sheet growth development for the large area silicon sheet task of the low-cost solar array project

Statistically significant quantitative structural imperfection measurements were made on samples from ubiquitous crystalline process (UCP) Ingot 5848 - 13C. Important correlation was obtained between defect densities, cell efficiency, and diffusion length. Grain boundary substructure displayed a strong influence on the conversion efficiency of solar cells from Semix material. Quantitative microscopy measurements gave statistically significant information compared to other microanalytical techniques. A surface preparation technique to obtain proper contrast of structural defects suitable for quantimet quantitative image analyzer (QTM) analysis was perfected and is used routinely. The relationships between hole mobility and grain boundary density was determined. Mobility was measured using the van der Pauw technique, and grain boundary density was measured using quantitative microscopy technique. Mobility was found to decrease with increasing grain boundary density

Automated Data Management Information System (ADMIS)

ADMIS stores and controls data and documents associated with manned space flight effort. System contains all data oriented toward a specific document; it is primary source of reports generated by the system. Each group of records is composed of one document record, one distribution record for each recipient of the document, and one summary record

Spin Torque Dynamics with Noise in Magnetic Nano-System

We investigate the role of equilibrium and nonequilibrium noise in the magnetization dynamics on mono-domain ferromagnets. Starting from a microscopic model we present a detailed derivation of the spin shot noise correlator. We investigate the ramifications of the nonequilibrium noise on the spin torque dynamics, both in the steady state precessional regime and the spin switching regime. In the latter case we apply a generalized Fokker-Planck approach to spin switching, which models the switching by an Arrhenius law with an effective elevated temperature. We calculate the renormalization of the effective temperature due to spin shot noise and show that the nonequilibrium noise leads to the creation of cold and hot spot with respect to the noise intensity.Comment: 10 pages, 7 figure

Vacuum-UV negative photoion spectroscopy of CF3Cl, CF3Br and CF3I

Using synchrotron radiation negative ions have been detected by mass spectrometry following vacuum-UV photoexcitation of trifluorochloromethane (CF$_3$Cl), trifluorobromomethane (CF$_3$Br) and trifluoroiodomethane (CF$_3$I). The anions F$^-$, X$^-$, F$_2^-$, FX$^-$, CF$^-$, CF$_2^-$ and CF$_3^-$ were observed from all three molecules, where X = Cl, Br or I, and their ion yields recorded in the range 8-35 eV. With the exception of Br$^-$ and I$^-$, the anions observed show a linear dependence of signal with pressure, showing that they arise from unimolecular ion-pair dissociation. Dissociative electron attachment, following photoionization of CF$_3$Br and CF$_3$I as the source of low-energy electrons, is shown to dominate the observed Br$^-$ and I$^-$ signals, respectively. Cross sections for ion-pair formation are put on to an absolute scale by calibrating the signal strengths with those of F$^-$ from both SF$_6$ and CF$_4$. These anion cross sections are normalized to vacuum-UV absorption cross sections, where available, and the resulting quantum yields are reported. Anion appearance energies are used to calculate upper limits to 298 K bond dissociation energies for $D^0$(CF$_3$-X) which are consistent with literature values. We report new data for $D^0$(CF$_2$I$^-$-F) ≤ 2.7 ± 0.2 eV and $\Delta_fH^0_{298}$ (CF$_2$I$^+$) ≤ (598 ± 22) kJ mol$^{-1}$. No ion-pair formation is observed below the ionization energy of the parent molecule for CF$_3$Cl and CF$_3$Br, and only weak signals (in both I$^-$ and F$^-$) are detected for CF$_3$I. These observations suggest neutral photodissociation is the dominant exit channel to Rydberg state photoexcitation at these lower energies