Results of an analytical study of spacecraft deposition contamination by internal reflection spectroscopy

Outgassing, deposition, and desorption kinetics of silicone compounds, are examined as examples of optical surface contaminants of spacecraft windows. Their behavior in a space environment after exposure to ultraviolet radiation is also examined. The use of internal reflection spectroscopy is shown to provide a viable means of real-time, in-situ identification of contaminants of orbiting spacecraft. The instrumental techniques are proposed as the basis of further investigations and the development of flight hardware

Analytical study of spacecraft deposition contamination by internal reflection spectroscopy

The in-situ vacuum chamber designed around the IRE was tested under vacuum. The contamination analyzer system was tested using two liquid contaminant materials. The analysis of the contaminants on the SL-4 rendezvous window shows that the material has methyl silicone, hydroxyl, and carbonyl radicals. The analysis of the outgassing material from Shuttle TPS shows silicone as the primary product

Liquid phase sintered compacts in space

A model that will explain the effect of gravity on liquid phase sintering was developed. Wetting characteristics and density segregation which are the two important phenomena in liquid phase sintering are considered in the model development. Experiments were conducted on some selected material combinations to study the gravity effects on liquid phase sintering, and to verify the validity of the model. It is concluded that: (1) The surface tension forces acting on solid particles in a one-g environment are not appreciably different from those anticipated in a 0.00001g/g sub 0 (or lower) environment. (2) The capillary forces are dependent on the contact angle, the quantity of the liquid phase, and the distance between solid particles. (3) The pores (i.e., bubbles) do not appear to be driven to the surface by gravity-produced buoyancy forces. (4) The length of time to produce the same degree of settling in a low-gravity environment will be increased significantly. (5) A low gravity environment would appear to offer a unique means of satisfactorily infiltrating a larger and/or complex shaped compact

Handbook on passive thermal control coatings

A handbook of passive thermal control surfaces data pertaining to the heat transfer requirements of spacecraft is presented. Passive temperature control techniques and the selection of control surfaces are analyzed. The space environmental damage mechanisms in passive thermal control surfaces are examined. Data on the coatings for which technical information is available are presented in tabular form. Emphasis was placed on consulting only those references where the experimental simulation of the space environment appeared to be more appropriate

Analytical study of spacecraft deposition contamination by internal reflection spectroscopy

Infrared absorption spectra of ten individual contaminant materials and four binary mixtures of these have been studied using the internal reflection spectroscopy technique. The effect of ultraviolet radiation on these contaminants has also been studied. It has been observed that all siloxanes, silanes, and esters are drastically affected by ultraviolet irradiation. In most cases polymerization and tar formation results

The Principal Magnetic Susceptibilities of Single Crystals of Rare Earth Salts at Low Temperatures. Part III—Neodymium Salts

The principal susceptibilities of neodymium salts have been measured from room temperature down to liquid air temperature. The results are discussed in terms of Crystalline Field Theory. It is found that (1) though the mean susceptibility can be explained satisfactorily on the basis of a single cubic field even of the fourth degree, the absolute magnitude of the fourth order cubic field estimated in this manner from the magnetic data will not be correct, (2) the cubic part of the field in the various neodymium salts estimated from magnetic data on the assumption that the cubic part of the field is wholly of the fourth degree, is found to vary markedly from crystal to crystal. (3) The influence of the fourth and six degree terms of the cubic field on the Stark splitting of the rare earth ions and in crystals, and their large magnetic anisotropy go to show that the low lying energy levels as observed in absorption spectra cannot be attributed to cubic field alone.(4)The X1—axis of neodymium sulphate rotates by about 7a In the range studied

The Principal Magnetic Susceptibilities of Single Crystals of Rare Earth Salts at Low Temperatures. Part II. Praseodymium Salts

The principal susceptibilities of praseodymium salts have been measured from room temperature down to liquid air temperature, The results are discussed in terms of the crystalline electric field theory. It is found that (1) on the basis of a single Suitable cubic field the observed magnetic moment at all temperatures in the range studied can be explained satisfactorily. (2) The observed large anisotropies of the crystals point to the existence 0f strongly asymmetric rhombic field. (3) a rough estimate of the rhombic part of the field shows that the splitting by it is by no means small and compares favorably with the cubic splitting. (4) The X1-axis of praseodymium sulphate rotates by about 63 degrees in the range studied

How Can We Better Evaluate Complex Global Health Initiatives? Reflections From the January 2014 Institute of Medicine Workshop.

An IOM workshop on evaluation design drew on recent evaluations of 4 complex initiatives (PEPFAR; the Global Fund to Fight AIDS, TB and Malaria; the President’s Malaria Initiative; and the Affordable Medicines Facility-malaria). Key components for good evaluations: (1) a robust theory of change to understand how and why programs should work; (2) use of multiple analytic methods; and (3) triangulation of evidence to validate and deepen understanding of results as well as synthesis of findings to identify lessons for scale-up or broader application