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Snyder, R. S.

Publications and source records attributed to Snyder, R. S..

33 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The effect of small temperature gradients on flow in a continuous flow electrophoresis chamber

Continuous flow electrophoresis employs an electric field to separate biological cells suspended in a flowing liquid buffer solution. Good separations based on differences in electrophoretic mobility are obtained only when a unidirectional flow is maintained. The desired flow has a parabolic structure in the narrow dimension of the chamber and is uniform acros the width, except near the edges where the no-slip condition prevails. However, because of buoyancy, very small laterall or axial temperature gradients deform the flow significantly. The results of experiments conducted with a specially instrumented chamber show the origin and structure of the buoyancy-driven perturbations. It is found that very small temperature gradients can disturb the flow significantly, as was predicted by earlier theoretical work.

Rhodes, P. H.↗
NASA NTRS1981

Effects of zero van der Waals and zero electrostatic forces on droplet sedimentation

The present investigation provides a confirmation of the dependence of droplet sedimentation on particle concentration. It is shown that it is possible to determine the maximum particle concentration which can remain stable on a given liquid from droplet sedimentation experiments. Droplet sedimentation can be reduced but not totally eliminated by the addition of appropriate amounts of dimethyl sulfoxide (DMSO) to reduce the van der Waals forces to zero. It was found that, at 12% DMSO, a maximum particle concentration of 6.3 x 10 to the 8th cells/ml of glutaraldehyde-fixed human erythrocytes suspended in physiological saline can remain stable on a D2O cushion.

Omenyi, S. N.↗
NASA NTRS1981

Electrophoretic separation of lunar soils in a space manufacturing facility

The feasibility of electrophoretic separation of lunar soil into its mineral constituents is discussed in this paper. The process and its applicability to lunar soil separation are considered in light of the special requirements of a space manufacturing effort. Data generated in studies at NASA-Marshall Space Flight Center, which assess the efficiency of electrophoretic separation of lunar soil, are discussed and evaluated.

Dunning, J. D.↗
NASA NTRS1979

Flow and thermal effects in continuous flow electrophoresis

In continuous flow electrophoresis the axial flow structure changes from a fully developed rectilinear form to one characterized by meandering as power levels are increased. The origin of this meandering is postulated to lie in a hydrodynamic instability driven by axial (and possibly lateral) temperature gradients. Experiments done at MSFC show agreement with the theory.

Saville, D. A.↗
NASA NTRS1977

Method of crystallization

A method is described for refining or growing bulk single crystals in an environment substantially free of gravity. The base material is suspended, positioned, and shaped as a containerless melt by wetting forces. Because no crucible is required, high temperature refractory materials can be processed.

Walter, H. U.↗
NASA NTRS1977

Space processing on Skylab and ASTP

The Skylab and Apollo Soyuz Test Project (ASTP) missions provided the opportunity the influence of micro-gravity on the processing of various materials. The results of physical and engineering experiments in metallurgy, fluids handling and crystal growth on two space missions are discussed. The majority of the experiments concern the solidification of alloys, semiconductors, and composite materials or basic liquid-liquid and solid-liquid interactions necessary to understand complex processing. Potential advantages of space processing to several materials disciplines are identified.

Snyder, R. S.↗
NASA NTRS1977

Static free-fluid electrophoresis in space

The weightless environment onboard spacecraft in drifting flight has provided a unique opportunity to do experiments that cannot be done on the ground. High resolution free-fluid electrophoresis of particles proposed in the late 1960s to take advantage of reduced gravity began with brief experiments done during two Apollo flights. The recent Apollo Soyuz Test Project mission had two major experiments that accomplished the separation of viable biological cells. Experiments now are being planned for the Space Shuttle which will attempt to achieve high resolution of the separated species by using zone electrophoresis. These experiments will return a quantity sufficient for laboratory testing and establish the potential of fractionation and purification of biological materials in space.

Snyder, R. S.↗
NASA NTRS1976

Summary of the pre-ASTP results

A general overview of materials experiments done on several Apollo missions and Skylab as well as the ground research that led to these experiments is given. Demonstrations of composite solidification, electrophoresis, and fluid flow were developed for Apollo. Fourteen different experiments in metal processing and single crystal growth were done in the space processing facility on Skylab. Metals were melted and solidified in a variety of configurations using different methods of heating to produce improved alloys and composite materials. Single crystals were grown by directional solidification and vapor transport to achieve uniform crystalline perfection, decreased structural defects, and homogeneity of the dopant material.

Snyder, R. S.↗
NASA NTRS1976

Facilities and experiment results of the NASA sounding rocket program

The NASA rocket program on reduced gravity materials experiments is reported, including experimental results obtained from the single-stage Black Brant VC sounding rockets first flight and the developed equipment. The first flight was made on 11 December 1975, and nine different experiments were done in the five min of weightlessness. All systems operated satisfactorily and each experiment generated interesting results and recorded phenomena that have been reported. Each of the experiments will be flown again in modified form to obtain additional data or check unexpected results on the multiple rocket launches planned each year. General-purpose apparatus and facilities are being developed and built to allow repeated experimentation of various materials by different investigators. For example, multiple-cavity furnaces with rapid heat-up and cool-down possibilities, providing isothermal and gradient thermal profiles, will accommodate a wide variety of solidification experiments. Special hardware satisfying specific individual requirements is also being developed.

Snyder, R. S.↗
NASA NTRS1976

Science demonstrations

Three demonstrations of scientific concepts concerning liquids were performed during the Apollo-Soyuz Test Project mission. Chemical foaming, spreading of liquids, and capillary wicking were the subjects of each demonstration photographed in space. The results clearly illustrated the basic principles, and films suitable for educational uses are now available from the first author.

Snyder, R. S.↗
NASA NTRS1976

Metal melting, joining, and alloying under weightlessness

During the Skylab mission experiments were conducted concerning the influence of weightlessness on molten metals and the solidification process. It was found that the absence of gravity-induced thermal convection and sedimentation modified the properties of the bulk melt. A metals melting experiment was conducted to study the behavior of metal melted by an electron beam and to evaluate the feasibility of joining metals in space. An exothermic brazing experiment investigated the spreading, mixing, and capillary flow of molten braze material. The containerless melting and solidification of small samples of several metals was studied in another experiment. A description is also given of a study of the directional solidification of solid solution alloys.

Snyder, R. S.↗
NASA NTRS1974

Role of gravity in preparative electrophoresis

Electrophoresis has contributed significantly to the methodology of biological sciences, and shows the potential for large scale fractionation of a wide range of medically important substances, including living cells. Gravity plays an important role in the electrophoretic process, and hence the importance of the NASA effort to develop a zero-gravity separation facility as part of its shuttle program. The current state of art in electrophoresis is reviewed with particular emphasis on the role of gravity and the possible use of istachophoresis. This technique utilizes a discontinuous buffer system, and appears to be the only high resolution electrophoretic technique currently available for separation of living cells.

Bier, M.↗
NASA NTRS1974

Electrophoresis in space at zero gravity

Early planning for manufacturing operations in space include the use of electrophoresis for purification and separation of biological materials. Greatly simplified electrophoresis apparatus have been flown in the Apollo 14 and 16 missions to test the possibility of stable liquid systems in orbit. Additionally, isoelectric focusing and isotachophoresis are of particular interest as they offer very high resolution and have self-sharpening boundaries. The value of possible space electrophoresis is substantial. For example, present technology permits large fractionation of only a few of blood proteins many fractions, and separated cell populations are needed for research.

Bier, M.↗
NASA NTRS1972

Electrophoresis demonstration on Apollo 16

Free fluid electrophoresis, a process used to separate particulate species according to surface charge, size, or shape was suggested as a promising technique to utilize the near zero gravity condition of space. Fluid electrophoresis on earth is disturbed by gravity-induced thermal convection and sedimentation. An apparatus was developed to demonstrate the principle and possible problems of electrophoresis on Apollo 14 and the separation boundary between red and blue dye was photographed in space. The basic operating elements of the Apollo 14 unit were used for a second flight demonstration on Apollo 16. Polystyrene latex particles of two different sizes were used to simulate the electrophoresis of large biological particles. The particle bands in space were extremely stable compared to ground operation because convection in the fluid was negligible. Electrophoresis of the polystyrene latex particle groups according to size was accomplished although electro-osmosis in the flight apparatus prevented the clear separation of two particle bands.

Snyder, R. S.↗