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At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Making Latex Microspheres in Space

Equipment yields larger, more uniform particles. Two NASA reports describe first commercial product to be manufactured in space. Product monodisperse latex, suspension of spherical particles of essentially same diameter. Carried aboard Space Shuttle on its orbital missions, monodisperse latex reactor (MLR) produces spheres of much larger size than possible on Earth. Mircospheres 30 micrometers in diameter produced, whereas 5 micrometers is limit for Earthbound reactors. Microspheres as large as 100 micrometers scheduled for production in MLR.

Kornfeld, D. M.↗
NASA NTRS1986

Detecting Pores in SiC Coatings

Liquid-penetrant/fluorescence technique reveals cracks and pinholes in protective coatings. Developed for checking quality of overcoatings on silicon carbide layers on advanced carbon/carbon substrates. Technique similar to other liquid-penetrant/fluorescence techniques used to make pores visible. Porous areas absorb more suspension and therefore accumulate more fluorescent particles. They fluoresce more brightly than their surroundings.

Hamilton, A. B.↗
NASA NTRS1985

Mathematical Models of Continuous Flow Electrophoresis

Development of high resolution continuous flow electrophoresis devices ultimately requires comprehensive understanding of the ways various phenomena and processes facilitate or hinder separation. A comprehensive model of the actual three dimensional flow, temperature and electric fields was developed to provide guidance in the design of electrophoresis chambers for specific tasks and means of interpreting test data on a given chamber. Part of the process of model development includes experimental and theoretical studies of hydrodynamic stability. This is necessary to understand the origin of mixing flows observed with wide gap gravitational effects. To insure that the model accurately reflects the flow field and particle motion requires extensive experimental work. Another part of the investigation is concerned with the behavior of concentrated sample suspensions with regard to sample stream stability particle-particle interactions which might affect separation in an electric field, especially at high field strengths. Mathematical models will be developed and tested to establish the roles of the various interactions.

Saville, D. A.↗
NASA NTRS1985

Electrophoresis technology

A new high resolution apparatus designed for space was built as a laboratory prototype. Using a moving wall with a low zeta potential coating, the major sources of flow distortion for an electrophoretic sample stream are removed. Highly resolved fractions, however, will only be produced in space because of the sensitivity of this chamber to buoyancy-induced convection in the laboratory. The second and third flights of the McDonnell Douglas Astronautics Corporation continuous flow electrophoresis system carried samples developed at MSFC intended to evaluate the broad capabilities of free flow electrophoresis in a reduced gravity environment. Biological model materials, hemoglobin and polystyrene latex microspheres, were selected because of their past use as electrophoresis standards and as visible markers for fluid flow due to electroosmosis, spacecraft acceleration or other factors. The dependence of the separation resolution on the properties of the sample and its suspension solution was assessed.

Snyder, R. S.↗
NASA NTRS1985

Production of Large-Particle-Size Monodisperse Latexes in Microgravity

A latex is a suspension of very tiny (micrometer-size) plastic spheres in water, stabilized by emulsifiers. The growth of billions of these tiny plastic spheres to sizes larger than can be grown on Earth is attempted while keeping all of them exactly the same size and perfectly spherical. Thus far on several of the Monodisperse Latex Reactor (MLR) flights, the latex spheres have been returned to Earth with standard deviations of better than 1.4%. In microgravity the absence of buoyancy effects has allowed growth of the balls up to 30 micrometers in diameter thus far. The MLR has now flown 5 times on the Shuttle. The MLR has now produced the first commercial space product; that is the first commercial material ever manufactured in space and marketed on Earth. Once it is demonstrated that these large-size-monodisperse latexes can be routinely produced in quantity and quality, they can be marketed for many types of scientific applications. They can be used in biomedical research for such things as drug carriers and tracers in the body, human and animal blood flow studies, membrane and pore-sizing in the body, and medical diagnostic tests.

Vanderhoff, J. W.↗
NASA NTRS1985

Seeding techniques used in the Vortex Research Facility

For many years, the Vortex Research Facility used kerosene vapor as seeding particles. The kerosene vapor formed (approx. 1 micron) particles initially. After injection into the test section, the vapor would begin to condense and form larger particles. By switching to solid particles, this has been eliminated. The uniform-sized (approx. 1 micron) solid particle seeding is used both to seed the Laser Velocimeter system and for flow visualization. After injection, the solid particles reach a uniform suspension before the vehicle is launched. It is found that the kerosene vapor poses a problem because it is a heated gas which modified the test section temperature distribution. It also produces high turbulence and secondary air currents because it was continually injected from the time of vehicle launch until model passage. In cases where the effects of either turbulence or the vertical temperature distribution are of interest, this hot gas injection method is unsuitable. Both types of seeding particles provide adequate flow visualization but are sensitive to vertical temperature distributions.

Satran, D. R.↗
NASA NTRS1985

Seeding subsonic, transonic and supersonic flows with 0.5 micron polystyrene spheres

Polystyrene latex particles have been successfully used as laser velocimetry seed material for flows in the Ames High Reynolds Channels (HR) 1 and 2, the pilot channel, and the one-foot low speed tunnel. These facilities provide test flows with Mach numbers from 0.1 to 3.0 and test section sizes from 4 inches by 6 inches to 18 inches by 24 inches. Tunnel mass flow in the HR-2 channel can approach 1000 lb/sec. The latex particles have the following favorable characteristics: size of 0.35 to 0.55 microns diameter; spherical shape; specific gravity of 1.05; excellent flow trackability; low toxicity; and low cost. they have the disadvantage of being packaged as an aqueous suspension which must be diluted and introduced into the test flow as an atomized mist. This must occur sufficiently far upstream of the test section to minimize flow disturbances and permit the liquid mist to evaporate before reaching the model. Several techniques which have been developed to accomplish satisfactory seeding will be described.

Seegmiller, H. L.↗
NASA NTRS1985

Aerosol seeding systems for the NSWC wind tunnels

Four types of laskin nozzles which are used to generate the primary aerosol mist are illustrated. This mist may be used directly as laser doppler velocimeters (LDV) particles. However, in general, a wide range of particle size exists at this stage and requires the use of some type of mono-dispersion refinement technique. These nozzles rely on the shearing action of high speed air near a column of seeding liquid. Typically, olive oil or dioctyl phthalate (DOP) is used, but within the past year solid polystyrene particles in an alcohol suspension have been used with great success. Air, at a typical pressure of five psig, is supplied to the top of the nozzle which is merely a hollow tube. This air issues radially from one or more small jets located near the collar close to the bottom of the tube. When the collar is submerged in the seeding liquid, the hollow columns located in the collar become filled with liquid. The air from the jet shears the liquid into the fine mist.

Yanta, W. J.↗
NASA NTRS1985

Advanced Integrated Power and Attitude Control System (IPACS) study

Integrated Power and Attitude Control System (IPACS) studies performed over a decade ago established the feasibility of simultaneously satisfying the demands of energy storage and attitude control through the use of rotating flywheels. It was demonstrated that, for a wide spectrum of applications, such a system possessed many advantages over contemporary energy storage and attitude control approaches. More recent technology advances in composite material rotors, magnetic suspension systems, and power control electronics have triggered new optimism regarding the applicability and merits of this concept. This study is undertaken to define an advanced IPACS and to evaluate its merits for a space station application. System and component designs are developed to establish the performance of this concept and system trade studies conducted to examine the viability of this approach relative to conventional candidate systems. It is clearly demonstrated that an advanced IPACS concept is not only feasible, but also offers substantial savings in mass and life-cycle cost for the space station mission.

Oglevie, R. E.↗
NASA NTRS1986

Experimental and analytical generic space station dynamic models

A dynamic model used for verification of analytical and experimental methods is documented. The model consists of five substructures to simulate the multibody, low frequency nature of large space structures. Design considerations which led to a fundamental vibration frequency of less than one Hz are described. Finite element analysis used to predict the vibration modes and frequencies of the experimental model is presented. In addition, modeling of cable suspension effects using prestressed vibration analysis is described. Details of the expermental and analytical models are included to permit replication of the study. Results of the modal vibration tests and analysis are presented in a separate document.

Belvin, W. K.↗
NASA NTRS1986

Sediment-transport (wind) experiments in zero-gravity

The carousel wind tunnel (CWT) can be a significant tool for the determination of the nature and magnitude of interparticlar forces at threshold of motion. By altering particle and drum surface electrical properties and/or by applying electric potential difference across the inner and outer drums, it should be possible to separate electrostatic effects from other forces of cohesion. Besides particle trajectory and bedform analyses, suggestions for research include particle aggregation in zero and subgravity environments, effect of suspension-saltation ratio on soil abrasion, and the effects of shear and shearfree turbulence on particle aggregation as applied to evolution of solar nebula.

Iverson, J.↗
NASA NTRS1985

Growth of zeolite crystals in the microgravity environment of space

Zeolites are hydrated, crystalline aluminosilicates with alkali and alkaline earth metals substituted into cation vacancies (Equation A) M(sub 2/n) 0-Al203-XSi02-YH20 A They have a uniform internal channel system which makes them ideal for use as catalysts and adsorbents. Presently zeolite materials constitute a 1-2 mi 11 ion dol lar/year business. Typically zeolite crystals are 3-8 µm along their characteristic dimension (e.g., edge). Larger zeolite crystals are desirable. Large crystals will allow more detail characterization of their complex crystal structures. Also, they will help improve reactor performance, may be used as membrane separators, and they should enhance basic studies in molecular diffusion in zeolites. Large zeolite crystals have been produced (100-200 µm) ; however, they have taken restrictively long times to grow. It has been proposed if the rate of nucleation or in some other way the number of nuclei can be lowered, fewer, larger crystals will be formed. provide an ideal condition to achieve rapid growth of large zeolite crystals (e.g., >l00 µm). Since settling crystals are believed to cause secondary nucleation, by limiting crystal movement by suspension in the zero gravity environment, fewer crystals will form, but they will grow larger. The objective of the project is to establish if large zeolite crystals can be formed rapidly in space.

A. Sacco, Jr.↗
NASA NTRS1984

The temporal response of bone to unloading

Rats were suspended by their tails with the forelimbs bearing the weight load to simulate the weightlessness of space flight. Growth in bone mass ceased by 1 week in the hindlimbs and lumbar vertebrae in growing rats, while growth in the forelimbs and cervical vertebrae remained unaffected. The effects of selective skeletal unloading on bone formation during 2 weeks of suspension was investigated using radio iostope incorporation (with Ca-45 and H-3 proline) and histomorphometry (with tetracycline labeling). The results of these studies were confirmed by histomorphometric measurements of bone formation using triple tetracycline labeling. This model of simulated weightlessness results in an initial inhibition of bone formation in the unloaded bones. This temporary cessation of bone formation is followed in the accretion of bone mass, which then resumes at a normal rate by 14 days, despite continued skeletal unloading. This cycle of inhibition and resumption of bone formation has profound implication for understanding bone dynamics durng space flight, immobilization, or bed rest and offers an opportunity to study the hormonal and mechanical factors that regulate bone formation.

Globus, R. K.↗
NASA NTRS1985

Biochemical response to chronic shortening in unloaded soleus muscles

One leg of tail-casted suspended rats was immobilized in a plantar-flexed position to test whether chronic shortening of posterior leg muscles affected the metabolic response to unloading. The immobilized plantaris and gastrocnemius muscles of these animals showed approximately 20 percent loss of muscle mass in contrast to simply a slower growth rate with unloading. Loss of mass of the soleus muscle during suspension was not accentuated by chronic shortening. Although protein degradation in the isolated soleus muscle of the plantar-flexed limb was slightly faster than in the contralateral free limb, this difference was offset by faster synthesis of the myofibrillar protein fraction of the chronically shortened muscle. Total adenine nucleotides were 17 percent lower (P less than 0.005) in the chronically shortened soleus muscle following incubation. Glutamate, glutamine, and alanine metabolism showed little response to chronic shortening. These results suggest that, in the soleus muscle, chronic shortening did not alter significantly the metabolic responses to unloading and reduced activity.

Jaspers, S. R.↗
NASA NTRS1985

Designing a Mars surface rover

Only three categories of vehicular configuration are under consideration for the Mars rover geological exploration mission: a six-wheeled 'lunar roving vehicle' (LRV), an elastic loopwheeled mobility system (ELMS), and a 'walking' vehicle. The LRV uses three compliantly coupled modules, each of which is equipped with two powered wheels. The ELMS uses three loopwheels that are reminiscent of tracks mounted on an articulated suspension. Walkers, which use leg-like mechanisms, are the least developed of the three categories. A comparative assessment of the capabilities and economies of the three vehicle types is presented.

Ruoff, C.↗
NASA NTRS1984

Instrument pointing technology for spaceborne science missions of the 1990's

The technologies which will permit sub-0.1 arcsec pointing accuracies on spacecraft in the 1990s are examined, along with the accuracies required and the current state of the art. Of particular interest are multi-mission spacecraft. Pointing accuracy can only be obtained by integrating the instrument (telescope) as part of the spacecraft, minimizing disturbances and using reaction wheels for pointing. The pointer could be isolated from complex spacecraft disturbances by soft mechanical mounts, e.g., inflatible tethers, guy-wire suspension and fluidic pointing systems. All design options are being explored for the Space Station, Earth Observing System, Co-orbiting platform and GEO platform spacecraft, and for near-term planetary spacecraft which will employ nuclear electric propulsion.

Laskin, R. A.↗
NASA NTRS1986

Regulation of hematopoiesis in rats exposed to antiorthostatic hypokinetic/hypodynamia. II - Mechanisms of the 'anemia'

The cause of the red cell mass (RCM) deficit, which occurs in rats during suspenion, is investigated. The experimental conditions and procedures, in which male Sprague-Dawley rats are subjected to antiorthostatic hyypokinetic/hypodynamia and changes in RCM are monitored, are described. The influences of stress, reduced food and water consumption, and antiorhostatic posture on RCM are analyzed. Changes in body weight, RCM, radioiron incorporation, red blood cells (RBC), and reticulocytes, for the rats after head-down suspension are graphically presented; only the changes in RBC are related to the antiorthostatic posture. The data reveal that anemia is primarily caused by reduced food and water consumption and secondly by restricted movements.

Dunn, C. D. R.↗
NASA NTRS1986

Optimum transonic wind tunnel

The optimum facility to complement existing high Reynolds number transonic wind tunnels is discussed. It is proposed that the facility be cryogenic, have a total pressure of five atmospheres or less, and have a test section on the order of 4- to 5-meters square. The large size is to accommodate complicated models such as those used in propulsion testing. It is suggested that magnetic suspension and wall interference minimization and correction procedures be used. Simplicity of initial design is stressed as a means of providing for future growth opportunities.

Barnwell, R. W.↗