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At least 1,351 records · Page 75

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NASA NTRS1987

Effect of component compression on the initial performance of an IPV nickel-hydrogen cell

An experimental method was developed for evaluating the effect of component compression on the charge and discharge voltage characteristics of a 3 1/2 in. diameter boiler plate cell. A standard boiler plate pressure vessel was modified by the addition of a mechanical feedthrough on the bottom of the vessel which permitted different compressions to be applied to the components without disturbing the integrity of the stack. Compression loadings from 0.94 to 27.4 psi were applied by suspending weights from the feedthrough rod. Cell voltages were measured for 0.96-C, 55-min charge and for 1.37-C, 35-min and 2-C, 24-min discharges. An initial change in voltage performance on both charge and discharge as the loading increased was attributed to seating of the components. Subsequent variation of the compression from 2.97 to 27.4 psi caused only minor changes in either the charge or the discharge voltages. Several one month open-circuit voltage stands and 1100 cycles under LEO conditions at the maximum loading have produced no change in performance.

Gahn, Randall F.↗

NASA NTRS1987

Oxygen chemisorption cryogenic refrigerator

The present invention relates to a chemisorption compressor cryogenic refrigerator which employs oxygen to provide cooling at 60 to 100 K. The invention includes dual vessels containing an oxygen absorbent material, alternately heated and cooled to provide a continuous flow of high pressure oxygen, multiple heat exchangers for precooling the oxygen, a Joule-Thomson expansion valve system for expanding the oxygen to partially liquefy it and a liquid oxygen pressure vessel. The primary novelty is that, while it was believed that once oxygen combined with an element or compound the reaction could not reverse to release gaseous oxygen, in this case oxygen will indeed react in a reversible fashion with certain materials and will do so at temperatures and pressures which make it practical for incorporation into a cryogenic refrigeration system.

Jones, Jack A.↗

NASA NTRS1988

The effects of normal and therapeutic baths on the central vascular organs of persons with healthy hearts, as measured by X-ray

According to current information, baths have a four-fold effect on the circulation: (1) Dilation or constriction is produced in the area of the blood vessels in the skin as a result of thermal, chemical or mechanical stimuli; (2) This reaction in the dermal vascular system produces a further effect on the central vessels in the extremities, the area of the splanchnicus, and other body cavities; (3) The reflect transposition of other organ systems, i.e., the respiratory organs, has a reaction on the circulation; and (4) The water pressure of the bath has a hydrostatic effect, i.e., on the one hand it empties peripheral veins more rapidly, and on the other it increases the intra-abdominal pressure and this reduces once again the circulation in the area of the splanchnicus.

Boehm, G.↗

NASA NTRS1987

Effect of component compression on the initial performance of an IPV nickel-hydrogen cell

Gahn, Randall F.↗

NASA NTRS1989

Fluidized-Bed Reactor With Zone Heating

Deposition of silicon on wall suppressed. In new fluidized bed, silicon seed particles heated in uppermost zone of reactor. Hot particles gradually mix with lower particles and descend through fluidized bed. Lower wall of vessel kept relatively cool. Because silane enters at bottom and circulates through reactor pyrolized to silicon at high temperatures, silicon deposited on particles in preference wall. Design of fluidized bed for production of silicon greatly reduces tendency of silicon to deposit on wall of reaction vessel.

Iya, Sridhar K.↗

NASA NTRS1988

Ultrasonic depth gauge for liquids under high pressure

An ultrasonic depth gauge 20 for liquids under high pressure is comprised of a transducer assembly 21 and a supporting electronics unit 22. The transducer assembly is mounted into the bottom wall of a storage vessel 12 with its resonating surface directly exposed to the highly pressurized liquid 13 in the vessel. The transducer assembly consists of a conventional transducer element 38 rigidly bonded to the inside wall of a bored out conventional high-pressure plug 30 thereby forming a composite resonator 50. The element and the plug wall resonate as one upon electrical excitation of the element while the transducer element is completely shielded from any exposure to the liquid under high pressure. The composite resonator sends a vibration up to the surface of the liquid where it is reflected back to the composite resonator. The supporting electronics unit measures the vibrations round-trip transit time which is proportional to the depth 15 of the liquid.

Allan J Zuckerwar↗

NASA NTRS1988

In situ observations of ClO in the Antarctic: Evidence for chlorine catalyzed destruction of ozone

Results from a series of 12 ER-2 aircraft flights into the Antarctic polar vortex are summarized. These in situ data define the spatial and temporal distribution of ClO as the aircraft flew at an altitude of approx. 18 km from Punta Arenas (54 deg S latitude) to the base of the Palmer Peninsula (72 deg S latitude), executed a rapid descent to approx. 13 km, turned north and climbed bach to approximately 18 km, returning to Punta Arenas. A general pattern in the ClO distribution is reported: mixing ratios of approximately 10 ppt are found at altitude in the vicinity of 55 deg S increasing to 50 ppt at 60 degrees S. In the vicinity of 65 deg S latitude a steep gradient in the ClO mixing ratio is observed. At a fixed potential temperature, the ClO mixing ratio through this sharp transition increases by an order of magnitude within a very few degrees of latitude, thus defining the edge of the chemical containment vessel. From the edge of that containment vessel to the southern extension of the flights, 72 deg S, a dome of slowly increasing ClO best describes the distribution. Conclusion are drawn from the data.

Anderson, J. G.↗

NASA NTRS1988

Human cell culture in a space bioreactor

Microgravity offers new ways of handling fluids, gases, and growing mammalian cells in efficient suspension cultures. In 1976 bioreactor engineers designed a system using a cylindrical reactor vessel in which the cells and medium are slowly mixed. The reaction chamber is interchangeable and can be used for several types of cell cultures. NASA has methodically developed unique suspension type cell and recovery apparatus culture systems for bioprocess technology experiments and production of biological products in microgravity. The first Space Bioreactor was designed for microprocessor control, no gaseous headspace, circulation and resupply of culture medium, and slow mixing in very low shear regimes. Various ground based bioreactors are being used to test reactor vessel design, on-line sensors, effects of shear, nutrient supply, and waste removal from continuous culture of human cells attached to microcarriers. The small Bioreactor is being constructed for flight experiments in the Shuttle Middeck to verify systems operation under microgravity conditions and to measure the efficiencies of mass transport, gas transfer, oxygen consumption and control of low shear stress on cells.

Morrison, Dennis R.↗

NASA NTRS1989

Investigation of Weibull statistics in fracture analysis of cast aluminum

The fracture strengths of two large batches of A357-T6 cast aluminum coupon specimens were compared by using two-parameter Weibull analysis. The minimum number of these specimens necessary to find the fracture strength of the material was determined. The applicability of three-parameter Weibull analysis was also investigated. A design methodology based on the combination of elementary stress analysis and Weibull statistical analysis is advanced and applied to the design of a spherical pressure vessel shell. The results from this design methodology are compared with results from the applicable ASME pressure vessel code.

Holland, Frederic A., Jr.↗

NASA NTRS1989

Transition to turbulence in laminar hypersonic flow

Progress in a recently started project aimed at the prediction of transition to turbulence in hypersonic flow is briefly discussed. The prediction of transition to turbulence is a very important issue in the design of space vessels. Two space vehicles currently under investigation, namely the aeroassisted transfer vehicle (AOTV) and the trans-atmospheric vehicle (TAV), suffer from strong aerodynamic heating. This heating is strongly influenced by the boundary layer structure. These aerospace vehicles fly in the upper atmospheric layer at a Mach number between 10 and 30 at very low atmospheric pressures. At very high altitudes the flow is laminar, but when the space vessel returns to a lower orbit, the flow becomes turbulent and the heating is dramatically increased. The prediction of this transition process is commonly done by means of experiments. The experimental facilities available nowadays cannot model the hypersonic flow field accurately enough by limitations in Mach and Reynolds number. These facilities also have a large free stream disturbance level which makes it very difficult to investigate transition accurately. An alternative approach is to study transition by theoretical means. Up to now numerical studies of hypersonic flow only discussed steady laminar or turbulent flow. This theoretical approach is extended to the study of transition in hypersonic flow by means of direct numerical simulations and additional theoretical investigations to explain the mechanisms leading to transition. A brief outline of how this research is to be performed is given.

Vandervegt, Jaap↗

NASA NTRS1990

Hollow-Fiber Clinostat

Hollow-fiber clinostat, is bioreactor used to study growth and other behavior of cells in simulated microgravity. Cells under study contained in porous hollow fiber immersed in culture medium inside vessel. Bores in hollow fiber allow exchange of gases, nutrients, and metabolic waste products between living cells and external culture media. Hollow fiber lies on axis of vessel, rotated by motor equipped with torque and speed controls. Desired temperature maintained by operating clinostat in standard tissue-culture incubator. Axis of rotation made horizontal or vertical. Designed for use with conventional methods of sterilization and sanitation to prevent contamination of specimen. Also designed for asepsis in assembly, injection of specimen, and exchange of medium.

Rhodes, Percy H.↗

NASA NTRS1990

Nondestructive Technique To Assess Embrittlement In Steels

Recent research at NASA Langley Research Center led to identification of nondestructive technique for detection of temper embrittlement in HY80 steel. Measures magnetoacoustic emission associated with reversible motion of domain walls at low magnetic fields. Of interest to engineers responsible for reliability and safety of various dynamically loaded and/or thermally cycled steel parts. Applications include testing of landing gears, naval vessels, and parts subjected to heat, such as those found in steam-pipe fittings, boilers, turbine rotors, and nuclear pressure vessels.

Allison, Sidney G.↗

NASA NTRS1989

Suitport extra-vehicular access facility

In a system for entering and leaving a space station, a bulkhead divides the module into an antechamber and an airlock. A space suit has a portable life support system (PLSS) interface on its back. The suit is removably attached to the bulkhead by the interface at a hatch in the bulkhead. A PLSS is detachably mounted in the hatch cover, which is pivotally mounted to move away from the hatch to allow an astronaut to enter the suit through the open hatch and the PLSS interface. After entering the suit, the astronaut closes the hatch and attaches the PLSS to the suit by the operating control to which the glove portion of the suit is attached. The astronaut initiates pumpdown of the airlock with the control. When the pumpdown is complete, the astronaut opens the hatch, disconnects the PLSS from the hatch cover, pivots the pressure vessels of the control to one side on their supports, disconnects the glove portions from the pressure vessels and goes EVA.

Cohen, Marc M.↗

NASA NTRS1989

Gravity field of the Western Weddell Sea: Comparison of airborne gravity and Geosat derived gravity

Marine gravity surveying in polar regions was typically difficult and costly, requiring expensive long range research vessels and ice-breakers. Satellite altimetry can recover the gravity field in these regions where it is feasible to survey with a surface vessel. Unfortunately, the data collected by the first global altimetry mission, Seasat, was collected only during the austral winter, producing a very poor quality gravitational filed for the southern oceans, particularly in the circum-Antarctic regions. The advent of high quality airborne gravity (Brozena, 1984; Brozena and Peters, 1988; Bell, 1988) and the availability of satellite altimetry data during the austral summer (Sandwell and McAdoo, 1988) has allowed the recovery of a free air gravity field for most of the Weddell Sea. The derivation of the gravity field from both aircraft and satellite measurements are briefly reviewed, before presenting along track comparisons and shaded relief maps of the Weddell Sea gravity field based on these two data sets.

Bell, R. E.↗

NASA NTRS1990

Spacecraft attitude impacts on COLD-SAT non-vacuum jacketed LH2 supply tank thermal performance

The Cryogenic On-Orbit Liquid Depot - Storage, Acquisition and Transfer (COLD-SAT) spacecraft will be launched into low earth orbit to perform fluid management experiments on the behavior of subcritical liquid hydrogen (LH2). For determining the optimum on-orbit attitude for the COLD-SAT satellite, a comparative analytical study was performed to determine the thermal impacts of spacecraft attitude on the performance of the COLD-SAT non-vacuum jacketed LH2 supply tank. Tank thermal performance was quantified by total conductive and radiative heat leakage into the pressure vessel due to the absorbed solar, earth albedo and infra-red on-orbit fluxes, and also by the uniformity of the variation of this leakage on the vessel surface area. Geometric and thermal analysis math models were developed for the spacecraft and the tank as part of this analysis, based on their individual thermal/structural designs. Two quasi-inertial spacecraft attitudes were investigated and their effects on the tank performance compared. The results are one of the criteria by which the spacecraft orientation in orbit was selected for the in-house NASA Lewis Research Center design.

Arif, Hugh↗

NASA NTRS1990

Spacecraft attitude impacts on COLD-SAT non-vacuum jacketed LH2 supply tank thermal performance

The Cryogenic On-Orbit Liquid Depot - Storage, Acquisition and Transfer (COLD-SAT) spacecraft will be launched into low earth orbit to perform fluid management experiments on the behavior of subcritical liquid hydrogen (LH2). For determining the optimum on-orbit attitude for the COLD-SAT satellite, a comparative analytical study was performed to determine the thermal impacts of spacecraft attitude on the performance of the COLD-SAT non-vacuum jacketed LH2 supply tank. Tank thermal performance was quantitied by total conductive and radiative heat leakage into the pressure vessel due to the absorbed solar, earth albedo and infra-red on-orbit fluxes, and also by the uniformity of the variation of this leakage on the vessel surface area. Geometric and thermal analysis math models were developed for the spacecraft and the tank as part of this analysis, based on their individual thermal/structural designs. Two quasi-inertial spacecraft attitudes were investigated and their effects on the tank performance compared. The results are one of the criteria by which the spacecraft orientation in orbit was selected for the in-house NASA Lewis Research Center design.

Arif, Hugh↗

NASA NTRS1989

Investigation of Weibull statistics in fracture analysis of cast aluminum

The fracture strengths of two large batches of A357-T6 cast aluminum coupon specimens were compared by using two-parameter Weibull analysis. The minimum number of these specimens necessary to find the fracture strength of the material was determined. The applicability of three-parameter Weibull analysis was also investigated. A design methodolgy based on the combination of elementary stress analysis and Weibull statistical analysis is advanced and applied to the design of a spherical pressure vessel shell. The results from this design methodology are compared with results from the applicable ASME pressure vessel code.

Holland, F. A., Jr.↗

NASA NTRS1990

IAL SPACE: A test laboratory for the ISO cryogenic payload

The ESA Infrared Space Observatory (ISO) satellite is a 3 axes pointed platform designed to make accurate pointed observations of astronomical objects and sources in the wavelength range between 2.5 and 200 microns. ISO is composed of a service module and a payload module which is a large cylindrical vacuum vessel. The vessel is in fact a cryostat (capacity of 2250 l of liquid He II) which contains the telescope and the four focal scientific instruments. The latter being cooled up to a temperature less than 4 K. The qualification of the payload requires the measurement respectively of: the image quality of the telescope through wave front error (WFE) measurements; and the optical alignment of the scientific instruments with respect to the telescope axis and the telescope focus, and this under cryogenic conditions. Consequently, since 1988, the FOCAL 5 IAL Space facility has been upgraded in order to perform the cryogenic optical tests of the ISO optical subsystems.

Cucchiaro, A.↗