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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1964

Space-Cabin Atmospheres: Part II - Fire and Blast Hazards. A Literature Review

The rapid evolution of aircraft and, lately, space vehicles has brought with it the ever-increasing difficulty of designing for prevention of fires and explosions. The present-day sealed cabin with its limited work space, unusual atmospheric constituents, and lack of flexibility in emergency situations has brought new and ill-defined hazards into the picture. In the past, numerous data have been compiled on the fire and explosion characteristics of all things combustible. Unfortunately, much of the material is not pertinent to the actual operational problems in space. The confusion and controversy arising from attempts to evaluate the space-cabin fire problem appear to stem from past failure to compile the scattered data and to expose it to critical review and selection. In the compilation that follows, an attempt has been made to review the best available data that was deemed actually pertinent to the present problem. The effects of unusual atmospheres have been emphasized, but, as will soon be evident, other physical parameters also play a major role in determining the nature of the problem. Chapter 1 contains a discussion of pertinent definitions and theory. This is detailed only to the point of anticipating some of the problems of interpretation that may arise in other chapters of the report. Included in this chapter is speculation on the impact of unusual environmental conditions such as aerodynamic heating, reduced gravitational acceleration, and low ambient pressures. Chapter 2 covers flammable fabrics and carbonaceous solids; Chapter 3, specific fire hazards involving flammable liquids, vapors, and gases; and Chapter 4, electrical fires. Chapter 5 covers the fire, blast, and flash hazards from meteoroid penetration; and Chapter 6, the problems of fire prevention and extinguishment in space cabins. Chapter 7 reviews the factors of fire and blast hazards in selection of a space-cabin atmosphere.

Roth, Emanuel M.↗
NASA NTRS1966

Cryogenic trap valve has no moving parts

Aluminum-body trap valve with an invar stem keeps cryogenic materials in the liquid state while entering the final component of a system. The valve has no moving parts and is self-actuated and self-monitoring.

Branum, L. W.↗
NASA NTRS1966

Seal-off assembly permits rapid evacuation of air from containers

Seal-off assembly which permits rapid container evacuation using large diameter tubing has a vacuum valve that permits sealing plate transfer from the vacuum valve stem to the container after evacuation. The sealing plate can be reused repeatedly. This device can repump in case of a small leak without exposing the container to the atmosphere.

Demers, R. R.↗
NASA NTRS1966

Biology and the Exploration of Mars

Until recent years the origin of life and its possible occurrence elsewhere in the universe have been matters for speculation only. The rapid growth of molecular biology since 1940 has, to be sure, made it possible to discuss life's origins in far more precise and explicit terms than was possible earlier; and the subject entered a new experimental phase in the 1950's with successful abiogenic synthesis of important biochemical substances in conditions simulating the presumptive environment of the primitive Earth. But the real transformation that the subject has undergone stems from the spectacular growth of space technology in the last decade. The possibility of life's origin and occurrence on planets other than ours is no longer limited to idle speculation: it has entered the realm of the testable, of science in the strict sense. Given the rockets now available, and especially those available by 1969, it has become fully realistic to consider plans for the biological exploration of Mars. The study that this report seeks to interpret was initiated in June, 1964, by the Space Science Board of the National Academy of Sciences to examine this possibility. The working group comprised 36 people representing a broad spectrum of scientific interests: evolutionary biology, genetics, microbiology, biochemistry and molecular biology, animal physiology, soil chemistry, organic chemistry, planetary astronomy, geochemistry, and theoretical physics. The participants included some with considerable prior involvement in problems of space exploration and others with none. Advice was also sought outside the group of immediate participants on the potentialities of selected analytical methods for the experimental study of extraterrestrial life and its environment. More than 30 individuals contributed in this fashion written assessments of techniques in which they were particularly well versed. Our task was to examine the scientific foundations and merits of the proposal to undertake a biological exploration of Mars. What are the potential scientific yields? How valuable, if attained, would they be? What, in fact, is the possibility of life occurring on Mars? And of our detecting it with available and foreseeable technology? What could be achieved by further astronomical work from Earth? by Martian fly-by missions? by Martian orbiters? and Martian Landers? What payloads would we recommend for planetary missions? What timing and over-all strategy would we recommend for Martian exploration were we to consider it worthwhile at all? In brief, the over-all purpose was to recommend to. the government, through the Academy's Space Science Board, whether or not a biological exploration of Mars should be included in the nation's space program over the next few decades; and, further, to outline what that program, if any, should be.

CONFERENCE↗
NASA NTRS1968

On the Equilibrium Figure of the Earth

If de Sitter's hydrostatic equations are developed independent of the external potential theory, the hydrostatic geopotential coefficient J(sub h) occurs explicitly on the right-hand side of those equations. J(sub h) here has to be treated as an unknown in the solution, it becomes rather difficult to solve the equations independently, regardless of which of the dynamical parameters associated with the earth is taken as the initial datum. Solution is possible, however, with the help of a boundary condition derived from the external potential theory which neither assumes nor discounts the presence of equilibrium conditions in the earth's interior. If a general solution i s constructed on this basis, the three particular solutions, usually quoted in literature, stem from it in the wake of the appropriate assumptions. Of course, the only meaningful solution--of these-- is that corresponding to the polar moment of inertia as the initial datum. It is essential that the solution be constructed in this way in order to demonstrate clearly the correct structure of the problem of hydrostatic equilibrium. The anomalous gravity field of the earth referred to the hydrostatic figure is compared with that referred to the international reference ellipsoid.

Khan, M. A.↗
NASA NTRS1971

Lunar Shelter Habitability Evaluation

Results are reported of an Investigation to determine the capability of pressure suited personnel to deploy lunar shelter/airlock structures install mockup life support, power and miscellaneous equipment within and outside the shelter, and adequately utilize this equipment after installation. Information was obtained on: (1) dimensional requirements for lunar shelter interiors, hatches, and airlocks, (2) limitations imposed on lunar shelter design by pressure suited crewmen, (3) times associated with various work tasks, and (4) redesign recommendations for a lunar stay time extension module (STEM).

Mattingly, G. Samuel↗
NASA NTRS1972

A valve concept for remote fluid flow control

Valve concept has been devised which offers lightweight, simplified mechanism capable of automatic control of large number of fluid flow ports. Valve control is achieved with valve stem which is bimetallic device activated by heating coil to open or close selected supply port. Number of controlled ports is limited only by desired physical size of system.

Flynn, W. J.↗
NASA NTRS1972

High intensity portable fluorescent light

Eight high intensity portable fluorescent lights were produced. Three prototype lights were also produced, two of which were subsequently updated to the physical and operational configuration of the qualification and flight units. Positioning of lamp apertures and reflectors in these lights is such that the light is concentrated and intensified in a specific pattern rather than widely diffused. Indium amalgam control of mercury vapor pressure in the lamp gives high output at lamp ambient temperatures up to 105 C. A small amount of amalgam applied to each electrode stem helps to obtain fast warm-up. Shrinking a Teflon sleeve on the tube and potting metal caps on each end of the lamp minimizes dispersion of mercury vapor and glass particles in the event of accidental lamp breakage. Operation at 20 kHz allows the lamps to consume more power than at low frequency, thus increasing their light output and raising their efficiency. When used to expose color photographic film, light from the lamps produces results approximately equal to sunlight.

Kendall, F. B.↗
NASA NTRS1971

Time-dependent polymer rheology under constant stress and under constant shear conditions.

A kinetic rate theory previously presented for describing non-Newtonian phenomena has been further modified to predict the flow behavior of viscoelastic materials under constant stress conditions. The thixotropic shear stress or shear rate is predicted by the kinetic theory, and the experimental stress or shear rate is obtained by modifying the thixotropic value by a stress or shear rate retardation term. The retardation term stems from a Maxwellian approach for stress retardation. In order to test the validity of this approach, transient and steady-state data were obtained for two solutions of polymethylmethacrylate in diethylphthalate. Both constant stress measurements and constant shear rate data were taken over a broad range.

Lee, K. H.↗
NASA NTRS1971

Erythropoietic radiosensitivity of the rat during altitude acclimatization.

The effect of a sublethal dose (300 R) of X-radiation upon the erythropoietic system of the rat, during 60-day acclimatization to moderate hypoxia (3,800 m altitude), was studied. Past work has shown that hypoxic animals are damaged less by radiation than animals irradiated in a normal environment; therefore, it was postulated that if, after acclimatization to hypoxia the bone marrow oxygen tension returns to sea-level values, these animals should suffer radiation damage equivalent to animals at sea level. The principal parameters followed were the rate of depletion of injected Fe-59 from the plasma of chronically catheterized rats, and its subsequent reappearance in the circulating erythrocytes. After 20 days of acclimatization, both parameters for altitude-irradiated animals returned to the values of animals irradiated at sea level, previously having reflected increased erythropoiesis. In altitude nonirradiated animals the parameters indicated erythropoietic stimulation persisting up to 45 days acclimatization. The protective effect of the hypoxia on the stem cells vanished during acclimatization, presumably as cellular oxygen tension rose.

Gaugl, J. F.↗
NASA NTRS1972

The method of models in variational scattering calculations.

It is shown that difficulties in atomic scattering calculations that stem from the use of inexact target wave functions can be overcome by employing the so-called method of models, provided that the projectile is distinguishable from the atomic electrons. The proposed method of models consists in replacing the target hamiltonian by a model hamiltonian, of which the appropriate target state is an eigenfunction. A connection with the positron scattering work of Peterkop and Rabik (1971) has been established.

Drachman, R. J.↗
NASA NTRS1972

The III-V photocathode - A major detector development.

Description of new (III-V) photocathodes which show improvements in sensitivity of as much as ten to a hundred times over conventional cathodes in the near infrared and useful improvements at shorter wavelengths. The development stems from a combination of basic knowledge of the photoemission process, gained in the 1950s, and the advancing understanding of the technology of III-V materials, in the 1960s. The superior performance of these cathodes is due to the fact that the vacuum level at the surface lies below the bottom of the conduction band in the bulk of the material. Consequently, the threshold of response is set by the III-V bandgap. The bandgap (and the threshold of response) can be varied by alloying different III-V materials together. A reduction in thermionic emission is realized with these cathodes. At present no semitransparent III-V cathodes with comparably interesting performance are available. The problems hindering further improvements, as well as the problems of placing these cathodes in practical multipliers and image tubes, are discussed briefly.

Spicer, W. E.↗
NASA NTRS1972

Analog simulation of a gas pressure regulator.

The behavior characteristics of direct-acting gas pressure regulators are discussed in terms of spring force, flow force, and friction force. The dynamics of the metering valve and bellows assembly are described by equating all forces on the valve to zero. Continuity equations for the regulator are derived. Simulations are carried out to determine effects of sensing orifice diameter, poppet stem friction, output volume, and supply pressure on regulator behavior. Several regulator configurations are studied.

Dustin, M. O.↗