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形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2018-06-29, 資料番号: PA1910055000

Water is matter for life on Earth and influences every aspect of our living planet. Water is crucial in forming the Earth’s unique ecosystem environment that supports the survival of human beings and other lives. Under the forcing of solar radiation, earth gravity, and other energy interaction, water cycle is the cyclical processes of transformation of water, including the transmission and phase transitions of water in the land, ocean, and atmosphere ( Trenberth et al., 2007 ; Trenberth et al., 2011 ; Oki and Kanae, 2006 ). The presence of water makes the earth unique from other planets.

We will discuss the following question: is the present day normal gravity field calculation suitable from the aspect of the applied geophysics/gravimetry? Today, the normal field or theoretical gravity is on a regular basis strictly related to a model of rotational biaxial ellipsoid with one important property, namely the constant potential on its surface. This condition, however, would require a specific density distribution within the model. Another issue is the treating the Earth atmosphere and topography. These masses are simply moved into the interior of such ellipsoid and “dissolved” there. In short, this approach does not fit the geophysical reality very well. Instead, in our contribution, we attempt to calculate the normal field as the gravity effect of a layered rotational ellipsoid, namely the gravitational effect of a suitable set of homeoid shells bounded by two similar ellipsoids having a constant ratio of axes, plus the centrifugal component. We believe that this approach will fit the structure and density distribution within the Earth much better. We analyze and present the primary differences between the two approaches, and we also discuss the relation of the normal field to the free-air correction.

Past efforts in developing an understanding of nucleate boiling under reduced gravity conditions have been mostly experimental. Often conjectures are made to explain the observed phenomena. In this chapter, numerical simulations of the process are used to simulate bubble dynamics and associated heat transfer at earth normal gravity, at 1/100th of earth gravity, and at microgravity conditions. The simulation results have been validated with experiments conducted on earth, in parabolic flights, and on the International Space Station. Numerical simulations are extended to predict nucleate boiling heat transfer on microfabricated and ordinary surfaces that are placed normal to the major gravity vector. In predicting the dependence of nucleate boiling heat flux on superheat correlations available in the literature for number density of active nucleation sites and waiting periods are used. For microfabricated surfaces, number of active sites and their location on the surface, as observed in experiments, were used as input to the model. Consistent with data from experiments, numerical simulations show that with reduced gravity heat transfer rate degrades.

This chapter provides detailed examples of thermo-gravitational, thermo-capillary and thermo-solutal instabilities. When a fluid is confined and in normal Earth gravity, the fluid configuration is vertically anti-symmetric. If suddenly exposed to weightlessness, the fluid will transition to a symmetric configuration over a period of time. Thermo-capillary instabilities have been observed during sessile droplet evaporation in the absence of buoyancy-driven convection and radiation. When the droplet rests on a thermally insulating substrate, no thermo-capillary convection is measured. However, if the substrate is thermally conductive, a transition to thermo-capillary flow has been observed and the transition depends on the evaporation rate. When a droplet evaporates into multicomponent atmospheres, thermo-solutal instabilities arise if one of the atmosphere species has a heat of solution with the droplet component. The thermo-solutal instabilities appear as temperature and pressure pulsations in the liquid and in the vapor phases that are coupled by the evaporation flux.

Absolute gravity meters are by definition calibrated instruments that measure gravity in natural units m s − 2 traceable to metrological standards. The first absolute gravity meters were pendulums, but these were eventually replaced by measurements of freely falling test masses in a vacuum. The most accurate instruments currently track a falling mirror with a laser interferometer. In the future, these instruments may become smaller by replacing the falling mirrors with atoms. Relative gravity meters are typically characterized by a mass on some type of spring support. Relative gravity meters must be calibrated to determine the scale factor that converts spring stretch into equivalent force and finally into gravity. Both types of gravity meters are useful for measuring gravity at a point near the surface of the Earth or at many points over a survey region. These measurements are useful for commercial resource exploration and management. They can also be used to determine the shape of the Earth's gravity field, which in turn defines the shape of the Earth. Gravity measurements repeated over time can be useful to look for changes in subsurface density or even to help understand problems of global sea-level rise or the melting of the ice sheets.

This chapter is designed to review the manufacturing and testing procedures used for developing heat pipes. The manufacture of conventional capillary driven heat pipes involves myriad simple operations, particularly when the unit is designed for operation at temperatures of the order of, say 50-200°C. It encapsulates skills such as welding, machining, chemical cleaning, and non-destructive testing, and can be carried out following a relatively small outlay on capital equipment. The most expensive item is likely to be the leak detection equipment. The life of a heat pipe often requires careful assessment in view of the many factors that can affect long-term performance. Measuring the performance of heat pipes is also a mandatory part of the work leading to an acceptable product. Test procedures for heat pipes destined for use in orbiting satellites have their own special requirements brought about by the need to predict performance in zero gravity by testing in earth gravity. vast majority of heat pipes manufactured today are conventional wicked circular cross-section units, there is an increasing trend towards miniaturization and the use of micro-groove type structures as wicks. The implications of these trends for manufacturing procedures are highlighted in this chapter.

Publisher Summary This chapter considers the gravitational field of the earth. The chapter mentions the forces acting on elementary volume of the rotating Earth in an inertial frame and considers the second Newton's law in non-inertial system. It introduces the centrifugal force and gravitational field, as well as its potential. Special attention is paid to the gravitational field and potential, caused by an ellipsoid of rotation and derives formulas for the gravitational field outside and at the surface of the rotating spheroid with an arbitrary value of flattening f, provided that this surface is equipotential. As is well known, the earth is mainly a fluid; the upper crust is an exception, but it is extremely thin layer with respect to the earth's radius. For this reason it is natural to expect that rotation around its axis makes the shape of the earth practically the same as if it was a fluid, and we will follow this conventional point of view.

Containerless processing is an effective tool for undercooling metallic melts far below their melting temperatures. The application of containerless processing techniques both in the Earth laboratory and in a space microgravity environment allows diagnostic access to the metastable state of an undercooled melt. This is demonstrated using laboratory results obtained by the electromagnetic levitation technique. The limitations for such experiments under Earth gravity are discussed and future prospects for containerless experiments under microgravity are described.

Publisher Summary This chapter describes artificial gravity as a countermeasure against the adverse effects of weightlessness. One of the goals of space medicine is to develop such countermeasures that would be, on the one hand, efficient and safe and, on the other hand, not encumbersome for crewmembers. Artificial gravity generated by spacecraft rotation may afford the best solution of the problem. From the biomedical point of view, the advantages and disadvantages of artificial gravity can well be understood only on the basis of the results of long-term space flights. In 1975, the studies on plants and lower vertebrates flown aboard the Soviet biosatellite Cosmos-782 showed that the biological effects of artificial gravity of 1 g generated by a centrifuge in a prolonged space flight were similar to those of earth gravity. The artificial gravity of 0.3 g proved sufficient to eliminate weightlessness-induced structural changes in the mitochondria and myofibers of cardiac and skeletal muscles of turtles.

Publisher Summary This chapter summarizes the concept of the gravity field. The rate of increase of the velocity is called the acceleration due to gravity or force of gravity. Gravity is the universal force of attraction between all masses. In 1665, Newton formulated the nature of this force from Kepler's laws on the motion of planets. He showed that gravity forces are proportional to the product of the masses involved and inversely proportional to the square of the distance between them. The direction of acceleration or force is everywhere normal to equipotential surfaces. Thus, the surface of a liquid at rest in a gravitational field will coincide with an equipotential surface. Instrumentation to measure the acceleration of the force of gravity may be naturally divided into two: one that measures absolute gravity and the other that measures the difference in gravity from one position to another or at a fixed position with time. Much useful information on the shape and internal mass distribution of the earth can be obtained from measurements of gravity differences, which are more convenient absolute gravity measurements.

The purpose of this introductory overview is to provide a possible guide for future LAF session activities in the general area of Earth and Ocean Dynamics, application satellites, ground systems, their necessary analytical tools and software. Some of these topics have been discussed in two previous IAF papers, but this is the first time that a serious and concentrated effort in this rather new area of space applications is to be made. The major potentials of these earth oriented Earth and Ocean Satellite and Systems objectives is in the area of “utilization” of space science and technology. This is to help and further geophysical exploration, earthquake hazard assessment, synoptic monitoring of the dynamics of the earth and oceans, the exploration of the polar ice regions and the refinements of the earth's gravitational and magnetic fields. These objectives have practical usage in such applications disciplines as protection of life and property, protection and prevention of disasters, exploration of mineral and energy resources, the shipping and fishing industry, coastal zone construction and off-shore drillings. It is evident that rather large economical benefits will result by achieving the above objectives. It is, however, very difficult at this time to determine a real monetary value for the benefits expected. Fortunately, some work has already been performed in the past years. Methods have developed, ground and flight systems have been constructed, operated and launched to satisfy at least some of the elements mentioned before. Geomagnetic spacecraft launched by the U. S. (OGOs) and the USSR (COSMOSs) have contributed to the construction of world magnetic field maps important for geologic studies. Other spacecraft, together with precision ground tracking systems (range and range rate, Doppler, LASER, Very Long Baseline Interferometer), have been used to develop rather sophisticated earth gravity models and geoids important to such applications as tectonic motion and earthquake studies, future global geophysical explorations and sea current studies. The Skylab and Nimbus missions contributed to the development of ocean surface wave and wind field models, sea surface temperature fields, ice fields and details of the ocean topography, to quote a few specific examples. The real intent of this paper is, as mentioned, to show one hand of some typical examples of how these applications objectives can be achieved. It is hoped that it will provide and act as a catalyst and driver for future IAF sessions to come in this area of space applications.

This chapter discusses the concept of motion on a rotating earth. The earth's rotation produces two effects on particles of the atmosphere. Both are the effects of inertia forces, because they are caused by the accelerations that the air undergoes. The first is the centrifugal force that causes the earth to be an oblate spheroid, and this is applied to all particles even when at rest relative to the ground. The second effect of the earth's rotation appears when particles begin to move over the earth's surface. The difference between gravity and apparent gravity accounts for the changes in velocity relative to the center of the earth. The remaining effect can, therefore, be represented as a rotation about an axis parallel to the earth's axis. The vertical motion in convection currents that produce cumulus clouds and the up-currents that occur in the neighborhood of mountains can be measured; but these motions occur on too small a scale for the earth's rotation to have any important effect because a particle of air passes through them in a small fraction of a day.

This chapter discusses centers of gravity and centroids. A solid body is made of a very large number of small bodies or particles; the earth attracts each one of these particles toward its center by the force of gravity. Each gravitational force is known as the weight of the particle. Because the earth is so large in comparison with any body, on it the radial lines of force attracting each particle to the earth's center can be regarded as parallel to each other. If all these tiny gravitational forces are added together, the total represents the weight of the body itself. In other words, the resultant of all the gravitational forces acting on the tiny particles is equal to the weight of the body. The resultant force is the one that produces the same effect as all these tiny gravitational forces acting together, and its line of action can be represented by the thick vertical line.

Publisher Summary This chapter discusses the ways in which gravitational attraction is utilized. It also summarizes the fundamental facts concerning the Earth's gravity field. Any measured value of gravity is a composite of many mass effects that includes the shape and size of the earth as a whole, the rotation of the earth, changes in elevation, horizontal mass discontinuities, and changes in topographic configuration. The largest and most easily measured changes in gravity are related to the change in shape of the earth. Therefore, these gravity measurements are an integral part of the geodetic program. Other geologic uses of gravity data include earth crystal studies, geological exploration, and gravity studies of the strength of the earth. With regard to national gravity base values, the principal difficulty in using gravity work, particularly for the study of the geoid, lies in getting all data on absolute datum. To eliminate confusion about the absolute gravity datum, the value determined at the Geodetic Institute at Potsdam is adopted by international agreement as a base value and all values are referred to it.