Zero-gravity environments

Suppose you are hired by NASA to examine the feasibility of developing chemical processing applications for the space station. What reactor and separation units would have to be abandoned, and what processes might be improved in a zero-gravity environment [Your first list will probably be much longer than your second, even before you consider transportation costs.1... 

In zero-gravity environments, human height increases by a few centimeters. This is because of the effects of reduced spinal curvature and the expansion of intervertebral discs in the back. The downside of this is lower back pain for astronauts. Lunar dust can pose pesky problems for astronauts working on the Moon. At sunrise and sunset, lunar dust tends to levitate and stick to surfaces. If lunar dust seeps into machinery, it can cause system failures, making this an important engineering concern for future lunar base builders. 

Gravity is negligible for sizes r < When this condition is met, it is as though the liquid is in a zero-gravity environment and capillary effects... 

In a zero-gravity environment, a sample of mercury has a spherical shape. Consider a sample that has a 1.000-cm radius. Determine how much work must be performed to separate the mercury into 10 equal spheres, assuming that the only work done is related to the change in surface energy. Recall that the surface area of a sphere is 4rrr and its volume is AlSirr. The surface tension of mercury is 435.5 erg/cm. ... 

Lilly s interest in the outer limits of human experience led him in the late 50s to invent the isolation tank, a coffin-like box in which one floats in warm water in a condition of silence, total darkness, and zero gravity. The aim of this invention was to provide a near-ideal environment for studying the human mind itself, removed from all outside influences. For a time his research in this area fell under the auspices of the National Institute of Mental Health in Bethesda, Maryland. Later his experiments with isolation loosely formed the basis for the popular book and movie Altered States. 

Such mirrors are capable to withstand stress imposed by launch and the space environment, including extreme and rapid temperature variations, high vacuum, zero gravity, vibration and shock. 

To determine precisely the flow relations that will exist in space, a complete duplication of the environment would be desirable, but this duplication is not possible for the type of tests needed. For example, the zero-gravity condition cannot, at present, be duplicated for a sufficient length of time to make flow measurements. 

Gravitis J, Abolins J, Kokorevics A. Integration of biorefinery clusters towards zero emissions. Environ Eng ManagJ 200S 7(105) S69-77. 

Thirsk, Robert, et al. The Space Flight Environment The International Space Station and Beyond. Canadian Medical Association Journal 180, no. 12 (June, 2009) 1216-1220. Discusses the basic science behind the effects of space travel and extended periods of time in zero-gravity on the human body and details specific risks to astronauts aboard the International Space Station. 

For the determination of a compound s chemical exergy value we need to define a reference environment. This reference environment is a reflection of our natural environment, the earth, and consists of components of the atmosphere, the oceans, and the earth s crust. If, at P0 and T0, the substances present in the atmosphere, the oceans, and the upper part of the crust of our earth are allowed to react with each other to the most stable state, the Gibbs energy of this whole system will have decreased to a minimum value. We can then define the value of the Gibbs energy for a subsystem, the "reference environment"—at sea level, at rest, and without other force fields present than the gravity field—to be zero as well as for each of the phases present under these conditions. It is a logical extension of these assumptions to... 

The /th species mass flux, j, and the total heat flux, q, can be expressed in terms of transfer coefficients. This is useful in situations where the liquid or gas phase is not completely resolved, or when the flow conditions are not exactly known. Often, these transfer coefficients are determined experimentally for a particular flow situation. For instance, different expressions are used, depending on whether the transfer is due to pure conduction or whether it is dominated by ccaivection. Also, the type of convection plays a role, that is, if the convection is forced or non-forced. A forced convection has a non-zero relative velocity between droplet and environment, whereas for a non-forced convection, the relative drop-gas velocity is zero and only the Stefan flow dominates. Note that the natural convection due to gravity is taken to be zero since gravity is an external force, and external forces are neglected in this article. In addition, in forced convection, the nature of the flow, that is, whether the flow is laminar or turbulent, plays an important role. These issues will be discussed in more detail in the following subsections. 

The gravity gradient and atmospheric drag account for the micro-g rather than zero-g time-averaged acceleration environment found in a q>acecraft. A q>acecraft in a low earth orbit is typically ut 300 kUometers above the earth s surface and about 6671 kilometers from ftie earth s center. It is int esting to note that r is onty about 5% greater in low earth orbit than on the earth s surfece. So the absolute value of A is only about 9% less in this orbit than on the ground... 

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