Click for next page ( 196

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 195
CGlossary agglutinates aggregates of pieces albedo the fraction of incident light that reflects diffusely from a surface aphelia the most distant points in solar orbits beneficiation process of transforming raw materials into more concentrated or beneficial forms bioreactor any system that is engineered to use biological agents for the transformation of one form of matter into another. This would include engineered composters, waste recovery systems, air purification systems using bio- logical agents, and fermenters used for producing antibiotics or other biological products. bioregenerative system system that makes use of metabolic processes in the conversion of waste to useful gases Brayton cycle a dynamic scheme for power generation featuring high conversion efficiency and a single-phase working fluid but with the drawback of relatively low heat-rejection temperatures, requiring relatively large and massive radiators capillarity the behavior of fluids under the influence of surface tension, such as the movement of water in a very small diameter tube, induced by the water' s ability to wet the walls of the tube cohesion the force that enables soil grains to cling together in opposition to the forces tending to separate soil into parts comminution reduction of a mass to minute particles or fine powder computational fluid dynamics (CFD) a numerical approach using high-speed computers for evaluating the conservation equations that describe single- and multiphase flows Coriolis force in a rotating system, a force proportional to the angular velocity and the velocity of any motion as measured in the rotating system 195

OCR for page 195
and other critical environmental parameters 196 cryogenics the study of the production of very low temperatures and their effects dead comets comet cores that no longer experience strong particle field interactions with the Sun duracrust a thin agglomerated soil layer that is observed at some locations on Mars dynamic equilibrium the balancing of forces on bodies in motion APPENDIX C ecological system the ensemble sustaining a life-support system, with special emphasis on the quality, nature, and analysis of interacting systems ejecta rocks and other solid debris thrown off the surface of a planetary body electrolysis the production of chemical changes in a chemical compound by causing its oppositely charged constituents, or ions, to move in opposite directions under a potential difference enabling technology a technology permitting the extension of human activity Eulerian formulation a mathematical model written in a fixed coordinate system excursive instabilities two-phase excursions from one operating state to another film bearing A bearing in which forces are transmitted through thin but continuous fluid films (gas or liquid) that separate solid machine components fines the silty sand regolith on the Moon with a median grain size of only 0.1 mm fractional gravity gravity levels lower than Earth' s but typical of those found on the surfaces of planets and their major satellites friction a force that opposes the sliding of one surface over another and whose magnitude is proportional to the normal force between the surfaces g-jitter (gravity-jitter) inertia effect due to oscillatory accelerations arising from crew motions, machinery, rocket firings, and so on, occurring in spacecraft gravity a body force per unit mass experienced as a result of mutual attraction with all other bodies, independent of electromagnetic or other forces heat exchanger device that facilitates the transfer of heat from a hot source to a cold sink heat pipe A container of two-phase fluid used to transfer heat efficiently heat sink A reservoir to absorb thermal energy homeostasis maintenance of constant values. for example for temperature. humidity, and gases in the atmosphere ' 1 1 ' hydrostatic pressure the equilibrium pressure acting at the base of a fluid which is proportional to the fluid's depth and gravity

OCR for page 195
APPENDIX C ilmenite FeTiO3, an oxygen-rich mineral found at moderate, but variable, concentrations on the Moon in situ resource utilization the production of useful materials from resources that are acquired and processed away from Earth's surface 197 interracial phenomena behavior, specially associated with boundaries between different phases, including those between similar phases of different materials Lagrangian formulation a mathematical model written in a coordinate system that is moving with the fluid Ledinegg instability an excursive instability in a boiling loop which may cause the flow to go to a new value, which in turn may result in the onset of critical heat flux liquid-phase sintering densification at the sintering temperature using a matrix of solid particles and a viscous liquid lunar magma molten lunar rock Marangoni effect liquid convection caused by surface tension gradients at the free surface of a liquid or at the interface between two liquids Marangoni flow movement of fluids under the influence of the Marangoni force Marangoni force a force exerted by the surface tension gradient multiphase used to describe any process involving a mixture of phases; a glass of ice water is a multiphase system near-net shape refers to shaped object that is in nearly the final desired shape and therefore requires only minimal . . mac fining normal stress the component of stress normal to a plane inscribed in a substance, tending to cause compressive or tensile strain in that normal plane, N/m2 penetrator a device used to penetrate beneath the surface of a planetary body phase a homogeneous and physically distinct state of aggregation of a substance, i.e., solid, liquid, or vapor phase phase separation separation of a mixture of phases into individual component phases physically based model a model of system behavior based on fundamental physical principles (e.g., thermody- namic laws) and the appropriate physical mechanisms (e.g., heat transfer, capillary flow), as opposed to an empirical model based primarily on experimental measurements and that incorporates only a limited theoretical understanding of the system physicochemical system system that makes use of a combination of physical and chemical processes power-to-mass ratio a characteristic of propulsion and other systems connoting the yield of power per unit of system mass, not including propellant mass

OCR for page 195
198 APPENDIX C pultrusion a process for producing continuous fibers for advanced composites that involves pulling reinforce- ments through tanks (of resins), a preformer, and a die radiation anything propagated as rays, waves, or a stream of particles, but especially light and other electromag- netic waves or the emission from radioactive substances Rankine cycle a dynamic method of power generation that uses separate boilers and condensers with two-phase (liquid/vapor) mixtures with high conversion efficiencies and high heat-rejection temperatures, allowing reduced radiator mass and areas reduced gravity gravity levels that are less than 1 go regolith surface rock, especially used to describe the lunar surface soil shear stress the component of stress parallel to a plane inscribed in a substance, tending to cause a shearing or slippage strain in that parallel plane, N/m2 slurry a mixture of a liquid and insoluble solids specific impulse thrust per unit mass of flow rate produced by burning rocket propellant at the rate of one pound per second, in seconds static equilibrium the balancing of forces on bodies at rest substoichiometric in chemical reactions, the participation of one species in less-than-exact chemical equivalence with other reacting species surface tension attractive forces at a liquid surface that cause the surface to contract as far as possible technical readiness level the maturity of a system, ranging from level 1 (a basic principle observed and re- ported) to level 8 (a design qualified for spaceflight) touch-and-go exploration round-trip space missions of the Apollo type, which are characterized by relatively short surface stays triple point the point on a pressure-temperature diagram representing the condition at which the solid, liquid, and vapor phases can exist together in equilibrium Van der Waals force attractive intermolecular force arising from induced dipole moment viscosity the property of fluids by virtue of which they offer a resistance to flow volatiles molecules that can exist in a gaseous phase on Earth's surface volatilization conversion to a gaseous or vapor phase water gas historical designation of a gaseous fuel produced by reacting steam with very hot solid carbon