Recapturing a Future for Space Exploration Life and Physical Sciences Research for a New Era (2011) / Chapter Skim
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9 Applied Physical Sciences
9 Applied Physical Sciences
Pages 265-298
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From page 265... ...
For example, multiphase flow regimes and the performance of heat transfer phase-change systems on Earth are very different than they are in the absence of gravity. Flame ignition, propagation, and quenching are also affected by gravity.
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Areas of particular interest are reduced-gravity multiphase flows, cryogenics, and heat transfer: database and modeling; interfacial flows and phenomena; dynamic granular material behavior; granular subsurface geotechnics; dust mitigation; and fundamental research in complex fluid physics. Each of these fields encompasses a myriad of individual phenomena.
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From page 267... ...
Key fluid physics issues include reduced-gravity multiphase flow, cryogenics and heat transfer, interfacial flows† and phenomena, dynamic granular material behavior, granular subsurface geotechnics, dust mitigation, and complex fluid physics. Research into all of these issues is uniquely enabled by NASA reduced-gravity facilities.
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From page 268... ...
24,25 Research in Support of NASA's Exploration Missions Reduced-Gravity Multiphase Flows, Cryogenics, and Heat Transfer: Database and Modeling In reduced gravity, the limitations on the empirically based predictive methods used on Earth for relatively high-speed multiphase flows do not allow NASA to exploit the advantages of using multiphase technology in space. This is because there is essentially no reliable database for flow regimes, void fraction, two-phase pressure drop, and wall heat transfer in reduced gravity.
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From page 269... ...
; they should be capable of accurately scaling up so that they can be used to design and analyze hardware of interest on NASA's spacecraft and extraterrestrial habitats. Physically based, three-dimensional, twofluid models of multiphase flow and heat transfer have been developed by rigorously averaging the Navier-Stokes equations of fluid mechanics and the associated mass and energy conservation equations.
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From page 270... ...
at the contact line in a horizontal conduit leads to a remarkable stratified-to-annular flow regime change when going from Earth gravity to reduced gravity.46 Thus, DNS or molecular simulations can also provide the insight needed to develop accurate three-dimensional multiscale CMFD models that are much more numerically efficient than DNS or molecular simulations and yet capture the same phenomena. This Grand Challenge type of research and development approach is consistent with the recommendations in previous NRC studies 47 and past international workshops on scientific issues in multiphase flow and heat transfer.
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The transient three-dimensional CMFD models previously discussed can be used for this purpose, but it appears that simpler, one-dimensional drift-flux models may be sufficient.56 Other flow-stability problems that warrant further investigation include the following: freeze-thaw cycles, flow excursions, system start-up transients, and cross-contamination. Dynamic Granular Material Behavior During the landing and launching of a spacecraft, its rocket exhaust directly interacts with the regolith, caus ing a spray of material that can damage the spacecraft or nearby structures and reduce visibility.
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Surface electric fields cause dust to adhere to objects and drive dust transport, yet this process is poorly understood. Fundamental Research in Complex Fluid Physics As noted in Chapter 8, complex fluids are excellent candidates for study in reduced gravity.
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Reduced-Gravity Multiphase Flows, Cryogenics, and Heat Transfer: Database and Modeling A detailed reduced-gravity database is essential for the development and assessment of reliable models for multiphase flow and heat transfer, but very little data is currently available. These data should include phase sepa ration and distribution (i.e., flow regimes)
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From page 274... ...
Research in this area should support the development of the critical technologies described in Chapter 10 that are listed in the section above titled "Reduced-Gravity Multiphase Flows, Cryogenics, and Heat-Transfer: Database and Modeling." Dynamic Granular Material Behavior and Granular Subsurface Geotechnics Improved predictive capabilities related to the behavior of lunar and martian soils on the surface and at depth would enable advanced human and robotic planetary surface exploration and habitation. Surface operations such as wheel/track-soil interaction and cratering would benefit from the development of particle-scale and multiscale models and simulations of key dynamic interactions with soil, including the crushing and compaction of agglu tinates.
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Research in Support of NASA's Exploration Missions Combustion research in support of NASA's exploration missions is addressed in Chapter 10, "Translation to Space Exploration Systems." Fundamental Combustion Research This section focuses on gravity-related combustion research issues of most crucial importance to NASA's future crewed and uncrewed missions. In particular, NASA should support fundamental combustion research in fire safety and combustion processes.
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. 87,88 The most effective fire suppression agents and deployment methods have yet to be determined for specific space applications.
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Data from reduced-gravity experiments, when combined with theory and computations, have "contributed to our fundamental knowledge of some of the most basic combustion phenomena, to the improvement of fire safety on present and future space missions, and to the advancement of knowledge about some of the most important practical problems in combustion on Earth."94 These results include the discovery of new phenomena that challenged previous theories and demonstrated the actual behavior of previously proposed combustion states. The existence of theoretically predicted flame balls has been revealed, and their persistence and stability in reduced gravity have been demonstrated.
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103,104 Solid Combustion and Smoldering Gas-phase combustion from a solid fuel produces a special type of diffusion flame that is profoundly affected by gravity. Smoldering has many applications in material synthesis, but it is mostly encountered as a fire safety
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Recommended Research in Combustion Recommended research in combustion is summarized below and in Table 9.1 toward the end of this chapter. Fire Safety Improved methods for screening materials in terms of flammability in space environments will enable safer space missions.
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. Numerical Simulation of Combustion Numerical models are powerful and necessary tools for studying combustion processes in reduced gravity, including issues related to fire safety in spacecraft.
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An example of a new, unique property is self-healing capabilities after a meteoroid impact. Materials Synthesis and Processing Improvements to existing synthesis processes and the development of new processes are needed for the groundbased synthesis of a wide range of enabling materials, both traditional and advanced, for space exploration and for materials repair and production during missions.
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a damaged structure. A vast array of smart materials can be employed in a variety of ways that will enable new space exploration capabilities.
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Much of the current research on fuel cells is very diverse in regard to the materials being investigated. Many of these systems may be applicable to space exploration missions, but the specific characteristics required for the rigors of space travel are not at present being investigated.135 System performance at low temperatures and pressures should be studied in greater depth in order to produce a fuel cell capable of operating efficiently in the vacuum of space.
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These uniform poros ity structures have several important applications for space exploration that range from gas and liquid filters and separation membranes to drug delivery systems for astronauts. Microstructure and Property Control Microstructures are central to properties of materials as diverse as nanoscale precipitates in aluminum alloys and single-crystal turbine blades.
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: inflatable aerodynamic decelerators, space nuclear propulsion, fission surface power, and radiation protection systems. In Situ Resource Utilization There is a strategic and critical need to utilize extraterrestrial resources for future space exploration and thereby extend human space exploration capabilities.
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The recommended high-priority research areas in applied physical sciences are listed below and in Table 9.1, which also lists current gaps, the specific research recommendations that cover a 20-year period, and the expected research outcomes. Fluid Physics Recommendations • Reduced-gravity multiphase flows, cryogenics, and heat transfer: database and modeling -- NASA should create a detailed reduced-gravity database that includes phase separation and distribution (i.e., flow regimes)
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(AP9) • Advanced materials -- NASA should support research to develop new and advanced materials that would enable operations in increasingly harsh space environments and reduce the cost of human exploration.
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(AP1) a change heat transfer computational in situ resource utilization (e.g., boiling and multiphase fluid (ISRU)
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accumulation exists. Many important -- Conduct fundamental Continue relevant A better understanding of Complex fluid physics: Utilization of microgravity experiments on the research on the ISS.
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(AP6) Incomplete knowledge Complete droplet-phase, Conduct larger-scale, Deeper understanding of Combustion processes: Combustion of basic processes gas-phase, and solid longer-duration fundamental combustion experiments in reduced and their response to experiments on the experiments.
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(AP11) that enables space exploration and can be manufactured from extraterrestrial resources in both normal and reduced gravity.
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2000. Microgravity Research in Support of Technologies for the Human Exploration and Development of Space and Planetary Bodies.
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2001. Numerical simulations of pool boiling heat transfer.
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2000. Microgravity Research in Support of Technologies for the Human Exploration and Development of Space and Planetary Bodies.
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Fire Safety Journal 32:61-88.
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1985. Implementing supercritical water oxidation technology in a lunar base environmental control/life support system.
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and in-situ resource utilization (ISRU)
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