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  • 1
    Publication Date: 2004-08-01
    Print ISSN: 0882-8156
    Electronic ISSN: 1520-0434
    Topics: Geography , Physics
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  • 2
    Publication Date: 2019-07-13
    Description: Apollo landing videos shot from inside the right LEM window, provide a quantitative measure of the characteristics and dynamics of the ejecta spray of lunar regolith particles beneath the Lander during the final 10 [m] or so of descent. Photogrammetry analysis gives an estimate of the thickness of the dust layer and angle of trajectory. In addition, Apollo landing video analysis divulges valuable information on the regolith ejecta interactions with lunar surface topography. For example, dense dust streaks are seen to originate at the outer rims of craters within a critical radius of the Lander during descent. The primary intent of this work was to develop a mathematical model and software implementation for the trajectory simulation of lunar dust particles acted on by gas jets originating from the nozzle of a lunar Lander, where the particle sizes typically range from 10 micron to 500 micron. The high temperature, supersonic jet of gas that is exhausted from a rocket engine can propel dust, soil, gravel, as well as small rocks to high velocities. The lunar vacuum allows ejected particles to travel great distances unimpeded, and in the case of smaller particles, escape velocities may be reached. The particle size distributions and kinetic energies of ejected particles can lead to damage to the landing spacecraft or to other hardware that has previously been deployed in the vicinity. Thus the primary motivation behind this work is to seek a better understanding for the purpose of modeling and predicting the behavior of regolith dust particle trajectories during powered rocket descent and ascent.
    Keywords: Lunar and Planetary Science and Exploration
    Type: KSC-2008-019 , 11th Biennial ASCE Aerospace Division International Conference on Engineering, Construction and Operations in Challenging Environments; Mar 03, 2008 - Mar 05, 2008; Long Beach, CA; United States
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  • 3
    Publication Date: 2019-07-13
    Description: Roberts' model of lunar soil erosion beneath a landing rocket has been updated in several ways to predict the effects of future lunar landings. The model predicts, among other things, the number of divots that would result on surrounding hardware due to the impact of high velocity particulates, the amount and depth of surface material removed, the volume of ejected soil, its velocity, and the distance the particles travel on the Moon. The results are compared against measured results from the Apollo program and predictions are made for mitigating the spray around a future lunar outpost.
    Keywords: Lunar and Planetary Science and Exploration
    Type: KSC-2008-020 , 11th Biennial ASCE Aerospace Division International Conference (Earth and Space 2008); Mar 03, 2008 - Mar 06, 2008; Long Beach, CA; United States
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  • 4
    Publication Date: 2019-07-13
    Description: Several physical mechanisms are involved in excavating granular materials beneath a vertical jet of gas. These occur, for example, beneath the exhaust plume of a rocket landing on the soil of the Moon or Mars. A series of experiments and simulations have been performed to provide a detailed view of the complex gas/soil interactions. Measurements have also been taken from the Apollo lunar landing videos and from photographs of the resulting terrain, and these help to demonstrate how the interactions extrapolate into the lunar environment. It is important to understand these processes at a fundamental level to support the ongoing design of higher-fidelity numerical simulations and larger-scale experiments. These are needed to enable future lunar exploration wherein multiple hardware assets will be placed on the Moon within short distances of one another. The high-velocity spray of soil from landing spacecraft must be accurately predicted and controlled lest it erosively damage the surrounding hardware.
    Keywords: Lunar and Planetary Science and Exploration
    Type: KSC-2007-064 , 18th Engineering Mechanics Division Conference (EMD2007); Jun 03, 2007 - Jun 06, 2007; Blacksburg, VA; United States
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  • 5
    Publication Date: 2019-07-13
    Description: In preparation for the Apollo program, Leonard Roberts developed a remarkable analytical theory that predicts the blowing of lunar soil and dust beneath a rocket exhaust plume. Roberts' assumed that the erosion rate is determined by the "excess shear stress" in the gas (the amount of shear stress greater than what causes grains to roll). The acceleration of particles to their final velocity in the gas consumed a portion of the shear stress. The erosion rate continues to increase until the excess shear stress is exactly consumed, thus determining the erosion rate. He calculated the largest and smallest particles that could be eroded based on forces at the particle scale, but the erosion rate equation assumes that only one particle size exists in the soil. He assumed that particle ejection angles are determined entirely by the shape of the terrain, which acts like a ballistic ramp, the particle aerodynamics being negligible. The predicted erosion rate and particle upper size limit appeared to be within an order of magnitude of small-scale terrestrial experiments, but could not be tested more quantitatively at the time. The lower particle size limit and ejection angle predictions were not tested.
    Keywords: Lunar and Planetary Science and Exploration
    Type: KSC-2007-195 , Earth and Space 2008; Mar 03, 2008 - Mar 05, 2008; Long Beach, CA; United States
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  • 6
    Publication Date: 2019-07-12
    Description: Analytic expressions for the magnetic induction (magnetic flux density, B) of a simple planar circular current loop have been published in Cartesian and cylindrical coordinates [1,2], and are also known implicitly in spherical coordinates [3]. In this paper, we present explicit analytic expressions for B and its spatial derivatives in Cartesian, cylindrical, and spherical coordinates for a filamentary current loop. These results were obtained with extensive use of Mathematica "TM" and are exact throughout all space outside of the conductor. The field expressions reduce to the well-known limiting cases and satisfy V B = 0 and V x B = 0 outside the conductor. These results are general and applicable to any model using filamentary circular current loops. Solenoids of arbitrary size may be easily modeled by approximating the total magnetic induction as the sum of those for the individual loops. The inclusion of the spatial derivatives expands their utility to magnetohydrodynamics where the derivatives are required. The equations can be coded into any high-level programming language. It is necessary to numerically evaluate complete elliptic integrals of the first and second kind, but this capability is now available with most programming packages.
    Keywords: Physics (General)
    Type: NASA/TM-2013-217919
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  • 7
    Publication Date: 2019-07-12
    Description: The pumping of liquid oxygen (LOX) by magnetic fields (B field), using an array of electromagnets, is a current topic of research and development at Kennedy Space Center, FL. Oxygen is paramagnetic so that LOX, like a ferrofluid, can be forced in the direction of a B field gradient. It is well known that liquid oxygen has a sufficient magnetic susceptibility that a strong magnetic gradient can lift it in the earth's gravitational field. It has been proposed that this phenomenon can be utilized in transporting (i.e., pumping) LOX not only on earth, but on Mars and in the weightlessness of space. In order to design and evaluate such a magnetic pumping system, it is essential to compute the magnetic and force fields, as well as inductance, of various types of electromagnets (solenoids). In this application, it is assumed that the solenoids are air wrapped, and that the current is essentially time independent.
    Keywords: Physics (General)
    Type: NASA/TM-2013-217918
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  • 8
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Lunar and Planetary Science and Exploration
    Type: KSC-2006-060 , World Congress of Particle Technology; Apr 24, 2006 - Apr 27, 2006; Orlando, FL; United States
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  • 9
    Publication Date: 2019-07-13
    Description: There are many situations in nature and technology where particulate matter is excavated by a fluid jet. Such a process is often used to excavate soil or to dig wells. Air jets are often used to transport particulate matter such as powders in various industrial processes. Similar situations occur in nature, as when waterfalls scour holes in sand. In other cases, the excavation is unwanted such as when a rocket lands on the sandy or dusty surface of a planet or moon. Recent research into regolith excavation by gas jets has obtained new insights into the physical processes of that excavation, and these may lead to new advances in technology for more efficient fluid-jet excavation processes and for better control of the unwanted excavation effects of landing rockets. This talk will explain the new insights and point to future work supporting lunar exploration.
    Keywords: Lunar and Planetary Science and Exploration
    Type: KSC-2006-094 , KSC-2006-165 , KSC-2006-061 , Planetary and Terrestrial Mining Sciences Symposium; Jun 04, 2006 - Jun 07, 2006; Sudbury, Ontario; Canada
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  • 10
    Publication Date: 2019-07-13
    Description: When launching or landing a space craft on the regolith of a terrestrial surface, special attention needs to be paid to the rocket exhaust cratering effects. If the effects are not controlled, the rocket cratering could damage the spacecraft or other surrounding hardware. The cratering effects of a rocket landing on a planet's surface are not understood well, especially for the lunar case with the plume expanding in vacuum. As a result, the blast effects cannot be estimated sufficiently using analytical theories. It is necessary to develop physics-based simulation tools in order to calculate mission-essential parameters. In this work we test out the scaling laws of the physics in regard to growth rate of the crater depth. This will provide the physical insight necessary to begin the physics-based modeling.
    Keywords: Lunar and Planetary Science and Exploration
    Type: KSC-2005-162 , 56th International Astronautical Congress; Oct 17, 2005 - Oct 21, 2005; Fukuoka; Japan
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