Surveyor V: Lunar Surface Mechanical Properties

Christensen, E. M.; Choate, R.; Jaffe, L. D.; Spencer, R. L.; Sperling, F. B.; Batterson, S. A.; Benson, H. E.; Hutton, R. E.; Jones, Rebecca H.; Ko, Hon‐Yim; Schmidt, F. N.; Scott, Ronald F.; Sutton, George H.

doi:10.1126/science.158.3801.637

Cited by 18 publications

(4 citation statements)

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“…The resistivity p can be calculated from a knowledge of noconstriction resistance as follows: p = AR Q /L ( 4 6 ) where L is the distance between the voltmeter probes, Substituting Eqs. (44) and (46) in (45), the conductance number becomes…”

Section: Methodsmentioning

confidence: 99%

Thermal Design Principles of Spacecraft and Entry Bodies

1969

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PREFACE 4 environment in the present case is much more demanding, and the reliability requirements for our present technology are much more severe than in the case of the environmental control technology of old.To illustrate the severity of the problems of today's thermophysics, let us consider the elements of the thermal design of a spacecraft, either manned or unmanned. We have a deep thermal sink surrounding the spacecraft at temperatures of 4°K (outer space) and, at the same time, a continuous strong flux of radiant energy, the density of which unfortunately is not uniform but varies as the inverse square of the distance from the sun. This complicates the regulation problem for an interplanetary mission. Inside the spacecraft we have sensitive components (including man) which must be maintained within rather narrow temperature limits over wide ranges of operational duty cycles and internal power dissipations. We therefore must establish and control the thermal balance between the external sources and sinks and the internal sources and sinks. We can do this in several ways as, for example, by the use of thermal coatings to balance absorbed and internally generated power with the emitted power, by the operation of mechanical devices, such as louvers, to vary the effective absorbed and emitted power as a function of the internal temperature, and by means of internal convective loops and space radiators, if necessary.However, the design process is always constrained by severe weight restrictions, difficult mission requirements, and the need for compatibility with the other subsystems, such as the propulsion assembly. Further complications in the selection of the materials and/or the methods used to achieve thermal control arise from the adverse environment of space (vacuum, ultraviolet radiation, charged particles, and micrometeorites). These environmental factors, together or singly, can degrade the thermal control coatings used, affect the mechanical devices employed, puncture the fluid passages in the radiators, or otherwise interfere with the thermal control system.All of this illustrates the severity of the thermal control problem. Yet, despite the unavoidable complexity, our system must attain a reliability far beyond anything ever expected of the older environmental control technology. Spacecraft with lifetimes in excess of five years are required for commercial communication systems, and, in the case of manned spacecraft, the reliability is required to approach perfection.

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Section: Methodsmentioning

confidence: 99%

Thermal Design Principles of Spacecraft and Entry Bodies

1969

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“…The detrimental effects of PSI from previous lunar and martian missions are well documented (Christensen et al, 1967;Foreman, 1967;O'Brien et al, 1970;Clark, 1970;Jaffe, 1971;Taylor, 1972;Hutton et al, 1980;O'Brien, 2009;Gómez-Elvira et al, 2014). In fact, four of the six Apollo landings suffered from hindered visibility caused by ejected granular material during landing.…”

Section: Impact Of Psi From Previous Landingsmentioning

confidence: 99%

Modeling high-speed gas-particle flows relevant to spacecraft landings: A review and perspectives

Capecelatro

2021

Preprint

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The interactions between rocket exhaust plumes and the surface of extraterrestrial bodies during spacecraft landings involve complex multiphase flow dynamics that pose significant risk to space exploration missions. The two-phase flow is characterized by high Reynolds and Mach number conditions with particle concentrations ranging from dilute to close-packing. Low atmospheric pressure and gravity typically encountered in landing environments combined with reduced optical access by the granular material pose significant challenges for experimental investigations. Consequently, numerical modeling is expected to play an increasingly important role for future missions. This article presents a review and perspectives on modeling high-speed disperse two-phase flows relevant to plume-surface interactions (PSI). We present an overview of existing drag laws, with origins from 18th-century cannon fire experiments and new insights from particle-resolved numerical simulations. While the focus here is on multiphase flows relevant to PSI, much of the same physics are shared by other compressible gas-particle flows, such as coal-dust explosions, volcanic eruptions, and detonation of solid material.

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“…However, DGE may have occurred at least one time during the Surveyor V mission when the vernier engines were fired as a test after landing. 5 There were some large blasts of soil in the final moments of some landings (particularly Apollo 15), 22 which may have been due to enhanced viscous scouring at low altitude or the removal of soil mechanically fractured by the lander's contact probes. A plume-induced crater of approximately 444 liters volume was noted by the Apollo 14 crew.…”

Section: Lunar Plume Effectsmentioning

confidence: 99%

“…The interaction of exhaust plumes with loose regolith material was first studied in the era leading up to the Apollo [3][4][5][6][7][8][9][10][11] and Viking [12][13][14][15][16][17] programs and again more recently. [18][19][20][21][22][23][24][25][26] There are several different flow regimes in the interaction between gas and granular media, and so the type of damage that could occur in a particular mission depends upon which flow regime is induced by the specifics of the propulsion system and the planetary environment.…”

Section: Introductionmentioning

confidence: 99%

ISRU Implications for Lunar and Martian Plume Effects

Metzger¹,

Immer

et al. 2009

47th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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Experiments, analyses, and simulations have shown that the engine exhaust plume of a Mars lander large enough for human spaceflight will create a deep crater in the martian soil, blowing ejecta to approximately 1 km distance, damaging the bottom of the lander with high-momentum rock impacts, and possibly tilting the lander as the excavated hole collapses to become a broad residual crater upon engine cutoff. Because of this, we deem that we will not have adequate safety margins to land humans on Mars unless we robotically stabilize the soil to form in situ landing pads prior to the mission. It will take a significant amount of time working in a harsh off-planet environment to develop and certify the new technologies and procedures for in situ landing pad construction. The only place to reasonably accomplish this is on the Moon. Nomenclature a = acceleration CD = coefficient of drag Kn = Knudsen number Re = Reynolds number v = velocity Δt = time step

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Surveyor V: Lunar Surface Mechanical Properties

Cited by 18 publications

References 1 publication

Thermal Design Principles of Spacecraft and Entry Bodies

Thermal Design Principles of Spacecraft and Entry Bodies

Modeling high-speed gas-particle flows relevant to spacecraft landings: A review and perspectives

ISRU Implications for Lunar and Martian Plume Effects

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