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  • 1
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    Degradation of Coflon in Methanol at Temperatures Around 140 C (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An unexpected and significant physico-chemical degradation of Coflon PVDF specimens was observed at the end of 1994 during routine scheduled exposure exercises on strained material. The intent was to age various samples, including some strained in a 4-point bend configuration, in methanol at 140 C and subsequently submit the aged samples to various tests including dynamic fatigue and fracture toughness. However, the samples deteriorated to such an extent that such testing was not possible: only when conditions were made less severe was it found possible to perform such testing. The purpose of the current report is to describe the nature of the PVDF deterioration observed during a number of tests performed to examine this phenomenon. This report also records, as Appendix 1, some SEM/X-ray microanalysis data on Coflon samples exposed to a methanol/amine mixture, and to other amine or H2S-aged samples.
    Keywords: Nonmetallic Materials
    Type: NASA/CR-95-207623 , NAS 1.26:207623 , CAPP/M.6
    Format: application/pdf
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  • 2
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    Workpiece positioning vise (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A pair of jaw assemblies simultaneously driven in opposed reciprocation by a single shaft has oppositely threaded sections to automatically center delicate or brittle workpieces such as lithium fluoride crystal beneath the blade of a crystal cleaving machine. Both jaw assemblies are suspended above the vise bed by a pair of parallel guide shafts attached to the vise bed. Linear rolling bearings, fitted around the guide shafts and firmly held by opposite ends of the jaw assemblies, provide rolling friction between the guide shafts and the jaw assemblies. A belleville washer at one end of the drive shaft and thrust bearings at both drive shaft ends hold the shaft in compression between the vise bed, thereby preventing wobble of the jaw assemblies due to wear between the shaft and vise bed.
    Keywords: MECHANICAL ENGINEERING
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    NASA TECHNICAL REPORTS
  • 3
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    A life test of a 22-Newton (5-lbf) hydrazine rocket (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Life tests were conducted on a 22-N (5-lb) hydrazine rocket thruster which incorporates the latest technology to obtain long life from the catalyst bed. A spring mechanism surrounding the catalyst bed continually applies compression to the catalyst bed to prevent the formation of any void channels. The research rocket thruster was tested over an operational cycle of both steady state and pulse firing which simulated a possible space station duty cycle. The thruster ran as expected for about 40 hours, or 3.2 times 10 to the 6th power N-sec (7.2 times 10 to the 5th power lb-sec) total impulse. Subsequently, some thrust chamber pressure decreases were noted during long steady state test periods. After 60.2 hours of run time, tests had to be terminated due to a blockage in the propellant injector tube which occurred during heating of the thruster by a heat lamp. A chemical analysis of the catalyst indicated that iron and nickel metals had poisoned some of the catalyst, thereby causing a degradation in performance. It was determined that a contaminated barrel of hydrazine was the source of the metal poisoning.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-100232 , E-3857 , NAS 1.15:100232
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  • 4
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    Cosmic ray exposure ages of features and events at the Apollo landing sites (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Cosmic-ray exposure ages of lunar samples have been used to date surface features related to impact cratering and downslope movement of material. Only when multiple samples related to a feature have the same rare-gas exposure age or when a single sample has the same Kr-81 -Kr and track-exposure age can a feature be considered as reliably dated. Based on these criteria, there are only five well-dated lunar features: Cone Crater (Apollo 14), 26 m.y,; North Ray Crater (Apollo 16), 50 m.y.; South Ray Crater (Apollo 16), 2 m.y.; the emplacement of the Station 6 boulders (Apollo 17), 22 m.y.; and the emplacement of the Station 7 boulder (Apollo 17), 28 m.y. Other features are tentatively dated or have limits set on their ages: Bench Crater (Apollo 12), upper limit of 99 m.y.; Baby Ray Crater (Apollo 16), upper limit of 2 m.y.; Shorty Crater (Apollo 17), approximately 30 m.y.; Camelot Crater (Apollo 17) upper limit of 140 m.y.; the emplacement of the Station 2 boulder 1 (Apollo 17), 45 to 55 m.y.; and the slide which generated the light mantle (Apollo 17), lower limit of 50 m.y.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Format: text
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  • 5
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    Horizontal transport of the regolith, modification of features, and erosion rates on the lunar surface (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Impact-ejecta systematics are developed for the smaller cratering events which, with cumulative crater populations observed in young mare regions and on Copernicus ejecta fields, yield rates and a range distribution for the horizontal transport of material by impact processes. The deposition rate for material originating more than 1 m away is found to be about 8 mm per million years. Material from 10 km away accumulates at a rate of about 0.08 mm per million years, providing a steady influx of foreign material. From the degradation of boulder tracks, a rate of 5 plus or minus 3 cm per million years is computed for the filling of shallow lunar depressions on slopes. Mass wastage and downslope movement of bedrock outcroppings on Hadley Rille seem to be proceeding at a rate of about 8 mm per million years. The Camelot profile is suggestive of a secondary impact feature.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 6
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    Mechanical absorption of acoustic oscillations in simulated rocket combustion chambers (1967)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Mechanical absorption of acoustic oscillations in simulated rocket combustion chambers
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-TN-D-3792
    Format: application/pdf
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  • 7
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    Cosmic-ray exposure history at the Apollo 16 and other lunar sites - Lunar surface dynamics (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Concordant Kr-81/Kr exposure ages for four station 11 breccias indicate an age of 50.3 plus or minus 0.8 m.y. for North Ray Crater. Ray structures visible from orbital photography suggest that stations 8 and 9 should contain a substantial amount of South Ray ejecta. Concordant Kr-81/Kr exposure ages at these sites indicate an age for South Ray Crater of 2.04 plus or minus 0.08 m.y. Surface effects show good general agreement with this young age, but discrepancies on a sample-by-sample basis seem to indicate that extensive presurface irradiations must have occurred.
    Keywords: SPACE RADIATION
    Type: Geochimica et Cosmochimica Acta; 38; Oct. 197
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  • 8
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    The Effect of Resistance on Rocket Injector Acoustics (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Combustion instability, where unsteady heat release couples with acoustic modes, has long been an area of concern in liquid rocket engines. Accurate modeling of the acoustic normal modes of the combustion chamber is important to understanding and preventing combustion instability. This study evaluates the effect of injector resistance on the mode shapes and complex eigen-frequencies of an injector/combustion chamber system by defining a high Mach-flow form of the convective wave equation (see Eq. 1) in COMSOL Multiphysics' Coefficient Form PDE Mathematics Module.
    Keywords: Fluid Mechanics and Thermodynamics; Numerical Analysis
    Type: M15-4797 , COMSOL Conference 2015; Oct 07, 2015 - Oct 09, 2015; Boston, MA; United States
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  • 9
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    Cosmic-ray exposure history at Taurus-Littrow (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Recent surface history at Taurus-Littrow is dominated by emplacement of the Central Cluster and Bright Mantle morphological units, both believed to have resulted from arrival of ejecta from a large primary crater, probably Tycho. This paper reports new noble gas data for eight Apollo 17 rocks. Kr-81 - Kr cosmic ray exposure ages for these rocks affirm the observation of a pronounced grouping of ages, reinforcing the photogeologic evidence for the site-wide nature of the Central Cluster event. The consequences of post-cratering shielding changes are considered and it is concluded that the differences can reasonably be attributed to these changes, particularly because of the greater likelihood of rollover and impact fragmentation of the relatively smaller rocks from which most age data have been obtained. These considerations also lead to a more refined age estimate of 109 plus or minus 4 m.y. for Central Cluster, the Bright Mantle, and Tycho.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 10
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    The regolith history of 14307 (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Noble gas and trace element analyses of matrix and a clast from breccia 14307 are reported. This sample was exposed to a large neutron fluence, as seen by an elevated Sm-150/Sm-149 ratio and by noble gases, particularly Xe-136 from neutron fission of U-235. Strong constraints on the exposure history result from combined consideration of Sm-150, Xe-136, and spallation noble gases. Both clast and matrix were irradiated for about 1 AE under substantial shielding beginning at least 2 AE ago, probably more than 3 AE ago. The manifestations of soil exposure seen in the matrix - solar wind gases, glass formation, etc. - thus must have been acquired in an ancient epoch. The matrix has had a longer exposure to cosmic rays than the clast, presumably during its prebrecciation history as a soil. Brecciation probably occurred more than 1 AE ago, perhaps more than 3 AE ago, but at least 0.4 AE after the formation of the matrix constituents.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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