C l a s s i f i e d a b s t r a c t s 1502-1513 ncnts at vacuum levels in the IO ~ to 10-D torr range. The pumping system and liquid-nitrogen-cooled shrouds are also described. A C Spagnuolo, Rep NASA-TM-X-1503, Feb 1968, 18 pages (Sci Tech Aerospace Reps, 6 (7), 982, N68-16695). 34 : 37 1502. Experimental investigation of ultrahigh vacuum adhesion as related to the lunar surface. (USA) Studies were concerned with (1) modifications of the experimental apparatus to permit study of the adhesional behaviour of ultrahigh vacuum cleaved silicates, in contact with metals of various surface state, and (2) construction of a second vacuum system to permit direct measurement of the magnitude and distribution of electrostatic surface charging produced during cleavage. The modifications consist of installation of apparatus to permit argon ion sputtering and mechanical abrasion of the metal surfaces. The second vacuum system contains an adjustable electrometer probe with associated electronics and recording equipment. The experiments demonstrated that vacuum cleavage of silicates does produce considerable surface charging, that this charging is macroscopically anisotropic, and that it persists over extended periods of time. J A R y a n and J J Grossman, Rep NASA-CR-92689; Jan 1968, 31 pages (Sci Tech Aerospace Reps, 6 (7), 982, N68-16826). 34 1503. Stability of thermal control coatings exposed to combined space environments. (USA) An in situ reflectometer system was designed, and installed in an existing space simulation facility. Tests were conducted on twelve materials, including combined environment of vacuum, protons and ultraviolet. Results of these studies are given. W R Holland, Rep NASA-CR-73160, Dec 1967, 111 pages (Sci T e c h Aerospace Reps, 6 (7), 1099, N68-16904). 34 : 28 1504. Accurate surface temperature measurements at liquid helium conditions in space environment facilities. (USA) An accurate temperature sensor, consisting of a germanium resistance thermometer, a lead-wire heat sink, and a high thermal conducting epoxy fastening method is available for measuring wall temperatures
of large liquid helium cooled space environment facilities. A high thermal conductivity epoxy minimizes the vacuum thermal contact resistance between the sensor envelope and the wall. J F Cassidy and W M Krawezonek, Rep NASA-TM-X-52386, 1968, 21 pages (Sci Tech Aerospace Reps, 6 (7), 1099, N68-17044). 34 : 24 1505. Study of propellant valve leakage in a vacuum. (USA) Results are presented of an investigation of the adverse effects of leakage through propellant valves into injector flow passages and combustion chambers, which are exposed to a vacuum environment, Leakage conditions are defined theoretically and confirmed experimentally, R D Gift et al, Rep NASA-CR-62046, 1967, 247 pages (Sci Tech Aerospace Reps, 6 (8), 1230, N68-17431). 34 : 18 1506. Discharge chamber studies for mercury bombardment ion thrnstors. (USA) Effects on the discharge properties of the magnetic field configuration, the cathode location and type, and the method of propellant introduction were studied in relation to mercury bombardment ion thrusters. W Knauer and P Poeschel, Rep NASA-CR-72350, 1967, 60pages (Sci Tech Aerospace Reps, 6 (8), 1232, N68-18136).
1508. Infuence of temperature on the pyrolysis of calcium carl in an isothermal container in a stream of nitrogen or under co vacuum. (USA) Pyrolyses were carried out in a stream of nitrogen and under co vacuum. Pyrolysis was much more rapid under constant w than in the stream of nitrogen. J P Auffredic and P Vallet, Rep NASA-TT-F-11435, Aug 1967, 3 (Sci Tech Aerospace Reps, 6 (8), 1144, N68-18071). 3 1509. Vacuum hot-pressing of magnesium aluminate spinel. (U; The densification kinetics of magnesium aluminate spinel ( vacuum hot pressing were studied between 1175° and 1460°t from 500 to 5100 psi. The vacuum furnace used had a tungsten heating element which heated the die by radiation. D R Rummier and H Palmour, J Am Ceram Sot', 51 (6), 1968, 32(
39. MISCELLANEOUS APPLICATIONS 1510. Effect of vacuum on the strength of balsa wood. (USA) Previous investigations have shown that exposure to vacum little effect on the ability of balsa wood to absorb energy. Spec of balsa wood were exposed to vacuum 10 4-10-5 tort for peri, long as 12 days. The effect of vacuum on compressive and be strength was found to be negligible. F E Blair et al, Rep AFIT-TR-67-4; AD-663920, 1967, 30 pag~ Tech Aerospace Reps, 6 (8), 1191, N68-17910).
IV. Materials and techniques used in
40. GASES AND VAPOURS 1511. Computing the volume of helium in cylindrical steel contain 10 to I0.000 psia. (USA) A table of factors for rapid, accurate calculation of the volu~ pure helium in cylindrical steel containers, at base conditions o psia and 70°F is presented. The table covers the pressure range psi increments and temperature range 0 to 120°F in 2 ° incremen H S Kalman, Rep MB-IC-8367, March 1968, 216 pages (Sol
AerospaceReps, 6 (8), 1140, N68-17562). 41. METALS AND ALLOYS 1512. Thermal expansion of polycrystalline titanium and zirc( (Great Britain) Observations of thermal expansion made between 2~K and differ considerably between two samples of each of the elemer and Zr. This must arise principally from a slight degree of prel orientation although X-ray pole figures show no strong evidet this. (Australia) J A Cowan et al, Cryogenics, 8 (3), 1968, 155-157. 42. GLASS, CERAMICS AND REFRACTORY OXIDES 4 Vacuum hot-pressiog of magnesium aluminate spinel. See ab number 1509. 1513. Environmentally assisted crack growth in glass. (USA) Glass exhibits the properties of high compressive strength an, density. Data were obtained on failure of unprotected glass sub to biaxial tension at about 50 per cent relative humidity. Remo surface flaws by etching in 5 per cent aqueous hydrofluork increased the mean failure strength. G M Sinclair and S P Withrow, Rep NRL-6635; AD-663885 1967, 21 pages (Sci Tech Aerospace Reps, 6 (8), 1191, N68-177761
37. METALLURGY, INORGANIC CHEMISTRY, ANALYTICAL CHEMISTRY 37 : 17 Review of literature on thermal contact conductance in a vacuum. See abstract number 1447. 37 : 34 Experimental investigation of ultrahigh vacuum adhesion as related to the lunar surface. See abstract number 1502. 37 : 34
Thermal degradation of polyethylene and polytetrafluoroetl during vacuum evaporation. See abstract number 1478.
1507. Vacuum test of instrument size gears. (USA) The report describes the experimental facilities developed for the evaluation of 8 different materials using hundreds of gears as the test component. Atmospheric and vacuum tests are described. JFarrelI, RepNASA-CR-92665, Aug 1967, 104pages(SciTechAerospace Reps, 6 (7), 1003, N68-16901).
V I. Miscellaneous 63. DOCUMENTATION, ABSTRACTS, BIBLIOGRAPHIES 6~ Plasma physics abstracts. 1 Jan 1966 - 3 1 Dec 1967. See ab number 1449.
43. PLASTICS AND ELASTOMERS