Experiences in simulating the space environment for scientific satellites

Classified abstracts 169---179 34 169. The electric state of the upper atmosphere. (France) The latest experimental data on the density distribution of electpons and ions in the upper atmosphere are given. The effects of latitude, season and solar activity are discussed, as well as complications due to the effect of the earth magnetic field (proton belt). The author points out that whilst in the troposphere the ions play an important role, the electrons determine the characteristics of the so-called ionosphere. Bibliography 7 items. E Vassy, Le Vide, 19 (112), July/Aug 1964, 193-210. 34 170. Solar radiation. (France) The extreme complexity of solar radiation is pointed out. We have a superposition of thermal spectra with source temperature ranging from 4000 to 10 million degrees together with nonthermal emissions associated with acceleration of ions and electrons up to relativistic energies. Full explanation of the observations awaits progress in plasma physics. In space simulation, solar radiation has so far been reproduced only very approximately. R Michard, Le Vide, 19 (113), Sept/Oct 1964, 265-271. 34 171. Vacuum-testing techniques and requirements for determining space craft performance. (France) Test chambers can be classified into 3 classes: small, intermediate and large, with approximate capacities of 50, 250 and in excess of 500 cubic feet respectively. An extensive survey of space simulation facilities in the USA indicated that small test chambers outnumber the intermediate size which in their turn o u t n u m b e r the full scale vacuum simulation facilities. It appears that the large chambers are associated with design verification, intermediate with development of components, whilst the small chambers are used primarily for research purposes such as materials investigation, outgassing, electronic performances etc. Most large and many intermediate size test chambers arc beset by significant operational difficulties. Solar simulation and albcdo simulation still constitute the major technical obstacle to adequate simulation of space environment and information relative to the design, performance and operation of major installations is altogether inadequate. (USA) Bibliography 30 items. R E Gaumer, Le Vide, 19 (113), Sept/Oct 1964, 272-301. 34 172. Experiences in simulating the space environment for scientific satellites. (France) A scientific satellite is predominantly electronic in nature and might include 1000 transistors, 1500 diodes, 5000 passive components and 8000 solar cells. The total investment in the space system up to the point of launch, including research and development, the spacecraft flight units, phototype design models and launch vehicle approaches 10 million dollars. Roughly speaking, the cost is divided equally between labour space hardware and launch vehicle. With such a large investment, it is provident to spend 10-20 pet cent in assuring that the craft is flight worthy and will yield useful information when operating in the space environment. The environment will vary widely during the life of the craft and broadly covers: pre-launch, launch, orbit, re-entry and planetary dwell. Of these the orbital and planetary environments are definable with the least confidence. In evaluating spacecraft it would be ideal if environment conditions could be reproduced exactly. This is neither technically n o r economically feasible. The article describes the type of tests carried out at the Goddard Space Flight Center, near Washington, USA. The importance of testing the complete working system as early in the project development cycle as p~ossiblc is stressed. Satellites which have passed the G o d d a r d simulation tests have proved satisfactory in space. (USA) J C New, Le Vide, 19 (113), Sept~Oct 1964, 327-339. 34 173. Observations in space. (USA) The technical advantages of orbiting solar and geophysical observatories are discussed, special attention being given to the projected orbiting X-ray observatory.

A I Berma~Scientific American, 209 (2), 29-37.

36. Drying, degassing a n d concentration 36 Freeze fixing of cells and tissues to preserve life. See abstract n u m b e r 201.

36 : 52 174. Some results of the experimental study of ice evaporation in vacuum. ( USSR) The author concludes that the intensity of evaporation is independent of the ambient pressure over the range 40 to 130 N/m' (3 X 10-x torr --1 torr). (USSR) E A Ermakova, InzhenFizZh, 7 (7), July 1964, 37-42. 36 : 26 175. Automatic control of vacuum spray drying installations. ( U S S R ) At the present time a method of drying liquid products by spraying in vacuum is widely used. In general, the vacuum in these installations is created by multistage ejector pumps and conventional methods of vapour pressure stabilization may not always maintain the vacuum within prescribed limits, mainly due to variations in the rate of spraying. As a result consistent quality of the final p r o duct cannot be ensured. To overcome this difficulty, an automatic control has been evolved which ensures constancy of the ratio " v a p o u r pressure at the ejector/outlet temperature of condenser". The theory underlying this control and its dynamic characteristics are discussed and the necessary control instruments enumerated. It appears that the system has received official sanction and is being applied in a n u m b e r of industrial undertakings. (USSR) Anon, Mekhaizatsiia i Avtomatizatsiia Proizvodstva, (10), 1964,

37-38. 36 176. Moisture adsorption in porous systems: relationship between vapour pressure and adsorbed moistures. (India) The possibility of predicting the vapour pressure of adsorbed moisture at any temperature from the moisture content of a porous system is indicated. (India) P T John, Indian J Technol, 2 (9), Sept 1964, 290-292. 36 177. Freeze drying of milk by radiant heat mechanism of heat transfer. (Japan) The experiments were carried out on concentrated whole milk with the object of obtaining heat transfer data for the design of a large scale plant. The following conclusions were drawn: (1) In the experimental set-up, the drying rate R (Kg/mZh) was independent of the thickness of the sample, provided the hot plate was kept at a constant temperature T(°C); (2) The connection between drying rate and hot plate temperature is linear and given by R = .0056 T + : 0.25. In these tests, the sublimating surface was kept at - - 2 5 ° C t h r o u g h o u t . (Japan) Bibliography 21 items. M Kako and T Tadano, Vacuum Chemistry, 12 (4), 1964, 152-158.

37. Metallurgy, inorganic chemistry, analytical chemistry 37

Treatment of silicon by electron bombardment. See abstract number 147. 37 Thermionic electron emission microscope for metallurgical studies. See abstract n u m b e r 163. 37 : 28 178. Radiation-electronic vacuum furnaces. (USSR) Three methods of operating vacuum furnaces are in c o m m o n use at present: radiation, induction and electronic bombardment. The article deals with an additional method, termed radiation-electronic. As the name indicates, in this method the charge is heated by the combined action of radiation and electron emission from a single source. A constant voltage applied between this element (the cathode) and the charge (the anode) accelerates the electrons and their impact supplements the heat received by radiatic;n. In order to prevent arcing, the pressure in furnaces of this type must not be lower than 10 -4 torr. If the charge is likely to emit much gas, the electronic part of the furnace can be switched off and the heating carried out by radiation alone till the gassing has moderated, when both factors can be made to operate. Details of such methods of operation are given and the dependence of power consumption on the emission efficiency of the cathode at various anode voltages is discussed. Furnaces of this type have the advantage of very high power concentration making short heating timgs possible. (USSR) Anon, Elektro Termiia, 38, 1964, 30-31. 37 179. Theory of the Procopiu effect. (Germany) The author establishes a theoretical relationship between the inten87