ensuring desired satellite pointing. The attitude control approaches broadly classified as active and passive are used alone as well as in combination. Proposed here is a new attitude control approach wherein solar heating of large panels/bimetallic strips mounted on-board is utilized to vary the overall centre of mass of the system in accordance with a suitable feedback control scheme. The sensors, of course, are required to measure the attitude angles as well as the rates of their variation. Mini-servo units are utilized to rotate/flip the strips to achieve the desired centre of mass variation. The concept may be particularly useful in augmenting the effectiveness of the primary attitude control system. (Paper number IAF-ICOSP89-6-8.) 6-9. On the Selection of Low-temperature Thermal Tubes' Parameters for Spacecraft Temperature Control Systems V. F. Prisnyakov, Y. K. Gontarev, Y. B. Navroosov & V. N. Serebryansky (Dniepropetrovsk University), Intercosmos Council, USSR Academy of Sciences, Leninsky prosp., 14, 117901 GSP-1 Moscow V-71, USSR. The use of thermal tubes for heat transfer in the active part of the Spacecraft Temperature Control Systems seems to be reasonable, since this allows us to make use of the phase transition released heat transfer principle in the closed vaporization and condensation cycle. The intensity of the heat transfer inner processes depends on a number of factors: geometrical shape of the thermal tubes, their size, capillary pattern, type of working liquid and structural materials. In this connection a number of experimental and theoretical investigations have been carried out to study the regularity of phase transitions in the low-temperature thermal tubes under a wide range of the regime parameters, simulating the conditions of their operation on-board the spacecraft. Thoroughly investigated are the regimes of thermal tube operation. Heat transfer at the evaporation stage is characterized by self-simulation of the heat-emission coefficient. A model of heat emission for liquids boiling in capillary structures has been worked out, which is based on the general regularity of heat transfer under boiling and takes into account the peculiarities of vapour bubbles generation in a porous layer. The generalized representation of the boiling heat transfer law has been obtained in a standard form. The dependencies suggested are valid for describing heat emission under boiling of a large number of existing and prospective heat carriers. The effect of the tubes design parameters on their efficiency has been also analysed. Recommendations for design of thermal tubes with emitter mass-energy parameters close to the maximum are suggested. (Paper number IAF-ICOSP89-6-9.) 7. ADVANCED SOLAR SPACE POWER SYSTEMS 7-1. Energy the Enabler: In a Changing, Growing World F. A. Koomanoff Office of Basic Energy Sciences, Department of Energy, USA. In 1950, the world consumed 77 quadrillion BTUs of energy—by 1985, consumption had grown to 302 quadrillion BTUs. We in the United States in 1950 used 13 million BTUs per person while the rest of the world used only 1 million BTUs per person. The rest of the world is catching up; for in 1985, the USA used 6 million BTUs per person to all others using just 1 million BTUs.
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