Closed cycle coolers for space applications

Single stage Stirling coolers providing refrigeration at around 80 K have been developed for space use and are now being produced commercially. Development work is now concentrating on multistage coolers for temperatures below 30 K. This paper describes results from a two stage cooler built at the Rutherford Appleton Laboratory and preliminary tests on a closed cycle 4 K cooler.     

Interaction of artificially injected plasma flows with ionospheric plasma

Results of rocket experiments on study of plasma flows (PF) artificially injected by sources separated from vehicles and their effect on medium parameters in ionosphere at altitudes 160:230 km are presented.PF were injected comprising lithium ions with velocities 1,2 x 10⁴ m/sec. and cesium-potassium ions with velocities (1,4–1,5)x10³ m/sec. Mass flow rate in case of lithium PS is 2 mg/sec, and in case of cesium-potassium PS is 0,2 g/sec. During experiments mass-spectrometer measurements of ion medium content in ranges of different ion masses were held, disturbancies of electric fields with frequencies up to 20 kHz and electron flows with energies 0,7keV, 4,6keV and over 40 keV were controlled at distancies from 150m to (500–600)m between plasma source and scientific equipment.     

Megahertz power converters for specific power systems

Some of the problems in the development of pulsewidth power converters when the switching frequency is increased from hundreds of kilohertz to tens of megahertz are highlighted. The major goal is the establishment of a ten megahertz power chain designed to operate in a distributed system from a DC power bus of 24 to 48 V. Available components and materials are discussed, and possible topologies-flyback, forward, push-pull forward, and buck converters-are examined. The performance criteria chosen for this analysis are, in the order of preference, output requirements, size and weight, efficiency, and cost     

Prebiotic oligodeoxynucleotide synthesis in a cyclic evaporating system at low temperatures.

Deoxynucleoside 5'-monophosphates were condensed by cyanamide or by l-ethyl-3-(3-dimethylaminopropyl) carbodiimide in the presence of ammonium chloride at 0 degree, 37 degrees or 60 degrees C through several cycles of evaporation to dryness with replenishment of all reactants at each cycle. We found that at 37 degrees or 60 degrees cyanamide gives distinctly more high molecular weight material than does carbodiimide. Indeed, the yield of condensed products for the cyanamide reaction (dimers and higher oligomers) was found to be between 60 percent and 80 percent. The molecular weight distribution of the product shifts to higher molecular weights as cycling continues at 37 degrees or 60 degrees for both condensing agents. The water soluble carbodiimide gives higher yields of low molecular weight product but much lower yields of the higher molecular weight products. At 0 degree yields of high molecular weight product were low for both condensing agents. Results of characterization of the products demonstrate the synthesis of oligodeoxynucleotides including tetramers, with 3'-5' phosphodiester linkages.     

Functional state of chromatin and proliferative activity of meristematic cells in pea seedlings under various clinostatic conditions.

Data from a complex cytochemical analysis show that the functional state of chromatin and the level of the cell proliferative activity may be reliable cytological criteria for primary structural and functional changes that result in disturbances of plant growth and development. Autoradiographic and cytophotonetric studies made it possible to establish certain differences, induced by fast rotation (50 rev/min) on the clinostat, in the chromatin state and cell reproduction of the pea seedling root meristem for the initial stages of plant development. There were no essential differences for the given parameters under slow (2 rev/min) clinostatic conditions.     

Evaluation of light emitting diode characteristics for a space-based plant irradiation source.

Light emitting diodes (LEDs) are a promising irradiation source for plant growth in space. Improved semiconductor technology has yielded LED devices fabricated with gallium aluminum arsenide (GaAlAs) chips which have a high efficiency for converting electrical energy to photosynthetically active radiation. Specific GaAlAs LEDs are available that emit radiation with a peak wavelength near the spectral peak of maximum quantum action for photosynthesis. The electrical conversion efficiency of installed systems (micromole s-1 of photosynthetic photons per watt) of high output LEDs can be within 10% of that for high pressure sodium lamps. Output of individual LEDs were found to vary by as much as 55% from the average of the lot. LED ratings, in mcd (luminous intensity per solid angle), were found to be proportional to total photon output only for devices with the same dispersion angle and spectral peak. Increasing current through the LED increased output but also increased temperature with a consequent decrease in electrical conversion efficiency. A photosynthetic photon flux as high as 900 micromoles m-2 s-1 has been produced on surfaces using arrays with LEDs mounted 7.6 mm apart, operating as a current of 50 mA device-1 and at an installed density of approximately 17,200 lamps m-2 of irradiated area. Advantages of LEDs over other electric light sources for use in space systems include long life, minimal mass and volume and being a solid state device.     

An advanced flight control and navigation system implementation fortactical helicopters

US Army helicopters that will allow single-crewmember operability in tactical environments require a high degree of automation. A tightly integrated flight control and navigation system has been studied. An architecture is discussed which meets anticipated flight control and navigation requirements, at an acceptable weight, using techniques of functional and physical integration. The architecture maximizes the sharing of sensor and computational resources in a flight critical environment and uses modular equipment packaging, dual fault-tolerant tetrad ring-laser-gyro inertial measurement units, and triplex self-checking processor pair-based flight critical processing channels     

On ionospheric aerodynamics

This paper presents theoretical methods to determine the gas dynamic and the electrostatic effects due to the interaction caused by a rapidly moving body in the ionosphere. The principles of the methods are derived from the kinetic theory of collision-free plasma. It is shown that the collective behavior of the collision-free plasma makes it possible to use the fluid approach to treat the problems of ionospheric aerodynamics. Various solutions to the system of fluid and field equations that have direct bearing on the ionospheric aerodynamics are presented and discussed. Physical significances of the mathematical results are stressed. Some outstanding unsolved problems in ionospheric aerodynamics are elaborated and discussed.     

Thermoluminescent dose measurements on-board Salyut type orbital stations.

A small, vibration- and shock-resistant thermoluminescent dosemeter /TLD/ system--named PILLE--was developed at the Health Physics Department of the Central Research Institute for Physics, Budapest, to measure the cosmic radiation dose on board orbital stations. The first on-board measurements with this system were performed /by B. Farkas, the Hungarian astronaut/, on the Salyut-6 space station in 1980. The same instrument was used by other crews in the following years. Doses measured at different sites in Salyut-6 are presented. The dose rates varied from 0.07 to 0.11 mGy.day-1. After the first cosmic measurements, the system was further developed. The minimum detectable dose of the new TLD system is 1 microGy, i.e. less by on order of magnitude than that of the former system. The self-irradiation dose rate of the TLD bulbs is also reduced--by more than one order of magnitude--to 10 nGy.h-1, by the use of potassium-free glass for the bulb envelope. This new type of PILLE TLD system is currently on-board Salyut-7. The dose rates /0.12-0.23 mGy.day-1/ measured in 1983 are presented in detail.     

Potential defense applications of expert systems

The authors provide an overview of expert systems and how they may effect the development of future defense applications. Military uses of computers are outlined, and expert-systems fundamentals are described. Artificial research and development efforts by the military are examined, and potential military applications are discussed. Expert systems efforts at NASA, by the US Air Force, and for the Strategic Defence Initiative are considered