Calculation of the Shaping of a Space Umbrella Antenna During Strong Bending of Radial Rods Connected Along Parallels by Tensile Cables

Abstract— A cyclically symmetric umbrella antenna is considered, the frame of which consists of flexible inextensible radial rods connected in nodes along parallels by tensile cables. In the initial transport position, the multilink rods are packed in packages oriented in the direction of the system axis. After the packing ties are removed, the rods are deployed in radial planes under the action of elastic springs connecting the links, and are fixed in rectilinear positions at a given angle with respect to the axis, at which all cables connecting the same type of rod nodes take the form of regular polygons, while remaining loose. Further, under the action of the force of a damping hydraulic cylinder with pre-compressed springs, the root parts of all rods are slowly turned to the stops. In the final position, the radial rods, connected at the nodes by tensioned cables, take a curved shape. The tensile stiffnesses of the cables are determined so that the radial and axial coordinates of the nodes of the curved rods coincide with the coordinates of the points of the given surface of revolution. A model of strong bending of a flexible inextensible rod is constructed taking into account the unknown radial reactions of tensioned cables acting on it at the nodes. The links of the rod are considered as “cantilever” elements connected in series at the nodes in local coordinate systems, which can make large displacements and turns. The bending of each element is described by two specified functions, the shrinkage of the element due to bending is taken into account in a quadratic approximation. The obtained nonlinear deformation equations of the system, taking into account the geometric connections at the nodes, are solved by the method of successive approximations with respect to the unknown reactions of the cables. The obtained values of the reactions are then used to determine the required tensile stiffness of the cables at the given coordinates of the nodes. As an example of the calculation, a parabolic antenna is considered for various numbers of radial rods and components of links. The estimates of the accuracy of the proposed computational model of the antenna shaping are carried out.

Island Eye Island Ear

For more than ten years since 1974, Tudor collaborated with Fujiko Nakaya and Jackie Monnier on a grand-scale project to convert an entire island into a musical instrument. His plan was to play back recordings of sounds recorded at various locations on an island via parabolic antenna loudspeakers installed throughout the same island, which created sound beams modulated by wind that visitors would hear only when they crossed paths with them. Although Tudor spoke of the aim of Island Eye Island Ear as an attempt to examine the maximum scale of feedback, neither electronic nor acoustic feedback appears in the plan. This puzzle can only be solved by accounting for the experience of the visitors who walk around the island-instrument hearing one sound and reflecting on another heard before, something Tudor was exploring in other works from the same period such as Rainforest. The fact that the island project was met by criticisms of environmental destruction and remained unfinished points to the idiosyncratic nature of Tudor’s conception of “nature” derived from the teachings of Rudolf Steiner, and hints at the possible limit of his conceptual and physical enhancement of what musical instruments can be.

IRRADIATOR WITH MINIMAL LOSSES OF PARABOLIC ANTENNA FOR RADIO MONITORING SYSTEMS OF INFORMATION CHANNELS OF RADIO RELAY COMMUNICATION LINES

Analysis of the experience of modern struggle shows that the success of combat missions to sone extent depends on the timely detection of information from communication channels, in particular, radio relay communication lines. Increasing the detection range of the radio monitoring station can be achieved by using a mirror parabolic antenna with a radiation in the form of a conical horn with low losses due to the use of a matching device. The constructive decisions of matching devices are analysed and it is determined that most of them are resonant. The substantiation and selection of the design of the dielectric transformer with the length ( – wavelength in a round waveguide, m) for coordination of the conical horn irradiator in the whole band of its operating frequencies for the wave type is carried out. To achieve the goal, the methods of antenna theories and electrodynamics were used, in particular the theory of long lines. A mathematical apparatus has been developed for calculating the parameters of a dielectric transformer (the length ). It is stated that its impedance must be equal to the modulus of load resistance. The calculation of the value of the active transformed resistance according to the formula (10) always gives a positive value of the input resistance, the value of which is greater the greater the reactive load reactance. The reliability of the obtained formulas is confirmed by the convergence of units and graphs of dependences of the changes of the outer radius of the coaxial power line (its impedance), as well as the thickness and place of inclusion on the matching dielectric transformer . The practical significance of the research results lies in the possibility of improving the matching of a horn antenna based on a circular waveguide in the range of its operating frequencies for a certain type of wave.

A MULTILEVEL MODEL OF A PARABOLIC ANTENNA MIRROR SEGMENT FOR ANALYZING THE SENSITIVITY OF POWER CHARACTERISTICS TO A DESIGN FACTOR

Предложена и апробирована технология изучения влияния конструктивных решений на результирующие характеристики изделия на примере сегмента зеркала крупногабаритной параболической антенны. Выбраны силовые характеристики конструкции для статического и динамического анализа. Определен перечень конструктивных решений, влияние которых на результирующие характеристики представляет интерес, и разработана соответствующая система численных моделей. Новизна подхода заключается в построении многомерного и многоуровневого графа-модели, отражающего логику взаимосвязей конструктивных решений при разработке рассматриваемого объекта.