A long time operation test of an ion engine system with its own propellant tank was carried out successfully. The total operating time was 1, 530 hrs and propellant efficiency, which is defined as the ratio of the beam current integrated over the test period to the consumed propellant in terms of charge, was found to be 59.7%. Though this experiment was interrupted by the vacuum chamber-originated flakes that bridged the accelerating grid system, the ion engine was operated without the indication of degradation in the hollow cathode, the isolator and the vaporizer. The thickness of the flake was explained from amount of sputtering material. The basic operating parameters of the ion engine were maintained through this experiment, As the flakes in the discharge chamber are not observed, the longer life will be expected. Finally, this experiment was terminated with using up the propellant of its own tank.
For the bars with initial deflection under tension loads at ends there are two cases to be treated separately according to the condition whether the compression side remains elastic all through the deformation or becomes plastic if it is only partial and temporary before the entire cross-section reaches the ultimate state of uniform tensile stress. The former case is treated in the previous report and in this paper the latter case is discussed. It is shown that in the course of deformation development there are seven stress distribution patterns, the sequence of which can be classified into three categoriesin accordance with the combination of initial deflection ratio and slenderness ratio.
This paper aims at contribution to the selection of a suitable material for rocket nozzle throat by means of evaluation of the thermal shock resistance and the thermal shock fracture toughness of several varieties of graphite. The thermal shocks are given by an arc discharge heating at the central area of disk specimen simulating the thermal stress conditions of rocket nozzle throat. In these tests, determining the critical threshold values of electric power to initiate and/or propagate cracks in the disks, the thermal shock resistance Δ(=σtk/Eα, σt, tensile strength; k, thermal conductivity; E, Young's modulus; α, thermal expansivity) and the thermal shock fracture toughness ∇(=KICk/Eα, KIC, fracture toughness of mode I) are evaluated en bloc quantitatively. The Δ's and ∇'s of carbon fiber chips reinforced graphites and two-and threedimensional carbon fiber reinforced carbon composites are also determined and discussed concerning the suitability for rocket nozzle materials.
This paper describes an experimental study of the flow past rectangular cylinder of square section placed on a plane boundary. The experiment was carried out in an N.P.L. blowdown type wind-tunnel having a working section of 500mm×500mm×2, 000mm in size at the Reynolds number 4.74×104. The surface-pressure distributions on the rectangular cylinders were measured, and the vortices of two kinds generated in the flow-field around a rectangular cylinder have also been observed. Consequently, it is found that the flow patterns and vortices around a rectangular cylinder of W/D (ratio of length to width)=1.5 is different from those for W/D=0.06-1.0.