A high pressure gas source is obtained by the compression of a free piston which is driven by the hydrogenoxygen detonation wave. It is easily formed in a cylindrical, tube, so-called detonation tube, and pushes a free piston with its high pressure. The gas in front of the free piston in a compression tube is compressed by the piston and arrives a high pressure state for a while. The pressure peak and the half width of the peak at the end of the compression tube can be controlled by adjusting the conditions in both of the detonation tube and the compression tube. In the present paper, the possibilities of the detonation driving and applying the high pressure source to launce a projectile to a high velocity are discussed. In order to know the motion of the free piston in the compression tube, a simple magnetic detector system consisting of nine electric-magnetic sensors is employed.
Tumbling motion makes it difficult to retrieve a satellite with an on-board manipulator. This paper proposes a new control scheme of a space manipulator based on an approximate model for the dynamics of a tumbling satellite. The proposed model is described as a superposition of three rotational motions of constant angular velocities. Kalman filtering technique is adopted to estimate the target motion based on visual information. The parameters of the approximate model are calculated from kinematical constraints using estimated results. Thus, the capture planning becomes simple with the approximate model parameters. The motion of a grapple fixture along a particular principal axis of a target satellite nearly stops relative to the end-effector of a manipulator. In the control scheme, the rendezvous satellite and the manipulator make rotational motions of certain constant angular velocities based on the approximate model. The validity and the usefulness of the proposed scheme are verified by computer simulations and experiments using a 3-D hardware simulator with 9 degrees of freedom.
This paper presents results of an experimental study on the buckling of circular cylindrical shells under pure bending. In the experiment, emphasis was placed on the effect of the length of the cylinder. A high precision loading device was developed, by which the torque can be applied equally on both ends of the cylinder. Test specimens made from polyester films have a length-to-diameter ratio ranging from 1 to 20 and a diameter-to-thickness ratio of 156, 200, 234, or 300. Large deformation accompanied by the flattening of the cross section was observed before buckling in long cylinders. For those having the length-to-diameter ratio greater than 15, the buckling torque was about 60% of the classical value calculated on the basis of the classical buckling stress under axial compression. The pre-buckling deformation was hardly observed in short cylinders. For those having the length-to-diameter ratio from 1 to 3, the buckling torque approached the classical value.
Simple nanosecond spark sources (Nanospark) have been developed for application in optical visualization systems of high-speed phenomena, especially shock wave phenomena. During operation, a 1400-4000pF capacitor in the spark head is pulse-charged in about 60 to 100ns with automatic preionization from a high-voltage pulse generator switched by a thyratron. This charge is available for discharge when the gas breakdown starts. The preionization is useful to start the gas breakdown easily and to decrease the pulse to pulse time jitter. This Nanospark produces 15-80ns (FWHM) light pulses with a time jitter of less than 60ns when operated at 6-14kV and in air of atmospheric pressure. The spark has adequately exposed the film of 100 ASA in various schlieren and shadow systems. With a Xe-filled source, the quantity of radiation may be increased up to tenfold while the pulse width rises up to 900ns depending on gas pressure. These sources have adequately exposed customary ASA 400 colour film in various colour schlieren experiments.
A study of ionization characteristics of high enthalpy nozzle flow has been carried out by using the arc-heated wind tunnel with conical nozzle, where argon gas is used for the simplicity of analyzing the phenomenon. In this experiment, the exit pressure is relatively low, so that the non-equilibrium flow can be realized. The electron temperature and electron number density are measured by Langmuir probes at three stations located on the nozzle surface for several stagnation temperatures. The test results are compared with the analysis using the frozen flow which is commonly treated in such a flow. As a result, the nonequilibrium flow with non-frozen flow characteristics were obtained near the nozzle surface. The experimental result of electron number density rapidly decreases toward the downstream unlike the analysis. On the other hand, the electron temperature showed good agreement with each other. Thus, the ionization characteristics were made clear near the nozzle surface.
A new flap pressure distribution with the center of pressure closer to the main wing is presented for enhancement of the lift capability on an HLD configuration. The HLD has such an aerodynamic characteristics that the aft element may induce an additional flow velocity over the main wing due to its formation of a pressure distribution and thus of vorticity with some strength and the associated circulation. The influence of the aft flap on the main wing was quantified by the potential flow theory of conformal transformation and a 2D wind tunnel test was carried out for validation of the effect of the pressure distribution with the center of pressure closer to the main element on some practical aerofoils. As a result of the tests, more lift was obtained than the conventional one which used to be a type of maximum lift loading over the flap.