The two-dimensional solutions are presented for the propagation of torsional waves in an elastic/viscoplastic circular cylinder subjected to a dynamically applied shear stress with non-linear radial variation at its end surface. The equations governing the dynamic torsional deformation of the cylinder are solved by using the method of numerical integration along bicharacteristics. The distributions of the dynamic shear stresses in the vicinity of the impact end of the circular cylinder are studied to determine the limitations of the elementary theory of torsional wave propagation. The numerical results for the torsional elastic waves in the circular cylinder are shown to be in good agreement with the existing exact solutions.
Many studies have shown the advantages of an Aeroassisted Orbital Transfer Vehicle (AOTV) which uses aerodynamic forces during an atmospheric pass to achieve orbital changes. This paper discusses optimal aeroassisted maneuvers to return from Geosynchronous Earth Orbit (GEO) to Low Earth Orbit (LEO). A trajectory optimization problem minimizing the total velocity change was formulated as a nonlinear programming problem, and numerical solutions were computed by the Sequential Quadratic Programming (SQP) method. The optimal trajectories are useful for the performance evaluation of vehicles or the design of flight profiles.
This report discusses about the “multicollinearity” problem in the equation error method. This problem represents the limit of the aerodynamic characteristics information given by the flight-test data. This problem is occurred not only when the strong correlations between the explanatory variables are generated by the aircraft's maneuver, but also when the number of the explanatory variables is more than the maximum number of the variables which can be essentially independent in the equation of motion. Furthermore, the physical meanings about the partial regression coefficients and the multicollinearity are schematically explained with the regression plane.
The reflecting surface of an inflatable reflector for space use consists of one or several inflatable elements (membrane elements), which are pressurized to generate an accurate reflecting surface. The surface of an inflatable element deforms as the pressure is applied. If the element is pressurized on the ground, gravity force also changes the deflection of the element. This means that the internal pressure and the gravity force influence the surface error of the element. This paper presents an analysis of the deflection and the surface accuracy of an inflatable element subjected to pressure and gravity loadings based on a flexible membrane strip model, the initial configuration of which is straight or a circle arc, with both ends immovably supported. The gravity is assumed to act in any direction in the plane which includes the membrane strip. The perturbation method is used to solve the membrane deflection due to the gravity force, assuming the ratio of gravity to pressure and the center height of the membrane to be small. The analytical expressions for the deflection and the surface error of the membrane strip subjected to pressure and gravity are obtained. It is found that the effect of gravity on the surface error increases as the ratio of gravity to pressure and the center height of the strip increases, and as the rigidity (Young Modulus) of the membrane decreases. It is also found that if the membrane strip is not so rigid (Young Modulus is not so high), the effect of gravity on the deflection is smallest with the membrane vertically placed. On the other hand if the membrane strip is rigid enough, the effect of gravity is smallest with the membrane horizontally placed.
A five-hole arrow head pitot tube is tested to measure flight velocity and angle of attack. This paper presents experimental equations with corrective coefficients. These equations enables us to calculate flight velocity and angle of attack in terms of the measured pressure. The time lag corresponding to the change of angle of attack is also reported.