The thermal contact resistance between the balls and the inner and outer rings of a space-use deep groove ball bearing is analyzed assuming that heat transfer between smooth contacting elements occurs through the elastic contact areas. It is also assumed that the stationary bearing sustains axial and/or radial loads under steady-state temperature condition. The shapes and sizes of the contact areas are calculated using the Hertzian theory. The thermal analysis is based on an isolated isothermal elliptic contact area supplying heat to an insulated half-space. The formulation of the resistance is given as a function of a geometric factor of the contact area and the thermal conductivity of the bearing. In particular, an expression for the axial load is derived with careful consideration of changes in contact angle induced by elastic deformation at the contact area.
This paper is concerned with detailed results of an experimental study on nonlinear dynamic stability of pitching motions of the various recovery bodies at a low subsonic speed. The experiment is conducted in an induction type transonic wind tunnel at Mach number of 0.2, and measurement of angular variation with time of the models is made for pitching oscillation with a finite amplitude. An approximate oscillation equation, that is formulated by use of an unsteady aerodynamic pitching-moment coefficient and, in general, is capable of predicting fairly accurately the experimental data having various nonlinear oscillatory modes, is proposed on the basis of the concept of a curvefitting method. It is shown that the aerodynamic pitching moment and the associated nonlinear dynamic stability can be determined from the numerical simulation to the experimental data with sufficient accuracy.
This paper considers a method for dynamic analysis of multi rigid bodies in space with impulsive forces, impact, and discontinuous velocities. The system equations of motion for rigid bodies connected with hinges are derived from the virtual work principal to the D'Alembert form of the Newton-Euler equations. Main body velocities/angular velocities and each hinge's angular velocity are used for the system variables. Discontinuities in the velocity are observed when either an impulsive torque is applied to a hinge or a sudden hinge lock occurs. A general formulation between the velocity jump and the impulsive force is presented for the system equations. The panel deployment of a spacecraft structure is numerically simulated using the method to demonstrate its capabilities.
The concept of flight-path stability, which is today in use, is based on the characteristics of steady unaccelerated flight conditions, and so can be called “static flight-path stability.” After the description about the “static flight-path stability, ” this paper introduces the “dynamic flight-path stability” concept for accelerated/decelerated flight conditions, and discusses the necessary elevator-compensation to provide an airplane with the designated dynamic flight-path stability. Furthermore, it is demonstrated that the airplane with the compensation can stably control the flight-path by the elevator in the backside flight region, through the study on the airplane's response and phugoidmode characteristics.