On the deployment mechanism of a large deployable onboard antenna of ETS-VI (Engineering Test Satellite Type 6), flight data are compared with predicted one. The deployment mechanism is thermally suitably controlled by heaters and by MLI (Multi-Layer Insulation) blankets. Such thermal control permits of deploying the main reflector within allowable temperature limits. That mechanism has thermally been evaluated with a mathematical model including thermal resistances between the inner and outer bearing rings. A good accuracy of the proposed method has also been demonstrated from flight data.
We present in this paper an analytic solution for the pillow deformation of the deployable mesh antenna which is segmented into a regular convex polygon by the cable net. We treat this problem by using both the methods of power series expansion of the complex variables and of Fourier analysis, in which we take into account the self-consistent boundary condition of the mesh on the supporting cable. Using this solution, we find that the magnitude of the pillow deformation of the regular polygonal facets is directly proportional to the square of the side length of the facet and the reflector curvature, and is an increasing function of the ratio of the tension of the mesh and cable. We also derive the approximate formulas for the pillow deformation and the best-fit surface error from the ideal parabola for the case of triangular and rectangular facets. We performed the numerical evaluation of the solution, and discuss the applicability of above mentioned approximate formulas. The analytic solution here derived gives us the basic and quantitative ideas of the pillow deformation and is useful for the quick numerical evaluation of the pillow deformation.
Starting loads observed in a free-jet type wind tunnel were investigated. Response functions between wall pressures and loads on a blunt model were derived by using Fast Fourier Transform (FFT). A large starting load was interpreted by the flow structure that separated nozzle flows, with Mach numbers less than the wind tunnel Mach numbers, impinge the model installed on a force measuring system (FMS). Probability functions for amplitudes of the starting loads were obtained to evaluate the possibility of excessive loads. The amplitude distribution of the loads and the experiencing frequencies were discussed from the viewpoint of normal random signals.
It is expected that an orbit transfer vehicle using an ion thruster (IOTV) can obtain a large payload ratio, because the ion thruster has a high specific impulse (several thousands seconds). However, orbit transfer missions by means of the IOTV require large trip times, therefore it is necessary for the ion thruster to have a sufficient endurance performance. In this study, the trajectory of the solar powered IOTV was analyzed in consideration of the influence of earth's eclipse, then the payload capability of the IOTV and the steady/endurance performance of the ion thruster were evaluated. For results, it was found that the IOTV could achieve approximately double the payload mass of the OTV using a chemical rocket, and a required durability to the ion thruster was comparable to one that has used for ETS-VI.
The flow around a wing with tip clearance is analyzed by a panel method, where the nonlinear equations must be iteratively solved to take into account the roll-up of free vortex sheets. The free vortex sheets consist of two parts shedding from the wing tip and the trailing edge. Both sheets are represented by several discrete vortex filaments. In the present iterative method, relaxation factors are used to improve convergence of a numerical process determining the source distribution over the wing surface and the location of vortex filaments. To avoid the singularity of induced velocity due to vortex filament, a vortex core is introduced, inside which vorticity is distributed instead of concentrated line vortex. The calculated results show good agreement with experimental aerodynamic characteristics such as local lift and drag peaks near the wing tip. The introduction of the tip vortex sheet is found to be useful to estimate the aerodynamic forces exerted on the wing with tip clearance, even though it treats the potential flow.