In order to establish automatic landing technologies for a space plane, the Automatic Landing Flight Experiment (ALFLEX) was planned and 13 flights were carried out from July to August in 1996. As one of the research items of ALFLEX, we developed the Pseudolite DGPS System for ALFLEX and evaluated its function and ability to acquire the differential GPS technique for an automatic landing. We chose the pseudolite method for the ALFLEX DGPS system because of the simplification of the onboard system and the improvement of the geometrical dilution of precision (GDOP) at landing. On the other hand, the pseudolite method had some technical problems and had many newly developed elements. Although there were some dilfficulties with the development of the Pseudolite DGPS System, finally the system performed the efficient accuracy at the automatic flight experiment. This paper presents the evaluation results of the Pseudolite DGPS System for ALFLEX using real flight data of ALFLEX.
Unsteady pressure distributions were measured in a series of experiments for a double swept-back SST arrowwing model in the transonic regime. The wing is an elastic model whose first natural frequency is 9.79Hz. Forty-six unsteady pressure transducers and 45 pressure taps were embedded in two semi-span lines and sensed unsteady and steady pressure distributions, respectively. Dynamic deformation data of the wing model were acquired by means of optical fibers and CCD cameras. The flow field around the model was excited by a trailing edge flap which was oscilluted around a mean deflection angle in a frequency range of up to 30Hz. Unsteady lift and moment coefficients were derived from unsteady pressure distributions. In this paper, not only pressure distributions but also aerodynamic coefficients induced by the flap oscillation are characterized relating to the dynamic deformations.
Tasks performed by a satellite-mounted manipulator include manipulation of large-scale and small-mass payloads such as spacecraft with large solar paddles and large pieces of the space station. The manipulated objects generally have high flexibility, that is, their lowest natural frequencies are very low. Therefore, in controlling such rigid body payloads there is the possibility of coupling between the flexible payload motion and the attitude control system. Because of this coupling, the satellite or payload may be uncontrollable. To cope with this problem, this paper proposes a coordinated control method which considers payload flexibility. In this method, a nominal payload model is constructed considering the rigid mode and a few of low frequency modes. Other higher frequency modes and variations of coupling coefficients are regarded as modeling errors. If appropriate control parameters are chosen considering the modeling errors, stability of the system can be guaranteed. The proposed control method also has high robustness and small computation cost. The validity and usefulness of this scheme are verified through results of computer simulations.
Vortex flows over rolling delta wings were investigated by flow visualization with oil mist and smoke wire. Compared flow visualization results with force measurements, unsteady aerodynamic characteristics of delta wing were analyzed. Experiments were conducted for two delta wing models with 14 and 7 degree apex half angles, which were forced to oscillate sinusoidally in roll. On the 7 degree apex half angle model, splitting of leading-edge separated vortices were observed in wing roll motion at high angles of attack. Disposition changes of leading-edge separated vortices by splitting induced ta wavy and complicated rolling moment hystagram. The vortex splitting on the slender delta wing is phenomenologically similar to the alternating vortex shedding on the ogive cylinder and to the trailing vortex on the conventional wing trailing-edge.
The purpose of present paper is to examine experimentally the drag reduction of the bluff bodies due to the cutout of the rectangular shape at the front edges of the square prism. The drag, the base-pressure, Strouhal number and the pressure distribution in the case of the rectangular cutout of various dimensions were measured and the visualization of the flow past the body was performed by means of the hydrogen babbles. The root mean square distribution of the velocity fluctuation was also measured by hot wire anemometer. The present experiment shows: (1) The distincture pattern of drag reduction for the cutout dimensions was shown by the contour of drag. (2) It shows that there is a case where the drag of the square prism is smaller than that of the circular cylinder and its case exists for wide reigns of cutout dimension. (3 ) As the minimum pressure of the edge of the cutout decrease, the absolute of the base-pressure decrease.
The synergistic effect of atomic oxygen and ultraviolet rays on the spin-coated polyimide film is investigated. The X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy suggest that the formation of carbonyl group at the film surface occurs during atomic oxygen exposures. The mass loss of the polyimide film and the enhancement carbon dioxide formation are observed during simultaneous irradiation of the low flux atomic oxygen and ultraviolet rays. These experimental results are explained by the photo-assisted chemical reaction of carbonyl groups formed by atomicoxygen attack. The fact that the synergistic effect of atomic oxygen and ultraviolet rays is obvious on the polyimide film, which is known as the material showing no synergistic effect in low Earth orbit, may reveal the importance of relative intensities of atomic oxygen and ultraviolet rays on the ground-based synergistic testing of the materials.