A theoretical analysis of the unsteady incompressible laminar flow in a semi-infinite porous circular pipe with injection or suction through the pipe wall whose radius varies with time is presented. The present analysis simulates the flow field by the burning of inner surface of cylindrical grain in a solid rocket motor, in which the burning surface regresses with time. An exact similar solution of fully non-linear form of the Navier-Stokes equation is calculated numerically. The flow field can be subjected to expanding coefficient of pipe wall α(=aa/ν) and injection parameter R=aV/ν. The properties of flow such as velocity components are represented as functions of expanding coefficient and injection parameter. Concludingly, the effect of burning surface regression on the flow field in combustion chamber of a solid rocket motor is so little that it may be negligible.
It is investigated, through theoretical analysis, the positional accuracies of DME-based navigation systems. It is supposed that the short range navaids, i. e. DME and VOR, are available. Four different types of navigation systems are examined, which utilize respectively; (1) single VOR/DME, (2) separate DME's, (3) one VOR/DME and another DME, (4) 3 DME's. In all the cases, the barometric altitude information is also assumed to be involved, in determination of position. The LMS error criterion is applied to calculate the estimation of position. The horizontal dilution of precision (HDOP) is so chosen as the evaluation parameter in comparison among the above-mentioned nav-systems. Obtained results are shown in the form of equi-HDOP contours around the typical configuration of navaids. Favourite discussions are given to the 3 DME's method from the theoretical viewpoint. But in actual operation, it is recommended that selection should be made between the four nav-systems, owing to such conditions as radio propagation, flight attitude, configuration of navaids etc.
A homing missile which is guided by the laws such as the proportional navigation guidance, the argumented proportional navigation guidance, and the optimal guidance has a target tracker to detect the line-of-sight rate, which is essentially needed for these guidance laws. Three different types of the tracker are used for this purpose; The first is the free-gyro gimbaled tracker; the second is the rate-gyro gimbaled tracker; the third is the strapdown type tracker. In this paper, basic dynamic models of these trackers are given at first, and then unstructured model uncertainty of these trackers are discussed. And the imperfect tracker stabilization is defined from the standpoint of the tracker model uncertainty, which is the important information for the robust design of the missile guidance system. By using this definition, it is shown that the stabilization loop gain of the rate-gyro gimbaled tracker and the sample frame time of the strapdown type tracker correspond each other.
In this paper, we discuss the reduction of RCS (Radar Cross Section) of helicopter rotorblade whose front edge is coated with thin microwave absorber, both theoretically and experimentaly. As a result, it is found that measured absorption values are 4-13dB at 15GHz and measured values show good agreement with those of calculation. These results are applicable to the design and manufacturing of stealth rotorblade having the cylinder-type absorber.
Simple parameters have been useful, for evaluating transportation efficiency of various vehicles. For this purpose, a new index E is proposed which is nondimensional and based on the area under the curve WP vs. R. This index includes a principal parameter WUV/P together with some additional parameters playing minor role.