Seishiro Kibe

Analysis of Jet Formation and Penetration by Conical Shaped Charge with the Inhibitor

Abstract This paper proposes a numerical method to simulate not only the jet formation process of the conical shaped charge with the inhibitor: approximately 11 km/s aluminum jet, but also the succeeding flight and impact processes onto the target plates. The method is demonstrated by performing a series of numerical analyses with a multi-processor type hydrocode: AUTODYN-2D™ and is successfully verified by comparing with the experiment conducted by National Aerospace Laboratory of Japan to assess the protection of orbital space debris impacts on the spacecraft in the low earth orbit (LEO). In the numerical model the shock-induced vaporization is taken into account by applying the Tillotson equation of state to the liner and the target materials. We can visually know the distribution of various field variables in the jet formed from the liner and in the jet and target after the impact: contour plots of velocity, temperature, density, energy, etc. Besides they are useful for understanding the mechanism of the phenomenon, it is truly interesting to see what physical phase the jet is in, especially by the phase indicator. The decrease effect of the jet mass during travel to the target is investigated, as well as the density and shape effect of the jet on the size of the crater formed on the target. The investigation is useful for the calibration of the jet mass and jet velocity, because it is difficult to know the accurate information on them by the experimental measurement. These numerical results are discussed over the comparison with the corresponding experimental results in the jet shape, the crater shape, the jet mass and the jet velocity.

A numerical simulation method and its validation for debris impact against the whipple bumper shield

The authors carried out three series of experiments of the first bumper perforation and main wall cratering processes directly caused by three different types of projectiles with about 2, 4 and 7 km/s impact velocities but comparable kinetic energies, for the purpose of investigating the space debris hypervelocity impact against the single walled Whipple bumper system [1]. In the present study, a number of parametric numerical simulation analyses were performed in order to optimize the material properties of bumper and main wall materials through the comparison with the experimental results of the single target impacts by the projectiles. Then a couple of numerical calculations to simulate the whole impact process were performed and compared with the corresponding experimental results. This paper offers a numerical simulation method applicable to the space debris impact against the Whipple bumper shield, after providing the optimized material models through the comparison of the results for several single target impact tests between the experimental and parametric numerical analyses.

Numerical simulation of space debris impacts on the Whipple shield

The authors carried out three series of experimental tests of the first bumper perforation and main wall cratering processes directly caused by three types of projectiles with about 2, 4 and 7 km s−1 impact velocities but comparable initial kinetic energies, by using three different accelerators (one-stage powder gun, two-stage light-gas gun and rail gun), for the purpose of investigating space debris hypervelocity impacts onto single-walled Whipple bumper shields [1]. In the present study, after reviewing the numerical simulation method of hydrocode for both Eulerian and Lagrangian descriptions, a number of parametric numerical simulation analyses using multiple material Eulerian methods were performed in order to optimize the material properties of bumper and main wall materials through comparison with experimental results of single target impacts by the projectiles. In particular, the material data on the dynamic fracture phenomena are discussed in detail in the first part. Then a couple of numerical calculations using the interactive Lagrangian rezoning method to simulate the overall impact process against the single walled Whipple shield were performed and compared with the corresponding experimental results. Both results indicated fairly good agreement with each other. Moreover, it was demonstrated that the present method is helpful and efficient in understanding the impact phenomena and fracture mechanism in the space debris hypervelocity impact problem. Finally the multiple material Eulerian method was applied to the same problems modeled by the interactive Lagrangian rezoning method used previously, because the former is much easier to use for almost all users, although it is more diffusive and unclear of material boundaries than the latter. Those two kinds of numerical results also indicated fairly good agreements with each other.

Numerical and experimental study on the shaped charge for space debris assessment

Abstract This paper proposes a numerical analysis method to simulate jet formation and penetration process by the ‘low-velocity’ (6∼7 km/sec-class) inhibited shaped charge launcher, in order to assess the protection capability of the bumper structure against orbital space debris impacts on the spacecraft. The present simulations by a two-dimensional hydrocode (AUTODYN-2D), which was performed by an improved method on the basis of our former works, were compared with the test results based upon the experimental method that we had proposed in our another work. The both results were in fairly good agreement, and the feasibility was ascertained of the calibration between the inhibited CSC jet and solid spherical projectile by the numerical method. Consequently, the accuracy of the ballistic limit curve at 10∼15 km/sec is expected to be enhanced by making use of the present method hereafter.

A space station experiment on large antenna assembly and measurement

Abstract The large assembly antenna in space can meet future requirements of both high frequency and large aperture. This paper proposes an experiment on assembling a large antenna at the Space Station, and discusses a realizable procedure of the experiment. The objective of this experiment is that a large antenna of a 10-m diameter is assembled in space and at the same time problems occurring in the assembling process are clarified by conducting the following experiments: assembly of test articles by manipulators, measurement of both mechanical and electrical performance of the assembled antenna, test of the pointing control system, and operational test. In the operational test, the weather radar development test and the large aperture microwave radiometer development test are conducted. Furthermore, the problem areas and items of further study are discussed in this paper.

EVA-related activities in Japan.

Recognizing the importance and fertility of the extra vehicular activity technologies in future space development and utilization, some related research activities have been conducted in Japan, though it has not committed itself to developing its own manned space flight capability. The purpose of this paper is to introduce and evaluate these EVA-related activities and to indicate the next step for Japan to get into the era of manned space activities including EVA in reality.