Sunao Hasegawa

We examined ejecta size distribution when aluminum alloy 2017-T4 spheres with a diameter of 3.2 mm impacted aluminum alloy 6061-T6 targets with a plane surface and a curved surface at velocities of 4 km/s. We used a two-stage light-gas gun at the Institute of Space and Astronautical Science (ISAS)/Japan Aerospace Exploration Agency (JAXA). To examine the scattering angles of the ejecta, the following was placed 50 mm in front of the target: a witness plate (150 mm × 150 mm, 2 mm in thickness) made of copper with a hole of 30 mm. The ejection behaviors of fragments were observed using a high-speed video camera. The number of ejecta when impacting on the curved surface target was more than that when impacting on the flat surface target.

5th Space Debris Workshop (January 22-23, 2013, Chofu Aerospace Center, Japan Aerospace Exploration Agency (JAXA)), Chofu, Tokyo, JapanTo protect a satellite from space debris impact threat, a satellite designer should employ structure material which has enough protection capability against debris impact. However, for some flexible components, it is impossible to use such strong materials, for example, expandable structures and wire harnesses. To protect these flexible components, a flexible debris bumper is needed. High strength fiber fabric is one of flexible debris bumper material. Since the alamido fiber has high tensile and shear strength, the alamido fiber fabric is known to be also useful for high velocity impact protection. The alamido fiber fabric was used as a part of the Staffed Whipple Bumper installed on the International Space Station. A satellite on the low earth orbit needs to pay attention to impacts on debris smaller than 1 mm, because debris environment models show such small debris will impact on the satellite during its operation lifetime. Therefore, to employ the alamido fiber fabric as a debris bumper, it is necessary to know their sub-millimeter debris impact damage. The purpose of this study is to investigate sub-millimeter debris impact damage of the fiber fabric.Physical characteristics: Original contains color illustrations

5th Space Debris Workshop (January 22-23, 2013, Chofu Aerospace Center, Japan Aerospace Exploration Agency (JAXA)), Chofu, Tokyo, JapanAluminum Foam targets were tested as a favored candidate material for a light-weight space debris bumper shield. A target consists of layers of aluminum foam plates, and each plate was made of aluminum powder, tens of micro-meters in diameter. Their porosity, density, and nominal diameters of pores is 82 %, 500 kg/m3, and 0.3 mm, respectively. Metal spheres are employed as simulated debris and accelerated to 4 to 7 km/sec. Bulb shaped craters with small entrance holes are observed. No high-speed ejecta is observed by use of a high-speed video camera.Physical characteristics: Original contains color illustrations

5th Space Debris Workshop (January 22-23, 2013, Chofu Aerospace Center, Japan Aerospace Exploration Agency (JAXA)), Chofu, Tokyo, JapanA new advanced ceramic thruster made of monolithic silicon nitride has been developed in ISAS/JAXA. In order for secure operation of a spacecraft, the reliability of the ceramic component against space debris and micrometeoroid impact has been investigated through hypervelocity impact tests. Silicon nitride plates were impacted by spheres of stainless-steel and other materials with 0.2-0.8-mm diameters in the velocity range up to 8.0 km/s using a two-stage light-gas gun. Using crater depth data under various impact conditions, the penetration equation of silicon nitride was determined. The impacted samples showed fracture patterns of three types: cratering, cratering with spallation, and perforation. These fracture patterns were well categorized by the multiple forms of the penetration equation.Physical characteristics: Original contains color illustrations