The projectile shape and material effect on the momentum transfer for asteroid orbit change Daisuke Yokoo, Masashi Tanaka, Masaya Ikeda, Takao Koura and Yausuhiro Akahoshi Department of Mechanical and Control Engineering, Kyushu Institute of Technology 1-1 Sensui, Tobata, Kitakyushu, Fukuoka, 804-8550, Japan Tel & Fax: +81-93-884-3151 Email:q344149d@mail.kyutech.jp IAA-PDC-17-04-P06 INTRODUCTION In this study, we will discuss about momentum transfer in which the kinetic impact is used for an asteroid orbit change. An effect of the kinetic impact is evaluated by β, where this ratio β is defined as comparison between the asteroid output momentum and the impactor input momentum shown in Eq. (1). The β ratio is affected by various factors. In this poster, we focused on two factors: There are projectile shape and the material effect. The purpose of this study is to reveal the projectile shape and material effect tendency and identify the respective shape and material from experiments using different projectiles. 𝑴 𝑨 ∆ 𝑽 𝑨 = 𝑴 𝑰 𝑽 𝑰 −∑ 𝒎 𝒆 − 𝒗 𝒆 𝒄𝒐𝒔𝜽 = 𝟏+ ∑ 𝒎 𝒆 𝒗 𝒆 𝒄𝒐𝒔𝜽 𝑴 𝑰 𝑽 𝑰 𝑴 𝑰 𝑽 𝑰 =𝜷 𝑴 𝑰 𝑽 𝑰 ···(1) 𝑴 𝑨 ∆ 𝑽 𝑨 𝒎 𝒆 𝒗 𝒆 𝑴 𝑰 𝑽 𝑰 𝜽 𝜷 SCALING SHAPE EFFECT 𝛽−1~ 𝑣 p ∙ 𝜌 𝑡 𝑌 𝑡 3𝜇−1 ∙ 𝜌 𝑡 𝜌 𝑝 1−3𝜈 Cylinder Cone Punch Cup Sphere shape   𝑣 𝑝 ⋯ Impact velocity 𝜌 𝑡 ⋯ Target density 𝑌 𝑡 ⋯ Target strength 𝜌 𝑝 ⋯ Projectile density K. A. Holsapple, “Momentum transfer in asteroid impact. I. Theory and scaling”, Icarus 221 p875-887, 2012 where μ and ν are called “scaling parameter”. The ν is about 0.4 for most materials. So, we chose ν=0.4 and plot data obtained from experiments in order to calculated C and μ from an approximate curve. The projectile shapes does not affect the ejecta mass MATERIAL EFFECT   Cu Chromium steel Ti Aluminum alloy Appearance We compare the β ratio at an actual impact velocity range using scaling law. The β difference was caused by the spread angle of the ejecta emission less than 15 km/s the Cup shape has the highest β ratio more than 15 km/s the Sphere shape has the highest β ratio The aluminum alloy has the best β ratio, followed by copper CONCLUSION Projectile shape does not affect the ejecta mass Projectile shape affects the ejecta emission direction The Cup shape has the best β less than 15 km/s and Sphere shape has the best more than 15 km/s. The aluminum alloy has the best value for β