OBSERVATION OF EXPANDING VAPOR CLOUD GENERATED BY HYPERVELOCITY IMPACT

Observations of the expanding vapor cloud generated by the hyperveloci ty impact have been carried out. Under usual laboratory conditions, ro ck or ice materials cannot be vaporized completely, In order to invest igate the expansion of a large amount of the vapor by complete vaporiz ation caused by hypervelocity impact, we used a nylon projectile and m easured the fundamental quantities of the vapor, that is, the expansio n velocity, the shape of the vapor cloud, the temperature, and the lig ht energy, by observing the light radiating from the vapor. The expans ion velocity of the leading edge of the vapor is almost constant with time and is about twice that of the isothermal sound velocity, which i s defined from the pressure and the density of the nylon projectile af ter passing of the shock wave. The shape of the cloud is not always he mispherical but depends on the combination of the material of the proj ectile and target, and impact velocity and angle. Inside the vapor clo ud are not only the vapor but also the solid ejecta, which travel with the same velocity as the leading edge of the cloud. The temperature o f the cloud in the case of nylon impacting on nylon decreases with the power law exponent of time of -0.04 to -0.2. The light energy radiati ng from the cloud is about 10(-4) to 10(-5) times the initial projecti le kinetic energy.