Home The Institute of Space and Astronautical Science Report Dynamical Characteristics of Planetary Penetrator: Effect of Incidence Angle and Attack Angle at Impact

2. 3. SHAPE AND SIZE OF THE MODEL PENETRATOR

The penetrators used in the present experiment are scale-models of about one-fifth of the flight model, and are made of A7075 aluminum. The shapes of penetrator models are shown in Figure 5. To investigate the effect of the nose shape on penetration characteristics, two models with two different nose shapes were prepared. One is of truncated conic shape with an apex angle of 28.6° and a height of 6 cm (hereafter abbreviated as STD, Figure 5a). Note that the ratio of the base diameter to the original nose length is one-half. The other is of truncated ogive-nose, which is more streamlined than the conic nose (hereafter abbreviated as OGIVE, Figures 5b and 5c). The curvature of the ogive shape is approximately expressed by the following equation,



Fig.5.Various sharpes of penetrator models used in this experiment. (a) comical nose(STD); (b) ogive nose (OGIVE-60); (c) ogive nose (OGIVE-90). (d) A indication of (=Sb/Sa) is schematically shown.The numbers in the figure indicate lengths in mm.


......(1)
where Ln represents the nose length with no truncation, X distance from the apex, D base diameter (fixed to be 30 mm in the present experiments) and r radius at X (O X Ln). The OGIVE-60 and OGIVE-90 correspond to the cases ofLn = 60 mm and 90 mm, respectively. As illustrated in Figure 5d, is the ratio of the nose sectional area with truncation to the base sectional area. Almost all the penetrator models used in the experiment have lengths of 1 9 cm to 28 cm and masses of 320 g to 380 g, respectively, resulting from the degree of truncation and from variation in the length of cylindrical part. Although the position of the center of gravity of the model was not controlled in this experiment, it is at about a half of the penetrator length as shown in Table 1 (the off-axis coordinate of the center of the gravity is thought to be negligibly small). To measure the impact velocity by the magnet flyer method, a small piece of Sm-Co magnet is mounted inside the rear end cap.

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Home The Institute of Space and Astronautical Science Report Dynamical Characteristics of Planetary Penetrator: Effect of Incidence Angle and Attack Angle at Impact