| 摘要 |
A spheroidal projectile with an aerodynamically roughened surface in the nature of intersecting grooves which give a high density of roughness elements. The grooves range in size between grooves of about 0.01 inch wide and deep, spaced about 1/32 of an inch apart for a "fine" degree of roughness to grooves which are 1/16 of an inch wide and deep, and spaced 1/16 of an inch. The projectile has a mass sufficiently low so that when launched at transltional and rotational speeds obtainable by hand, Magnus forces are enhanced by the roughness, and anti-Magnus forces are made to appear by this appropriate degree of roughness, the result of which is a trajectory with pronounced multiple curves. In accordance with the preferred embodiment, a surface speed of rotation of 8 feet per second is desirable and a ball of 15 grams having a 3 inch diameter would have a spin of about 10 revolutions per second. An acceptable ballistic (or linear) launch speed for the ball is about 55 feet per second.
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