Collisional Spin Up of Nonspherical Asteroids

We investigate the spin up of nonspherical asteroids by successive random collisions with other smaller asteroids. The spin-up rates are calculated for ellipsoidal and spherical bodies of the same mass. Then, we derive the relative spin-up efficiency, that is, the ratio of the spin-up rate of the ellipsoidal body to that of the spherical body. We suppose a collisional process in our model different from that adopted in the previous works. The results show that ellipsoidal bodies can spin up more rapidly than spherical bodies.