  Rotor walk is deterministic counterpart of random walk on graphs. We study
that under a certain initial configuration in Z^d, n particles perform rotor
walks from the origin consecutively. They would stop if they hit the origin or
infinity. When the dimension d>=3, the escape rate exists and it attains the
upper bound of O. Schramm. When the dimension d=2, the numbers of the particles
escaping to infinity are of order n/log(n). The limit of their quotient exist
and also attains the upper bound of L.Florescu,S.Ganguly,L.Levine,Y.Peres which
equals to frac{pi}{2}. We use the results and the methods of the outer estimate
for rotor-router aggregation in L.Levine and Y.Peres' previous paper.
