      RVD = 0.0
      VVDOT = 0.0
      DO 20 K = 1,3
          VDOT(K) = ACC(K) - MR*X(K)/R2
          RVD = RVD + X(K)*VDOT(K)
          VVDOT = VVDOT + V(K)*VDOT(K)
   20 CONTINUE
