  We model a circular mass-transferring binary system to calculate the exchange
of angular momentum between stellar spins and the orbit due to direct impact of
the mass transfer stream onto the surface of the accretor. We simulate mass
transfer by calculating the ballistic motion of a point mass ejected from the
$L_1$ point of the donor star, conserving the total linear and angular momentum
of the system, and treating the stars as uniform density spheres with main
sequence radii determined by their masses. We show that, contrary to previous
assumptions in the literature, direct impact does not always act as a sink of
orbital angular momentum and may in fact increase it by facilitating the
transfer of angular momentum from the spin of the donor to the orbit. Here, we
show an example of the exchange of angular momentum, as well as a measure of
the orbital angular momentum changes for a variety of binary star systems with
main sequence components.
