  The time of protostellar wind breakout may be determined by the evolution of
the infalling flow, rather than any sudden change in the central engine. I
examine the transition from pure infall to outflow, in the context of the
inside-out collapse of a rotating molecular cloud core. I have followed
numerically the motion of the shocked shell created by the impact of a stellar
wind and infalling gas. These fully time-dependent calculations include cases
both where the shell falls back to the stellar surface, and where it breaks out
as a true outflow. Assuming a wind launched from the protostellar surface, the
breakout time is determined in terms of the parameters describing the wind
(Mdot_w, V_w) and collapsing cloud core (a_0, Omega). The trapped wind phase
consists of a wind sufficiently strong to push material back from the stellar
surface, but too weak to carry the heavy, shocked infall out of the star's
gravitational potential. To produce a large-scale outflow, the shocked material
must be able to climb out of the star's gravitational potential well, carrying
with it the dense, swept-up infall.
