  We consider the steady-state nonequilibrium behavior of mesoscopic
superconducting wires connected to normal-metal reservoirs. Going beyond the
diffusive limit, we utilize the quasiclassical theory and perform a
self-consistent calculation that guarantees current conservation through the
entire system. Going from the ballistic to the diffusive limit, we investigate
several crucial phenomena such as charge imbalance, momentum-resolved
nonequilbrium distributions, and the current-to-superflow conversion.
Connecting to earlier results for the diffusive case, we find that
superconductivity can break down at a critical bias voltage $V_\mathrm{c}$. We
find that $V_\mathrm{c}$ generally increases as the interface transparency is
reduced, while the dependence on the mean-free path is non-monotonous. We
discussthe key differences of the ballistic and semi-ballistic regimes to the
fully diffusive case.
