  Collisional fragmentation is shown to not be a barrier to rocky planet
formation at small distances from the host star. Simple analytic arguments
demonstrate that rocky planet formation via collisions of homogeneous
gravity-dominated bodies is possible down to distances of order the Roche
radius ($r_\mathrm{Roche}$). Extensive N-body simulations with initial bodies
${\gtrsim}1700$ km that include plausible models for fragmentation and merging
of gravity-dominated bodies confirm this conclusion and demonstrate that rocky
planet formation is possible down to ${\sim}$1.1 $r_\mathrm{Roche}$. At smaller
distances, tidal effects cause collisions to be too fragmenting to allow mass
build-up to a final, dynamically stable planetary system. We argue that even
differentiated bodies can accumulate to form planets at distances that are not
much larger than $r_\mathrm{Roche}$.
