Supersonic Aerosol Deposition (AD) is an additive manufacturing technique wherein particles, dispersed in a gas, are accelerated through a nozzle and impacted on a substrate at supersonic gas velocities (gas velocity Mach numbers often approaching 5). It is well established that AD can yield dense coatings from metal and ceramic particles with little-to-no substrate damage, and without the need to heat the substrate. However, little is actually known about particle trajectories in AD. The drastic reduction in pressure leads to particles experiencing drag in a unique Knudsen number-Mach number regime where the drag coefficient was previously unknown. This presentation will overview our groups work in (1) using direct simulation Monte Carlo (DMSC) to develop an appropriate drag coefficient for particles in AD processes, (2) utilizing this drag coefficient to examine particle trajectories in AD processes with a de Laval slit nozzle, and (3) demonstrating that the particle impact velocity correlates with the extent of particle fragmentation for SnO2 nanoaggregates impacting onto Al2O3 substrates. Trajectory simulations show that for any given nozzle geometry, there is a particle size of maximum velocity; larger particles are insufficiently accelerated, while smaller particles are decelerated by the shock at the substrate surface. This peak velocity is typically limited to ~500 m s-1 using air and N2 as the process gas. We have also found that it is possible to inertially focus particles in AD, suggesting that highly monodisperse particles can be used to deposit with extremely narrow linewidths (on the order of the particle diameter).