peer reviewed ; Ballistics and fracture mechanics are important disciplines for understanding the variables that influence the breakage of lithic armatures on impact. In particular, kinetic energy and angle of impact have been judged to be key variables for understanding impact fracture formation. In this presentation, we take the investigation of these parameters a step further and explore the variability in kinetic energy and the direction of applied stress. We do this for each of the four modes of propulsion traditionally considered relevant for the Palaeolithic (bow, spear-thrower, hand-cast spear, thrusting spear). Our goal is to evaluate whether each propulsion mode produces a reactional impact stress that is sufficiently distinct to offer clues to the propulsion mode on the basis of the fractures on archaeological stone projectiles