A missile or other flight vehicle has a stage separation mechanism for separating a downstream stage from an upstream portion of the missile. The mechanism includes one or more holes in fluid communication with a cavity between the upstream and downstream portions of the missile. The holes are located downstream of one or more shocks produced by one or more local variations in the outer surface shape of the missile. The one or more local variations in outer surface shapes produce the one or more shocks as the missile is flown at supersonic speeds. These shock(s) produce downstream pressure rises, and these pressure increases are communicated to the cavity by the hole(s). The increased pressure in the cavity provides a mechanism for separating the downstream stage from the upstream portion of the missile, after release of a mechanical coupling between the upstream portion and downstream stage.