Abstract
Investigations show that a time-varying δ-δ' mirror gives rise to asymmetrical vacuum radiation on its two sides, enabling one to extract propelling forces from the vacuum fluctuation. In this work, we propose a design of Casimir device to gain propulsions out of vacuum with conventional δ mirrors. We call this device a ``vacuum propellion'', which is experimentally feasible. It consists of a cavity made up of a perfectly reflective left mirror and a right mirror with time dependent transparency. All particles generated from this propellion are preferentially right-moving, so the cavity obtains a left-pointing propelling force.