A system and method for detecting thrust in a remote object is disclosed herein. The system is suitable for use in connection with midcourse discrimination systems that distinguish actual targets of interest, such as warheads, from decoys. The system directs laser pulses at the remote object under observation. The system directs at least one initial laser pulse at the remote object to heat the surface material of the remote object and to create an outgas environment near the remote object. The system also directs at least one secondary laser pulse at the outgas environment, which creates very high peak power filaments that bombard the surface of the remote object. The filaments ablate the surface material of the remote object, ejecting mass away from the remote object at a high velocity. The ejection of mass imparts thrust to the remote object, resulting in an imparted differential velocity dependent on the mass of the remote object. The magnitude of the imparted differential velocity allows assessment of whether the remote object is a relatively massive target of interest or a countermeasure having relatively low mass.