Ablative armor is armor which prevents damage through the process of ablation, the removal of material from the surface of an object by vaporization, chipping, or other erosive processes. In contemporary spacecraft, ablative plating is most frequently seen as an ablative heat shield for a vehicle that must enter atmosphere from orbit, such as on nuclear warheads, or space vehicles like the Mars Pathfinder probe. The idea is also commonly encountered in science fiction. Ablative armor is distinct from the concept of reactive armor which is actually in common use in modern armored vehicles.