A kinetic bombardment is the act of attacking a planetary surface with an inert projectile, where the destructive force comes from the kinetic energy of the projectile impacting at very high velocities. The concept is encountered in science fiction and is thought to have originated during the Cold War. Non-orbital bombardments with kinetic projectiles, such as lobbing stones with siege engines such as catapults or trebuchets are considered siege warfare, not kinetic bombardment.
Project Thor is an idea for a weapons system that launches kinetic projectiles from Earth orbit to damage targets on the ground. Jerry Pournelle originated the concept while working in operations research at Boeing in the 1950s before becoming a science-fiction writer.
Posted by Bob Wallace, who heard about this from Jerry Pournelle