Once a bomb has been primed, an accidental shock can cause it to explode. The US Army would like charges that can tell the difference between accidental impacts and intended ones, so it tasked Jahangir Rastegar and colleagues at the State University of New York in Stony Brook, US, with designing them.The team has proposed a system which it says could work for explosive devices that are launched before detonating, such as rocket-propelled grenades and mortars. The idea is to have the mortar "know" it has been launched, and that on the next impact it should explode.
A piezoelectric sensor in the shell turns the vibration from a shock into an electric signal. If that signal is characteristic of the launch charge, the fuse becomes primed so the next impact triggers detonation. If the shock is purely accidental, the signal will have a different signature, and the fuse ignores it.
Read the full piezoelectric fuse patent application.
Justin Mullins, New Scientist contributor