Unexploded Shells
The fuze of a shell has to keep the shell safe from accidental functioning during storage, due to (possibly) rough handling, fire, etc., it also has to survive the violent launch through the barrel, then reliably function at the correct time. To do this it has a number of arming mechanisms, which are successively enabled under the influence of the firing sequence.
Sometimes, one or more of these arming mechanisms fails, and if the fuze is installed on an HE shell, it fails to detonate on impact. More worrying and potentially far more hazardous are fully armed shells on which the fuze fails to initiate the HE firing. This may be due to shallow, low velocity or soft impact conditions. Whatever the reason for failure, such a shell is called a blind or unexploded ordnance (UXO). The older term, "dud", is discouraged because it implies that the shell cannot detonate. Blind shells often litter old battlefields and depending on the impact velocity may be buried some distance into the earth, all remain potentially hazardous. For example, antitank ammunition with a piezoelectric fuze can be detonated by relatively light impact to the piezoelectric element, and others, depending on the type of fuze used can be detonated by even a small movement. The battlefields of the First World War still claim casualties today from leftover munitions. Modern electrical and mechanical fuzes are highly reliable: if they do not arm correctly they keep the initiation train out of line, or if electrical in nature, discharge any stored electrical energy.
Read more about this topic: Shell (projectile)
Famous quotes containing the word shells:
“It is not easy to make our lives respectable by any course of activity. We must repeatedly withdraw into our shells of thought, like the tortoise, somewhat helplessly; yet there is more than philosophy in that.”
—Henry David Thoreau (1817–1862)