Rocket

Rocket is a cylindrical case of paper or metal partially filled with an inflammable composition (saltpetre 68 parts, sulphur 12 parts, charcoal, or mealed powder, 32 parts), so that a large conical hollow is left inside. The base is open or has vents in it, and the head closed. On being ignited this composition burning over the whole surface of the hollow portion at once causes a great rush of gas out of the base, thus driving the rocket forward with great and increasing velocity. Rockets are used for signalling and to carry a light line for life-saving purposes (see LIFE-SAVING APPARATUS). Early in the 19th century they began also to be used in war. Sir William Congreve in 1808 introduced iron war-rockets up to 24 lb. in weight, with thick iron heads adapted to act like a shell. They were fired from a tube and steadied in their flight by means of long sticks. In the more modern Hale rocket a rotatory motion is given by causing the gas to pass out of vents in the base bored between three projecting shields, shaped somewhat like the blades of a screw-propeller, against which it presses. The cumbrous stick is therefore no longer used, and the rocket is fired from a low trough with tripod stand, or even from the ground, by raising the head to the height necessary to give the required range, which may be as much as 4000 yards. Though extremely portable as compared with other missile weapons of similar power, rockets are so uncertain in their flight that they are not much used, except for incendiary purposes and against savages, who greatly dread them. Against cavalry they would be very useful if they could be depended on. The rocket troop of the Royal Horse Artillery did very good service in the Peninsular war, however, and ships' boats, which could not carry a gun firing a 24-pounder shell, can throw rockets of that weight into a place under bombardment. See PYROTECHNY.