Visual Signaling

by United States. Army. Signal Corps

ROCKETS AND SHELLS.

Two distinct kinds of rockets and shells are issued, one of which is adapted to day and the other to night signaling. Shells and rockets of the amber smoke type with parachutes are used in the daytime, while shells (red and white) and sequence rockets are used at night.

Fig. 11.—Signaling rocket and accessories.

Fig. 12.—Signaling shells.

Description.—The shells are all single shot and are fired from a 5-inch portable mortar, attaining a height of about 550 feet. The report of explosion can be heard at varying distances up to 5 miles, depending on weather conditions. The parachute attached to the smoke shell suspends a small light wooden tube which, after ignition, emits smoke for from four to six seconds. The red and white shells, on bursting, discharge a shower of red and white fire which can be observed for some time, in fact almost until the sparks fall to the ground.

Rockets for both day and night signaling are equipped with parachutes. The smoke rocket is of similar construction to the smoke shell. The sequence rocket is so arranged at the base that threaded sections of combustible material burning either red or white can be attached to it. Rockets ascend about 700 feet.

Each rocket and shell is supplied in a cylindrical sealed tin can, which also contains a port fire, wind matches, and for the rockets a stick in four sections. On the outside of the can is a label designating the kind of shell or rocket therein contained. These cans are easily opened by pulling a ring and require no special opening tool.

Operation.—In firing shells the mortar should be surrounded by earth or sand, preferably placed in sacks. The fuse for all shells is very rapid and should be ignited by attaching the port fire to a long stick.

All of the old type Signal Corps mortars, originally designed to withstand a pressure of 1,000 pounds per square inch, and made of ordinary iron pipe, are considered unsafe and should be immediately destroyed. The new mortars, recently made for the Signal Corps by the Ordnance Department, are of cold-drawn steel having a tensile strength of 6,000 pounds per square inch, which is more than the maximum pressure for firing any of the Signal Corps bombs. They are stamped "Signal Corps, U. S. A., Model 1907," or "Rocket Gun, Watertown Arsenal, 1907."

The sequence rocket is prepared for use by attaching red or white sections to the base in such a combination as to form letters of the alphabet which it is desired to use. Letters containing the same color in sequence are very difficult to read and should be avoided whenever possible. If necessary to use them, blank sections furnished for the purpose should be inserted between the units. The base of the rocket will secure six units.

When rockets are to be fired the sticks must be firmly attached, the rocket placed upright in a trough, upon a frame, or against a post. If the fuse is beneath the paper covering the "choke" orifice, the paper should be torn off and the rocket ignited by a port fire. In the rockets now used the fuse extends through the covering and can be lighted direct. If the night be damp this fuse should be exposed only a moment before the rocket is fired. If several rockets are to be fired in succession it is well to prepare them all at the same time, and to have them all stood upright, but each separated from the other at a distance of at least 6 feet, else one may ignite the other accidentally. In firing for chronosemic signals, one rocket ought to be kept ready upon the frame and in reserve, to be fired in place of one that fails.

If a rocket misses fire it is to be taken from the stand and laid on the ground. Its place is at once supplied by a similar rocket, fired in its stead. The failing rocket is laid on the ground pointed away from the station in order that if it has only hung fire and should afterwards ignite it may not disarrange the signal shown or injure any one of the party. If the wind blows freshly the rocket to be fired should be inclined slightly against the wind.

Signal rockets and shells are furnished in sealed cans and should not be removed therefrom until ready for use. Strict economy should be observed in the use of these articles and on no account should they be used for purposes of display.

Employment.—Rockets and shells are especially valuable in making preconcerted or emergency signals. On account of the great amount of ammunition required it is impracticable to spell out messages with them. These articles should be supplied to outposts, detached stations, etc., to be used for signaling the approach of the enemy or the happening of unexpected events, the necessity for promptly knowing which is important.