|NAVAL ORDNANCE AND GUNNERY, VOLUME 1
| F. Bombs
3F1. Bombs and bomb components
The aerial bomb provides for very efficient use of the load-carrying ability of a given plane. Only a small fraction of the weight involved must be reserved for suspension, release, and sighting equipment. On the other hand, an aerial bomb has very low initial velocity, this velocity being that of the airplane carrying the bomb at the time of release. Time of flight is relatively prolonged, and accurate computation is required to obtain hits. A partial exception exists, of course, in glide bombs with homing mechanisms. The first aerial bombs were the small, hand-thrown missiles of World War I, but 2-ton bombs are now commonplace, and even larger sizes have been standardized.
A conventional aerial bomb has three major components. The body contains the explosive charge, or it may have a chemical filler. The fin assembly is provided to keep the bomb stable in flight. A fuze serves to detonate the charge. These three elements usually are assembled into a complete round just before the bomb is loaded in or on the aircraft. A glide bomb, which is a guided missile, must in addition carry the equipment necessary for guidance.
Trends in bombing developments include the perfection of a great variety of special-purpose bombs, including some relatively small types and others of great weight; development of improved methods of tracking, sighting, and computing; development of sighting and control systems that are effective at high altitudes and under all conditions of visibility or lack thereof; and evolution of more effective methods of detonation.
3F2. Bomb classification
In terms of their fillers there are three general types of bombs: explosive bombs, chemical bombs, and inert bombs. Varieties of explosive bombs include armor-piercing, semi-armor-piercing, general-purpose, light-case, depth, fragmentation, and antiaircraft types. Chemical bombs include gas, smoke, and incendiary varieties. Inert bombs contain no explosives or chemicals, and are used in drills and in practice bombing. A number of aerial bombs are shown in figure 3F1. All bombs are painted with appropriate identifying markings.
In addition to the three major types, various encased pyrotechnic materials (not strictly bombs) are usually regarded as bomb ammunition.
|3F3. Explosive bomb types
Armor-piercing bombs (fig. 3F2) are thick walled, contain about 15 percent by weight of explosive filler, and are intended for use against heavily armored ships and heavy steel or concrete structures. They incorporate only tail fazes. The effect of a near miss with such a bomb is small, because of the small percentage of explosive contained. If used against unarmored or lightly armored ships, they are likely to pass clear through the target before detonating.
|General-purpose bombs (fig. 3F3) have medium-thick cases, contain about 50 percent by weight of explosive filler, and are used to produce blast, fragmentation, or mining effects. Appropriate targets include unarmored vessels, submarines, and land targets such as ordinary buildings, aircraft (on ground), gun emplacements, and personnel.
Light-case bombs carry a maximum explosive charge: about 75.6 percent by weight. The fuzes used function instantaneously; this is necessary, because cases rupture upon impact. Various weights have been developed, ranging from 400 to 12,000 pounds. The effect of such bombs depends largely upon blast, and to a lesser degree upon fragmentation; they are effective against light structures and personnel.
Depth bombs, intended primarily for attacks upon submarines, contain about 70 percent by weight of explosive filler, and have relatively light cases. As shown in figure 3F1, a depth bomb has a flat nose to reduce the possibility of ricochets when it is dropped into the water at small entrance angles. For attacks upon submarines, this bomb is fitted with a hydrostatic tail fuze, but an impact nose faze may also be installed if the target is a surface ship. If a nose fuze is present, it must be unarmed in making antisubmarine attacks. Depth bombs have little penetrating power, and depend primarily upon blast to produce desired effects.
Fragmentation bombs have heavy cases made up of steel rings or steel bars, and contain about 14 percent by weight of explosive charge. When such a bomb bursts, fragments from the shattered case are thrown outward at high velocity and may do considerable damage to light installations, aircraft on the ground, unarmored vehicles, and personnel.
|3F4. Fire and incendiary bombs
Fire and incendiary bombs are types of chemical bombs. Large fire bombs may be droppable fuel tanks filled with a highly flammable mixture, which is usually 94 percent of 80 or 100 octane gasoline and 6 percent napalm. Napalm thickeners gel the gasoline to a rubbery mass of such a consistency that when used in the fire bomb the resulting conflagration covers a large area, burns intensely, and lasts a long time.
As an antipersonnel weapon, the fire bomb has been found to be effective against personnel in slit trenches, dugouts, and foxholes. As an incendiary, the fire bomb has been found to be effective against wooden piers, houses, docks and waterfront warehouses, wooden surface vessels, ammunition dumps, truck convoys, and any other readily burnable target.
The average coverage from one bomb dropped on level terrain is about 300 feet long and 100 wide, when dropped from aircraft in level flight at altitudes of 100 feet and speeds of 300 knots. Higher altitudes and lower speeds decrease the coverage and vice versa.
Other incendiary bombs usually contain thermite in magnesium alloy cases. As the thermite bums, the magnesium case becomes ignited and adds to the incendiary effect.