by William Weir
But with all these defenses, shaped charges and still being used. And, regrettably, even relatively primitively shaped charge weapons are still putting holes in our tanks.
Chapter 41
Red Glare Everywhere: Small Rockets
Nineteenth-century rocket battery firing.
The rocket is one of the oldest of explosive weapons. The Chinese were using rockets before they — or anyone else — had guns. Rockets appeared in Europe around 1250 — again, before any Europeans had guns. Rockets may have been even more useful than guns for scaring horses (the chief effect of the earliest guns). They could also set fires. But rockets weren’t worth a hoot for knocking down stone walls, which was what interested most belligerents at that time, so they were soon dropped by most armies.
They came back into fashion in the early 19th century when an Englishman named William Congreve, impressed by rockets the Indians were using, invented an improvement. Congreve’s rockets were iron and carried a warhead of either gunpowder or incendiary material. He built several sizes, and all were stabilized by a long pole fastened to the body of the rocket. They were launched from a long ramp and used by both armies and navies. Ships using rockets had sails set back from the front of the ship, which was reserved for rocket launching, and some had chains, instead of rope, for rigging. The rocket’s back blast as always been a factor that must be reckoned with. During the Napoleonic Wars, British ships used rockets to burn down Copenhagen, and in the War of 1812, they used rockets in the unsuccessful bombardment of Fort McHenry.
Later, rockets were stabilized by either propellant gases pushing vanes at the rear of the rocket, which set it spinning, or by tail fins. Rockets were easier to move than artillery, but they were much less accurate, so they remained a secondary weapon until World War II. Changed conditions combined with improvements in rocket engines made rockets important weapons. Continued improvement after the war has led to rockets replacing guns in many situations.
This trend is particularly noticeable in navies. All the world’s huge 16-inch-gun battleships are now out of service, and their places have been taken by smaller ships armed principally with rockets and guided missiles. In the Iraq War, Coalition naval forces included four carrier battle groups, including four of the giant nuclear Nimitz class carriers, each displacing more than 93,000 tons, as well as slightly smaller carriers like the 81,990 Kitty Hawk class. There were scores of smaller ships: cruisers, destroyers and frigates. None carried many guns, and those were comparatively light antiaircraft or dual purpose guns, fast-firing lightweights for which shore bombardment was little more than an afterthought. Instead of heavy guns, the fleet carried hundreds of antiaircraft, anti-ship, and other surface-to-surface rockets in addition to cruise missiles.
For ground fighting, rockets turned out to the perfect antitank weapon for infantry. A rocket launcher has no recoil, because it’s just a hollow tube. There’s no internal pressure, as there is in a gun. All the internal pressure is in the rocket itself, so the launcher can be quite light. The bazookas, short-range point-and-shoot weapons, were fired from one man’s shoulder. There are still modernized forms of the bazooka in service, but there are also much longer ranged antitank rockets, which are guided by signals coming over a thin wire (the Brennan torpedo — see Chapter 26 — was a century ahead of its time). Other antitank rockets home in on reflected laser light. All of them are much lighter and more mobile than any kind of artillery.
World War II produced many situations that required a sudden, intensely heavy bombardment for a short period. For this, the rocket was ideal. Landing craft equipped with masses of rockets delivered more explosives on enemy beaches in a shorter time than any battleship could. Both the Germans, with their Nebelwerfer, and the Russians, with their Katyusha, laid down massive rocket bombardments on the Eastern Front. Rockets were especially important for air defense in World War II. Planes were flying higher and faster, only rockets could reach the necessary altitude, and only rockets could be programmed to home on the planes. After the war, rockets also gave the infantry a way to cope with low-flying enemy planes attempting to strafe them. Shoulder-fired rocket launchers as the United States’s Stinger now allows the dogface to fight back effectively. Unfortunately, they also give terrorists something to use against civilian airliners.
Aircraft, too, found rockets essential. German night fighters, confronted with Allied bombers flying in tight formation for mutual defense, simply launched their rockets at the formations as if the rockets were torpedoes and they were submarines attacking a convoy. In dogfights, fighter pilots on both sides used rockets extensively. A rocket packed a much heavier punch than a .50 caliber bullet or a 20 mm shell. Rockets could also be made to home in on enemy planes — to turn with them, dive with them, outrun them and blow them up.
For strafing ground targets, the rocket was also ideal. World War II ground fighting saw the obsolescence of dive bombers such as the German Stuka. Dive bombing was an extremely hazardous occupation if the enemy had any decent ground fire capability, because the bomber appeared to be almost motionless to those immediately below it. The only reason for dive bombing was that it was the most accurate way to drop an unguided bomb. Rockets had accuracy built in. The fighter-bomber (pure fighters were also becoming obsolete) would approach its target at high speed in a rather shallow dive and fire rockets when the target was in range. Rockets for antitank use, of course, had shaped-charge fillings.
During the Cold War, all the nations of the world feared the nuclear-armed intercontinental ballistic missile. They still do. Witness the flap over nuclear programs in North Korea and Iran. Although the ICBM has strongly affected nations’ political and military strategy, it has never been used. That’s not true of its smaller cousins. They have already changed the nature of war on land, sea, and air.
Chapter 42
Firing a Cannon Like a Rifle: Recoilless Guns
National Archives from Army
U.S. troops fire 75 mm recoilless gun at North Koreans in 1951.
In the armies of Napoleon and Gustavus Adolphus, cannoneers and their guns fought right up in the front lines as the infantry. That had many advantages. Front line commanders didn’t have any trouble getting fire support from the artillery. But when rifles were adopted, standing up in the front line loading a cannon meant that you probably would not get a chance to tell your grand-children any war stories.
There were some attempts to rectify the situation. Until World War II, the most successful was the trench mortar. In the First World War, French and American infantry troops used a light, low-power 37 mm gun. It was good for knocking out machine gun nests, but very little else. In the Second World War, the American Army experimented with “cannon companies,” artillerymen who dragged a 105 mm howitzer up to the front and used it to give direct fire support. The trouble was that the gun was a magnet for enemy fire, and life in a cannon company tended to be short.
The greatest disadvantages of modern artillery pieces is their weight and bulk. The carriage has to be massive and heavy to withstand the stress of recoil, even though the guns are equipped with a recoil-absorbing mechanism, which artillerymen call a recuperater. The recuperator also adds weight and bulk. If recoil could be eliminated, the gun could be smaller and lighter. The first man to eliminate recoil from a cannon was a U.S. Navy officer — a Commander Davis. A gun recoils because, as Isaac Newton stated, every action has an opposite and equal reaction. A shell is much lighter than the gun that fires it, so it travels at high speed and goes a great distance. The gun does not recoil at the same speed and, even without a recuperater, it doesn’t travel anything like the distance the shell goes. If the gun fired a missile of the same weight from each end of the barrel, there would be no recoil at all. That’s what Davis did. The missile from the rear end of his gun was mixture of lead shot and grease so, unlike the shell fired from the front end, it quickly dispersed. Davis sold his gun to the British, who used some of them on naval aircraft during World War I.<
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Recoil depends on the mass of the missile being fired times its velocity. If the Davis gun could fire a rear missile weighing half the “business” missile but at twice the velocity, recoil would still be eliminated. In calculating recoil, you have to figure the mass of the gas, as well as the mass of the missile. The mass of the gas is roughly the same as the weight of the powder charge. Some of the powder does not leave the gun in the form of gas but remains as residue. With smokeless powder, however, this is negligible, so it would be possible to eliminate recoil by ejecting only gas from the rear of the gun, provided the gas could be ejected at a high enough velocity to balance the force of the shell being fired.
Because it’s gas that’s ejected, the danger zone behind the gun is much shorter than if any kind of solid were ejected. Still, there is a fan-shaped danger zone behind these guns that may extend more than 100 feet. The gas jet also kicks up a huge cloud of dust, which makes it easy for enemies to locate the gun.
The first to put this principle to practical use was the German firm, Krupp.
In 1940, Krupp produced a 75 mm light gun for airborne troops. The gun used fixed ammunition, but the base of the cartridge case was plastic. When fired, the plastic shattered and blew out a hole in the breechblock. The hole was a venturi, a tube with a narrow center section and widened, tapered ends designed to increase the speed of gas ejected through it. That speed was carefully calculated to equal the action of the shell being fired from the muzzle. The light gun had a carriage of light alloy and motorcycle wheels. It weighed only 321 pounds, compared to 1.1 tons for the regular 75 mm field gun, but had velocity and range only a little less than that of the regular gun. The Germans used the light gun during their invasion of Crete, and it was such a success they ordered two more recoilless guns, a 105 mm and a 150 mm.
The British also produced a recoilless gun design, invented by Sir Dennis Burney. The biggest difference between the Burney and Krupp guns were the ammunition they used. The Burney gun had a cartridge case with a few large holes punched in it. These were covered by thin brass sheets that blew out when the gun was fired. The escaping gas traveled to the rear around the cartridge case and was ejected from several venturis. Burney also invented a projectile for his gun, something he called a “wallbuster,” intended for use against fortifications. The wallbuster developed into the HESH or HEP shell (see Chapter 39) and turned out to be a good antitank round. It is less effective with modern layered armor, because that type does not transmit shockwaves through the metal so well, and the explosion of a HEP shell is less likely to break off significant “scabs” of metal.
Neutral Sweden got into recoilless gun design early, bringing out a 20 mm antitank gun in 1942. It used fixed ammunition with a plastic base cartridge case similar to the Krupp gun. It followed this rather ineffectual weapon with a much more formidable 105 mm gun.
The United States developed a different recoilless gun. As the others did, it used fixed ammunition, but the cartridge case was punctured with many small holes, instead of a few big ones, as in the Burney gun. It was nicknamed the Kromuskit from the names of its designers, Kroger and Musser. The shell’s driving band was pre-engraved to fit the gun’s rifling. That meant that less gas pressure was needed to send the shell on its way at a decent velocity, and that meant that the barrel of the gun could be lighter. Also, a larger proportion of the propelling charge would actually be pushing the shell. Earlier recoilless guns needed a powder charge five times heavier than used in a standard gun — most of the burning gasses being ejected through the venturi rather than pushing the shell.
The first Kromuskit was a 57 mm gun weighing only 35 pounds. It could easily be fired from one man’s shoulder. The next one, a 75 mm, weighed 115 pounds — a bit heavy for shoulder firing, but usable on a machine gun tripod.
All of these recoilless guns fired shaped charge as well as ordinary high explosive shells. The Kromuskit guns also fired white phosphorus shells, which were both antipersonnel and smoke shells, and canister shot, which turned them into giant shotguns for use against personnel at close range.
Most of the recoilless guns lost some of the efficiency of their shaped charge antitank shells because they were rifled. Spinning decreases the power of the jet blast of a shaped-charge explosion. The Swedes avoided that trouble with their 84 mm Carl Gustaf recoilless gun. The shell is fitted with rotating bearings. The rifling spins the bearings, imparting enough gyroscopic stability to keep the projectile on course, but the core, containing the shaped charge, does not spin.
At 38 pounds, the Carl Gustaf is light enough to fire from the shoulder and is able to penetrate 15.75 inches of homogeneous armor at a range of 500 yards. A second Swedish recoilless gun, called the Miniman, is disposable. Fire the one shell packed in it and throw it away. It’s a smoothbore, firing a shell stabilized by tail fins, has a range of 250 yards and can penetrate 11.8 inches of homogenous armor. It weighs only 6.31 pounds.
Germany also has a disposable recoilless gun. Like the Swedish model, it’s a smoothbore firing a finned shell. But no gas escapes from either the muzzle or the rear end. The propelling charge moves two pistons to the front and to the rear. The front piston throws out the shell and the rear pistol ejects a solid counterweight that is designed to rapidly disperse. Presumably, this makes the gun less visible on firing than the traditional recoilless gun. The German gun, called the Armbrust, is also light enough to fire from the shoulder.
Recoilless guns give the infantry direct fire artillery for the first time in centuries. They are available for any job that calls for something heavier than rifle or machine gun fire. Especially, they are available for antitank and — although the situation has not yet occurred — anti-helicopter work.
Chapter 43
Eyes and Ears: Sonar and Radar
National Archives from Coast Guard
Coast Guardsmen drop depth charges on German submarine located by sonar in 1943.
In the early years of the submarine, it seemed that the only problems the undersea craft would have would be its own mechanical deficiencies. There was no way anyone on the surface could detect the presence of a submerged boat.
In the first part of World War I, the object of the British Navy was to catch German U boats on the surface. The main anti-submarine weapons were the destroyer and the “Q ship,” a converted merchant ship, often carrying a cargo of lumber to inhibit sinking, with hidden deck guns. The former cruised the waters haunted by submarines and tried to catch one on the surface. Because the early subs had to spend most of their time on the surface, that task is not as hopeless as it sounds. The latter was a seagoing booby trap. To save on torpedoes and to comply with accepted standards of decency, subs in the early days of the war often approached freighters on the surface, told the crews to abandon ship and then sank them with gunfire. The Q ships aimed to attract these surfaced submarines and sink them with its guns. But after a few Q ship mis-haps, submarine commanders just torpedoed all ships while submerged.
The first step toward the detection of a submerged U boat was the hydrophone. Hydrophones could pick up the sound of a submarine’s engines, but there were two big drawbacks. First, the hunter ship had to shut down its own engines so it could hear the subs. Second, one ship could not locate the sub by itself. Several ships working together were needed to get a rough approximation of the sub’s location. Once that was found, the navy ships would attack with depth charges.
The best anti-submarine measure in the First World War was the convoy system, but not because convoys made it easier to locate or destroy U boats. It was because the convoy system bunched freighters up. Previously, the U boats waited for a freighter to come along. If its torpedoes missed, another ship would be along soon. A submerged submarine was about the slowest craft at sea. It couldn’t catch up with or even keep up with the slowest freighter. Convoys eliminated the steady stream of ships steaming across the Atlantic. U boats had to wait a long time between targets, and when a convoy appeared, it was guar
ded by naval ships. If the U boat were not positioned just right, it might miss all the ships in the convoy, and it was too slow to make up for poor positioning.
In the next war, the submarines were bigger, faster, and sturdier, but their enemies had something new, too. The British called it asdic; the Americans called it sonar. Basically, sonar sends beeping sounds into the water and listens for echoes caused by other objects in the water. An experienced sonar operator could distinguish between the echoes from a U boat or a whale. The convoy escorts also had better hydrophones, and whales don’t make engine and propeller noises.
Locating subs was also helped by another, more sophisticated method of detection: radar. Radar used radio waves instead of sound waves, but it, also, relied on echoes. The first important use of radar was in the Battle of Britain.
Britain had radar stations all along its shore. They were able to locate German planes long before they were in sight, allowing the British fighter command to concentrate its interceptors to meet the threat. The Germans had a primitive form of radar and had no idea that the British had any, much less the more advanced form they were actually using.
British scientists continually improved their radar devices. They made some small enough to be installed on ships. That further complicated life for subma-riners. Radar could “see” in the dark, and it could “see” at much longer distances than human eyes. Submarines could no longer travel on the surface at night in safety, as they once did. It got worse. Radars became precise enough to “see” periscopes; they became small enough to install on airplanes. In daylight, unseen planes swooped out of the clouds and bombed surfaced submarines. At night, a surfaced submarine could be located by a plane and bombed before its crew even knew they were under attack. Airborne radar became operational in 1943, the year a German writer called “the year of the slaughter of the U boats.”