Submarines, Military. Technology used

Although the first military submarine operated as early as 1775 and development continued throughout the 1800s, the submarine was really a creature of the twentieth century; it was the submarine and the aircraft carrier that defined naval warfare in that century.

The basic technology of the submarine is quite simple and has remained constant since its inception. The boat submerges by taking on water through vents to decrease its buoyancy and surfaces by expelling the water with compressed air. The outward appearance of the military submarine has remained remarkably constant throughout its modern development—a cigar-shaped hull topped by the immediately recognizable conning tower with a periscope for viewing the surface.

We can break submarine technology into five categories:
- Propulsion
- Hull design
- Weaponry
- Stealthiness
- Ancillary technologies.

The method of propulsion for the first half of the century was the diesel-electric system. Standard diesel engines were used for general operation on the surface but could not be used while submerged because of the enormous amount of air required for combustion. The submarine would only dive to attack or avoid detection, at which time the boat switched to power provided by electric batteries, charged from the diesels while on the surface. Most submarines were double hulled, with water filling the space between the two hulls while submerged.

The weapon that made the submarine useful was the self-propelled torpedo, powered by compressed air, which provided the sub with a deadly and stealthy attack. These technologies have been supported by countless others, each complex in its own right: atmosphere regeneration, escape and rescue techniques, underwater communications, weapons guidance, electronic countermeasure, and countless others, but all technologies unique to the military submarine revolved around one concept: avoiding detection by stealth.

The first significant use of submarines came in World War I when German U-boats attacked Allied shipping in the Atlantic Ocean. Losses of merchant ships increased and threatened to cripple the Allied war effort until a simple and ancient remedy was rediscovered—sailing the merchant ships in convoys. U-boats sank over 11 million tons of shipping but ceased to be a serious threat after the adoption of the convoy system.

In World War II, the critical Battle of the North Atlantic was a struggle defined by the technological accomplishments on each side as Germany’s U- boat force sought to avoid detection from the eyes and ears of Great Britain’s anti-submarine warfare (ASW) force. In the efforts at stealth and avoidance of detection, the most significant developments were the deployment of ASDIC (for AntiSubmarine Detection Investigation Committee), or sonar, followed closely by airborne radar.

The most deadly enemy of the submarine turned out to be aircraft, which could detect surfaced submarines by means of radar allowing an attack with bombs or, as the submarine dived, depth charges. The U-boats countered British radar with a radar detector called Metox that warned of attack, but the British eventually deployed a new radar using a centimetric wavelength undetectable by Metox. The Germans did not discover the use of the new radar and were slow to develop an effective counter.

U-boat losses continued to rise. As a stopgap measure the Germans deployed the schnorkel, developed before the war by the Dutch but captured by the Germans upon the surrender of the Netherlands. The schnorkel, or snorkel to the Americans and snort to the British, was a simple device—a breathing tube that could be raised similar to a periscope that allowed the submarine to run its diesel engines while submerged. While technologically interesting, its practical deployment was a failure; Allied radar could soon detect even the schnorkel protruding from the water.

The war ended before the Germans could deploy their own next wave of technology embodied by the Type XXI ‘‘Walther’’ boat, powered by hydrogen peroxide fuel and much larger battery capacity that gave it a fast underwater speed.

A submarine is only as effective as its weaponry is reliable, and World War II saw examples of massive weapons systems failures. In the Norwegian campaign of 1940, the earth’s magnetic field interfered with the operation of the U-boats’ magnetically armed torpedoes. German U-boats operating off the Norwegian coast aimed torpedoes at unsuspecting British capital ships only to hear their duds clank off the sides of the targets.

In the Pacific, American submarines were armed with hopelessly defective torpedoes that rendered the American submarine fleet useless for many months until the flawed torpedo design was corrected. When effective torpedoes reached the American subs, their effect was devastating. The Japanese never developed an effective ASW force or doctrine, and U.S. subs ran wild, destroying over 60 percent of Japanese merchant shipping and paralyzing the import-constrained Japanese economy. While less well known than the great carrier battles and island invasions, the U.S. submarine force contributed at least as much to the defeat of Japan.

The most significant single development in submarine technology has undoubtedly been the use of nuclear propulsion. The first nuclear- powered boat was the USS Nautilus, launched in 1955. Nuclear power freed submarines from the need to surface or schnorkel. Subs could stay at sea for months longer than before and stay submerged indefinitely. The drawback of nuclear power was that it was relatively noisy, and a new generation of diesel submarines remained in use through the remainder of the century, particularly in short- range roles.

The submarine also entered the area of strategic nuclear warfare, as it provided an ideal platform for long-range missiles tipped with nuclear warheads. The first launch of a ballistic missile from a submarine came from the USS George Washington in 1960.

With the security of a nation’s entire population dependent on its defense against enemy ballistic missile submarines, antisubmarine and stealth technology became even more important. Both the U.S. and the Soviet Union devoted enormous amounts of resources in research in the race to detect the other’s subs and protect their own. If the ASW-submarine contest of World War II was a battle of technology, the competition between Cold War fleets was even more so. Hull design improved tremendously; World War II subs could dive to 120 meters, and modern submarines can reach much greater depths. Hulls were also more streamlined, further increasing speed.

Weaponry diversified from earlier years. In addition to ballistic missiles and the traditional torpedo, subs began deploying sophisticated cruise missiles, first for attacking surface naval targets and, with the introduction of the American Tomahawk cruise missile, land targets.

The airplane, while still useful, gave way to the submarine itself as the most effective antisubmarine weapon with hunter-killer submarines on both sides patiently stalking the other’s missile submarines lurking deep in the ocean as far as possible from enemy bases. The use of active emission sonar fell from favor except for targeting immediately before an attack, as its use gave away the position of the attacking sub. Passive listening sonar became the preferred method of tracking an enemy boat, and hence silence became the most important defense for the submarine.

A representative example of the many developments was when ASW forces began finding subs by the use of magnetic anomaly detection (MAD), the Soviet constructed their Alfa class with hulls of nonmagnetic titanium at great expense. Unfortunately for the Soviets, the machinery of the Alfas was so noisy they could be easily located by passive sonar. Such tradeoffs and competitions existed in all facets of submarine and ASW technology.

With the end of the Cold War, the usefulness and cost-effectiveness of the nuclear submarine began to be seriously questioned, but technological advances continued. The USS Seawolf, launched in 1997, boasted a nuclear reactor fueled with liquid sodium and the Virginia class promised to be even more advanced when deployed early in the twenty- first century.

The use of the submarine and its technological advance paralleled the changes of war in world society over the course of the century. World War I began with the U-boats operated by a strict law of maritime warfare, warning merchant ship crews of their presence and patiently waiting for the embarkation of the crew in lifeboats. Well before the end of the century, nuclear submarines lurked in the depths, each waiting to destroy dozens of enemy cities without warning.