Why Were Submarines So Dangerous to their Inventors?

A dangerous combination of wishful thinking and a pronounced misunderstanding of the physical world largely characterized submarine development prior to the year 1900. At sea level, water is some 800 times as dense as air. However, unlike air, water is not compressible, meaning that any descent into the depths brings pressure increases with crushing exactitude. Even a few feet below the surface, this pressure creates marked changes in the way that physical objects behave, including the human body. Pure oxygen—deliriously accepted by the human body at surface level—is potentially fatal in a depth as little as six feet. The excess capacity of oxygen in tissues caused by breathing the gas under pressure causes violent spasms, unconsciousness and death. Likewise, the inert gas nitrogen causes a dangerous euphoria at depths greater approaching just 100 feet. As the average depth of Earth’s oceans is a staggering 12,500 feet, it is no small wonder that we know less about our own depths than we do about the dark side of our moon.

Mechanical objects fare little better. There exists an old axiom held by those who work in the deep ocean; the cable-layers, the explorers, fossil-fuel prospectors and treasure hunters. Don’t put anything into the ocean that you can’t afford to loose. It’s an exaggeration, but it reflects the inherent uncertainty in any maritime enterprise; even in this age of technology. No sealed object can resist the pressure of the sea perpetually. The ocean is a cold, dark and corrosive environment, and fewer angels could dance on its razor-thin margin for error than the head of a pin.

As such, submarines could never have developed in the organic fashion as ships, where individual advancements and innovations built a base of civil knowledge over years, decades and centuries. From a standpoint of cultural evolution, our modern conception of seagoing vessels could easily be traced to a rude floating log pushed across a still body of water by muscle-power alone. Imagine that log is combined with a paddle, then hollowed out to create a lighter, longer-lasting vehicle. Sails could be added to catch the wind, and branching tracts of invention created skin-covered frames, woven-reed canoes, paddle-driven outriggers and overlapping-board longboats. Power sources advanced from simple muscle to paddles to sails and eventually fossil fuels. Ships slowly became larger, sturdier, capable of serving as floating homes first for hours, then days and eventually months and years. Hard tack, however weevil-ridden and unappetizing, could be eaten months after it was created. Citrus prevented the dangerous onset of scurvy, a disease that had previously decimated entire crews with loss of strength, hair and teeth before they eventually succumbed to creeping death. These advancements may have taken millennium, but none of them had to be made in concert, nor were any individual inventions necessarily the sole cause of fatal accidents if they catastrophically failed.

Similarly, the development of diving is a poor parallel to that of submarines. Like our first crude marine transportation, the floating log, diving started with skin diving. This was the simple act of holding one’s breath and swimming beneath the surface. Unaided, accomplished skin divers can do as deep as 40 feet, sometimes a few feet deeper. Diving bells extended that distance further, as divers could exit from and return to a sealed bubble of compressed air held underneath a sealed vessel. Armored diving suits were essentially an extension of the same technology, a miniature diving bell worn atop a diver’s head and filled with a constant flow of pressurized air. Equalization between the air pressure inside the suit and the was vitally important. Too much, and the diver’s suit would inflate like a balloon, turning their negative buoyancy into positive and rocketing them towards the surface with a bad case of ‘the bends.’

The bends were a horrifying and oftentimes fatal affair. At pressure, nitrogen gas slowly accumulates in human tissues. If the pressure is let off slowly enough, the gas naturally escapes the tissues. If the pressure is suddenly reduced, the effect resembles a shaken bottle of soda—too much pressure, and when the cap is removed the bubbles rapidly expand. The same process occurs within the human body. Nitrogen bubbles rapidly expand in joints and muscle tissue, causing unbearable pain. Air bubbles can travel into the brain, killing the diver within moments. Survivors can crippled for life with intense pain or paralysis.
Opposite of this terrible condition is ‘the squeeze.’ When the air pressure becomes inadequate due to ice in the air supply tube, a ruptured tube, or failure of the surface pump, the oceanic pressure has nothing to resist it but the fragile body of the diver. British divers wore wicker armor inside their suits to disperse and protect against small variations in air pressure, but nothing to prevent a full-on case of the squeeze. The diver would suddenly not be able to draw in a lungful of air against the pressure of the ocean. At depth, the force of ocean pressure could potentially squeeze a diver’s entire body into the helmet of his suit, even into the tube itself.

By the dawn of the 19th century the development of the cannon turned sailing ships from troop transports to veritable superweapons in their own right—with a price tag to boot. In the 1700’s, building just a handful of capital ships could tap out a kingdom’s coffers for an entire year, and then mortgage it to near perpetuity.

Cannon advancements came as swiftly as they did for the sailing ships they were mounted upon. Long, light guns capable of engaging at great distance eventually fell from favor, giving the rise to shorter-range, heavy ponders. Lightweight, high-velocity cannon shot could pierce a perfectly round hole in a ships hull while retaining the momentum to do the same through the other side of the ship, while slower, heavier shot shattered hulls and bulkheads, propelling razor-sharp wood splinters into crewmembers. The huge, ugly holes could not easily be plugged, and the crews would have to cope with the additional hazard of a red-hot ball of iron rolling on the deck, setting fires and snapping ankles.

Chain- and bar-shot, or two cannonballs connected with a metal chain or rod, took out rigging. Grape-shot consisted of lightweight cans of grape-sized iron pellets, and acted like a short-range shotgun blast capable of clearing entire decks of men with one well-placed shot. Mortars and other siege guns could fire shells at a high arc, laying waste to garrisons and cities desire their tall fortifications. These sailing military superweapons, when working in concert and properly equipped, rivaled any terrestrial fortress. They could lay siege to entire port cities and garrisons, and any vessels foolish enough to approach them faced not only the powerful long guns, but a steady rain of sniper fire from marines stationed in the ships’ rigging.
Few sailing vessels were unaffected by the development of their military counterparts. Even before the ages of exploration and colonialism, sailing ships boats tall hulls to make boarding difficult, and rows of iron and bronze guns meant to dissuade attack, if not to outright repel it. In these ages, military and civilian vessels differentiated in the quality of their guns, the readiness of their gunpowder and the size of their crews but little else.

Clever tactics could sometimes break sieges, whether by utilizing fire ships (ships covered with tar, set alight and pushed into enemy convoys,) sneaking ordnance to higher ground, sabotage or outright engagement. These tactics aside, lesser powers could rarely match or break these sieges; there were few effective guerilla tactics capable of taking on a superior foe. Thus was the initial attraction of the submarine, a vessel that could, unencumbered by a support team or an air hose, surreptitiously engage larger surface vessels, attach limpet mines or sabotage hulls, then sneak back to shore undetected.

However, the development of the submarine would operate to a largely alien collection of physical standards. Several key innovations would need to be developed simultaneously, all of which would need to work in perfect concert. The learning curve of such a submarine vessel was extraordinarily steep, as their brave inventors rarely outlived even minor mistakes or miscalculations.

Though these initial creations are now generally thought of as submersibles, their inventors and contemporaries forever enshrined them as submarines. The difference is slight, but important. A submersible is a hybrid vessel, largely designed to operate on the surface, but capable of limited underwater passage. A submarine, however, is an underwater vessel designed for near indeterminate underwater passage. Despite this definitional conflict, the underwater vehicles described in this narrative will be referred to as submarines.

But what does a submarine require to be a submarine? As previously discussed, several key components would need to be independently developed, and yet work perfectly and in concert during application. First and foremost, a submarine must be watertight. The process of creating a watertight vessel was more difficult in practice than in concept. Early submarine inventors had no way of understanding how the physical properties of their building materials would behave under pressure. The earliest of them created with wood, caulks and greased leather, a technology that could barely keep up with the requirements of a small sloop, not to mention an underwater vessel. Even sailing ships required a near-constant use of bilge pumps to keep up with their ever-flooding vessels.

The age of industry developed the riveted boiler, a ready-made pressure vessel. Imaginative inventors could see how the airtight properties of a well-built boiler had possible submarine applications. Though overlapping iron plates bound together with rivets was a deeply flawed technology for underwater application, builders are perpetually limited by the technology of their times, and a better method of sealing plates together would not exist until the development of welding decades later.

The vessel would also need to be large enough to contain a volume of air adequate to sustain the life of the crew for at least a few hours. Even if the dive was meant to last a few minutes, at least a small margin of error had to be built in. Before the discovery of carbon-dioxide absorbing materials, it was a given that every breath of exaltation would slowly poison their air supply, first leading to splitting headaches, tired stupor, and eventually unconsciousness and death.

A ballast system was also essential. The early builders were clever enough to understand the basics of buoyancy, the amount of water displaced by their fragile vessels. Admit water into a specialized tank or vessel (or in some cases, into the bilge of the vessel itself,) and their invention would sink—if properly designed. Expel water, and it would rise. Some early designs used drop-weights, where rock ballast would be released once the sub reached the desired depth. Though simple, this method is still utilized by the very deepest diving submersibles, where pumping out a water ballast against the intense pressure of the ocean is either a battery-sucking enterprise or otherwise inefficient.

Propulsion was the final key. Experimental designs could simply descend to the bottom and then return, but to be effectual in any practical sense, the submarine must have some means to move under power. Initial experimentations with oars and paddlewheels were inefficient at best, as both modes of propulsion are designed to take advantage of the extreme friction differential between air and water. A oar dips down into the water, where it experiences much resistance when moved. Raised from the water, it can easily slip through the air to return its original position. When underwater, even an oar turned to slice through the water like a knife experiences tremendous hydrodynamic resistance, a paddlewheel without the ability to reorient the paddles doubly so.

Propellers are the natural solution to this problem, but effective power sources (such as fossil fuels, batteries and compressed air) were not developed until the closing years of the 19th century. Previous to that, all submarines were propelled by the muscle-power of their crews. Given the incredible weight of even the smallest submarines, their generally unfavorable hydrodynamic properties, and the oxygen requirements of a physically active human, this was a wholly inadequate mechanism of propulsion even in ideal circumstances.

Complicating the matter is the concept of propulsion is the free-surface problem, a buoyancy issue experienced by all submarines. Despite depictions to the contrary, submarines are perpetually either floating to the surface or sinking into the depths. Occasionally they may do both simultaneously, where one end rises and the other sinks, causing a potentially catastrophic situation. Though an experienced hand at the ballast system may reduce this natural phenomenon to a negligible minimum, a more practical solution is forward momentum. The submarine is balanced to slightly float—a vital configuration in case of emergency—with the diving planes set to negative. Just like the forward momentum of an airplane causes it to rise above the surface, the forward momentum of a submarine causes it to dip below the waves. Should an emergency occur and the propulsion cease, the sub would (theoretically) gently rise to the surface.
The military advantages of a fully operational submarine were clear. It could be a cunning, devious tactic to use against the super-weapon of the time. In a word, it could be brilliant. Tall, heavily armed capital ships blockading the ports of lesser powers would suddenly have to contend with the ultimate guerilla weapon, a vessel that could navigate, undetected, to point-blank range, attach a gunpowder mine to the hull of the target warship, then slip away into the darkness. It would be one of the first truly asymmetrical weapons to be deployed at sea.

The concept of a game-changing weapon enthralled centuries of inventors and thinkers. It is said that all great theorists and inventors stand on the shoulders of giants, their small contributions to a chosen field of study being made possible by the knowledge passed on by previous generations. This was not so in the case of underwater exploration, the first submariners would set forth to explore the very limits of humanity’s interaction with the abyss, and pay for each milestone with headstones.