The Forgotten History of the Submarine: From Bushnell's Turtle to Nuclear Boats

The submarine occupies a strange position in technological history. Conceptually it is one of the oldest machines anyone seriously proposed: Cornelis Drebbel demonstrated an oar-powered submersible on the Thames in 1620, rowed by twelve men with snorkels for air. Practically it took until the 1950s for submarines to become genuinely useful military platforms, and the engineering story of the intervening 330 years is a long sequence of partial solutions to interlocking problems that turned out to be much harder than they looked.

The four problems are: how to make a hull that resists pressure at depth, how to maintain controlled buoyancy, how to propel the boat without combustion, and how to provide breathable air for the crew. Each was solved separately at different times, and the solutions had to be combined before submarines became more than novelties. The propulsion problem was the last to be solved properly, and the air problem was the one that nobody thought was hard until it became the limiting factor.

The Turtle and its descendants

David Bushnell's Turtle (1775) was a one-man wooden submersible designed to attach explosive charges to British warships during the American Revolution. It had two hand-cranked propellers (one for vertical motion, one for horizontal), brass hand pumps for ballast water, and a six-foot diameter hull shaped like two tortoise shells joined together. Sergeant Ezra Lee piloted the Turtle in the only documented combat attempt, in New York Harbor in September 1776, and failed to attach the charge to HMS Eagle — the auger meant to drill into the hull couldn't penetrate the copper sheathing. The vehicle worked as a vehicle; the weapon delivery system did not.

Robert Fulton's Nautilus (1800), built in France, improved on the Turtle in most respects: copper-clad iron hull, sail-and-propeller hybrid propulsion, working diving plane controls, and a crew of three that could stay submerged for several hours. Fulton demonstrated it to Napoleon, then to the British, then to the Americans, and was rejected by all three. Submarines were considered ungentlemanly weapons.

The American Civil War produced the H.L. Hunley, the first submarine to sink an enemy warship. The Hunley used a hand-cranked propeller turned by seven crew members and carried a single spar torpedo (an explosive charge mounted on a long pole). On 17 February 1864 it rammed and sank USS Housatonic outside Charleston Harbor and then itself sank with the loss of all hands. The Hunley had killed three previous crews in trials before its successful mission. The fundamental engineering problem of the era is captured by that statistic: even when the boats worked, the operational risk was higher than any weapon they could deliver.

The propulsion problem

The Turtle and the Hunley were powered by human muscle. Fulton's Nautilus added sail power for surface operation but reverted to muscle for diving. None of these arrangements gave the boats useful endurance or speed.

The first practical submarine propulsion was electric. John Holland's Holland VI (1900) carried a 60-horsepower gasoline engine for surface operation and a 50-horsepower electric motor with battery banks for submerged operation. Submerged endurance was a few hours at slow speed; surface endurance was hundreds of miles. The Holland VI was bought by the US Navy as USS Holland and became the template for every diesel-electric submarine for the next 50 years.

The diesel-electric arrangement had a structural limitation: the boat could only operate submerged for as long as the batteries lasted. After that it had to surface to run the diesel engines, which needed air. World War I U-boats spent most of their time surfaced, diving only for tactical engagement. The submarine was effectively a torpedo boat that could disappear briefly, not a vessel that lived underwater.

The Walter cycle (Hellmuth Walter, 1930s-1940s) used hydrogen peroxide as an oxidizer, allowing diesel engines to run submerged. Several Walter-cycle U-boats were built late in WWII, including the Type XVIIB, but the technology was unstable and produced enormous heat. After the war, the Walter approach was studied by all major navies and abandoned by all of them.

The Snorkel (Schnorchel), introduced on German U-boats in 1944, was a less elegant solution to the same problem: a tube that ran from the diesel engine to the surface, allowing the boat to run diesels while submerged at periscope depth. The snorkel made surface running optional but kept the boat tethered to the surface in a different way.

Nuclear propulsion was the eventual answer. USS Nautilus (SSN-571), commissioned January 1955, was the first submarine that could remain submerged indefinitely. Its pressurized water reactor produced enough power to run the boat at speed for years between refuelings, and the closed-cycle reactor needed no air. Nautilus crossed under the North Pole in August 1958, demonstrating the operational capability that nuclear propulsion enabled. From that point onward, military submarines were either nuclear-powered (with operational profiles that diesel-electric boats couldn't match) or diesel-electric coastal boats (cheaper, quieter at low speed, with limited submerged endurance). The major powers settled into nuclear; smaller navies stayed with diesel-electric.

The air problem

A submerged submarine needs to do three things with its atmosphere: provide oxygen for the crew, remove the carbon dioxide they produce, and remove other contaminants (CO from cooking, hydrogen from the batteries, various organics from machinery and humans). On Bushnell's Turtle the solution was to surface every twenty minutes; the boat couldn't stay down longer because the operator would suffocate.

For the diesel-electric era, the air problem was solved by surfacing frequently. The boat ventilated when it surfaced, and submerged operations were limited to whatever the air would support — typically a few hours before CO2 became a problem. This was acceptable when the boat surfaced often anyway.

Nuclear submarines surface rarely, and the air problem became central. Modern submarines use electrolysis cells (splitting seawater into oxygen and hydrogen) to produce oxygen, monoethanolamine scrubbers to absorb CO2, and catalytic burners to handle hydrogen and CO. The scrubbers and electrolysis cells need to run continuously; a failure in any of the systems shortens the time the boat can stay submerged. The atmospheric chemistry became one of the limiting reliability issues for nuclear submarines, and remains so today.

The pressure hull and depth

The depth a submarine can operate at is limited by its hull. Pressure increases by one atmosphere per ten meters of seawater, and the hull has to resist that pressure without buckling. WWI U-boats had operational depths around 50 meters and crush depths around 70 meters. WWII Type VII U-boats reached 200 meters in some emergencies. Modern attack submarines have classified test depths thought to be in the 400-700 meter range.

The hull material progressed from mild steel through high-tensile steel to HY-80 (US, 1960s) and HY-100 (later). Titanium hulls were used by the Soviet Alfa class (Project 705, 1970s), allowing test depths of perhaps 800 meters but at enormous cost — titanium welding required argon-flooded shipyards because titanium reacts with atmospheric nitrogen at welding temperatures. The Alfas were technically remarkable and operationally problematic, with reactor and metallurgical issues that limited their service life.

The depth race effectively ended in the 1970s. Going deeper produces marginal tactical benefit and substantial engineering cost; modern submarines optimize for quietness rather than depth.

The deeper observation

The submarine's history follows a pattern common to transformative technologies: the basic concept is articulated centuries before it becomes practical, partial implementations exist for generations, and the breakthrough comes from solving the least obvious of the contributing problems. For submarines, the propulsion question was visible from the start and discussed in every proposal from Drebbel onward. The atmospheric question was almost invisible until nuclear propulsion made it the binding constraint. The pattern recurs in aviation (where the engine problem dominated discussion until the control problem turned out to be harder), in spaceflight (where propulsion got most of the attention until life support and reentry became the binding issues), and in computing (where hardware was the visible problem until software became the limiting factor).

The submarine that operates in 2026 is the product of three centuries of incremental work on four interrelated problems, with the final synthesis coming from a completely different field — nuclear engineering — than the people who first proposed the concept could have imagined. The Hunley's seven-man crew turning a hand crank in 1864 and the 130-man crew of a Virginia-class submarine in 2026 are doing the same job: staying underwater, moving where they want to go, and coming back. The intervening engineering is what made the second case routine and the first case fatal.