Triton 3300/3 Submersible: A Walkthrough of DEEP's Deep-Sea Submarine

This lecture introduces fundamental physics concepts including the MKS unit system (meter, kilogram, second), significant figures for precision in measurements, and the distinction between mass and weight. It covers motion along a straight line, defining average velocity as total distance divided by time interval, and instantaneous velocity as the limit of average velocity as the interval approaches zero—a concept fundamental to differential calculus. The lecture traces the historical development of calculus, noting it was independently invented by Isaac Newton and Gottfried Wilhelm Leibniz in the late 17th century, with Leibniz's notation (dx/dt) becoming the standard used today.

本讲座系列系统介绍杨振宁先生对现代物理学的代表性贡献，本期聚焦于李-黄-杨硬核玻色气理论（1957年）。该工作研究了硬球玻色气体的量子行为，引入伪势方法以处理粒子间短程强相互作用，避免直接求解复杂多体波函数。该方法通过有效势替代真实硬核排斥，使理论计算在保持物理本质的同时变得可行。讲座引用原始论文（Lee, Huang, Yang, PR 1957）及费曼相关研究（PR 1954），并参考黄克孙《五十年硬球玻色气》综述，说明该理论对冷原子系统与量子多体物理的深远影响。该工作是理解玻色-爱因斯坦凝聚中相互作用效应的基础，推动了后续量子气体与规范场理论的发展。讲座面向物理研究生、有准备的本科生及研究人员，每两周一次，持续进行，旨在教学性地解析杨振宁理论的物理内涵与数学结构。

On larger vessels, processes such as electrolysis can be used to separate water molecules into their independent parts of oxygen and hydrogen. The oxygen generated this way can then be circulated through the vessel for the crew to breathe, meaning these types of vessels can stay underwater indefinitely, with the only limitation being the amount of food it can hold to feed the crew. To remove carbon dioxide from the air, soda lime, which is made up of sodium hydroxide and calcium hydroxide, is used inside scrubbers. The soda lime traps carbon dioxide and removes it from the air. Problems arise when these systems fail and the air inside of the sub becomes a mixture of gases that is not safe to breathe.

Nuclear submarines maintain breathable atmospheres through two primary oxygen generation methods: electrolysis of purified water using potassium hydroxide as an electrolyte (creating oxygen and hydrogen), and chlorate candles that release oxygen through exothermic chemical reactions between iron and sodium chlorate; simultaneously, carbon dioxide is removed using either monoethanol amine (MEA) chemical scrubbers that absorb CO2 and release it overboard under pressure, or lithium hydroxide canisters that passively absorb CO2 from the air, providing redundant life support systems for extended underwater missions.

A submerged submarine is in a constant life and death struggle with the sea itself, beginning with the air they breathe. When 155 people are on board, they shut all hatches, producing CO2 and depleting oxygen levels. Each person generates over 2 pounds of CO2 per day. This air is pumped into scrubbers which separate the CO2 out and absorb it by blowing it across a chemical called monoethanolamine. Once isolated, it is pumped overboard. For oxygen, submarines use electrolysis to split water molecules, producing hydrogen and oxygen. The hydrogen is pumped overboard while oxygen is distributed throughout the ship or supplied into oxygen banks. Carbon dioxide poisoning has plagued submariners since the early days, with warning signs including headache, nausea, and in very high amounts, coma or death.

Inside a sealed submersible, air quality is critical for survival. At sea level, air contains 21% oxygen, but in a pressurized sphere, oxygen levels can become dangerously high or low. The Deep Sea Challenger uses oxygen cylinders to supply controlled doses of oxygen. More critically, lithium hydroxide cartridges remove CO2 from the air. Without these scrubbers, CO2 levels rise invisibly, causing headaches, confusion, and unconsciousness without warning. In the Johnson Sea Link disaster, CO2 scrubbers failed in the cold compartment, killing two crew members after 24 hours. This demonstrates that CO2 poisoning can kill silently before anyone realizes the danger has arrived.

The ISS maintains breathable atmosphere and water supplies through interconnected closed-loop systems. The Oxygen Generation System uses electrolysis—water splits into oxygen and hydrogen via electrical current. Oxygen enters the cabin; hydrogen feeds the Sabatier reactor. The Carbon Dioxide Removal Assembly uses zeolite molecular sieves with enormous surface area to capture CO2, cycling between absorption and regeneration at 200°C. The Water Recovery System achieves approximately 98% efficiency, recovering water from humidity condensate and urine through vapor compression distillation and multi-stage filtration. These systems work together: CO2 from crew exhalation feeds the Sabatier reactor, which produces water returned to oxygen generation. This creates a closed-loop where every breath generates raw material for the next breath, maintaining atmospheric composition (21% O2, 79% N2) and CO2 below 3 mm Hg partial pressure.

The favorite materials for building deep-sea exploration vehicles are specifically made and specially produced kinds of steel, acrylic, and most importantly, titanium. These materials and the methods by which they are turned into deep-sea submersibles have been tried, tested, and refined over decades. Ship classification societies like the American Bureau of Shipping exist to maintain standards of ship construction and marine technology. Their safety tests, not just for construction materials but for the submersible as well, take years to complete. The Cyclops was built in nowhere near enough time to conduct all these tests and safety checks.

Tensile strength refers to a material's ability to resist pulling or stretching forces, while compressive strength refers to its ability to resist crushing or inward squeezing forces. A water bottle demonstrates this: it can withstand tensile forces (being pulled) but easily crushes under compressive forces (being pressed inward). This distinction is crucial because airplanes and submarines face opposite physics problems - airplanes experience outward stretching from cabin pressurization, while submarines face inward crushing from ocean pressure.

Deep-sea submersibles require spherical pressurized areas because spheres distribute pressure evenly around their entire surface, preventing pressure buildup in any single area. These spheres are made from titanium or steel alloys. Historical examples like the Alvin (titanium sphere, first Titanic dive in 1986) and Mir subs (steel alloy spheres) have made numerous successful dives over decades. Viewports are the weakest points, requiring small, thick acrylic construction. Spherical designs are severely limited in passenger capacity, typically accommodating only two or three people. Increasing size exponentially increases cost and engineering difficulty.

Deep sea submersibles face immense hydrostatic pressure that increases proportionally with depth. At 3.8 kilometers, pressure reaches 37 MPa (5400 PSI), equivalent to 35 elephants on your shoulder. Hydrostatic forces are compressive and act radially inward, making hull integrity critical—any breach causes immediate implosion. Design requires understanding forces, materials, and geometry, aided by computer simulations and extensive testing. The Titan submersible, designed for 4000-meter depths, faced these fundamental engineering challenges.

At the Titanic's depth of 12,500 feet, pressure reaches approximately 5,500 PSI—equivalent to 366 atmospheres. This pressure is applied to an area slightly larger than an A3 paper, equivalent to a Saturn V F1 engine's thrust. Submersibles use cylindrical designs with inherent weak points in the center, where hoop stress concentrates unlike spherical geometries that distribute stress evenly. The Titan used three dissimilar materials (acrylic, titanium, carbon fiber) with different thermal expansion coefficients, creating stress concentrations at interfaces.