Windows into the Abyss: Why Submarines Have Viewports and How They Resist the Pressure

Anyone who has ever had the opportunity to observe a submarine up close has undoubtedly noticed the small windows set into the protruding structures often referred to as «turrets». These seemingly ordinary features naturally spark curiosity: what exactly are these windows, and what purpose do they serve? Could it be that submariners peer through them during dives, gazing into the abyssal darkness of the ocean depths as they steer their vessel? To unravel this mystery, we must embark on a journey into the intricate world of submarine architecture, carefully examining both the terminology and the functional logic behind these vessels’ design.

The confusion often begins with the term «conning tower», a phrase that carries different connotations depending on the context. Technically speaking, a conning tower refers to an enclosed superstructure found on various types of vessels — from surface ships to airships and, of course, submarines. Its primary role is to house critical equipment and control systems. However, the way this structure manifests and functions varies dramatically across different vessel types. On surface ships, for instance, the conning tower might integrate multiple command and navigational functions, serving as a central hub for vessel operation.

When it comes to submarines, however, the situation becomes considerably more nuanced. What most observers identify as the conning tower — the prominent structure rising above the submarine’s hull — is not actually the true conning tower in engineering terms. This visible superstructure is, in fact, merely the enclosure for retractable devices, a technical designation that reveals its true purpose. The real conning tower, known as the strong conning tower, exists entirely within the submarine’s pressure hull.

This strong conning tower serves three vital functions that are essential for submarine operations. Far from being a command centre in the traditional sense, it operates primarily as a watertight airlock, providing a crucial transition point between the interior of the submarine and the outside environment. Additionally, it functions as an emergency escape chamber, offering a last resort for crew members in dire situations. Finally, and perhaps most importantly, it serves as a protective housing for the periscope shafts — the submarine’s primary means of visual observation when submerged.

Modern submarine operations have evolved significantly, with vessel control now centred in a conning tower that is seamlessly integrated with the main command post. This central command area is located deep within the pressure hull, far removed from the external superstructure that captures the observer’s attention. The bridge and primary control station reside in this protected interior space, ensuring the crew’s safety and the vessel’s operational integrity.

The external superstructure, with its distinctive windows, serves a much more practical purpose than one might initially assume. Rather than housing control systems, this structure exists primarily to protect the submarine’s protruding equipment — periscopes, antennas, and airlocks — from environmental hazards and potential damage.

An interesting divergence in design philosophy emerges when we compare Soviet‑style submarines with their Western counterparts. Soviet submarine architecture often incorporates an additional feature within the retractable device enclosure: a dedicated bridge space. This bridge, while sharing some functional similarities with surface ship bridges, operates as a completely separate external compartment accessible only when the vessel is on the surface. Unlike the integrated bridge structures found on surface vessels, this submarine bridge serves specifically as an observation post, providing crew members with a protected vantage point when the submarine operates in surface mode.

Those small windows observers notice on Soviet submarines are, in technical terms, bridge ports. Their function, while seemingly simple, is critically important: they provide essential visibility for crew members when the submarine is operating on the surface. This design feature highlights a significant difference between Soviet and Western submarine philosophies. Most Western submarines lack such enclosed bridges, meaning their officers must perform surface watch duties exposed to the full force of the elements — the biting wind, driving rain, and relentless sea spray. In contrast, Soviet and Russian submarine designs prioritise crew comfort and protection, offering a sheltered environment that makes surface operations considerably more bearable.

One might wonder how these bridge ports withstand the immense pressures encountered during submersion. The answer lies in a clever engineering solution: when a submarine dives, the bridge area — unlike the robust conning tower — is intentionally flooded. This flooding ensures that the pressure on both sides of the glass remains nearly equal, preventing the windows from shattering under the weight of the surrounding water. The windows themselves are constructed from specialised materials, typically high‑strength acrylic or polycarbonate, chosen for their ability to withstand significant pressure differentials while maintaining optical clarity.

Beyond their practical function, these bridge ports represent a fascinating intersection of engineering necessity and human factors. While they may appear to be simple observation windows, their placement, construction, and integration into the overall submarine design reflect careful consideration of multiple variables: operational requirements, crew safety, material science, and even psychological well‑being. The decision to include these windows — and to position them precisely where they are — demonstrates how submarine designers balance technological constraints with the very human need for visibility and connection with the outside world, even in the most extreme operating environments.

Thus, what might initially appear as mere windows on a submarine’s exterior are, in reality, sophisticated components of a complex system — each element carefully designed and positioned to serve specific functions while contributing to the vessel’s overall operational effectiveness and crew comfort.