Meanwhile, Holland still refused to use these early periscopes, believing that they were too limiting operationally. Because the early instruments were relatively short, with a fixed height, a certain amount of “porpoising” was still necessary to bring the boat near the surface. If the periscope tube was too short, the submarine hull could easily broach the rolling waves, but if it was too long, the image became too dim and was significantly distorted by vibrations in the mast induced by the moving water. A thicker tube damped the vibrations but also increased the wake created by the periscope as it cut through the surface of the water.
The basic design for the modern periscope was perfected by the industrialist Sir Howard Grubb in Britain. His father founded a Dublin telescope-making firm, which Grubb eventually inherited. Renowned for his optical expertise, Grubb was commissioned to develop periscopes for the British Royal Navy’s new Holland-designed submarines in the early 1900s. Improving upon Lake’s omniscope design, Grubb eventually perfected his own version during World War I, which was installed on the majority of the British Royal Navy’s submarines, and on several U.S. Navy boats. The Grubb periscope and subsequent variants remained the submarine’s only visual aid for over fifty years, until underwater television was installed aboard the first nuclear-powered submarine, USS Nautilus (SSN-571).
From these early days through World War II, various improvements were made to periscopes, including the ability to rotate and be retracted into the hull. This allowed periscope tubes to become longer while the diameter was decreased to reduce wake. Around 1911, Dr. Frederick O. Kollmorgen proposed the introduction of two telescopes into the periscope, instead of a series of lenses. This allowed the window at the top of the periscope to become a simple piece of glass, as opposed to a prism, which in turn allowed for a much smaller head. The telescopes also made it easier to develop tubes of various lengths because of the lack of intermediary lenses. In 1916, during World War I, Kollmorgen formed the Kollmorgen Corporation, which quickly became the dominant U.S. periscope manufacturer. The two-telescope design was tested during the war, and became standard for periscopes into the modern day.
In the late 1930s, submarine operators convinced the Bureau of Ships to develop a new type of periscope that eventually became the “needle nose” Type 1 attack design. This featured a tube that tapered at its head to reduce the surface wake. Recognizing that by this time aircraft were a major threat to submarines, Kollmorgen in 1940 offered a modified Type 1 periscope, dubbed the Type 2. The Type 2’s field of view extended to 90.5 degrees of elevation, which enabled the attack periscope to cover the entire sky. The Type 3 designation was used for earlier large-head search periscopes, but this was replaced in World War II by the Type 4 night periscope, which featured a much fatter head (for greater light-gathering power) and a shorter tube (to reduce loss of light inside). A major innovation during this period was the advent of quality periscope photography. Throughout the course of World War II, most submarines sailed with two instruments – an attack periscope and a search/night periscope The Type 2 periscope could only operate during daylight, but it was known for superb optics and minimal wake. Improvements were made for greater depth, improved optics and optical coatings, and photo capabilities, and it remained in use through the 1990s.
By the 1950s, evolutionary improvements to the Type 4 design resulted in the Type 8 periscope. Frequent modifications during the decades since have made it one of the primary “hull-penetrating” periscopes in the fleet today, used on all USS Los Angeles (SSN-688)-, USS Seawolf (SSN-21)-, and USS Ohio (SSBN-726)-class boats. The Type 8 periscope features multiple levels of optical magnification, a day-and-night viewing capability, and an antenna system for EHF Low Data Rate (LDR) satellite communications.
|An officer aboard USS Bullhead (SS-332) “dancing with the gray lady.” This photo was taken during a Pacific war patrol in the spring of 1945.|
Also in the 1950s, a special stabilized periscope, the Type 11 “star-tracker,” was developed specifically for ballistic missile submarines to facilitate the more accurate navigation needed for missile launches. It was designed to take azimuth sightings of stars to update the planned Ships Inertial Navigation System (SINS), and it was the first periscope developed specifically for the nuclear-powered age.
With the advent of the Los Angeles-class fast attack submarine design in the late 1960s, the Navy developed a new attack periscope, the Type 18, which offered 18-times magnification, as opposed to its precursor’s eight. Kollmorgen again won the contract to design and build the periscopes, partly because their design allowed using a camera without removing the periscope’s face-plate. This design eventually permitted the use of television cameras, whose images can be displayed throughout the submarine and recorded. The Type 18 periscope is one of the primary hull-penetrating periscopes in the fleet today, used on all Los Angeles- and Seawolf-class submarines. Important features of the Type 18 include multiple magnification levels, single-axis stabilization, digital photography, low-light image intensification, color television, and day-and-night viewing capabilities. The Type 18 periscope is currently undergoing upgrades for a video package known as SUBIS (Submarine Imaging Subsystem), a set of analog video and digital still cameras that record the view from the periscope and provide image enhancement software for image analysis.
Although the Type 18 represents the current state-of-the-art in U.S. submarine periscopes, the Navy’s new USS Virginia (SSN-774)-class submarine will be getting a completely new set of eyes. Virginia’s AN/BVS-1 Photonics Mast has replaced the traditional optical lenses and prisms of conventional periscopes with electronic imaging equipment. Each Virginia-class submarine will have two photonics masts that do not require physical penetration of the ship’s hull, but instead “telescope” out of the sail. Importantly, this allows Virginia’s Control Room to be moved from the cramped first deck to the more spacious second deck. Additionally, there will be no “gray lady” to dance with – or take up valuable control-room space – since the customary periscope in its below-deck well gives way to a fiber optic system that carries images from the photonics masts to two workstations and a commander’s control console, each equipped with two flat-panel displays and a keyboard, trackball, and joystick. The masts are equipped with three cameras – color, high-resolution black-and-white, and infrared – in addition to a mission-critical control camera in a separate, pressure-proof and shock-hardened housing and a laser range finder that will provide accurate ranges to targets and aids to navigation. All of these sensors are housed in the mast’s rotating head.
CAPT David Portner, the Program Manager for the Imaging and Electronic Warfare Program Office, notes that “the Photonics Mast is one of the revolutionary systems aboard Virginia. Its digital imagery design eliminates the need for a major hull penetration required for optical periscopes. Not only does it keep the CO from having to focus entirely on the top-side scene, but it has allowed the ship designers to break the hard link between the sail and the Command and Control System Module (CCSM). In doing so, Virginia’s sail has been moved forward for improved hydrodynamics and its CCSM relocated down one deck and aft, affording this critical space more room and an improved layout. The non-penetrating design also increases hull integrity and simplifies maintenance.”
In a hundred years, submarines have progressed from having to porpoise at the surface to see outside, through crude viewing devices fixed in height and direction, to today’s hull-penetrating, multi-purpose, camera-equipped scopes, which allow the boats to get a clear view of the outside world from up to 60 feet below the surface, while revealing almost nothing of themselves. And yet, today’s periscopes are based on the same fundamental principles of prisms, lenses, and telescopes that their predecessors exploited a century ago. But radical change is on the way. With the first of the new Virginia-class submarines already in the water, the submarine’s capability for viewing the world above the surface is taking off in the first fundamentally new direction since the days of John Holland and Simon Lake.
Mr. Holian is an analyst with Anteon Corporation in Washington, D.C. and a Contributing Editor to Undersea
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