LOOKING AROUND: A SHORT HISTORY OF SUBMARINE PERISCOPES Part II

Mr. Merrill retired from a long and distinguished career at the New London Division of the Naval Undersea Warfare Center. He currently writes historical works involving that lab and its accomplishments. Part I appeared in the January 2002 issue of THE SUBMARINE REVIEW.

WORLD WAR II

The Ubiquitous Periscope

The periscope is omnipresent throughout Sink ’em all: Submarine Warfare in the Pacific, Vice-Admiral Charles A. Lockwood’s factually accurate and technically correct (as credited by Fleet Admiral Chester W. Nimitz) account of the United States submarine in the Pacific in World War II. Throughout the book, a typical recurring quote regarding a submarine attack read “up periscope; and stand by number one tube” or an equivalent comment concerning the periscope.

More than 200 submarines meeting fleet boat capabilities were constructed between 1941 and 1945. The Balao class USS BOWFIN (SS 287), commissioned May 1, 1943, was typical of the wartime fleet type submarine at 311 feet in length, crew of 80, 20 knots surfaced, 10 knots submerged, 1,526 tons surfaced, and a 75 day cruise capability.

Like most other submarines of the period, BOWFIN carried two periscopes. The one nearest the bow, designated as No. 1, was the night scope and with a large head providing the highest usable light-gathering power and a large 7mm-diameter exit pupil. The length of this periscope was 36 feet with a net weight of 2000 pounds. The No. 2 aft periscope was the attack scope with a tapered upper section and small diameter, 2-1/2 inch head leaving a smaller wake or feather in the water from the periscope to be seen. The narrower design also reduced light transmission and the diameter of the exit pupil (4 or 5mm). The attack scope was four feet longer and had about the same weight as the night periscope. Kollmorgen manufactured both BOWFIN periscopes. The periscopes were equipped with a stadimeter for measuring the distance to an object of known height.

By 1927, as noted previously, Kollmorgen dominated the United States periscope field. At the Kollmorgen plant in Brooklyn, New York, the 1944 wartime production rate of USN submarine periscopes peaked at one periscope per day. The typical World War II periscope cost $10,000 and by the mid-1950s the price became $30,000. Multiple functions and operation at increased depths and speeds accounts for some of the price change.

Type 2 Daylight Attack Periscope

The Type 2 daylight attack periscope was introduced into the submarine fleet in 1942 and found wide use and acceptance during World War II and in the decades following. It is recalled today (2001) with great respect for its superb optics by some present day submarine personnel who operated with the Type 2. The optical capability of more recent periscopes with a variety of non-optical devices crammed into the coveted space is not held by some with the same regard.

The periscope’s long slim neck (1.4 inches in diameter) with a very small head resulting in reduced wake made it attractive for use in submerged daylight attack operation. In the post World War II era, modifications were made to provide greater pressure capability (greater depth). Other changes in later models included improved optics, optical coatings, and photo capability. In particular, reduced photographic vignetting effect was achieved with better optical elements.

A Japanese Horse Race Track

USS GUARDFISH (SS 217), commissioned May 8, 1942, was on its first war patrol by August, off the coast of Japan close to Yagi, a port in Northern Honshu. The city’s horse race track could be seen through the periscope. Photographs taken with the periscope supported the memory of the event and proof that the viewing took place. This frequently-cited incident is evidence of the then-current periscope’s optical and photographic capability as well as the courage of the submarine and its crew. It is notable that on this initial patrol, the submarine was credited with sinking 70,000 tons of enemy ships.

Off Tokyo Bay

USS JACK (SS 259), a fleet submarine commissioned in January 1943, in Groton, Connecticut, was on its first patrol off Tokyo Bay by mid-June. The new submarine sank more than 16,000 tons of Japanese merchant shipping on this patrol. Admiral James F. Calvert in Silent Running: My Years on a WWII Attack Submarine recalls the role and some of the use of the periscope. Concerning the sighting of targets: he writes “Our routine was to expose about two feet of scope. With that height we could see the tops of an average maru’s masts at maybe three or four miles. This meant that the circle of our observation was only six to eight miles in diameter, an area of about fifty square miles at best.” Target hunting with a periscope was a formidable task. A further use of the periscope concerned the presence of enemy aircraft: ” … the remaining thing the 000 had to be careful about with his periscope watch was the presence of aircraft … They were hard but not impossible to see through a periscope.”

Type 4 Periscope with Radar

A meeting of submarine officers and logistics planners in December of 1943 at Mare Island concurred that the performance of a new night periscope would be enhanced if a radar antenna (providing active detecting and ranging) and electronics could be squeezed into a standard 7-1/2 inch periscope tube along with the opticle. ComSubPac Admiral Lockwood was a participant. A 9-inch diameter night periscope, in use by some foreign navies, would more easily accommodate radar and was considered However, the larger diameter increased the threat to the submarine’s stealth in the event that it was needed in a daytime emergency. Development of the new periscope moved ahead. The 7-1/2 inch diameter Kollmorgen radar-equipped periscope was tested seven months later on the newly commissioned SEA FOX (SS 402).

In November 1944, the Kollmorgen Type 4 periscope including the new ST firing range radar, augmenting the on board SJ radar, was operational on SPIKEFISH (SS 404), a Balao class 400 foot operating depth submarine. This submarine was also the first to be fitted with hydraulic periscope hoists replacing the cable and motor arrangement.

With the ST radar and the periscope in the same mast, a radar approach to a target and the periscope approach became simultaneous, with attendant advantages. The Navy’s submarines in the Pacific did not overlook this benefit. In combination, the ST and SJ radar provided targeting improvement at night and during conditions of fog. In an emergency, this could be used for daytime approaches. The pairing could also work against radar-equipped Japanese escorts.

Further, this periscope was the first to introduce navigation by periscope and a reasonable photographic capability. 24 In the years ahead, use of the mast for multiple functions increased. The companion periscope, the Kollmorgen Type 2 (anack periscope) developed during the 1930s, was widely installed in the fleet type submarine of WWII and continued in extensive use as late as the 1990s. As previously mentioned, its features included a narrow 1.4-inch diameter neck, and enhanced optics for daytime use. The Type 4 complemented the Type 2 for night submarine torpedo anacks. As the war ended, Kollmorgen had two general categories of periscopes: the Attack (Type 2) and the All-Purpose (Type 4).

British Periscope Length

With regard to periscope length, military historian Peter Padfield noted that British submarines were at a disadvantage in an attack during World War II because their periscopes were shorter. They were made of bronze, so as not to affect the magnetic compass in the conning tower. Other navies were using steel. Bronze (unable to bear the length that steel could support) resulted in a loss of periscope depth of 10 to 16 feet. “British boats were more subject to surface swell, hence more difficult to control and more liable to break surface at critical moments in an attack. n2′ Padfield points out that the conning tower (also constructed of bronze) added weight that was compensated for by using thinner plating for the pressure hull. This reduced submarine diving depth. German and United States hull plating was three-quarters to seventh-eighths inches thick while British plating was slightly over half an inch.

German Periscope Innovation

On the first day of World War II September 3, 1939, U-30 sank the Atlantic liner A THENIA by torpedo 250 miles northwest of Northern Ireland. The toll in lives was 112 including 28 Americans. The liner was en route from Glasgow to Montreal with primarily refugees as passengers. The sinking was contrary to German rules of engagement at that time and caused an international stir similar to the sinking of the liner LUSITANIA in 1915. Padfield cited above in War beneath the Sea recreated the torpedoing. Concerning the periscope, ” … he [Commanding Officer Oberleutnant Fritz-Julius Lemp] swung himself on to the metal bicycle-type seat straddling the attack periscope housing abaft the hatch opening. Unlike the system in other navies, the eyepiece on the German attack periscopes did not move up or down with the shaft but remained at a fixed height. .. n26 From his seat, the operator’s right hand controlled the height of the scope and the left, the focus and stadimeter. 27 The any-height periscope capability later was a feature of a 1950s Kollmorgen Type 6 attack periscope.

U-boat Periscope Conditions for Attack

In The U-Boat Commander’s Handbook,28 attack instructions highlight the periscope’s role under favorable and unfavorable circumstances. Even under favorable conditions, cautions and limitations must be observed, including minimizing periscope height. Sea states 2 to 3 and wind levels of 3 to 4 are favorable. However, if the sea is as smooth as oil, “The slightest ripple even of the low periscope is noticeable, and easily observable by the enemy. Exceptions: enemy coming out of a bright sun; conditions of twilight; moonlit nights.”

POST WORLD WAR II

Periscopes and the Nuclear Submarine

With the launching of the first true submersible, the nuclear-powered USS NAUTILUS (SSN 571) commissioned September 30, 1954, two factors heavily influencing periscope specifications for the remainder of the 20111 century involved the depths and speed of the nuclear submarines. The greater underwater speeds available with the advent of nuclear power demanded a periscope capable of being raised at high speed without vibration damage. As operational depths, increased watertight integrity became a prime consideration to be met by the periscope builders with heavier periscope tubes and improved pressure seals.

Periscopes Under the Ice

In 1957, during the initial under-ice probe for a nuclear submarine, NAUTILUS (SSN 571) came within 180 miles of the North Pole. This investigative trip by the first nuclear submarine introduced a new role for the periscope. Under some conditions, a view aided by sunlight of the underside of the ice could be seen. For some situations a topside floodlight was available. But sonar remained the primary tool for under ice navigating.

During the early part of the trip to the ice shelf, the Number 1 periscope, with a badly-packed hull fitting, dripped seawater leakage on the user. Once repaired, both scopes became useful later when skirting under the ice. However, while proceeding slowly under ice in a northerly direction, periscope casualties of a serious nature took place. A polynya appearing to be free of ice was not. As NAUTILUS gradually moved up toward the surface of the polynya, the Number 1 scope went black. The periscope was bent and could not retract because it was bent. Number 2 periscope was damaged beyond repair. Skill, effort, and clever stainless steel welding in an Arctic environment brought the Number 1 periscope back to operability. Periscopes are helpful but not absolutely vital under ice. Sonar is essential.

Missions and Surveillance

The Cold War development of the strategic fleet ballistic missile submarine with its pivotal deterrent role and unique mission needs created further significant demands on periscope design and engineering creativity. In particular, the precise navigation needed for missile launch led to the development of the Kollmorgen Type 11 Star Tracker periscope. This periscope developed for the Polaris submarine is capable of taking automatic star sights to allow the submarine to determine and maintain its position with an accuracy of seconds of arc.

At the same time, new and varied intelligence and surveillance missions of some attack submarines brought about additional fresh periscope requirements. The periscope tube and head as real estate was highly sought. Expanded prtions of the electromagnetic spectrum vied for space. Optical (visual, photographic, navigation, and laser), infrared (imaging), and electronic warfare support measures (ESM) antennas contended for room in the periscope head and rube. With severe space limitations, challenges abounded. The periscope engineers and builders and the engineers and scientists of the other periscope electromagnetic systems at government and industrial activities found the requirements particularly demanding. The post-war periscopes with the multiple capabilities may best be described as all-purpose periscopes.

In the 1950s, a common periscope need was how to improve bundling the various non-optical systems in the limited diameter (7-1 /2 inch) periscope tube. The Navy’s goal was to develop and enhance the other systems sharing the space with the optics including photographic, electronic surveillance measures antennas, radar, and sextant navigation. A further objective involved improving the mechanical aspects of operating the periscope. The Kollmorgen Type 88, delivered in 1959 and widely installed in the United States submarines, incorporated some of the aforementioned features and also included a new electric motor to quietly and easily train the periscope in azimuth.

The Periscope Builders

Throughout the last half of the 20111 century, the Kollmorgen Corporation remained the primary developer, integrator, and builder of submarine periscopes for the U.S. Navy. In 1952, the U.S. Navy moved the company from Brooklyn, New York to Northampton, Massachusetts.

During the 1950s, the U. S. Navy decided it was necessary to have at least two sources of supply for all critical systems on the submarine. In addition, it was expedient to foster competition. The U. S. Navy funded Kollmorgen to transfer periscope-manufac-turing know-how to Sperry Marine in Charlottesville, Virginia. This was a successful effort; and even though Kollmorgen main-tained its stature as the developer of periscopes, Sperry successfully competed with Kollmorgen into the early 1990s. Bausch and Lomb in Rochester, New York also had a brief involvement during the 1950s in the building of submarine periscopes.

Periscopes representative of the 201h Century are shown in the Periscope Summary. A significant number were designed, manufactured, and delivered by the Kollmorgen Company. The periscopes addressed solutions to new submarine mission require-ments, new submarine speed and depth capabilities, and the implementation of technological innovations. Some of the modifications or changes were optical; others related to the various systems co-located in the periscopes and produced by other companies.

Kollmorgen improvements during the 1950s included photo-graphic instrument enhancements and the inclusion of the first radar detection system. Advanced optical coatings were introduced at this time, significantly reducing the reflection losses in the optical elements. To increase the length of a periscope in some designs, typically Kollmorgen uses three relaying telescope sets. For these periscopes with as many as 30 optical elements with 60 surfaces, light loss reduction is essential.

In general, each periscope stems from a previous design. The World War II Type 4 all-purpose periscope evolved in 1951 into the Type 8 with a navigation capability incorporating a tilting head prism. Initially, this was due to longer submerged periods as a result of the snorkel. The extended undersea capability of the nuclear submarine required further celestial navigation improve-ment using the periscope. The Types 9 and IO were developed to answer this requirement. Both were versions of the Type 8. A program in 1957 adding a communications capability emerged as another version of the Type 8 with a 7-112 inch tube and replaced the Types 9 and 10. This Type 88 with increased edge illumination from 10 percent to 40 percent for photography was in the fleet by 1959. More recently, the Type BB has been further modified to incorporate additional satellite communication capability.

Periscope Summary

Note: Types 2, 8, 15, and 18 are Kollmorgen designed periscopes, manufactured at Kollmorgen and Sperry Marine. Types 16 and 22 were designed and manufactured by Sperry Marine.

Navy Laboratory Role in Submarine Periscopes

At the Navy’s Underwater Sound Laboratory (USL) at Fort Trumbull in New London, Connecticut, optical and elector-optical systems investigations began in 1947 with the development of infrared detectors for use on surface ships. The Laboratory’s submarine antenna group experience included periscope antennas.

As alluded to earlier, by the mid-1960s, a consensus within the submarine community was converging on three submarine missions attack, deterrence, and intelligence. Periscopes appropriate for each mission share common attributes but the different missions have unique needs. Solutions to the equipment needs for the various systems embedded in the periscope were found in the advanced technology available in such areas as photography. Adapting the technology to the periscope and submarine environment required resourcefulness. Designing for and implementing the new peri-scope requiremencs broadened Navy periscope Research and Development participation. It was at this juncture that USL’s participation in the Navy’s periscope programs changed significantly.

The Navy solicited industry for proposals including Perkin Elmer, ITEK, and Kollmorgen. Kollmorgen and the ITEK company in the Boston area were awarded winner takes all prototype development contraccs. Kollmorgen eventually won the competition and continues to produce and improve the Type 18 today.

In 1967, the Washington projeccs office responsible for recon-naissance, electronic waifare, special operations, and naval intelligence processing (REWSON) and aware of USL’s submarine interescs and ability to address optical and electro-optical research and engineering problems brought the Laboratory into the Type 18 development program. This engineering advisory role for the Laboratory occurred after the start of construction of the demon-stration Type 18 periscopes. State-of-the-art optics in the new periscopes was the primary emphasis. Periscope work placed new demands on the Laboratory’s physiciscs, electrical, and mechanical engineers through generations of periscopes, including the current non-penetrating periscopes.

This new assignment took place as the periscope was continuing to evolve from simple optics-only systems used for visual observa-tion into more complex systems incorporating communications, radar and ESM countenneasure antennas, and eventually satellite communication capability. Equipment to suppon visual observation such as TV and photographic cameras were add-on devices and not universally readily available at that time.

Kollmorgen and ITEK, both Massachusetcs companies were competing for the Type 18, each constructed a demonstration periscope (optics) for evaluation at sea. Based on the sea tests and evaluations, USL made recommendations regarding the details of the planned periscope that included increased light-gathering capability, image motion compensation, stabilization, and enhanced photographic capability. Kollmorgen won the competition for the full-scale development of the Type 18 periscope.

REWSON assigned NUSC to oversee the full development, installation. and test and evaluation of the new Type 18 periscope. A particular area of attention by the New London Laboratory was integration of the TV and photographic aspects of the new peri-scope. Successful completion of Technical and Operational Evaluations at sea of the Type 18 followed in 1971 and 1972.

Initial employment consideration for the Type 18 involved a modest production of systems as mission requirements dictated. It soon became evident that the SSN 637 class and the growing SSN 688 class submarines could benefit from the special capabilities of the Type 18 on all missions. Further. the 1972 production contract with Kollmorgen included a complete design of the ESM portion of the system, since the original demonstration model of the Type 18 provided optics only. The New London Laboratory was tasked to oversee the Type 18 production and fleet introduction. The initial production periscope installation was performed on board USS CA VALLA (SSN 684) by a NUSC/Kollmorgen team in mid-1975.

By 1981, Kollmorgen manufactured 52 Type 18 periscopes. Three years later. the New London Laboratory developed signifi-cant Type 18 periscope documentation based on the New London Laboratory’s intense involvement with installation and introduction of more than 40 Type 18 periscopes on SSN 637 and 688 class submarines. The total production of the 688 class was more than 60 submarines. This documentation allowed the fleet to maintain, repair and support the periscope’s logistics. It was the first submarine periscope brought under Navy configuration management.

As the various periscopes developed, the Laboratory’s technical involvement and contributions included areas such as electronic imaging and introduction of satellite capabilities for communications, and navigation including the satellite Global Positioning System (GPS).

During the 1978-80 time frame, NUSC received further periscope development work under the sponsorship of the Office of Naval Intelligence (ONI}. A new mission oriented periscope, the Type 22 (a replacement for the Type 16) was developed for the SSN 688 and SSN 637 class submarines. Both the Types 16 and 22 were designed and manufactured by Sperry Marine at Charlottes-ville, Virginia. These periscopes were used as mounting devices for deploying imaging systems, and both used basic Type 2 unique optics. NUSC Type 22 responsibilities included sensor integration, maintenance and installation. Periscope building by Sperry Marine began in 1955. In 1995, Kollmorgen purchased their product lines.

Periscope Facilities

In the mid 1970s, the increasing periscope role at the New London Laboratory resulted in the construction of a periscope facility at that location in order to be able to conduct periscope work. It was determined that requirements and specifications for such a facility did not exist. Subsequently, a specification and design for a periscope facility was developed at New London. A facility was constructed and opened in December 1977. The facility was expanded in 1984 to accommodate periscope satellite systems. In 1985, the Laboratory developed a Naval Sea Systems Command guide for periscope facility development and provided assistance in the improvement or construction of new periscope facilities in Hawaii and at the Trident Submarine Bases at Bangor, Washington, and Kings Bay, Georgia.

Trident Periscope

In 1974, NA VSEA selected NUSC as their technical representa-tive agent for the development of the Trident Fleet Ballistic Missile Submarine periscope shipset. The periscopes that were developed by Kollmorgen for Trident were modifications of the Type 15 and Type 8 periscopes. The Trident periscopes are the U.S. Navy’s longest periscopes. Both periscopes function as optical instruments and antenna masts, and include omnidirectional or direction-finding antennas for signal reception in support of early warning, and contain antennas for external communication and satellite navigation.

In 1979, an early Trident shipset was delivered to NUSC for a yearlong test program. Trident Ohio class periscopes were the first periscopes developed from a full Navy specification and the first to have integrated logistics support as a fundamental consideration in the development.

Periscope Systems Enefneering at NUWC

Beginning in 1992, NUWC undertook technical initiatives with financial support from the intelligence community that improved overall periscope performance for mission requirements. This was accomplished by engineering the most advanced imaging and sensing capability (exclusive of the optics) into a Kollmorgen Type 18 periscope.

Commercially available high-end technology devices appropriate to the periscope’s requirements were examined, tested and engi-neered to accommodate the space and conditions found in the periscope. Initial success of this approach led to ongoing efforts for upgrading the sensors and taking advantage of the latest available devices. Principal areas include low light level color television; low light level black and white television, and the digital still camera. Significantly, the digital camera removes the need for wet photographic processing on board the submarine. Further, these new capabilities developed by NUWC are in keeping with the concept of a workstation for observation and distribution of the data collected by periscope sensors in lieu of the eye-box and the one-person observer.

THE NEW CENTURY

With more countries acquiring submarines, demand for periscopes continues and among the builders Kollmorgen in the United States and Zeiss (Germany) stand out. Pilkington (Barr and Stroud) in Great Britain and SAGEM (France) also produce periscopes for the current world market.

As recently as June 2001, Kollmorgen’s venerable 1950s Type 8 periscope is cited. The news release by the Naval Sea Systems Command’s Naval Undersea Warfare Center (NUWC) Division in Newport, Rhode Island identified a multimillion dollar contract modification to incorporate infrared imaging capability into a variant of the U.S. Navy’s still popular Type 8 (Type 8 Mod 3).

A Russian company (LOMO}, located in St. Petersburg, site of the founding of the Russian Navy 300 years ago, and a builder of periscopes for all Russian nuclear submarines, is presently developing and manufacturing an attack periscope. Features include a night vision channel, laser range finder and satellite navigation and warning antennas. The periscope is designed for prospective diesel submarines of the Amur Class.

Non-Hull Penetrating Periscopes CNPP)

For almost a century, the traditional submarine periscope remained basically the same. The NPP concept with new image sensing initiated by Kollmorgen as early as 1978 is moving towards fruition in the new century. The technology making it possible electronically to deliver the periscope images into the submarine (control room) is referred to as optronic or photonic. These techniques make NPP possible.

The NPP, by not requiring a 5-10 inch diameter periscope mast to penetrate the submarine hull, enhances hull integrity. In addition, there are more opportunities for periscope location. The periscope may be entirely located in the submarine’s sail (fin). With fiber optic and wire data transmission, the new telescoping mast eliminates the deep well and the nearly fifty feet of hull-penetrating optics tubes that are installed on current generation submarines. NPP allows greater flexibility in submarine hull design, as it is not necessary for the periscope mast to be directly above the submarine’s bridge, also allowing a more optimal use of space. It has been commented that in the future the optical periscope is still likely to continue as the choice for some submarine configurations.

In 1992, a Kollmorgen prototype optronic hybrid system using commercial visible and infrared spectrum cameras was built under a contract with the Defense Advanced Research Projects Agency (DARPA) and demonstrated for sixteen months on USS MEMPHIS (SSN 691) a Los Angeles class submarine. Currently Kollmorgen, Pilkington, and Zeiss are producing versions of NPP.

Kollmorgen’s Optronic Mast includes features like ESM, communications, and GPS antennas, color charge coupled device camera, high definition TV camera, eye-safe laser range finder, and thermal imaging camera. Pilkington’s NPP mast for early 21″ Century British submarines similarly contains a surveillance package that includes color, low light, and thermal imaging television cameras.

NPP technologies allow the periscope observations to be taken quickly and recorded with images later replayed, enlarged and examined while at depth by any crew member at various locations on other systems in the submarine. Microwave direction-finding functions and other features are in the NPP. In 2001, the Virginia class submarine and the Royal Navy’s Astute class will not include traditional periscopes in deference to two NPP systems.

A 1995 article in conclusion notes a considerable degree of customer resistance to the optronic mast at that time. “The sophistication of the sensors and their supporting electronics as well as hydraulics have raised fears about their reliability.” 30 The author goes on to point out that, if the optronics fail, some navies are of the opinion that the submarine commander will need a periscope optical path for reserve.

Submarine Periscopes and their Customers

With the 201h century introduction and acceptance of the submarine as a proven important component of modem navies, above water imaging has a future. Whether in the form of the now old optical path device with a variety of technological devices sharing the tube real estate or the looking around device (optronic) outside the pressure hull being very high technology, the periscope has an ubiquitous and continuing presence on all submarines. The world’s submarine navies include:

Ahead

At first, the periscope task was to capture quickly and covertly the visual part of the electromagnetic spectrum. The last half of the 20″‘ Century saw other parts of the electromagnetic spectrum sharing the periscope tube. Now that the NPP has removed the optical link and wires, wave-guide and fiber optics are the path-ways. Periscopes and their subsystems continue as the central point for surveillance, electronic warfare and intelligence gathering with the ability to process, distribute and share information. Ahead lies the challenge of remote surveillance for the submarine in the water and above.

Acknowledgment

Curator Stephen Finnegan and archivist Wendy Gulley at the Nautilus Submarine Force Library and Museum in Groton, Connecticut, made periscope archival material available which was most valuable concerning the early part of the 20th Century.

A great number of people, who really knew and understood periscopes, came forward and patiently helped me unravel the history of the periscopes of the last half of the 1900s. These physicists and engineers (primarily with careers at USL, NUSC, and NUWC) included John Comiskey, James Flatley, Carl Floyd, Gary Motin, Ralph Polley, Herman Ruhlman, and Paul Sheldick. Roger Densmore of Analysis and Technology Inc. provided further historical details. Herbert E. Torberg, a long time Kollmorgen engineer, scientist and company president greatly increased my understanding of periscopes. Douglas Jones, Matthew Richi and John Nixon of Kollmorgen provided significant additional insight.