The concept of a wire antenna for submarines arrived on the Navy’s communication horizon in 1954, the same year as the launching and commissioning of the first nuclear submarine USS NAUTILUS (SSN 571). Six years later, in 1960 USS TRITON (SSNR 586) was able to deploy a buoyant cable antenna and maintain continuous radio reception during its historic circumnavigation of the world while submerged. From its beginnings, the floating wire antenna has provided capabilities which have steadily improved and reflected the communication needs of nuclear submarine platforms.
In the mid 1950s, interest in this type of antenna at the Navy Underwater Sound Laboratory’ in New London was directed to the communication requirements of the diesel submarine while submerged. During these early years, research worked with this antenna toward providing the submerged submarine a send-and receive capability. The frequencies of interest were 2 to 30 x 106 Hz. At that time, submarines periodically still rose to, or neared, the surface to charge batteries and conduct radio frequency communications.
NAUTILUS, a true submersible with the ability to spend extensive periods submerged, provided additional submarine antenna challenges including new speed and depth considerations. As the nuclear submarine program grew, each new class of attack and fleet ballistic missile submarine brought fresh, interesting, and difficult challenges to the Underwater Sound Laboratory (USL) antenna engineers, scientists and technicians.
Technology, patience, support and hard work gave a viable buoyant cable antenna to attack and strategic submarines by the mid-1960s. Today, an inboard retrievable buoyant cable antenna is part of the antenna suite of all U.S. submarines and those of major foreign powers.
Introduction of this submarine antenna concept resulted from the initiatives and investigations of James Tennyson, a physicist and inventor working in the Radio Communications Branch of the Electromagnetic Division of USL. He came to the New London Laboratory from the Naval Research Laboratory in February 1947 when the submarine radio research group was still in a formative stage.
In October 1944, during Word War II, a German conference was held on underwater antennas in Berlin. Minutes of this wartime conference mentioned the possible use of a floating cable antenna towed by a submarine for radio communications. The report of the conference came to the attention of Tennyson in the early 1950s. The idea caught his interest. After some preliminary research and limited encouragement, he proceeded with development of an experimental floating wire antenna. The initial thrust was to use a floating wire to address the problem of intra-fleet communications. An early goal was to provide a range in the order of 20 miles.
First problems included how to make an antenna that would float. This was one of the tasks that John Amaral, a long time radio engineer at the Laboratory, helped to resolve. He assistec Tennyson in all the early experiments and at-sea tests. At th~ Laboratory he fabricated the first antennas that would float. His installations and tests of these early floating wire antennas included the submarines BARRACUDA (SST 3), BONITA (SS 551) AND BASS (SS 552), /Editor’s Note: BARRACUDA was redesignated from SSKl to SST3 in July 1959. BASS and BONITA were redesignated from SSK2 and SSK3 to SS 551 and SS 552 respectively in December 1955.] as well as others. One early sea test with floating wire antennas involved Amaral in an under the ice exercise in the North Atlantic involving three diesel submarines and an at-sea transfer from one diesel submarine to another in a polynya.
Initial laboratory investigations into the capability of an antenna to radiate while floating just above sea water were conducted at the USL test facility located at Fishers Island, New York, six miles from the New London Laboratory. An underground laboratory below a 50 foot diameter ground level sea water test pool allowed measurements to be made on antennas placed in the pool simulating the condition of a submerged submarine.
The first floating wire antennas as previously mentioned were made at the Laboratory. A 100 foot length of a standard coaxial cable (RG-14/U) was used. Flotation was achieved by using 50 small football-shaped fishnet floats six inches long and three inches in diameter along the cable. 2 The outer jacket and metal braid were stripped from the last 25 feet of the cable. Floating on the surface, this 25 foot length of center conductor separated from the sea water by the cable’s dielectric became the active part of the antenna. For the next several years, this was the basic design.
In July 1954, Tennyson and Amaral conducted a successful at sea test with the experimental antenna on the submarine USS TUSK (SS 426). The first communication was between TUSK and the laboratory site on Fishers Island, New York. As mentioned previously, the interest was in transmitting and receiving while submerged. Later in 1962 and 1964, Tennyson was awarded patents for his floating wire antenna invention.
The early antennas with floats were about 100 feet long. The lead-in end was attached to an antenna fitting on the sail while the outboard end was always made so that the antenna could not reach and tangle in the screw. The original antennas were throw-overthe-side wires with floats.
The concept was a success. However, during the following years both difficult and first-ever technological challenges were continuously addressed. Antenna frequency considerations, how to make an antenna that would be buoyant without the fish net floats, and how to have an overall antenna system compatible with the submarine’s requirements were some of the problems that lay beyond this first demonstration on TUSK.
First Buoyant Cable
In 1956, further development of the antenna at USL was transferred to the Antenna Branch of the Laboratory’s Electromagnetic Division. An RF cable for the antenna that would have buoyancy and not require floats was sought, and the first length was delivered by a cable company in 1958. Obtaining the sufficient buoyancy, cable strength, and ease of handling the cable were some of the many antenna requirements which had to be met. Between 1959 and 1969, with the cooperation of many cable manufacturers, USL developed approximately 36 different versions of single conductor and coaxial buoyant cable.
USL antenna engineers Warner Adams and Richard Jones developed the first mechanized system. In August 1958, it was tested at sea onboard USS BARRACUDA . This system was the inaugural use of an inherently buoyant cable with a cable payout and retrieval reel (on the afterdeck of BARRACUDA). It was also the first time that up to 1000 feet of cable could be streamed, allowing the submarine to communicate at deeper depths. COMSUBLANT reported that viable submarine-aircraft and submarine-surface ship communication ranges were achieved from a submerged submarine. The external reel system arrangement was overtaken by further developments which provided an inboard launching and recovery of the buoyant cable.
RF Reception Below Periscope Depth
Emphasis in succeeding years was on developing the buoyant cable antenna concept to meet the operational requirement for VLF and LF reception below periscope depth. Developing an antenna compatible with the nuclear submarine’s changing speed and depth requirements was elusive, at least initially.
However, by the end of the 1950s, USL was manufacturing fixed-length buoyant cable antenna installations which provided submerged reception on a number of landmark submarine missions.
In 1959, USS SKATE (SSN 578), using an early one inch diameter buoyant cable antenna received broadcasts under the Arctic icecap while making a North Pole transit. (The previous year, NAUTILUS was the first submarine to make the transit.) The following year, 1960, USS TRITON, using a smaller diameter (518 inch) buoyant cable antenna, maintained continuous radio reception during the previously cited historic circumnavigation of the world while submerged. The antenna was streamed throughout the entire trip without mishap or failure. The first fleet ballistic missile submarine, USS GEORGE WASHINGTON (SSBN 598), successfully used a fixed length outboard connected type buoyant cable antenna during an early patrol (1960) and reliably received VLF broadcasts while remaining completely submerged.
The fixed length outboard connected type limited submarine operability when using the antenna. In order to receive, the several hundred foot antenna restricted the submarine’s speed and depth. Further, if the antenna was damaged or cut, the submarine would have to surface to replace or repair it since the antenna was not inboard retrievable.
Antenna Inboard Retrievability Demonstration
In 1960, U.S. Navy Commander Oater Captain) Arthur P. Sibold, Jr., during his assignment as Senior Program Officer and Executive Officer on the staff of the Commanding Officer and Director of USL, investigated the inboard recoverability problem and identified an innovative solution. At this time, USL was heavily involved in several aspects of Polaris submarine communications, including both electromagnetic and acoustic.
He proposed the idea of using a line wiper of the type found in the oil drilling industry to pay out and reel in the USL developed floating wire antenna from inside the submarine. He conducted a test in June 1960 onboard USS HARDHEAD (SS 365) off New London. The line wiper was developed in the mid 1950s by Bowen-Itco in conjunction with paraffin removal in oil well operations under pressure. The test was successful in demonstrating that a floating wire antenna could be paid out and retrieved from inside the submarine.
On 3 June 1960, Commander Si bold wrote a USNUSL Technical memorandum outlining his design concept, Recommended Approach to Development Qf a Recoverable Floatinr Wire Antenna. This was followed by an 8 June 1960 Technical Memorandum, Report of Test of Recoverable Floatinr Wire Antenna, which reports the sea test results.In 1964, Commander Sibold filed for a patent on his invention and was granted a patent for a Pressure-Proof Hull Fitting on
Aprill 2, 1966. The patent addressed providing the submarine with the capability of launching, repairing, and recovering of devices such as a VLF communications antenna towed astern while the submarine is underway and submerged.
Inboard Retrievable Buoyant Cable Antenna Systems
Tennyson’s invention brought about practical reception of RF signals below periscope depth. The nuclear submarine brought with it the necessity of receiving while submerged. The Polaris program increased the requirements for submarine communications. New speed and depth needs as the new nuclear classes evolved kept increasing the challenge. Commander Sibold’s demonstration pointed the way to provide an antenna system which could be brought inside the submarine for repair, replacement or stowage while the submarine was underway and submerged.
The device, called a transfer mechanism, to accomplish the inboard handling of buoyant cables hundreds of feet in length led to an evolutionary research and development program; and in the early 1970s, a standard transfer mechanism was available (BRA24).
Like all submarine antennas, buoyant cable antennas confront extreme temperatures, high pressure, severe drag forces and high sea states. In addition, buoyant cable antennas accommodate the transfer mechanism and are wound and unwound from a drum. Mechanical requirements are measured in thousands of pounds of pull. Further, the antenna had to meet the radio frequency specifications.
Between 1959 and 1989, a series often developmental antennas were produced most of which were configured with a 0.65 inch diameter antenna which has become the standard size. The antennas had a steadily increasing break strength of 1000 pounds in 1950 and finally as much as 5000 pounds in some current designs. It was the advent of the commercial production of Kevlar as an antenna strength member that brought about the enhanced break numbers. The results of these improvements is seen in the speed/depth performance curves of these carefully designed and produced antennas.
In general, buoyant cable antenna effectiveness was improved by in-line electronic miniaturization, materials developments, and other advanced techniques. Over several decades, the realization of better cables, active in-line amplification at the antenna element, design and development of improved connectors compatible with the transfer mechanism and other devices led to a series of patents to various Laboratory personnel: A. Susi, L. Carnaghan, R. Phillips, and B. Pease.
ELF and the Floating Wire Antenna
In 1963, under the broad Polaris Special Projects Program called Pangloss, extensive efforts were being made to address a solution to communicating from land to submerged submarines. At that time, extremely low frequency (ELF) was an experimental candidate to satisfy the Navy’s need for secure radio wave transmission to submerged fleet ballistic missile submarines.
An intensive six weeks of communication tests were made starting January 21, 1963 with a receiver installed on USS SEAWOLF (SSN 575). At that time, the experimental ELF transmitter was located in North Carolina and the transmitting antenna was 109 miles long, oriented northeasterly. The submarine was equipped with a 1000 foot trailing wire antenna. at the end of which was a pair of sensors. Signals in the ELF spectrum were measured at ranges of about 2000 miles in the North Atlantic with the trailing antenna at keel depth. At greater depths, signals were received at a range of more than 500 miles with the antenna. ELF permitted reception at antenna depths much greater than was possible with VLF. The tests on SEA WOLF using a floating wire antenna supported the feasibility of ELF reception by a submarine at operational depths.
These communication tests established that a deployed submarine could receive messages from the continental United States without severe reductions in the submarine’s operational capability during reception. This was a first in the history of submarine communications.
During the extensive at-sea testing conducted over a number of years during the development and implementation of ELF, the Laboratory’s buoyant cable was a key element of the submarine suite. For example, a successful ELF communication test was conducted in 1976, using a floating wire antenna, on a submarine traveling at 16 knots at a depth of 427 feet under 33 feet of Arctic
sea ice. The Wisconsin ELF test facility was the signal source.
Submerged reception at operational speeds and depths at frequencies of the order of tens of Hertz to the Megahertz region are the result of 50 years of hands-on effort at the New London Laboratory. Support by the Navy in Washington, and a multiplicity of sea tests on diesel and all classes of nuclear submarines at locations around the globe brought Tennyson’s vision to a firm reality and a submarine antenna capability which will improve further in the future.