The birth of ASW during the First World War inaugurated a scientific commitment to underwater sound research which has persisted to the present day. The work of the Navy and the Woods Hole Oceanographic Institution (WHOI) with the bathythermograph (BT) and underwater sound transmission before and during World War Two demonstrated the remarkable results achieved on behalf of the Submarine Force through the proper combination of pure and applied science.
The BT was first developed in 1934 at Woods Hole by CarlGustav Rossby of MIT and refmed over the next three years by his colleague, the South African, Athelstan Spilhaus. This instrument provided the scientist with data on water temperature variation as depth increased and allowed a better analysis of the all-important course of echo-ranging signals through the water.
Given its awkward construction and tolerance only for slow surface speeds, the Rossby-Spilhaus version of the BT required further refinements before the Navy could place it in service. In October of 1940, Maurice Ewing, a WHOI associate and Professor of Physics at Lehigh University, along with his students Allyn Vine and J. Lamar Worzel, began working on a more refined and durable version of the BT for use in both ASW surface ships and submarines. Their goal was to give the Navy a way of determining sound velocity through seawater. Since water temperature was the most important factor in this calculation, the BT proved the perfect instrument Allyn Vine recently recalled that “our problem was not to make it necessarily more accurate but to make it so that it was ten times more usable.”
During 1941 the WHOI team developed a BT model which could endure depths of over 400 feet and provide accurate data at speeds of between 15 and 20 knots. By 1942 most research vessels and convoy escorts carried BTs. Under Allyn Vine’s supervision, Woods Hole manufactured two hundred of these instruments before the Bristol Company of Waterbury. Connecticut. signed a contract to assume this responsibility in cooperation with WHOI.
In estimating the BT’s wartime value. Columbus Iselin. director of the Institution from 1940 through 1950, commented that in “the first four years of its use. over 60.000 records were accumulated and processed. From data collected by these. and later by the submarine bathythermographs. new fields of sound transmission phenomena were opened. ”
Ewing and Vine created a submarine BT in 1942, and added isoballast lines to the standard 3 x S inch graph on which the submarine BTs recorded their temperature data. This graph allowed the submarine diving officer to determine quickly the location of density layers caused by dramatic temperature change. This data would provide the probable locations of shadow zones in which a vessel could escape detection because of the effect of radical temperature change on the speed and direction of the active ASW sonar signal. The isoballast lines provided further insurance by actually giving the submarine diving officer the number of tons of ballast water he would have to take in or pump out in order to maneuver the submarine quietly into the shadow zone and maintain trim without further machinery noise.
In one typical example, the submarine USS HERRING (SS233) recorded, in its submarine patrol report for the period 11 to 17 June 1943, that the submarine BT allowed the diving officer to determine increasing water density as the temperature decreased with depth near Palau. ~ a consequence. the information from the submarine BT “enabled him to adjust his trim so that during the search following each attack while we were deep he never had to pump, blow or increase speed to maintain depth.”
With the aid of WHOI and other centers of oceanographic research, the Navy acquired a greater understanding of the factors common to both ASW and submarine warfare. Very often the research which helped the ASW forces to find and kill a submarine with greater frequency during World War Two also permitted the submarine to hide or take countermeasures. For oceanography, ASW and pro-submarine research were two sides of the same coin.
Consequently a close professional and personal relationship developed between the submarine community and those scientists, like Allyn Vine and William Schevill of Woods Hole, who taught officers how to apply scientific developments to their craft. These scientists managed to convince operational officers that instruments such as the submarine BT could truly protect their boats in post attack searches and enhance their chances of survival.
At a 1972 Navy ceremony honoring Allyn Vine for his work on the BT and submarine BT, a former engineering officer on the USS GUITARRO (SS-363) recalled a time twenty-eight years before when his vessel barely survived a Japanese search. The GUITARRO managed to hide under a layer of dramatic temperature change at 240 feet detected by the submarine BT. He concluded his comments by saying, “We on the 363 have always believed in the BT but this attack made salesmen for the BT out of us. ” As a result of experiences like this, many veteran officers became great friends and apostles of ocean· ography when they occupied billets of considerable influence in the pentagon in the postwar era.
In addition to their research and instrument development, the WHOI faculty instructed naval officers both in the field and at Woods Hole in the operational application of naval oceanography. The faculty wrote manuals, held classes, rode the submarines giving lessons on the use of instruments, and acted as advisors to the commanders of American Submarine Forces in the Atlantic and Pacific. Woods Hole, in conjunction with Scripps Institute of Oceanography and the Naval Hydrographic Office also inaugurated the Submarine Supplements to SailinK Directions. a series of classified Navy publications which provided submarine officers with additional information regarding the most critical characteristics of the ocean in various war zones.
Some of WHOI’s water temperature research also led to developments which proved significant after the war. In one case Maurice Ewing and J. Lamar Worzel discovered the remarkable sound transmission characteristics of the ocean’s natural deep water channels and their possible importance for naval warfare. In the North Atlantic the deep sound channel usually occurred at approximately 4,000 feet. Ewing and Worzel determined that sound traveled at a minimum speed at this Depth. But, as Columbus Iselin recalled, because of sound refraction, or bending, “signals emitted in this layer can travel very long distances without having to undergo bottom or surface reflection. Thus sound transmission in this layer is relatively efficient and a receiver located at similar depth can record signals originating several thousand miles away:
By 1943, Ewing and Worzel developed their knowledge of underwater sound channels into the SOFAR system for locating downed airmen. The unfortunate pilot would drop a small bomb set to explode in the SOFAR sound channel. With the extraordinary transmission properties of this layer, the Navy could detect the submerged explosion at three carefully situated listening stations. The time the sound took to reach each station would provide sufficient data for rescue personnel to calculate the location of the pilot.
Using this same principle, but reversing the process, if the three stations broadcast a signal into the sound channel, a submarine equipped to receive the transmissions could easily determine its location. This alternate use of the SOFAR system, called RAFOS, formed the basis for postwar submarine navigation systems and the underwater Sound Surveillance System (SOSUS).
Wartime work demonstrated to scientists that applied research could produce great rewards, as well as new frontiers for exploration. For the submarine community, these conflicts identified the practical application of science as one of the most potent weapons in the submarine’s arsenal.