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In 1962, the Research Platform FLIP was developed with the need for a stable platform to measure fine-scale fluctuations in phase and amplitude of sound waves in support of the Navy SUBROC program. One of the major questions concerned bearing accuracy obtained acoustically out to convergence-zone ranges. Horizontal temperature/salinity gradients in the ocean could introduce bearing errors in the volume of the ocean, and sloping bottoms could do the same for acoustic paths that interacted with the bottom. What was needed were measurements to determine the extent to which environmental gradients and fluctuations could affect bearing accuracy out to convergent zone ranges.

In the late 1950's Drs. F. N. Spiess and F. H. Fisher embarked on experimental work to address these problems with Dr. Spiess attacking the effect of bottom topography and Dr. Fisher attacking the effect of horizontal gradients and fluctuations on bearing accuracy.
Dr. Fisher initially used the research submarine, the USS BAYA (AGSS 318) to make such measurements, piggybacking on research cruises with Frank Hale and Henry Westfall of the US Navy Electronics Laboratory (NEL). After a few cruises, it became clear that the submarine was not a satisfactory platform for this work, even though it had hydrophone booms with a 100-foot span. There was no way to obtain either an optical or electromagnetic-bearing reference in a satisfactory manner at periscope depth or at the desired 300-foot depth needed for separating acoustic multipaths. Even at the 300-foot depth, wave-action effects caused sufficient yawing motion of a
submarine to limit measurements of bearing fluctuations in acoustic propagation.

Phillip Rudnick, Fred H. Fisher and Fred N. Spiess, designers of FLIP, holding the first model of FLIP made from a Louisville slugger bat by Marvin Crouch of MPL.

Phillip Rudnick, Fred H. Fisher and Fred N. Spiess, designers of FLIP, holding the first model of FLIP made from a Louisville slugger bat by Marvin Crouch of MPL.

Dr. Fisher described these problems to Dr. Spiess in January, 1960. Dr. Spiess mentioned that Allyn Vine of the Woods Hole Oceanographic Institution had suggested upending a submarine to make a stable platform. Allyn Vine got this idea from observing how stable a navy mop floated in choppy water; that is the stability of a long, narrow, buoyant object floating in rough water could make it possible to make simultaneously bearing measurements in deep water and compare them with optical or other signals above the water. This interchange resulted in the development of the Research Platform FLIP.

Drs. Spiess and Fisher determined that it would not be possible to convert a submarine to a vertical platform and that it would be better to start from scratch. To measure bearing accuracy and the fine-scale fluctuations in bearing (phase difference) and amplitude of sound waves due to inhomogeneities in the ocean such as thermal microstructure and internal waves, a manned spar buoy was proposed as an ideal platform to make such measurements.

The original requirements established for the platform were:

  • should have a 300-foot draft to mount hydrophones;
  • be acoustically quiet (this led to the requirement that the hull should be completely flooded in the region near the hydrophones to avoid acoustic reflections.);
  • have a high degree of torsional rigidity so the position of hydrophones at the 300-foot depth would be knownwith respect to an optical benchmark in the laboratory above water;
  • have an electronics laboratory above the surface from which visual, radio, and radar contact could be maintained with a surface ship; and
  • be capable of being berthed at a pier where the draft might be as shallow as 15-feet.

Extensive model studies with different 1/10 scale model configurations were conducted by Dr. Fisher to work out the flipping operation. The idea was to simply flood tanks by opening valves to vent the control tanks. These studies led to the need for a hard tank that could withstand the full differential pressure during the flipping operation in order to prevent plunging that occurred when the tanks were allowed to flood freely. By dividing one hard tank into top and bottom sections and adding ballast in the horizontal keel, it was possible to ensure a safe flipping operation.

Launching of FLIP from Gunderson Brothers Engineering Company, Portland, Oregon, June 22, 1962. Launching of FLIP from Gunderson Brothers Engineering Company, Portland, Oregon, June 22, 1962.

MPL proceeded to design, conduct model tests and supervise, with the assistance of the commercial naval architects, L. R. Glosten and Associates of Seattle, Washington, the construction of FLIP [Floating Instrument Platform]. FLIP was constructed in just six months and on June 22, 1962, the full-scale FLIP was launched at the Gunderson Brothers Engineering Corporation yard in Portland, Oregon. Cdr. Earl D. Bronson, USN (ret.), supervised construction and developed the operating techniques. Total initial construction cost was under $600,000.

On July 23, 1962, after completion of outfitting, it was tested for the first time in the Dabob Bay area of the Hood Canal in Washington state on the Navy tracking range. After successfully completing trials of the flipping operation, it was towed to San Diego to commence operations in September 1962.

Christening ceremonies of FLIP at Gunderson Brothers Engineering Company. Christening ceremonies of FLIP at Gunderson Brothers Engineering Company. Left to right: Capt C. B. Momsen, Jr. (Office of Naval Research), Dr. Fred N. Spiess (MPL), Warren G. Magnesun (Washington State Senator), and Sally Spiess. (June 22, 1962).

Over many years of operations have included many deployments in the Pacific as far as Hawaii and one deployment to the Atlantic. While originally intended for acoustic research, it has become a versatile platform for research in upper-ocean physical oceanography, meteorology, geophysics, and biology.

On June 29, 2012, the Office of Naval Research sponsored a 50th Birthday celebration for FLIP at the Nimitz Marine Facility, Scripps Institution of Oceanography, to honor FLIP's long life as a valuable research platform:

With special guests onboard, on June 30, 2013, FLIP got underway and proceeded to a area 20 miles west of San Diego, California, for a ceremonial flip. it was flip number 381 of FLIP's research career.


On June 30, 2013, FLIP executes flip number 381 of its research career.

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