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
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.
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:
have a 300-foot draft to mount hydrophones;
acoustically quiet (this led to the requirement that the hull should
be completely flooded in the region near the hydrophones to avoid
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;
capable of being berthed at a pier where the draft might be as shallow
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.
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. 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.
The Office of Naval Research sponsored
a 40th Birthday ceremonial flipping operation on June 21, 2002, to honor
its long life as a useful research platform.