Abstract: A seeker having a gyroscopic spin stabilized optical arrangement adapted to gimbal relative to a body in response to a current fed to a precession coil by a processor. Gimballing action of such optical arrangement within the body is measured by a voltage induced in a cage coil. The precession coil and cage coil are mounted adjacent to each other. The seeker includes a cage coil compensator comprising a differencing network and a differentiator. Changes in the current fed to the precession coil induces unwanted voltage in the adjacent cage coil. The differentiator is fed by the current in the precession coil to produce a voltage related to the rate of change in the current in the precession coil and hence, related to the undesired voltage induced in the cage coil. The differencing network is fed by the voltage produced by the differentiator and the total voltage induced in the cage coil to subtract from such total voltage the undesired portion thereof induced therein by the adjacent precession coil.

Abstract: A three-dimensional large scale rectilinear array of hydrophones comprising a plurality of equally spaced, fixed position, omni-directional, electro-acoustic transducers, utilizes aperture steering circuits to create a polar coordinate map indicating the bearing and elevation of incoming sound signals. The attitude and depth of the array is controlled by an array maneuvering system to position the array for maximum signal strength and to rotate the array to a horizontal position for maneuvering in shallow water. The geometric configuration combined with digital signal processing circuits provide improved sound detection threshold over linear and single planar arrays. An acoustically transparent housing is used to enclose the array. The shape of the housing and supporting structural frame are adapted to limit self-induced background noise.

Abstract: The underwater sound projector includes a hollow-cylindrical metal housing having a recess with an opening. A non-ceramic flexural disc is supported over the opening. Within the recess is a stack of piezoelectric ring elements. A metal drive head transfers force axially from the stack to an annular area on the disc spaced from the center thereof. Foil electrodes are interposed between the piezoelectric rings and situated at the ends of the stack. A stress bolt clamp connects the drive head to the housing with the stack situated therebetween.

Abstract: The disclosed flextensor transducer enables the transmission and reception of acoustic waves in water at very great depths. It includes at least one pillar of piezoelectrical cells placed within an impervious shell. Each pillar is supported solely by a first end on the shell, and is compressed on the shell by a counter-mass applied to its second end.

Abstract: Alignment restoring apparatus for use with seismic shock generators that includes a support frame, a lift frame supported by the support frame, a seismic generator peripherally supported by the lift frame, and a base plate supported by the life frame and arranged to be impacted by the seismic generator. The alignment restoring apparatus includes biasing means located between the lift frame and the base plate to provide a restoring force upon movement of the frame relative to the base plate whereby the initial relationship between the frame and base plate is re-established assuring that the time lapse from initiating the propulsion of the seismic generator toward the base plate to the time of impact therebetween is repeatable.

Abstract: A digital marine seismic system employes a plurality of data acquisition control modules which simultaneously digitize analog seismic signals. The control modules also are selectably addressable in that each module is uniquely programmed to respond only to a particular control word. The system allows a large number of channels, such as 480 channels, on a simple transmission system, such as a twisted pair of wires. Each module includes a power switch to sequentially apply power to downstream modules. Selective addressing of the switches allow testing of specific modules for power malfunctions.

Abstract: An acoustic detection device having a parabolic dish antenna for gathering ound waves and providing a first stage of amplification, an exponential horn located at the focus of the parabolic dish antenna for further acoustic amplification, a fluidic gainblock for a final stage of amplification, and acoustic earphones for listening. Either a hand operated latex bulb or a mechanical pump is used to pressurize a plastic fluid storage container that is used to supply fluid to the fluidic gainblock. Within the fluidic gainblock are four or more staged laminar proportional amplifiers having a bandwidth of 0 to 4,000 Hz.

Abstract: A flextensional sonar transducer assembly includes a stack of piezoelectric elements disposed along a linear axis, a plurality of electrodes disposed between the elements, end pieces disposed at each end of the piezoelectric stack, with the end pieces having outwardly facing, generally arcuate surfaces, a compression band formed into a loop to encircle the stack and end pieces, a flexural shell disposed to circumscribe the compression band to present a generally elliptical side cross-section, with the major axis thereof being generally coincident with the linear axis of the stack, and with the shell being reactively coupled to the arcuate end portions of the compression band, and rod members positioned between the compression band and the arcuate end portions of the band of material for maintaining driving contact between the shell and the end pieces, and for adjusting the prestress compression pressure in the stack. The invention also includes methods of manufacturing the transducer assembly.

Abstract: A method is provided for improving the coefficient of transmission to geological formations of the energy generated by the firing of a seismic source lowered inside a well or borehole and a device for implementing same. A zone of the wall containing the seismic source is defined by confinement so as to prevent the propagation along the well, outside the confined zone, of the energy generated therein by the seismic source, when fired. The confinement is achieved by closing off the wall on each side of the seismic source. Two expandable members are used disposed in the wall on each side of the source and each comprising for example an elastomer sheath, an annular piston whose movement causes expansion of the sheath and hydraulic means for moving the piston.

Abstract: A firing system for marine seismic sources 14 grouped and fired in subarrays 18. Each source 14 is provided with a firing circuit 30 including an energy storage device, such as a storage capacitor 32, adapted to pass firing current through the source actuator 24 in response to receiving a low power trigger signal from a source control system 28 located on the ship 16 from which the seismic survey is conducted. The firing circuit 30 corresponding to each source 14 is situated proximate the source 14. An umbilical 20 extends between the control system 28 and each subarray 18. The umbilical 20 includes a trigger signal conductor corresponding to each source, a charging conductor to which the storage capacitors of each firing circuit 30 are connected in parallel and a ground conductor.

Abstract: Apparatus for generating a controlled parameter elliptically polarized shear wave into an earth medium. The apparatus consists of a baseplate for engagement with the earth medium in omni-directionally resistant manner and a reaction mass and actuator assembly affixed thereto and energizable to impart reciprocal lateral forces to the baseplate that exert a predetermined resultant force at a controlled rate of rotation.

Abstract: A transmitter comprises an impeller assembly rotatable by a liquid flow, and an electrical generator having a stator and a rotor arranged to be driven by the impeller assembly. The impeller assembly comprises a main impeller portion and a secondary impeller portion angularly displaceable relative to one another about the axis of rotation of the impeller assembly in response to a change in load of the generator so as to vary the pressure drop across the rotating impeller assembly. Thus appropriate variation of the load of the generator may be used to control the impeller assembly in such a manner as to transmit pressure signals within the liquid flow. Such a transmitter is particularly suitable for transmitting measurement data to the surface from a measuring instrument at the end of a drill string within a borehole. Furthermore such a transmitter can be constructed so as to be readily retrievable without requiring withdrawal of the drill string from the borehole.

Abstract: A streamer-cable assembly is provided having a tubular outer jacket enclosing an open-cell and closed-cell foam core. The foam core provides an axial hole for retaining a plurality of pressure sensors and a plurality of off-axial holes providing passages for the transmission bundle. Longitudinal channels along the exterior of the foam inserts receive substantially rigid stress members which provide longitudinally strength to the streamer. Cable noise associated with the cable jerk and cable whip/vibration is radially reduced by the open-cell foam core and rigid stress members while the closed-cell foam core provides buoyancy to the streamer cable at the connectors between sections.

Abstract: An apparatus is disclosed for balancing a seismic streamer cable. The housing is comprised of a first and a second valve coupled about the streamer cable. Each valve has a clasp adapted to engage a socket on the other valve to ridigly fasten the valves together about the streamer cable. The housing surrounds and retains weights applied to the streamer cable. An alternate embodiment is disclosed where the weight is integral with each valve. The exterior of the housing is designed to produce laminar flow conditions for the fluid passing over the housing as the cable is under tow, reducing ambient noise detected by the sensors within the streamer cable.

Abstract: Geophones are placed around pipelines to detect third parties, e.g., heavy construction vehicles. Associated computer equipment acquires data from the geophones and discriminates for the frequencies associated with heavy construction vehicles.

Abstract: A downhole seismic exploration device comprises a seismic detector such as a geophone and a magnetic clamp, supported by Q-rings in an open cradle carrier which can be secured to a cable linking several such devices into an array. The array is lowered into a cased borehole and the magnetic clamps are operated to clamp the devices temporarily to the casing. Seismic signals detected by the geophones are transmitted to the surface via the cable, the O-ring supports acting to reduce or eliminate transmission of vibrations from the borehole fluid and the cable via the carrier to the geophone. The array is then unclamped and moved to another location in the borehole and the operation repeated. The magnetic clamp comprises a rotatable permanent magnet with radial poles disposed between a pair of parallel pole piece plates protruding on each side of the device and separated by non-magnetic blocks on each side of the magnet.

Abstract: A method for reducing signal degradation in a foam covered hydrophone used in seismic marine streamers. Said method comprises purging the foam streamer body with a fluid which is at least partially miscible with an oil used to fill said foam body. Thereafter, said foam body is filled with oil by gravity-assistance. Said method substantially removes air trapped in said foam body thereby reducing said signal degradation. Fluids, which can be utilized include butane, carbon dioxide, and fluorocarbons.

Abstract: A method of measuring the shear modulus profile of a seabed floor using one or more bottom shear modulus profilers, each having a seisometer package to measure the seabed motion in three dimensions and a sensor for measuring the pressure at the seabed floor, placed on or below the seabed floor, and a means for converting the measurements derived therefrom into a shear modulus profile.

Abstract: An omnidirectional hydrophone having an elastic shell which is spheroidal so that the circumference of the shell about different axes changes differentially when the shell is subjected to pressure variations. The differences in circumference are advantageously measured by an optical fiber interferometer having one leg wound about the equatorial circumference of the shell and another leg wound about its meridional circumference. The shell may be an oblate spheroid having the ratio of its major axis to is minor axis greater than about (2-.nu.)1/4, where .nu. is Poisson's ratio of the shell material, so that the shell narrows along one axis and widens along the other when the shell is subjected to a pressure change.

Abstract: A seal of flexible waterproof material joins two shells, or a shell and its end plate, which are spaced at their edges to have a separation or gap between them into which the seal material loops. The seal material is attached to each shell, or to the shell and its end plate, to effect a watertight seal at the joint. When one joint edge moves radially with respect to the other edge, a low friction rolling action of the seal material accommodates the motion with low frictional resistance and low energy loss.