Abstract: Processing of electrical signals representative of incident and reflected acoustic signals generated by underwater explosion and comprising primary and secondary impulse, or bubble pulse, peaks. Acousto-optic diffraction and optical Fourier transform of the primary or explosive incident signal is performed and photographically recorded to provide a bubble pulse spatial filter. The filter is used in performing subsequent acousto-optic diffraction and optical Fourier transforms to derive impulse response, bottom loss, and an output electrical signal representative of the reflected signal, without the bubble pulse.

Abstract: A wide angle, wide bandwidth sonar transducer comprising a spherically cud array of transducer elements fully embedded in a body of acoustically transparent potting compound with their axes extending radially outwardly of a spherically curved wall to which they are bonded. Each includes an aluminum load element bonded to a piezoelectric element and is characterized by an electrical terminal press fitted into the load element. A method of manufacture for achieving the desired array formation within the potting compound utilizes a pattern from which a form is cast to hold the transducer elements in formation while being bonded to the curved wall, after which the form is removed and additional potting is cast.

Abstract: A telephone system for use by divers employing demand breathing apparatus. ounds picked up by each diver's microphone are processed by selective filtering, amplification, rectification and comparison to a reference voltage level to provide logic signals representative of presence or absence of inhalation noise that could mask voice transmissions of other divers or of a tender. The microphone output to listening stations is switched through an attenuation path by the logic signal representing inhalation noise and through a by-pass or full strength path by the other logic signal.

Abstract: A composite diver's umbilical including concentric hoses for breathing gas, eating fluid supply and return, electrical conductors, and a strength member, and cooperating separable connectors for effecting end to end joining of segments of the umbilical. The connectors are characterized by cooperating nipple and receptacle members having coaxial, arcuate passageways, and cooperating pin and socket electrical connectors.

Abstract: A roughness measuring tool wherein a pair of discs are mounted in spaced allel relation for rotation by a motor about a common axis with a face of only one of the discs being exposed to a layer of fluid contacting a surface to be tested. A torsionally resilient coupling beteen the discs permits rotational displacement due to a difference in hydrodynamic drag thereon. The displacement is sensed as a phase difference between signals generated by rotation of the discs and a phase signal is applied to a function generator the output of which is displayed as a figure of merit of test surface condition.

Abstract: A towable cable type electrode has a bouyant core covered by a layer of hcally laid wire strands and is characterized by a slide member near the aft end of the electrode to which the aft ends of the wire strands are secured. The slide member is constrained by guides to axial movement along the core so as to accommodate excess length in the wire strands that works its way aft along the electrode during use.

Abstract: A three axis magnetometer is provided with a single calibration checking l lying in a plane disposed at equal angles to each of the three orthogonal axes of sensitivity. Energization of the calibration checking coil with a known current while the calibrated magnetometer is in a known condition of calibration provides sensitivity readings for each of the three axes, which readings provide a standard of comparison for checking the calibration and sensitivity of the magnetometer by similar energization of the coil when the magnetometer is disposed in a remote operational environment.

Abstract: A magnetometer wherein inductance of a resonant circuit is made sensitive changes in magnetic field to vary an oscillator operating frequency. The magnetometer utilizes a ferromagnetic sensor element that is characterized by high permeability in weak magnetic fields when the element is maintained at predetermined elevated temperatures near the Curie point of the element material and also exhibits a hysteresis curve having a steep slope in the region of field strengths on the order of the earth's magnetic field. The preferred embodiment includes resistive heating of the element and use of substantially pure iron as the element material.

Abstract: An underwater navigation device wherein a flux gate compass provides head difference signals, a doppler navigation sonar provides drift angle signals, which signals are combined by a summer to provide steering correction signals that are displayed by a steering null meter.

Abstract: Relative phase and sensitivity characteristics of individual transducer eents in a long acoustic array are determined by sequentially positioning a transmitting element in predetermined spaced relation to each array element by means of an array holding member and a trough-like spacing member that contains a known transmission medium, driving the transmitting element with a test frequency input signal that is pulsed at a predetermined repetition rate, gating the output signal from the array element under test to an oscilliscope for phase comparison with an adjustably phase shifted version of the input signal, and measuring amplitudes of both input and output signals.

Abstract: An electro-optic modulator wherein a light waveguide is in the form of a film disposed on a prismatic substrate and beneath modulating electrodes. The substrate has opposite end faces disposed at predetermined angles to its longitudinal axis and cooperates with grating couplers on the waveguide to direct an entrance beam through the waveguide and to provide an exit beam along a predetermined path relative, e.g., parallel, to the entrance beam.

Abstract: A sonar system is disclosed which processes received sonic energy echo sils in such manner as to determine whether or not a marine mine or other object of significance is laying on a particular area of sea floor being sonically scanned or searched and, in addition, whether or not said marine mine or other object has a sonic energy shadow behind it. If and when such two conditions are met, an alarm is given to the human operator monitoring the subject sonar system, so as to call his attention to the fact that a target of significance has been acquired.

Abstract: A depressing force in the form of negative lift is hydrodynamically generd on a towed underwater vehicle as a result of fluid in motion passing static fluid separated by a membrane so as to cause a negative pressure zone externally of the membrane. The external negative pressure enhances distension of the membrane into a water foil generating additional negative lift.

Abstract: Method and apparatus for mixing hydrogen and oxygen as a noncombustionable ixture of gases which avoids the hazard of a combustible mixing interface are disclosed as comprising a pair of cylinders which timely contains a water solvent within which said hydrogen and oxygen are respectively dissolved under pressurized and refrigerated conditions, in accordance with a predetermined program of operations. Then, the gas-saturated water of one of said cylinders is mixed with that of the other, thereby causing the gases therein to be mixed wthin the mixed water. The resultant gaseous mixture is subsequently separated from said water mixture, dried, and stores as a mixture of hydrogen and oxygen gases.

Abstract: A helicopter carried, towline recovery buoy system including a package coining a retrieval line, inflatable buoys, and buoy inflating devices. A support and release mechanism releases the package response to dropping of the towline. The buoys and retrieval line are automatically deployed to permit recovery of the towline by grappling from a helicopter.

Abstract: A diving helmet exhaust regulator valve maintains helmet pressure substanlly constant in a push-pull system wherein breathing gas is supplied under pressure (push) at a constant rate and respired gas is exhausted to a low pressure (pull) conduit for return to a regenerator. The regulator valve is characterized by a throttling valve member operated by a piston that is acted upon by ambient sea pressure and helmet pressure independently of pressures in the upstream exhaust passages, or of exhaust flow rate.

Abstract: A low-noise, stage-stabilized, direct-coupled, single-ended amplifier cirt is disclosed which has a unique feedback network combined therewith in such manner that degenerative alternating current and substantially constant direct current feedback signals are supplied thereto, so as to effect an exceptionally steady amplification factor therefor over a very broad frequency response band.

Abstract: A connection for releasably securing a diving helmet to a suit through the se of nestable upper and lower ring members having mating cylindrical portions sealed by an O-ring. A tongue and slot serve to orient the helmet during donning and cooperate with two sets of pintles and gudgeons disposed 120.degree. from one another to secure the ring members together.

Abstract: Phase detection between interfering light beams in an interferometric sys is accomplished by frequency shifting the reference beam prior to combination with the interrogation beam and electro-optically scanning the resulting pattern to produce an FM electrical signal having the shift frequency as a carrier and the interrogated parameter as the modulation data. A phase lock loop is responsive to the FM signal to provide a D.C. signal that is analogous of rate of change of the interrogated parameter with scan, and which is integrated to provide an output voltage signal that is proportional to the interrogated parameter and the corresponding optical phase difference. The method and system employing it are operative for a wide range of phase differences including multiple fringes.

Abstract: A vehicle carried metal object sensing system wherein sensing of magnetic elds of different polarity or of ferrous and non-ferrous objects results in distinctive colors on a cathode ray tube display. Deflection signals are generated in accordance with vehicle travel and field scan to provide successive frames of a map-like display.