Abstract: Apparatus for measuring pressure fluctuations in air or other gases in an area of elevated temperature. A condenser microphone is located in the area of elevated temperature and electronics for processing changes in the microphone capacitance is located outside the area and connected to the microphone by means of a high-temperature cable assembly. The microphone includes apparatus for decreasing the undesirable change in microphone sensitivity at high temperatures. The high-temperature cable assembly operates as a half-wavelength transmission line in an AM carrier system and maintains a large temperature gradient between the two ends of the cable assembly. The processing electronics utilizes a voltage controlled oscillator for automatic tuning thereby increasing the sensitivity of the measuring apparatus.

Abstract: This invention is an improvement in aircraft control systems that utilize feedback motion sensors to generate a control signal to control the aircraft. The improvement consists essentially of a complementary filter comprising a simplified model of the aircraft, a high-pass filter, a low-pass filter and a summing amplifier. The control signal is applied to the simplified model of the aircraft which ateempts to compute the vehicle response to the signal. This computed response is then fed into the high-pass filter to eliminate long-term errors in the calculated response, with the result that a good estimate of the high frequency content of the aircraft motion is obtained. In order to obtain a good estimate of the low frequency content of the motion a rate gyro signal is fed through the low-pass filter that eliminates all of the offending noise. The outputs from the high-pass and low-pass filters are summed by the summing amplifier to produce an estimated rate which is then used as a motion feedback signal.

Abstract: An indicator for recording the load at which a fatigue specimen breaks during the last cycle of a fatigue test. A load cell is attached to the specimen which is alternately subjected to tension and compression loads. The output of the load cell which is proportional to the load on the specimen is applied to the input of a peak detector. Each time that the specimen is subjected to a compression load, means are provided for appyling a positive voltage to the reset of the peak detector to reset it. Hence, during the last cycle of the tension load the peak detector measures the maximum load on the specimen. Means are also provided for disconnecting the load cell from the peak detector when there is a failure in the specimen.

Abstract: Apparatus for measuring an aircraft's horizontal speed and height above ground without the need for airborne cooperative devices. Two ground level TV cameras separated by a measured distance and pointed at zenith are placed in line with the projection of the expected path of the aircraft. Speed is determined by measuring the time that it takes the aircraft to travel between the fields of view of the two TV cameras using zenith crossings as the reference points. Height is determined by correlating the speed with the time required to cross the field of view of either of the two cameras.

Abstract: A device for generating burst signals that can be used to determine whether or not a laser doppler velocimeter is operating properly. A high frequency signal which corresponds to the information frequency of the laser doppler velocimeter is modulated by a low frequency signal to provide an envelope for the high frequency signal. The high frequency signal is modulated by the low frequency signal by any modulator means such as, for example, an analog multiplier. The low frequency signal is added to the modulated signal to provide pedestals for the resulting series of burst pulses. Then means are provided for selecting different combinations of these burst signals. Also means are provided for making the burst signals asymmetrical as desired. In addition, means are provided for varying the frequencies and amplitudes of the information, envelope and pedestal frequency signals in the burst signals.

Abstract: A device for measuring acoustic properties and their changes in a sample of liquid, gas, plasma or solid. A variable frequency source is applied to the sample by means of a transducer to produce sound waves within the sample. The application of the variable frequency source to the sample is periodically interrupted for a short duration. Means are connected to the transducer for receiving the resulting acoustic signals during the interruptions for producing a control signal indicative of a difference in the frequency of the output of the variable frequency source and the frequency of a mechanical resonant peak in the sample. The control signal is applied to the variable frequency source to maintain its output frequency at the frequency of the mechanical resonant peak. The change in frequency of the variable frequency source is indicative of the shift in frequency of the mechanical resonant peak and the amplitude of the acoustic signals is indicative of the attenuation of the acoustic signals in the sample.

Abstract: This invention is a high data rate pressure sensor module with an in situ calibration capability to help reduce energy consumption in wind tunnel facilities without loss of measurement accuracy. The sensor module allows for nearly a two order of magnitude increase in data rates over conventional electromechanically scanned pressure sampling techniques. The module consists of 16 solid state pressure sensor chips and signal multiplexing electronics integrally mounted to a four position pressure selector switch. One of the four positions of the pressure selector switch allows the in situ calibration of the 16 pressure sensors; the three other positions allow 48 channels (three sets of 16) pressure inputs to be measured by the sensors. The small size of the sensor module will allow mounting within many wind tunnel models, thus eliminating long tube lengths and their corresponding slow pressure response.

Abstract: A volumetric direct nuclear pumped laser has been developed in which the gas is a mixture of .sup.3 He and a minority gas from the group of argon, krypton, xenon, chlorine and fluorine. The mixture of .sup.3 He and the minority gas produces lasing with a minority gas concentration of from 0.01 to 10 percent argon, 1 percent krypton, 0.01 to 5 percent xenon and small concentrations of chlorine or fluorine.

Abstract: The invention is a device for measuring the contour of a surface. Light from a source is imaged by a lens onto the surface which concentrates the energy from the source into a spot. A scanning means is used to scan the spot across the surface. As the surface is being scanned the surface moves relative to the point of perfect focus. When the surface moves away from perfect focus the spot increases in size, while the total energy in the spot remains virtually constant. The lens then reimages the light reflected by the surface onto two detectors through two different sized apertures. The light energy going to the two detectors is separated by a beam splitter. This second path of the light energy through the lens further defocuses the spot, but as a result of the different sizes of the apertures in each light detector path, the amount of defocus for each is different. The ratio of the outputs of the two detectors which is indicative of the contour of the surface is obtained by a divider.

Abstract: This invention is a corrugated horn antenna that is readily collapsible while not in use. A plurality of different sized annular metal rings are arranged in a sequence such that each ring is larger than the one that precedes it in the sequence. A plurality of thin flexible electrically conductive members attach successive metal rings together physically and connect them together electrically. Each flexible conductive member is attached to make electrical contact between the outside surface of a metal ring and the inside surface of an adjacent metal ring in the sequence.

Abstract: The magnetometer transducer includes a group of plated magnetic wires arranged in parallel physically and connected in series electrically to serve as a drive circuit, and several turns of 0.025 mm diameter wire wound around the group of plated magnetic wires to serve as a sense coil. Each of the magnetic wires has a diameter of 0.05 mm with their centers being 0.25 mm apart. Because of its shape and small size, it is capable of very good spatial resolution of magnetic fields as low as 0.02 oe and it can make measurements of transverse magnetic fields as close as 0.08 mm from a surface. The magnetometer utilizes two X-Y recorders in a unique transducer scanning technique. One of the recorders moves the transducer over the specimen being measured and the other recorder records the measurements.

Abstract: Apparatus for providing accurate pointing of instruments on a carrier vehicle and for providing isolation of the instruments from the vehicle's motion disturbances. The apparatus includes two assemblies, with connecting interfaces, each assembly having a separate function. The first assembly is attached to the carrier vehicle and consists of an azimuth gimbal and an elevation gimbal which provide coarse pointing of the instruments by allowing two rotations of the instruments relative to the carrier vehicle. The second or vernier pointing assembly is made up of magnetic suspension and fine pointing actuators, roll motor segments, and an instrument mounting plate around which a continuous annular rim is attached which provides appropriate magnetic circuits for the actuators and the roll motor segments.

Abstract: The invention is an optical scanner that sequentially focuses optical energy (light) at selected points in space. The essential component of the invention is a scanning wheel including several glass windows with each window having a different thickness. Due to this difference in thickness, the displacement of the emerging light from the incident light is different for each window. The scanner transmits optical energy to a point in space while at the same time receiving any optical energy generated at that point and then moves on to the next selected point and repeats this transmit and receive operation. It fills the need for a system that permits a laser velocimeter to rapidly scan across a constantly changing flow field in an aerodynamic test facility.

Abstract: This invention is a CW ultrasonic device for measuring frequency shifts of the peak of a mechanical resonance in a body. One application of the device is measuring the strain in a bolt. It also has other applications such, for example, as measuring the thickness of a body, measuring the depth of a flaw in a body, measuring the elongation of body and measuring changes in velocity of sound in a body. The body is connected, by means of a CW transducer, to electrical circuit means including a narrow band RF amplifier to form a closed loop feedback marginal oscillator that frequency locks the device to the peak of a mechanical resonance in the body. Thereafter, when the frequency of this peak changes, because of a physical change in the body, the frequency of the oscillator changes. The device includes an automatic frequency resonant peak tracker that produces a voltage that is related to a change in frequency of the oscillator.

Abstract: An apparatus is disclosed for monitoring the development and growth of fatigue cracks in a test specimen subjected to a pulsating tensile load. A plurality of television cameras photograph a test specimen which is illuminated at the point of maximum tensile stress. The television cameras have a modified vidicon tube which has an increased persistence time thereby eliminating flicker in the displayed images.

Abstract: This invention is a device for measuring small differences between relatively high sound pressure levels at two different microphone sites. It provides electrical insertion voltages, "pilot" voltages, as a means for continuously monitoring the gains of two acoustical channels. The difference between two pilot voltages is utilized to force the gain of one channel to track the other channel.

Abstract: Apparatus for directly measuring the quantity .sqroot..rho.ck of a test specimen such as a wind tunnel model where .rho. is the density, c is the specific heat and k is the thermal conductivity of the specimen. The test specimen and a reference specimen are simultaneously subjected to the heat from a heat source. A thermocouple is attached to the reference specimen for producing a first electrical analog signal proportional to the heat rate Q that the test specimen is subjected to and an infrared radiometer that is aimed at the test specimen produces a second electrical analog signal proportional to the surface temperature T of the test specimen. An analog-to-digital converter converts the first and second electrical analog signals to digital signals. These digital signals are applied to a computer for determining the quantity .sqroot..rho.ck by computing the quantity ##EQU1## WHERE T.sub.

Abstract: A method for locating any person in distress in a selected area on the surface of the earth who has deployed passive radio frequency (RF) reflectors in a predetermined arrangement. A first transparency is made in the spatial frequency domain of an image of said predetermined arrangement of said RF reflectors. The said selected area of the surface of the earth is scanned by means of a side-looking radar, on board a satellite or aircraft, to produce radar images. Second transparencies in the conventional image domain are produced from the radar images. It is then determined from the first and second transparencies, by means of complex spatial filtering, if RF reflectors in said predetermined arrangement were deployed in said selected area when scanned by said radar.

Abstract: A method for making a glass-to-metal seal. A domed metal enclosure having a machined seal ring is fitted to a glass post machined to a slight taper and to a desired surface finish. The metal part is then heated by induction in a vacuum. As the metal part heats and expands relative to the glass post, the metal seal ring, possessing a higher coefficient of expansion than the glass post, slides down the tapered post. Upon cooling, the seal ring crushes against the glass post forming the seal. The method results in a glass-to-metal seal possessing extremely good leak resistance, while the parts are kept clean and free of contaminants.

Abstract: Apparatus for superimposing numerical information on the field of view of binoculars. The invention has application in the flying of radio-controlled model airplanes. Information such as, for example, airspeed and angle of attack are sensed on a model airplane and transmitted back to earth where this information is changed into numerical form. Optical means are attached to the binoculars, that a pilot is using to track the model airplane, for displaying the numerical information in the field of view of the binoculars. The optical means includes means for focusing the numerical information at infinity whereby the user of the binoculars can see both the field of view and the numerical information without refocusing his eyes.