Abstract: The invention is a helicopter blade crack detection system for blades that are hollow and pressurized or evacuated to a low pressure A rotating assembly having a rotating indicator assembly photo-optically communicates to an airframe detection assembly providing high reliability, ease of maintenance, and EMI secured.

Abstract: A fuel cell stack is cooled by evaporation of water into a carrier gas such as fuel or oxidant. The coolant and the carrier gas are separately supplied to the cooler, and this allows the fuel cell to operate at high pressure without raising cell temperature.

Abstract: A digitizer, which comprises integrated circuit cards designed to attach to an expansion slot in an IBM PC/AT, operates at 20 megasamples per second for approximately 52 milliseconds and provides eight bit resolution on the signal input. The computer software includes a device driver for the digitizer. A flash analog-to-digital converter (ADC) in a single IC package has an analog input coupled to the video signal source. The data line from the ADC circuit goes to a SRAM (Static Random Access Memory) memory made up of four identical banks which are interleaved together so that slower less costly memory chips can be used. An interface circuit provides communication between the computer and the digitizer, with address, data and control lines. A sync pulse from the video tape unit is monitored by a sync pulse input comparator to trigger the start of a digitizing sequence.

Abstract: In a deformable mirror having a mirror face plate and a plurality of axially movable piezoelectric actuators for controlling the contour thereof, an improvement is provided by which a pneumatic pre-load assembly is inserted between the face plate and the actuators. The assembly includes a core, having apertures therethrough, with a plurality of mirror surface contour posts passing separately through said apertures and a diaphragm plate which is mounted between the face plate and the core and spaced from such face plate but in contact with such core and one end of the posts. A rear plate is mounted to the other end of such posts and in spaced proximity with the core, which core, together with the diaphragm plate and the rear plate, define a cavity therebetween. The posts are aligned with actuators on the other side of the rear plate. Gas is applied to such cavity to bring the posts and the rear plate into contact with their associated actuators so as to pre-load them.

Abstract: A surveying satellite apparatus having an on-board microprocessor to process sensor-provided data from planetary and/or celestial reference scene. The sensor data is compared with the on-board spacecraft database to determine if any misorientation or translation error is present. The spacecraft attitude and ephemeris solutions are autonomously updated to reflect the realtime alignment.

Abstract: A gas turbine pyrometer filtering method and system uses a pyrometer to measure the high pressure turbine blade temperatures using infrared optical detection techniques. The pyrometer signal can be cluttered by positively biased noise. The turbine speed and the pyrometer electrical signal are alternately sampled by an analog to digital converter, and several revolutions of pyrometer data are stored in the local RAM. A data compression algorithm then selects single samples, at evenly spaced intervals, which results in a given number of revolutions, containing an exact number of data points of aligned data in RAM. This data is passed to a clutter rejection filter which then passes only the lowest value for each of the points in all revolutions of data. Thus, the revolutions of acquired data are reduced into a single revolution of filtered data for the current sampling. This single revolution of filtered data in then enter into a circular queue and the last element is discarded.

Abstract: Both the low and high intermediate frequencies (IF) are amplified simultaneously in a single IF amplifier strip. For proper operation it is required that the two IFs be sufficiently isolated from each other so that independent tuning can be achieved. In operation, the RF signal is amplified and mixed down by a first local oscillator (LO). The RF signal is amplified in the IF strip to obtain IF #1. IF #1 from the strip is mixed down with a second LO in a feedback arrangement to obtain IF #2 simultaneously with IF #1 from the strip.

Abstract: An in-circuit test probe apparatus for probing the finely and closely spaced leads of an LSI circuit package in order to monitor the signals on the pins. A magnetic holding assembly is utilized to attach the test probe apparatus to the circuit package which is positioned with a cavity in the bottom of the test probe apparatus. A layer of silicon rubber is positioned between rough and fine probe pin location members to hold the probes during test and to allow easy insertion and removal of the test probe.

Abstract: In order to measure the far field antenna pattern of a phased array antenna, the phased array is focused at a probe antenna which is a specific distance away from the aperture. The antenna pattern is then measured by moving the probe antenna on a constant focal arc. This arc minimizes phase aberrations due to defocusing error. To minimize amplitude errors, the pattern of the probe antenna is carefully matched to compensate for the variation induced amplitude error.

Abstract: A system for decoding an IF signal modulated with 4-ary words generated at a known spreading rate (PN code) comprises a receiver in which four known 4-ary words are generated at the same rate. The system then compares the incoming signals modulated with unknown 4-ary words with each of four known 4-ary words. Only one of the known words will be in phase with a received unknown word. The disclosure describes a system which determines which of the four words is in phase, this being the determinant of the identity of the unknown word.

Abstract: A process, known as the Hick's Probabilistic Data Association Algorithm, correlates sensor measurement to target tracks under condition in which there are numerous false measurements. It accomplishes this by forming multiple hypotheses and computing a probabilistic score for each. The hypothesis with the high score is then used as a probability vector to update each target's track. The result is accomplished by combining the attributes of Joint Probabilistic Data Association (JPDA) and Nearest Neighbor Standard Filter (NNSF). This combination provides an improved algorithm which yields improved performance ever both prior art methods under high clutter conditions with crossing targets.

Abstract: A new type of laser structure utilizes field-effect at a self-aligned p-n junction to control the current flow into the active quantum well region. The HFET laser structure is identical to the corresponding HFET transistor and is realizable with the same fabrication technology. The optical properties of the laser are optimized simultaneously with the electrical properties of the FET and thus the prospect of opto-electronic integration of the laser and the transistor are excellent.

Abstract: This is a methodology which reduces the time required to render a volume with extracted isocontours and inserted cutting plane and perform an arbitrary rotation within a three-dimensional volume. The volume is first partitioned among the processors of a multiple-instruction, multiple-data (MIMD) multiprocessor computer. As the user indicates the isocontour to be extracted, rotation, and cutting plane to be inserted into the image space volume, each processor independently selects the optimum algorithm for rendering the volume using the indicated display parameters on its local data set. If the processor is fully behind the cutting plane, a front-to-back (FTB) volume rendering algorithm is used. If the cutting plane lies behind the cutover point, then a back-to-front (BTF) volume rendering algorithm is used, otherwise the FTB volume rendering algorithm is used.

Abstract: Rigid-rod aromatic heterocyclic polymers having repeating units of the formula: ##STR1## wherein Ba is a benzobisazole moiety of the formula: ##STR2## wherein X is --O--, --S-- or --NH.

Abstract: A spar assembly jig for tack-free positioning of aircraft spar components for subsequent fastening at a second location. Pneumatically operated clamps are mounted on the frame of such jig. The spar components are laid up in such jig and the clamp closed thereon to hold the members together as opposed to the prior art method of securing such components together by temporary fasteners or tacking. The assembly jig and so-assembled and clamped spar components are then transported by overhead crane to an automatic riveting machine. The riveting machine has a jaw defined by a spindle and anvil which fits above and below the jig assembly. The clamps have a swing-away feature such that as the spindle and anvil approach, the clamp swings out of the way so that such machine can drive a rivet through endcap and web at or near the spot vacated by the swing-away clamp. The machine then moves on and the clamp re-closes on the spar components.

Abstract: A method of separating structure comprising first and second components having different coefficients of thermal expansion and bonded together with a bonding material. Separation is achieved by immersing the structure in a cryogenic cooling substance to break the bonding material as a result of the different rates of expansion of the two components and then applying a force to separate the two components. Separation of a rotor and its windings is disclosed.

Abstract: An improved commutation arrangement for an AC to AC or AC to DC energy converter circuit is disclosed. The improved arrangement uses turn-off capable commutation switches to enable modification of the operating waveforms in the cycloconverter. The modified waveforms include an operating concept wherein in lieu of always switching to the next lagging phase (as is done with conventional cycloconverters), an intervening switch is made to the leading phase when the output voltage is less than one-half of the maximum value. The disclosure includes mathematical consideration of source machine power factor, output waveform ripple content, interphase transformer characteristics, engine starting usage, and other refinements of the commutation arrangement.

Abstract: An aircraft attitude display format which maintains the horizon reference line always in view and which presents the pilot with multiple indications of aircraft attitude differing from level flight. The multiple indications include attitude registration along an angular scale and shape change of the horizon reference line. The display format has the appearance of a fish-eye lens derived optical image and is preferably placed in this form by electronic image processing--which is exemplified by an included mathematical discussion and computer code listing software. Provisions for other data display are also disclosed. Use of the display format in a panel instrument or CRT-based system including the HUD configuration are contemplated.

Abstract: The testing device, also known as a totally integrated payload attitude control tester (T.I.P.A.C.T.), is suspend on a single, high strength, low torsional moment line through the gravity vector axis. Attached directly to this line is a strong back assembly having a fixed lateral width with ends thereon. Attached to the ends of the strong back assembly are thin, high strength straps which are connected to a pair of tensile universal joints which are further connected to, by way of this high strength straps, to a pair of trunnions. The trunnions are connected to the payload support frame which may have a satellite payload therein. The three orthogonal axes of the test device allow rotation to .+-.45 degrees, .+-.60 degrees and >360 degrees, simultaneously in roll, yaw, and pitch respectively. The thin fabric strap allows movement with virtually no friction or suspension resistance.

Abstract: A radioactively biased optical power limiter device is described which comprises first and second lenses disposed along an optical axis with a common focal plane therebetween, the first lens disposed for receiving electromagnetic energy input directed along the optical axis and focusing the input at the focal plane of the first and second lenses, a cell of optically nonlinear material disposed along the optical axis at the focal plane of the lenses, and a radioactive source of ionizing radiation disposed near or in the nonlinear material for selectively controlling the electromagnetic field level necessary to cause optical nonlinear effects in the cell.