Abstract: A strain sensor has a first optical fiber (212) including first (212e.sub.1) and second (212e.sub.2) ends and also includes lead-in (12) and lead-out (16) optical fibers. One (12) of the lead-in and the lead-out fiber has a first end (12e) affixed to the first end of the first fiber, forming a first partially reflective surface (214). The other one (16) of the lead-in and lead-out fibers has a first end (16e) located at a second distance (S) from the second end (212e.sub.2) of the first fiber (212). The sensor includes a glass tube (30), with a bore (32), affixed to at least the other one of the fibers, and holds the first end of the other one of the fibers to define coaxial partial reflectors (14, 18) at the second end (212e.sub.2) of the first fiber and the first end (16e) of the other one of the fibers. In one embodiment, the one of the fibers is the lead-in fiber.

Abstract: Multiphase ceramic composites containing 47% to 52% by weight aluminum nitride, 23% to 27% by weight silica, 3% to 7% alumina and the balance boron nitride wherein the boron nitride is one phase in the composition and the reaction products of aluminum nitride, silica and alumina are the other phase in the composite. The boron nitride phase is uniformly distributed in the form of discrete particles throughout the reaction products of aluminum nitride, silica and alumina. A window transparent to electromagnetic radiation in a predetermined frequency spectrum is made by forming a homogeneous, finely-divided mixture of the foregoing composite and compacting the homogeneous, finely-divided mixture at an elevated temperature and pressure for a sufficient time to form reaction products of the aluminum nitride, silica and alumina. In preferred embodiments, the homogeneous, finely-divided mixture of aluminum nitride, silica, boron nitride and alumina is densified at a temperature of 1760.degree. C.

Abstract: A spacecraft includes a plurality of paralleled RF amplifiers. Each paralleled power amplifier (206) includes a signal splitter (222) which produces two nominally equal-amplitude signals, and a signal combiner (242) which combines appropriately phased signals to produce a sum signal at a sum port (250). The signal combiner also includes a null output port (248). A pair of elemental amplifiers (236, 238) is coupled between the splitter outputs and the combiner inputs. In order to allow for phase drift of the elemental amplifiers, at least one phase shifter (258) is associated with one of the elemental amplifiers. A phase control loop is coupled from the null output of the combiner, around the paralleled amplifier arrangement, and controls the phase shifter to maintain the phase within bounds, to maximize the signal at the sum port of the combiner.

Abstract: In a time division multiple access spacecraft communication system, each ground station determines when to send its information packets to arrive at the spacecraft at the beginning of a time slot. The calculation is based upon knowledge of the locations of the spacecraft and the transmitting ground station. A master ground station determines the location of the spacecraft by the use of the propagation delays between the various ground stations (including itself) and the spacecraft, together with knowledge of the locations of the ground stations. The spacecraft location is then transmitted back to the various ground stations. The determination of propagation delay by each ground station is performed by repeatedly transmitting a ranging signal containing a multiple-bit unique word to the spacecraft, and counting spreading code chips until the next unique word is received from the spacecraft.

Abstract: An assembly of logic devices intercommunicates, at least in part, by way of a data and address bus, which may not be accessible from outside the assembly. Consequently, the various logic devices, such as memories and other logic functions, cannot be directly tested. The assembly includes a field-programmable gate array (FPGA), which is programmed to perform a particular function during normal operation of the assembly. The FPGA is reconfigured during a test mode of operation into a built-in self-test (BIST) device capable of testing the various logic devices, without requiring significantly more resources on the assembly.

Abstract: A spacecraft (12) cellular TDMA communications system (10) includes many user terminals (16), some of which may be movable. The spacecraft repeats transmissions by way of spot beams (20). A user initiates communication by synchronizing to the TDMA slots (210, 212), and transmits an access request signal. The access request signal is transmitted in at least two slots. The first slot contains time and frequency PN synch information, and the second slot contains one of (a) the user terminal's ID code and (b) a code representing the desired type of access. After this message is transmitted and received, the user terminal may transmit the PN synch information on a third slot, followed by the other one of the user terminal's ID code and the access-representative code.

Abstract: A spacecraft of a set of spacecraft has an antenna support frame defining square apertures, which are the same size in all spacecraft of the set of spacecraft. The set also includes a plurality of radiating tiles for various operating frequencies. The tiles all have the same dimensions, so that any combination of tiles may be mounted in the apertures of the frames of any spacecraft to form antenna arrays of various sizes, depending upon the customer's requirements. Each tile includes plural beamformers and power amplifiers, and remotely controllable phase shifters and level controls, for ready reconfiguration of the antennas while the spacecraft is in operation. The preferred dimension of each radiating tile is a one-foot square.

Abstract: In a time division multiple access spacecraft communication system, each ground station determines when to send its information packets to arrive at the spacecraft at the beginning of a time slot. The calculation is based upon knowledge of the location of the spacecraft. A master ground station determines the location of the spacecraft by the use of the propagation delays between the various ground stations (including itself) and the spacecraft, together with knowledge of the locations of the ground stations. The spacecraft location is then transmitted back to the various ground stations. The determination of propagation delay by each ground station is performed in two major steps. The first step determines coarse time delay to within one bit interval by repeatedly transmitting a multibit unique word to the spacecraft, and counting bits until the next unique word is received from the spacecraft.

Abstract: A microphotonic circuit includes one or more light control elements such as modulators or switches coupled in polymer waveguides, and controlled by electrical bias fields produced by voltage or light sources. Each modulator or switch includes at least one polymer waveguide having a high-.eta. core and surrounding low-.eta. cladding, to constrain the light. An electrooptic control element is evanescently coupled to the core of the first waveguide by spacing from the core. The coupling between the core and the control element depends upon the relative .eta.s of the core, cladding and electrooptic element. Bias is applied to maintain the electrooptic element in one of at least two possible states, one of which prevents coupling between the electrooptic element and the core, and the other of which permits such coupling. The bias may be applied in the form of electrical voltage or light. In some embodiments of the invention, a second optical waveguide is coupled to the electrooptic element.

Abstract: A pneumatically operated autobalance arrangement includes a hub which connects a shaft with a driven rotational element. The hub is fitted with a plurality of circumferentially-acting bellows which move weights about the hub. The inflation state of each bellows is determined by an air gap, which varies in dimension depending upon the amount and location of an imbalance of the driven element. The pneumatic pressure can be generated by a turbine driven by the shaft. Force amplification is provided in another embodiment. Autobalance hubs can be stacked axially to provide two-plane dynamic balance.

Abstract: A spacecraft includes a body defining a center of mass, and an attitude control system, for generating attitude error signals representing deviation of the body from a desired attitude. A plurality of thrusters mounted on the body have nominally parallel thrust components, in a particular direction. The thrusters are arranged in pairs, which produce opposed torques. A velocity change controller is coupled to the thrusters, for generating pulsatory firing command signals for the thrusters for a particular total time duration, for achieving a desired velocity change in the desired direction.

Abstract: An acoustic array handler (10) includes an elongated linear guide channel (14U, 14L) in which upper (18U) and lower (18L) trains of suction heads (18su) are longitudinally movable. Each suction head (18su) has a porous part shaped to fit the array hose, and together the two trains of suction heads hold the array along the length of the channel. A pump is coupled to the channel for applying suction to the channel and, through the suction heads, to the hose. When immersed in seawater, the pump creates a negative pressure within the channel and the suction heads, which is communicated to the hose, drawing the hose into intimate contact with the trains of suction heads. The trains of suction heads are powered so as to drive them through the channel, drawing the hose with them. In one embodiment of the invention, each of the trains of suction heads is an endless loop, which recirculates through the channel under the impetus of pulleys or sprockets.

Abstract: A hybrid electric vehicle includes a lead-acid traction battery made up of a plurality of series-connected modules. During operation of the vehicle, the traction battery is discharged for acceleration, and charged by an ancillary power source. The traction battery is desirably not fully charged at the beginning of a day's operation, so that overcharging cannot occur, so the battery spends long periods of time in a partially charged condition. When not fully charged for long periods of time, sulfation may reduce the charge storage capacity of the battery. A maintenance procedure takes place when the vehicle is not operating, in which one or more modules of the traction battery, but less than all the modules, are fully charged, then partially discharged. The full charging tends to reduce sulfation in the particular module being maintained, and the partial discharge restores its charge condition to that prior to the full charge. Each of the modules is eventually maintained by a programmed controller.

Abstract: A control system for the uplink transmitter of a ground station communicating with a spacecraft includes an antenna located at the ground station, pointed toward the spacecraft for receiving downlink signals transmitted therefrom. The received signals are accompanied by noise attributable to ambient, sky and ground temperatures. A low-noise receiver is coupled to the output port of the antenna, for establishing the receiver noise temperature. A processor is coupled to the low-noise receiver apparatus and to the power control input port of the uplink transmitter, for responding to changes in the received noise power attributable to the presence or absence of precipitation in the downlink. The processor does this by producing an estimate of the attenuation attributable to the rain in the downlink, and generates the control signal in response to the estimate of the attenuation.

Abstract: A spacecraft includes heat-generating payload equipment, and a heat transport system with a cold plate thermally coupled to the equipment and a capillary-wick evaporator, for evaporating coolant liquid to cool the equipment. The coolant vapor is coupled to a condenser and in a loop back to the evaporator. A heated coolant reservoir is coupled to the loop for pressure control. If the wick is not wetted, heat transfer will not begin or continue. A pair of check valves are coupled in the loop, and the heater is cycled for augmentation pumping of coolant to and from the reservoir. This augmentation pumping, in conjunction with the check valves, wets the wick. The wick liquid storage capacity allows the augmentation pump to provide continuous pulsed liquid flow to assure continuous vapor transport and a continuously operating heat transport system. The check valves are of the ball type to assure maximum reliability.

Abstract: Aluminum-lithium plates are butt-welded by juxtaposing the plates and making a preliminary weld from the rear or root side of the seam. An initial weld is then made from the face side of the seam, which may cause a defect in the root portion. A full-size X-ray is made and overlain over the seam to identify the defects. The defect is removed from the root side, and rewelded. Material is then removed from the face side, and the cavity is rewelded. The procedure repeats, alternating from the root side to the face side, until the weld is sound.

Abstract: A spacecraft (10) has an attitude sensor (20) mounted on its body (12). The sensor must be maintained near a temperature setpoint. Each sensor (20) produces its own temperature-indicative signal. Each attitude sensor is coupled to a thermally conductive instrument platform (18). A standoff (21) supports the platform (18) away from a baseplate (16) and the spacecraft body (12). The standoff (21) includes a thermally conductive portion (22) adjacent the platform (18), and a nonconductive portion (24) remote from the platform. An electric heater (26) is connected to the thermally conductive portion (22) of the standoff (21). A temperature sensor (28) thermally coupled to the platform (18) generates platform temperature signals. A filter (212) high-pass filters either the platform temperature signals or the attitude sensor temperature signals, to form filtered signals. A combining circuit (218) combines the filtered signals with the other temperature signals, to make composite temperature signals.

Abstract: A Tripulse method determines the orientation or attitude of a phased-array antenna located at a remote site, such as an aircraft or spacecraft. Three pulses are transmitted from the phased-array antenna in an estimated direction toward a coherent receiver, with a sum beam, and with first and second difference beams formed by reversal of the phase of certain elements above a first axis of symmetry, and to one side of a second axis of symmetry. The received signals are processed in a manner which determines the error between the assumed direction and the actual direction of the receiver. To determine the rotational position of the array antenna, the same steps are performed for a second remote receiver, and additional processing determines the complete attitude, including yaw, of the phased-array antenna. The coherent receiver may use the first transmitted pulse as a reference, or it may use a separate reference signal.

Abstract: A hermetically sealed housing for plural GaAs chips includes a body made from Al/SiC. The body defines a peripheral seal ring support surface, an electrical connector insert support surface and an end wall to which a ceramic insert is mounted. The insert includes a first portion with an upper surface within the sealed housing, Which upper surface is coplanar with the upper surface of the body, for convenient HDI film connections to the chips and electrical connector inserts. The refractory electrical conductors extend from the upper surface of the first portion of the insert to an exterior terminal portion of the insert. The terminal portion of the insert is spaced from the first portion of the insert by a non-terminal portion containing no terminals. The non-terminal portion of the insert is coplanar with the seal ring support surface of the body, and contiguous therewith.

Abstract: Semiconductor devices made in highindium-content semiconductor material have advantageous properties, but similar substrate materials are hard to handle. A buffer layer makes a lattice-constant transition between a GaAs substrate and a high-indium epitaxially deposited semiconductor such as those lattice-matched to InP. The buffer layer is an epitaxial layer including atoms of two Group III elements, and atoms of two Group V elements, with the ratio of the atoms of at least one group varied along the depth of the buffer layer, in a manner which makes a transition of the lattice constant between that of the substrate and the high-Indium semiconductor material. The Group III elements are gallium and aluminum, and the Group V elements are arsenic and antimony.