Abstract: A gas gun has a charge chamber, an inlet valve to admit a charge of compressed gas to the charge chamber and either a plane or rifled barrel which communicates at its breech end with the charge chamber via a rotary outlet valve. Preferably the inlet valve is linked to the outlet valve so that closing of the inlet valve immediately precedes the opening of the outlet valve. The outlet rotary valve includes a frestoconical valve member which rotates within a complementary seat and has a radial bore which can connect two or more ports in the wall of the seat and is strongly biassed to the open position. The inlet and outlet valves may be combined in a three-way valve. In use a projectile is placed at the breech end of the barrel and the inlet valve is opened and the outlet valve closed. After compressed gas, preferably helium, has been introduced to the charge chamber to the desired pressure, the gun is fired by closing the inlet valve and immediately thereafter opening the outlet valve.

Abstract: In a radiation detector including a substrate of photoconductive material having input and output contacts, the photocarrier flow-path between the two contacts includes regions of conductive material. These regions may be formed as strips overlying the substrate, or may be formed in grooves in the substrate. Alternatively, the substrate may comprise a number of separate regions of photoconductive material interconnected by regions of conductive material. The substrate is preferably of cadmium mercury telluride photoconductive material and the conductive regions of gold. Chromium may be used to provide a bond between the gold and cadmium mercury telluride. The substrate may be slotted to increase flow-path length between the two contacts.

Abstract: A thrust unit for a space vehicle has a container in which an electrolyte is electrolyzed to produce combustible gases (for example, water producing hydrogen and oxygen). At a predetermined pressure the gases are ignited and combustion products are exhausted from the container through a thrust nozzle. The pulsed nature of the thrust unit operation, and the duration of each pulse, are such that overheating of the unit is avoided.

Abstract: A process for preparing a surface for adhesive bonding to a second surface having the steps of abrasion cleaning the surface and then applying an adhesive thereon, wherein the improvement over prior art processes comprises the displacement of atmospheric gases from the surface by means of a dry inert gas. The abrasion cleaning is preferably achieved by bombarding the surface with particulate matter and removing the particulate matter before application of adhesive to the surface. The process is suitable for preparing metal surfaces for metal to metal bonds.

Abstract: A hydraulic servo valve suitable for controlling flow of a pressurized fluid in dirty and explosive environments, comprises a control valve actuated by a contamination-free sealed pilot circuit of electroviscous fluid commanded by electroviscous valves requiring minimal electrical power. Fluid is circulated in the pilot circuit by pressure pulses derived from the pressurized fluid by means of a fluidic oscillator and transmitted to the pilot circuit via flexible diaphragms.

Abstract: A reflector antenna comprising a reflector system, and a feed system, for instance a log-periodic feed system, the phase center of which moves with frequency, for illuminating the reflector system to produce a substantially focussed antenna beam. To compensate for frequency variations in the position of the phase-center of the feed system, the reflector system includes a frequency dependent reflector the effective surface of reflection of which varies with frequency to cause the focus of the reflector system to move with the phase-center of the feed system. A number of different forms of suitable frequency dependent reflectors are described, employing composite arrangements frequency selective mesh or grid reflector elements, or arrays of reflecting horns or wedges.

Abstract: A method of fabricating a series-connected combination of two-terminal semiconductor devices on a common substrate comprising: forming a layer of high quality semiconductor material, 4, on the surface of a temporary substrate, 2 and 3, to provide active areas for the devices, forming first contact pattern conductors, 6, 9, 10, on the free surface of the high quality semiconductor layer to provide a separate first contact to this layer for each of the devices, bonding an insulating support substrate, 12, to the first contact pattern, removing the temporary substrate, forming second contact pattern conductors, 17, 18, 19, on the other surface of the high quality layer to provide a separate second contact to this layer for each of the devices, removing regions, 8, of the high quality layer separating the conductors of a pattern at any stage after beginning formation of the first contact pattern in order to define the device active areas so that parts of the first contact pattern are exposed when both the tempora

Abstract: A length of microstrip line turns through successive right-angle corners to form a rectangular pattern comprising successive quartets of such corners. Each right-angle corner radiates with a polarization which is predominantly diagonal, and the strip lengths between the corners of each quartet are made such, in relation to the operating wavelength in the strip, that the radiation from each quartet sums to produce a desired polarization direction, e.g. vertical, horizontal, or circular of either hand. Some forms of the invention can be used in a resonant as well as a travelling-wave mode, the latter giving a main lobe whose direction sweeps with frequency.

Abstract: An ultrasonic flaw detection system automatically measures attenuation of an input signal from a receiver transducer that provides a reference level. Successive amplifier stages having stepped gains provide graduated output levels that are detected and stored by individual peak readers. Sampled output levels are compared in comparators and with a reference voltage generated by a digital-to-analog converter to produce a binary output corresponding to each signal as a first coarse attenuation level. Logic control and timing circuitry selects the output level corresponding to one of the signals having a peak voltage in a predetermined range. A logarithmic converter and comparator provide a fine attenuation reading which is summed with the coarse reading in digital form. This is decoded and displayed as a total attenuation readout.

Abstract: A method of fabricating a field effect transistor comprising the steps of forming an active layer of semiconductor material (GaAs) over a surface of a first substrate of semiconductor material (GaAs), applying a second substrate of insulating material, e.g. glass, over the surface of the active layer, removing the first substrate so that the active layer is now supported on the insulating second substrate, and forming source, drain and gate electrodes over the free surface of the active layer. To facilitate removal of the GaAs first substrate by selective etching, a buffer layer of GaAlAs resistant to the GaAs etchant, may be formed between the active layer and the first substrate, which buffer layer is removed, following removal of first substrate, using a selective etchant to which the GaAs active layer is resistant. The technique is particularly applicable to high frequency FETs requiring a very thin active channel region interfaced to a substrate having good insulating properties.

Abstract: A method of fabricating a field effect transistor comprising the steps of forming an active layer of semiconductor material, e.g. GaAs over the surface of a first substrate of semiconductor material, e.g., also GaAs, forming source, drain and gate electrodes over the surface of the active layer, applying a second substrate of insulating material to the surface of this structure, and removing the first substrate. To facilitate the removal of the GaAs first substrate by selective etching, a buffer layer of GaAlAs resistant to the GaAs etchant may be formed between the first substrate and active layer, which buffer layer is removed, following removal of the first substrate, using a selective etchant to which the GaAs active layer is resistant. A second gate electrode may be formed on the active layer following removal of the first substrate. The technique is particularly applicable to high frequency FET devices.

Abstract: Scanning radiation source detecting apparatus, comprising means for deriving a general response signal in response to radiation from any part of a field of view, and a central response signal in response to radiation from a central part of the field of view, with means for producing audio signals of a frequency dependent on the magnitude of the central response signal. The apparatus may produce a constant frequency signal in response to the general response signal, and the central response signal may be derived from the general response by a gate circuit controlled by a scanning mirror mechanism. The gate circuit may be connected to a voltage controlled oscillator by a sample-and-hold circuit or, by an integrating circuit. Alternatively the apparatus may comprise a light emitting diode energized by a radiation detector, an optical system arranged to form an image of the diode and two separate detectors placed in the optical system to form the general response and central response signals.

Abstract: A method of fabricating a field effect transistor comprising the steps of forming an active layer of semiconductor material, e.g., GaAs, over a surface of a first substrate of semiconductor material, e.g., also GaAs, forming a gate electrode on the surface of the active layer, applying a second substrate of insulating material to the surface of this structure, removing the first substrate, and forming source and drain electrodes on the opposite surface of the active layer to the gate electrode. To facilitate removal of the GaAs first substrate by selective etching, a buffer layer of GaAlAs resistant to the GaAs etchant, may be formed between the active layer and the first substrate, which buffer layer is removed, following removal of the first substrate, using a selective etchant to which the GaAs active layer is resistant. A second gate electrode may be formed on the opposite surface of the active layer to that on which the first gate electrode is formed.

Abstract: An accelerometer includes a thermocouple circuit which comprises a movable member and a second member which abuts the movable member, wherein the abutting parts of the members include a cutting portion and wherein said parts are composed of dissimilar metals, for example steel and tungsten carbide, and recording means connected to the members for recording a thermoelectric signal generated when the cutting portion cuts the abutting part of the other member during acceleration.

Abstract: A fascine capable of conforming to the contours of a supporting surface, comprises a core of loose cylindrical pipes disposed within a surrounding sleeve of similar pipes transversely and continuously inter-connected by flexible ties. Binding straps attached to the sleeve are reeved so as to cause axial pleating of the sleeve when tensioned, thereby to bind the core into rigid cylindrical form. The fascine is transported in bound condition and the binding straps slackened on deployment.

Abstract: A sliding breech block suitable for rapid, semi-automatic operation of a bag charge gun comprises two interlinked portions mutually engageable in two dispositions at a stepped interface one of the portions being drivable in a transverse guideway by gun runout via a crank and a shaft, and the other portion being guidable by rollers engaged in cam tracks to follow a semi-arcuate path aligned at one end with the gun barrel axis and at the other with the guideway axis.

Abstract: An apparatus for transferring television pictures onto cine film which operates independent of field scan frequency and which synchronizes each frame of the cine film with the television field scans to avoid the appearance of a bar across each frame. The apparatus comprises a cine camera which in operation is placed in front of a television screen and which generates a shutter opening signal, a control unit which synchronizes that signal with the video signal to the television such that the shutter opens at the beginning of a field scan, and a motor drive unit which utilizes the video signal to drive the camera shutter blade at one third the field scan frequency. The apparatus is useful for transferring television field scans operating at any frequency onto cine film.

Abstract: A fuel tank largely filled with a plurality of discrete impermeably walled cells, the cells and the space between them and the tank sides and roof being substantially filled with fire protective reticulated structure. The cells are each plugged into one of a plurality of fuel collection networks, via non-return valves which prevent return flow of the fuel into the cells. The region between the cells and the tank walls is arranged to receive incoming fuel which then flows from the ullage into the cells, and, by means of a self switching pump, is also arranged to empty preferentially. The purpose of the invention is to minimize fuel loss and fuel fire in the event of a tank rupture.

Abstract: A decompression bubble detector comprises a pulsed ultra-sound transmitter/receiver which is scanned across a cross-section of tissue and the total number of pulse echoes received in a preselected time interval is recorded. Changes in the total number of pulse echoes recorded in successive time intervals are used to monitor the decompression. A single transducer is scanned by means of a driven eccentric cam and a cam follower. A sin/cos potentiometer generates a signal related to the angular position of the transducer connected to a delay so that pulse counting can be arranged to coincide with the passage of the transducer across the target.

Abstract: A radio communications system for aircraft, particularly useful at UHF frequencies and in aircraft travelling at high speed and low level where rapid phase and amplitude fluctuations degrade intelligible speech transmission. The system comprises a transmitter in a first aircraft, the transmitter including an upshift frequency translator for transferring the frequency band of an input signal from a microphone to a higher band, and further including an amplitude modulator for modulating the frequency translated signals; and a receiver in a second aircraft arranged to receive and demodulate the transmitted signals, the receiver including a high pass filter for removing noise from the demodulated signal, and a downshift frequency translator for transferring the frequency band of the filter output to a lower band.