Abstract: A plurality of unidirectional sheets (30a, 30b, 30c) are superposed in different directions and they are bonded together. At least one of the unidirectional sheets is made by spreading a tow so as to obtain uniform thickness, width not less than 5 cm, and a weight of no more than 300 g/m2, cohesion being imparted to the sheet so as to enable it to be handled prior to being superposed with other sheets. Advantageously, the unidirectional sheets are made of carbon fibers and are obtained by spreading out large tows.

Abstract: The metal static gasket forms an annular body about an axis ZZ′. The profile of the gasket in axial half-section presents an elongated S-shape and comprises a lateral first portion defining the inner peripheral surface of the gasket, a lateral second portion defining the outer peripheral surface of the gasket, said lateral first and second portions being offset from each other along the direction of the axis of the gasket. The gasket also presents a curved third portion of undulating shape having a substantially rectilinear first contact region at one of its ends, and a curved fourth portion of undulating shape having a substantially rectilinear second contact region at one of its end extending perpendicularly to the axis of the gasket in such a manner that the gasket provides sealing between two flanges solely by means of the axial pressure exerted by the flanges.

Abstract: The thrust device comprises a valve body (20) having a chamber (24) surrounding part of the needle, at least one gas admission opening (27) opening out into the chamber, and a gas outlet opening (25) opening out into the chamber and defined by a wall portion which co-operates with a nose portion (14) of a moving needle (10) to define an outlet section for gas leaving the chamber. Actuator means (40, 41, 43) control the position of the needle in the valve body by acting on a rear end portion of the needle. The nose (14) of the moving needle (10) has an aerodynamic concave profile (15) and the wall portion (29) which defines the outlet (25) from the chamber is shaped in such a manner as to be capable of directing the exiting gases essentially against the concave side of the nose of the needle, which needle acts as the main member for taking up thrust.

Abstract: A regenerative circuit structure is built up by implementing the following steps in particular: an intermediate layer is made on a support core representing the inner profile of the structure; a series of channels regularly distributed around the core is made with the channels opening to face the intermediate layer, each of the channels being provided with a soluble insert; the support core is preheated and the body of the structure is made by thermal spraying under a vacuum; channels are machined in the body from the outside, and said channels are filled by means of soluble inserts; a closure layer is formed to close the channels in the body, and an outer envelope is formed by thermal spraying under a vacuum, after preheating; and all of the soluble inserts and the intermediate layer are eliminated.

Abstract: The piece made of composite material comprises a plate and a plurality of stiffeners integrally formed with the plate. A metal wall is fixed to the edges of the stiffeners and is provided with passages for circulating the fluid. The plate exposed to the heat flux radiates towards the metal wall through the gaps between the stiffeners, and it also performs the structural function. The invention can be used with structures that are exposed to very high heat flux: the walls of jet combustion chambers, the walls of space plane vehicles, the walls of nuclear fusion reactors.

Abstract: A diverging ring is displaceable between a retracted position in which it surrounds a first portion of a diverging part and a deployed position in which it is connected to a downstream end of the first portion. A deployment mechanism causes the diverging ring to move from its retracted position to its deployed position under drive from an actuator. A temporary structure, or “insert”, is placed inside the diverging ring so as to transform the diverging section thereof into a non-diverging section, at least over the major portion of the length of the diverging ring, the insert being eliminatable on or after the diverging ring coming into its deployed position.

Abstract: The invention concerns (1) thermochemically treating by pack-cementation a carbon-containing material, which may have an open porosity, to generate a refractory carbide coating on its surface and, if the material is porous, within the material; and (2) the use of specific alloys as a pack for thermochemically treating carbon-containing materials, optionally with an open porosity, in a halogenated atmosphere. Pack-cementation is carried out under reduced pressure using an element E (to be transported and to be reacted with the carbon in the material to generate the expected carbide) alloyed to an element M, and using a halide (chloride or fluoride, preferably a fluoride) of the same element M, of low volatility, present in the solid form.

Abstract: The present invention provides a method of densifying porous structures by chemical vapor infiltration. In characteristic manner, said densification method is implemented using toluene as a precursor for carbon. Said toluene is generally used mixed with at least one carrier gas.

Abstract: The rack is made essentially out of thermostructural composite material and comprises a baseplate (12), a partition (14) extending above the baseplate, and a plurality of support arms (20) fixed to the partition and extending substantially horizontally therefrom to their own free ends, so that parts to be treated (A) can be supported in cantilevered-out positions on said arms.

Abstract: A steerable nozzle for a reaction engine comprises a fixed portion (1) for fixing to the engine, a moving portion (2) hinged to the fixed portion, control means (3) for controlling the moving portion, and one or more resilient assemblies (4) disposed between the fixed portion and the moving portion. The nozzle is characterized in that each resilient assembly comprises at least one fixed resilient stud (40) having a first end secured to the fixed portion and a second end, opposite from the first end, secured to a rigid piece (42); and at least one moving resilient stud (41) having a first end secured to the moving portion and a second end, opposite from the first end, secured to said rigid piece (42). In addition, each moving resilient stud (41) is offset relative to each fixed resilient stud (40) in a circumferential direction of the nozzle.

Abstract: A steerable nozzle for a reaction engine comprises a fixed portion (1) for connection to the engine, a plurality of steerable flaps (21) mounted on one end (11) of the fixed portion, and flap steering means (3, 4, 22, 31). The nozzle is characterized in that the flap steering means comprise a resilient ring (3) having a first circumference secured to said end (11) of the fixed portion and a second circumference connected to the flaps (21), and control means (4) for moving the second circumference of the resilient ring.

Abstract: An axisymmetric, converging-diverging and swiveling exhaust nozzle includes converging flaps (3) driven by an axially displaceable drive ring (7). The diverging flaps (15) are connected by linkrods (20) to a pivoting ring (21). The pivoting ring (21) is mounted in swiveling manner on a spherical segment (30) fixedly joined to the structure (13). In an embodiment variation, the spherical segment (30) is mounted by a sliding connection on the stationary structure. A rotation-blocking system (33) precludes the rotation of the spherical segment (30) about the axis X of the turbojet engine.

Abstract: The loader device is made of a thermostructural composite material and comprises a base (20), a loading pole (30) secured to the base and extending at least over the full height of the loader device, and a plurality of loading trays (40) each provided with a central passage through which the loading pole can pass. Each loading tray carries a plurality of spacers (50) enabling the trays to be mounted in succession at predetermined intervals, each tray carrying the same number of spacers which are in alignment so that after the trays have been assembled the spacers make up load-carrying columns extending over the height of the loader device, and at least one of the spacers carried by each tray has a disposition and/or a size that differs from the other spacers carried by the same tray so as to enable the trays to be indexed during assembly. Each tray (40) has means (45) for positioning parts at predetermined locations.

Abstract: In order to compensate non-linearity in the zero drift of the bridge at very low temperatures, a strain gauge in at least one of the arms of the bridge is in series with a resistor, e.g., a connection lead, of resistance that is much less than that of the strain gauge, and a compensation circuit is connected in parallel with the resistor. The compensation circuit includes a resistive element, e.g., a platinum probe, whose resistance varies as a function of temperature in such a manner as to influence, in the very low temperature range, the resistance of the parallel circuit of which it forms a part, and to do so in a manner that is sensitive to temperature and that increases with decreasing temperature.

Abstract: The material comprises fiber reinforcement made of fibers that are essentially constituted by silicon carbide, and an interphase layer between the fibers of the reinforcement and the matrix. The reinforcing fibers are long fibers containing less than 5% atomic residual oxygen and they have a modulus greater than 250 GPa, and the interphase layer is strongly bonded to the fibers and to the matrix such that the shear breaking strengths within the interphase layer and at the fiber-interphase bonds and at the interphase-matrix bonds are greater than the shear breaking strengths encountered within the matrix.

Abstract: The closed electron drift plasma thruster uses a magnetic circuit to create a magnetic field in a main annular channel for ionization and acceleration, said magnetic circuit comprises: an essentially radial first outer pole piece; a conical second outer pole piece; an essentially radial first inner pole piece; a conical second inner pole piece; a plurality of outer magnetic cores surrounded by outer coils to interconnect the first and second outer pole pieces; an axial magnetic core surrounded by a first inner coil and connected to the first inner pole piece; and a second inner coil placed upstream from the outer coils. The thruster also comprises a plurality of radial arms included in the magnetic circuit, and a structural base which is separate from the magnetic circuit and which serves, amongst other things, to cool the coils.

Abstract: The thruster comprises, on a common plate, a plurality of main annular ionization and acceleration channels having axes that are not parallel and that converge in the outlet direction of the channels. A magnetic circuit sets up a magnetic field in the annular channels. The thruster also has a hollow cathode, a device for regulating the ionizable gas feed rate to each annular channel, and a device for controlling the ion discharge acceleration current in the channels. The direction of the thrust vector of the thruster can be controlled without significantly increasing the mass of the thruster.

Abstract: An axially symmetric turbojet-engine exhaust nozzle which is directable as a unit. The exhaust nozzle is situated downstream of an exhaust duct (1) fitted with a spherical wall (5). A single control ring (12) driven by linear actuators (30) allows regulation of the nozzle cross section and direction. Converging flaps (7) are guided on an upstream side by the spherical wall (5) and are supported at a downstream side by a control lever (13) which hinges on the control ring (12) and rests upstream on an external surface (16) of the spherical wall (5). Diverging flaps (10) hinge on the converging flaps (7) to form an inner ring of hot flaps. The diverging flaps (10) are situated downstream in an extension of the converging flaps (7) and further hinge on an outer ring of cold flaps (11), which in turn hinge on the control ring (12).

Abstract: The present invention relates to: a novel process for the preparation of mesophasic polyborazylene. Said process is of particular value in that it affords a quality product from an appropriate polyborazylene, rapidly (virtually instantaneously), reproducibly and with a good yield. Furthermore, said process is easy to carry out. Said process comprises the preparation of polyborazylene by the polycondensation of borazine in a closed reactor and the addition, to said polyborazylene obtained by polycondensation, of a solvent selected from aromatic solvents, borazine solvents and mixtures thereof, mesophasic polyborazylene which is novel in that it is in the presence of a particular solvent and/or by virtue of its quality, the use of said polyborazylene of the invention, and/or prepared according to the invention, as a boron nitride precursor.

Abstract: The invention concerns an acoustic igniter for igniting a mixture of rocket fuels in a liquid propellant rocket engine combustion chamber comprising a cylindrical precombustion chamber (101) including a cylindrical wall (111) and first and second end walls (112, 113), a rocket fuel injection nozzle (103) emerging into the precombustion chamber (101) through the first end wall (112) via an orifice of diameter dn, a rocket fuel injector (104) arranged inside said nozzle (103) along the axis thereof, at least an outlet orifice (102) of minimum diameter df provided in the cylindrical wall (111), an acoustic resonator (105) defining a cavity opening into the precombustion chamber (101) opposite the nozzle (103), through the second end wall (113), via an orifice (151) of diameter dr. The acoustic resonator (105) is enclosed by a housing (106) which defines around the acoustic resonator (105) a closed auxiliary chamber (160) which communicates only with the precombustion chamber (101) by at least one conduit (107).