Abstract: A device for measuring variations in the thrust of a plasma accelerator with closed electron drift comprising a main annular channel for ionization and acceleration, at least one hollow cathode disposed outside the main channel and downstream therefrom, an anode, ionizable gas feed means associated respectively with the hollow cathode and with the anode, and magnetic field creation means. The device comprises a plurality of magnetic flux sensors (101 to 104; 31 to 33) disposed around the acceleration channel (24), a plurality of amplifiers (111 to 114) whose inputs receive the respective signals delivered by the magnetic flux sensors (101 to 104; 31 to 33) and a summing circuit (115) whose inputs are connected to the outputs of said amplifiers (111 to 114).

Abstract: A method of manufacturing an enclosure containing hot gases cooled by transpiration comprises:forming a shaped rigid shell comprised of a microperforated sheet metal, hydraulic calibration sheath,welding spacers to an outside face of the hydraulic calibration sheath;welding an outer sealing envelope on an outside surface of the spacers and the partitions; andforming a porous wall by applying a deposit onto an inside face of the hydraulic calibration sheath.

Abstract: Distinct preforms are made for different portions of a composite material part that is to be fabricated, and they are assembled together in a non-densified state or in a state that is not completely densified by uniting respective contacting surfaces of the preforms (13, 15, 36) together by means of fibrils (17, 19) projecting perpendicularly from the surface of one of the preforms (13, 15) and in which the surface of another preform (36) is engaged. The assembled-together preforms are then co-densified. The fibrils are formed on the surface of a fiber preform by the ends of fibers thereof that have been displaced by the preform being needled. The method is particularly suitable for fabricating a sandwich panel of composite material comprising two rigid skins between which there is disposed a core constituted by partitions that are perpendicular to the skins.

Abstract: The downstream portion of the diverging part of the nozzle of the rocket engine is extended by an ejectable diffuser which, downstream from the zone where it is connected to the diverging part, presents a zone of smaller cross-section that acts during a first stage of flight in the presence of significant outside pressure to recompress the flow of hot gases and to prevent a flow separation from appearing along with the wall of the diverging part. The ejectable diffuser may have a streamlined throat which constitutes the zone of smaller cross-section.

Abstract: The thermal protection device is made up of a plurality of juxtaposed unit modules each comprising a fairing element provided with fixing tabs and thermal insulation integrated in the fairing element. The gap between neighboring fairing elements is limited to the minimum width necessary for accommodating thermal expansion thereof. The connection means which releasably connect the fixing tab to a primary structure to be protected comprise a ball fixed to the fixing tab in adjustable manner and capable of being locked in a corresponding socket of a retaining part fixed to the primary structure. The ball is locked in its socket by means of a bolt capable of being released by action exerted against a resilient return force.

Abstract: A fiber preform constituting the fiber reinforcement of the part to be made is itself made by shaping and consolidating a fiber fabric by a liquid process. An interphase layer between the fibers and the matrix is formed on the consolidated preform prior to densification thereof with the matrix, such that the operation of densifying the consolidated preform can be performed without requiring supporting tooling therefor.

Abstract: In a rocket engine nozzle with a selectively smaller outlet cross-section, the nozzle comprising a converging portion which receives the gases produced in a combustion chamber, a nozzle throat of small cross-section and a diverging part connected to the nozzle throat and terminating at its downstream portion in a gas jet outlet cross-section defining a high cross-section ratio, a releasable annular obstacle is connected to the downstream end of the diverging part so as to define at the outlet of the diverging part a zone of selectively smaller cross-section which ensures stability of the separation of the flow of hot gases relative to the wall of the diverging part during a first phase of flight.

Abstract: In a process according to the invention, before a carbon/fiber ceramic matrix is densified, the carbon fiber reinforcement material is subjected to a thermal treatment in a non-oxidizing environment at a temperature greater than 1300.degree. C. and less than 2200.degree. C., to act on the bonding between the fibers and the matrix. If a preform of the carbon fiber reinforcement material is formed prior to densification by a matrix, then the thermal treatment may be performed on the preform, prior to densification by the matrix. If the matrix is densified by chemical vapor infiltration inside a furnace, then the thermal treatment may be performed inside the infiltration furnace prior to the densification. The thermal treatment achieves a significant improvement in the strength of the resulting composite material.

Abstract: The system (31 to 33, 34 to 38) for generating a magnetic field in the main channel of the plasma accelerator are adapted to produce, in the main channel (24) an essentially radial magnetic field at the downstream end (225) of the channel (24), its induction being maximum at this point. The magnetic field has a minimum induction in the transition area in the vicinity of the anode (25), the absolute induction value of the field increasing again upstream of the anode (25), in the region of the buffer chamber (23) in order to produce a magnetic mirror effect. The magnetic field lines include, between the anode (25) and the downstream end (225) of the channel (24), a concavity oriented downstream, causing focusing of ions, the maximum ionisation density area being located downstream of the anode (25).

Abstract: A process for the manufacture of a fibrous texture for producing a composite material article. The fibrous texture is formed of a yarn comprising discontinuous fibers which are made of a refractory material or a precursor thereof. The discontinuous fibers are disposed parallel to one another, without twist. A covering yarn made of a fugitive material is disposed over the discontinuous fibers to provide integrity to the yarn. The covering yarn is eliminated after formation of the fibrous texture.

Abstract: In a rocket engine nozzle comprising: a converging portion that receives the gases produced in a combustion chamber; a throat of small section; and a diverging portion connected to the nozzle throat; the diverging portion includes a set of downstream notches running longitudinally from its downstream end and uniformly distributed around the entire periphery of the diverging portion, the total width of all of the notches within any section representing about 1% to 6% of the periphery of the diverging portion. The notches serve to avoid having a jet separation line that is irregular and unstable, and they facilitate matching the diverging portion to ambient conditions that vary in flight.

Abstract: The sliding joint assembly for a first part and a second part having different expansion coefficients comprises a plurality of radially-acting spring blades connected firstly at first ends to the first part only in the vicinity of a contact interface, and secondly via second ends to the second part only in a zone that is axially remote from the contact interface, the contact interface constituting a sliding contact interface between the first and second parts while the second ends of the spring blades are connected to the second part by mechanical fasteners constituted by detachable screw-and-nut type assemblies provided with spring washers for damping forces exerted in the axial direction.

Abstract: The present invention provides an ion-optics system for a source of ions for discharge into gases, the system comprising a screen grid (1) and an accelerator grid (2) constituted by respective frames (3, 4) and respective systems of parallel wires (5, 6) fixed to the frames by means of springs (21), the frames of the grids being assembled to each other via insulators (7) to which they are fixed, the system being provided with a displacement device (9) for adjusting the wires in each of the grids, which device comprising rolls (11) disposed transversely relative to the wires in each grid and offering guide elements (12) in which the wires are placed, the rolls being installed on the frames of the grids with the facility of rotating about their own axes and of changing position in three dimensions together with the wires.

Abstract: The gas generator comprises an annular main porous piece, at least one calibration lining for defining a flow rate of a first liquid propellant component that is injected through the porous piece towards a combustion chamber that is delimited by one of the faces of the porous piece, and means for radially injecting a flow of a second propellant component into the immediate proximity of the face of the porous piece that delimits the combustion chamber in such a manner as to cause the first and second propellant components to be mixed in the immediate proximity of the face of the porous piece that delimits the combustion chamber.

Abstract: The centrifugal pump with an open-faced impeller comprises at least one open-faced impeller having blades placed inside a casing defining both a delivery pipe and a suction pipe facing the base of the blades situated in the vicinity of a central shaft for driving the impeller. An active axial balancing system for the rotary assembly is integrated in the impeller and comprises a balancing chamber interposed between the rear face of the body of the impeller and an outer rear portion of the casing, the impeller itself acting as the balancing turntable. A shroud-forming intermediate part is prevented from rotating relative to the casing and is interposed between an outer front portion of the casing and the impeller, a cavity is formed between the outer front portion of the casing and the intermediate part to receive a back pressure of predetermined value serving, in operation, to maintain small clearance without contact between the intermediate part that is prevented from rotating and the blades of the impeller.

Abstract: The present invention relates to a device for purging combustion residues from a thruster that comprises firstly a combustion chamber designed to receive a solid propellent and secondly a nozzle for evacuating propulsion gases and connected to the bottom of said chamber while leaving an annular space in which liquid residues of propellent combustion can accumulate. The device comprises at least one tube fixed on the converging part of the nozzle by fixing means, said tube including a first end dipped in the mass of liquid formed by said combustion residues and at a determined distance j from the bottom of the chamber, and a second end emerging level with the top end of the converging part and set back a little from the throat of the nozzle.

Abstract: A method of manufacturing a honeycomb structure of thermostructural composite material comprising a fiber reinforcing fabric densified by a matrix, the fibers of the reinforcing fabric being of a material selected from carbon and ceramics, as is the matrix, the method comprising the following steps:making a three-dimensional fiber fabric by means of superposed two-dimensional plies that are bonded together by means of fibers passing through the plies;making slit-shaped cuts in a staggered configuration through the plies, and through the entire thickness of the fabric;stretching the cut fabric in a direction that is not parallel to the cuts but that is parallel to the plies so as to form cells whose walls are constituted by the lips of the cuts; andwhile the cut texture is held in the stretched state, densifying it using the matrix-constituting material to obtain a rigid honeycomb structure of thermostructural material.

Abstract: The rocket engine is fitted with an injection device comprising a single injection plate having a central portion that defines the end of the burn zone of the combustion chamber and that contains first propellant injectors having a high mixing ratio adapted to the conditions under which hot gases are produced in the burn zone, and a peripheral portion in the form of a ring that defines the end of an annular cavity of a gas generator and that contain second propellant injectors having a low mixing ratio and adapted to the conditions under which hot gases are produced in the gas generator. The gas generator is thus integral with the combustion chamber and the annular cavity of the gas generator is separated from the burn zone of the combustion chamber by a cylindrical wall that extends axially perpendicularly to the injection plate and that is fixed thereto in sealed manner.

Abstract: A compact high power turbopump for feeding liquid propellant to a rocket engine comprises: a short, large diameter shaft that is capable of rotating; a single impeller providing a large pressure rise at a large flow rate, the impeller being mounted on the short shaft so as to constitute a single pump stage; a ball bearing for supporting the short shaft in a small section zone thereof situated in front of the impeller; a fluid bearing dimensioned so as to withstand a high speed of rotation N and having a large diameter D, the fluid bearing serving to support the short shaft in a large section zone situated behind the impeller; a turbine cantilevered out on the short shaft behind the fluid bearing; an inducer of the high pressure type disposed upstream from the ball bearing on the suction pipe; and metal casing elements for the pump and for the turbine that are of simplified shape.

Abstract: A process for the manufacture of a fibrous texture for producing a composite material article. The fibrous texture is formed of a yarn comprising discontinuous fibers which are made of a refractory material or a precursor thereof. The discontinuous fibers are disposed parallel to one another, without twist. A covering yarn made of a fugitive material is disposed over the discontinuous fibers to provide integrity to the yarn. The covering yarn is eliminated after formation of the fibrous texture.