Patent Application
20060017197
The present invention relates to missiles and, more particularly, to valves that are used in the guidance of missiles.
Different types of missiles have been produced in response to varying defense needs. Some missiles are designed for tactical uses, while others are designed for strategic uses. Missiles typically have rocket motors that use hot propellant gases to thrust the missile forward. For missiles with guidance capabilities, valves may be employed that open or close to thereby redirect propellant gases to steer the missile in a desired direction.
Historically, missiles using thrust control valves have employed relatively simple geometric designs. The exhaust valves associated with these missile-types include component liners that define relatively simple flow paths (i.e., cylindrical, tubular, conical). Traditionally, component liners have been constructed of phenolic or rubber, which each can serve as an insulator to other exhaust valve components as well as an ablative that burns off when exposed to the propellant gases. Phenolic component liners may be made by compression-molding the phenolic around a solid insert shaped like the flow path. Alternatively, the component liner shape may be machined into a solid piece of phenolic.
Recently, the desire for smaller missiles having greater agility and the ability for longer flight missions has increased. As a result, missile designs have evolved to incorporate components having complex shapes that provide the desired precision guidance capabilities within these space constraints. These components may include flow paths having an L-shaped bend, an S-shape, or any one of a number of other complex shapes.
Although the aforementioned conventional methods have been adequate for the production of component liners having simple flow paths, they have not been as useful in the manufacture of component liners having complex flow paths. For example, in cases where the component is manufactured by a compression-molding process, the solid insert that is used may not be removable without inflicting damage to the component. Specifically, the solid insert may become trapped in the complex flow path. In the case where a machining process is employed, machining these complex flow paths into a solid piece of phenolic may be relatively difficult and time-consuming. Consequently, the costs of manufacturing these components may increase.
Thus, there is a need for a method of manufacturing that is useful for constructing missile components that have complex flow paths without damaging the component. It is also desirable to have a cost-efficient method for manufacturing missile components that may be implemented for mass production. The present invention addresses one or more of these needs.
Methods are provided for fabricating a missile component. In one embodiment, and by way of example only, the method includes the step of covering at least a portion of a core insert with a composite material. The method also includes compression molding the composite material on to the core insert to form the component and destructively removing the core insert while the core insert is at least partially disposed within the component.
In another exemplary embodiment, a method for a missile component having a flow path is provided. The method includes covering at least a portion of a core insert having a shape substantially similar to the flow path with a phenolic composite, compression molding the phenolic composite on to the core insert to form the component and the flow path, and destructively removing the core insert while the core insert is at least partially disposed within the flow path.
Other independent features and advantages of the preferred method will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention. For illustration purposes only, the invention is described herein as being used to manufacture a thrust assembly component that may be employed on a missile, however, it will be understood that the method may be used to manufacture any component that may be exposed to extreme high temperatures, such as for tactical, strategic, or long range missiles, any type of thrust-propelled craft, such as spacecraft and torpedoes, or other engine components that are exposed to extreme high temperatures.
The blast tube 104 is generally cylindrical in shape and includes a channel 114 therethrough that is configured to receive propellant gases from a non-illustrated motor, such as, for example, a solid rocket motor. The motor may include a fuel source that, when ignited, produces propellant gases and directs the gases into the blast tube 104. In the depicted embodiment, a portion of the propellant gases are directed through the blast tube 104 to the nozzle 106. As will be discussed more fully below, the remaining portion of the propellant gases are directed into the thrust assembly 108.
The nozzle 106 is coupled to the blast tube 104. In the depicted embodiment, the nozzle 106 is generally funnel-shaped and includes an inlet throat 118 in fluid communication with the blast tube 104 and an outlet 120 through which the propellant gases that enter the nozzle 106 may escape. When the propellant gases escape through the outlet 120, thrust is generated that propels the missile.
As was noted above, another portion of the propellant gases produced in the motor 102 is directed to the thrust assembly 108. The thrust assembly 108 includes at least a main inlet duct 122 and a valve nozzle 124. Both the main inlet duct 122 and valve nozzle 124 have a liner 126 which defines a flow passage 128. The flow passage 128 is shaped to divert a portion of the propellant gases from one direction to at least another. The flow passage 128 shape may also be configured to provide fine control of the pitch, yaw, roll, and thrust of an in—flight missile. In smaller missile configurations, the flow passage 128 may include any one of numerous shapes having any number of twists, turns, and bends. For instance, the flow passage 128 may be S-shaped, coil-shaped, or may include the two L-shaped bends and convergence/divergence, as shown in
The overall process 200 is illustrated in
Before discussing the process steps in more detail, it will be appreciated that, the core insert 300 shown in
Returning now to a discussion of the process steps, as was noted above, the composite material is initially compression molded around the core insert 300 (210). Any conventional method for compression-molding may be employed. In one exemplary embodiment, the core insert 300 is placed into a container and substantially covered with the composite material. Examples of composite materials include, but are not limited to glass or carbon reinforced phenolic prepreg, or any other material that may be compression-molded into a phenolic component. The container and its contents are then heated to between about 325 and 350 degrees F. The heat consolidates and crosslinks the composite material to form an infusible thermoset polymer. Next, pressure is applied to the composite material, ranging from between about 2,000 to 6,000 psi, which causes the composite material to deform around the core insert 300. Consequently, a compression molded, cured, phenolic component is formed.
For reasons that will become more clearly understood below, it is preferable to form at least one opening in the phenolic component that extends from the outer periphery of the component to the core insert 300. Preferably, the opening is proximate the vicinity of the first end 302 or second end 304 of the core insert 300 and may be formed during the compression molding step (210). In one exemplary embodiment, the core insert 300 is placed in contact with the bottom of a container. As a result, the phenolic material is unable to flow between the core insert 300 and container, thus forming an opening in the phenolic component. In another exemplary embodiment, an opening is machined into the phenolic component after the component has been compression molded.
Turning back to
In one exemplary embodiment, the core insert 300 comprises a material that has a melting temperature that is higher than the processing temperature of the cured phenolic component. Heat sufficient to melt the core insert 300 is applied to the core insert 300, causing the insert 300 to liquefy and flow out of the component. In one embodiment, the core insert 300 is selectively heated using eletrical induction coils, thus melting the core insert 300 without subjecting the entire component to elevated temperatures. In another embodiment, the cured phenolic component and core insert 300 are placed into a batch furnace. The furnace is heated above the melting temperature of the insert 400 but below the thermal degradation temperature limit of the cured phenolic component, thereby causing the insert 400 to melt, but the component shape to remain intact. Examples of suitable materials having a melting point lower than the melting point of the phenolic component include, but are not limited to indium-lead solder.
In another exemplary embodiment, the core insert 300 comprises material capable of withstanding the temperatures and pressures of a compression molding process, but having less physical strength than the cured phenolic component. In one example, the material is susceptible to damage upon the application of sonic energy. Thus, when sufficient sonic energy is applied to the core insert 300, the molecular structure of the core insert 300 breaks down. As a result, the core insert 300 breaks apart, shatters into a plurality of pieces, or may pulverize into a powder. Suitable materials include clay, green ceramic, or sand.
In another example, the core insert 300 is constructed of material capable of being sand- or bead-blasted. These materials include but are not limited to, graphite, green ceramics, and sand with binder additives. In yet another example, the material is capable of breaking down upon the application of highly pressurized water. Materials having such properties include plaster or sand with binders.
In yet another exemplary embodiment, the core insert 300 is exposed to a chemical that reacts with and dissolves the insert 400 material. The phenolic component remains in tact while the core insert 300 erodes. Examples of suitable core insert 300 materials and chemicals that may erode the core insert 300 include but are not limited to acid or alkaline. In another example, the core insert 300 is constructed of a composite that includes sand, which dissolves when wetted.
The core insert 300 material is physically removed from the phenolic component. As noted above, the phenolic component preferably includes at least an opening that extends between its inner and outer peripheral surfaces. After the core insert 300 is liquefied, pulverized, dissolved, shattered into a plurality of pieces, or otherwise destroyed, the opening provides an outlet through which the insert 300 material exits. The insert 300 material may be shaken or gravitationally directed out of the opening.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
