Missile canister and method of fabrication

Abstract: A missile canister (110) for storing, transporting and launching missiles includes inner (114) and outer (112) skins and a compression resistant honeycomb type material (116) between the skins. An alternative embodiment on the missile canister has an epoxy syntactic foam material between the skins of the cells which are attached one to another by threaded fasteners (442) which cooperate with tapped holes (440) in the cell walls.

Description: The present invention relates to a missile canister for storing, transporting and launching missiles according to the precharacterizing clause of claim 1. In particular, such a canister is intended for use on naval vessels. Missile canisters of the prior art which have been used in conjunction with shipboard vertical launch systems to store, transport and launch missiles have generally enclosed only a single missile. These prior art canisters are typically constructed of steel and incorporate welded reinforcements and/or corrugations in order to achieve sufficient strength to provide adequate protection for the missiles during transport and storage and to withstand the stress of missile firings. Thus, these canisters of the prior art are heavy and occupy a volume much larger than that of the missile they enclose. The seize and weight of these canisters of the prior art thus limit the number of missiles which can be placed on a ship of given type and seize. US-A-3,754,497 discloses a missile canister having an outer skin comprising a plurality of cells having an axis parallel to the canister axis. The canister skin and the cell skins form an interstitial space which is filled with a compression resistant material such as expanded polyurethane. A rigid support frame in which guide tubes for the projectiles are mounted comprises a plurality of rigid plates transverse to the tubes and having openings in which the tubes are mounted. GB-A-2 188713 discloses a missile canister according to preamble of claim 1 having an inner layer which is clad with heavy gauge aluminum foil to prevent transfer of external water vapor into the inner side of the enclosure and also to provide electromagnetic shielding. Between the inner layer and the outer layer of this known canister a core member of honeycomb-type material is provided. From GB-A-1 372846 it is generally known to provide a syntactic foam element comprising a syntactic foam and a reinforcement material for the foam. The syntactic foam comprises microspheres embedded in a resin matrix, whereas the reinforcing material is a honeycomb material. The resin forming the matrix for the microspheres is an epoxy resin, polyester resin or another curable thermosetting resin. Finally, GB-A-1 153248 shows a flotation unit for underwater instrumentation in which a syntactic foam is used consisting of a mixture of hollow glass microspheres in an epoxy resin matrix. Due to the disclosed structure, a superior buoyancy of the assembly can be obtained. It is an object of the present invention to provide a light-weight missile canister which provides sufficient strength to protect one or more missiles contained therein during storage and transport and to provide protection for other missiles and other objects which are proximate to the canister during firing of a missile therein. This object is achieved according to the invention with a missile canister as characterized in claim 1. Further advantageous developments of the inventive missile canister are mentioned in claims 2 to 11. The canister includes a plurality of missile cells each of which having a cell wall generally surrounding a longitudinal cell axis and releasable fastening means, such as fastener strips which may be bolted to the cell walls, for releasably fastening the missile cells together to form a multiple cell canister. Each of the missile cells includes an outer missile cell skin formed of a suitable material, such as aluminum, and an inner missile cell skin, formed of a similar material, generally surrounding a common longitudinal axis. The interstitial space between the two skins contains a compression resistant material, such as aluminum honeycomb or epoxy syntactic foam. A missile canister comprising the present invention may be fabricated by providing an outer skin and an inner skin, positioning the inner skin within the outer skin, such that they bound an interstitial space, and injecting an epoxy syntactic foam into the interstitial space. These and other features, advantages and objectives of the present invention will be further understood upon consideration of the following detailed description together with the drawings in which: Fig. 1 is a cross sectional view of a missile canister comprising a first exemplary embodiment of the present invention. Fig. 2 is a cross sectional view of a missile canister comprising a further exemplary embodiment of the present invention. Fig. 3 is a cross sectional view of a single missile cell of a missile canister comprising another embodiment of the present invention. Exemplary missile canisters 210 of Fig. 1 comprises four missile cells 218. Wall 220 of each of missile cells 218 has an inner missile cell skin 214 and an outer missile cell skin 222 which sandwich a honeycomb core in interstitial space 216. Inner cell skin and outer skin are made of aluminum, but may be made of any material of suitable rigidity and elasticity, for example fiberglass composite. Compression resistant material of exemplary missile canister 310 is an epoxy polymer matrix material comprising glass microspheres in an epoxy polymer matrix. A suitable epoxy syntactic foam may be prepared by mixing, by weight, about 55% epoxy resin, for example Expon 815 as manufactured by Shell Chemical Company, 22% epoxy hardener, for example Jeffamine T403 as manufactured by Texaco Chemical Company, about 5% cure accelerator, for example Accelerator 399 as manufactured by Texaco Chemical Company, and about 17% glass microspheres, for example product B23/500 glass bubbles as manufactured by 3M Corporation. Corner fittings 224 join the plainer cell wall panels of exemplary missile canister 210 and include fin guides 226. Missile cells 218 are joined one to another by means of tie strip 230 and bolts 232 which pass through holes in edge portions of the tie strip and thread into threaded holes 234 in corner fittings 224. This allows any of missile cells 218 to be removed from missile canister 210 and refurbished or replaced by a similar missile cell should the cell become damaged, require refurbishment after a missile firing, or need to be replaced by a missile containing cell after a single missile has been fired from missile canister 220. Missile canister 410 of Fig. 2 comprises a further exemplary embodiment of the present invention in which interstitial space 416 between inner missile cell skin 414 and outer missile cell skin 422 is also filled with an aluminum honeycomb material. Missile cells 418 of missile of missile canister 410 are each fabricated from a sheet of aluminum honeycomb core material by first crushing the honeycomb material along lines at which the corners of the cells are to be formed and then bending the sheet to form the corners of a closed cell. Corner stringers 438 are then welded to crushed edges of the panel to form the closed cell. Missile cells 418 of canister 410 are releasably attached by nut and bolt sets 442 which cooperatively engage eyes 440 which are welded to outer missile skin 422. An individual cell 518 of a missile canister is shown in the sectional view of Fig. 3. Cell wall 520 of missile cell 518 comprises inner skin 514 and outer skin 522 separated by interstitial space 516 which is filled with an epoxy syntactic foam. Exemplary foam core missile cell according to Fig. 3 fabricated by first positioning inner cell skin in the desired location within outer skin defining interstitial space 516 in which end caps are then placed at each end of the structure to seal interstitial space 516 from the surrounding atmosphere. Air is withdrawn from interstitial space 516 through a port in one of the end caps by means of a vacuum pump to lower the pressure within the interstitial space to about 5 pounds per square inch below atmospheric pressure. With the longitudinal axis of the missile cell preferably in a near vertical position and the vacuum ported end cap in an elevated position, an epoxy syntactic foam mixed in accordance with the above proportions is then injected into the interstitial space 516 through a port in the lower end cap. Open honeycomb material, for example an aluminum honeycomb or fiberglass honeycomb material, may be used to assist in maintaining inner missile skin in position within outer canister skin and assure they remain in their desired position during the foam injection process. During the foam injection process, foam will flow into and fill the open interstitial space of the canister structure. Also, it may be advantageous to provide a limited number of foam injection ports in outer canister skin through which foam may be injected to facilitate the foaming process by eliminating the need for some portion of the foam material to flow over the entire length of the missile canister. Typically, inner cell skin may be formed of aluminum sheet 81,000 of an inch thick and interstitial space 516 may be of the order of one-half inch. Fittings for releasably attaching missile cells 518 one to another may be welded to outer missile skin 520 prior to placement of the epoxy foam in interstitial space 516 when outer skin 520 is fabricated of a metallic material. Should outer skin 522 be fabricated of a nonmetallic material, for example a composite fiberglass material, such fittings may be embedded in the fiberglass outer skin during its fabrication. The epoxy syntactic foam of the preferred embodiments will have a density of about 39 to 41 pounds per square foot. Those familiar with the art will recognize that wiring and tubing for servicing and controlling a missile within missile canisters constructed by an in place foaming process may be installed in the interstitial space 516 before the foam is placed thus embedding such wiring and service lines in the foam for their protection and to provide an unobstructed interior and exterior surface of the missile cells and missile canister. While exemplary missile canisters comprising embodiments of the present invention have been shown, it will be understood by those knowledgeable in the art that the invention is not limited to those embodiments. Modification may be made by those skilled in the art, particularly in light of the foregoing teachings, within the scope of the appended claims. For example, a fiberglass honeycomb material may be utilized to fill the interstitial space.

Claims: A missile canister for storing, transporting and launching a missile, comprising a plurality of missile cells, each cell having an outer missile cell skin (222, 422, 522) substantially surrounding a longitudinal missile cell axis; an inner missile cell skin (214, 414, 514) integrally formed and substantially surrounding said longitudinal missile cell axis such that an interstitial space (216, 416, 516) is defined between the skins (214, 414, 514; 222, 422, 522), and a compression resistant material within said interstitial space (216, 416, 516), characterized in that said compression resistant material includes an open honeycomb material and epoxy syntactic foam filling the interstitial spaces present in the honeycomb material as well as between the inner cell skin (214, 414, 514) and the outer cell skin (222, 422, 522), and that a releasable fastening means (230, 442) for releasably attaching one of the cells to another cell comprising a substantially longitudinal axis lying between a first and a second edge portion, first means for releasably connecting said first edge portion to the wall of a first cell and second means for releasably connecting said second edge portion to the wall of a second cell. A missile canister as in claim 1, in which the releasable fastening means comprise a tie strip (230) and bolts (232) which pass through holes in the edge portion of the tie strip and thread into threaded holes (234) in corner fittings (224) of adjacent cells. A missile canister as in claim 1, in which said releasable fastening means comprise nut and bolt sets (442) which cooperatively engage eyes (440) which are welded to the outer missile cells skins (422) of adjacent cells. A missile canister as in claim 1, in which said epoxy syntactic foam is formed by mixing about 55% epoxy resin, 22% epoxy hardener, 5% cure accelerator and 17% glass microspheres by weight. A missile canister as in claim 1, in which said foam has a density of approximately 40 pcf. A missile cell as in claim 2, in which said epoxy syntactic foam comprises glass microspheres within an epoxy polymer matrix. A missile cell as in claim 6, in which said epoxy syntactic foam is formed by mixing about 55% epoxy resin, 22% epoxy hardener, 5% cure accelerator and 17% glass microspheres by weight. A missile cell as in claim 6, in which said microspheres are of a diameter of approximately five microns. A missile cell as in claim 6, in which said foam has a density of approximately 40 pcf. A missile canister as in claim 1, in which said releasable fastening means for releasably attaching one of the cells to another cell comprises: a tie strip (230) having a substantially longitudinal axis lying generally between a first and a second edge portion; first means (232) for releasably connecting said first edge portion to the wall of a first cell; and second means (234) for releasably connecting said second edge portion to the wall of a second cell. A missile canister as in claim 10, in which said first and second releasable connecting means each include threaded fasteners adapted to cooperate with threaded holes formed in the first and second cell walls.

Inventors: BOVEE STAN P, BUSHAGOUR ABUBAKER M, VASKE JAMES G, BOVEE, STAN P., BUSHAGOUR, ABUBAKER M., VASKE, JAMES G.
Applicants: FMC CORP, FMC CORPORATION
Application year: 1992
Main classification: F41F3
IPC codes: F41F3