Abstract:
An explusion system in which an inner tank is nested within a second and  er tank to provide a very compact and space saving arrangement for an expulsion system for a rocket with the first and inner tank as well as the second and outer tank being reinforced with composite material to provide a space saving and relatively light expulsion system for a rocket.

Description:
DEDICATORY CLAUSE 
     The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalties thereon. 
    
    
     BACKGROUND OF THE INVENTION 
     In the past, various packaging systems have been provided, however none of them provide as lightweight and economical packaging arrangement as needed. The weight of a system often determines a particular missile system to which the packaging arrangement can be used and further, when used with a liquid system as desired here, the expulsion of that liquid requires a source of pressure. 
     With the above needs in mind, it is an object of this invention to provide a compact, lightweight and relatively economical fuel expulsion arrangement. 
     Another object of this invention is to provide an expulsion system that produces structure that can withstand relatively high pressures without unwanted leakage. 
     Other objects and advantages of this invention will be obvious to those skilled in this art. 
     SUMMARY OF THE INVENTION 
     In accordance with this invention, a very economical fuel system is provided that includes a tank within a tank with a piston mounted in the larger tank and shaped to expel a liquid fuel and still maintain a good seal between the pressurizing fluid and the liquid fuel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of an expulsion system in accordance with this invention, and 
     FIG. 2 is a sectional view of an alternate inner bottle that can be used in accordance with this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1 of the drawing, expulsion system 10 in accordance with this invention includes an inner tank 12, an outer tank 14 and an inner piston 16. Inner tank 12 includes members 18 and 20 that are telescoped together and sealed where they telescope such as by an O-ring seal 22 to define a chamber 24 therein. End members 18 and 20 are made of a metal such as aluminum. On the outer surfaces of members 18 and 20, alternate helical and hoop layers of composite material such as fiberglass, graphite, Kevlar and etc., is used in the helical and hoop layers to provide structural support to enable the tank to withstand pressures therein of 5,000 pounds with a burst strength of the tank of about 7,500 pounds. Helical layers 26 run from end to end of the tank structure and hoop layers 28 are at a cylinderical intermediate portion of the tank. The helical and hoop layers are each impregnated with an epoxy as they are added and the layers are added alternately with first a helical layer and then a hoop layer with this being altered until the required number of helical and hoop layers are built up. The tank after being provided with the required number of helical and hoop layers is cured to form a finished structure. End member 20 is threaded at 30 and a center tube member 32 has one end threaded into threads 30 and a seal 34 is provided for sealing between center tube 32 and member 20. End member 18 has an opening 36 therethrough and a manifold type structure 38 is sealably mounted about one end of center tube 32 and in opening 36. Manifold 38 is secured in place by securing means 40 on center member 32. Manifold structure 38 has openings 42 that communicate from chamber 24 to an on-off valve 44 and pressure regulator 46 and from pressure regulator 46 to chamber 48 that communicates with center passage 50 of center tube 32. Outer tank 14 includes end members 52 and 54 that telescope into cylindrical structure 56 and are sealed relative to cylinderical structure 56 by O-ring seals 58 and 60. Each of members 52, 54 and 56 are preferrably made of metal such as aluminum. The internal surface 62 of cylinderical member 56 is preferrably impregnated with teflon to provide a relatively slick and a sealing surface that can be easily sealed relative to a piston such as piston 16 by the use of O-rings 64 and 66 that are mounted in grooves 68 and 70 of piston 16 with each O-ring having an anti-extrusion ring 72 and 74 as illustrated for keeping the O-rings from extruding into the clearance space between the outer surface of piston 16 and the inner surface of cylinder 56. Piston 16 has an inner surface 76 that is contoured to the outer surface of one end of inner tank 12 to provide a minimum volume of dead space between these two members. Piston 16 has outer surface 78 that is contoured to fit internal surface 80 of end member 54. Outer surface 78 and inner surface 80 are contoured such that these two surfaces nest together and prevent any appreciable amount of fuel from being left in tank 14. As can be seen, a chamber 82 is formed on one side of piston 16 and a fuel chamber 84 is formed on the other side of piston 16. Piston 16 has a burst diaphragm arrangement 86 mounted at the center thereof and burst diaphragm 88 is designed to burst from the pressure within chamber 82 when fuel has been expended from chamber 84. Externally of end member 54 a molded syntactic foam 87 of glass microballoons and epoxy is mounted and this foam is of such a structure that forces transmitted from chamber 84 through end member 54 are transfered to outer helical layers 89 that are made of composite materials for supporting the outer tank sufficiently to withstand the pressures exerted thereon. Molded syntactic foam 87 not only acts as a support for transferring forces from end member 54 to outer helical support members 88 but this molded syntactic foam also provides heat insulation for insulating this end of the larger tank from a rocket motor (not shown) that produces heat and such heat being produced would not be desirable to be transmitted or radiated to the fuel in chamber 84. Helical layers 89 are wound from one end of the tank structure to the other and are built-up in layers and hoop layers 90 are also provided about the cylindrical intermediate portion of the tank. These helical and hoop layers can be added as alternate layers of helix and hoop layers. The composite material used in these layers can be fiberglass, graphite, Kevlar, etc., but preferrably is Kevlar. Other conventional composite materials could be used provided the materials have sufficient strength for supporting the tank structure. The composite material is bonded together with an epoxy in conventional manner. A flange 92 for securing the outer tank to a rocket motor or support is wound and machined in a conventional manner at one end of the tank as illustrated. End member 54 has an opening 94 therein that is provided for communicating fuel from chamber 84 to a rocket motor as desired. End member 52 is secured to end member 18 of tank 12 by bolts 51 and O-ring seal 53 is mounted between mating surfaces on members 18 and 52 to seal these members. 
     Another inner tank structure is illustrated in FIG. 2 that can be substituted for the tank structure illustrated at 12 in FIG. 1 and this tank 12 includes end structures 100, 102 that are made of aluminum. An inner liner 104 of isoprene rubber is fiber filled with silicon glass and bonded with conventional adhesive for bonding rubber to metal at surfaces 106 and 108 of end members 100 and 102. Helical layers 110 and hoop layers 112 at the cylindrical portion of the tank are provided and these layers are alternated first with a helical layer and then a hoop layer until sufficient strength is provided for the tank. The helical layers and hoop layers are made of conventional composite materials such as fiberglass, graphite, Kevlar, or other conventional composite materials. These composite materials are epoxy impregnated and allowed to cure after they have been applied. An outer epoxy sealing layer 114 is applied to the outer surface of the overall structure to ensure that an impervious tank structure is provided by sealing from end members 100 and 102 and over the complete surface of the helical and hoop structures. This tank is designed to have a burst pressure of 7,500 psi and is designed to continuously operate at pressure of 5,000 psi. Sealing layer 114 is made of any conventional epoxy sealant type material for sealing structures of this type. In operation, with inner tank 12 filled with a gas such as nitrogen and with chamber 84 filled with the desired fuel such as a monopropellant of hydrazine, on-off valve 44 is opened and regulator 46 regulates the pressure from say 5,000 psi to 900 psi and the inert gas is delivered through passage 50 to chamber 82 for moving piston 16 against the fuel in chamber 84 to expel the fuel through opening 94 to the motor which receives the fuel. As fuel from chamber 84 is expended, outer surface 78 nest into surface 80 of end member 54 and almost all the fuel from chamber 84 is expelled. When this fuel has been expended, the pressure in chamber 82 and across diaphragm 88 creates a differential pressure across diaphragm 88 such that diaphragm 88 is ruptured and the gas remaining in tank 12 and in chamber 82 serves to expend substantially all of the fuel and allow the structure to be safely recovered for examination without subjecting the test engineer to unnecessary risk or injury in examination of the expulsion system. 
     It will be appreciated that the expulsion system in accordance with this invention has the advantage of being much lighter in weight than conventional metal tankage systems of equal pressure capacity due to the higher specific strength of composite materials. In addition, a packaging advantage exists due to higher volume efficiency which results from nesting the piston over the enternal high pressure bottle. It will also be appreciated that the piston is shaped to rest against the end member and nest therein to minimize space required and at the same time to ensure that the fuel is all expelled.