Abstract:
A launch assist system for supplementing the launch acceleration forces of a projectile, rocket or missile. An airtight chamber covered by a flexible elastic membrane supports a platform in the center of the membrane; the platform is electromagnetically coupled to a cocking mechanism that withdraws the platform into the chamber. Air within the chamber is removed and compressed to be stored in a holding tank as the platform is lowered into the chamber and as the flexible elastic membrane extends into the chamber. The electromagnetic coupling may be triggered to release the platform to permit the stored energy in the extended flexible elastic membrane, and in supplemental force members, to apply acceleration forces to a launch vehicle; the compressed air stored in the tank is simultaneously released to fill the chamber as the flexible elastic membrane is withdrawn.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the launching of a projectile, rocket or missile, and more particularly to a system to assist in such launch to lessen the necessary fuel load during the initial phases of the launch. 
     BACKGROUND OF THE INVENTION 
     The launching of projectiles, rockets or missiles usually entails the ignition or firing of a propellant creating a thrust to raise the launch vehicle as it overcomes the forces of gravity. This initial phase requires that the vehicle move from rest and is accelerated to a critical velocity to permit the effective operation of internal controls to stabilize the vehicle as it continues to accelerate. The fuel expended during this initial acceleration requires that the acceleration forces exceed the weight of the vehicle including the onboard fuel; a reduction in weight of the vehicle lessens the required acceleration force and thus the fuel required to create the force. However, fuel calculations are predicated on the total weight of the vehicle including all unused fuel onboard. 
     Therefore, a reduction in the fuel load will reduce the requirement for onboard fuel since the total weight of the vehicle before launch has been lowered. If a supplemental acceleration system could be employed to impart acceleration forces to the vehicle, during the initial phases of its launch, the onboard fuel requirements would be lowered and the overall fuel requirements for the launch would be reduced. 
     OBJECTS OF THE INVENTION 
     It is therefore an object of the present invention to provide a system for assisting the initial phases of the launch of a launch vehicle such as a projectile, rocket or missile. 
     It is another object of the present invention to provide a system to impart supplemental acceleration forces to a vehicle during launch. 
     It is still another object of the present invention to provide a system for supplementing the required thrust or force to create acceleration to launch a vehicle without the use of onboard fuel. 
     It is still another object of the present invention to provide a launch assisting system to impart an acceleration force to a launch vehicle to supplement the acceleration forces being created by the thrust of the onboard propulsion system. 
     These and other objects of the present invention will become apparent to those skilled in the art as the description thereof proceeds. 
     SUMMARY OF THE INVENTION 
     Briefly, in accordance with one embodiment of the present invention, an airtight chamber is provided having a flexible elastic membrane extending across the open top thereof with a supporting platform positioned at the top center of the chamber. A cocking mechanism is secured to the platform for withdrawing the platform into the chamber thereby stretching the flexible elastic membrane. As the platform is being withdrawn into the airtight chamber, a compressor withdraws air from the chamber and stores the compressed air in a holding tank. Thus, as the cocking mechanism withdraws the platform, the flexible elastic membrane stretches and the air in the chamber is removed and stored in a compressed form in a holding tank. A launch vehicle mounted on the platform is thus lowered into the chamber as the platform is withdrawn. Supplemental force members such as steel cables may also be secured to the platform above the flexible elastic membrane and be lowered with the platform against tension forces applied to the supplemental force members. 
     At a predetermined time and position within the chamber, the electromagnetic coupling holding the platform in its depressed position within the chamber is de-energized thus releasing the platform and permitting the force of the flexible elastic membrane, and forces supplied by supplemental force members, to apply accelerating forces to the launch vehicle mounted on the platform. Simultaneously, the compressed air previously stored in a holding tank is released into the chamber to provide a positive pressure in the chamber; the positive pressure creates an upward force on the flexible membrane and the platform mounted thereon. Thus, the expanding air contributes ti the force applied the launch vehicle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may more readily be described by reference to the accompanying drawings in which: 
     FIG. 1 is an illustration, partly schematic and partly in section, of a launch assist system constructed in accordance with the teachings of the present invention. 
     FIG. 2 is an enlarged view, partly in section, of the details of the launch platform. 
     FIG. 3 is a schematic illustration of a flexible elastic membrane take up system that may be used in the system of the present invention. 
     FIG. 4 is a schematic illustration of a tensioning means for supplemental force members. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a launch structure  9  comprising a cylindrical rigid member forms a chamber  10 . A flexible elastic membrane  12  extends across the chamber and supports a launch platform  18  in the center thereof. 
     The flexible elastic membrane  12  may comprise any of numerous available flexible elastic materials having a suitable modulus of elasticity and that may be either monolithically molded or formed such as by weaving; the membrane must be capable of stretching and returning essentially to its original shape upon release of the forces creating the deformation of the material. It is intended that the flexible elastic membrane will be stretched and will be utilized upon release to impart an accelerating force to a launch vehicle. The flexible elastic membrane  12 , attached to platform  18 , extends over a plurality of guide drums  16  positioned about the upper circumference of the launch structure  9  and is anchored at  17 . Thus, as the flexible elastic membrane is stretched by the lowering of the platform  18  into the chamber  10 , the guide drums  16  permit the material of the membrane to flow over the drum while the anchors  17  secure the periphery of the membrane to the launch structure  9 . It will be appreciated that FIG. 1 is a two dimensional representation of a three dimensional system; that is, guide drums  16  will normally be positioned about the periphery of the opening of the launch structure  9  such that the lowering of the membrane into the chamber  10  can be accommodated without damaging or frictional contact of the membrane with the launch structure  9 . 
     A launch vehicle  15  is mounted on the launch platform  18 ; the platform is electromagnetically coupled to a cocking mechanism  22 . The cocking mechanism  22  (to be described) may be a screw-threaded shaft which can be lowered by a screw drive mechanism so that it extends through the bottom of launch structure  9  as it is lowered; alternatively, and in a preferred form, the cocking mechanism comprises a hydraulic ram that is driven by a drive  28  in the form of hydraulic pumps. With either embodiment, the cocking mechanism is lowered to thus lower the platform  18  into the chamber  10 . 
     Supplemental force members  11  may take the form of steel linked chains or steel cables extending radially from the platform  18 . These are strong enough (sufficient tensile strength) to withstand forces applied thereto by a supplemental energy source such as hydraulic rams, solenoids, or mechanical energy storage means such as springs. The supplemental energy sources are shown schematically as tensioning means  22 . The strengthening members may separately be secured to platform  18  over appropriate guide pulleys  23  and may either be formed as a supplemental force member positioned on top of the flexible elastic membrane as shown in FIG. 1 or may actually be formed as part of the membrane  12  (e.g. woven into a supporting fabric that is impregnated with an air impermeable material such as rubber). The flexible elastic membrane, with or without the supplemental force members, provides an air tight seal with the chamber  10 . As the cocking mechanism  22  lowers the platform  18  into the chamber  10 , compressor  26  removes the air from the chamber  10  and compresses the air to be stored in the holding tank  25 . 
     At launch time, the electromagnetic coupling holding the platform  18  in its lowered position (shown in dashed lines in FIG. 1) is deactivated to permit the stored energy in the stretched flexible elastic membrane, and the stored energy available in any supplemental force members, to impart an acceleration force to the launch vehicle  15 . Normally, this force will be applied at time coinciding with or near the time of ignition of the fuel onboard the typical launch vehicle. Simultaneously, as the forces applied to the platform tend to direct the platform upwardly, valve  27  is opened to permit the compressed air in holding tank  25  to enter the chamber  10 ; the air being replaced in chamber  10  creates a temporary high pressure below the membrane, thus assisting in the creation of additional upward forces to assist the launch. 
     Referring to FIG. 2, the launch platform  18  is shown in greater detail. The platform may comprise a support plate  31  and thrust deflector plate  30  for supporting the launch vehicle. The deflector plate is secured to the support plate  31  in any convenient manner and may be provided to assist in deflecting the escaping gases from the ignition of the fuel onboard the vehicle  15  during the initial phases of the launch. Supplemental force members  11  may be secured to the launch platform in any convenient mainer; in the embodiment shown in FIG. 2 these force members are secured to the support plate  31  through the thrust deflector  30 . The flexible elastic membrane  12  is secured to the launch platform in any convenient manner; in the embodiment chosen for illustration, the membrane  12  is compressed between the support plate  31  and a trigger plate  33 . The support plate  31  and trigger plate  33  are shown secured to each other through the utilization of fastening means  32  such as machine screws or the like. Any fastening technique may be used; however, it is important that the fastening, including the use of bolts or screws, does not adversely affect the integrity of the airtight chamber  10 . That is, the fastening means  32  are shown extending through the flexible elastic membrane  12 ; it is important that this penetration of the membrane be sealed to maintain the membrane as an airtight member. An electromagnet  20  having an electromagnetic coil  35  (shown schematically) therein is coupled to the platform  18  by applying a suitable electrical current to the coil  35 . The current supplied to the coil provides sufficient electromagnetic attraction to maintain contact with the trigger plate  33  until the electromagnetic field created by the current flowing in the coil  35  ceases. The control of the coil current is provided by a triggering system schematically shown in FIG. 2 at  36 . A power source such as a battery  37  applies a suitable potential to create an electric current for the coil  35  through a switch  39 . This switch is opened or closed in accordance with the commands provided by a switch controller  38 . It will be apparent to those skilled in the art that the schematic representation in FIG. 2 is provided for convenience and that actual utilization of the control circuit is likely to be substantially more complex and would be interfaced with the overall launch control system that effects ignition of the launch vehicle powering system. 
     The cocking mechanism  22  may be coupled to the electromagnet  20  in any convenient manner; if the cocking mechanism  22  is a screw-activated rotating member with external threads  40 , then a locking flange  43  would be appropriate to permit the cocking mechanism to rotate with respect to the electromagnet  20 . If, however, the cocking mechanism is a hydraulic ram, or if the cocking mechanism incorporates internal threads  41 , or any other means wherein the cocking mechanism  22  is not required to rotate, then the locking flange  43  may be replaced with any means of rigidly attaching the mechanism to the electromagnet  20  without provision for relative rotation. The launch platform  18  and the many components described in connection with FIG. 2 may take many forms; however, the use of an electromagnetic triggering mechanism appears to be the most convenient and the most readily controllable. 
     The flexible elastic membrane will “stretch” as the cocking mechanism withdraws the platform  18  into the chamber  10 . Depending on the physical size and weight of the launch vehicle, the vehicle may require extension into the chamber  10  to an extent greater than the elasticity of the membrane material will permit. That is, the material may be stretched beyond its ability to return to its original shape or perhaps beyond its tensile strength. To accommodate these variations in the size or total length of the flexible elastic membrane as it extends from the exterior of the chamber  10  (where it is attached to the launch structure  9 ) to the platform  18  at its lowest position during the lowering of the platform into the chamber, takeup drums are provided. Referring to FIG. 3, the flexible elastic membrane  12  is shown passing over a drum  50 . The drum  50  corresponds to the guide drum  16  shown in FIG.  1 . In FIG. 3, the amount of material used in the flexible elastic membrane  12  requires a means to accommodate the excess material when the membrane is in its relaxed or upper-most position; that is, with or without a launch vehicle, but in an uncocked position. Accordingly, drums  51 ,  52  and  53  are provided to permit the flexible elastic membrane to pass over the respective drums in a serpentine fashion. Each of the drums is spring loaded such as by springs  54 ,  55  and  56 , respectively, which are anchored as shown at  60 . The position shown in FIG. 3 for the membrane  12  is the position that the membrane would take in an uncocked position. When the membrane is stretched during the lowering of the platform into the chamber  10 , the membrane extends from the anchor  60  in a straight line as indicated by the broken line of FIG. 3 to the drum  50 . Each of the drums  51 ,  52  and  53  would thus be moved against the force of their respective springs to accommodate the straightened path of the flexible elastic membrane  12 . As the launch proceeds, and the membrane returns to its unstretched condition, the respective springs force the connected drums to return to the position shown in FIG. 3 to thus create a serpentine path for the flexible elastic membrane  12  to accommodate its longer unstretched form. 
     The supplemental force members  11  may be secured to the platform  18  as described in connection with FIGS. 1 and 2. These supplemental force members may be necessary in those instances where the forces supplied by the flexible elastic membrane are insufficient to materially affect the launch assist. These supplemental force members  11  may take the form of cables, steel link chains, composition cords or ropes and the like. These members may be positioned separately such as shown in FIG. 1 or may in some instances be positioned within the chamber  10  beneath the flexible elastic membrane  12 . It may also be possible to incorporate supplemental force members directly in the fabric of the flexible elastic membrane although accommodating the different moduli of elasticity of the membrane and supplemental force members may complicate such an embodiment. The force supplied by the supplemental force members  11  may be derived from any suitable tensioning means such as those shown schematically in FIG.  4 . Referring to FIG. 4, the tensioning means  49  may comprise a force cylinder  44  in the form of a hydraulic cylinder, an electromagnetic coil, or a mechanical spring. The force provided by hydraulic pressure, or the energization of an electromagnetic coil, or the release of the energy stored in a mechanical spring acts upon a piston  45  to drive the piston in the direction indicated by the arrow  46 . The supplemental force member  11  is anchored as shown at  60  to a stationary entity such as the launch structure  9 . The driving of the piston  45  in the direction of the arrow  46  will apply a tensile force to the member  11  and withdraw that portion for the supplemental force member  11   a  downwardly as shown in FIG.  4 . The force member  11  passes over a guide pulley  62  which in effect doubles the speed of withdrawal of the supplemental force member  11  in relation to the speed of the piston  45 . Other arrangements could be made to multiply the force applied by the piston  45  or adjust the speed of withdrawal of the supplemental force member to correspond to the desired speed of the platform  18  as it is accelerated upwardly from the chamber  10 . 
     The present invention has been described in terms of selected specific embodiments of the apparatus and method incorporating details to facilitate the understanding of the principles of construction and operation of the invention. Such reference herein to a specific embodiment and details thereof is not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modifications may be made in the embodiments chosen for illustration without departing from the spirit and scope of the invention.