Patent Application
20070234893
The present invention relates to missilery in general, and, more particularly, to missile launchers.
A missile is propelled by fuel and a chemical-propulsion engine. A chemical-propulsion engine propels a missile by the reaction that results from the rearward discharge of gases that are liberated when the fuel is burned. For the purposes of this specification, a “missile” is defined as a projectile whose trajectory is not necessarily ballistic and can be altered during flight (as by a target-seeking radar device and control elements).
When a missile is launched, the discharge of the hot gases causes several problems. First, the hot gases heat the launch platform, which renders the launch platform more visible to enemy infrared sensors and, therefore, more vulnerable to attack. Second, the hot gases can obscure the ability of personnel in the area of the launch platform to see, which might impair their ability to perform routine tasks, such as detecting enemy threats. Third, the brightness of the flame exiting the engine can—especially at night—temporarily blind the launch-platform personnel. Fourth, the missile's fuel often includes an aluminized compound that is dispersed in the atmosphere surrounding the launch platform, which can impair the operation of radar systems near the launch platform. And fifth, as modern missiles become larger, their gases become hotter and more voluminous, and, therefore, cannot be adequately vented within the launching platform using current technology.
Electromagnetic missile launchers (EMMLs) have been developed to mitigate some of the damaging effects of a chemically-based missile launch, In the prior art, such as U.S. patent application Ser. No. 10/899,234, filed on 26 Jul. 2004, which is incorporated by reference herein, an EMML typically utilizes electromagnetic coils around a guide rail to propel an armature on which is mounted to a missile. Inefficiencies inherent to this propulsion method, however, dictate that the electromagnetic coils be larger, more numerous, and carry more electric current than desirable. The additional infrastructure adds to launcher cost and complexity. In addition, the power system used to control the flow of electric current in the electromagnetic coils must be made larger so as to manage the increased electric current as well as transients that develop through the course of a missile launch. There exists a need, therefore, for a missile launch system that avoids or mitigates some or all of these problems.
The present invention provides a technique for launching a missile that avoids some of the costs and disadvantages for doing so in the prior art. In particular, the illustrative embodiment of the present invention uses a pilot accelerator to accelerate an armature for throwing a missile from its rest position into motion toward a series of rail coils that sustain the acceleration of the armature.
In the illustrative embodiment, an electromagnetic coil arrangement includes a propulsion coil—the pilot accelerator—that is located behind the missile armature so as to direct its propulsive force on the armature along the launch axis. This provides a more efficient means of initiating the motion of the armature than is known in the prior art. The coupling efficiency of the electromagnetic force generated by the rail coils is improved by the use of the pilot accelerator, which results in an improvement in efficiency of the overall launcher system. This mitigates some of the problems associated with launching missiles in the prior art.
An embodiment of the present invention comprises: an outer coil that has a longitudinal axis; an armature that comprises an armature coil that is concentric with the outer coil, wherein the outer diameter of the armature coil is smaller than the inner diameter of the outer coil; and a pilot accelerator for imparting a first force to the armature, wherein the first force is directed along the longitudinal axis of the outer coil; wherein a second force on the armature is based on the mutual inductance of the outer coil and the armature coil; and wherein the first force accelerates the armature from a rest position toward the outer coil so as to increase the mutual inductance of the outer coil and the armature coil.
The following terms are defined for use in this Specification, including the appended claims:
Launcher 102 is a system that has the capability to house and expel one or more missiles upon command. The system expels each missile from an associated launch cell using an electromagnetic catapult and without the aid of the missile's chemical-propulsion engine. This is advantageous because it enables the missile to clear the launch platform before it ignites its engine, thereby avoiding some of the problems discussed in the Background section. Although in the illustrative embodiment electromagnetic launch system 100 comprises an electromagnetic launcher having a single launch cell, it will be clear to those skilled in the art, after reading this specification, how to make and use alternative embodiments of the present invention wherein launcher 102 comprises more than one launch cell.
Launch controller 104 provides the targeting and flight information to a missile prior to launch and the directive to launch to power system 108.
Weapons control system 106 provides targeting and flight information and firing authority to launch controller 104 prior to and during a launch sequence. It will be clear to those skilled in the art, after reading this disclosure, how to make and use weapons control system 106.
Power system 108 comprises circuitry that conditions and manages the storage and delivery of power to, and the recover of power from, launcher 102 in response to signals from launch controller 104. Power system 108 controls power generation, scavenging, storage, and delivery prior to, during, and after each launch. Power system 108 is described in detail in U.S. patent application Ser. No. 10/899,234, filed on 26 Jul. 2004, which is incorporated by reference herein.
Control cable 110 carries the targeting information from launch controller 104 to the missile and sled position information from sled-position sensor 322 (shown in
Signal line 112 connects launch controller 104 to power system 108 and carries the commands that direct power system 108 to initiate and control the launch of a missile.
Current cable 114 carries power from power system 108 to launcher 102. In some embodiments of the present invention that comprise multiple launch cells, current cable 114 is capable of carrying power to each launch cell independently from the other launch cells.
Missile canister 208 encloses missile 202, sled 204, guide rail 206, and rail coils 212-1 and 212-2 in a substantially air-tight environment.
Missile 202 comprises a chemical-propulsion engine and an explosive warhead.
Sled 204 comprises a rigid platform for holding a missile, sled coil 210, and bearings 214 for guiding sled 204 along guide rail 206. Sled coil 210 is an electrical conductor that has a helical shape and is immovable with respect to sled 204. Prior to launch, missile 202 is attached to sled 204 by actuatable missile restraint bolts (not shown for clarity) and sled 204 is attached to missile canister 208 by sled restraint bolt 214.
Rail coils 212-1 and rail coil 212-2 each comprise a helix of electrical conductor, wherein each helix has an inner diameter larger than the outer diameter of the sled coil, and wherein the electrical conductor is capable of carrying sufficiently high voltage/amperage to enable sufficient launch power.
During a missile launch, electric current is first directed to flow through sled coil 210 and rail coil 212-1 by a power management system. The current flow induces a force on sled 204 that is partially directed along launch axis 216. The magnitude of the electromagnetic force on sled 204 is a function of the currents in sled coil 210 and rail coil 212-1 and the gradient of their mutual inductance. The electromagnetic force increases until it is sufficient to break sled restraint bolt 216 and propel sled 204 (and attached missile 202) along launch axis 218 toward the muzzle end of launcher 200. The power management system sequences and controls current flow in sled coil 210, rail coil 212-1 and rail coil 212-2 during missile launch to continue the acceleration of sled 204 along launch axis 218 until sufficient velocity is obtained to throw missile 202. At a predetermined velocity, the missile restraint bolts are actuated (i.e., broken) and the power management system changes the current flow in sled coil 204 and rail coils 212-1 and 212-2 so as to decelerate sled 204 such that the missile disengages from the sled. After it disengages from sled 204, missile 202 exits the muzzle end of launcher 200 and achieves aerodynamic flight. Prior to the loss of aerodynamic flight, and after missile 202 achieves sufficient separation from launcher 200, the chemical-propulsion engine of the missile is ignited and missile 202 continues toward its target.
At the beginning of the launch sequence, the electromagnetic force on sled 204 is generated by the flow of electric current in the sled coil and rail coils. The magnitude of that force is a function of the mutual inductance of these coils. Rail coils 212-1 and 212-2 are “side-load” electromagnetic propulsion elements, as will be described below and with respect to
The mutual inductance between a coil and an armature is a function of the number of coil windings and the magnitude of the electric current flowing in the coil. The force exerted between the coil and armature arises from a gradient in the mutual inductance between them. The directionality of that force is a function of the relative positions of the coil and armature (i.e., the way the electromagnetic field couples to the armature). The rail coils described above are examples of “side-load” electromagnetic coils. Much of the force generated between a side-load coil and an armature is in the direction between the coil and the armature. In the case of an electromagnetic missile launcher, however, it is most desirable to direct the force applied to an armature along the launch axis of the missile launcher.
In a maximally-efficient electromagnetic missile launch system, all of the generated electromagnetic force is directed along the launch axis. As is described below and with respect to
Since it is more efficient, the arrangement of propulsion coils depicted in
Missile canister 506 provides a substantially air-tight environment for missile 202, armature 502, guide rail 504, pilot accelerator 508, rail coils 510-1 through 510-3, and current umbilical 516, in well-known fashion. In some alternative embodiments of the present invention, some of pilot accelerator 508 and rail coils 510-1, 510-2, and 510-3 are located outside missile canister 506.
Missile 202 comprises an explosive warhead, a chemical-propellant engine, and accelerometer 520 for providing acceleration information as is well-known in the art. It will be clear to those skilled in the art, after reading this disclosure, how to make and use missile 202.
Armature 502 comprises sled 520, sled coil 522, and reflector 524. Sled 520 comprises a rigid platform of suitable size for supporting missile 202. Sled coil 522 comprises a helical coil of electrical conductor, capable of carrying sufficiently high voltage/amperage to enable sufficient launch power, and sled coil 522 is substantially immovable with respect to sled 520. The mutual inductance of sled coil 522 and booster coil 514 generates an electromagnetic force along axis 518 when booster coil 514 is energized with electric current. In similar fashion, the mutual inductance of sled coil 522 and each of rail coils 510-1 through 510-3 generates an electromagnetic force along axis 518 when one or more of rail coils 510-1 through 510-3 is energized with electric current. Reflector 524 is a mirror for reflecting an optical beam back to sled-position sensor 512 in known fashion. In some embodiments of the present invention, sled coil 514 is carries electric current supplied by power system 108. In these embodiments, the direction of electromagnetic force generated by sled coil 522 along axis 518 depends on the direction of current flow in sled coil 522.
Prior to a launch, armature 502 is rigidly attached to missile canister 506 by a sled restraint bolt, and missile 202 is attached to armature 502 by missile restraint bolts. Bearings for guiding armature 502 along guide rail 504, the missile restraint bolts, and the sled restraint bolt are not shown for clarity. It will be clear to those skilled in the art how to make and use sled bearings, missile restraint bolts, and sled restraint bolts. It will be clear to those skilled in the art, after reading this disclosure, how to make and use armature 502.
Guide rail 504 comprises four vertical members that provide structural support for missile canister 506, pilot accelerator 508, and rail coils 510-1 through 510-3 which are affixed to guide rail 504 in a substantially-immovable manner. Guide rail 504 also provides straight, smooth tracks against which the sled bearings ride during a launch. Although the illustrative embodiment comprises four (4) vertical structural members, it will be clear to those in skilled in the art, after reading this disclosure, how to make and use embodiments of the present invention that comprise any number of vertical structural members.
Pilot accelerator 508 is located behind the rest position of armature 502 on axis 518 and comprises booster coil 514. Booster coil 514 is a helix of electrical conductor capable of carrying sufficiently high voltage/amperage to enable sufficient electromagnetic energy to: (1) initiate motion of armature 502 from a rest position; and (2) propel armature 502 into a suitable position for continued acceleration by electromagnetic force generated by rail coil 510-1. Booster coil 514 generates electromagnetic force along axis 518 when energized with electric current. The direction of electromagnetic force generated along axis 518 by booster coil 514 depends on the direction of current flow in the coil. It will be clear to those skilled in the art, after reading this disclosure, how to make and use booster coil 514.
Current umbilical 516 comprises electrical conductors of sufficient length to span the length of travel of armature 502 during a launch. Current umbilical 516 is electrically-connected to current cable 114 and provides electrical connection of armature 502 to power system 108 throughout the entire launch. Prior to the launch, targeting information is passed from launch controller 104 to missile 202 via a canister-to-sled umbilical and sled-to-missile umbilical in similar fashion to current cable 516. For the sake of clarity, these umbilical lines are not shown in
Although the embodiment depicted in
Rail coils 510-i, where i=1 to 3, each comprise a helix of electrical conductor, wherein each helix has an inner diameter larger than the outer diameter of sled coil 522, and wherein the electrical conductor is capable of carrying sufficiently high voltage/amperage to enable sufficient launch power. Each rail coil 510-i generates electromagnetic force along axis 518 when energized with electric current. The direction of electromagnetic force that is generated along axis 518 by each of rail coils 510-i depends on the direction of current flow in that coil. It will be clear to those skilled in the art, after reading this disclosure, how to make and use rail coils 510-i.
Sled-position sensor 512 is an optical range-finding device on the bottom of missile canister 506. Sled-position sensor 512 transmits an optical beam at reflector 524, which is located on the bottom of armature 502, and determines the position of armature 502 based on the time-of-travel of the reflected optical beam. The position of armature 502 is used by launch controller 104 to sequence current flow in booster coil 514 and rail coils 510-1, 510-2, and 510-3. In some embodiments, the position of armature 502 is used by launch controller 104 to control current flow in sled coil 522. It will be clear to those skilled in the art, after reading this disclosure, how to make and use sled-position sensor 512 and reflector 524.
Referring now to
At task 602, launch controller 104 passes target information to missile 202.
At task 603, power system 108 energizes booster coil 514 with current supplied on current cable 114. Power system 108 controls the flow of electric current in booster coil 514, which is substantially immovable with respect to missile canister 506. The current flow is controlled such that a first electromagnetic force is generated along axis 518 by booster coil 514. The direction of the generated force is made so as to cause a repulsive force between armature 502 and booster coil 514 that is directed along axis 518. When the magnitude of the repulsive force exceeds a pre-determined threshold, the sled restraint bolt releases, and armature 502 is allowed to travel along axis 518 toward the muzzle end of launcher 102 and toward the interior volume of rail coil 510-1. In some alternative embodiments, power system 108 also controls the flow of electric current in sled coil 522. In some alternative embodiments, the current flow in sled coil 522 is controlled such that a second electromagnetic force is generated along axis 518 so as to increase the force applied to armature 502. Due to its proximity and orientation with respect to armature 502, the electromagnetic force generated by booster coil 514 is more efficiently coupled to the armature 502 than the electromagnetic force generated by rail coils in prior art electromagnetic missile launchers.
At task 604, as armature 502 travels along axis 518, power system 108 sequences the flow of current in booster coil 514 and rail coil 510-1 in order to substantially maximize the efficiency of the propulsion of armature 502. As armature 502 continues its travel along axis 518, power system 108 sequences the flow of current in rail coils 510-1, 510-2, and 510-3 to substantially maximize propulsion of armature 502 toward the muzzle end of launcher 102. The illustrative embodiment comprises four propulsion coils, booster coil 514, and rail coils 510-1, 510-2, and 510-3. It will be clear to those skilled in the art, however, after reading this specification, how to make and use alternative embodiments of the present invention that comprise any number of coils that are:
At task 605, sled-position sensor 512 transmits a signal to launch controller 104 to indicate that armature 502 is nearing the end of its travel along axis 518. In response, launch controller 104 changes the flow of electric current in coils 510-1 through 510-3 to begin to decelerate armature 502.
At task 606, accelerometer 520 senses the deceleration of armature 502 and provides a signal that is used to (i) actuate the missile restraint bolts, and (ii) initiate ignition of the missile's chemical-propellant engine.
At task 607, armature 502 throws missile 202 with sufficient velocity that missile 202 obtains aerodynamic flight away from launcher 102.
At task 608, the chemical-propellant engine is ignited once missile 202 has achieved sufficient clearance from launcher 102 but before missile 202 has lost aerodynamic stability.
It will be clear to those skilled in the art, after reading this disclosure, how to make and use accelerometer 520. Furthermore, it will be clear to those skilled in the art, after reading this specification, how to make and use alternative embodiments of the present invention that use other means of initiating ignition of the chemical-propellant engine such as a signal from an altimeter, a timing circuit, a fuse, or signal transmitted to missile 202 from weapons control system 106.
It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. For example, in this Specification, numerous specific details are provided in order to provide a thorough description and understanding of the illustrative embodiments of the present invention. Those skilled in the art will recognize, however, that the invention can be practiced without one or more of those details, or with other methods, materials, components, etc.
Furthermore, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the illustrative embodiments. It is understood that the various embodiments shown in the Figures are illustrative, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present invention, but not necessarily all embodiments. Consequently, the appearances of the phrase “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout the Specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.
This invention was made with Government support under Cooperative Research and Development Agreement No. SC99/01573 awarded by the Department of Energy. The Government has certain rights in the invention.
