Abstract:
A rock pulverizer device based on a superconducting linear motor. The superconducting electromagnetic rock pulverizer accelerates a projectile via a superconducting linear motor and directs the projectile at high speed toward a rock structure that is to be pulverized by collision of the speeding projectile with the rock structure. The rock pulverizer is comprised of a trapped field superconducting secondary magnet mounted on a movable car following a track, a wire wound series of primary magnets mounted on the track, and the complete magnet/track system mounted on a vehicle used for movement of the pulverizer through a mine as well as for momentum transfer during launch of the rock breaking projectile.

Description:
GOVERNMENTAL INTEREST 
       [0001]    The U.S. Government has a paid-up license in this invention, and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of a grant awarded by the National Aeronautics and Space Administration (NASA). 
     
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates generally to a method and apparatus for pulverizing a formation including useable raw materials such as an ore, coal or the like using a high speed projectile accelerator to hurl projectiles at the formation to breakup or pulverize a portion of an exposed surface of the formation. 
         [0004]    More particularly, the invention relates to an apparatus for hurling one projectile or a plurality of projectiles at an exposed surface of a formation including a projectile car mounted on a track having two parallel rails, where the car includes a trapped field magnet and the track includes a plurality of electromagnets that can be turned on and off as the car moves down the track accelerating the car to a desired velocity. The apparatus also includes a stop assembly at its distal end designed to engage and nearly instantaneously stop the forward motion of the car expelling the projectile or the projectiles disposed in a projectile holder on the car. If the distal end of the apparatus is positioned adjacent a surface, then the projectile would impact the surface breaking or pulverizing the surface. The invention also relates to a method for breaking up or pulverizing a surface using the apparatus of this invention. In one embodiment, the apparatus comprises a superconducting linear motor. 
         [0005]    2. Description of the Related Art 
         [0006]    The mining industry has a significant need for an apparatus and method to breakup large rock sections loosened during mining operations such as blasting or other means. These rock sections can be up to 30 cubic meters in volume, and require break up into smaller pieces for transport out of the mine. Several approaches have been tried including: (1) additional blasting—this is not necessarily cost effective due to the need for drilling new set-charge holes, setting new charges, evacuating the mine and removing the residual gas; (2) steam/compressed air hammers—this requires a source of steam or compressed air and is limited as to hammer size and velocity; and (3) rf induction heating to fractionate—this requires water porosity of the rock structure, large and inefficient rf transmitters and safety procedures to protect against high levels of rf radiation. To pulverize a 30 cubic meter section of rock, energy of approximately 1 Mjoule is required. As an example, for a projectile launcher, this would require a projectile of approximately 1,000 kg at a speed of about 33 meters/sec (about 75 miles/hr). These requirements show the inadequacy of using a steam/compressed air hammer approach to break rock. 
         [0007]    Electromagnetic motors have been described for the acceleration of a mass for warfare applications as in a rail gun in U.S. Pat. No. 5,078,043 (column 5) which patent is incorporated herein by this reference. The inclusion of superconducting material to a rail gun has also been described in U.S. Pat. No. 4,901,621 (column 2), which patent is incorporated herein by this reference. 
         [0008]    There is a need, therefore, for a system (such as an electromagnetic launch system) to accelerate a projectile to the required speed over moderate lengths compatible with mine dimensions and mine operations and cause pulverization of rock with the projectile. 
       SUMMARY OF THE INVENTION 
       [0009]    The apparatus of the present invention is a trapped field superconducting secondary magnet mounted on a movable car following a track, a wire wound series of primary magnets mounted on the track, and the complete magnet/track system mounted on a vehicle used for movement of the pulverizer through a mine and for momentum transfer during launch of the rock breaking projectile The method of the present invention accelerates a projectile via a superconducting linear motor and directs the projectile at high speed toward a rock structure that is to be pulverized by collision of the speeding projectile with the rock structure. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention can be better understood with reference to the following detailed description together with the appended illustrative drawings in which like elements are numbered the same: 
           [0011]      FIGS. 1A&amp;B  depict an embodiment of a track system of this invention; 
           [0012]      FIG. 1C  depicts another embodiment of a track system of this invention; 
           [0013]      FIG. 1D  depicts another embodiment of a track system of this invention; 
           [0014]      FIGS. 2A-C  depicts another embodiment of a track system of this invention; 
           [0015]      FIGS. 3&amp;B  depicts another embodiment of a track system of this invention; 
           [0016]      FIGS. 4A&amp;B  depicts another embodiment of a track system of this invention; 
           [0017]      FIG. 5A  depicts a vehicle apparatus of this invention; 
           [0018]      FIG. 5B  depicts another vehicle apparatus of this invention; and 
           [0019]      FIG. 5C  depicts a front view of a track shield of this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The inventor has found that a rock pulverizing system can be constructed including a rail system having a car adapted to move along the rail system via magnetic forces produced by primary winding in the rail system and a trapped field magnet in the car. The rail system also includes a car breaking or deceleration system which stops the car after its is accelerated via magnetic attraction between successively activated primary winding and the trapped field magnet in the car. The car supports a projectile, which can be retrievable or expendable, and which is ejected from the car when the car is decelerated by the deceleration system. The deceleration or breaking occurs in such as way that the project is dispelled from the car with sufficient momentum to pulverize a target earth/rock formation. If the projectile is retrievable, then after the project is ejected and impinges on the target, the projectile is retrieved and repositioned on the car. The car is then return to its start position so that the car can again be accelerated down the track and decelerate ejecting the projectile at a new target. If the projectile is expendable, then the car is repositioned and a new expendable projectile is loaded onto the car so that the car can again be accelerated down the track and decelerate ejecting the projectile at a new target. 
         [0021]    The superconducting rock pulverizer presented here uses a superconducting linear motor containing monolithic YBa 2 Cu 3 O 7-x  trapped field superconducting magnet as the moving secondary magnet of the linear motor, and a series of wire-wound primary magnets located along a track on which the secondary superconducting magnet travels. 
         [0022]    The secondary magnet is formed preferably from high temperature superconducting YBa 2 Cu 3 O 7-x  elements. It can also be formed from other bulk or thin film superconducting materials including BiSrCaCuO, ThSrCaCuO, HgSrCaCuO, MgB 2 , TiNb, or other high temperature or low temperature superconducting material. To form the superconducting secondary magnet, the superconductors are cooled to below their critical temperature, Tc, while in a magnetic field of appropriate magnitude for the rock pulverizer. Thus, the superconductors capture the magnetic flux and become magnets. They remain magnets as long as they are kept at a temperature below Tc. For the high temperature superconductor YBa 2 Cu 3 O 7-x  it is preferable to cool with liquid nitrogen the boiling point of which (77K is well below the critical temperature of 91K. Cooling can also be accomplished by various cryocooler means. The superconducting elements comprising the secondary magnet can be stacked so as to maximize force applied to the secondary by the primary magnet. The size and shape of the secondary magnet elements are tailored for the required final velocity and mass of the projectile under acceleration over the desired lengths of the linear motor track (often as defined by the design parameters of the mine). The mass of the projectiles can range from about 50 kg to 2000 kg or more. The secondary superconducting magnet is attached to a car that moves on the track formed by the primary coil magnets. 
         [0023]    The primary coil magnets are linearly stacked and are energized as the secondary magnet approaches, and are de-energized when the secondary magnet passes. The primary coil magnets can be energized with current by direct contact through brushes on the secondary magnet car or via a contact-less mode. The primary coils or electromagnets can be made of wire comprised of copper, aluminum, or other metallic materials, or superconducting materials or mixture or combinations thereof. The superconducting wire can be of high temperature superconductors such as YBa 2 Cu 3 O 7-x , BiSrCaCuO, ThSrCaCuO, HgSrCaCuO, or other high temperature superconductors, or of other superconductors such as MgB 2  or TiNb or mixtures or combinations thereof. Higher operating temperature wire can be more beneficial as costs of insulation and heat loss are reduced. 
         [0024]    The superconducting linear motor has a track length along which the secondary travels, that is defined by the critical transit dimensions of the mine, and by the required force and resultant acceleration and final velocity applied by the secondary magnet to the projectile over the length of the primary coil and track system. The superconducting secondary magnet is attached to a car that follows the primary track and had accommodations for brush contact or non-contact energizing of the primary coil sections as the car passes. The car holds the projectile, and projectile retrieve system for tethered projectiles. The car rides on the track with sliding or bearing contact, or has the possibility of being levitated above the track through the application of additional superconducting or non-superconducting magnets. 
         [0025]    The primary coil magnets along with the secondary magnet and car, comprising the superconducting pulverizer are attached to a vehicle such as a standard mine scoop, or a specifically built ‘mule’ vehicle that is able to manipulate/move the pulverizer to wherever it is needed in the mine, to allow for connection of electrical power to energize the pulverizer, and to provide the inertia for momentum transfer to effectively operate the pulverizer. The momentum of the projectile upon release is projected for a 500 kg projectile @45 m/sec to be 22,500 kgm/sec. To minimize recoil of the pulverizer system attached to the vehicle, the mass of the vehicle is projected to be greater than 5,000 kg. Resulting recoil of the vehicle and pulverizer is then less than ˜4.5 m/sec and can be accommodated by vehicle braking, anchoring the vehicle to the mine floor/walls through springs, or other confinement techniques. 
       DETAILED DESCRIPTION OF THE DRAWINGS 
       [0026]    Referring now to  FIGS. 1A&amp;B , an embodiment of a superconducting electromagnetic projectile acceleration apparatus, generally  100 , of this invention is shown to include a power supply component  102 , a track component  120 , and a projectile car component  160 . 
         [0027]    The power supply component  102  includes a current in cable  104  and a current out cable  106 . The two cables  104  and  106  are connected to a DC power supply  108 . The track component  120  includes a left side rail  122   a,  a right side rail  122   b,  and a central rail component  124 . The left side rail  122   a  and right side rail  122   b  include central support members  126   a &amp; b  and a plurality of conductive members  128   a &amp; b  mounted on the support members  126   a &amp; b.  The conductive members  128   a &amp; b  include vertical sections  130   a &amp; b,  a horizontal section  132   a &amp; b  having top rail contacts  134   a &amp; b  and L-shaped feet  136   a &amp; b  having bottom rail contacts  138   a &amp; b.  The conductive members  128   a &amp; b  are all interconnected by the laterally extending conductive feet  136   a &amp; b.  The left side rail  122   a  is connected to the current in cable  104  at the left rail contacts  138   a  disposed in bottom surfaces  140   a  of the feet  136   a;  while the right side rail  122   b  is connected to the current out cable  106  at right rail contacts  138   b  disposed in bottom surfaces  140   b  of the feet  136   b.    
         [0028]    The central rail component  124  includes a current in rail  142   a  having a current in bottom contact  144   a  disposed in a bottom surface  146   a  of a current in foot  148   a  and a current in top contact  150   a  disposed in its top current in rail surface  152   a.  The central component  124  also includes a current out rail  142   b  having a current out bottom contact  144   b  disposed in a bottom surface  146   b  of a current out foot  148   b  and a current out top contact  150   b  disposed in its top current out rail surface  152   b.  The current in bottom contact  144   a  is connected to the current in cable  104 ; while the current out bottom contact  144   b  is connected to the current out cable  106 . 
         [0029]    The car component  160  includes a projectile holder  162  mounted on a car body  164 . The car body  164  includes a superconducting trapped field magnet  166  mounted laterally in an interior  163  of the body  164  near its proximal end  168  ( FIG. 1B ). The body  164  includes two current rail grooves  170   a &amp; b  disposed in a bottom surface  172  of the body  164  having car bottom contacts  174   a &amp; b  disposed in groove top surfaces  176   a &amp; b.  The grooves  170   a &amp; b  are adapted to engage the current in rail  142   a  and the current out rail  142   b  of the track component  140 , respectively, so that the car bottom contacts  174   a &amp; b  are brought into electrical contact or into electrical communication with the corresponding contacts  152   a &amp; b  of the central rail component  124  of the track component  120 . The car component  160  also includes two rail engaging U-shaped members  178   a &amp; b  including car top contacts  180   a &amp; b.  The U-shaped member  178   a &amp; b  are adapted to surround and engage an upper section of the rails  122   a &amp; b,  respectively, so that the car top contacts  180   a &amp; b  are brought into electrical contact or into electrical communication with the top rail contacts  134   a &amp; b  of the rails  122   a &amp; b.  The body  164  also include a cryocooler  182  adapted to maintain the superconducting trapped field magnet  166  at or below it critical transition temperature, T c . The top car contact  180   a  is connected to the bottom car contact  174   b  via a wire  184   a;  while the top car contact  180   b  is connected to the bottom car contact  174   a  via a wire  184   b.    
         [0030]    Referring now to  FIG. 1C , another embodiment of a superconducting electromagnetic projectile acceleration apparatus, generally  100 , of this invention is shown to include a power supply component  102 , a track component  120 , and a projectile car component  160 . In this embodiment, the car body  164  includes two superconducting trapped field magnets  166   a &amp; b  mounted laterally in the interior  163  of the car body  164 , one near its proximal end  168  and one near its distal end  169 . Each magnet  166   a &amp; b  is contained within a separate cryocooler  182   a &amp; b,  but the cryocooler  182   a &amp; b  can be combined into a single cryocooler. Unlike the embodiment of  FIGS. 1A&amp;B , the feet  136   a &amp; b  are non-conductive. Instead, each conductive member  128   a &amp; b  is connected to the appropriate electrical cable  104  or  106  as shown so that they can be separately controlled. Although two superconducting trapped field magnets are disclosed herein, the car can have a higher number of superconducting trapped field magnets with accompanying contacts, limited only by the size of the car and the amount of acceleration to be imparted to the car. Generally, the upper limit will be less than 10 superconducting trapped field magnets. 
         [0031]    Referring now to  FIG. 1D , another embodiment of a superconducting electromagnetic projectile acceleration apparatus, generally  100 , of this invention is shown to include a power supply component  102 , a track component  120 , and a projectile car component  160 . In this embodiment, the car body  164  includes two superconducting trapped field magnets  166   a &amp; b  mounted laterally in the interior  163  of the car body  164 , one near its proximal end  168  and one near its distal end  169 . Each magnet  166   a &amp; b  is contained within a separate cryocooler  182   a &amp; b,  but the cryocooler  182   a &amp; b  can be combined into a single cryocooler. The track component  140  includes isolated conductive members  128   a  and  128   b.  The car contacts are designed so that the magnets  166   a &amp; b  are pushed by conductive members behind of the magnets and pulled by conductive members in front of the magnets. The push-pull configuration is controlled by the current direction flowing through the conductive members. In such a configuration, alternating conductive members on each rail  122   a  and  122   b  have current flowing in the opposite direction. Moreover, the two tracks are do not have the same current flow pattern, but one is one member offset so that the magnetic fields generated by the flowing current push and pull in unison. Although two superconducting trapped field magnets are disclosed herein, the car can have a single superconducting trapped field magnet or a higher number of superconducting trapped field magnets with accompanying contacts, limited only by the size of the car and the amount of acceleration to be imparted to the car. Generally, the upper limit will be less than 10 superconducting trapped field magnets. 
         [0032]    Referring now to  FIG. 2A-C , another superconducting electromagnetic rock pulverizer track system  200  includes a dual-rail track component  202  having a left side rail  204   a  and a right side rail  204   b,  each rail including a plurality of primary coil magnet windings  206   a &amp; b,  a superconducting trapped field magnet  208 , which is mounted in an interior  210  of a car  212  riding on the primary magnet rails  204   a &amp; b.  The field magnet  208  is enclosed in a thermally insulated cryocooler  214 , which can be a contained filled with liquid nitrogen or other cryogenic fluid for keeping the superconducting magnet  208  at a temperature below its critical temperature. For example, if the superconducting field magnet  208  comprises YBCO, then the liquid is liquid nitrogen, 77K. The cryocooler can also be a cryocooler system to keep the superconducting magnet below its critical temperature. The car  212  moves on the track component  202  either on lubricated slides or on bearings or any other mechanism for reducing friction as one surface move on other surface. The system  200  also includes a power supply (not shown) to which are connected a current in cable  216  and a current out cable  218 . The current in cable  216  is connected to current in contacts, brushes or leads  220   a &amp; b  on the car  212  and the current out cable  218  is connected to current out contacts, brushes or leads  222   a &amp; b  on the car  212 . The current in contacts  220   a &amp; b  and the current out contacts  222   a &amp; b  are configured on the car  212  so that the windings  206   a &amp; b  are charged through contacts or leads  224   a &amp; b  on the windings  206   a &amp; b  as the car  212  travels down the track component  202 . The car  212  and the track component  202  are configured so that windings  206   a &amp; b  are charged by the leads  220   a &amp; b  and  222   a &amp; b  so that the charged windings  206   a &amp; b  push and pull against the field magnet  206  in the car  212  accelerating the car  212  from the first windings to the last windings. The car  212  of  FIG. 2A-C , is designed so that four windings push and four winding pull the trapped field magnet. The car  212  also includes a projectile holder  226  into which projectiles are placed and ejected from the holder  226 , when the car  212  is stopped suddenly at a distal end of the track system. The car  212  included two U-shaped rail engaging members  228 . The member  228  engaged the rails  204   a &amp; b  via a lubricated slid or bearings  230 . Brushless non-contact system can also be used to energize of the windings as the car moves down the track. It should be recognized that the car can include numerous different contact patterns. For example, the car contacts can be configured so that only a single pair on windings push the car, only a single pair of winding pull the car, a single pair of windings push and a single pair pull, a plurality of windings push, a plurality of winding pull, or a plurality of windings pull and a plurality of winding push. The car can also be configured with one or more field magnets and any arrangement on contacts to charge the windings needed to accelerate the car from a start end of the track system to the stop end of the track system. 
         [0033]    Referring now to  FIGS. 3A&amp;B , another superconducting electromagnetic rock pulverizer track system  300  is shown as a cylindrical shape. The system  300  includes a cut-cylindrical track component  302  having a left side rail  304   a  and a right side rail  304   b.  The system  300  also includes a plurality of lower portions  306  of primary windings  308 . The lower portions  306  of the windings  308  are designed to be brought into electrical contact or communication with four upper portions  310  of the windings  308  disposed in a car component  312 . The lower portions  306  and the upper portions  310  of the winding  308  are brought into electrical communication as the car component  312  travels down the track component  302  via track contacts, leads or bushes  314  and car contacts or leads  316 . The car component also includes three superconducting trapped field magnets  318   a - c.  The windings  308   a - d  are closed by the contacts  314  and  316  and generate magnetic fields that push and pull the magnets  318   a - c,  when power is supplied to the four completed windings  308   a - d.  The magnets  318   a - c  are disposed in an interior  320  and contained within a cryocooler  322 . 
         [0034]    Referring now to  FIGS. 4A&amp;B , another superconducting electromagnetic rock pulverizer track system  400  is shown as a monorail. The system  400  includes a monorail track component  402 . The system  400  also includes a plurality of primary windings  404  contained in an upper portion  406  of the monorail  402 . Each winding  404  includes a current in lead  408  connected to a current in cable  410  and a current out lead  412  connected to a current out cable  414 . The system  400  also includes a car component  416  mounted on the monorail  402  and riding on bearings or lubricated slides  418 . The car  416  includes four superconducting trapped field magnets  420   a - d  contained in cryocoolers  422   a - d.  The windings  404   a - e  are energized by a control system located on a vehicle used to maneuver the system  400  adjacent a surface to be pulverized. Thus, the car  416  is accelerated down the track  402  via a controlled turning on and off windings  404  as the car  416  moves down the track  402 . Mounted on a top  424  of the car  416  is a projectile holder  426  holding a projectile  428 . When the car  416  is rapidly decelerated as shown in  FIGS. 5A-B , the projectile  416  is ejected from the holder and impinges on the surface. 
         [0035]    Referring now to  FIGS. 5A&amp;B , two embodiments of a pulverizing vehicle apparatus, generally  500 , are shown to include the track system  200 , but track system  100 ,  300 , or  400  can be used as well, is mounted at its proximal end  250  on a vehicle  502  for movement and positioning of the track system  200  to a desired location; for example, the vehicle can be a vehicle used in a mine so that the track system  200  can be positioned adjacent a surface to be pulverized. The vehicle  502  also includes command and control equipment for the track system  200 , and a power supply for supplying electrical energy to the track system  200 , via current in and current out cables  504  and  506 , respectively. The vehicle  502  can be a standard mine scoop modified to accept the track systems  200 , or a specifically designed and built “mule” vehicle. 
         [0036]    The track system  200  is attached to the vehicle  502  via a hydraulic system  508  including a hydraulic reservoir pump unit  510 , a track raising/lowering unit  512  and a hydraulically adjustable wheel assembly  514  having a wheel  516  and a hydraulic lift unit  518  positioned near a distal end  520  of the apparatus  500  as shown in  FIG. 5B . The pump unit  510  is connected to the track raising/lowering unit  512  and the lift unit  514  via hydraulic lines  522 . The hydraulic system  510  is adapted to raise or lower the track system  200  or to move the track system  200  from side-to-side so that the distal end  520  of the apparatus  500  can be positioned adjacent a projectile target surface. 
         [0037]    The vehicle  502  also supports blast shields  524  and  526  to protect the operator and the components of the track system  200 , respectively. The vehicle  504  also contains an electrical energy storage system  528 , which activates the primary windings or conductive elements of the track system  200  via the current in and out cables  504  and  506 . The apparatus  500  can use capacitors, flywheels, batteries, superconducting magnetic energy storage or other energy storage devices not shown connected to the system  528  via umbilical  530 . The vehicle  502  can also contain a separate electrical energy source for energizing the primary coil circuits. This source could be a generator, fuel cell, or other electrical generation system not shown. 
         [0038]    The apparatus  500  also includes a mechanized reel mechanism  532  having a reel  534  and a control cable  536  wound onto the reel  534  with a cable&#39;s distal end  538  attached to the car system  212  as shown in  FIG. 5A . The mechanism  532  is adapted to pay-out the cable  536  as the car system  212  is accelerated down the track component  202 , and to reel-in of the car  212  back to the proximal end  250  of the track system  200  after a projectile  540  contained within the car holder  226  is released. The blast shield  526  is shown in a front view in  FIG. 5C  to have an opening  542  therein to permit the projectile  540  to be ejected through the shield  526 . 
         [0039]    The apparatus  500  also includes a deceleration system  544  disposed at its distal end  520  and attached to a distal end  252  of the track system  200 . The deceleration  544  system can include electromagnetic windings (not shown) that can be energized to slow down and stop the car component  212  of the track system  200 . The deceleration system  544  can also be a shock-in-spring deceleration system  546  as shown in  FIG. 5A . The shock-in-spring deceleration system  546  includes a plurality of spring units  548 , which can be traditional springs or shock absorbers including springs and/or air springs. The deceleration system  544  can also be an air compressions unit  550  including a piston  552  moving in a cylinder  554 , where compressing air provided the deceleration necessary to stop the car and eject the projectile  540 . The deceleration system  544  can also be of varying design from the shock-in-spring design. The deceleration system  544  includes a contact plate  556  that can be a rubberized pad to assist in shock reduction of the car system  212  upon contact with the deceleration plate  556  as shown in  FIG. 5B . The deceleration plate  556  can be supported on slide bearings moving on rods attached to the track system. 
         [0040]    The projectile  540  is carried in the holder  226  attached to the car system  212 . The holer  226  can includes a cable/reel system (not shown) for use with tethered projectiles. The cable/reel system for tethered projectiles is adapted to be mounted on the distal end  520  of the apparatus  500  so that the tethered projectiles can be retrieved after ejection and reused. If a rock is used, then the tethering can be to a wire mesh holding the rock, but generally, for dispensable projectiles such as rock, no tethering system is needed. Although several stopping and rewind system have been disclosed, the car itself as mentioned previously can have on-board braking systems that will brake the car once it has progressed a given distance down the track. The car can also be retracted by simply reversing the current path. This will push/pull the car from the distal end of the track to the proximal end of the track. The current flow can then be reversed for acceleration of the car down the track. If magnetic force is used to restore the car to its start position, then a boost unit can be positioned at the distal end of the track to start the car on its return to the start position. 
         [0041]    The apparatus  500  can also include a car boost unit  558  designed to push the car  212  to start it in motion before or simultaneous with electromagnetic activation. The boost unit  558  can be a hydraulic ram unit, air ram unit, a compressed spring or other acceleration boost device, that includes a push member that is thrust out from the unit pushing the car in to motion. The boost unit  558  can an air or hydraulic ram, a compressed spring, or other acceleration device 
         [0042]    The operation of the superconducting electromagnetic rock pulverizing system  500  is as follows. The projectile  540 , either tethered or un-tethered, is loaded onto the projectile holder  226  attached to the car system  212  located on the track component  202  positioned at the proximal end  250  of the track component  202 . The superconducting trapped field magnet  208 , which is at or below is critical temperature, T c , is magnetized, if it is not already magnetized. There is also the possibility not shown of using a permanent magnet in place of the superconducting magnet especially in the cases where lower mass projectiles are to be used. 
         [0043]    The vehicle  502  is connected to the mine electrical power system through umbilicals  530  or contains its own power generating system, and the electrical energy storage system  528  on the vehicle  502  is energized. The vehicle  502  is moved to place the projectile ejection end  520  of the apparatus  500  adjacent a surface to be pulverized. Exact placement of the track end will be defined by trained operators. Fine positioning of the end of the track can be accomplished through the hydraulic system  510 . 
         [0044]    Once the area around the pulverizer system  500  is cleared of personnel other than the system operators who are behind protective blast shields  524  and  526  on the vehicle  502 , the primary magnet windings  206  are energized generating magnetic fields the act on the superconducting field magnet  208 . This causes the car system  212  to move down the track  202  accelerating every time a new set of primary windings  206  are energized by the brush or brushless contacts on the car  212 . This acceleration continues down the length of the track  202  with the car system  202  supporting the projectile  540  reaching a design velocity nominally 45 m/sec for a 500 kg projectile at the end of the nominally 10 m long track. The last 1 m of the track is a deceleration section where the car system is decelerated and the projectile  500  is ejected from the support basket  226  attached to the car  212 . The deceleration of the car  212  can be accomplished by a passive spring over shock system, or by electromagnetic deceleration from reverse current applied to primary coils located at the last 1 m of track, or by a combination of both systems. 
         [0045]    The ejection of the projectile  500  from the car basket  226  when the car system  212  reaches the distal end  252  of the track  202  is followed by reel-out of the projectile tether for tethered projectiles. After collision of the projectile  540  with the rock, the tether is used to reel the projectile  540  back onto the car basket  226 . The car system  212  along with the tethered projectile  540  is then reeled back to the vehicle end  250  of the track  202  in preparation for the next pulverizing event. 
         [0046]    Blast shields  524  and  526  are strategically mounted near the end of the track to protect the track and secondary magnet/car system as well as any primary magnet windings  206  from shrapnel from flying rock. 
         [0047]    The vehicle  502  can include a DC power supply  528  and necessary control systems to allow the operator to turn on the power supply once the apparatus is properly positioned. The control system can also be used to change the current being delivered to the conductive members of the track. Thus, the current can start off at just the current necessary to start the car moving and increased to increase the acceleration being imparted to the car. Of course, the current density must be kept below the maximum current of the cables and the maximum current capable of being tolerated by the conductive members. 
         [0048]    The apparatus operates by pulling the car to the proximal end of the track component. Next, one or more projectiles are placed on the projectile holder. The car is then accelerated by turning on the DC power supply so that current flows through the feet to the conductive member activated by the car contacts. The current flowing through the conductive members generates a magnetic field that pushes against the superconducting trapped field magnet. Each subsequently activated conductive member continues the acceleration down the track on the rails. The power supply can be adjustable so that the current density is increased as the car moves down the track. At the end of the track, the car is stopped by a breaking system that is generally biased. The stopping is sudden enough to propel the projectiles from the projectile holder at a surface or into a surface of a structure or formation to breakup or pulverize a portion of the surface contacted by the expelled projectiles. The projectiles can be stones or rocks or can be special projectiles designed to more effectively penetrate, breakup or pulverize the surface. The projectiles can be explosively charged. The projectiles can be shaped to spin once be expelled from the holder. 
         [0049]    All references cited herein are incorporated by reference. Although the invention has been disclosed with reference to its preferred embodiments, from reading this description those of skill in the art may appreciate changes and modification that may be made which do not depart from the scope and spirit of the invention as described above and claimed hereafter.