Abstract:
An electrically powered launcher is disclosed that can accelerate small payloads to orbital velocities. The invention uses a novel geometry to overcome limitations of other design, and allows full exploitation of existing superconducting materials.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims provisional priority to U.S. Provisional Patent Application Ser. No. 60/578,272, filed 9 Jun. 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a novel linear motor or linear acceleration apparatus.  
         [0004]     More particularly, the represent invention relates to a novel linear motor or acceleration apparatus utilizing superconductors in a persistent current mode for both a primary and secondary assemblies. The motor is well-suited as electromagnetic payload launch apparatus or as a projectile launch apparatus because sliding current pickups are not needed for the secondary assembly, the power supply can be arbitrarily small, and no quench or other switching of the primary assembly is necessary during a launch of a payload.  
         [0005]     2. Description of the Related Art  
         [0006]     Currently, electromagnetic (EM) launch apparatuses include superconducting motors such as the quench gun and collapsing field accelerator and other linear motors, such as the Electromagnetic Aircraft Launch System (EMALS) being developed by Northrop Grumman and General Atomics and chemical guns, such as the Industrial Sounding System from Columbiad.  
         [0007]     Although considerable research and developments efforts have directed an EM launch apparatus both for use in payload delivery into space or in projectile delivery in weapons, the art is still in the state of rapid development and is still in need of new, different and possibly improved methods for achieving efficient payload delivery both terrestrial and extra-terrestrial payloads.  
         [0008]     The possibility of using electrically powered or electromagnetic (EM) launch apparatus to drastically reduce the cost of placing small payloads in orbit or to delivery small payloads over a large distance has long been known; however, until now, technical obstacles have prevented realization of such launch apparatuses or vehicles. The present invention uses a novel geometry to overcome these technical hurdles, and allows full exploitation of existing superconducting materials.  
       SUMMARY OF THE INVENTION  
       [0009]     The invention is an electrically powered launcher that can accelerate small payloads to orbital and sub-orbital velocities.  
         [0010]     The present invention provides an electromagnetic launch apparatus including a primary assembly and a secondary assembly, where the secondary assembly is designed to be accelerated by the primary assembly down a length of the primary assembly in response to electromagnetic fields in the primary assembly and the secondary assembly.  
         [0011]     The present invention provides an electromagnetic launch apparatus including a primary assembly having a left element and a right element, each element having a longitudinal slot herein and a secondary assembly comprising a closed loop designed to travels down the longitudinal slots and upon which a payload can be coupled.  
         [0012]     The present invention provides an electromagnetic launch apparatus including a primary assembly having a left element and a right element and a secondary assembly comprising a closed loop surrounding the left and right elements and designed to travel down an outside of the primary assembly.  
         [0013]     The present invention provides an electromagnetic launch apparatus including a primary assembly having a left element and a right element and a secondary assembly comprising a closed loop disposed between the left and right elements and designed to travel down between the primary assembly.  
         [0014]     The present invention provides an electromagnetic launch apparatus including a primary assembly comprising a closed cylindrical conductor and a secondary assembly comprising a magnet designed to travel down an interior of the primary.  
         [0015]     The present invention provides an electromagnetic launch apparatus including a primary assembly comprising a plurality of conducting segments, a secondary assembly comprising a magnet designed to travel down the primary adjacent the segments and sliding contacts or a plurality of solid state switches designed to produce a current flow in each successive tooth during a launch cycle.  
         [0016]     The present invention provides an electromagnetic launch apparatus including a primary assembly comprising two comb members, each member having a plurality of teeth, a secondary assembly comprising a magnet designed to travel down the primary adjacent the segments and sliding contacts or a plurality of solid state switches designed to produce a current flow in each successive tooth during a launch cycle.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  depicts a preferred embodiment of a linear acceleration motor apparatus of this invention including a primary assembly having a slot and a secondary assembly designed to move in the slot;  
         [0018]      FIG. 2  depicts a block diagram of the linear acceleration motor apparatus of  FIG. 1 ;  
         [0019]      FIG. 3  depicts an illustration of the magnetic line of flux for the apparatus of  FIG. 1 ;  
         [0020]      FIG. 4  depicts a block diagram of another preferred embodiment of a linear acceleration motor apparatus of this invention;  
         [0021]      FIG. 5  depicts a block diagram of another preferred embodiment of a the linear acceleration motor apparatus of this invention;  
         [0022]      FIG. 6  depicts a block diagram of another preferred embodiment of a the linear acceleration motor apparatus of this invention;  
         [0023]      FIG. 7  depicts a block diagram of another preferred embodiment of a the linear acceleration motor apparatus of this invention;  
         [0024]      FIG. 8  depicts a block diagram of the interaction between the primary assembly and the secondary assembly in a preferred apparatus of this invention and the direction of the fields and forces;  
         [0025]      FIG. 9  depicts a block diagram of the interaction between the primary assembly and the secondary assembly in another preferred apparatus of this invention and the direction of the fields and forces;  
         [0026]     FIGS.  10 A-C depict a top view, an end view and a side view of a linear acceleration motor apparatus of this invention; and  
         [0027]     FIGS.  11 A-B depict photographic images of a preferred embodiment of a working model of a linear acceleration motor apparatus of this invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]     The inventors have found that a linear motor can be constructed using superconducting materials that allow the motor to be used as a launching platform for payloads, where the platform can accelerate the payloads to orbital or sub-orbital velocities. The launching platform is, thus, ideally suited for delivery payloads into space or for other application requiring linear acceleration such as electromagnetic guns, cannons, or rocket launchers.  
         [0029]     The geometry of the Linear Persistent Current Motor (LPCM) apparatus of this invention is related to existing EM launch concepts. The motor apparatus of this invention includes a wound-secondary with the secondary turned by 90 degrees. The motor apparatus of this invention is similar to an apparatus having two augmented railguns operating in parallel, but with links connecting the railgun armature segments.  
         [0030]     The geometry of the LPCM apparatus of this invention has the following advantages: (1) a complete loop in the secondary can operate in persistent current mode, unlike an armature of an augmented railgun; (2) phases of the primary can operate on direct current, or in persistent current mode, unlike the multi-phase AC primary of devices such as the Electromagnetic Aircraft Launch System (EMALS) device; (3) the system as a whole can operate in persistent current mode throughout a launch, without a quench or switching of any kind during a launch. The third advantage means that the launcher apparatus of this invention can be charged gradually with an arbitrarily small power supply, and then, unlike the quench gun or collapsing field accelerator, the apparatus of this invention does not require fast-acting persistent current switches to open primary circuits during a launch cycle. Thus, the LPCM apparatus of this invention overcomes a major obstacle that has prevented adoption of superconducting electromagnetic launchers during the last 20 years.  
         [0031]     The primary use of the linear motor apparatus of this invention will be launching small payloads to high altitudes, or, with rocket assist, into orbit or as a launch platform for projectiles to make EM guns, mortars, cannons, rockets or other types of projectiles. The low launch cost of the linear motor system of this invention will make possible new applications, such as assembly of satellites from multiple small payload launches, satellite maintenance and refueling, and space station resupply. The LPCM apparatus of this invention will be superior to competing chemical systems because it allows greater control flexibility, will likely be smaller and lighter, is likely to have higher maximum end speed, will have lower maintenance requirements, and will be safer to operate.  
         [0032]     Broadly, the present invention relates to a linear motor apparatus including a primary assembly and a secondary assembly. The secondary assembly is designed to travel along a length of the primary assembly. The secondary assembly is designed to be mechanically linked or coupled to a projectile or payload to be launched. The primary assembly is fixed and is designed to generate a magnetic field that is approximately constant during motor operation and during a launch cycle. The primary assembly includes two sides, where the sides are similar if not identical except that they produce fields having opposite directions. The sides of the primary assembly can comprise any material that is capable of generating a magnetic field, such as superconducting windings operating either in persistent or pulsed current mode, arrays of permanent magnets, copper windings, arrays of monolithic superconductors or the like or mixtures or combinations thereof. Each side of the primary assembly can either be split, i.e., the primary assembly has a slot, where the secondary assembly traveling down the slot or down a middle section of the primary assembly, or a single piece that is either on the inside or the outside of the secondary assembly. The secondary assembly typically be a loop composed of any material that can carry a current, such as superconducting wire, copper wire, a ring-shaped superconducting monolith, or mixtures or combinations thererof. Current can be fed into the secondary assembly from rails, or a flexible conductor, or can be induced by a pulsed magnetic field in the primary assembly. Alternatively, the secondary assembly can include only one segment for each side of the primary assembly, oriented for the desired force on each segment. It should be recognized that the primary and secondary assemblies are the primary and secondary parts of a motor and can be made of any material capable of generating a magnetic field or intrinsically has a magnetic field. Of course, the size and uniformity of the magnetic fields will affect the launch velocity of the apparatus. It should also be recognized that the preferred materials out of which both the primary and secondary assemblies is made are superconducting materials.  
         [0033]     The present invention also broadly relates to a method for launching a payload including the step of providing a launch apparatus of this invention. The method also includes coupling or linking a payload with the secondary assembly. Once the payload is coupled to the secondary assembly, the primary assembly is activated and the secondary assembly and the coupled payload is accelerated down a length of the primary assembly. At the end of the primary assembly, the secondary assembly stops and the payload is launched from the apparatus at a specified velocity. If the payload includes a supplemental acceleration component such as a rocket engine, then the method also includes the step of activating the supplemental acceleration component to increase provide additional lift or velocity of the payload. In certain situation, the supplemental acceleration component associated with the payload can be used to aid the payload to reach a desired terminal velocity and/or direction, e.g., the aid the payload reach earth escape velocity for launching payloads into space or into orbit.  
         [0034]     Suitable superconducting materials for use in this invention include, without limitation, normal or classical superconducting metal, metal alloys, or mixtures or combinations thereof, high temperature superconductors, or mixtures or combinations thereof. Exemplary examples of high temperature superconductors include, without limitations, LaCu oxides, LaBaCu oxides, LaSrCu oxides, YbaCu oxides, BiSrCaCu oxides, TlBaCaCu oxides, other high Tc superconducting materials or mixtures or combinations thereof. Exemplary examples include La 2-x Ba x CuO 4 , La 2-x Sr x CuO 4 , La 2-x Sr x CaCuO 4 , YBa 2 Cu 3 O 7-δ , Bi 2 Sr 2 Ca 2 Cu 3 O 10 , Bi 2 Sr 2 Ca—Cu 2 O 8 , Bi 2 Sr 2 Ca 2 Ca 3 O 8 , Tl 2 Ba 2 Ca 2 Cu 3 O 10 , or mixtures or combinations thereof. Preferred HTS includes YBa 2 Cu 3 O 7-δ , La 2-x Sr x CaCuO 4 , Bi 2 Sr 2 Ca 2 Ca 3 O 8 , Tl 2 Ba 2 Ca 2 Cu 3 O 10 , or mixtures or combinations thereof.  
         [0035]     Referring now to  FIG. 1A , a preferred embodiment of a linear acceleration motor apparatus or launch apparatus, generally  100 , is shown to include a housing a housing  102 , which houses a primary assembly  104  having a left superconducting element  106  and a right superconducting element  108 . The left and right superconducting elements  106  and  108  have a longitudinal slot  110  and a central slot  112 . Positioned inside the longitudinal slot  110  is a secondary assembly  114  comprising a superconducting loop. The secondary assembly  114  is designed to travel down a length of the slot  110  in an accelerated fashion. By coupling a payload to the secondary assembly  114  and accelerating the secondary assembly  114  with the coupled payload down the length of the slot  110 , the payload can be launched out of the housing in the direction of a launch arrow  116 , the direction of motion of the secondary assembly  114  relative to the primary assembly  104 .  
         [0036]     Referring now to  FIG. 1B , a start end or start end cross-sectional view of the apparatus of  FIG. 1A . The housing  102  is shown as left and right blocks  118 . Mounted on the blocks  118  are the left and right superconducting elements  106  and  108 . Positioned within the slot  110  is the secondary superconducting loop  114 . A direction of a current  120  flowing in the superconducting loop  114  is shown. Lines of magnetic flux  122  across the slot  110  that act on the loop  114 . The resulting interaction between magnetic field of the primary assembly  104  and the magnetic field produced by the current  120  flowing in the secondary assembly  114  produces an acceleration direction of motion of the secondary assembly  114  into the plane of the  FIG. 1A  as shown by a direction indicator  124 .  
         [0037]     Referring now to  FIG. 1C , a diagram of the magnetic lines of flux of the magnetic field produced by one of the elements  106  of the primary assembly  104  and the magnetic field produced by the secondary assembly  114  to produce an acceleration force on the secondary assembly  114  in the direction of the arrow  116 .  
         [0038]     Referring now to  FIG. 2 , another preferred embodiment of a linear acceleration motor apparatus or launch apparatus, generally  200 , is shown to include a primary assembly  204  having a left superconducting element  206  and a right superconducting element  208 . The left and right superconducting elements  206  and  208  have a longitudinal slot  210 . Also shown are the lines and direction of magnetic flux  222  across the slot  210 . Positioned inside the longitudinal slot  210  is a secondary assembly  214  comprising a superconducting loop having a current flow direction  220 . The secondary assembly  214  is designed to travel down a length of the slot  210  in an accelerated fashion. By coupling a payload to the secondary assembly  214  and accelerating the secondary assembly  214  with the coupled payload down the length of the slot  210 , the payload can be launched in the direction of travel of the secondary assembly  214  as indicated by the direction indicator  224 , which represents an acceleration vector into the plane of the drawing.  
         [0039]     Referring now to  FIG. 3 , another preferred embodiment of a linear acceleration motor apparatus or launch apparatus, generally  300 , is shown to include a primary assembly  302  having a left superconducting element  306  and a right superconducting element  308 . Also shown are the lines and direction of magnetic flux  322  generated by the elements  306  and  308 . The apparatus  300  also includes a secondary assembly  314  comprising a superconducting loop having a current flow direction  220 . The primary elements  306  and  308  are disposed in an interior of the secondary assembly  314 . By coupling a payload to the secondary assembly  314  and accelerating the secondary assembly  314  with the coupled payload down the length of the primary assembly  302 , the payload can be launched in the direction indicated by the direction indicator  324 , which represents an acceleration vector into the plane of the drawing.  
         [0040]     Referring now to  FIG. 4 , another preferred embodiment of a linear acceleration motor apparatus or launch apparatus, generally  400 , is shown to include a primary assembly  402  having a left superconducting element  406  and a right superconducting element  408 . Also shown are the lines and direction of magnetic flux  422  generated by the elements  406  and  408 . The apparatus  300  also includes a secondary assembly  414  comprising a superconducting loop having a current flow direction  420 . The primary elements  406  and  408  are disposed in an exterior of the secondary assembly  414 . By coupling a payload to the secondary assembly  414  and accelerating the secondary assembly  414  with the coupled payload down the length of the primary assembly  404 , the payload can be launched in the direction indicated by the direction indicator  424 , which represents an acceleration vector into the plane of the drawing.  
         [0041]     Referring now to  FIG. 5 , another preferred embodiment of a linear acceleration motor apparatus or launch apparatus, generally  500 , is shown to include a primary assembly  504  comprising a superconducting loop having a current flow direction  505 . The apparatus  500  also includes a secondary assembly  514  including two superconducting elements  526  and  528 . Also shown are the lines and direction of magnetic flux  530  generated by the elements  526  and  528  of the secondary assembly  514 . The secondary elements  526  and  528  are disposed on an exterior of the primary assembly  504 . By coupling a payload to the secondary assembly  514  and accelerating the secondary assembly  514  with the coupled payload down the length of the primary assembly  504 , the payload can be launched in the direction of travel of the secondary assembly  514  as indicated by the direction indicator  524 , which represents an acceleration vector out of the plane of the drawing. The apparatus  500  represents an inversion of the apparatus  100 . That is, in the apparatus  100 , the loop moves relative to the stationary field magnet, while in the apparatus  500 , the field magnet moves relative the stationary loop. In the apparatus  500 , the secondary assembly  514  is short in length compared to the primary windings  504 .  
         [0042]     Referring now to  FIG. 6 , another preferred embodiment of a linear acceleration motor apparatus or launch apparatus, generally  600 , is shown to include a primary assembly  604  comprising a plurality of conductor segments  640  having a current flow I in a direction  605 . The apparatus  600  is similar to the apparatus  500 , but the current loop is replaced by conductor segments fed by sliding contacts as described more fully below. The secondary assembly  614 . The configuration produces a magnetic force  630  and an acceleration force  616 .  
         [0043]     Referring now to  FIG. 7 , another preferred embodiment of a linear acceleration motor apparatus or launch apparatus, generally  700 , is shown to include two primary assemblies  704   a &amp; b  comprising pluralities of conductor segments  740   a &amp; b  having a current flow I in directions  708   a &amp; b  and arranged in a parallel configuration. It should be noted that the current flow direction  708   a  is opposite to the current flow  708   b  in the linear elements  740   a  and  740   b , respectively, so that the magnetic fields  730   a &amp; b  are in the same direction. The apparatus  700  also includes two secondary assemblies  714   a &amp; b . The configuration produces magnetic forces  730   a &amp; b  and acceleration forces  716   a &amp; b . Two of the alternate configuration motors can be used in parallel. A payload  750  can be placed between the secondary magnets  714   a &amp; b , so that a symmetric force is exerted on the payload  750 .  
         [0044]     Referring now to  FIG. 8A -C, another preferred embodiment of a linear acceleration motor apparatus or launch apparatus, generally  800 , is shown to include a primary assembly  804 . The primary assembly  804  includes a current rail  855 , sliding contacts  870 , a plurality of conductor tooth segments  840  extending from a base  841 , and an insulating support  880 . The apparatus  800  also includes a secondary assembly  814  comprising a magnet  815  and a cyrostat  860 . The arrow  830  represents the magnetic force B; the arrow  805  represent the direction of current flow I; and the arrow  816  represents the direction of motion of the secondary assembly  814  relative to the primary assembly  804 . Although the segments  840  are shown here as being short conduct elements, the segments  840  can also be loops.  
         [0045]     Referring now to  FIG. 9A -B, two photographs of the apparatus  800  are shown. The photographs show the housing structure, the primary assembly comprising superconducting segments and the secondary assembly. The photographs also show the electrical wires, cyrostat and other aspects of an actual prototype.  
         [0046]     In the alternate configuration, the secondary magnet, the two sliding contacts, and the payload are connected by a support structure and move as a unit. One terminal of a power supply (e.g., a capacitor bank) is electrically connected to the current feed rail, while the other terminal of the power supply is connected to the toothed primary. A sliding contact rides on the current feed rail, and is electrically connected to another sliding contact that rides the toothed part of the primary. The sliding contact that rides the toothed part of the primary is narrower than a tooth, so that current is fed from the current feed rail, through the sliding contacts, through a single tooth, and returns to the power supply. Each tooth in the primary is preferably narrower than the secondary magnet. The field magnets can comprise either permanent magnets, monolithic superconductors with a trapped field, or a wound superconducting magnet operating in persistent current mode or mixtures and combinations thereof. The toothed part of the primary can comprise a sheet of a good conductor such as copper or aluminum, or superconductors in tape or wire form or mixtures and combinations thereof. The sliding contacts can comprise carbon, copper, other metals or alloys with good conductivity, or a composite of carbon and metal or alloy or mixtures and combinations thereof. The toothed part of the primary is supported by an insulating material, such as polycarbonate or G10 or other similar structural insulators. If a superconducting magnet is used in the secondary, it should be contained in a cryostat that maintains a low temperature during a launch. Variations of this configuration are possible. The current feed rail can be placed in other locations relative to the toothed part of the primary. Multiple secondary magnets can be used, along with multiple sliding contacts. The secondary assembly can be supported by rolling bearings, low friction pads such as PTFE, or by a magnetic levitation structure that is either independent of or makes use of the field magnets.  
         [0047]     The main advantage of the alternate configuration is that it takes advantage of the very high magnetic fields (up to 17 T) that have been demonstrated in small superconducting monoliths. Although this configuration uses a sliding contact, while the others do not, this is thought to be acceptable because sliding contacts have been demonstrated in rail guns to work up to a speed of about 6 km/s. At this speed, energy transfer becomes extremely inefficient (near zero percent efficiency). However, the configuration presented here differs from a rail gun in two important ways: 
        1. The sliding contacts in a rail gun are in a high magnetic field regions. In the alternate configuration, the contacts need not be in a high field regions; additionally, a tailored magnetic field can be applied in this case in order to contain any generated plasma in the regions of the contact.     2. In a rail gun, a significant pressure is exerted on the area of the sliding contact. In this configuration, the sliding contact is only required to support its own mass.        
 
         [0050]     It is therefore expected that this configuration can accelerate payloads to speeds significantly higher than 6 km/s.  
         [0051]     Another advantage of the alternate configuration is that the inductance of the toothed primary is very low. This minimizes the energy that must be dissipated as the sliding contact commutates current from one tooth to the next. It also provides the possibility of using solid-state switches rather than sliding contacts to control current in the teeth. In solenoidal coil guns, the inductance of the coils combined with the switch voltage limit is one of the main limitations of these types of devices achieving launch velocities.  
         [0052]     A prototype of the alternate configuration has been constructed, and demonstrated to accelerate a payload. To date, the prototype has been used with permanent magnets in the secondary, but has been designed so that these permanent magnets can be replaced by existing monolithic superconducting magnets. The acceleration and back electromotive force measured during tests were found to agree with theoretical predictions.