as shown in fig1 and 2 , a rocket 10 of the type for which arming devices in accordance with the present invention are to be used , has a pair of support brackets or shoes 12 and 14 mounted thereon and arranged to support the rocket prior to and during launch by engaging the launch rail of the launching device . the forward shoe 12 has associated with it a pivotably mounted arming lever 16 coupled to an arming mechanism inside the rocket 10 . the arming lever 16 includes an outwardly extending projection in the form of a pin 18 attached to its free end for engagement with an associated mechanism in the arming device of the launcher . positioned on both sides of the forward shoe 12 are a pair of fire button contacts 20 , one of which is shown in fig2 . the contacts 20 are connected to internal rocket ignition circuitry and , when contacted by the launcher arming device , couple the control circuit to fire the rocket motor . the arming lever 16 , when rotated through approximately 80 ° counterclockwise , moves the internal arming mechanism from the &# 34 ; safe &# 34 ; position to the &# 34 ; armed &# 34 ; position . the arming device 30 in accordance with the present invention is shown in the exploded view of fig3 and in the other views of fig4 - 10 of the drawing . the arming device 30 is mounted on a launch rail of a missile launcher ( not shown ) which incorporates power and control circuitry for activating the arming device 30 . such circuitry has been omitted for the sake of simplicity . as indicated in fig2 and 3 , the arming device 30 is in the relative juxtaposition in which the rocket 10 is mounted on the launch rail 32 in preparation for launch . the launch rail 32 is provided with separate sets of guide slots 34 and 36 for engaging respectively the raised lateral extensions 38 and 40 of the forward and aft shoes 12 and 14 of the rocket 10 . it will be noted that the aft shoe 14 is narrower than the forward shoe 12 and its top surface is higher than that of the forward shoe . with the arming lever 16 being recessed somewhat relative to the outer surface of the forward shoe 12 , it will be seen that there is clearnace for the arming lever 16 below the central portion of the launch rail 32 which defines the guide slot 36 . the arming device 30 comprises a gear motor 50 supported in a motor mount 52 affixed to the launch rail 32 . also supported in the motor mount 52 and extending longitudinally from the forward end thereof is a screw member 54 ( see fig6 ) which is coupled to be driven by the shaft of the gear motor 50 by means of a coupling member 56 . a shuttle 60 is constrained by a forward housing 62 , affixed to the launch rail 32 , in a manner which permits bi - directional longitudinal movement of the shuttle 60 when driven by a ball bearing nut 64 ( fig6 ) affixed to the shuttle 60 and mounted on the ball screw member 54 . the so - called &# 34 ; ball bearing screw &# 34 ; comprising the combination of screw member 54 and ball bearing nut 64 is a well - known device for converting rotary motion of a shaft such as the motor 50 into precisely controlled linear motion such as is employed in the present invention to activate the various mechanisms performing the functions described herein . the housing 62 is provided with a pair of rearwardly extending legs 66 which serve , among other things , to restrain the shuttle 60 in position against the launch rail 32 for forward and aft traversal motion as described . a forward travel limit switch 68 is mounted on one of the legs 66 . an aft travel limit switch 70 is mounted on the motor mount 52 . these limit switches 68 , 70 are connected in the control circuitry for the motor 50 and are alternately activated at the respective traversal limits of the shuttle 60 by means of a switch tripper bar 72 affixed to the shuttle 60 in a position to engage the switches 68 , 70 . a pair of fire button arms 76 , one of which is shown in fig3 are pivotably mounted laterally outward of the launch rail 32 at pivot points 78 . each fire button arm 76 has affixed at its outer end a spring - type fire button contact 80 for making contact with the associated contact button 20 of the missile 10 . an inclined slot 82 is cut in the arm 76 through which extends a cam pin 84 which also extends through a horizontal slot 86 in the housing leg 66 and is mounted on the shuttle 60 at the point 88 . by means of the cam pin 84 and the slots 82 , 86 , the arm 76 is caused to rotate about the pivot point 78 as the shuttle 60 traverses back and forth , the fire button contact 80 moving into engagement with the corresponding button 20 of the missile 10 when the shuttle 60 moves to its aft position . mounted interiorly of the shuttle 60 on an arm shaft 90 is an arming member 92 . the arm shaft 90 is held in position in the shuttle 60 by a roll pin 94 . an arming member spring 96 , mounted to engage a notch 97 of the arming member 92 and associated spring collars ( not shown ) positioned interiorly of the shuttle 60 on the shaft 90 , serves to bias the arming member 92 for upwardly rotational movement about the shaft 90 . mounted in the housing 92 is a laterally oriented restraint shaft 102 which has a flat side along the extent thereof . affixed on the shaft 102 in mating recesses of the housing 62 are a pair of restraint levers 104 and an arming member latch 106 . a shear pin 108 extends through a lever portion of the restraint lever 104 and associated portions of the housing 62 . the launch rail 32 is provided with an opening 110 through which the arming member 92 and lower extended portion of the arming member latch 106 extend . the lower portion of the latch member 106 is provided with a pin 112 for bearing against the upper flat surface 114 of the arming member 92 . openings 116 are also provided through which the lower ends 118 of the restraint levers 104 extend . in the &# 34 ; restrain &# 34 ; position , the ends 118 of the restraint levers 104 bear against the forward shoe 12 of the rocket 10 and prevent its release from the launcher . the shuttle 60 is provided with a pair of forwardly extending legs 120 which , when the shuttle 60 is in the forward position , bear against the underside of rearwardly extending portions 122 of the restraint levers 104 , thus preventing the rotation of the restraint levers 104 and release of the rocket 10 , even against full thrust in the event of an inadvertent firing . when the shuttle 60 is in the full aft position , the legs 120 disengage from the rearward portions 122 of the restraint levers 104 so that these levers can rotate to release the rocket . the shear pin 108 is designed to retain the restraint levers 104 in the &# 34 ; restrain &# 34 ; position until the rocket has built up a predetermined minimum thrust , at which point the shear pin 108 ruptures and the rocket is released . details of the underside of the arming member 92 are shown in fig3 a which depicts the member in an inverted position . as shown therein , the underside of the member 92 is provided with a curved cam surface 130 which is so shaped to engage the portion 18 of the arming lever 16 of the rocket 10 and rotate the lever 16 in the counterclockwise direction against clockwise spring bias as the member 92 is moved aft by the traversal of the shuttle 60 in the aft direction as driven by the motor 50 . movement of the member 92 in the forward direction disengages the camming surface 130 from the portion 18 of the arming lever 16 , permitting the latter to return to the &# 34 ; safe &# 34 ; condition . the member 92 is provided with a ramp surface 132 along a rearward portion thereof so that , in the event of failure of the biasing spring 96 , the forward motion of the aft shoe 14 as the rocket 10 is launched , causes retraction of the member 92 through the opening 110 of the launch rail 32 . operation of the device will be described by reference to fig4 - 10 . in particular , fig5 and 6 show the shuttle 60 with associated components in the forward position , corresponding to storage of the rocket 10 on the launcher 32 in readiness for arming and firing . in this position , the forward legs 120 of the shuttle 60 are positioned under the rearward portions 122 of the restraint levers 104 , the lower portions 118 of which engage the portions 38 of the forward rocket shoe 12 so that , even if the rocket were inadvertently fired and developing full thrust , it could not be released from the launch rail 32 . fig7 and 8 illustrate the shuttle 60 and associated components in the aft position in which the missile is armed and in readiness for launch . the arming sequence representing the transition between the positions of fig5 and fig7 is set forth in the following paragraph . the gear motor 50 through the coupling 56 rotates the ball bearing screw member 54 to retract ( move aft ) the shuttle 60 . in moving aft , the shuttle 60 moves the arming member 92 aft across the rocket motor arming lever 16 . the configuration of the cam surface 130 on the underside of the arming member 92 engages the protruding portion 18 of the rocket motor arming lever 16 and , as the arming member 92 moves aft across the lever 16 , it rotates the arming lever 16 to the &# 34 ; armed &# 34 ; position . the same aft movement of the shuttle 60 rotates the fire button arms 76 so that the contacts 80 thereon move down against the rocket motor fire button contacts . this rotation of the arms 76 is a result of the cam pin 84 acting against the inclined cam slots 82 in the fire button arms 76 . also as the shuttle 60 moves aft , the forward legs of the shuttle 60 move out from under the rearward portions 122 of the two restraint levers 104 . the levers 104 are then free to rotate in the clockwise direction after sufficient rocket motor thrust has developed to shear the pin 108 . the proper aft position of the shuttle 60 is sensed by the activation of the aft limit switch 70 . if desired , the rocket motor may be returned to the &# 34 ; safe &# 34 ; condition by simply activating the gear motor 50 to run in the opposite direction so as to drive the shuttle 60 to its forward limit , thus retracting the rocket motor fire button arms 76 and moving the arming member 92 forward , thus safing the rocket motor arming mechanism . when the shuttle 60 is in the forward position , as sensed by the forward limit switch 68 , the restraint levers 104 are prevented from rotating by engagement with the forward legs 120 of the shuttle 60 . fig9 represents the various components comprising the arming device in accordance with the present invention in the launch position with the rocket having been released . the sequence of transition from the armed position of fig7 and 8 to the position of fig9 is described in the following paragraph . in the armed position , the missile is free to fly forward upon ignition by the associated control circuitry of the launcher ( not shown ). as the missile moves forward , after sufficient thrust is developed to shear the &# 34 ; fly - thru &# 34 ; pin 108 , the missile forward shoe 12 pushes against the lower portions 118 of the restraint levers 104 and thus rotates them up out of the way . rotation of the restraint levers 104 in the clockwise direction causes the arming member latch 106 to also rotate , since the restraint levers 104 and the arming member latch 106 are keyed together through the restraint shaft 102 . the arming member 92 is held down in place by the arming member latch 106 until the latter rotates forward so that the lower portion thereof 112 clears the arming member 92 . at that point , the arming member 92 is caused to rotate up through the slot 110 in the launch rail 32 by arming member spring 96 . when the arming member 92 is rotated upward , the aft missile shoe 14 can travel down the slots 36 of the guide rail 32 without interference . in the event of failure of the spring 96 , the arming member 92 is retracted anyway by the aft shoe 14 bearing against the ramp surface 132 . by virtue of the simple but effective construction and cooperation of the components of the mechanism described hereinabove , an arming device achieving extreme simplicity and reliability is provided for performing the functions desired in a vertical launcher of rocket missiles of the type decribed herein . the device has the capability of restraining a rocket against full thrust in the event of inadvertent firing . it effectively arms the missile with the capability of returning the missile from the armed to the safe condition ; and it restrains the missile upon firing until a predetermined minimum thrust is developed which will assure an effective launch . although there has been described above a particular arrangement of a missile launcher arming device in accordance with the invention for the purpose of illustrating the manner in which the invention may be used to advantage , it will be appreciated that the invention is not limited thereto . accordingly , any and all modifications , variations or equivalent arrangements which may occur to those skilled in the art should be considered to be within the scope of the invention as defined in the appended claims .