Abstract:
The invention efficiently and effectively secures and releases a rail-launched missile. An asymmetrical secure-release wheel ( 70 ) is defined by several surfaces which extend radially outward from a pivot hole ( 70 K). The surfaces include a wheel unlatch surface ( 70 H), a wheel notch stop surface ( 70 D), a wheel detent surface ( 70 G), a clockwise stop surface ( 70 C) and a counterclockwise stop surface ( 70 B). The wheel ( 70 ) is rotatable within a wheel housing ( 72 ). When a missile is loaded onto the launch rail, the middle shoe of the missile engages the detent surface ( 70 G) of the wheel. During missile launch, the plume of the missile moves a trigger ( 110 ) which pulls a connecting rod ( 52 ) aft which results in a wheel lock ( 78 ) being disengaged from the detent surface ( 70 G). A microswitch ( 56 ) provides a signal indicating whether the wheel ( 70 ) is in a latched or unlatched state.

Description:
[0001]    The invention described herein may be manufactured, used and licensed by or for the U.S. Government for governmental purposes without payment of any royalties thereon. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention pertains to mechanisms and systems for retaining and releasing a missile on a rail launch system. 
         [0004]    2. Discussion of the Background 
         [0005]    In order to assure accuracy of a missile launcher, it is desirable for a missile launcher to provide a smooth release and induce a minimum of impulse back into the launching platform of an air launched missile. Prior to the fielding of the Army HYDRA 70 Lightweight Launchers, M260 and M261, for the 2.75 Inch Rocket System, the retention mechanisms for tactical launchers fell into three categories. 
         [0006]    The first approach was called a material failure detent. For systems that employ this approach, the munition is restrained by a material component that was designed to fail (i.e. break) when the launch motor thrust became higher than the material strength of the detent. Release force is well controlled in this detent mechanism, but the detent is not reusable. The TOW Missile System is an example of this prior art. 
         [0007]    The second approach is the spring-friction-override detent. For this approach, the munition is retained by a spring-loaded engagement retainer, a.k.a. the detent. The detent has some angle on the engaging surface, or face. As thrust builds up, the munition overcomes friction of the munition against the engaging surface of the detent. This forces the detent out of the way by overcoming the spring force that holds the retainer in place. Older 2.75 Inch launchers, such as the M158 and the M200 are examples of this prior art. Hellfire missile launchers M272, M279, and M299, such as shown in  FIG. 1 , are examples of this prior art. The release force is poorly controlled, but the launcher may be used multiple times. 
         [0008]    The third approach may be termed the umbilical-pull detent. This is the most complicated detent/retention system. For this approach, the missile is retained in its launch tube by the communication and power plug, commonly called the umbilical. At the moment that the external launch command is transmitted to the missile, the missile thermal batteries are energized. When the missile completes pre-launch checkout, a fire pulse is sent to an explosive squib adjacent to the umbilical. When the squib is fired, the umbilical is retracted. 
         [0009]    When the retracted umbilical reaches the end of its motion, a switch is closed and the rocket motor igniter receives a firing pulse over the last external connection to the missile. The missile then is launched out of its tube. During the brief time between umbilical retraction and motor ignition, the missile is held in place by a light spring-friction-detent. The Stinger Surface-to-Air missile is an example of this prior art. This type of detent mechanism is a one-time use only system. 
         [0010]    The newest detent approach is called the blast-actuated detent. This approach was developed for the HYDRA 70 M260 and M261 launchers and these launchers are examples of this prior art, shown in  FIG. 2 . One of the goals of that design was to minimize impulse into the launcher platform during the firing of the rockets. A description of its operation is associated with Prior Art  FIG. 2 . 
         [0011]      FIG. 1  depicts the prior art detent mechanism currently used in the M272, M279, and M299 Hellfire missile launchers. This prior art is the spring-friction-override detent. The detent mechanism is protected from the environment by the detent cover  16 . To load a missile, the sides of the middle and aft missile rail shoes are engaged in the grooves  12 A on the inside of the missile launcher rail  12 . The missile slides aft until the middle shoe on the missile is almost at the detent  10 . The handle  24  that is attached to the detent raising cam  14  is rotated counter-clockwise. Rotating the detent raising cam  14  causes the detent  10  to rotate about the detent retainer pivot shaft  18 . 
         [0012]    As the detent engagement surface  10 A is raised, the detent spring  22  is compressed. The handle  24  is held in position while the missile is pushed aft until the middle shoe firmly rests against the aft missile stop  20 . The handle  24  is then rotated clockwise and returned to its original position. The detent raising cam  14  also returns to its original position. The detent  10  has engaged the middle shoe of the missile. 
         [0013]    The combination of friction between the missile middle shoe, and detent  10  and the spring constant of the detent spring  22  determines the missile release force. 
         [0014]    When a Hellfire missile is to be launched, the missile motor is fired. As thrust builds up, the middle shoe pushes against the detent engagement surface  10 A of the detent  10 . Aided by the angle on the detent engagement surface  10 A, the detent  10  rotates clockwise about detent retainer pivot shaft  18 . As the detent  10  is forced up, the detent spring  22  is compressed down. When the detent  10  is clear of the missile middle shoe, the missile will then move along the launch rail  12  until the middle and aft shoes drop clear of the rail. 
         [0015]      FIG. 2  depicts the prior art detent mechanism currently used in the M260 and M261 varieties of the 2.75 inch diameter Hydra 70 rocket launchers. The detent mechanism holds rockets in the launch tube  26  between the time that the rocket is loaded into the launch tube  26  and the moment the rocket motor is fired. The blast-activated detent mechanism is contained within the detent housing  44 . The detent housing  44  is held on the launch tube  26  with strips of aluminum spot welded to the launch tube  26 . 
         [0016]    When a rocket is loaded, the blast paddle  30  is rotated counter-clockwise about the blast paddle pivot pin  34 . As the blast paddle  30  rotates, the blast paddle cam surface  30 A rubs on the aft portion of the side contact  40 , which is wrapped around the end of the detent housing  44 . The side contact  40  is held in place on the detent housing  44  by two rivets  28 . The action of rotating the blast paddle  30  pulls the sear  38  in the aft direction against the sear spring  36 . The motion of the sear  38  causes the detent  42  to pivot about the detent pivot point  42 B. The aft portion of the detent  42  is forced down while the forward end moves up in the vertical plane. 
         [0017]    The detent  42  is forced against the detent springs  46 . The detent pivot point  42 B is a rectangular hole in the retainer plate  49 . The retainer plate  49  is held in the detent housing  44  by six rivets  48 . The aft motion of the sear  38  removes downward force from the forward end of the side contact  40  causing the contacts to retract out of the launch tube  26 . This clears the way for a rocket to be loaded. The blast paddle  30  is rotated until it passes an over center position, which locks the detent  42  into position for loading a rocket. 
         [0018]    When a rocket is loaded, it is pushed into the launch tube,  26  until it is in contact with the aft stops  32 . To lock the rocket in the launch tube  26 , the blast paddle  30  is rotated clockwise about the blast paddle pivot pin  34  so that it will protrude into the aft opening of the launch tube  26 . The action causes the sear  38  to move forward, forcing the contact points of the side contact  40  into the rocket contact band. The detent  42  is allowed to pivot about the detent pivot point  42 B until the detent engagement groove  42 A of the detent  42  engages the detent ring on the rocket nozzle. The detent springs  46  hold the detent  42  in position while it has engaged the rocket nozzle. 
         [0019]    Launching the rocket consists of a process that is the opposite of loading the launcher. When the rocket motor receives an electrical firing pulse through the side contact  40 , the rocket motor igniter fires and sends hot gases to light the motor grain. The hot gases also exit the rocket nozzle and put an unbalanced gas pressure on the blast paddle  30 . The unbalanced pressure causes the blast paddle  30  to rotate counter-clockwise about the blast paddle pivot pin  34 , with the blast paddle cam surface  30 A sliding over the rub surface of the side contact  40 . As the blast paddle  30  rotates, it pulls the sear  38  aft, compressing the sear spring  36 . 
         [0020]    The motion of the sear  38  allows the side contact  40  to withdraw from the rocket contact band groove. The motion of the sear  38  also causes the detent  42  to rotate about the detent pivot point  42 B in the retainer plate  49  and out of the launch tube  26 . This disengages detent engagement groove  42 A of the detent  42  from the detent ring on the rocket nozzle. The action of the detent  42  compresses the detent springs  46 . As the thrust of the rocket motor builds up, the rocket is free to slide down the launch tube  26  only being restrained by friction. 
       SUMMARY OF THE INVENTION 
       [0021]    The secure-release mechanism of the present invention is used in conjunction with a launch rail such as a missile launch rail provided on a helicopter or aircraft. The secure-release mechanism includes a connecting rod which is connected to and positioned between a wheel assembly and a trigger assembly. The trigger assembly and the wheel assembly are secured to the launch rail with the launch rail having an aperture to allow access to the middle shoe of a missile. 
         [0022]    The trigger assembly includes a trigger housing. A trigger rod extends through the trigger housing and connects to a trigger positioned at the rear or aft of the trigger housing. The trigger rod connects to the connecting rod at a first end of the connecting rod. A spring stop is positioned at a location proximate to where the trigger rod connects to the first end of the connecting rod. A trigger spring is positioned and secured between the spring stop and the trigger housing. 
         [0023]    The wheel assembly includes a wheel housing which engages a wheel slider at a forward section of the wheel housing such that the wheel slider can slide, i.e., is slidable, within the wheel housing. A secure-release wheel is rotatable upon a pivot pin supported by the wheel slider, with the pivot pin being inserted through a pivot hole in the secure-release wheel. The wheel housing is provided with a bushing at the rear end of the wheel housing. A raceway is positioned in a middle section of the wheel housing between the forward section and rear of the wheel housing. 
         [0024]    A wheel lock is in sliding engagement with the raceway of the wheel housing. The wheel lock has a microswitch engagement pin positioned at a lateral side thereof. The rear of the wheel lock is secured to a lock link. The lock link extends through a bushing in the rear of the wheel housing and connects to the second end of the connecting rod. 
         [0025]    The secure-release wheel is asymmetrical and has a plurality of defined surfaces located radially outward from the pivot hole. A wheel unlatch surface of the secure-release wheel contacts the wheel lock when the secure-release wheel is in an unlocked position. A wheel notch leading edge is located between the wheel unlatch surface and a lock surface. A wheel notch stop surface adjacent to the lock surface serves as a stop to the forward axial movement of the wheel lock. A wheel latch leading edge is the leading edge of the secure-release wheel which first contacts the middle missile shoe when a missile is loaded on the launch rail. A wheel detent surface of the secure-release wheel secures the middle shoe of a missile so as to lock the missile in place on the launch rail. The secure-release wheel is further provided with a clockwise stop surface and a counterclockwise stop surface. 
         [0026]    A slider pin supported by the wheel slider is positioned between the clockwise stop surface and the counterclockwise stop surface to limit the clockwise and counterclockwise rotation of the secure-release wheel. 
         [0027]    A wheel assembly spring has a first end connected to a spring securing aperture located on a protruding flange portion of the secure-release wheel. The wheel assembly spring has a second end which connects to a spring securing aperture located in a flange positioned above the bushing in the aft of the wheel housing. 
         [0028]    A pair of release springs are compressed between the front end of the wheel slider and a wheel stop. A pair of shoulder screws, which extend through the wheel stop, the release springs and the front of the wheel slider, are screwed into the wheel housing. 
         [0029]    A flange provided on a lateral side of the wheel housing is used to mount a microswitch. The microswitch is provided with a bent leaf actuator. When a missile is loaded onto the launch rail, the trigger is placed is a latched position which causes the connected rod to move forward such that the lock link and wheel lock are moved forward such that the front section of the wheel lock fits into the wheel notch stop surface of the secure-release wheel. When a missile is launched the connected rod is pulled to the rear and the microswitch pin presses against the bent leaf actuator which presses the contact of the microswitch which sends a signal that the secure-release mechanism of the present invention is in the unlatched state. 
         [0030]    The present invention is able to retain the load along the missile&#39;s axis and provides a blast-enabled detent release of the missile from a launch rail while greatly reducing the energy input into the launcher and the airframe of an aircraft. 
         [0031]    The wheel assembly of the present invention automatically secures a missile as it is loaded on to a launch rail. The wheel assembly includes an asymmetrical secure-release wheel having a plurality of defined surfaces which are positioned radially outward from a pivot hole through which a pivot pin extends. A microswitch which is mechanically connected to the wheel assembly notifies launcher electronics if the detent surface of the wheel assembly is in a latched or unlatched state. 
         [0032]    Upon firing the missile, the exhaust blast from the missile motor hits the trigger, causing the trigger to rotate counter-clockwise out of the propellant plume. This rotational motion is transferred to lateral motion in the connecting rod by the action of the cam surface on the trigger. The connecting rod pulls the lock backward out of the wheel, allowing the wheel to rotate freely, thus releasing the missile to travel freely down the launch rail. When the connecting rod is pulled back, the lock link is disengaged from the secure-release wheel thereby allowing the microswitch pin to contact the microswitch. When the pin-microswitch connection is made, launcher electronics are able to determine an unlatched state. 
         [0033]    The present invention is robust enough to withstand the retention force imparted by the missile along the launch axis. This force is roughly equivalent to a 6G retention capacity for the Hellfire missile under all conditions except for during launching of the missile. 
         [0034]    The present invention may also act as a spring-override detent. The missile may push the secure-release wheel forward off of the wheel lock should any event occur such that the trigger fails to release the secure-release wheel. The secure-release wheel is mounted upon a wheel slider connected to release springs such that when the missile pushes upon the secure-release wheel, the wheel slider moves forward and away from the wheel lock, compressing two compression springs, and allowing the secure-release wheel to rotate. 
         [0035]    An additional design feature of the present invention is that the mechanism automatically locks when a missile is loaded onto the launch rail. When the missile slides down the rail towards the loaded position, the missile contacts the wheel and causes the wheel to rotate around until the lock can slide into position. The spring in the trigger assembly forces the connecting rod and lock into a notch in the wheel, preventing the wheel from rotating. 
         [0036]    When the lock is in position in the wheel, a pin no longer contacts the microswitch causing the switch to be open. The launcher electronics are able to determine that the secure-release mechanism is in the latched state. 
         [0037]    Also, the trigger of the trigger assembly is able to rotate 180 degrees such that the trigger can be pointed up. This allows the secure-release mechanism to be placed flat on a horizontal surface for storage while protecting the trigger from damage. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0038]    A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. 
           [0039]      FIG. 1  is a sectional side view of a prior art HYDRA  70  rocket launcher blast-activated detent mechanism. 
           [0040]      FIG. 2  is sectional side view of a prior art Hellfire missile launcher spring-override detent mechanism. 
           [0041]      FIG. 3  is a partially exploded, perspective view showing the orientation of the missile secure-release assembly of the present invention in relation to a launch rail and missile. 
           [0042]      FIG. 4  is an exploded view of the wheel assembly section of the present invention. 
           [0043]      FIG. 5  is an exploded view of the trigger assembly section of the present invention. 
           [0044]      FIG. 6  is a side-view of the secure-release wheel of the present invention. 
           [0045]      FIG. 7  is a sectional side-view of the wheel assembly section of the present invention with the microswitch removed. 
           [0046]      FIG. 8  is a sectional side-view showing the microswitch in relation to the microswitch pin and secure-release wheel of the present invention in a latched state. 
           [0047]      FIG. 9  is a close-up, sectional side-view schematic drawing of the wheel assembly section of the present invention with the microswitch removed and demonstrates the secure-release wheel latching to a missile shoe as the missile is loaded on the launch rail. 
           [0048]      FIG. 10  is a sectional side-view schematic drawing of the trigger assembly of the present invention demonstrating the trigger being acted upon by the blast of the missile so as to move connecting rod  52  aft. 
           [0049]      FIG. 11  is a side-view, schematic drawing of the trigger assembly  66  of the present invention in an unlatched position. 
           [0050]      FIG. 12  is a side-view, schematic drawing of the trigger assembly  66  of the present invention in the stowed position. 
           [0051]      FIG. 13  is a side-view, schematic drawing of the trigger assembly  66  of the present invention in the latched position. 
           [0052]      FIG. 14  is a side-view, schematic drawing of the trigger assembly  66  in the ready-to-load position. 
           [0053]      FIG. 15  is a bottom view of the wheel assembly and microswitch when the secure-release mechanism of the present invention is in a latched state. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0054]    Reference is now made to the drawings wherein like numbers represent like parts in each of the several figures. 
         [0055]    In  FIG. 3 , a securing-releasing mechanism  50  is provided with a trigger assembly  66  and a wheel assembly  54  which are connected by connecting rod  52 . The trigger assembly  66  and the wheel assembly  54  are secured to the launch rail  58 . The connecting rod  52  is held in position above the launch rail  58  by lubricated rod guide  64 . The wheel assembly  54  is protected from the environment by a cover  62 . When missile  60  is loaded onto the rail  58 , the wheel assembly  54  securely retains the missile  60  on the rail  58  until the missile is launched. 
         [0056]    In  FIG. 4 , a secure-release wheel  70  is mounted to wheel slider  76  by wheel pivot pin  74 . The slider pin  90  is inserted into the wheel slider  76  such that the rotational position of the wheel  70  is limited in either rotational direction by slider pin  90 . The wheel slider  76  is inserted into the forward end of the wheel housing  72 . 
         [0057]    Safety release springs  92 A,  92 B are compressed onto the wheel slider  76  by the wheel stop  94 , so as to hold the wheel slider  76  firmly in place in the wheel housing  72 . The wheel housing  72  is provided with a flange  88  for mounting microswitch  56 . The wheel stop  94  is mounted and secured to the wheel housing  72 , through holes in the wheel slider  76 , by shoulder screws  96 A,  96 B. The compressive force on the safety release springs  92  is determined by the number of washers used underneath the shoulder screws  96 A,  96 B that mount the wheel stop  94 . Launch rail  58  contains an aperture  63  ( FIG. 3 ) which allows secure-release wheel  70  to make contact with missile middle shoe  68 . Secure-release wheel  70  is latchable to the middle shoe  68  of missile  60 . 
         [0058]    A first end  82 A of wheel extension spring  82  is attached to the wheel  70  at wheel spring mount  70 J. A second end  82 B of spring  82  is attached to spring mount  72 A of wheel housing  72 . Spring  82  provides the force that pushes the wheel  70  into the unlatched position prior to a missile being load on the launch rail. Wheel lock  78  mounts inside the raceway in the wheel housing  72  and fits into the like-shaped notch in the wheel  70 . The lock bearings  84  are attached on both sides of the wheel lock  78  and roll along the raceway  95  in the wheel housing  72 . 
         [0059]    The microswitch pin  86  is attached to the wheel lock  78  and acts upon the microswitch  56  as the wheel lock  78  moves fore and aft. The wheel lock  78  is connected to lock link  80 , which attaches to the rear  79  of the wheel lock  78  while fitting through the bushing  89  in the wheel housing  72 . The missile launcher electronics are able to determine that the detent is in the unlatched state. 
         [0060]    With reference to  FIG. 5 , the trigger  110  is mounted to the aft end of the trigger rod  104  by the trigger pivot pin  108 . The trigger rod  104  is held in position by mounting through the bushing in the trigger housing  102  and through the slot in the trigger plate  106 . The trigger spring  100  mounts against the trigger housing  102  and pushes upon the spring stop  98 . The spring stop is mounted securely to the forward end of the trigger rod  104 . The compressive force on the trigger spring  100  is determined by the geometry of the assembled parts and the position of the trigger  110  on the trigger plate  106 . The action of the trigger spring  100  keeps the trigger  110  pushed firmly against the trigger plate  106  under all rotational positions. 
         [0061]    As demonstrated in  FIG. 6 , the wheel  70  has many surfaces which interact with other parts in the wheel assembly  54 . The wheel notch leading edge  70 A slides against the wheel lock  78  as the wheel  70  rotates. The rotation of the wheel is restricted between the counter-clockwise stop surface  70 B and the clockwise stop surface  70 C when they contact the slider pin  90 . The wheel notch stop surface  70 D stops the forward axial movement of wheel lock  78 . The wheel notch lock surface  70 E rests against the wheel lock  78  when the secure-release mechanism  50  of the present invention is in the latched position. The wheel latch leading edge  70 F contacts the missile middle shoe  68  when loading the missile  60 . The wheel detent surface  70 G contacts the missile middle shoe  68  when the missile  60  has been loaded onto the rail  58 . The wheel un-latched surface  70 H contacts the wheel lock  78  when the detent is in the unlatched position. The wheel spring mount  70 J attaches the wheel extension spring  82  to the wheel. The wheel pivot hole  70 K is where the wheel pivot pin  74  slides through, mounting the wheel  70  to the wheel slider  76 . 
         [0062]    With respect to  FIG. 7 , before the missile  60  is fired, the wheel  70  holds the missile  60  on the launch rail by capturing the missile middle shoe  68  between the wheel detent surface  70 G and the rail missile stops  20 . The missile middle shoe  68  is kept firmly pushed against the wheel detent surface  70 G by the interaction of the missile  60  and the springs on the connectors which electrically join the missile to the launcher electronics. The wheel  70  is prevented from rotating counter-clockwise by the slider pin  90 . 
         [0063]    When the missile  60  is fired, the forward thrust  114  of the missile  60  pushes the missile middle shoe  68  of the missile  60  against the wheel detent surface  70 G of the wheel  70 . This force acts to force the wheel  70  to rotate clockwise. As the wheel notch lock surface  70 E contacts the wheel lock  78 , it puts a normal force against the wheel lock  78 , preventing the wheel  70  from rotating. 
         [0064]    At the same time, through the interaction of the trigger assembly  66  and the missile motor plume, the connecting rod  104  is pulled in the aft direction  112 . The force pulling the connecting rod  104  from the trigger assembly  66  must overcome the friction force holding the wheel lock  78  in place under the notch in the wheel  70  against the wheel notch lock surface  70 E. To mitigate this friction force, the wheel lock has bearings  84  on either side to roll in the raceway of the wheel housing  72 . 
         [0065]    Upon ignition of the missile motor, the rocket exhaust gases, i.e., the rocket plume, cause unbalanced forces through the trigger assembly  66  and impart enough force to pull the connecting rod  104  and overcome the friction force holding the wheel lock  78  in place. This pulls the wheel lock  78  out from under the wheel  70 , allowing the wheel  70  to rotate clockwise. The wheel extension spring  82  also acts to rotate the wheel  70  clockwise. 
         [0066]    Once wheel notch leading edge  70 A contacts the front section  78 F of the wheel lock  78 , the rotational force on the wheel  70  imparted by the missile  60  acts to push the wheel lock  78  and connecting rod  52  aft. 
         [0067]    After the wheel lock  78  has moved sufficiently aft, the wheel  70  is completely free to rotate out of the way of the mid rail shoe of the missile  60 . The wheel  70  will rotate clockwise until it again contacts the slider pin  90 . At this point, the wheel  70  is now in the ready-to-load position. 
         [0068]    The entire process from missile firing to release of the wheel  70  to freely rotate happens in the first 10-20 milliseconds after ignition of the missile motor. The missile  60  is released faster than the force of the missile motor can ramp up, and much faster than the current spring-override detent in the missile rail, shown in  FIG. 2 . By significantly reducing the time the detent holds the missile on the rail after launch, the total energy put into the launcher from the missile is significantly reduced. This reduces the total displacement of the launcher during the launch process. The overall effect is to greatly reduce the chance of an errant missile after launch. On certain aircraft, an errant missile can be caused by interaction of the missile  60  and the rail  58  after the missile  60  leaves the rail  58  as the launcher springs back to its initial position before launch. 
         [0069]    Should some circumstance occur where the trigger assembly  66  fails to pull the connecting rod  52  and the wheel lock  78  out from under the wheel  70 , the present invention can still function as a spring-override detent mechanism. The wheel  70 , being mounted to the wheel slider  76 , can move horizontally forward inside the wheel housing  72  if enough force is applied to overcome the compressive force of the safety release springs  92 A,  92 B. The safety release springs  92 A,  92 B are pre-loaded to approximately 200 lbs of compression each. 
         [0070]    After the missile thrust ramps up to at least  720  lbs of thrust, the missile  60  will force the wheel  70  forward off of the wheel lock  78 . During assembly of the wheel assembly  106 , the spring-override function of the present invention is tested and adjusted such that the force required to release the missile  60  under thrust will be within  630  lbs and  700  lbs of force along the missile thrust vector. This is done by adjusting the number of washers under the shoulder screws  96  that locate the position of the wheel stop  94  relative to the wheel housing  72 . 
         [0071]    When the wheel  70  and wheel slider  76  slide forward against the safety release springs  92 A,  92 B far enough, the wheel notch leading edge  70 A in the wheel  70  contacts the sloped surface of the wheel lock  78 A. The rotational force on the wheel  70  imparted by the missile  60  acts to push the wheel lock  78  and connecting rod  104  aft. Alternately, should the wheel lock be unable to move, the wheel  70  can continue to move forward relative to the wheel housing  70 . This will also allow the wheel  70  to rotate far enough clockwise to allow the missile  60  to depart the rail  58 . While the spring-override function provides no benefit over the current spring-override detent, shown in  FIG. 2 , with respect to the total energy imparted into the launcher during launch, it does greatly reduce the probability of a hangfire event occurring due a failure in the detent mechanism. 
         [0072]    Referring now to  FIG. 8 , the secure-release mechanism is in a latched state; thus, the microswitch  56  is positioned such that the bent leaf actuator  56 A does not make contact with the microswitch contact  56 B. When the detent surface  70 G is in the latched position, the microswitch pin  86  does not contact the bent leaf actuator  56 A. 
         [0073]    However, during the launch of a missile  60 , the wheel lock  78  is pulled aft and away from under the wheel  70 . The microswitch pin  86  is attached to the wheel lock  78 . As the microswitch pin  86  moves aft, it contacts the bent leaf actuator  56 A. When the wheel notch leading edge  70 A in the wheel  70  is approximately  70 % of the way down the sloped front surface  78 F of the wheel lock  78 , the bent leaf actuator  56 A will contact and depress the microswitch contact  56 B. With the microswitch  56  activated, the launcher electronics knows that the secure-release mechanism is in the unlatched state. Through the maximum aft displacement of the wheel lock  78 , the microswitch pin  86  keeps the microswitch  56  activated. The microswitch contact  56 B is only released when the wheel lock  78  approaches the latched position after loading a missile  60  on the rail  58 , (see  FIGS. 8 and 15 ). 
         [0074]    As demonstrated in  FIG. 9 , when the missile  60  is loaded onto the rail  58 , the missile middle shoe  68  engages with the wheel  70  and automatically latches the detent. When the trigger assembly  66  is in the ready-to-latch state, the trigger compression spring  100  applies force through the connecting rod  104  to the wheel lock  78 . The wheel lock  78  rests against the wheel unlatched surface  70 H of the wheel  70 , keeping the trigger  110  hanging down loosely from the trigger assembly  66 . The wheel extension spring  82  holds the wheel  70  firmly against the slider pin  90 , putting the present invention into the ready-to-latch state. 
         [0075]    As the missile  60  is loaded onto the rail  58 , the missile middle shoe  68  slides down slots in the rail  12 A until the missile middle shoe latch surface  68 B contacts the wheel latch leading edge  70 F on the wheel  70 . As the missile  60  slides aft, the missile middle shoe  68  causes the wheel  70  to rotate counter-clockwise until the wheel lock  78  is able to slide into place in the notch in the wheel  70 . 
         [0076]    The trigger compression spring  100  in the trigger assembly  66  forces the wheel lock  78  to seat firmly and remain in the wheel notch which causes the trigger  110  to snap tightly against the trigger plate  106  in the trigger assembly  66 . This causes a loud banging sound that gives an auditory indication that latching has occurred. The missile middle shoe detent surface  68 A is now in contact with the wheel detent surface  70 G. At this point the missile  60  is fully retained by the wheel assembly  54 . 
         [0077]    With reference to  FIG. 10 , when the missile  60  is loaded on the launch rail  58 , the nozzle of the motor section of the missile  60  sits about  1  inch from the forward face of the trigger  110 . This is the latched position for the trigger  110 . When the missile  60  ignites, the missile motor plume exits the nozzle and creates a partial pressure force  116  on the trigger  110  in the direction of the motor section exhaust. This force causes the trigger  110  to rotate counter-clockwise around the trigger pivot pin  108 . The cam surface on the trigger  110 A contacts the trigger plate  106  and causes the trigger rod  104  to move aft as the trigger  110  rotates counter-clockwise. The trigger compression spring  100  keeps the trigger  110  tight against the trigger plate  106  throughout the rotation around the trigger pivot pin  108 . The fore and aft motion of the trigger rod  104 , by way of the connecting rod  104 , causes the wheel lock  78  to pull out of and push back into the wheel  70 . 
         [0078]    Referring now to  FIGS. 11-14  and  FIG. 5 , the trigger  110  has four primary positions. As shown in  FIG. 14 , with the trigger  110  tight against the trigger plate  106  and hanging down vertically from the trigger pivot pin  108 , the trigger  110  is in the latched position. As the trigger  110  rotates counter-clockwise towards horizontal, it trigger cam surface creates an over-center displacement of the trigger rod  104 . 
         [0079]    By the time the trigger  110  becomes horizontal, the trigger compression spring  100  will push the trigger rod  104  back forward and keep the trigger  110  tight against the trigger plate  106 . By way of  FIG. 11 , this is the unlatched position. If the trigger  110  is rotated further around counter-clockwise, it will pass another over-center position and come to rest tight against the trigger plate  106  with the trigger  110  sitting vertically upwards from the trigger pivot pin  108 . As seen in  FIG. 12 , this is the stowed position. 
         [0080]    From the unlatched position, if the trigger  110  is rotated clockwise, the trigger rod  104  will push the wheel lock  78  against the wheel  70  in the un-notched area of the wheel  70 . This will cause the trigger  110  to hang down vertically, as in the latched position, but not tight against the trigger plate  106 . As demonstrated in  FIG. 13 , this is the ready-to-latch position. 
         [0081]    The trigger  110  is prevented from rotating clockwise from the latched position by mechanical interference between the trigger  110  and the trigger rod  104 . The trigger is prevented from rotating counter-clockwise from the stowed position more than  20  degrees by the trigger stop  98  contacting the trigger housing  102 . The trigger rod is prevented from sliding aft more than 0.625 inches by the trigger stop  98  contacting the trigger housing  102 . 
         [0082]    In that the blast-enabled secure-release mechanism embodied by the present invention has a much reduced energy impulse applied to the launcher from the missile during a launch event, the probability of an errant missile phenomena is greatly reduced by the present invention. Further, as the present invention encompasses automatic latching when loading a missile, the ease of operation of the missile launcher has been significantly enhanced. 
         [0083]    By utilizing a stowed position for the trigger, the ease of the launcher to be stored has not been negatively impacted by the present invention. Additionally, the present invention meets or exceeds all the same performance requirements of prior art Hellfire rail detent mechanisms while keeping the probability of a hangfire event extremely remote. 
         [0084]    It is understood that modifications to the present invention may be made by those skilled in the art without departing from spirit of the foregoing disclosure and the scope of the following claims.