M712 Copperhead
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The M712 "Copperhead" is a 155 mm cannon-launched, fin-stabilized, terminally optically guided, explosive projectile intended to engage hard point targets such as tanks, SP howitzers or other high-value targets. It may be fired from the following US Army field artillery weapons: M114A2 towed howitzers, and both the short-barrel (M109A1 and M109A1B) and long-barrel (M109A2, M109A3, M109A3B, M109A4, M109A5 and M109A6) M109 howitzer series SP howitzers and the M198 towed howitzer. The projectile has a minimum range of 3km and a maximum range of 16km. It is no longer in production.
In order for Copperhead to function, the target must be illuminated with a laser. Once the laser signal is detected, the on-board guidance system will operate the steering vanes to maneuver the projectile onto the target. The Copperhead targeting logic is designed to (1) ensure that the optical system will always be able to detect the target, and (2) that once the target has been detected there will be sufficient time and velocity to maneuver to hit the target. Copperhead must be below any cloud cover at critical parts of the trajectory, and there must be sufficient visibility to ensure that when the target is acquired the projectile will have sufficient time to maneuver.
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[edit] Modes of operation
Copperhead has two modes of operation: Ballistic mode and glide mode. Ballistic mode is used where the cloud ceiling is high and visibility is good. Ballistic mode trajectory is simulated using a point-mass trajectory model. When the projectile is 3000 meters from the target, the guidance vanes extend, the target is acquired, and then the on-board guidance system adjusts the guidance vanes to maneuver onto the target.
Glide mode is used when the cloud ceiling and/or the visibility is too low to permit the use of the ballistic mode. A glide mode trajectory consists of two phases: A ballistic phase and a glide phase. The first phase is simulated exactly as in the ballistic mode. At a predetermined point along the trajectory, the guidance vanes extend and there is a transition from ballistic phase to glide phase; the glide phase is simulated using a modified point-mass model. Glide phase targeting logic is designed to ensure the largest possible angle of fall permitted by the cloud cover and the visibility. The target is acquired when the projectile is close enough to detect the laser illumination or when the projectile emerges from the cloud cover, which ever event occurs later in the trajectory. When a trajectory solution has been obtained, time-to-target and terminal velocity are checked to ensure that there will be enough time to maneuver and that the projectile is aerodynamically stable - that it will not stall while maneuvering.
[edit] Combat history
Copperhead was used in Desert Storm.[1]
