XM1156 Precision Guidance Kit
The XM1156 Precision Guidance Kit is a U.S. Army program to develop a precision guidance system for existing 155 mm artillery shells. The prime contractor is Alliant Techsystems and the industry team includes Interstate Electronics Corporation.
In operation the PGK screws into the nose of the projectile much like conventional fuzes. In addition to the fuzing function it provides a GPS guidance package and control surfaces to correct the flight of the shell. This is analogous to the addition of a Joint Direct Attack Munition (JDAM) tail-kit to a dumb iron bomb, creating a precision guided munition. The system began production in 2009, was first expected to be in service by 2010, but later was fielded in spring 2013.
A conventional unguided M549A1 155 mm artillery projectile has a circular error probability (CEP) of 267 m (876 ft) at its maximum range, meaning that rounds can be expected to land within 267 meters of their intended target. This has made unguided artillery dangerous to use in close combat for fear of friendly fire and collateral damage. The M982 Excalibur was fielded as a guided shell that effectively hit within 6 m (20 ft) of a target, but the Army developed the XM1156 as a cheaper alternative. The PGK fuse can be screwed onto existing M549A1 and M795 projectiles, be fired from M109A6 Paladin and M777A2 Howitzer artillery systems, and hits within 50 m (160 ft) of the target at any range.
Small aerodynamic fins pop out of the system to steer the shell on target. Its GPS receiver compares the PGK's flight pattern to the coordinates of where it should hit, and the fins adjust its path to match where the round will actually impact. A fail safe exists where if the shell does not impact within 150 m (490 ft) of the intended target, it will land but not explode; the PGK "decides" five seconds after launch whether it expects to impact close enough to detonate. This safety feature is expected to give soldiers more confidence when calling in artillery support close to their position.
The PGK is compatible with various 155 mm artillery stockpiles to reduce dispersion. It was demonstrated on German DM111 shells in September 2014 fired from a PzH2000 self-propelled howitzer. From a distance of 27 km (17 mi), 90 percent of the PGK-equipped German shells landed within 5 meters of the target.
- June 2006: Raytheon downselected from XM1156 competition.
- July 2006: BAE Systems and Alliant Techsystems selected to take part in a competitive Technical Development (TD) program.
- May 2007: System Demonstration and Development (SDD) contract awarded to Alliant Techsystems.
- October 2012: Soldiers from Fort Bliss became the first troops to fire the XM1156 guidance kit. 24 PGK-equipped projectiles were fired.
On 8 August 2013, Australia requested the sale of 4,002 M1156 Precision Guidance Kits with training and associated equipment for $54 million. PGKs were ordered for Australia and Canada in February 2015.
In March 2013, the 15th Field Artillery Regiment in Afghanistan began training on equipment related to the XM1156, and began fielding PGK rounds shortly after, with initial fielding completed by the end of June 2013. The U.S. Army received 2,400 PGK-equipped shells and the U.S. Marine Corps received 700 shells.
Following fielding in Afghanistan under an urgent materiel release, the PGK underwent First Article Acceptance Tests to verify performance, reliability, and safety. During tests, PGK-fuzed rounds had consistent performance across towed and self-propelled artillery platforms, passing the accuracy objective requirement of 30 m (98 ft) or less CEP with a majority of rounds being placed within 10 m (33 ft). On 6 February 2015, ATK announced that the PGK had passed acceptance testing and been approved for low-rate initial production (LRIP).
In April 2015, the PGK completed a first Production Lot Acceptance Test to assess the reliability and provide acceptance of the first low rate initial production lot. 41 out of 42 PGK rounds fired from an M109A6 Paladin performed reliably, a 97 percent success rate. Two more Lot Acceptance Tests were scheduled for May and June, which will support a full-rate production (FRP) decision by the end of 2015.
On 29 June 2015, Orbital ATK announced that the PGK had completed its first production Lot Acceptance Test, demonstrating a median accuracy of less than 10 meters and passing all safety and reliability requirements. Two additional Lot Acceptance Tests are to confirm production consistency and provide information for product improvements over the course of production.
- Guidance: GPS
- Unit cost: < $3,000
- Fusing options: Point detonating or proximity airburst
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- FMS: Australia Requests Precision Guidance Kits for 155mm Munitions - Deagel.com, 12 August 2013
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- Army's precision guidance kit achieves new acquisition milestone, demonstrates high reliability - Army.mil, 30 April 2015
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- Army munitions officials eye pending developments - Aviation Week