M1156 Precision Guidance Kit

The M1156 Precision Guidance Kit (PGK), formerly XM1156, is a U.S. Army-designed precision guidance system to turn existing 155 mm artillery shells into smart weapons.[2] The prime contractor was Alliant Techsystems – later merging with Orbital Sciences Corporation to form Orbital ATK, in turn being taken over by Northrop Grumman and renamed Northrop Grumman Innovation Systems – and the industry team includes Interstate Electronics Corporation.[3] By April 2018, more than 25,000 PGKs had been produced.[4]

M1156 Precision Guidance Kit
Diagram of XM1156 alongside standard fuse profile
TypeGPS-guided artillery fuze kit
Place of originUnited States
Service history
In serviceSince 2015
Used by
Production history
DesignerAlliant Techsystems
Designed2007–2013
ManufacturerNorthrop Grumman Innovation Systems
Unit costUS $13,541[note 1]
ProducedSince 2013
No. builtOver 100,000[note 2]
Specifications
Length
  • 8.67 in (220.2 mm) overall
  • 3.75 in (95.25 mm) visible
  • 4.91 in (124.7 mm) intrusion
Detonation
mechanism
Impact and proximity-detonation functions
Guidance
system
GPS
Steering
system
Four fixed canards
AccuracyCEP of less-than 30 m (98 ft)[note 3]
Launch
platform
ReferencesJanes[1]

Overview
Setting the fuze

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,[5] but was ultimately fielded in spring 2013.[6]

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 half of the 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.[7][8]

Small aerodynamic fins allow 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.[7][8] The PGK fuze weighs 3 lb (1.4 kg), 1 lb (0.45 kg) more than a standard fuze because of the addition of fins and an alternator. The self-contained system does not need a battery since the alternator inside generates power in flight. Not only is the PGK fuze cheaper to produce than whole purpose-built guided artillery shells, its purpose to turn standard shells into more accurate rounds enables the millions of rounds already in inventories to be upgraded, while new smart shells have to be built to create a stockpile.[9]

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.

Program timeline
  • June 2006: Raytheon removed 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.[10]
  • October 2012: Soldiers from Fort Bliss became the first troops to fire the XM1156 guidance kit. 24 PGK-equipped projectiles were fired.[6]

Trials

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.[11]

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.[12] By mid-2016, 4,779 PGK fuses had been produced under the low-rate initial production contract, with full-rate production commencing through 2019.[13]

Variants
XM1113 extended range artillery round, shown here at a range demonstration, uses a rocket-assist motor

In 2021, the U.S. Army plans to produce the upgraded M1156E2/A1, compatible with newer XM1128 high explosive and XM1113 rocket-assisted projectiles to achieve 10-meter accuracy at 30 km and 40 km respectively when fired from a 39-caliber barrel. The follow-on M1156E3/A2 in 2022 will be designed to operate with the GPS-M satellite constellation along with having a cheaper electronic module. After that, a new version known as the Long Range PGK will enable accuracy with XM1113 projectiles out to 70 km when fired from 58-caliber barrels of artillery pieces developed from the Extended Range Cannon Artillery (ERCA) program, as well as being compatible with legacy projectiles and being able to operate in a near-peer GPS threat environment.[14]

Export

On 8 August 2013, Australia requested the sale of 4,002 M1156 Precision Guidance Kits with training and associated equipment for $54 million,[15] something unusual for an item still in low-rate initial production.[16] PGKs were ordered for Australia and Canada in February 2015.[17] Australia is to begin receiving PGKs in the December 2015-January 2016 timeframe.[18] On 24 April 2018, the US Defense Security Cooperation Agency approved the foreign military sale of 3,500 M1156 kits to the Netherlands at an estimated cost of US$70 million.[19]

Deployment

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. The U.S. Army received 2,400 PGK-equipped shells and the U.S. Marine Corps received 700 shells.[7][8]

Specifications

See also

Footnotes
  1. Price per unit in the 2013 fiscal year. That price was expected to fall as production increased.[1]
  2. According to Northrop Grumman, as of September 2022 over 100,000 PGKs had been produced and delivered.[1]
  3. A majority of rounds attained a CEP of 10 m (33 ft) during the 2015 First Article Acceptance Test.[1]

References
  1. Janes (7 February 2023), "Northrop Grumman M1156 Precision Guidance Kit", Janes Land Warfare Weapons: Ammunition, Coulsdon, Surrey: Jane's Group UK Limited., retrieved 6 March 2023
  2. XM1156 Precision Guidance Kit (PGK). Global Security.
  3. "ATK Precision Guidance Kit (PGK)". ATK.
  4. Orbital ATK is expanding to prepare for what they predict will be a surge in DoD buys of more lethal munitions. Defense News. 12 April 2018.
  5. "ATK To Make Precision Artillery Shell - defensenews.com". Archived from the original on 2013-01-21. Retrieved 2007-07-14.
  6. Calloway, Audra (December 13, 2012). "Fort Bliss Soldiers First To Fire Army's New Near-Precision Artillery Rounds". Army.mil.
  7. XM1156 Precision Guidance Kit Heads to Afghanistan - Defensemedianetwork.com, 26 April 2013
  8. Army Ships Precision Guidance Kits to Artillery Units in Afghanistan - Defensetech.org, 10 May 2013
  9. US Army 'Dumb' 155mm Rounds Get Smart - Defensenews.com, 13 March 2015
  10. "ATK Awarded Precision Guidance Kit Contract After Multi-Day Competitive Shoot-Off - ATK". Archived from the original on October 9, 2007.
  11. Army's precision guidance kit achieves new acquisition milestone, demonstrates high reliability - Army.mil, 30 April 2015
  12. Orbital ATK's 155mm Artillery Precision Guidance Kit Meets All Requirements During Test - Armyrecognition.com, 30 June 2015
  13. Orbital ATK Signs $69 Million Contract to Produce Artillery Precision Guidance Kits Through 2019 - Armyrecognition.com, 4 August 2016
  14. US Army: new rounds for 155 mm artillery. European Defence Review. 4 November 2020.
  15. FMS: Australia Requests Precision Guidance Kits for 155mm Munitions - Deagel.com, 12 August 2013
  16. "Army halts mortar buys, looks to trade up". Armytimes.com, 8 November 2013.
  17. Orbital ATK to provide Precision Guidance Kit XM1156 to US, Australia and Canada - Armyrecognition.com, 3 March 2015
  18. Aussie precision munitions en route - Shephardmedia.com, 9 September 2015
  19. "Netherlands – M1156 Precision Guided Kits". Defense Security Cooperation Agency. Washington, D.C.: US Department of Defense. 24 April 2018. Archived from the original on 25 April 2018. Retrieved 3 May 2018.
  20. "Precision Guidance Kit (PGK) Improving the Accuracy of Artillery Fire - Defense Update". Archived from the original on 2017-10-01. Retrieved 2007-07-14.
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