M-32 Submunition (M32 SMART GMLRS Concept)

1. Overview

The M-32 designator refers to a developmental concept for a GMLRS (Guided Multiple Launch Rocket System) rocket variant intended to carry SMArt (Sensor-fuzed Munition for Artillery) anti-tank submunitions. Originating from German-U.S. cooperative development efforts, the M-32 SMART concept represented an advanced approach to precision-delivered, sensor-fuzed anti-armor submunitions within the MLRS family. Unlike earlier DPICM-type submunitions, the M-32 concept employed intelligent submunitions capable of independently detecting and engaging armored targets.

Safety Note: All ordnance should be considered dangerous until proven safe by qualified EOD personnel. Sensor-fuzed submunitions may retain active electronic systems and remain capable of functioning long after deployment. Suspected ordnance should be reported to military or law enforcement authorities.

Note on Source Limitations: The M-32 SMART GMLRS concept exists primarily in developmental and limited-source references. Some technical details remain unconfirmed or may have evolved during the development process. Information presented here represents the best available open-source understanding.

2. Country/Bloc of Origin

  • Countries: Germany (primary SMArt submunition development) in cooperation with the United States (GMLRS platform integration)
  • Era: Late 1990s through 2000s development period
  • Key Developers: GIWS (Gesellschaft für Intelligente Wirksysteme), a German joint venture between Diehl Defence and Rheinmetall, developed the SMArt submunition; Lockheed Martin produced the GMLRS rocket platform
  • NATO Context: Developed within the broader framework of NATO cooperative armament programs

3. Ordnance Class

  • Type: Guided rocket with sensor-fuzed anti-armor submunition payload
  • Role: Anti-armor / anti-vehicle precision area weapon
  • Delivery Method: Ground-launched via the M270 MLRS or M142 HIMARS rocket launcher systems
  • Category: Sensor-fuzed weapon (SFW); a class of munition that uses onboard sensors to autonomously detect and engage targets

4. Ordnance Family / Nomenclature

  • Designation: M-32 (developmental GMLRS variant)
  • Submunition: SMArt 155 (Suchzünder-Munition für die Artillerie, translated as “Sensor-fuzed Munition for Artillery”)—adapted from the 155mm artillery submunition for rocket delivery
  • Related Systems:
    • GMLRS M30 (DPICM variant with M85 submunitions)
    • GMLRS M31 (Unitary high-explosive variant)
    • SMArt 155 artillery round (DM702, used in 155mm artillery projectiles)
  • NATO Context: Part of the broader MLRS family of munitions; the SMArt submunition family is in service with multiple NATO nations in 155mm artillery form

5. Hazards

  • Primary Hazard: Each SMArt submunition contains an explosively formed penetrator (EFP) warhead capable of defeating armored vehicle top armor
  • Sensor Hazard: The submunition incorporates active infrared and millimetric-wave radar sensors that scan the ground during descent. An unfunctioned submunition may retain active sensor capability and could potentially engage a target if disturbed
  • Self-Destruct/Self-Neutralization: SMArt submunitions are designed with self-destruct and self-deactivation features to reduce UXO risk. However, these features cannot be assumed to have functioned correctly in all cases
  • Battery Hazard: The submunition uses an internal battery to power its sensor and guidance systems. Battery degradation over time may result in unpredictable behavior
  • EFP Hazard: The EFP warhead forms a high-velocity copper or tantalum slug upon detonation, capable of penetrating significant armor thickness from stand-off distances
  • UXO Considerations: Even with self-destruct features, unfunctioned SMArt submunitions must be treated as live ordnance. The combination of active sensors and an armed EFP warhead makes these items particularly hazardous

6. Key Identification Features

  • Rocket: Standard GMLRS rocket dimensions—approximately 3.94 m (12 ft 11 in) in length, 227 mm (8.94 in) in diameter
  • Submunition Shape: The SMArt submunition is cylindrical with a distinctive parachute pack and sensor dome
  • Sensor Dome: An infrared/millimetric-wave sensor window is visible on the submunition body
  • Parachute System: Each submunition deploys a small parachute to slow descent and allow the sensor system adequate scan time
  • Payload: The M-32 concept carried four SMArt submunitions per rocket
  • Markings: Standard NATO/German military ammunition markings; specific lot and designation stenciling
  • Rocket Remnants: GMLRS rocket motor casings and fin assemblies found in the field indicate potential submunition deployment in the area

7. Fuzing Mechanisms

  • Fuze Type: Multi-mode sensor fuze combining infrared (IR) imaging and millimetric-wave (MMW) radar
  • Arming Sequence:
    1. The GMLRS rocket is fired from an M270 or M142 launcher using GPS/INS guidance to the target area
    2. At a predetermined point on the trajectory, the rocket warhead section opens and ejects the submunitions
    3. Each submunition deploys a parachute system to slow descent
    4. The submunition begins a slow rotation, allowing its multi-mode sensor to scan the ground below in a spiral pattern
    5. When a target signature consistent with an armored vehicle is detected, the onboard processor calculates optimal engagement geometry
    6. The EFP warhead fires, projecting a penetrator slug downward into the target
  • Self-Destruct: If no target is detected during descent, the self-destruct mechanism is designed to destroy the submunition at a preset time or upon ground impact
  • Self-Deactivation: Battery life limitations provide an additional self-deactivation mechanism—once the battery is depleted, the sensor and firing circuits are rendered inoperable

8. History of Development and Use

  • Origins: The SMArt submunition was developed by GIWS in Germany during the 1990s, initially for the 155mm artillery application (DM702 round). The concept proved highly effective and attracted interest for integration into the GMLRS rocket system
  • M-32 GMLRS Concept: German defense sources proposed an M-32 GMLRS rocket variant carrying four SMArt submunitions per rocket. This would provide MLRS units with a precision anti-armor capability at extended ranges (60+ km) with reduced collateral damage compared to DPICM munitions
  • Development Status: The M-32 SMART GMLRS concept progressed through feasibility and early development but did not reach full-scale production. U.S. policy shifts toward unitary warheads (driven by cluster munition policy concerns and the 2008 DoD policy requiring less than 1% UXO rate) affected the program’s trajectory
  • SMArt 155 Service: While the GMLRS variant remained developmental, the SMArt 155 submunition entered active service in 155mm artillery form with the German Bundeswehr and several other NATO nations. It saw its first combat use in operations in the 2000s
  • Cluster Munition Policy Impact: The 2008 U.S. Department of Defense cluster munition policy, which required all cluster munitions to have less than 1% UXO rate after 2018, favored systems with self-destruct features like SMArt but also increased pressure to develop unitary alternatives
  • Current Status: The M-32 GMLRS SMART concept is not in active production. The GMLRS family continues in service with the M31 unitary variant and the newer GMLRS-ER (Extended Range) and GMLRS-AW (Alternative Warhead) variants

9. Technical Specifications

ParameterSpecification
Rocket DesignationM-32 (developmental)
Rocket Length~3.94 m (12 ft 11 in)
Rocket Diameter227 mm (8.94 in)
Submunition TypeSMArt (Sensor-fuzed anti-armor)
Submunitions per Rocket4
Warhead TypeExplosively Formed Penetrator (EFP)
Sensor SuiteDual-mode IR imaging + millimetric-wave radar
Guidance (Rocket)GPS/INS
Range60+ km (37+ miles)
Launcher PlatformsM270 MLRS, M142 HIMARS
Self-DestructYes (designed)
Self-DeactivationYes (battery depletion)

10. Frequently Asked Questions

Q: What makes the M-32 different from earlier DPICM-type GMLRS rockets? A: Earlier DPICM rockets like the M30 carried hundreds of small, unguided submunitions (M85 bomblets) that relied on simple impact or self-destruct fuzing. The M-32 concept carried only four submunitions, but each was an autonomous sensor-fuzed weapon capable of independently detecting and engaging armored targets with high precision. This represented a shift from quantity-based area saturation to quality-based precision engagement.

Q: What is an Explosively Formed Penetrator (EFP)? A: An EFP is a warhead that uses explosive force to reshape a metal liner (typically copper or tantalum) into a high-velocity penetrating slug. Unlike a conventional shaped-charge jet, an EFP forms a solid projectile that maintains its penetrating ability at much greater stand-off distances—up to 100 meters or more. This allows submunitions to engage armored targets from significant altitude during descent.

Q: How does SMArt compare to the U.S. BLU-108 sensor-fuzed submunition? A: Both are sensor-fuzed anti-armor submunitions that use IR sensors and EFP warheads to engage armored targets. The BLU-108 (used in CBU-97/CBU-105) carries four smaller “skeet” submunitions and uses a rocket motor to gain altitude before deployment. The SMArt submunition is a single, larger unit with a dual-mode IR/MMW sensor package, generally considered to have more advanced target discrimination capabilities.

Q: Why didn’t the M-32 GMLRS enter production? A: Several factors contributed, including U.S. policy shifts favoring unitary warheads over cluster-type munitions, the high cost of sensor-fuzed submunitions compared to alternatives, and the proven effectiveness of the GPS-guided GMLRS unitary variant (M31) in combat operations. Budget constraints and evolving operational requirements also played a role.

Q: Are SMArt submunitions still dangerous as UXO? A: Yes. Despite self-destruct and self-deactivation features, unfunctioned SMArt submunitions must be treated as live ordnance. The combination of an armed EFP warhead and potentially active sensor systems makes them hazardous. Battery degradation may result in partial functionality, creating an unpredictable threat.

Q: Which countries use SMArt submunitions? A: The SMArt 155 is in service with Germany, Switzerland, Greece, and Australia, among others, in its 155mm artillery form. The GMLRS rocket variant (M-32) did not reach widespread production or fielding.

Q: How does sensor-fuzed technology reduce civilian harm compared to DPICM? A: Sensor-fuzed submunitions are designed to engage only targets matching specific sensor signatures (armored vehicles), significantly reducing the indiscriminate area effect of traditional DPICM. Self-destruct and self-deactivation features further reduce the post-conflict UXO hazard. However, sensor failures and battery malfunctions can still result in unexploded items, so the risk is reduced but not eliminated.