GBU-39 SDB.

Technical Data

• Design

  The design of the GBU‑39 centers on aerodynamic efficiency, compact form factor, and modular integration. The weapon measures approximately 1.8 meters (71 inches) in length, with a body diameter of 190 millimeters (7.5 inches). Its deployable wing kit, made from graphite-epoxy composite, extends after release to a wingspan of 1.5 meters (59 inches), providing the necessary lift and stability to glide for distances exceeding 110 kilometers (68 miles) when released from high altitude.

  The bomb's structural core is fabricated from high-strength steel for durability, while composite elements contribute to weight savings and radar cross-section reduction. The four tail fins, located at the rear of the bomb, are controlled by an internal electromechanical actuation system powered by a thermal battery. These fins provide precise maneuverability and flight correction throughout the munition’s glide profile. Internally, the munition houses sealed compartments for avionics, the guidance suite, warhead, and power systems. The overall layout supports high survivability under high-G release conditions and provides excellent compatibility with the BRU-61/A quad launcher.

  The entire weapon is designed for modularity and carriage efficiency. Its shape and fin layout allow multiple GBU‑39s to be packed into internal bays of stealth aircraft or externally mounted on legacy fighters, making it adaptable across virtually all tactical and strategic air platforms in U.S. and NATO inventories.

• Warheads

  The standard warhead of the GBU‑39B SDB is a 93-kilogram (203-pound) steel-cased, penetrating blast-fragmentation warhead. It is engineered to defeat hardened fixed structures, including command bunkers, aircraft shelters, and fortified storage sites. It uses a delayed-action fuze that allows it to penetrate more than 1 meter (about 3 feet) of reinforced concrete before detonation, ensuring maximum damage within protected structures.

  For operations in urban environments or where collateral damage must be minimized, the GBU‑39A/B FLM variant replaces the steel casing with a carbon-fiber composite shell and fills the bomb with Dense Inert Metal Explosive (DIME). This explosive composition delivers a powerful localized blast with sharply limited fragmentation, significantly reducing unintended damage to nearby personnel or infrastructure. The FLM variant is particularly valued for counterinsurgency, counterterrorism, and precision-strike operations near civilian areas.

  Both warhead types are modular and interface directly with the guidance and control systems, enabling mission-specific configuration of explosive effects without altering the overall bomb geometry or aerodynamic characteristics.

• Guidance Systems

  The GBU‑39 SDB utilizes a sophisticated GPS-aided Inertial Navigation System (INS) that combines a Honeywell HG1700 ring-laser gyroscope Inertial Measurement Unit (IMU) with a Rockwell Collins SAASM-enabled NavStrike GPS receiver. This configuration allows the munition to maintain precise targeting in both permissive and contested electromagnetic environments, including GPS-degraded or GPS-denied zones.

  What sets the GBU-39’s guidance apart from traditional JDAMs is its adaptive flight path correction algorithm, which continually monitors the bomb’s real-time position and velocity using inertial data. These inputs are compared to GPS readings, and discrepancies are used to dynamically adjust fin movements in-flight. This ensures a highly accurate terminal trajectory and mitigates the risk of drift-induced miss distance, especially at extended ranges beyond 100 kilometers (62 miles).

  The system’s SAASM integration enables the bomb to use encrypted military GPS signals that are hardened against spoofing and jamming. Should GPS be disrupted, the weapon will revert to inertial-only guidance, which still offers high accuracy over shorter ranges. Additionally, during the final glide phase, the munition performs a vector correction maneuver to ensure it impacts the target at an optimal angle for penetration. These features combine to deliver a combat-proven circular error probable (CEP) of less than 5 meters, even in challenging operational environments.

• Launcher and Combat Use

  The GBU‑39 SDB is launched from the BRU-61/A smart carriage system, a quad-pack launcher capable of holding four bombs in a streamlined, compact configuration. Each munition is mounted in an individual bay within the rack, with separate power and datalink interfaces for independent targeting. The BRU-61/A uses pneumatic ejection to minimize signature and improve reliability under high-G maneuvering conditions.

  The launcher is certified for use on a wide range of tactical fighters and bombers, including the F-15E Strike Eagle, F-16C/D Fighting Falcon, F-22A Raptor, and all variants of the F-35 Lightning II. It is also carried by long-range bombers such as the B-1B Lancer, B-2A Spirit, and B-52H Stratofortress. Some experimental test configurations have examined integration on unmanned platforms such as the MQ-9 Reaper.

  Before launch, the munition is programmed with its target coordinates via the aircraft’s mission computer. Upon release, the bomb deploys its wings, stabilizes in flight, and follows a GPS-aided inertial trajectory toward the designated target. The munition can adjust for environmental variables such as wind drift and minor navigational errors, ensuring terminal precision even at maximum range. This standoff capability enables aircraft to engage protected targets without entering high-risk zones dominated by enemy air defenses.