GLSDB is a combination of M26 rocket and GBU-39 small diameter bomb jointly produced by Boeing and Saab.

Ukraine is looking forward to Ground Launched Small Diameter Bombs (GLSDB) provided by the US, which will help improve Kiev’s military capabilities compared to high mobility artillery rocket systems (HIMARS). But it will need to wait until next year before receiving its first shipment, that the United States has adapted to strike at a nearly 100 miles (160km) range, according to Reuters. On February 3, 2023, the United States announced an aid package that included GLSDBs.

GLSDB is a combination of M26 rocket and GBU-39 small diameter bomb jointly produced by Boeing and Saab, which can be launched from ground platforms such as the M270 multiple launch rocket system (MRLS) and high mobility artillery rocket system (HIMARS). The combat-proven GLSDB allows the operator to rapidly engage a variety of targets, at any angle, over significant distances.

Ukraine needs GLSDB to augment the limited number of 100-mile range ATACMS rockets the U.S. has sent. It will allow Ukraine’s military to hit targets at twice the distance reachable by the rockets it now fires from the U.S.-supplied High Mobility Artillery Rocket System (HIMARS) and force Russia to move its supplies even farther from the front lines. People familiar with current timing say delivery to the U.S. by Boeing, the prime contractor for the GLSDB, will take place in late December – followed by several months of testing before onward shipment to Ukraine.

According to SAAB’s website, GLSDB is GPS-guided, can defeat some electronic jamming, is usable in all weather conditions, and can be used against armored vehicles. Boeing, in partnership with Saab, developed an “inter-stage adapter” to connect the GBU-39 to an M26 rocket. The advantage of the M26 is that there is an abundant stockpile of these rockets. Although the GLSDB can be launched from either MLRS or HIMARS, it also comes with its own launcher, making it easier to create decoys and more difficult for the enemy to locate and target.

GLSDB uses two battle-proven systems that allow operators to quickly hit a variety of targets, at any angle over a considerable distance. Since the start of mass production in 2006, tens of thousands of GBU-39 have been shipped to customers worldwide. The ammunition warhead weighs 93 kilograms and contains 16 kilograms of explosive. When diving on a target from a high altitude, thanks to the tungsten tip, it is able to penetrate concrete shelters. The fuze system allows it to also select the airburst or adjustable delay explosion after hitting before the bomb release.

In addition to accuracy, the main advantage of the GBU-39 is stealth, which makes it difficult to repel a massive strike with such a weapon using anti-aircraft missile means. The bomb has wings that fold in flight, which significantly increases the strike range. Its weight is quite small, only 130 kg, the diameter is about 190 mm, the length is about 1.8 m.

The initial versions of the bomb had a circular error probability of 5-8 m. This accuracy is achieved due to an on-board guidance system with inertial navigation channels and GPS. Inertial channels can provide operation in conditions of intense EW jamming by the enemy. Released from a sufficient altitude, the SDB can independently glide for a distance of up to 110 km.

In 2011, Boeing took on a new project with the Small Diameter Bomb (SDB), called the Ground-Launched Small Diameter Bomb (GLSDB). As part of the GBU-39 project concept, the developers wanted to provide the capability to launch bombs from ground launchers. For the bomb, the engine was selected from the М26 rocket, which is used to launch from the М142 HIMARS and М270. The maximum firing distance of GLSDB can reach 150 kilometers in the direction of launch. Thus, the GLSDB is a glide bomb crossed with a solid rocket motor.

With the help of a rocket motor, the bomb accelerates to a speed of 900-1200 m/s, after which, when it reaches an altitude of about 15-25 thousand meters, it is disconnected from the acceleration unit and begins controlled gliding to the target. The uniqueness of GLSDB is that it is capable of reaching 360-degree coverage for large and small angles of attack, flying around the folds of the terrain and striking targets located in the mountains, as well as returning to the target, which is behind the initial course of flight.

According to Saab the glider will be more difficult to intercept since it can be programmed to approach a target from any direction, and from a variety of angles. Unlike conventional artillery that follows a predictable path from launch to destination, the wings and navigation ability of the GLSDB allow it to evade obstacles and anti-air defenses by steering around them, even approaching from the target’s rear. Also, because the GLSDB is a glider it has little IR signature, making it a poor target for IR homing missiles such as MANPADS.

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