Americans boost Ukraine's arsenal with upgraded GLSDBs

According to Reuters, the Americans have made the GLSDB missile bombs resistant to the effects of Russian GPS signal jammers, which caused the suspension of these new weapons’ deliveries in 2024.

It's worth noting that the GLSDB missile bombs, with a range of about 150 kilometres, are an excellent substitute for the initial versions of MGM-140 ATACMS ballistic missiles with a range of 165 kilometres, which the U.S. had exhausted supplies of. The readily available option to destroy Russian logistics or command points at a distance of over 100 kilometres would be a tremendous help for Ukraine.

GLSDB (Ground Launched Small Diameter Bomb) has been developed since 2015 at Sweden's initiative to provide extended range for the M270 MLRS and M142 HIMARS multiple launch rocket systems while maintaining low costs.

The idea is to combine the rocket engine of a GMLRS missile with a GBU-39 SDB glide bomb. Utilising existing solutions offers quick production capabilities and a lower price than developing a new long-range system from scratch. The principle of operation involves launching the missile bomb, after which the section with the rocket engine detaches after burnout, and the bomb continues on its course to the target after unfolding its wings.

Ukraine became the first user of this weapon, and it turned out that after promising first months, the GLSDB missile bombs became useless. This was due to disruptions in GPS navigation, which is the primary guiding system for SDB bombs, by systems like the R-330Zh Zhitel.

Indeed, they are also equipped with an inertial navigation module that calculates the position based on, for example, flight speed or time to calculate position. Still, these calculations are always subject to error, which accumulates with distance. As a result, the bomb's precision can degrade from the declared few feet to several hundred feet depending on the distance.

This, combined with a small warhead weighing 90 kilograms, of which about 16 kilograms is explosive material, makes it ineffective if deviated from the point of impact. The problem is not as pronounced with, for instance, JDAM-ER bombs, particularly those weighing 450 kilograms or 900 kilograms, where nearly half consists of the explosive charge, or with MGM-140 ATACMS ballistic missiles. In their case, firepower can offset the lack of precision.

Unfortunately, it is not known how the Americans modified the GLSDB missile bombs, and perhaps the secret will be revealed when pictures of the wreckage surface online. One option might be the application of additional HOJ (Home-on-jam) seeker heads guiding the bomb to the source of interference.