February 9, 2023: The latest American arms shipment to Ukraine includes the recently developed longer-range GMLRS guided rockets. Ukraine has been asking for those since mid-2022. They were satisfied with the performance of ordinary GMLRS but found there were important targets beyond its 85-kilometer range. The U.S. has a stockpile of over 3,000 ATACMS (Army Tactical Missile System) with 300-kilometer range held in reserve for American use. The Americans were afraid that if given a longer-range missile like ATACMS the Ukrainians would attack targets inside Russia that would lead to a disastrous escalation. Ukraine demonstrated that it had other ways to strike deep inside Russia and that did not prompt another Russian escalation. Ukraine was told that there would soon be a longer-range GMLRS called GLSDB (Ground-Launched Small Diameter Bomb) with a range of 150 kilometers. The manufacturer could send GLSDB to Ukraine as soon as they were available if the U.S. government included the GLSDB in a shipment of weapons to Ukraine. Now that GLSDB is available, the Americans are sending it to Ukraine, where it will get its first battlefield use.

Ukraine has been asking for the longer range (300 kilometers) version of ATACMS. It is, like GMLRS, carried and launched from the HIMARS truck but HIMARS can only carry and launch one ATACMS at a time. HIMARS can carry and use six GLSDB. Ukraine would still like the longer range ATACMS but the Americans need those for any military emergencies in the Pacific. There, the longer 300-kilometer range is crucial.

While Lockheed Martin developed ATACMS, Boeing developed and produced GMLRS. Boeing and Swedish firm Saab jointly developed an even longer range of GMLRS called GLSDB. The design concept is simple. Take the 227mm rocket motor that propels the GMLRS and use it to launch the latest version of the U.S. Air Force SDB (Small Diameter Bomb), the GBU-53 Stormbreaker.

Initially, the SDB was seen as the next generation of smart bombs and is a more compact design of the classic 227 kg (500-pound) unguided bomb. The streamlined shape of the SDB carried the GPS guidance system and other guidance components internally. SDB has a hard front end that can punch through nearly three meters (eight feet) of rock or concrete and a warhead that does less damage than the usual dumb bomb (explosives in a metal casing). That’s because the SDB warhead carries only 17 kg (38 pounds) of explosives, compared to 127 kg (280 pounds) in the conventional 227 kg (500-pound) bomb. SDB can carry other types of warheads, like the high-explosive one currently found in GMLRS.

Boeing/Saab received a contract to deliver production models of GLSDB to Ukraine by February 2023. Ukraine liked GLSBD because it can be fired from HIMARS, or any other GMLRS launch vehicle, and has a range of 150 kilometers. Moreover, it is more precise than GMLRS because Stormbreaker has multiple guidance systems that enable it to hit moving targets, including ships at sea and do so at night and in any weather.

Stormbreaker entered service in 2018 as the latest version of the SDB II (Small Diameter Bomb also known as GBU-53) in service. This version can identify, track and hit a moving target on the ground in any weather and at night. The novel targeting system was so impressive that the GBU-53 was given an official nickname; Stormbreaker. SDB is basically an unpowered missile which can glide long distances. This makes the SDB even more compact, capable, and expensive. While the original SDB I cost about $70,000 each, that went up to $300,000 for Stormbreaker.

Small wings allow the SDB to glide up to a hundred kilometers (from high altitude). Launching Stormbreaker from the ground (or even a ship at sea) using any GMLRS launcher provides long range precision firepower at relatively low cost. In 2017 the American marines demonstrated that GMLRS rockets could be launched from the flight deck of amphibious assault ships against land targets. This concept can use GLSDB to do the same, but also against enemy ships as well as land targets. This feature enables Ukraine to keep Russian warships out of areas of the Black Sea used by Ukraine. The GLSDB guidance system also makes it possible to hit moving land targets, like trucks or train cars carrying munitions or other Russian supplies.

GLSDB has shortcomings. It achieves the longer range using Stormbreaker the second stage of the GLSDB by having the Stormbreaker glide bomb use the GLMRS rocket as a first stage to take it to a high altitude and then separate and allow Stormbreaker, as the second stage, to proceed on its own. This is done by deploying wings and control surfaces that enable the unpowered second stage to locate and hit its target. GMLRS was a single stage missile and made its final approach to the target at a higher speed than GLSDB. The HIMARS and larger tracked GMLRS carriers have to get new fire control software installed before they can use GLSDB. It is unclear how long this will take. It could be simultaneous with GLSDB delivery or take several months.

The Ukrainians are the ones getting shot at and have a more “can do” wartime attitude that has time and again overcome issues like this that the Americans underestimated. NATO nations closer to Ukraine, like Poland, are more familiar with that attitude because they know that if Russia wins in Ukraine, Poland is next on the Russian conquest list. Poland and the larger NATO members like the United States, Britain and France often disagree because of the “we are next” attitude of Poland versus the more diplomatic attitude of the larger and farther away NATO nations. These differences in perspective and attitude makes sending Ukrainians what they feel they need a more complicated process than it should be.