Air Weapons: SDBs For Israel


October 25, 2023: A few days after the October 7th Hamas attack on Israel, an Israeli air transport took off from an American Air Force base to the deliver the first of a previously ordered shipment of a thousand SDBs (Small Diameter Bombs). These are glide bombs with a range of over 60 kilometers. They can maneuver to a specific target and land within a meter of the target it was aimed at. The Israelis are using these SDBs against Hamas targets in Gaza. This is not the first time; in 2014 Israel did so with the main targets being Hamas storage sites for unguided rockets to be fired at Israel. These sites were usually in residential areas so Hamas could use local civilians as involuntary human shields against Israeli attacks. Any civilians killed were declared an Israeli atrocity in the subsequent Hamas press release, but Israel regularly sought to avoid civilian casualties while Hamas did not.

SBDs have been used since 2006 and the first combat use was that year in Iraq to provide close support for U.S. troops fighting there. Since 2014 Israel has ordered over 5,000 SDBs. They are the preferred weapons against Hamas in Gaza and Hezbollah and Islamic terrorists in Lebanon and Syria. Larger bombs are used when the enemy is outside populated areas. To avoid this, the enemy spends as little time outside populated areas as possible. Human shields and structures to hide in are found in populated areas. Hamas leaders must travel in the open more frequently than their followers and often do so in civilian automobiles trying to look like innocent civilians. The Israelis can often obtain specific information about such movements and launch airstrikes. Sometimes SDBs are but more often a laser guided missile launched from a UAV, helicopter or jet fighter does the work. These missiles are faster and a bit more accurate than an SDB as well as carrying less explosives and causing fewer collateral (nearby) casualties.

Israel also designed and built its own guidance kits for larger bombs providing additional features the American JDAM kit lack. It’s not worth the time, effort and expense to develop competition for the SDB.

The United States is also donating SDBs to Ukraine as part of the NATO effort to provide Ukrainian forces with sufficient weapons to defeat the Russian invaders. Some of the SDBs sent to Ukraine are longer range and are attached to a rocket which carries the latest SDB version, the StormBreaker. This version entered service in 2020 and is equipped with hardware and software to enable it to hit moving targets. To do this StormBreaker has three different guidance systems: radar, heat seeker, and homing on laser light bounced off the target. That means no matter what the weather or time of day, there is a guidance system that will find the target. Even without human intervention, the three sensors enable StormBreaker to find targets in a cluttered and obscured (by weather or darkness) environment. It took three years of tweaking and testing, and it was a cycle repeated several times until the StormBreaker team won because they finally got a promising concept to work. The StormBreaker design was finally doing everything promised but never quite delivered, and the air force was so pleased that the upgraded SDB was given an official nickname; Stormbreaker. Much catchier than SDB, or even SDB II. Publicizing the new, improved Stormbreaker does cause a bit of confusion for those who do not follow the SDB saga regularly.

Most of those who investigated Stormbreaker eventually realized it is not just like the SDB, it also has a better press agent. At the same time Stormbreaker is a visibly, and operationally, different small bomb than SDB and SDB II. Yet there will continue to be demand for the original GBU-39 SDB and GBU-40 SDB II. Both are cheaper and less capable than StormBreaker. Yet more warplane fire control systems can handle GBU-39/40 and do what their users require and cost a lot less than StormBreaker. The GBU-40 version has laser guidance added to GPS but lacks all the additional features of StormBreaker. While the U.S. Air Force and Navy were eager to switch to StormBreaker, many foreign customers were not sure they needed the much more capable, and expensive, StormBreaker. One problem with the Stormbreaker is that the aircraft using it must have its fire control system upgraded considerably to handle it and that upgrade is more complex than needed for earlier SDB versions. Initially only the F-15E and F-22 received Stormbreaker upgrades. The F-35 couldn’t use Stormbreaker until recently when its software was updated to handle the many additional capabilities of the GBU-53. Similar upgrades for the F-18E were also ready by 2023.

StormBreaker had been in development since 2005 and announced as ready several times, at least until the last round of Operational Tests were conducted and, as often happens during these realistic or operational, tests something goes wrong. In other words, SBB II was, for a long time, ready to go, but not quite ready for prime time, better known as actual combat. At least not for missions requiring certain features that were having Operational Test problems.

When first announced in 2005, StormBreaker was described as possessing multiple sensors and a data link that enabled it to hit vehicles going at high speed and in bad weather. Sounded great but the repeated failures to get past the Operational Testing meant StormBreaker did not boost sales as much as anticipated. From the beginning, StormBreaker had an encrypted data link that enabled the fighter (especially F-35) pilot to guide the SDB, with great precision, to hit moving targets. This communications capability enabled the SDB movement to be controlled via the air force's airborne Internet (Link 16), which means whoever is directing StormBreaker to a target can be anywhere, even another aircraft or on the ground.

The original StormBreaker specifications called for three different guidance systems: radar, heat seeker, and homing on laser light bounced off the target. That meant no matter what the weather or time of day there is a guidance system that will find the target. Even without human intervention, the three sensors enable StormBreaker to find targets in a cluttered and obscured, by weather or darkness, environment. Now it works but it was felt that a new name like StormBreaker might overcome the shaky reputation the original SDB II designation had earned.

There is a much longer-range version of StormBreaker was created by attaching StormBreaker to a GMLRS guided rocket in place of the rocket’s normal warhead. When launched, this version of the rocket will release StormBreaker after reaching its starting to plunge earthward. At that point StormBreaker glides the rest of the way as it normally does and achieves a maximum range of 150 kilometers. This version was called GLSDB (Ground-Launched Small Diameter Bomb). Ukraine has been asking for the longer range StormBreaker 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. also had about 3,000 ATACMS (Army Tactical Missile System) with 160 or 300-kilometer range, depending on the weight of the warhead. These ballistic missiles were held in storage 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 which when used did not prompt further Russian escalation. That led to the 160km-range ATACMS I recently showing up in Ukraine and used against Russian targets in Ukraine that had been out of range until now. Ukraine was also told that the longer-range GMLRS called GLSDB with a range of 150 kilometers was on the way. Now GLSDB is available, and it has also been used in Ukraine, where it was used in combat for the first time. Russian air defenses detected and shot down some GLSDB attacks, but that was expected. The same thing happens to the even slower attack UAVs Ukraine often uses. Attackers consider that there will be such losses and use enough missiles that some get through.

Ukraine has been asking for the longer range (300 kilometers) ATACMS II. 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 ballistic missile, but the Americans need those for any military emergencies in the Pacific. There, the longer 300-kilometer range is crucial.

ATACMS is no longer in production because it is too expensive, at nearly two million dollars each. Developed near the end of the Cold War, when that conflict ended in 1991 so did the urgent need for ATACMS. Only 3,700 were manufactured and between 1991 and 2014 560 ATACMS were used in Afghanistan and Iraq. Now some are being used in Ukraine.

While Lockheed Martin developed ATACMS, Boeing developed and produced GMLRS. Boeing and Swedish firm Saab jointly developed an even longer range of GMLRS with a new Ground-Launched Small Diameter Bomb (GLSMDB) warhead. The design concept is simple. Take the 227mm rocket motor that propels the GMLRS and use it to launch 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 the new Ground Launched Small Diameter Bomb (GLSDB) to Ukraine by February 2023. Ukraine liked GLSDB 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 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 new SDB version was given a unique designation; 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 be used by 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 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 must 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.




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