Artillery: Smarter Sadarm Subsequently Succeeds


June 2, 2020: Are tanks becoming obsolete? With smarter and cheaper anti-tank weapons available, including missiles, "smart mines", and air delivered robot tank killers like Bonus, Smart and SADARM, it will only take one incident of the "cheap and smart" stuff beating up on a lot of tanks to make the point. Another telling sign is the lack of enthusiasm in America and Russia for designing a replacement for current tanks, at least not a replacement that features the "bigger gun and thicker armor" that has characterized tank development for the century.

Then again, it may be premature to write off the tank. For a weapon that has been dismissed as obsolete for decades, it still survives. True, there are a lot fewer (less than 50,000) tanks in use now than there were in 1991 when there were over 100,000. And the new ones built each year are not sufficient to replace those that age out each year. Less affluent nations will still find tanks useful against their own citizens, or equally poor neighbors who also have some tanks. The U.S. and its allies found out that the M-1 and similar Western tanks were very useful against irregulars in Iraq and Afghanistan.

The math, however, is unavoidable. Unless a new arms race begins the number of tanks in service will slowly decline year by year. Meanwhile, the number of "smart weapons" grows rapidly. The tank won't completely disappear soon but never again will it be the key weapon for ground warfare.

The U.S. Army recently ordered another batch of the Swedish BONUS 155mm anti-tank artillery shells. This is the second batch purchased and so far it appears the Americans are keeping an eye on this tech, not adopting it. The first American purchase of BONUS was in 2018.

The BONUS is a fire and forget guided 155-millimeter munition designed for destroying armored targets. BONUS was a joint project by Britain, France and Sweden with the Swedes taking the lead in production. BONUS can be fired from standard NATO 155mm artillery and has maximum 35 kilometer effective range. The round carries two submunitions, each with their own multiband IR (heat) sensors backed by laser radar. BONUS uses small winglets to slow its descent rather than small parachutes that are used in earlier similar submunitions, like the German SMART shell. The parachutes are easier to spot and more expensive and complex to use.

These submunitions separate in the last phase of flight at about 175 meters and scan area for targets. Each warhead can scan about 32,000 square meters and hit even moving targets within that area. The destruction is achieved by an Explosively Formed Penetrator (EFP) able to punch through more than 130 mm (five inches) of armor. This doesn’t seem like much but the tank armor is strongest at the front and not at rear or top. The only defense against this “top attack EFP is active protection systems (APS) such as Trophy but even these have difficulty dealing with things like EFPs. The APS systems work great against HEAT warheads because these disperse cumulative streams of superheated gases,  but this can’t be done versus a molten metal projectile formed by the EFP. Moreover, thanks to two submunitions per shell, the artillery pieces remain for a shorter time on their firing position, so they are less likely to get caught by enemy counter-battery fire. The drawback of these “smart” rounds that these are significantly more expensive than GPS guided Excalibur shells and the laser-guided Copperhead or Russian Krasnopol. The BONUS concept isn’t a new one because the U.S. and Germany used similar tech for the American SADARM and German SMART 155.

The American XM898 SADARM (Search And Destroy Armor Munitions) dates back to the late 1970s when the U.S. Army started to look for a “smart” anti-armor 155 mm projectile. About a decade later SADARM had been developed and prototypes built but due budget restrictions in 1990 the program was slowed down. In 1993 the first tests were unsatisfactory because SADARM hasn’t been able to hit a moving target and overall accuracy was poor. The project managers promised to improve the technology, they did and a year later program was approved for limited low rate production. Unfortunately for SADARM the later (1995, 1998 and 1999) tests showed only a little improvement. In all trials, the SADARM struggled to get an 80 percent reliability rate. This together with significant cost overruns were reason enough to end production in 2001. This failure did not mean the end of the submunition technology, which was subsequently adopted by the U.S. Air Force as well as the developers of the SMART and BONUS shells. The submunition was always meant to be carried by a wide variety of projectiles including MLRS rockets, mortar shells and cluster bombs.

The reliability of the submunition improved and it soon showed as the payload of the CBU-105 half ton cluster bomb. Each of these bombs is a container carrying 40 BLU-108/B SFW (Self Forging Warhead) bomblets. These bomblets are basically the SADARM submunition. Individual SADARM submunitions have their own radar and heat sensor that searches for armored vehicles below and destroys them with a specially shaped charge warhead. The SADARM sensors can search and attack vehicles within an area of roughly 150 x 360 meters, as they slowly descend. The self-forging metal projectile used by the SADARM submunition punches through the thinner armor on the top of the vehicle. If a target is not found, SADARM self-destructs.

The first use of the CBU-105 was on April 2nd, 2003, when a B-52 dropped six of them on an Iraqi army column moving south from Baghdad. Most of the vehicles were later found destroyed. Since then there have been several export customers for CBU-105 and U.S. Air Force still has them stockpiled for future use.

The Russians have a version of their own, SPBE-D, for sale to anyone who can pay for it. The American CBU-105 is preferred because the United States pioneered the technology, and demonstrated it could work in combat. India faces a large force of Pakistani tanks, and CBU-105 is an inexpensive and quick way to destroy lots of armored vehicles.

Russia eventually responded to the SADAM submunition threat by developing a new generation of ERA (Explosive Reactive Armor) that now covers the top of the turret and engine compartment of their tanks. It is unclear just how effective this ERA is against the SFW penetrator. In theory the ERA should protect against ERA or at least reduce SFW effectiveness,

Due to recent changes in the strategic environment, the U.S. Army has shifted from counterinsurgency operations against technologically weak opponents to “near-peer” situations (fighting against someone with similar forces. Usually, air delivered weapons are the most effective way to hit ground targets but against near-peer foes with advanced air defenses, airstrikes are not always the best way to go In this type of situation artillery with a “smart” specialized anti-tank munitions is a safer option than cluster bombs and that is one reason SMART and BONUS shells are still in production. --Przemyslaw Juraszek


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