With the flurry of controversy over how the US and the world should respond to the apparent use of chemical weapons in Syria and the implied assumption that such a response might be an attempt to destroy the weapons, what is often overlooked is how difficult they can be to safely eliminate. Decades after the first Gulf War, some former chemical weapons depots are still too toxic for human entry, after bombing made a mess of the stockpiles they contained. Daryl Kimball of the Arms Control Association framed the problem in his recent testimony on the subject, “If you drop a conventional munition on a storage facility containing unknown chemical agents — and we don’t know exactly what is where in the Syrian arsenal — some of those agents will be neutralised and some will be spread. You are not going to destroy all of them.”

Over the last decade, the US has invested hundreds of millions of dollars in a set of projects called Agent Defeat, that aim to both reduce the impact of chemical agent-based weapons and to create ordinance that can be used to destroy chemical weapon stockpiles. By their nature, Agent Defeat weapons are difficult to test, and many of the project details are classified, but from budget information released by the sponsoring Defense Threat Reduction Agency (DTRA) and DoD project proposals, it is possible to assemble a picture of the challenges and some of the likely solutions.

Binary form: Seatbelts for chemical weapons

Early chemical weapons were simply very toxic substances stored in canisters, bombs, or artillery shells. They were a huge safety hazard at the factory, in transit, and in the field. Any type of leak could prove fatal to those in the surrounding area. Binary systems were developed that stored two separate precursor chemicals that could be mixed immediately prior to use — often upon launch of an artillery shell, or after dropping a bomb. This greatly reduced the threat posed by inadvertent release of the chemical agent by its owner, but didn’t eliminate the difficulties with safe disposal.

For many binary weapons, such as a typical sarin gas artillery shell known to have been owned by the Iraqis and (possibly the Syrians), the two precursors — typically isopropyl alcohol and methylphosphonyl difluoride — are separated by a physical disk that is ruptured by the force of firing. Unfortunately the disk can also be destroyed in an explosion, like the one created if the storage area is bombed — resulting in the immediate creation of a cloud of deadly toxins.

CrashPad: Portable incinerator

Fortunately, some common precursors, like the isopropyl alcohol used to create sarin gas, can be incinerated. If enough heat is created quickly, the military believes the production of sarin gas can be greatly reduced or even eliminated. For this purpose it has funded the creation of the BLU-119/B (aka CrashPad — with the PAD standing for Prompt Agent Defeat.) The CrashPad is a 420-pound weapon with a “blast-fragmentation” warhead designed to incinerate chemical agents and precursors before they can escape into the surrounding area. This is accomplished by using white phosphorous in the payload, resulting in a thermobaric or high-heat weapon that uses oxygen in the environment to burn. For comparison, this video shows about the same amount of thermobaric explosive as contained in a CrashPad, being used to detonate a car:

Another version of the CrashPad, that couples it with some type of bunker-busting bomb, has also been commissioned. Called Shredder, it is designed for use where the targeted weapons or chemicals are stored deep within reinforced bunkers. It is not publicly known whether CrashPad or Shredder have ever been used in combat.

Rip it apart: For heavier than air chemicals

For chemical and biological agents that are heavier than air, simply ripping things apart can work. Destroying their containers — whether bomb casings, artillery shells, or storage canisters — and letting the agents settle to the ground could greatly reduce the area affected. The CBU-107 is a specially designed bomb containing up to 3,700 metal fragments — 350 14-inch rods, 1,000 7-inch rods, and 2,400 2-inch rods — that scatter throughout a 60-meter target area. If exploded in a WMD stockpile, this PAW (Passive Attack Weapon) should destroy nearby canisters, shells, and bombs, releasing their agents locally.

The result of a PAW strike will still be a toxic mess, but hopefully one that only affects a limited area. The PAW has one other trick up its sleeve: Because the rods are propelled at very high speeds, they will heat up whatever they hit. So, much like a Sabot anti-tank round can melt its way through tank armor, the PAW’s payload may be able to incinerate many of the chemicals located where it is detonated.

Another unique feature of the CBU-107/PAW was its development process. Going from design to finished development in only 98 days, at a relatively small cost of $40 million, the weapon was one of the first uses of the Pentagon’s new rapid-response development system. By re-using existing components, like the structure of the CBU-103 and CBU-105 bombs, the new weapon was designed quickly and available soon after for deployment in Iraq.

Use of any of these munitions is made much more complex if the targeted weapons are housed near populated areas, of course. Similarly, none of them have had extensive field tests — although they have been simulated on USAF’s SERPENT attack simulator. As a result, many weapons experts predict that if strikes in Syria do occur, they may not attempt to directly destroy its chemical weapon stockpiles.

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