Wired News: We Can Detect Liquid Explosives
For a machine to detect explosives in liquid or solid form, it bombards an object with energy — such as radio waves or neutrons — and in seconds measures the reaction, a response that differs depending on the material’s chemical properties. Software in the machine is programmed to alert screeners if it detects chemical signatures known to match those of dangerous materials.
A key question, though, is whether this kind of detection system can realistically block terrorists from bringing seemingly innocuous liquids past security and combining them later to deadly effect.
Certainly, some common ingredients in liquid explosives can be programmed into the detector. But Kant, at Rapiscan, said he would not discuss the vulnerabilities of that approach. “Whether it detects the components of explosives and which ones, there’s no way I’m putting that in print,” he said.
Sean Moore, vice president of sales at a rival maker of explosive-detection systems, HiEnergy Technologies, said future screening machines could be linked so that they might let a person through with one kind of liquid — but stop another traveler carrying another type of liquid that reacts explosively with what the previous person was carrying.
This list of liquids to watch for, he acknowledged, would have to be constantly updated as “terrorists become more ingenious.”
That scenario, however, remains a ways off. Not only are security checkpoints not networked, but HiEnergy has not sold a single device for U.S. airports. Its main project so far involves field tests on unattended packages in Philadelphia with the Southeastern Pennsylvania Transportation Authority.
A different kind of scanning technology that already has begun to emerge — backscatter screening — has no automated ability to detect explosives. But its backers say it nonetheless could go a long way to halting plots like the one apparently thwarted this week.
Backscatter screening is much like traditional X-rays, except that the system sends more, but weaker, X-rays at an object. It can’t penetrate skin, but it can reveal items under someone’s clothes — such as a hidden bottle of liquid.
A major problem is that the view is so powerful that an individual’s private parts can be seen, which forced the TSA to delay tests while vendors tweaked the machines’ programming to distort or mask bodily images. And backscatter systems still leave it up to a human screener to recognize a suspicious item. [Full article]