The ability to detect explosives from a distance is vital to protecting against terrorist threats. But, what remains elusive is a reliable stand-off method for detecting explosives - a technology that allows airport screeners or first responders, such as police and fire, to keep a safe distance until they know what they're dealing with.
According to the Technical Support Working Group (the U.S. national forum that identifies, prioritizes and coordinates research and development requirements for combating terrorism), current stand-off techniques are limited in both stand-off distance and type of explosives that can be detected.
Several new stand-off technologies are emerging to close this gap, and academia is developing better stand-off explosive detection.
Safe to fly?
The problem is there are indications that airport security hasn't changed that much for the better
in the years since the 1988 terrorist
bombing of Pan Am Flight 103 over Lockerbie, Scotland, which led to an extensive re-examination of procedures in place for airline security. The issue was again examined after September 11, 2001.
Still, there is evidence that airport security is as much a myth now as it was prior to the attacks.
NBC News reported in March 2006 that federal investigators were able to slip enough explosive material past airport Transportation Security Association (TSA) screeners to blow a car trunk apart. It may have been merely a handful of components, but imagine what an IED (improvised explosive device) could do to a jetliner in flight.
Done at the request of Congress, investigators for the Government Accountability Office conducted the tests between October 2005 and January 2006. The goal was to determine just how safe U.S. airlines are from suicide bombers using cheap, readily available materials - the same as those used to build IEDs. The test was to see if investigators could smuggle IED components through TSA checkpoints for assembly once in the airport sterile area. It is believed an IED explosion in flight would likely destroy the aircraft.
The other bad news is the test didn't expose just one isolated incident of lax TSA security protocol at a single checkpoint. According to NBC, the test was run at 21 domestic airports and every one of them failed to discover the smuggled IED components. In no instance was a machine, swab or human screener able to detect the breach. Bomb parts weren't discovered even after investigators deliberately triggered extra screening of the bags.
Twenty-one failures out of 21 tests does not inspire confidence in TSA's ability to protect the flying public. It's painfully obvious that TSA needs remedial help.
A few good detectors
One technology is under development at Kansas State University (KSU), where a professor of mechanical and nuclear engineering has been recruited by the U.S. Marine Corps to develop a way to improve bomb detection without having to get in close proximity to suspicious containers such as cars, backpacks or briefcases that may conceal explosives.
The military needs better, more reliable means of detecting the deadly IEDs they must deal with in the Iraq conflict. Such a technology would ultimately be of interest to civilian law enforcement bomb squads and first responders as well.
"The Marine Corps needs what they call 'stand-off' bomb detection," says principal investigator Bill Dunn, KSU associate professor. "We're trying to give them a way to detect explosives remotely, so that people and things, that may be damaged if an explosive device is detonated, are far enough away that they are not injured or can survive the blast."
The KSU device uses pulses of both gamma and neutron radiation that penetrate into the target. The return signal, to a large extent, is determined by what is inside.
"Different chemical elements emit radiation of different characteristic energies," Dunn explains. "We're trying to detect what comes back from the target and see if it looks like what you would see in an explosive."
Dunn says his technique uses some technologies that others are investigating, but does so in a different way.
"Rather than try to completely identify the contents of a random target or to create a detailed image, we are simply trying to see if the contents emit 'signatures' that are typical of explosives," he explains.
By looking at how the set of signatures differs from the "template" for an explosive, Dunn hopes to be able to distinguish between inert and explosive contents.
Dunn's process is swift. A yes/no result is displayed within 1 to 10 seconds - considerably faster than bomb dogs, long the standard of military and law enforcement. It takes bomb dogs about 5 minutes to work a vehicle, sniffing tires, doors, trunks and hoods.
So far, Dunn has been able to determine what signals come back when he interrogates an object containing an explosive substance. Currently, he's trying to find out the best way to analyze the data to make sure the analysis is correct - that there indeed are explosives on board.
Dunn says the problem becomes more complicated by the size of the container. Large cars make it easier to hide explosives, while it is easier to detect explosives in a briefcase or a knapsack.
"Even if you put other things in small containers, we think we're going to get a set of signals that indicate the presence of explosives if they are there," Dunn says. "With larger containers, it can become very complex, but we're still hopeful."
The research is past the proof of principle stage. Dunn is now trying to optimize the design of the system.
"Full field implementation will require that templates be constructed for various types of targets containing various explosive materials in various package geometries and with various other cargos," he says.
Nevertheless, with sufficient funding, he thinks he can have a working prototype within a year or two.
Beam me up, Scotty
To improve upon explosive screening at airports, the University of Arizona (UA) has designed a Star Trek-like device that may help TSA finally make the grade.
According to UA scientists, the "tricorder" technology can screen passengers for traces of explosives or illegal drugs as they walk through security portals, and handheld units scan the baggage.
The device would make it possible to screen 100 percent of passengers for explosives, instead of the random samples TSA screeners now obtain by current swabbing methods.
Rather than analyzing a swab from a person's briefcase, the UA technology could detect the traces of explosives left in the air that passes over a person who has handled explosives.
"The new device can be pocket sized," says principal investigator M. Bonner Denton, UA professor of chemistry, versus the analyzers currently used in airports that are about the size of a tabletop microwave oven.
Such a device also could be employed at border crossings to detect illicit drugs, as well as smuggled explosives.
"This is more sensitive than dogs' noses," says Denton. "And it tells you what material has been detected. Dogs just tell you something has been detected."
No swabbing
In yet another project in academia, scientists at Purdue University have come up with a fast, reliable means of detecting residues indicating the presence of trace quantities of several common explosives, as well as chemicals such as those found in biological and chemical warfare agents, within a few seconds.
The technique works on just about any surface, including clothing, human skin and luggage.
The new method uses a tool found in many chemistry and
biology labs called a mass spectrometer, only the Purdue mass spectrometer has been modified to analyze samples directly from the environment rather than from samples that require lengthy pretreatment.
"Mass spectrometry is the gold standard in analytical chemistry," says lead investigator R. Graham Cooks, professor of analytical chemistry at Purdue. "However, mass spectrometers are traditionally slow since they require extensive preparation of the sample and the instruments."
Until this work, the future of mass spectrometry in field work looked bleak. Most mass spectrometers are unwieldy, cabinet-sized machines that require samples to undergo hours of intensive preparation before testing - a huge problem when a large number of containers need to be processed quickly.
Scientists have known for years that without a way to streamline the analytical process, mass spectrometry would have limited use in the field.
Cooks' team has developed a method of creating ions from samples, meaning the lengthy process of sample preparation can be avoided, yielding results typically in less than 5 seconds - all this, while at the same time maintaining mass spectrometry's characteristic low false positive and low false negative rates.
The new method, called desorption electrospray ionization, or DESI, has the ability to detect explosives on virtually any surface at ultra-trace levels, Cooks says.
Cooks believes a portable tool based on the technology could prove valuable for security in public places worldwide. In principle, the technology could be totally automated by positioning the DESI source near a luggage conveyor belt, for instance, which would allow for high throughput analysis, eliminating the intervention of an agent and further decreasing analysis time.
"In the amount of time it requires to take a breath, this technology can sniff the surface of a piece of luggage and determine whether a hazardous substance is likely to be inside, based on residual chemicals brushed from the hand of someone loading the suitcase," Cooks explains.
If the DESI technology is as fast and accurate as believed, it could be useful in screening suspect packages not only in airports, but also train and subway stations, courthouses, federal buildings, schools, and other places where there have been problems in the past.
"Because the technology works on other surfaces, such as skin and clothing, as well, it also could help determine whether an individual has been involved in the handling of any of these explosives or chemicals," Cooks says.
According to Cooks, the DESI technology has already been used to analyze pharmaceuticals at up to three samples per second.
As terrorists and suicide bombers invent new and more powerful ways to inflict terror, so too will the world of academia and research develop new technologies to combat them.
