Next-generation technologies ensuring safety in civil aviation.
Aviation Week & Space Technology.- 1996 .- 145, No. 15 .- P. 44,46
Next-Generation Technologies Ensuring Safety in Civil Aviation
The Federal Aviation Administration (FAA) and other US federal agencies fund research and development of technologies that ensure safety in civil aviation.
The plans call for the creation of new devices and systems, bringing them to the level of operational testing. Contracts are awarded for developments in new areas, provided that at least seven competing bidders participate in the competition for the contract.
Federal funding for research and development of explosive detection systems increased from 1978 to $246 million. Annual expenditures for this item increased from $25 million in 1994-95 to $39 million in 1996. The explosive detection systems and devices used successfully at London's Heathrow Airport and considered the best for major airports were developed with U.S. federal funds.
In addition to nuclear technology, the methods under consideration include advanced X-ray, radar, chemical vapor analysis, and magnetic resonance. Although some of these methods are not yet used on airlines, they may prove very important in the coming years.
In the area of X-ray explosive detection systems, the FAA has funded the use of X-ray diffraction to detect crystalline explosives. However, according to some data already obtained, the effect of this method was several orders of magnitude lower than expected. The approach of American scientists was to inspect the entire piece of luggage, for example, a suitcase, turning it to obtain several images at several irradiation angles. Philips (Germany), which is also studying the possibility of using this method, is forced to switch to using a pencil beam of radiation to inspect suspicious areas marked by another system. There were also problems with the transmission of signals for interpreting the X-ray diffraction image. However, at present, the analysis of signals is much better than several years ago, and there is hope that the method will work.
The FAA also supports the development of improved dual-energy X-ray and backscatter X-ray systems, which are already in use for baggage screening. Improvements to low-energy X-ray systems used for carry-on baggage screening include producing images with greater angular resolution, increased dynamic range, and the use of dual-energy X-rays to determine the atomic numbers of substances.
With funding from federal agencies, work on radiofrequency modeling of atomic nuclei, or nuclear quadrupole resonance, is moving toward commercial application. The FAA-DoD Research Support Working Group has awarded $3.6 million to Quantum Magnetics to advance nuclear magnetic resonance technology that began at the Naval Research Laboratory. The working group is funded by the National Security Council to coordinate research and development efforts among federal agencies in the counterterrorism program.
The quadrupole resonance method is a nuclear magnetic resonance method that does not require a strong magnetic field to obtain signals resulting from the interaction of the crystalline structure of the explosive with the exciting electromagnetic field. Each structure can be identified by the resonant absorption of radiation at a specific frequency characteristic of it. But the difficulty in using this method is in choosing the correct pulse repetition rate for the different types of explosives being examined. This difficulty has delayed the FAA in compiling a complete list of explosives for their identification.
The FAA will fund testing of the screening systems at most U.S. airports over the next six months. One version of the baggage screening system was tested for two weeks at Los Angeles Airport by United Airlines in June 1996. The test showed a false alarm rate of less than 10%. No prototype explosives were used during the tests, so the detection rate was not measured. This version of the system was to be tested at the FAA Technical Center in October 1996. A smaller version of the system was tested by Delta Air Lines during the Atlanta Olympics to detect electronic devices in baggage.
Quantum Magnetics has also developed a miniature magnetic resonance imaging detector to image and analyze the contents of bottles carried by airline passengers. The passenger tells the operator what liquid is in the bottles, and the operator sets the detector to analyze that liquid. If there is a discrepancy, the device sounds an alarm. The device itself cannot determine what is in the bottle. This development was supported by the FAA, and work is currently underway to expand the database for tuning the detector. The magnetic resonance imaging method used in the detector is unlikely to find widespread use, since the strong magnetic field can erase data stored on magnetic memory disks, credit cards, and other magnetic storage media.
The FAA also supports and funds the development of radar methods for screening airline passengers and the bottles they carry. It awarded Spatial Dynamics Applications $1.6 million to develop and manufacture a «dielectric portal» to detect unusual objects on a passenger's body based on changes in the permittivity and scattering coefficient of radio waves by the body. The passenger enters a cabin about 1.5 m in diameter, which contains a vertical panel with 32 ultra-high-frequency transceivers that scan the passenger for 3 seconds. The amplitude and phase of the reflected signals are measured. The system does not create an image, but reacts to the presence of anomalies. The sensitivity of the system is set at a level where it does not react to small objects such as zippers or buckles. The detection rate for larger objects is within FAA standards. The system is to be tested at one airport before the end of 1996.
Spatial Dynamics Applications, under another small FAA contract, is to develop a device to measure the permittivity of liquids in bottles to determine their contents. The device is to be an alternative to the magnetic resonance-based device. Liquid explosives were used to blow up the South Korean airliner.
Pacific Northwest National Lab. has been awarded $5.3 million by the FAA to develop a walk-through arch with a millimeter-wave radio source to obtain radar images of objects hidden by airline passengers. A passenger enters the inspection booth and holds onto the railings to maintain a stable position. A rotating vertical array containing 400 transmit/receive modules scans him for 4 seconds. A three-dimensional image of the passenger being screened is formed using the phase topography method. The operator is presented with 16-32 two-dimensional images of this model for analysis. The resolution of the method is theoretically equal to half the wavelength, or about 5 mm. The developers' goal is to reduce the time for signal processing, image formation and analysis to 10 seconds or less.
The system is to be demonstrated to the FAA in April 1997. The operator will make the decision on the outcome of the inspection until automatic image recognition becomes possible. The cost of a prototype system will be about $200,000, and in series production it could fall to $50,000.
Technology is also being developed to detect explosives by analyzing the chemical vapors they emit. Thermedis has a contract to develop a walk-through arch. As an airline passenger passes through this arch, their clothing will come into contact with the vacuum walls, which will collect the chemical vapors and particles emitted by the passenger. The vapors and particles collected by the walls of the arch are analyzed by gas chromatography or chemiluminescence detection devices. This system is currently being tested at Boston Airport. It is estimated that it can handle 360 people per hour. This may require the use of two different types of detectors in each arch, alternating to reduce analysis time. The FAA has allocated $4 million for the development of this arch.
Another area of technology for detecting explosives by the vapors and particles they release is ion mobility spectroscopy. Explosive molecules are small molecules that can accept electrons. The resulting negatively charged ions are accelerated and move toward the positively charged lattice in the direction opposite to the gas flow. The time of flight of the molecules is measured. The ability to form negatively charged molecules and measure their time of flight provides good discrimination of substances. The FAA spent about $2.5 million to develop two prototypes of a system based on this technology and deliver them to airports for testing.
Vapors or particles of explosives are collected from the walls of the passage arch by passing air currents through it. These vapors and particles are directed to an explosive detector for analysis. Another alternative method of collecting traces of explosives, which is under development, is to examine tickets or other documents presented by an air passenger and a special sign that he touches.
The possibility of using biotechnology to detect explosives is also being studied. The FAA has awarded a contract to the Naval Research Laboratory to create antibodies similar to explosives. The antigen, coated with fluorescent dye, usually weakly adheres to the antibody. A 400-liter air sample is collected and concentrated to form a 3-cc liquid, which is passed through the antibody. If particles of a particular explosive are present in the liquid, they adhere more strongly to the antibody than to the antigens. Antigens that have lost adhesion to the antibody are detected by their fluorescent glow. Antibodies have already been created for TNT and some other explosives. But the method is not yet developed enough to be tested in real airport conditions.