Most explosive detection technology has been centered on systems tuned to nitro-based explosives or on imaging devices with high X-Ray or other spectrometric profiles. There are, however, several readily available and highly effective non-nitrogenous high energy explosives which are essentially invisible to explosive detection technologies currently in development.
"Transparent" explosives which will be discussed in the first part of this presentation include peroxides (used in both monergolic and hypergolic applications); acetylene precursors; and fuel/air bomb systems involving use of olefin oxides, acetylene, other hydrocarbons, and similar high energy agents. For many of these, blasting cap or similar detonating devices requiring easily detected triggering systems are not required. Areas to be covered for these explosive systems include commercial availability or ease of clandestine manufacture (preparative schemes and raw materials); stabilities in transit; ignition/detonation systems; energy release; and potential for use in clandestine operations. Suggestions for enhancing airport detection will also be presented.
The second part of this paper will deal with numerous composite explosives in the form of intimate mixtures of condensed-phase fuels and oxidizers, which also could be formulated. Many of these rely on perchlorate, chlorate or hypochlorite salts as oxidizers. Several self-igniting systems such as boranes, phosphorus and alkali metals will be discussed as well.
The forensic analysis of explosives and explosives residues is introduced with a short historical review followed by a discussion of state-of-the-art protocols as followed by the FBI Laboratory. The review includes laboratory and field analytical techniques and describes actual case scenarios as examples.
Probabilistic risk assessment (PRA) is a tool intended to aid decision makers in choosing among complex safety alternatives. This paper describes the general PRA approach (as applied to practical systems/processes) and provides simple examples relevant to the aviation security problem.
The increasing sophistication of terrorists and their ability to exploit technological advancements makes effective detection of weapons and explosive devices critical to aviation security. The Federal Aviation Administration (FAA) is the leading federal agency responsible for the safety and security of civil aviation. Acts of terrorism against the aviation community have demonstrated an increasing level of knowledge in the design and deployment of explosive devices and weapons. Sabotage for political purposes, particularly in the international arena, has surpassed hijacking as the foremost threat. The research and development challenge for the FAA is to counter the increasing sophistication of these terrorists with a broad range of technologies which thwart and render their attempts to sabotage civil aviation ineffective.
Imaging and visualization techniques for aircraft security are discussed. Planar transmission imaging techniques using x-rays and nuclear radiation are described along with their intrinsic limitations. Methods for distinguishing materials using dual - energy and multi-energy x-ray sources are shown along with techniques for simulating materials with mixtures of other materials. Tomographic reconstruction methods are derived and estimates made of their performance. X-ray diffraction imaging is shown as an alternative method to transmission measurements. Evaluation of overall system performance through the use of "receiver operator characteristics" (ROC) methods is discussed along with their application to evaluation of performance of screening systems.
This paper presents an exploration of several techniques for detection of Improvised Explosive Devices (IED) using interactions of specific nuclei with gammarays or fast neutrons. Techniques considered use these interactions to identify the device by measuring the densities and/or relative concentrations of the elemental constituents of explosives. These techniques are to be compared with selected other nuclear and non-nuclear methods. Combining of nuclear and non-nuclear techniques will also be briefly discussed.
The dog-handler team as an explosive detection system is critically reviewed. The probable means of detection, olfaction or the sense of smell, is described to understand how sensitive and selective the dog-handler team can be. The empirical and experimental data available at this time regarding the means by which the teams are selected, trained, deployed, and maintained are presented and evaluated.
The dog-handler team is recognized as a very effective system for detection of explosives with considerable potential for improvement. The need for more valid data relating to the mechanisms of detection, of training, and of selection are expressed and explained. Potential means of improving the system are proposed.
The Federal Aviation Administration (FAA) is the leading federal agency responsible for the safety and security of civil aviation. Recent acts of terrorism against the aviation community have demonstrated an increasing level of sophistication in the design and deployment of explosive devices. Hijacking, once the dominate threat to aviation, has been replaced by the threat of sabotage for political purposes. Since the bombing of Pan Am Flight 103, the FAA has initiated an accelerated research program to determine the minimum size explosive charge that would destroy a commercial aircraft and to address the feasibility of increasing aircraft tolerance to such charge sizes. This program, the Aircraft Hardening Program, is supported with government and industry expertise in the areas of explosive effects, aircraft vulnerability, and aircraft design.
Transforming apparatus that has developed into a successfully working laboratory system into a system that is ready, or nearly ready for production, distribution and general use is not always accomplished in a cost effective or timely fashion. Several design elements must be considered interactively during the planning, construction, use and servicing of the final production form of the system. The basic design elements are: Operating Specifications, Reliability Factors, Safety Factors, Precision Limits, Accuracy Limits, Uniformity Factors, Cost Limits and Calibration Requirements. Secondary elements including: Human Engineering, Documentation, Training, Maintenance, Proprietary Rights, Protection, Marketing, Replacement of Parts, and Packing and Shipping must also be considered during the transition.
A number of nuclear techniques have been utilized or considered for detecting concealed explosives. Theses technique range form those utilizing multi-energetic x-rays to those relying on high energy photons or neutrons. The physical principles behind these methods are reviewed. Each technique is critically examined, in view of its ability to distinguish explosive materials form other common materials of similar composition. The suitability of each method for use in airport security is also assessed.