Mechanics of Compounded Explosives for Enhanced Checkpoint Detection

Download Project Report (Phase 2, Year 3)

Project Description

This project is an important element of the overall ALERT strategy to enhance air travel security. Like project R2-A.1, it is focused on checkpoints by contact sampling of carry-on baggage. Existing methods for contact sampling use traps that are applied manually to extract explosives residue from suspicious bags. These traps are then placed in an ion mobility spectrometer (IMS), where any explosive residue is desorbed from the trap when the temperature is raised to roughly 250°C over a period of approximately 8 seconds. Commercial off-the-shelf (COTS) traps are optimized to survive repeated exposure to the IMS desorber, but not to extract residue from the surfaces being interrogated.


Considerable effort has been placed on finding ways to improve the sensitivity, accuracy, and response time of IMS tools. However, these efforts have been undertaken without a great deal of consideration of the essential first step in residue detection, which is extraction of the residue from the surface of interest. This project directly addresses this key step by pursuing rational trap design intended to optimize trap properties leading to superior residue harvesting from surfaces.


This project explores the mechanical properties of compounded explosives, such as C4 and Semtex, for several reasons. First, by understanding the mechanics of these compounds, it is possible to identify the controlling processes in contact sampling, which is a critical step in determining effective detection. Second, understanding the mechanics allows optimization of swab design. Third, understanding the mechanics allows optimization of swabbing protocols. Finally, understanding the contact mechanics and the mechanics under load allows us to develop benign surrogates that can be used in place of live explosives during the development of sampling/detection schemes.


This last capability is significant. At present, the community that is developing contact sampling methods is limited substantially by difficulties associated with obtaining live explosives to use in their laboratories. A benign surrogate that presents the proper key behaviors would dramatically improve the ability of researchers worldwide to develop best-in-class technology to improve trace explosives detection.


The benign surrogate has considerable value as a training aid for TSA operators to reduce false positives.
Biennial Review
Project Leader
  • Stephen P. Beaudoin
    Purdue University

Students Currently Involved in Project
  • Melissa Sweat
    Purdue University
  • Andrew Parker
    Purdue University
  • Hannah Burneau
    West Lafayette Jr./Sr. High