Description:
TECHNOLOGY AREA(S): Sensors, Weapons
OBJECTIVE: To advance the state of the art of using transient electric field measurements as a test diagnostics tool, specifically for conventional explosive tests.
DESCRIPTION: Signals of various types are of interest to DTRA and DOD for conventional explosives testing.Historically, seismic and acoustic signals have been the primary diagnostic signals of interest in explosives testing, mainly due to the relatively mature understanding of their generation and propagation, their direct applicability to damage potential and forensics, and the variety of sensors available to collect these signals.However, other signals are generated from conventional explosives detonations that are not as well understood.It has long been known that the detonation of conventional explosives produces various types of electric and electromagnetic phenomena [1-3].This innovation challenge involves exploration of these electric and electromagnetic phenomena to determine how they are generated, what the measured signal content represents, and the best method(s) to conduct measurements of electric and electromagnetic phenomena during explosives testing.Past work has identified various general mechanisms by which the detonation of conventional explosives produces electric and electromagnetic phenomena.These mechanisms include early time ionization [4], case breakup, piezoelectric effects [5], lightning in the debris cloud [6], seismoelectric effects, and movement of charge within porous earth materials.These phenomena are related to seismoelectric exploration [7-8] as well as the field of magnetotellurics.Using transient electric field measurements as a test diagnostics tool is attractive because 1) a major advantage of electric methods compared to mechanical methods is that they eliminate the ambiguity that often exists for mechanical signals regarding the travel path and/or propagation velocity (since electric signals propagate at the speed of light, the travel time is insignificant), and 2) valuable data can be collected and analyzed in future tests if it can be determined how the electric field measurements can be related to phenomena of interest [9].An example of a DoD area of interest would be using the electric field measurements to provide information regarding weapon fuse function and other performance forensics.Methods exist today to collect these electric field measurements, ranging from the expensive such as magnetometers and electric field meters with high frequency recording systems to cheaper options such as ground rods connected to a recording system [6], but interpretation of these measurements is an area that requires further investigation.The desired outcome of this innovation challenge is to better understand the electric field measurements recorded during explosive tests and how they can be correlated to phenomena of interest, i.e., bridging the current gap between known/hypothesized mechanisms of electric field generation and the characteristics (magnitude, frequency content, duration, etc.) of the signals generated by these mechanisms.Additionally, a major issue existing today is how to separate out effects from different phenomena and therefore extract useful diagnostic information from an electric field measurement during an explosive test.These electric field measurements currently represent a relatively untapped source of diagnostics which could provide valuable information for future tests if research efforts prove fruitful.
PHASE I: Identify the most important mechanisms that generate transient electric fields during explosive tests, and the signal types and characteristics expected from such mechanisms.Arguments should be testable and supported using methods such as (list is not exhaustive): theoretical derivations, modeling, previous studies, and simple experiments (if cost feasible).The best method or methods to collect transient electric field measurements during explosive tests should also be proposed.The Phase I deliverable is a technical report.
PHASE II: Execute an experimental test program to verify mechanisms identified in Phase I, incorporating the measurement method(s) proposed in Phase I.The experimental test program shall incorporate pre-test predictions.
PHASE III: Since phenomena generated during conventional explosive detonations are also generated in natural events such as earthquakes and volcanic eruptions, there could be significant crossover between this work and other fields once enhanced understanding is obtained.Methods and devices used to measure the electric field generated from conventional explosive detonations could also find applicability in the fields of seiesmoelectric exploration and magnetotellurics.
KEYWORDS: High explosives, electrical field, electrical signals, detonation, diagnostics, signal processing
References:
[1] H. Kolsky, 1954, “Electromagnetic Waves Emitted on Detonation of Explosives”, Nature, Vol. 173, page 77.[2] Fine, J.E., and S.J. Vinci, 1998, “Causes of Electromagnetic Radiation from Detonation of Conventional Explosives: A Literature Survey”, Army Research Laboratory Technical Report ARL-TR-1690. [3] Lauten, W.T., Reinke, R.E., and R.J. Martin, 2006, “The Measurement and Modeling of Earth Electric Signals Produced by Impacts and Detonations” in Proceedings of the 19th Symposium on the Military Aspects of Blast and Shock (MABS 19), Calgary, October. [4] Kuhl, A.L., White, D.A., and B.A. Kirkendall, 2014, “Electromagnetic Waves from TNT Explosions”, Journal of Electromagnetic Analysis and Applications, Vol. 6, pages 280-295.[5] L. Eppelbaum, 2017, “Quantitative Examination of Piezoelectric/Seismoelectric Anomalies from Near-Surface Targets”, Geosciences, Vol. 7, Issues 90. [6] Reinke, R.E., and J.A. Leverette, 1999, “Earth Potential Signals as Diagnostic Tools for High Explosive Structures Testing” in Proceedings of the 9th ISIEMS, Berlin, May. [7] Theriault, R., St-Laurent, F., Freund, F.T., and J.S. Derr, 2014, “Prevalence of Earthquake Lights Associated with Rift Environments”, Seismological Research Letters, Vol. 85, pages 159-178.[8] Russell, R.D., Butler, K.E., Kepic, A.W., and M. Maxwell, 1997, “Seismoelectric Exploration”, The Leading Edge, Vol. 16, Issue 11, page 1611. [9] Soloviev, S.P., Surkov, V.V., and J.J. Sweeney, 2002, “Quadrupolar electromagnetic field from detonation of high explosive charges on the ground surface”, Journal of Geophysical Research, Vol. 107.
