Laser Ignitability Programs Being Conducted at the Indian Head Division Naval Surface Warfare Center

Abstract

The Indian Head Division, Naval Surface Warfare Center (IHDIV, NSWC) has been involved with the laser initiation of energetic materials over the past 18 years. Specifically, the IHDIV, NSWC has been leading efforts in the basic research into laser ignitability of various energetic materials, developing cartridges and Cartridge Actuated Devices (CADs) incorporating this research, and ultimately implementing these new devices into a variety of aircrew escape system and weapon system applications. This paper presents an overview of one of these on-going programs: the effort to determine the laser ignitability characteristics of the MTV (Magnesium Teflon Viton) initiation material used in Mk 117 Mod 0 Jet Assisted Take-Off device. This example highlights one of the current efforts being conducted at the IHDIV, NSWC and supplements the previously presented technical papers offered at various the AIAA Conferences and other related symposia. The laser ignition capability is currently supporting several Department of Defense CAD/PAD programs. This paper will highlight the efforts underway to support an effort to determine the laser ignitability characteristics of the MTV (Magnesium Teflon Viton) and NOSIH-AA6 double base propellant used in the Mk 117 Mod 0 Jet Assisted Task-Off (JATO) device. This investigation is one phase of a larger investigation into several anomalies associated with this JATO and the BQM-74E Aerial Target system. FIELDED SYSTEM AND INVESTIGATION: BACKGROUND: This paper presents the IHDIV, NSWC current capability to study the laser ignition characteristics of various energetic materials used in various CAD/PAD (Cartridge Actuated Device/Propellant Actuated Device) applications. Determining the laser ignition characteristics of an energetic material greatly enhances the overall understanding of how this material reacts to a stimulus and supplements the standard mechanical, chemical, and ignition test parameters generated when an energetic material is studied. The IHDIV, NSWC approach to evaluating the laser ignition characteristics of energetic materials utilizes a 400 Watt Coherent, Inc. carbon dioxide (CO2) laser (10.6 micrometer wavelength) with a developed test methodology to generate two critical energetic material characteristics: a 50% ignition threshold level and identifying the time to first light (or ignition delay). The details of the test approach will follow. Photo 1: BQM-74E Aerial Target Launch The U.S. Navy has utilized the BQM-74E Aerial Target (Photo (1)) extensively for various training and weapon system tests over the past several years. The BQM-74E Target utilizes an on-board jet engine to provide over 200 pounds of thrust to sustain flight. The dual Mk 117 Mod 0 JATOs provide a combined thrust of approximately 7,000 pounds to launch the target both from land-based and from shipboard platforms. 1 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit 10 13 July 2005, Tucson, Arizona AIAA 2005-3517 This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Recently, the Navy has experienced several anomalies in which the JATO devices have either failed to ignite or have not provided continuous sustained thrust shortly after ignition. In these cases, the asymmetric thrust resulting from only one successful JATO have resulted in the complete loss of the aerial target (Photos (2), (3), and (4)). These photos were taken during a 3 May 2004 incident at the Naval Air Warfare Center – Weapons Division, Point Mugu, CA. e r Photo 5: JATO Initiator Configuration LASER IGNITABILITY TEST METHODOLOGY: In general, the test methodology adopted for all of the IHDIV, NSWC laser ignitability programs is very similar. Utilizing the carbon dioxide laser previously described, a mask with a 0.10-inch diameter hole in the center is used to limit the generated laser beam (normally the beam is 1.0-centimeters in diameter at the 1/e points). This 0.10inch beam delivers a controlled thermal input to the energetic material samples. For the NOSIH-AA-6 propellant, a series of 0.25-inch cube propellant samples were used. For the MTV ignition material, a series of short, extruded cylinders were used. All of these samples are centered in the test chamber in brass holders. These samples were prepared specifically for this investigation.