U.S. Navy and the CAD/PAD Joint Progam Office Electronic Time Delay Cartridge: SDI/Scot, Inc. Development Program - 2006 Update

Abstract

The Indian Head Division, Naval Surface Warfare Center (IHDIV, NSWC) is sponsoring a program to design, develop, and implement a family of electronic time delay cartridges for a wide variety of aircrew escape and other cartridge applications throughout the U.S. Department of Defense. Currently, pyrotechnic cartridges, utilizing either a “pressed column” delay or a small column insulated delay (SCID), provide the time delays required for these applications. Implementing an electronic time delay (or digital delay) cartridge, which maintains the form, fit, and function as the current pyrotechnic cartridges while providing longer useful lifetimes and more precise time delays is the primary objective of this program. This paper presents the program approach adopted for this effort and the successes achieved by the selected contractor Special Devices, Inc. and its partner Scot Inc. to develop an electronic time delay cartridge family. BACKGROUND: Cartridge Actuated Devices and Propellant Actuated Devices (CAD/PAD) are utilized for various applications throughout the U.S. military. A cartridge is defined as an energy source utilizing one or more energetic materials. A Cartridge Actuated Device (CAD) is defined as a device releasing cartridge energy to perform a work function. A Propellant Actuated Device (PAD) is defined as a rocket powered device releasing controlled propellant energy to perform a work function. Also, an Aircrew Escape Propulsion Systems (AEPS) is a “PAD” specifically designed for aircrew systems applications. For example, on the F/A-18E/F aircraft, there are over sixty-six (66) cartridges, CADs, and AEPS (Figure (1) on the next page). As shown, the F/A-18E/F utilizes a NACES (Navy Aircrew Common Ejection Seat) ejection seat to provide the pilot escape capability during an emergency situation. In addition, as part of the overall escape system, delay cartridges are utilized to provide optimized timing for all required events. The MC50 Cartridge Actuated Initiator (Photo (1) and Figure (2)) provides supplemental ballistic pressure to the system after a 0.3 second delay. Photo 1: MC50 Cartridge Actuated Initiator For this initiator, ballistic pressure is used as the stimulus to actuate a percussion primer. This primer, in turn, initiates a pyrotechnic column that provides the required 0.3 second time delay before initiating the output charge which provides ballistic pressure to the remainder of the system. Figure 2: MC50 Cartridge Actuated Initiator Schematic 1 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit 8 11 July 2007, Cincinnati, OH AIAA 2007-5133 This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. 43 AIAA/ASME/SAE/ASEE JPC AIAA 2007-5133 Figure 1: F/A-18 E/F CAD/PADs Currently, pyrotechnic cartridges provide the required time delays for a wide range of CAD/PAD systems. These cartridges contain energetic materials that burn in a column at a controlled rate and provide ballistic output after the required system delay has been achieved. These current cartridges fall into two basic categories: “pressed column” type cartridges and “small column insulated delay (SCID)” type cartridges. One example of the “pressed column” type cartridges is the CCU-40A/A (Figure (3)). This cartridge is used on the AV8B aircraft and provides a 0.575 second delay prior to generating ballistic pressure to deploy the ejection seat parachutes. Figure 3: CCU-40A/A Delay Cartridge As shown, the CCU-40A/A delay cartridge is 1.095 inches long and 0.379 inches in diameter. Included in this cartridge are the percussion primer, the delay column, and the output charge that generates the required ballistic pressure for system operation. The CCU-40A/A Delay Cartridge is the smallest of the family of current U. S. Navy and U. S. Air Force delay cartridges or initiators. By maintaining the physical envelope of the CCU-40A/A cartridge, the selected technology can be rapidly implemented into larger cartridge or initiator applications. Thusly, maintaining this physical envelope, while implementing an alternate electronic time delay technology, has been identified as the primary design challenge of this program. A critical secondary design challenge is the packaging of the sub-components that comprise the selected alternate technology. Both of these current types of delay cartridges are expensive to produce, provide imprecise delay times (a tolerance of 25% for the “pressed column” type cartridges and a tolerance of 8% for the SCID-type cartridges are considered acceptable over a standard aircraft environmental temperature range), and require change-out as often as every 18-months during the maintenance cycle for some aircraft applications. Implementing cartridges that replace the pyrotechnical delays with electronic technologies