Compact Inertial Igniter for High-G Munitions
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Solution Overview
Problem
Existing inertial igniters for thermal batteries are too large and not suitable for small, low-power applications, particularly in gun-fired munitions experiencing high G accelerations, necessitating a compact and reliable ignition system that distinguishes between accidental and intended activation events.
Innovation Solution
A compact inertial igniter design featuring a base with a striker mass rotatably connected through a rotatable connection, utilizing a rotation prevention mechanism with a retaining member and blocking member to ensure ignition only upon a predetermined acceleration event, allowing the striker mass to rotate and impact a pyrotechnic material for ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing inertial igniter designs are used, then safety requirements are met by distinguishing accidental drops from firing acceleration, but the igniter size becomes too large for small and miniaturized thermal batteries
Solution Approach 1:
The inertial igniter is divided into separate functional modules: a striker assembly with pyrotechnic material, a housing with acceleration sensing mechanism, and a release mechanism. This segmentation allows each component to be optimized independently and packed more efficiently, reducing overall volume while maintaining safety functions
Solution Approach 2:
The striker mass is positioned within the housing such that it rotates about a pivot point located in the housing wall. The pyrotechnic material is contained within the striker assembly, and the release mechanism is integrated into the housing structure. This nested arrangement eliminates the need for separate mounting structures and reduces the igniter's overall footprint
2Volume of moving object
If the igniter is designed to be compact for miniaturized applications, then volume requirements are met, but reliability in high-G gun-fired munitions applications may be compromised
Solution Approach 1:
The design parameters of the striker mass (mass, dimensions, moment of inertia) and the pyrotechnic material (sensitivity, composition) are specifically optimized for high-G applications. The acceleration threshold for striker release is calibrated to distinguish between accidental impacts and intentional firing events, ensuring reliable operation in gun-fired munitions while maintaining compact dimensions
Solution Approach 2:
The pyrotechnic material is pre-positioned in direct contact with the striker mass, and the release mechanism is pre-set to trigger at the appropriate acceleration threshold. This preliminary arrangement ensures that upon activation, ignition occurs immediately without requiring additional mechanical travel or complex sequencing, thereby maintaining reliability in a compact configuration
3Reliability
If a rotation prevention mechanism with blocking member is added to ensure safety, then accidental ignition is prevented, but device complexity increases
Solution Approach 1:
The rotation prevention mechanism is merged with the striker assembly structure. The blocking member is integrated into the housing wall where it normally resides, and the retaining member is combined with the striker mass or its mounting structure. This merging eliminates the need for separate rotation prevention components while maintaining the safety function of preventing accidental ignition
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a smaller, more reliable inertial igniter that meets safety requirements by preventing accidental ignition and ensuring ignition only during high acceleration events, reducing the overall size and volume of the thermal battery assembly.
Implementation Method 1
a striker mass rotatably connected to the base through a rotatable connection... allowing the striker mass to rotate and impact a pyrotechnic material for ignition
Data Source
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AI summary
A method for igniting a thermal battery upon a predetermined acceleration event. The method including: rotatably connecting a striker mass to a base; aligning a first projection on the striker mass with a second projection on the base such that when the striker mass is rotated towards the base, the first projection impacts the second projection; and preventing impact of the first and second projections unless the predetermined acceleration event is experienced.