Spin-Acceleration Inertial Igniters for Drop-Safe Initiation
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Solution Overview
Problem
Current inertial igniters fail to provide safe non-initiation during accidental drops from high heights, such as 40 feet, due to the inability to differentiate between high-height drop-induced decelerations and firing setback accelerations, leading to potential accidental ignition.
Innovation Solution
Design of inertial igniters that utilize simultaneous detection of setback induced linear and spin accelerations to arm and initiate the device, ensuring safe non-initiation during high-height drops and reliable ignition during firing, using mechanisms like preloaded tensile and compressive springs to manage striker mass movement and pyrotechnic initiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inertial igniters are designed to respond to high deceleration levels (exceeding 18,000 Gs) to ensure reliable initiation during firing, then initiation reliability is improved, but safety during accidental high-height drops deteriorates
Solution Approach 1:
The deceleration detection function is segmented into two independent detection axes: a linear acceleration sensor and a spin acceleration sensor. The igniter only activates when both sensors simultaneously detect their respective threshold decelerations, which occurs during firing but not during accidental drops. This segmentation allows the system to maintain high initiation reliability while achieving safety during transportation and loading.
2Device complexity
If inertial igniters use a single deceleration threshold mechanism, then device complexity is reduced, but the ability to differentiate between firing and accidental drop conditions deteriorates
Solution Approach 1:
The detection mechanism is segmented into two independent sensor systems: a linear acceleration sensor and a spin acceleration sensor. Each sensor monitors a different physical quantity along a different axis. This segmentation enables precise differentiation between firing conditions (which produce both linear and spin deceleration) and accidental drops (which produce only linear deceleration), while maintaining relatively simple device architecture.
Solution Approach 2:
The detection system transitions from single-dimensional linear acceleration measurement to two-dimensional measurement by adding spin acceleration detection. This dimensional expansion allows the system to distinguish between different types of deceleration events: firing produces deceleration in both linear and rotational dimensions, while accidental drops produce deceleration only in the linear dimension, enabling accurate condition differentiation.
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 inertial igniters to safely withstand drops from up to 40 feet with decelerations of 18,000 Gs while ensuring reliable ignition during firing, reducing the risk of accidental initiation and optimizing space and volume in munitions.
Implementation Method 1
an inertial igniter that is armed by a linear acceleration and is initiated by a spin acceleration
Implementation Method 2
an inertial igniter that is armed by a linear acceleration and is initiated by a spin acceleration
Implementation Method 3
simultaneous linear and rotary acceleration (deceleration) operated mechanical mechanisms
Data Source
AI summary
An apparatus actuatable under a rotary acceleration having a predetermined duration and magnitude. The apparatus including: a body having a first channel and a second channel, the second channel being disposed radially offset from the first channel; a mass disposed in the first channel, the mass having an arm disposed at a first end of the mass and the arm being rotatable from a first position in which the arm cannot move within the second channel to a second position in which the arm can move inside the second channel; a first biasing spring member having a first end connected to the body and a second end connected to the arm such that when the arm is subjected to the rotary acceleration greater than the predetermined duration and magnitude, the arm is biased to rotate from the first position to the second position; wherein the mass is connected to the arm such that the mass moves in the first channel and the arm moves in the second channel when the arm is biased into the second position.