Thermal Trigger with Inertial Lockout for Missile Safety
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Solution Overview
Problem
Missiles and rockets can ignite explosively when heated due to the retention of strength by their casings at elevated temperatures, posing a risk of detonation and damage or harm in fire scenarios.
Innovation Solution
A thermal trigger with an integrated out-of-line lockout device that disarms upon acceleration, using a shape memory trigger and inertial mass to prevent the firing pin from triggering explosive charges, thereby preventing detonation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermal trigger is used to prevent detonation by venting explosive materials, then safety during fire is improved, but the risk of accidental discharge due to vibration or shock remains
Solution Approach 1:
An inertial mass is introduced as an intermediary element between the thermal trigger mechanism and the external environment. This inertial mass acts as a mediator that filters out harmful vibrations and shocks while allowing the thermal trigger to function properly during fire conditions. The inertial mass absorbs and dampens mechanical disturbances that could cause accidental discharge, while not interfering with the thermal activation process.
Solution Approach 2:
The inertial mass is pre-positioned and pre-configured within the thermal trigger assembly before deployment. This preliminary action ensures that the inertial mass is already in place to counteract vibrations and shocks during critical operations, preventing accidental discharge before it can occur. The system is prepared in advance with the inertial mass already integrated into the trigger mechanism.
2Speed
If the thermal trigger remains armed during flight vibrations, then responsiveness to fire conditions is maintained, but false triggering from vibration occurs
Solution Approach 1:
The inertial mass serves as a mediator that selectively filters mechanical disturbances. It allows thermal signals to pass through to the trigger mechanism while blocking vibrational and shock signals that could cause false triggering. This intermediary element enables the system to respond quickly to fire conditions while maintaining reliability during flight vibrations.
Solution Approach 2:
The system changes the physical parameters of the trigger mechanism by introducing an inertial mass with specific mass and damping characteristics. This parameter change allows the trigger to remain sensitive to thermal conditions while becoming insensitive to mechanical vibrations within a certain frequency and amplitude range, thus preventing false triggering during flight.
3Speed
If the firing pin is allowed to move freely for quick response, then fire detection response is improved, but accidental discharge from shock increases
Solution Approach 1:
The inertial mass is positioned as an intermediary between the firing pin and external shock sources. It allows the firing pin to move freely in response to thermal activation while blocking shock-induced movement. The inertial mass absorbs shock forces that would otherwise cause accidental discharge, while not impeding the rapid movement of the firing pin when thermal conditions are met.
Solution Approach 2:
The inertial mass is pre-positioned to protect the firing pin mechanism before shock events occur. This preliminary protective action ensures that when shocks or vibrations occur during flight, the inertial mass is already in place to prevent accidental discharge, while allowing the firing pin to respond quickly to fire conditions when needed.
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 effectively prevents detonation of missiles or rockets during fires by ensuring the thermal trigger is disarmed upon acceleration, allowing for controlled burning rather than explosive detonation, thereby reducing risk to personnel and equipment.
Implementation Method 1
A thermal trigger with an integrated out-of-line lockout device that disarms upon acceleration, using a shape memory trigger and inertial mass to prevent the firing pin from triggering explosive charges
Implementation Method 2
The lockout device is configured to move a first lockout ball into a notch of the firing pin to disarm the thermal trigger
Data Source
AI summary
A device includes a thermal trigger having a firing pin, where the thermal trigger is configured to move the firing pin in response to an elevated temperature. The device also includes an out-of-line lockout device configured to disarm the thermal trigger in response to acceleration of the lockout device. The lockout device is configured to move a first lockout ball into a notch of the firing pin to disarm the thermal trigger. The lockout device could include an inertial mass configured to move the first lockout ball into the notch of the firing pin and a first spring configured to bias the inertial mass in an initial position. The lockout device could also include a second lockout ball configured to move into a position that prevents the inertial mass from returning to the initial position or a dampener configured to slow movement of the inertial mass.