Arm-fire Device Ignition Control via Acceleration Sensing
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Solution Overview
Problem
Existing arm-fire devices for rockets are prone to accidental ignition and lack reliable acceleration sensing, especially in multi-stage rockets and cold launching systems, which can lead to unstable operation and increased risk of accidental ignition due to sensitivity to external impacts and pressure changes.
Innovation Solution
An arm-fire device incorporating a capacitor, an acceleration switch with a stator and proof mass design, and a through bulkhead initiator, where the acceleration switch generates an operation signal upon sensing predetermined acceleration, and the controller discharges the capacitor to produce a firing signal only when both signals are present, ensuring controlled ignition and minimizing accidental ignition risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high voltage initiator is used to prevent accidental ignition, then safety is improved, but the device complexity increases
Solution Approach 1:
The arm-fire device is divided into distinct functional modules: acceleration sensing module, capacitor charging module, and initiator firing module. This segmentation allows each module to be optimized independently while maintaining overall system safety and reducing complexity through modular design.
Solution Approach 2:
The capacitor is charged in advance during the arming phase, before the actual firing decision is made. This preliminary action separates the energy storage function from the firing control function, allowing the initiator to remain inactive until both acceleration conditions are met, thereby preventing accidental ignition while simplifying the control logic.
2Reliability
If an acceleration switch is added to sense rocket movement, then accidental ignition prevention is improved, but the device complexity increases
Solution Approach 1:
The acceleration switch uses a MEMS-based proof mass and electrode plate system that detects acceleration through electrostatic force changes rather than traditional mechanical switches. This substitution reduces mechanical wear and contact issues while integrating the sensing function into the existing electronic architecture of the arm-fire device.
Solution Approach 2:
The proof mass structure serves multiple functions: it acts as the sensing element for acceleration detection, provides mechanical support for the electrode plates, and contributes to the overall structural integrity of the device. This multi-functionality reduces the total component count and simplifies the device architecture.
3Device complexity
If the arm-fire device is miniaturized, then the device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The electrode plates are nested within the housing structure, with the proof mass positioned between them. The capacitor is integrated into the same housing, with its terminals connected to the controller. This nested arrangement maximizes space utilization and reduces the overall device footprint while maintaining adequate clearance for manufacturing tolerances.
Solution Approach 2:
The design uses standardized component values and dimensions that can be manufactured with conventional precision capabilities. The capacitor capacity, electrode plate spacing, and proof mass dimensions are selected to provide adequate margins for manufacturing variation, allowing miniaturization without excessively tight tolerances.
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 enhances the reliability and safety of rocket propulsion systems by reducing accidental ignition, improving acceleration sensing accuracy, and allowing for precise control over ignition timing, while also enabling miniaturization and improved durability of the arm-fire device components.
Implementation Method 1
a capacitor charged by an arming signal; a controller electrically connected with the capacitor and the acceleration switch, controlling the firing signal, and a through bulkhead initiator provided with an ignition portion installed in a space separated by a bulkhead and configured to be electrically connected with the controller to ignite the ignition portion if the firing signal is transferred thereto
Implementation Method 2
an acceleration switch for generating an operation signal when the acceleration is sensed more than a predetermined acceleration
Data Source
AI summary
An arm-fire device comprises a capacitor charged by an arming signal; an acceleration switch for generating an operation signal if an acceleration more than a predetermined acceleration is sensed; a controller electrically connected with the capacitor and the acceleration switch, controlling generation of a firing signal; and a through bulkhead initiator provided with an ignition portion installed at a space separated by a bulkhead and configured to be electrically connected with the controller to ignite the ignition portion if the firing signal is transferred thereto, wherein the controller discharges the capacitor to generate the firing signal when the operation signal and a launching signal, which is applied from outside, are all sensed in a state that the capacitor is charged. The arm-fire device is applied to a multi-stage rocket, etc., whereby the probability of accidental ignition may be lowered.