Thermal Battery Reserve Power for Munitions
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Solution Overview
Problem
Thermal batteries used in munitions face challenges in size reduction due to insulation needs and susceptibility to high centrifugal forces during spinning, requiring external power sources for ignition, and struggling to differentiate between intended firing and accidental events without external sensors or power.
Innovation Solution
Integration of a thermal battery with an inertial igniter and a low leakage capacitor, where electrical energy is generated and rapidly stored, minimizing the need for thermal insulation and allowing the power source to be small and self-sufficient, using existing technologies to ensure reliability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If thermal battery size is reduced, then munition size is reduced, but thermal insulation requirements increase due to high centrifugal forces during spinning
Solution Approach 1:
The thermal battery is pre-charged to a higher state of charge before munition launch. This preliminary energy storage allows the battery to withstand the stress of high centrifugal forces during spinning without requiring excessive thermal insulation, as the battery is designed to deliver power in a specific time window after launch when centrifugal forces are managed.
2Reliability
If external power sources are added for ignition, then ignition reliability is improved, but device complexity and volume increase
Solution Approach 1:
The thermal battery system is designed to be self-igniting through pyrotechnic initiation. The battery contains its own pyrotechnic igniter that activates the electrochemical reaction without requiring external power sources or decision circuitry. This self-service approach maintains ignition reliability while minimizing device complexity and volume.
3Measurement precision
If external sensors are added to differentiate firing events, then event differentiation accuracy is improved, but device complexity and power requirements increase
Solution Approach 1:
The thermal battery incorporates an inertial igniter that automatically differentiates between firing events and accidental events using inertial forces. The igniter is designed to activate only under the specific acceleration conditions of munition launch, eliminating the need for external sensors or power sources for event differentiation. This self-service mechanism maintains measurement precision while minimizing device complexity.
4Duration of action of moving object
If thermal insulation is increased, then thermal battery operational duration is extended, but device volume and weight increase
Solution Approach 1:
The thermal battery is pre-charged to a higher state of charge before launch, extending its operational duration without requiring increased thermal insulation volume. The battery's electrochemical design and charge management allow it to maintain power output for the required duration while keeping the insulation volume optimized for the munition's size constraints.
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
Enables the creation of compact, reliable, and cost-effective reserve power sources that can withstand high firing accelerations and long shelf life without external power, effectively differentiating firing events from accidental ones, and maintaining operation over extended periods.
Implementation Method 1
These batteries incorporate pyrotechnic heat sources to melt the electrolyte just prior to use in order to make them electrically conductive and thereby making the battery active
Implementation Method 2
The inertial igniters operate based on the firing acceleration. Such mechanical means include, for example, the impact pins to initiate a percussion primer or impact or rubbing acting between one or two part pyrotechnic materials
Data Source
AI summary
A method for producing electrical energy in a munition includes; initiating a thermal battery contained within the munition to generate electrical energy; dumping the electrical energy generated by the thermal battery into an electrical energy storage device before the thermal battery becomes inactive; and using the stored electrical energy in the electrical energy storage device over a period of time. The initiation device can be an inertial igniter, the electrical energy storage device can be a capacitor and the thermal battery, initiation device and electrical energy storage device can be configured such that the initiation device and electrical energy storage device sandwich the thermal battery.