Shape Memory Polymer Venting for Solid Rocket Motor Safety
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Solution Overview
Problem
Current containment devices for solid rocket motors (SRMs) are insufficient in preventing unintentional ignition or explosion due to heat and mechanical shock, necessitating the development of insensitive munitions (IM) that do not detonate under non-intended conditions, and existing venting systems are not durable or effective enough to prevent over-pressurization.
Innovation Solution
The use of shape memory polymers (SMPs) or SMP composites that maintain a seal at normal temperatures but revert to their memory shape at critical temperatures to vent pressurized containers, preventing ignition or explosion by releasing containment, thereby ensuring IM compliance and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If containers are sealed to protect ammunition from the outside environment, then protection from environmental contamination is improved, but the ability to vent generated gasses during cook-off deteriorates
Solution Approach 1:
The plug material undergoes a parameter change from solid to liquid or gas at a predetermined temperature, transforming the sealing mechanism from a permanent seal to a temperature-responsive venting system. This allows the container to maintain密封ity at normal temperatures while automatically venting at elevated temperatures.
Solution Approach 2:
The plug is designed to undergo phase transition (melting or vaporization) at a specific temperature threshold. This phase change enables the plug to automatically open the vent passage when the container experiences cook-off conditions, converting the harmful pressure buildup into a controlled venting process.
2Object-generated harmful factors
If traditional venting systems are used, then venting capability is provided, but durability and effectiveness in preventing over-pressurization are insufficient
Solution Approach 1:
The venting system is self-activating through the use of temperature-responsive material that automatically melts or vaporizes at the predetermined temperature. No external actuation mechanism is required, eliminating mechanical failure points and enhancing reliability. The system serves itself by using the thermal energy present in the cook-off scenario to trigger the venting action.
Solution Approach 2:
The patent replaces traditional mechanical venting systems (which rely on moving parts, springs, or latches) with a material-based solution where the plug's physical state change directly controls the vent passage. This substitution eliminates mechanical complexity and improves durability by relying on inherent material properties rather than mechanical mechanisms.
3Object-affected harmful factors
If containers are designed for IM compliance, then safety under unintentional stimuli is improved, but the complexity of meeting multiple specifications increases
Solution Approach 1:
The temperature-responsive plug serves multiple functions simultaneously: it provides environmental sealing during normal storage, acts as an automatic venting mechanism during cook-off, and contributes to IM compliance by preventing explosive pressure buildup. This multi-functionality reduces the need for separate systems for each requirement.
Solution Approach 2:
The invention extracts the venting function from complex mechanical systems and embeds it directly into the container closure structure through the use of temperature-responsive material. This integration simplifies the overall system while maintaining IM compliance capabilities.
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 SMP-based venting system effectively prevents inadvertent ignition or explosion of SRMs by allowing controlled venting when temperatures exceed the transition temperature, enhancing safety and compliance with IM standards while maintaining structural integrity and ease of operation.
Implementation Method 1
shape memory polymers (SMPs) or SMP composites that maintain a seal at normal temperatures but revert to their memory shape at critical temperatures to vent pressurized containers
Data Source
AI summary
The disclosed device primarily consists of a band, ring, or other piece of shape memory polymer (SMP) or SMP composite in various embodiments that allows or disallows containment. When the SMP reaches its transition temperature (Tg) the SMP provides the means for releasing containment of the pressurized material so as to prevent ignition or explosion of hazardous material. At normal operating temperatures, the SMP is in a deformed shape maintaining an environmental seal to protect the contents of the container. When environmental conditions cause the SMP or SMP composite to exceed its Tg, specified by the operating requirements, the SMP returns to its memory shape in a controlled geometry, rather than simply melting. The return of the SMP to its memory shape causes the venting of the container in different manners depending on which embodiment is utilized.