Variable Diameter Nozzle for Slow Cook Off Rocket Igniter
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Solution Overview
Problem
Existing rocket motor propulsion systems face issues with unintended ignition and shrapnel generation during slow cook off, leading to potential damage and uncontrolled missile propulsion, and existing solutions often result in non-reusable systems with uncontrolled gas venting.
Innovation Solution
A gas generating propulsion system with an auto igniter and a variable diameter nozzle, where the nozzle's cross-sectional area can be adjusted to manage pressure and thrust, incorporating an auto igniter between the igniter and main propellant to control ignition and a valve to regulate gas discharge, ensuring safe operation during transport and deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the throat diameter is increased to vent gases during slow cook off, then the risk of shrapnel generation and unintended propulsion is reduced, but the thrust generation capability is diminished
Solution Approach 1:
The patent employs a movable valve that can dynamically adjust the throat diameter between two states: a first position for normal operation with restricted flow to generate thrust, and a second position for slow cook off safety with increased flow area to vent gases. This dynamic reconfiguration allows the system to adapt its geometry based on operational requirements, resolving the contradiction between thrust generation and slow cook off safety.
2Reliability
If existing venting methods are used during slow cook off, then gas pressure is reduced, but the system becomes non-reusable and gas is vented in an uncontrolled manner
Solution Approach 1:
The patent replaces traditional mechanical venting methods (such as burst discs or welded joints that fail permanently) with a controllable valve mechanism that can be reset and reused. The valve provides controlled gas discharge through a defined pathway, allowing the propulsion system to maintain structural integrity and functionality after slow cook off events, thereby enabling reuse while maintaining reliable protection.
3Power
If the valve restricts gas discharge to generate thrust, then pressure increase within the housing generates thrust, but the risk of housing rupture increases during normal operation
Solution Approach 1:
The valve dynamically adjusts between restricted flow (first position) for thrust generation and increased flow area (second position) for pressure relief during slow cook off. This dynamic control allows the system to operate at high pressure for thrust while providing a safety release mechanism that prevents housing rupture, resolving the contradiction between thrust generation and housing integrity.
Solution Approach 2:
The valve acts as an intermediary control element between the propellant combustion chamber and the exhaust nozzle. It mediates the flow of combustion gases, allowing controlled restriction for thrust generation while providing a regulated pathway for pressure relief, thereby preventing uncontrolled housing rupture while maintaining effective thrust production.
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 system effectively prevents unintended propulsion and shrapnel expulsion during slow cook off, allowing the rocket motor to remain intact and potentially reusable, with controlled gas discharge and reduced pressure to prevent system rupture.
Implementation Method 1
The auto igniter ignites the main propellant charge at a lower temperature than its auto ignition temperature
Implementation Method 2
When the propellant is exposed to temperatures above about 200° C., such as in a burning warehouse, the explosive composition undergoes a rapid, exothermic decomposition that may lead to a violent reaction or explosion
Implementation Method 3
As the propellant burns, a copious volume of gas is generated along with heat that expands the volume of generated gas
Implementation Method 4
As this gas is expelled through a nozzle, thrust is generated. The thrust may be used to propel a missile to a target
Data Source
AI summary
A gas generating propulsion system includes an igniter containing an igniter propellant and an auto igniter. A rocket motor is coupled to the igniter and has a housing containing a main propellant, a rocket motor throat and a nozzle. A release port extends through a portion of the rocket motor. This gas release port has a variable diameter through bore in fluid communication with the main propellant. In this way, the through bore has a variable area that forms an unobstructed open area with a cross-section effective to discharge gas generated by the main propellant such that a pressure increase within the housing remains below a safety value for the housing.