Self-extinguishing Solid Propellant via Surfactant Negative Pressure Dependence
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Solution Overview
Problem
Solid rocket motors lack a reliable method to extinguish and re-light propellants, as conventional shut-off processes are complex and often destructive, and natural extinguishment is considered difficult or impossible, limiting their control and efficiency in applications like divert and attitude control systems (DACS) for missile defense.
Innovation Solution
The development of self-extinguishing composite propellant compositions that include an oxidizing agent, binder, and surfactant, which exhibit a negative pressure dependence in burning rate, allowing for extinguishment without depressurization by reaching a cutoff pressure, and can be tailored for specific applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional shut-off processes are used to stop propellant burning, then the propellant can be extinguished, but the process requires complicated rapid depressurization techniques and causes severe structural damage to the motor
Solution Approach 1:
The propellant composition itself provides the extinguishment mechanism through its inherent chemical properties. The surfactant-modified propellant automatically stops burning when combustion chamber pressure drops below a threshold, eliminating the need for external depressurization systems or complex shutdown mechanisms. The propellant serves its own extinguishment function through the negative pressure dependence of its burning rate.
Solution Approach 2:
The invention changes the burning rate characteristics of the propellant by incorporating surfactants, creating a negative pressure dependence relationship. This parameter change allows the burning rate to naturally decrease as pressure decreases, enabling automatic extinguishment at lower pressures without requiring active control systems or complex shutdown procedures.
2Reliability
If physical rupture of the case is used to depressurize the combustion chamber, then the propellant can be extinguished, but it causes uncontrolled burn-off of the remaining solid propellant and severe structural damage
Solution Approach 1:
The propellant composition automatically extinguishes itself through its inherent chemical properties when pressure drops below a threshold, eliminating the need for destructive case rupture. The surfactant-modified propellant naturally stops burning through its negative pressure dependence, preventing both uncontrolled burn-off and structural damage associated with forced depressurization methods.
Solution Approach 2:
The invention converts the naturally occurring pressure drop during combustion into a beneficial extinguishment mechanism. Instead of requiring destructive case rupture to achieve depressurization, the system utilizes the natural pressure decrease to trigger automatic extinguishment, transforming a potentially harmful process into a controlled and beneficial shutdown mechanism.
3Ease of manufacture
If solid rocket motors are used for DACS applications requiring multiple firings, then they offer ease of manufacture and structural simplicity, but they lack the ability to control or alter thrust characteristics after ignition
Solution Approach 1:
The invention introduces dynamic thrust control capability to solid rocket motors through surfactant-modified propellant chemistry. The burning rate becomes dynamically responsive to pressure changes, allowing thrust characteristics to be controlled during operation. This enables multiple firings and trajectory adjustments by manipulating combustion chamber pressure, transforming the previously static thrust profile into a dynamically controllable parameter.
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
This solution enables solid rocket motors to be more straightforward and efficient, allowing for controlled shut-off and re-lighting, reducing structural damage and improving thrust management, particularly in DACS applications where multiple firings and trajectory adjustments are necessary.
Implementation Method 1
The addition of a suitable surfactant has been found by the Present Inventors to provide the solid propellant the unexpected property of being 'self-extinguishing'. 'Self-extinguishing' as defined herein refers to the burning rate as a function of pressure including a negative pressure dependence portion, wherein the burning rate in the negative pressure dependence portion decreases with increasing pressure until a cutoff pressure is reached which results in extinguishment of the solid composite propellant.
Implementation Method 2
The solid composite propellant can also comprise at least one catalyst that modifies the burning rate of the solid composite propellant.
Implementation Method 3
The solid propellant is normally in the form of a propellant grain placed within the interior of the rocket motor (e.g. in the combustion chamber) and burned to produce hot gases which, in turn, exit through the throat and nozzle of the rocket motor at high velocity to provide thrust which propels the rocket in the opposite direction.
Data Source
AI summary
Solid composite propellant compositions include at least one oxidizing agent, at least one binder, and at least one surfactant. The surfactant provides the solid propellant the property of being “self-extinguishing”, where the burning rate of the solid composite propellant as a function of pressure includes a negative pressure dependence portion, wherein the burning rate in the negative pressure dependence portion decreases with increasing pressure until a cutoff pressure is reached which results in extinguishment of the solid composite propellant. The solid composite propellant can also include at least one catalyst that modifies the burning rate of the solid composite propellant. Solid composite propellants can be extinguished without the need for depressurization by reaching a cutoff pressure, and with a tailored burning rate.