Secondary Propellant Layer for Rocket Motor Autoignition Control
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Solution Overview
Problem
Conventional solid rocket propellants experience rapid overpressurization and destruction due to autoignition, which is not effectively controlled by existing methods, leading to premature and violent reactions in rocket motors.
Innovation Solution
Incorporating a secondary propellant with a lower autoignition temperature, such as a nitramine like nitroguanidine or cyclotetramethylenetetranitramine, in contact with the main propellant near the motor casing, to manage heat generation and reduce reaction violence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform thin coating of paraxylene polymer is deposited over the propellant grain as an ignition inhibitor, then autoignition is delayed, but the coating does not sufficiently prevent rapid overpressurization and destruction
Solution Approach 1:
The propellant system is segmented into multiple functional layers: a main propellant grain and a secondary propellant layer with different autoignition characteristics. This segmentation allows each layer to perform its specific function - the main propellant provides sustained combustion while the secondary layer controls autoignition timing, preventing premature overpressurization.
Solution Approach 2:
The secondary propellant acts as an intermediary layer between the main propellant and the motor casing. It mediates the heat transfer and combustion process, absorbing and managing the autoignition event in a controlled manner that prevents direct transmission of destructive overpressurization to the motor housing.
2Object-generated harmful factors
If the secondary propellant is positioned in localized contact with the main propellant near the motor casing, then heat generation exceeds heat losses and reaction violence is reduced, but the positioning precision requirement increases
Solution Approach 1:
The secondary propellant is applied with local quality - specifically positioned in contact with the main propellant near the motor casing where heat accumulation is most critical. This localized application provides precisely where it is needed to control autoignition and reduce reaction violence, rather than requiring uniform coverage throughout the entire propellant grain.
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 secondary propellant system effectively delays and moderates the autoignition process, reducing the risk of premature overpressurization and allowing for a controlled burning reaction, thereby preserving the rocket motor hardware.
Implementation Method 1
The autoignition temperature of these propellants is controlled by the decomposition of ammonium perchlorate and the interactions of the decomposition products with the rubbery binder, that lead to porosity in the propellant grain. When autoignition finally occurs, around 450° F., the high surface area of the porous propellant causes rapid overpressurization in the rocket motor leading to destruction.
Implementation Method 2
The autoignition temperature of these propellants is controlled by the decomposition of ammonium perchlorate and the interactions of the decomposition products with the rubbery binder
Implementation Method 3
The secondary propellant is most preferably in physical contact with a localized region of the main propellant near the motor casing. In this regard, most preferably the secondary propellant is in the form of a relatively narrow (i.e., as measured in the elongate axis of the motor casing) strip or ring circumferentially positioned near the motor casing wall in contact with the main propellant. The localized positioning of the strip of secondary propellant provides a critical mass such that heat generation exceeds heat losses.
Data Source
AI summary
Solid propellant systems include a main propellant and a secondary propellant in contact with the first propellant that exhibits autoignition temperatures of at least about 100° F. lower than the autoignition temperature of the main propellant. The secondary propellant of the present invention is most advantageously employed with conventional AP-containing solid propellant formulations as the main propellant, especially formulations containing both AP, an energetic solid, and a binder. In especially preferred forms, the secondary propellant will include a nitramine which is at least one selected from nitroguanidine (NQ), cyclotrimethylene trinitramine (RDX) and cyclotetramethylenetetranitramine (HMX), and a binder which is at least one selected from HTPB, HTPE or glycidyl azide polymer (GAP). Most preferably, the secondary propellant will include a combination of nitramines which includes NQ and one of RDX or HMX.