Composite Solid Propellant Bimodal Oxidizer Pressure Sensitivity
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Solution Overview
Problem
Composite propellants for rocket engines exhibit high sensitivity to pressure variations, leading to unstable engine operation and mechanical stresses due to fluctuations in combustion rate.
Innovation Solution
A composite solid propellant formulation featuring a crosslinked polyol polymer binder, bimodal size distribution of inorganic perchlorate oxidizing filler, aluminum or aluminum compound reducing filler, and copper oxide (CuO) as a ballistic catalyst, which reduces the pressure exponent in Vieille's law, thereby stabilizing the combustion rate and reducing pressure-related fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional composite propellant formulations are used, then high combustion rate can be achieved, but the combustion rate exhibits high sensitivity to pressure variations
Solution Approach 1:
The patent applies parameter changes by implementing a bimodal particle size distribution for ammonium perchlorate oxidizer particles, with a first population having D50 between 150-250 μm and a second population having D50 between 5-20 μm. This specific size distribution parameter modification reduces the pressure exponent from typical values of 0.3-0.5 to below 0.2, thereby reducing pressure sensitivity while maintaining high combustion rate through the synergistic effect of the two particle size populations
Solution Approach 2:
The patent uses composite materials by combining ammonium perchlorate particles with bimodal size distribution, aluminum reducing filler, crosslinked polyol binder, and copper oxide ballistic catalyst in specific proportions. This composite formulation creates a propellant system where the interaction between different sized oxidizer particles and the catalyst produces stable combustion characteristics across varying pressure conditions while sustaining high burn rates
2Speed
If iron oxide is used as a ballistic catalyst, then combustion rate increases, but pressure sensitivity remains high
Solution Approach 1:
The patent replaces iron oxide catalyst with copper oxide and combines it with a bimodal oxidizer particle size distribution. This parameter change in both the catalyst material and the oxidizer morphology achieves a pressure exponent below 0.2, simultaneously increasing combustion rate and reducing pressure sensitivity, overcoming the limitations of iron oxide-based formulations
3Ease of manufacture
If uniform particle size distribution is used, then manufacturing is simplified, but combustion stability under pressure variations deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the oxidizer particle population into two distinct size classes: a first population with D50 of 150-250 μm comprising 50-60% by mass, and a second population with D50 of 5-20 μm comprising 7-17% by mass. This segmented approach creates complementary combustion characteristics where larger particles provide structural stability and smaller particles enhance surface area for catalytic action, achieving pressure-insensitive combustion while remaining manufacturable through conventional mixing processes
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 use of CuO as a ballistic catalyst in the propellant with a bimodal size distribution of oxidizing filler significantly reduces the pressure exponent, resulting in a more stable engine operation, allowing for optimized motor architectures with reduced mechanical stresses and increased reliability.
Implementation Method 1
a ballistic catalyst comprising particles of copper oxide CuO. The incorporation of a CuO copper oxide ballistic catalyst within the composite solid propellant formulation described above allows to jointly achieve a high burn rate associated with a significant reduction in the pressure exponent
Implementation Method 2
an oxidizing filler comprising particles of inorganic perchlorate... and a reducing filler comprising particles of aluminum and/or of an aluminum compound
Implementation Method 3
Composite propellants are known for rocket propulsion and generally implement a binder in which energetic charges are dispersed. A ballistic catalyst can be added to these compositions in order to increase the rate of combustion and the thrust produced
Data Source
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AI summary
The present invention relates to a composite solid propellant comprising a binder comprising a crosslinked polyol polymer in which are present: - an oxidizing charge comprising inorganic perchlorate particles, the oxidizing charge having a bimodal size distribution with (i) a first set of inorganic perchlorate particles having a first size D50 between 150 µm and 250 µm and present at a rate of 50% to 60% by mass in the composite solid propellant, and (ii) a second set of inorganic perchlorate particles having a second size D50 between 5 µm and 20 µm and present at a rate of 7% to 17% by mass in the composite solid propellant, - a reducing charge comprising aluminum particles and/or an aluminum compound, and - a ballistic catalyst comprising copper oxide particles CuO.