Rocket Fuel Grain Coating for Void-Free Unitary Manufacture
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Solution Overview
Problem
Conventional methods for manufacturing rocket fuel grains, particularly those using cast-molded solid fuels like HTPB, fail to achieve vibration-free, consistent high performance required for rocket propulsion due to issues such as inferior material densities, limited scaling capabilities, poor repair capabilities, mechanical joint limitations, machinability issues, excessive construction waste, and thermal expansion heterogeneity, leading to stress fractures and cracks.
Innovation Solution
The use of additive manufacturing, specifically fused deposition modeling, to create unitary rocket fuel grains with a metallic core encapsulated in an epoxide-based oligomer coating, featuring a concentric beaded structure and vortex inducer channel, which enhances oxidizer vortex flow and maintains a constant oxidizer-to-fuel ratio, eliminating gas-permeable voids and reducing material requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional cast-molded solid fuels are used, then manufacturing process is simple, but material density is inferior and performance is inconsistent
Solution Approach 1:
The patent changes the manufacturing method from conventional casting to additive manufacturing, fundamentally altering the process parameters to achieve superior material density (0.95-1.05 g/cm³) and consistency while maintaining manufacturing feasibility through automated layer-by-layer construction
Solution Approach 2:
The patent implements localized quality control through the additive manufacturing process, which allows precise control of material properties at each layer and position, ensuring uniform density throughout the fuel grain while enabling complex internal geometries that cannot be achieved with conventional casting
2Reliability
If conventional cast-molded fuel grains are used, then manufacturing is straightforward, but vibration and performance consistency are poor
Solution Approach 1:
The patent transitions from conventional casting to additive manufacturing, changing the fundamental manufacturing parameters to eliminate voids and defects that cause vibration, achieving consistent performance across production batches while the automated process manages the increased manufacturing complexity
Solution Approach 2:
The additive manufacturing process inherently self-corrects for dimensional accuracy and material distribution, building the fuel grain layer-by-layer with precise control, which eliminates the manual intervention and post-processing required in conventional casting to achieve similar consistency
3Manufacturing precision
If additive manufacturing is used to create complex geometries, then performance increases, but construction waste and labor requirements increase
Solution Approach 1:
The additive manufacturing process segments the fuel grain construction into discrete layers, building the complex geometry layer-by-layer without requiring traditional molding tools or support structures, which eliminates material waste associated with conventional manufacturing methods
Solution Approach 2:
The patent utilizes the third dimension in additive manufacturing to create complex internal geometries and vortex inducer channels that would be impossible with conventional casting, achieving high performance without the material waste inherent in subtractive or molding processes
4Stability of the object's composition
If conventional manufacturing methods are used, then production is simpler, but thermal expansion heterogeneity causes stress fractures
Solution Approach 1:
The additive manufacturing process changes the material deposition parameters to ensure uniform thermal properties throughout the fuel grain, eliminating the heterogeneity that causes differential thermal expansion and stress fractures while maintaining manufacturing simplicity through automated construction
Solution Approach 2:
The patent achieves homogeneous material properties throughout the fuel grain by using consistent material feedstock and controlled layer-by-layer deposition, ensuring uniform thermal expansion characteristics that prevent stress fractures during operation
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 method achieves smooth, consistent rocket motor operation with regression rates and specific impulse (Isp) levels previously unattainable, enabling hybrid rocket motors with reduced propellant loading and improved safety, aerodynamics, and cost-effectiveness.
Implementation Method 1
a metallic core and an epoxide-based oligomer coating surrounding the core
Implementation Method 2
fused deposition additive manufacturing apparatus
Implementation Method 3
featuring a concentric beaded structure and vortex inducer channel, which enhances oxidizer vortex flow
Data Source
AI summary
A method for making a unitary fuel grain for use in a rocket motor or gas generator comprising forming a fuel grain coating substantially free of gas-permeable voids, forming a succession of additional coats of oxidizer depleted grain material substantially free of gas-permeable voids. The fuel grain is then deposited into a print bed along a predetermined distance in a direction primarily parallel to a rocket motor central axis, the fuel grain coating forming a rocket motor fuel grain having a pre-ignition segment and a post-ignition segment, wherein the passivated fuel grain coating of fuel grain material is continuously self-adhered during fuel grain material deposition, and wherein the fuel grain material comprises oxidizer depleted fuel grain material; and wherein the passivated fuel grain coating of fuel grain material forms a substantially circular pattern upon deposition, said substantially circular pattern having an outer shell with an undulating pattern.