Dismantleable Mandrel Assembly for Deep Fin Cavity Solid Rocket Propellant
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Solution Overview
Problem
Conventional mandrel assemblies for solid rocket motors have limitations in flexibility and safety due to their complex designs with multiple components and joints, leading to challenges in forming large propellant grain cavities and increasing the risk of propellant slurry leaks and explosion hazards during the decoring process.
Innovation Solution
A mandrel assembly comprising a base mandrel, a core mandrel, and fin molds with a minimal number of components and joints, allowing for the formation of deep cavities and safe propellant grain manufacturing by configuring the mandrel inside the rocket motor casing, casting the propellant slurry, and minimizing machining requirements post-curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional single-piece casting mandrels are used, then the grain design flexibility is limited because major transverse dimensions of propellant grain cavities cannot be larger than the openings in the monolithic casing, but using larger mandrels would allow formation of larger cavities
Solution Approach 1:
The mandrel is divided into multiple segments that can be assembled together to form a complete mandrel structure with transverse dimensions larger than the casing opening. These segments are inserted through the casing opening and joined internally to create the desired large-diameter mandrel configuration, enabling formation of large propellant grain cavities while using a small opening.
2Reliability
If conventional mandrel assemblies with multiple components and joints are used, then the propellant slurry leak risk increases due to critical joints, but using fewer components would limit the ability to form complex grain cavities
Solution Approach 1:
Multiple mandrel segments are designed to join together with minimal joint interfaces, reducing the number of critical joints compared to conventional multi-component assemblies. The segments are combined to form a unified mandrel structure that maintains reliability while enabling complex cavity formation.
3Object-affected harmful factors
If conventional dismountable mechanical cores with multiple components are used, then the decoring process becomes more hazardous due to large number of components and joints, but using simpler cores would reduce cavity formation capability
Solution Approach 1:
The mandrel is segmented into a limited number of large components rather than many small parts, reducing the complexity of the decoring process. Fewer segments mean fewer joints to disconnect and fewer components to remove from the cured propellant grain, thereby reducing explosion hazards during decoring while still enabling complex cavity formation.
4Volume of moving object
If propellant machining is used to form grain cavities larger than casing openings, then the grain cavity size can be increased, but the process becomes slow and hazardous
Solution Approach 1:
The mandrel is pre-assembled to the required large dimensions before the propellant casting process, eliminating the need for post-curing machining operations. The mandrel segments are joined together and inserted into the casing before propellant is introduced, allowing the propellant to cure around the complete mandrel structure, thus forming the final cavity shape directly during casting rather than requiring slow and hazardous machining afterward.
Data Source
Figure 1
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Figure 3~4b
AI summary
The present disclosure relates to a dismantleable mandrel assembly and a method of molding solid propellant grains with deep fin cavities whose major transverse dimensions are larger than casing opening dimensions in a monolithic rocket motor. The mandrel assembly comprises a base mandrel, a core mandrel insertable into the base mandrel and a plurality of fin molds attachable onto the base mandrel in a circular pattern about the motor axis. The plurality of longitudinal fin cavities is configured with forward swept leading and trailing edges. The manufacturing technique involves assembling and disassembling the mandrel components before propellant casting and after propellant curing respectively in a specific sequence. With minimum number of components and critical joints the method assures reduced quantum of explosive hazard in propellant grain manufacturing for high performance solid rocket motors.