Multi-Conic Preform Assembly for Thin-Walled Semi-Ellipsoidal Shells
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Solution Overview
Problem
Existing methods for manufacturing large, lightweight components with thin-walled curved surfaces for rocket stages face challenges in accuracy, repeatability, and cost, particularly when forming non-spherical shapes using fluid pressure forming techniques, and there is a need for cost-effective methods to achieve aircraft-like reusability of rocket stages.
Innovation Solution
A method involving a multi-conic preform with longitudinally segmented annular wall segments joined by latitudinal welds, combined with fluid pressure forming and optional cold stretching, to create semi-ellipsoidal or toroidal shells from sheet metal components, which are then assembled into tanks and vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fluid pressure forming techniques are used to manufacture large components with thin-walled curved surfaces, then the need for size- and cost-prohibitive tooling is eliminated, but manufacturing precision and repeatability deteriorate due to difficulty in controlling deformity and reducing wrinkles
Solution Approach 1:
The shell is divided into multiple wall segments (first wall segment, second wall segment, third wall segment) that are formed separately and then joined together. This segmentation allows each segment to be formed with better control over deformity and wrinkles, while still achieving the overall large-scale curved surface structure without requiring prohibitively large tooling.
Solution Approach 2:
Alignment markings are provided on the wall segments before the forming process, and these markings are used to pre-align the segments during assembly. This preliminary alignment action ensures that when the segments are joined, the overall shell achieves the desired geometric precision with minimal deformity, without requiring post-forming adjustments.
2Strength
If wall segments are joined by welding to form a complete shell, then structural integrity is improved, but device complexity increases due to the need for precise alignment and multiple weld operations
Solution Approach 1:
Alignment markings are provided on the wall segments before welding operations. These markings enable quick and accurate alignment of segments during assembly, reducing the complexity of the welding operation. The markings serve as guides that simplify the positioning process, ensuring proper alignment without requiring complex alignment devices or procedures.
Solution Approach 2:
The alignment markings are provided directly on the wall segments themselves, making the segments self-aligning during assembly. This self-service approach eliminates the need for external alignment tools or complex positioning mechanisms, reducing device complexity while maintaining structural integrity through proper alignment and welding.
3Weight of moving object
If rocket stages are designed for reusability with minimal additional mass, then payload capacity is preserved, but manufacturing complexity increases due to the need for additional functionality in harsh re-entry environments
Solution Approach 1:
The shell is segmented into multiple wall segments that can be manufactured separately using standardized processes and then assembled. This segmentation allows for modular replacement and repair of individual segments after re-entry, enabling reusability without requiring complete replacement of the entire shell. The segmented design adds minimal mass while providing the functionality needed for harsh re-entry environments through selective replacement of damaged segments.
Solution Approach 2:
The segmented shell design enables selective recovery and replacement of wall segments. After re-entry, only the damaged segments need to be replaced while the intact segments are recovered and reused. This approach minimizes mass addition for reusability by maximizing the reuse of undamaged components while providing the necessary functionality to withstand harsh re-entry environments.
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 approach enables the production of thin-walled, high-performance components with controlled deformity and reduced wrinkles, facilitating the reuse of rocket stages with minimal mass addition and improved structural integrity.
Implementation Method 1
The pressure of the fluid medium in the cavity is increased in a controlled manner until the preform plastically deforms and bulges to form a shell with a desired shape
Implementation Method 2
the preform plastically deforms and bulges to form a shell with a desired shape
Implementation Method 3
positionally fixing the first preform wall segment relative to the second preform wall segment such that the top edge alignment markings of the first preform wall segment are aligned with the bottom edge alignment markings of the second preform wall segment
Implementation Method 4
joining the top edge of the first preform wall segment to the bottom edge of the second preform wall segment via a first latitudinal weld
Data Source
AI summary
A semi-ellipsoidal, semi-toroidal, or toroidal shell includes an annular sheet metal wall that is longitudinally segmented so as to include a plurality of annular wall segments. Each of the plurality of annular wall segments is joined to an adjacent wall segment by a respective latitudinal wall weld. Also disclosed is a tank including the shell, a vehicle including the shell, a multi-conic preform used to manufacture the shell, a method for assembling the preform, and a method for manufacturing the shell using the preform.