Multi-Conic Thin-Walled Shell Forming for Concentric Rocket Tanks
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Solution Overview
Problem
The challenge of manufacturing large, lightweight components with thin-walled curved surfaces for rocket stages, such as the upper stage, is hindered by the need for costly tooling and the difficulty in accurately forming and welding sheet metal components, particularly for non-spherical shapes, which leads to unsightly deformities and destabilizing issues in fluid pressure forming processes.
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 with improved control over concentricity and reduced tooling costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional fluid pressure forming is used to manufacture large thin-walled curved components, then tooling costs are reduced, but manufacturing precision deteriorates due to uncontrollable deformities and poor concentricity
Solution Approach 1:
The preform wall is divided into multiple annular wall segments joined by latitudinal welds, creating a segmented structure that maintains concentricity during forming. Each segment can be independently positioned and welded, ensuring precise alignment and reducing deformities while avoiding the need for expensive traditional tooling.
2Adaptability or versatility
If sheet metal components are formed and welded for large curved shells, then component flexibility is improved, but manufacturing precision deteriorates due to welding inaccuracies and deformities
Solution Approach 1:
The preform is constructed with pre-assembled annular wall segments joined by latitudinal welds before the final forming process. This preliminary structuring ensures precise concentricity and alignment are established early, and subsequent fluid pressure forming maintains these precision characteristics while achieving the desired curved shell shape.
3Adaptability or versatility
If non-spherical shell shapes are formed using fluid pressure, then design versatility is improved, but manufacturing precision deteriorates due to destabilizing deformities
Solution Approach 1:
The segmented preform structure with latitudinal wall segments allows the formation of complex non-spherical shapes including semi-ellipsoidal and toroidal geometries. The segmentation maintains structural stability during forming, preventing the destabilizing deformities that typically occur with non-spherical shapes, while enabling design versatility for various rocket stage configurations.
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 high-performance, thin-walled shells with controlled deformities, reducing material costs and enhancing the reusability of rocket stages by minimizing structural mass while maintaining precise shape and structural integrity.
Implementation Method 1
Fluid pressure forming generally involves use of a fluid medium (e.g., water, oil, gas, liquified gas, etc.) to load and deform a workpiece. 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
Cold stretching (or cold forming) is a technique that is similar in principle to cryogenic stretching, but the cooling medium is water instead of liquid nitrogen.
Implementation Method 3
The preform 216 includes a domed cap 218, a domed base 219, and an annular wall 220 extending therebetween. Notably, the wall 220 is latitudinally segmented so as to include a plurality of wall gores 226, each of which is joined to an adjacent wall gore 226 by a respective longitudinal weld 246.
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.