Development of Advanced Manufacturing Approaches for Single-Piece Launch Vehicle Structures

Advanced, near-net shape manufacturing methods have the potential to enable production of
structures with fewer welds and reduced machining requirements. Two such methods that are
suitable for the manufacturing of single-piece, stiffened barrel-shaped structures are presented.
The first solution deployed existing manufacturing technology to produce a thick-walled barrel
with integrally machined stiffeners. In this study, an 8-ft. diameter barrel was produced and
subjected to a buckling test. Data on the manufacturing and testing of this barrel are provided and
compared against the traditional multi-piece weld construction approach. The single-piece barrel
resulted in a 28% greater load carrying capacity than the welded barrel.

A second solution utilized a novel flow-forming technique to produce the barrel and stiffeners
in one process without the need for welding or machining. This is an emerging manufacturing
method known as the Integrally Stiffened Cylinder (ISC) process. This innovative process is being
evaluated for launch vehicle and commercial aircraft manufacturing. The one-piece, stiffened ISC
barrels, which have been successfully fabricated at 10 ft. in diameter, offer a direct replacement
for conventional multi-piece, welded or riveted structures. A cost-benefit analysis for launch
vehicle cryogenic propellant tanks estimated that the ISC process offers up to a 50% reduction
in manufacturing costs and a 10% reduction in mass.