Innovative Manufacturing of Launch Vehicle Structures Using Integrally Stiffened Cylinder (ISC) Technology

Reducing launch costs is essential to ensuring the success of NASA’s vision for Mars exploration, economical support of the International Space Station (ISS), and competitiveness of the U.S. commercial launch industry. Reducing launch vehicle manufacturing costs supports this goal. Manufacturing of the Shuttle external cryogenic propellant tank relied on multi-piece machined and welded construction using technology developed in the 1950’s. It was expensive and time intensive and the welded structure resulted in greater weight and risk. This manufacturing technology remains the baseline for NASA’s Space Launch System and commercial launch system cryotanks.

An innovative spin/flow forming technology is under development by NASA Langley Research Center (LaRC) that could revolutionize cryogenic tank fabrication by producing a net shape cryotank barrel with internal stiffeners in a single forming operation. The integrally stiffened cylinder (ISC) advanced manufacturing technology could replace conventional multi-piece construction, realizing up to 50% reduction in manufacturing costs with an associated 10% reduction in vehicle mass. While targeted for cryogenic tanks, ISC technology will also benefit intertank and dry bay structures, rocket segments, and missile bodies. ISC technology could also benefit aircraft fuselage structures by replacing time intensive riveted construction.

ISC technology was adapted from an automotive manufacturing method to make 8-inch diameter steel clutch housings. NASA LaRC optimized this technology to form aerospace aluminum alloys and demonstrated stiffener sizes and shapes required for cryogenic tanks. Initial process scale up resulted in successful manufacture and flight of a 17-inch diameter integrally stiffened sounding rocket payload segment. NASA teamed with the European Space Agency (ESA) and U.S. and international industry partners to further scale the ISC technology to manufacture 10-foot diameter cylinders. Ongoing work aims to optimize and further scale up the ISC process to fabricate aerospace quality aluminum alloy cryogenic tanks at commercial launch vehicle scales.