Design Optimization and Utilization of Advanced Aluminum Alloys on the SLS EUS

Space Launch System (SLS) represents the next generation of man-rated space-flight vehicles designed for deep-space exploration. Two cryogenic stages coupled with solid fuel rocket boosters will deliver up to 130 metric tons of cargo to intermediate orbits in preparation for interplanetary travel. Major components of the EUS wet and dry volumes are being joined using friction stir weld (FSW) technology, and similar to the SLS Core Stage (CS), AA 2219-T87 was originally utilized. During the early stages of the EUS design, i.e. when significant weight savings is typically realized by architecture optimization (e.g. lighter materials, configuration changes, etc...), a decision was made to explore usage of advanced AL-Li alloys (drawing on the experience of the Space Shuttle External Tank). Based on mechanical properties (strength and durability) and relative density, Constellium’s Airware® 2050 alloy was selected as part of a formal trade study which showed significant benefits to using AA 2050 on EUS. This paper presents the results of this trade study including details associated with the design optimization achieved due to the usage of Airware® 2050.