13 ADVANCED MATERIALS & PROCESSES | MARCH 2024 The United States’ space launch program has played a key role in the advancement of materials science for the last seven decades. Unprecedented financial investment was initiated during the Apollo program in the 1960s and continued with the Space Shuttle program until the last flight of Atlantis on July 8, 2011. The winding down of the shuttle program gave way to significant privately funded launch system development with more unprecedented investment in recent years. These programs continue to advance materials science and engineering as the focus moves toward human travel to the moon, Mars, and beyond. Star Trek creator Gene Roddenberry gave an interesting lecture at North Carolina State University in the mid1980s while the author was working on his undergraduate degree. At the time, the United States was in the early stages of a very robust but technically challenging Space Shuttle program. Roddenberry noted that the technology boosts resulting from the Apollo and Shuttle programs would pave a fast track for space travel and he predicted that humans would be living on the moon by the year 2000. His forecast was based on extrapolating out the advances in materials science on the trajectory we were on at that time. Although his prediction did not come true, we are on track to land humans on the moon once again this decade. Modern day orbital space launches and the vision of millions of people living and working in space has required game-changing technological advancements in how rockets are engineered and built. Significant cost reduction of launch systems is needed to make space travel financially sustainable. Figure 1 shows a comparison of launch costs per kg of cargo for various launch systems over the past several decades. Recent advances in technology have reduced costs to an all-time low of $2500 per kilogram of payload. Two key technology areas that are driving these launch costs down are weight reduction and reusability. ADDITIVE MANUFACTURING One example of a technology that has been a game-changer for aerospace and other industries over the past two decades is additive manufacturing (AM). Additive manufacturing has helped the space industry reduce the weight of rocket components by allowing the fabrication of parts that were previously impossible to machine using traditional techniques. For example, internal weight-saving cavities can be designed into a part produced by AM. Figure 2 shows some examples of metallic parts produced by AM. AM technology also helps rapidly prototype parts for evaluation. The National Aeronautics and Space Administration (NASA) acknowledges that “propulsion system development requires new, more affordable manufacturing techniques and technologies in a constrained budget environment, while future in-space applications will require in-space manufacturing and assembly of parts and systems”[2]. Fig. 2 — Parts produced from metal powder using AM. Fig. 1 — Approximate payload cost per kg for various medium-heavy launch systems, adjusted for inflation[1].
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