The metal cutting considerations in the space race
A new record for the number of people in space all at once was set in May 2023, with 20 people simultaneously in orbit. Among the many space missions that have taken place this year, Virgin Galactic’s Galactic 01 marked the first commercial suborbital spaceflight mission for the company, with SpaceX also gearing up for its first commercial spacewalk. From space tourism to rocket innovation, man is diving deeper into the great black. But how much is known about the tools that are engineering space exploration? Here, William Durow, Global Engineering Project Manager for space, defense and aerospace at Sandvik Coromant, reveals the metal cutting considerations for outer space.
In recent years, humanity has witnessed several monumental leaps in space exploration. Noteworthy among them is the European Space Agency’s JUpiter ICy moons Explorer (JUICE) mission, which launched in April 2023 and is poised to reach the Jovian System in 2030, embarking on a three-and-a-half-year mission to observe Jupiter’s three moons. Simultaneously, SpaceX has planned approximately 100 launches for the current year, and NASA’s OSIRIS-Rex successfully returned to Earth in September 2023. These endeavors represent just a fraction of the ongoing and upcoming projects aimed at unraveling the mysteries of our galaxy.
Achieving success in space missions involves a myriad of considerations, ranging from meticulous mission planning, rigorous simulations, and qualified mission managers to effective contingency planning. Beyond these, the materials utilized in space applications must withstand some of the most extreme conditions imaginable—vacuum, radiation, thermal cycling, and micrometeoroid impacts.
Tough Materials for the Cosmos
Constructing anything destined for space requires a thorough examination of materials to ensure safety, performance, and functionality in extreme conditions. Structurally, materials must endure the high pressures and stresses experienced during launch and in-flight. External materials must prevent the spacecraft from burning up during re-entry into Earth’s atmosphere, and components like rocket nozzles require heat-resistant materials.
Weight is a critical consideration, especially for elements such as rocket propellant tanks, where a lighter tank can better withstand structural stresses and enhance payload capacity. The weight of the rocket directly impacts its payload capacity—satellites, scientific instruments, and crew. Consequently, the choice of materials becomes pivotal.
Popular materials for space applications include heat-resistant superalloys (HRSAs), known for their ability to withstand harsh conditions. These alloys are designed to endure extreme temperatures, mechanical stresses, and corrosive environments. Frequently used for components like turbine blades, exhaust nozzles, and combustion chambers, HRSAs maintain their mechanical properties at temperatures exceeding 1000°C (1832°F) with exceptional creep resistance and good thermal stability. However, their robustness presents machining challenges, particularly due to the high stresses generated during the machining process.
Another pivotal material for space components is titanium. A lightweight metal with roughly half the density of steel, titanium contributes to reduced overall spacecraft weight, resulting in greater fuel efficiency and payload capacity. Its corrosion resistance and excellent resistance to atomic oxygen make titanium ideal for applications in low Earth orbit. However, machining titanium poses challenges, requiring sharp, wear-resistant cutting tools due to its high strength and low thermal conductivity compared to other metals.
Machining Considerations for Space Engineers
Machining heat-resistant superalloys demands specialized tools and techniques. Space engineers must carefully select cutting tool materials, with carbide being the predominant choice. Additionally, ceramic, cubic boron nitride (CBN), and polycrystalline diamond (PCD) find applications in roughing and finishing of HRSAs and titanium alloys. Tool coatings and geometry are crucial considerations, with a preference for sharper geometries to avoid heat generation during machining. Thin, tough coatings, particularly using Physical Vapor Deposition (PVD), are favored.
HRSAs are typically machined at lower cutting speeds to prevent excessive heat build-up and notch wear. Adjusting feed rates and depths of cut plays a crucial role in maintaining efficient machining. The right cooling strategy is paramount due to the substantial heat generated during machining of HRSAs and titanium. High-pressure coolant is often employed to break chips and dissipate excess heat. Manufacturers prioritize tool wear monitoring to predict tool failure and reduce the risk of insert failure, which could potentially damage expensive components.
Sandvik Coromant, a prominent player in the field, recommends high feed side milling as a method for machining space components efficiently. This technique involves a small radial engagement with the workpiece, allowing increased cutting speeds and feed rates with decreased heat and radial forces. To support this method, Sandvik Coromant has developed the CoroMill® Plura HFS high feed side milling range, featuring end mills optimized for titanium alloys and nickel alloys.
Unique Requirements and Ongoing Innovation
While titanium and HRSAs remain critical in the space race, organizations in the field continually innovate their materials to gain a competitive edge. The specific blends of these materials, often shrouded in secrecy, may include titanium alloys, ablative materials, carbon-carbon composites, or entirely novel compositions. Beyond the spacecraft engineers, the secrets of these material blends are shared with their machine tools suppliers.
In Sandvik Coromant’s case, their expertise in space exploration spans the globe, with dedicated research and development teams advising on the best tools and techniques for the job. When a customer approaches Sandvik Coromant, the team collaborates to discover machining solutions for their material requirements, involving testing in secure sites, consulting on tool selection, and providing advice on machining methodologies.
The stakes are exceptionally high when developing components for outer space. The slightest compromise in quality can halt a mission in its tracks. Therefore, meticulous attention is required at every step of the manufacturing process, including the selection of materials and the machining processes employed. To achieve success among the stars, manufacturers must carefully balance the use of tough materials with the associated machining challenges. Access to the right machining knowledge and robust tools is paramount for making the next great leap in space exploration.
Sandvik Coromant: Shaping the Future Together
Sandvik Coromant, in collaboration with its customers and partners, leads the way toward a sustainable future by supplying tooling solutions to the world’s engineering industries. With over eight decades of hands-on experience in metal-cutting and machining, Sandvik Coromant transforms challenges into opportunities for innovation, collaboration, & progressive solutions. Their commitment to promoting sustainability, efficiency, and growth positions them as a key contributor to shaping a future where innovation thrives. As part of the global industrial engineering group Sandvik, Sandvik Coromant continues to play a pivotal role in shaping the future of space exploration.
For more information
www.sandvik.coromant.com
