When materials are moving at hypersonic speed through the earth’s atmosphere, they get extremely hot! In aerodynamics, hypersonic speed is described as anything that exceeds 5 times the speed of sound, otherwise known as Mach 5. Most hypersonic flight can reach upwards of 20 times the speed of sound and exceed temperatures of 1800oC. This makes materials development for thermal protection a critical part of the hypersonic system design.
At Battelle, we use our 90+ years of advanced materials engineering to develop solutions that utilize carbon-carbon composites. These materials consist of high-strength carbon fibers, woven together like cloth. The carbon fiber sheets are then stacked and sewn together, and the space between is filled with polymer. Carbon-carbon composites are exceptionally lightweight and retain their mechanical strength at extreme temperatures, making them the perfect materials for thermal protection of hypersonic vehicles.
Traditionally, carbon-carbon composites are made by starting with carbon fiber pre-fabs that carbonized by putting the entire part in large industrial ovens —a highly manual, time-consuming and expensive process. In this process, the entire material structure is converted into a carbon-carbon composite, making the part brittle and providing a pathway for heat to get into the interior systems when in use. Through internal research and development efforts, our advanced materials team are working to mature a controlled laser heating system to carbonize composites without the use of huge ovens. With our selective laser heating, lasers are directed to the exposed surface of the thermal protection system, providing better protection where needed. Our material has been tested at recognized hypersonics test facilities.
Battelle’s selective laser heating provides a higher level of precision and control over the heating profile. The heat is directed with more precision, creating the thermal protection system where it needs to be while leaving a tough polymer matrix composite where necessary. In addition to being more precise, this method is significantly faster and more scalable to any shape or size, than the traditional use of ovens, reducing production time from months to hours. We intend to help the industry scale up production of hypersonic vehicles using this process since it provides a more flexible and cost-effective option.
Our team is improving the laser heating process and further testing is scheduled at recognized test facilities. We believe selective laser heating is a huge step towards making carbon-carbon material fabrication faster, easier and less expensive.