Hypersonic missiles were used for the first time in combat last month in Ukraine, as Russian jets launched Kinzhal missiles from jet fighters. Hypersonic missiles are fast, flying at speeds of Mach 5 or faster, and when combined with a flat trajectory compared to ballistic missiles and maneuverability, they present a difficult problem for defense.Hypersonic missiles are under development as long-range strategic weapons, but the most intense research is in air-launched standoff systems launched from conventional military aircraft. The Kinzhal system uses conventional rocket engines, but more advanced propulsion under development in China and the U.S. uses air breathing supersonic combustion ramjets to use air as the oxidizer, adding longer range compared to rocket systems. Heat is the primary technical challenge to “scramjet” development, but test systems with run times that could allow a 300-mile range have been demonstrated.Want to watch this podcast as a video? This Week in Engineering is available on engineering.com TV along with all of our other shows such as End of the Line, Designing the Future, and, Manufacturing the Future.