There are approximately 25,000 “city killer” asteroids in near-Earth orbit. Small enough to evade detection, they are capable of large-scale destruction and represent our greatest cosmic threat. But in September 2022, NASA’s Double Asteroid Redirection Test (DART) mission crashed a spacecraft into a city killer, altering the asteroid’s orbit and proving that we stand a chance against them. In How to Kill an Asteroid, Robin George Andrews–who was at DART mission control when it happened–reveals the development of the technology that made it possible. In a narrative that reads like a sci-fi thriller, Andrews tells the story of the planetary defence movement, and introduces the international team of scientists and engineers now working to protect Earth.