A machine weighing 1.8 kilograms pulled off the aerodynamic equivalent of flying a helicopter at 87,000 feet on Earth. This episode tells the full biography of NASA's Ingenuity Mars helicopter, beginning with its three years as an unfunded rebel project at the Jet Propulsion Lab, the opposition from Mars 2020 chief scientist Kenneth Farley, and the $23 million finally secured in the 2018 federal budget. It then digs into the engineering required to fly in an atmosphere with one percent of Earth's density: four-foot coaxial rotors spinning at 2,400 to 2,900 RPM, a smartphone Snapdragon processor running Linux, off-the-shelf Sony batteries, and a test chamber with a wall of nearly 900 computer cooling fans and a gravity-offload string.

The story covers the watchdog timer glitch that nearly derailed the first flight, the 85 percent workaround  ...