NASA Pushes Next-Generation Mars Helicopter Rotors Past the Speed of Sound

NASA engineers have pushed next-generation Mars helicopter rotor blades past the speed of sound during tests at the agency's Jet Propulsion Laboratory (JPL) in Southern California, showing that the blade tips can safely exceed Mach 1 inside a chamber built to recreate Martian atmospheric conditions. Data from 137 test runs will help engineers design aircraft capable of carrying larger payloads, including scientific instruments, to the Red Planet.

Flying on Mars is difficult because the planet's atmosphere is only about 1% as dense as Earth's, meaning rotor blades must approach the speed of sound to generate enough lift. "NASA had a great run with the Ingenuity Mars Helicopter, but we are asking these next-generation aircraft to do even more at the Red Planet," said Al Chen, Mars Exploration Program manager at JPL. "While everything about Mars is hard, flying there is just about the hardest thing you can do."

NASA's Ingenuity helicopter made the first powered, controlled flight on another world on April 19, 2021, and went on to complete 72 flights, but it was built only as a technology demonstration and carried no science instruments. During those flights, engineers kept Ingenuity's rotor blade tips below Mach 0.7 with no wind, so that a Martian headwind would not push them into supersonic speeds. "If Chuck Yeager were here, he'd tell you things can get squirrely around Mach 1," said JPL's Jaakko Karras, the rotor test lead. "We want more performance from our next-gen Mars aircraft. We needed to know that our rotors could go faster safely."

For the tests, engineers mounted a three-bladed rotor built by AeroVironment of Simi Valley, California, inside JPL's 25-Foot Space Simulator, replacing the chamber's air with carbon dioxide at Mars-like pressure. As rotor speed climbed to 3,750 rpm, the blade tips reached Mach 0.98; adding headwinds pushed the tips to Mach 1.08, increasing the rotor's lifting capability by 30%. A two-bladed rotor designed for NASA's SkyFall mission concept needed only 3,570 rpm to reach similar near-supersonic tip speeds, because its blades are longer.