By Cosmos US correspondent
Richard Lovett
NASA’s Ingenuity helicopter has made its last flight on Mars. The spindly 1.8-kilogram helicopter crashed landed on 18 January and broke at least one of its rotors, NASA announced today.
It’s a bittersweet moment, says Teddy Tzanetos, the helicopter’s project manager at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. Sad, because it marked the end of an airborne explorer that had captured public attention. But also the end of a prolonged triumph, because the helicopter had been designed as a technology demonstration, slated to be abandoned after 30 days and a handful of flights. Instead, it lasted nearly three years, and survived 71 flights before finally succumbing on its 72nd.
The fact it flew at all was itself a triumph. “On Earth, helicopters can’t fly above 25,000 feet (7,600 meters),” says JPL’s director, Laurie Leshin. “On Mars the atmosphere is so thin that it’s equivalent to Earth’s atmosphere at 80,000 or 90,000 feet (24,000 or 27,000 meters).”
Now, NASA is planning larger Ingenuity-style helicopters as part of its next Mars landing. And Lori Glaze, director of the agency’s Planetary Science Division, envisions that when humans finally do get to Mars, they will be accompanied by a fleet of flying robotic scouts.
Ingenuity has kept us spellbound
Ingenuity initially ran into trouble on its 71st flight, Tzanetos says, when it was forced to make an emergency landing. That time it got to the ground safely, and reported back that all systems were healthy and able to fly.
The problem, Tzanetos says, was that beginning on flight 69, it began venturing into very sandy terrain with few rocks its robotic navigation system could use as landmarks to track progress. The emergency landing came about because the terrain was so bland that the helicopter’s robotic navigation system couldn’t keep oriented.
Flight 72, he adds, was designed to be a quick hop—12 meters straight up to get a look around, then straight back down to wait while controllers back on Earth figured out what to do next. This time, however, the landing didn’t work.
What most likely happened, says Håvard Grip, JPL’s chief engineer for Mars’ helicopters is that it got truly lost as it neared the ground, and tried to maneuver sideways in the effort to find a landmark. That might have been followed by an overly aggressive maneuver when it realized its error, aggressive enough to dip a blade into the sand—a deadly event for any helicopter.
But the reality is that the details aren’t known, and given the data loss, he says, “we may never know.”
What is known is that the helicopter came down upright and is still perfectly operational except for the broken blade or blades. That makes it unflyable for two reasons: (1) it would shake itself apart if spun up to flying speeds of 2,500 revolutions per minute, and (2) a disproportionate amount the lift comes from the outer portions of the rotor—the part now broken off. “That means we’ve lost a massive chuck of our thrust capacity,” Tzanetos says.
“We didn’t design the system to handle this kind of terrain,” Grip adds. But he says, “we now know that this kind of terrain can be a trap.” Future helicopters, he says, might be programmed to immediately back up if they encounter such conditions, or be equipped with higher-resolution cameras that could pick out smaller features by which to navigate.
None of this affects the Perseverance rover itself in any important way. Yes, it had benefited from the presence of an aerial scout. But it was designed to work on its own, without one, and the long survival of Ingenuity was simply a bonus to the mission, not a critical component. Instead, what will happen is that the rover will gradually move on, eventually losing contact with the helicopter as it continues on its own.
