Lessons learned from the Ingenuity Mars helicopter will play a role in designs for follow-on craft

Almost a year later NASA’s Ingenuity helicopter crash-landed on Mars after an extended, remarkably successful mission, engineers have identified the most likely culprit: a flight over sand drifts so featureless that onboard sensors could not determine the helicopter’s orientation and speed.

The result was a “hard” sideways landing on a steep slope that spun Ingenuity so quickly that its rotors, which spun at nearly 400 miles per hour to provide lift in Mars’ ultra-thin atmosphere, structurally failed. One broke off and the others were severely damaged.

Håvard Grip, Ingenuity’s first pilot, said in an interview on Wednesday that lessons have been learned Ingenuity’s 72nd and final flight on January 18 will be used in designs for more powerful Mars helicopters now being studied at the Jet Propulsion Laboratory where Ingenuity was built.

“We are currently working very actively on what that could look like,” Grip said in an interview. “We’re developing this big aircraft concept with six rotors and 36 blades that could fly its own science payload around Mars. So that’s kind of where our focus is right now in the helicopter world.”

During a briefing Wednesday at the annual meeting of the American Geophysical Union in Washington, D.C., Teddy Tzanetos, Ingenuity’s project manager, discussed the six-rotor Mars Chopper concept, a helicopter aircraft that would be 20 times heavier than Ingenuity and travel up to two miles could fly. carrying several kilos of scientific instruments per day.

Ingenuity “became the first mission to fly commercial off-the-shelf mobile phone processors into space,” Tzanetos said in a NASA news release. The mission showed “that not everything needs to be bigger, heavier and radiation-hardened to work in the harsh environment of Mars.”

Ingenuity was transported to Mars by NASA’s Perseverance rover and dropped to the red planet’s surface in April 2021. made its first flight two weeks later. Built primarily to find out if helicopters could fly in the cold, thin atmosphere, Ingenuity was expected to make five flights over 30 days as a proof of concept.

To the surprise of almost everyone, the plane ultimately made 72 flights over nearly three years, repeatedly coming out ahead of Perseverance as it logged more than two hours of flight time and traveled a total of 17.7 miles at altitudes of up to 80 feet before its final flight at January 18.

During that flight, Ingenuity climbed to a height of about 40 feet, hovered and took photographs of the surrounding terrain, and began descending 19 seconds after takeoff. Thirteen seconds later the helicopter was back on the ground, but contact was lost.

Communications via Perseverance were restored the next day, and six days after the flight the rover sent back photos showing that the helicopter had suffered extensive damage to its rotors.

Flight controllers initially suspected that Ingenuity was making a hard landing at a steep angle, causing its high-speed rotors to hit the ground.

But the most likely scenario, Grip said, is that the helicopter failed to determine its horizontal speed as it flew over virtually featureless sand and landed while moving sideways at a speed well above design limits.

“We also landed on a steep slope, probably the steepest slope we have encountered in all our flights,” he said. ‘The combination of the two lends itself well to what our most likely scenario assumes.

“When it hit the ground, it spun around rapidly to align with the surface. That forces the helicopter to rotate in roll and pitch, and because this rotor is stiff, the rotor has to follow more or less. less direct, and that causes a lot of bending moments on the knives.”

Those bending moments, or forces, were extreme because the tips of the rotors were moving so quickly. The tips of the blades broke off, causing the rotor system to become unbalanced. That in turn resulted in enough vibration to cause one rotor to break off at the root. Grip said none of the blades touched the surface during landing.

Another surprise for flight controllers: Ingenuity came to a rest on its landing legs, with its small solar panel pointed skyward. Although it could no longer fly, it continued to relay Martian weather reports to Perseverance through November of last year, when the rover eventually moved too far away to maintain radio communication.

“I always imagined that a bad landing would end with, you know, the thing in a thousand pieces on the surface,” Grip said. “So the fact that it’s standing up and talking to us (was) not what I expected at all.”