NASA's Mars helicopter Ingenuity didn't get off the ground as planned earlier this month.
Ingenuity was scheduled to make its 14th Red Planet sortie on Sept. 18, a relatively short and simple hop that would have demonstrated the little chopper's ability to fly with slightly higher rotor speeds — 2,700 revolutions per minute (RPM) rather than the usual 2,537 RPM.
The mission team is making this adjustment to deal with the Martian atmosphere, which is thinning out slightly as the seasons change on the floor of the Red Planet's Jezero Crater, Jaakko Karras, Ingenuity deputy operations lead at NASA's Jet Propulsion Laboratory in Southern California, wrote in an update Tuesday (Sept. 28).
Ingenuity performed a high-speed rotation test on Sept. 15, spinning its blades at 2,800 RPM for a spell while it remained on the ground. Everything went well, paving the way for the Sept. 18 flight. But the 4-pound (1.8 kilograms) chopper did not end up taking off that day.
"Here's what happened: Ingenuity detected an anomaly in two of the small flight-control servo motors (or simply 'servos') during its automatic pre-flight checkout and did exactly what it was supposed to do: It canceled the flight," Karras wrote.
Ingenuity has six servos, three for each of its two rotors. The little motors adjust the pitch of the rotors, allowing the chopper to control its orientation and position during flight.
"The servo motors are much smaller than the motors that spin the rotors, but they do a tremendous amount of work and are critical to stable, controlled flight," Karras wrote.
Analysis of the Sept. 18 preflight test has shown that two of Ingenuity's servos oscillated slightly during the "servo wiggle" checkout. The team is still trying to determine the cause, but it may be due to increasing wear in the servo gearboxes and linkages, Karras wrote. (Ingenuity is a technology demonstrator that was originally supposed to make just five flights on the Red Planet.)
Ingenuity passed two additional servo wiggle tests on Sept. 21 and Sept. 23, however, "so the issue isn’t entirely repeatable," Karras wrote. "We have a number of tools available for working through the anomaly, and we're optimistic that we'll get past it and back to flying again soon."
But orbital dynamics will keep Ingenuity grounded for a couple more weeks at least. Mars is now in "solar conjunction," meaning it's on the other side of the sun from Earth. Our star can corrupt and otherwise interfere with communications sent between the two planets, so NASA has stopped sending commands to Ingenuity and its other Red Planet robots — including Ingenuity's much larger partner, the Perseverance rover— until mid-October, when Mars will come more clearly into view.
"Ingenuity will not be completely idle during this time, however; Ingenuity and Perseverance will be configured to keep each other company by communicating roughly once a week, with Ingenuity sending basic system health information to its base station on Perseverance," Karras wrote. "We will receive this data on Earth once we come out of conjunction, and will learn how Ingenuity performs over an extended period of relative inactivity on Mars. See you on the other side of conjunction!"
Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.