2,800 RPM Spin a Success, but Flight 14 Delayed to Post Conjunction
Its been an eventful numerous Martian days, or sols, considering that our last post, so we wished to provide everybody with an upgrade on where things stand on Mars. In our last post, we described that we were preparing yourself to start flying with a greater rotor speed to make up for decreasing atmospheric density triggered by seasonal modifications on Mars. Increasing the rotor speed is a significant modification to how weve been flying so far, so we wanted to proceed forward thoroughly. Step one was to perform a high-speed spin test at 2,800 rpm on the ground and, if whatever worked out, step 2 was to perform a short-duration flight, briefly hovering over our current area, with a 2,700 rpm rotor speed.
The high-speed spin test was finished effectively on September 15, 2021 at 23:29 PDT, 11:11 LMST local Mars time (Sol 204 of the Perseverance mission). Resourcefulnesss motors spun the rotors up to 2,800 rpm, briefly held that speed, and then spun the rotors back down to a stop, all precisely as sequenced for the test. All other subsystems carried out flawlessly. Of particular interest was figuring out whether the greater rotor speeds trigger resonances (vibrations) in Ingenuitys structure. Resonances are a typical challenge in aerial rotorcraft and can cause issues with sensing and control, and can likewise result in mechanical damage. The information from this newest high-speed spin showed no resonances at the higher rotor rpms. The successful high-speed spin was an exciting accomplishment for Ingenuity and provided us the green light to continue to a test flight with a 2,700 rpm rotor speed.
Resourcefulnesss Upper Swashplate Assembly: The upper swashplate of NASAs Ingenuity Mars Helicopter controls the pitch of the upper rotor blades as they rotate and is important to steady, controlled flight. Heres what took place: Ingenuity found an abnormality in two of the small flight-control servo motors (or merely “servos”) during its automated pre-flight checkout and did precisely what it was expected to do: It canceled the flight.
Each rotor has its own independently managed swashplate, and each swashplate is activated by 3 servos, so Ingenuity has 6 servos in total. We affectionately refer to the Ingenuity servo self-test as the “servo wiggle.”
Resourcefulness will not be completely idle during this time, however; Ingenuity and Perseverance will be set up to keep each other company by interacting roughly as soon as a week, with Ingenuity sending out standard system health details to its base station on Perseverance.
Resourcefulnesss Upper Swashplate Assembly: The upper swashplate of NASAs Ingenuity Mars Helicopter controls the pitch of the upper rotor blades as they turn and is important to stable, controlled flight. The swashplate is driven by 3 small servo motors. Credit: NASA/JPL-Caltech.
The test flight was arranged to occur on September 18, 2021 (Sol 206) and was expected to be a brief hover flight at 16 feet (5 meters) elevation with a 2,700 rpm rotor speed. It turned out to be an uneventful flight, due to the fact that Ingenuity decided to not remove. Heres what took place: Ingenuity discovered an abnormality in two of the small flight-control servo motors (or simply “servos”) during its automated pre-flight checkout and did exactly what it was expected to do: It canceled the flight.
Each rotor has its own independently controlled swashplate, and each swashplate is activated by three servos, so Ingenuity has 6 servos in overall. Due to the fact that of their urgency, Ingenuity performs an automatic check on the servos prior to every flight. We affectionately refer to the Ingenuity servo self-test as the “servo wiggle.”
The data from the anomalous pre-flight servo wiggle reveals that 2 of the upper rotor swashplate servos– servos 1 and 2– began to oscillate with an amplitude of approximately 1 degree about their commanded positions just after the second step of the sequence. Ingenuitys software spotted this oscillation and immediately canceled the self-test and flight.
Our team is still looking into the abnormality. To collect more data, we had Ingenuity perform additional servo wiggle tests during the past week, with one wiggle test on September 21, 2021 (Sol 209) and one on September 23, 2021 (Sol 211). Both of the wiggle trial run effectively, so the concern isnt totally repeatable.
One theory for whats taking place is that moving parts in the servo gearboxes and swashplate linkages are beginning to reveal some wear now that Ingenuity has actually flown well over two times as many flights as originally prepared (13 completed versus 5 prepared). Use in these moving parts would cause increased clearances and increased looseness, and might explain servo oscillation. Another theory is that the high-speed spin test left the upper rotor at a position that loads servos 1 and 2 in a distinct, oscillation-inducing way that we havent come across prior to. We have a variety of tools offered for working through the anomaly and were optimistic that well surpass it and back to flying once again soon.
Ingenuity will not be completely idle during this time, however; Ingenuity and Perseverance will be set up to keep each other business by communicating approximately when a week, with Ingenuity sending out fundamental system health info to its base station on Perseverance. We will get this information on Earth as soon as we come out of combination, and will learn how Ingenuity performs over a prolonged duration of relative lack of exercise on Mars.
Written by Jaakko Karras, Ingenuity Mars Helicopter Deputy Operations Lead at NASAs Jet Propulsion Laboratory