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It’s been an eventful a number of Martian days, or sols, since our final weblog submit, so we wished to supply everybody with an replace on the place issues stand on Mars. In our final submit, we defined that we have been on the point of start flying with the next rotor velocity to compensate for reducing atmospheric density attributable to seasonal modifications on Mars. Growing the rotor velocity is a major change to how we’ve been flying to date, so we wished to proceed ahead fastidiously. The 1st step was to carry out a high-speed spin check at 2,800 rpm on the bottom and, if every part went nicely, step two was to carry out a short-duration flight, briefly hovering over our present location, with a 2,700 rpm rotor velocity.
The high-speed spin check was accomplished efficiently on Sept. 15, 2021 at 23:29 PDT, 11:11 LMST native Mars time (Sol 204 of the Perseverance mission). Ingenuity’s motors spun the rotors as much as 2,800 rpm, briefly held that velocity, after which spun the rotors again right down to a cease, all precisely as sequenced for the check. All different subsystems carried out flawlessly. Of specific curiosity was figuring out whether or not the upper rotor speeds trigger resonances (vibrations) in Ingenuity’s construction. Resonances are a standard problem in aerial rotorcraft and may trigger issues with sensing and management, and may result in mechanical injury. Thankfully, the info from this newest high-speed spin confirmed no resonances on the greater rotor rpm’s. The profitable high-speed spin was an thrilling achievement for Ingenuity and gave us the inexperienced gentle to proceed to a check flight with a 2,700 rpm rotor velocity.
The check flight was scheduled to happen on Sept. 18, 2021 (Sol 206) and was presupposed to be a quick hover flight at 16 ft (5 meters) altitude with a 2,700 rpm rotor velocity. It turned out to be an uneventful flight, as a result of Ingenuity determined to not take off. Right here’s what occurred: Ingenuity detected an anomaly in two of the small flight-control servo motors (or just “servos”) throughout its automated pre-flight checkout and did precisely what it was presupposed to do: It canceled the flight.
Ingenuity controls its place and orientation throughout flight by adjusting the pitch of every of the 4 rotor blades as they spin across the mast. Blade pitch is adjusted by means of a swashplate mechanism, which is actuated by servos. Every rotor has its personal independently managed swashplate, and every swashplate is actuated by three servos, so Ingenuity has six servos in whole. The servo motors are a lot smaller than the motors that spin the rotors, however they do an amazing quantity of labor and are essential to steady, managed flight. Due to their criticality, Ingenuity performs an automatic examine on the servos earlier than each flight. This self-test drives the six servos by means of a sequence of steps over their vary of movement and verifies that they attain their commanded positions after every step. We affectionately consult with the Ingenuity servo self-test because the “servo wiggle.”
The info from the anomalous pre-flight servo wiggle reveals that two of the higher rotor swashplate servos – servos 1 and a couple of – started to oscillate with an amplitude of roughly 1 diploma about their commanded positions simply after the second step of the sequence. Ingenuity’s software program detected this oscillation and promptly canceled the self-test and flight.
Our workforce continues to be trying into the anomaly. To collect extra information, we had Ingenuity execute further servo wiggle assessments in the course of the previous week, with one wiggle check on Sept. 21, 2021 (Sol 209) and one on Sept. 23, 2021 (Sol 211). Each of the wiggle assessments ran efficiently, so the difficulty isn’t totally repeatable.
One idea for what’s taking place is that shifting components within the servo gearboxes and swashplate linkages are starting to indicate some put on now that Ingenuity has flown nicely over twice as many flights as initially deliberate (13 accomplished versus 5 deliberate). Put on in these shifting components would trigger elevated clearances and elevated looseness, and will clarify servo oscillation. One other idea is that the high-speed spin check left the higher rotor at a place that masses servos 1 and a couple of in a singular, oscillation-inducing method that we haven’t encountered earlier than. We’ve plenty of instruments out there for working by means of the anomaly and we’re optimistic that we’ll get previous it and again to flying once more quickly.
Our workforce may have just a few weeks of time to finish our evaluation as a result of Mars might be in photo voltaic conjunction till mid-October, and we received’t be uplinking any command sequences to Ingenuity throughout that point. Conjunction is a particular interval by which Mars strikes behind the Solar (as seen from Earth), making communications with spacecraft on Mars unreliable. Ingenuity won’t be utterly idle throughout this time, nonetheless; Ingenuity and Perseverance might be configured to maintain one another firm by speaking roughly as soon as per week, with Ingenuity sending fundamental system well being info to its base station on Perseverance. We’ll obtain this information on Earth as soon as we come out of conjunction, and can find out how Ingenuity performs over an prolonged interval of relative inactivity on Mars. See you on the opposite facet of conjunction!
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